We know electric cars are getting better and likely to get popular even when driven by humans. Tesla, at its core, is a battery technology company as much as it’s a car company, and it is sometimes joked that the $85,000 Telsa with a $40,000 battery is like buying a battery with a car wrapped around it. (It’s also said that it’s a computer with a car wrapped around it, but that’s a better description of a robocar.)
Tesla did a lot of work on building cooling systems for standard cylinder Lithium-Ion cells and was able to make a high performance vehicle. The Model S also by default charges to only 80% of capacity because battery life is hurt by charging all the way to full. In fact, charging to 3.92 volts (about 60%) capacity is the sweet spot. Some of the other things that reduce battery life include:
Discharging too close to empty
Getting too warm while discharging
Getting too warm while charging, and in particular causing thermal expansion which creates physical damage
Even ordinary warmth, where the vehicle is stored for long periods, particularly at high charge, is dangerous. The closer to freezing the better, and even above 25 degrees centigrade causes some loss.
The important, but little reported statistic for a battery is the total watt-hours you will be able to get out of it during its usable lifetime. This tells you the lifetime of the battery in miles, and the cost tells you the cost per mile. How important is this? If the Tesla $40,000 battery lasts you 150,000 miles and sells for $10,000 when done, the straight-line cost per mile is 20 cents/mile — more than the cost of gasoline in most cars, and much more than the 3 cent/mile or less cost of electricity.
Humans will drive as humans want to drive, and it’s hard to change that. They will accelerate for both fun and to get ahead of other cars. They will take mixes of short trips and long trips. They don’t know how long their trips are and demand a flexible vehicle always ready for anything.
Electric robotaxis change that game. They will drive predictably, rarely ever demanding quick acceleration. A driver likes zippy fun, a passenger wants a gentle ride. They can go even further, and set their driving pattern based on the temperature of their batteries. Are we making the batteries too warm? Then “cool off,” literally. This applies both to fast starts and also slowing down. Regenerative braking conserves energy and increases range, but doing it too hard heats the batteries. Start slowing down sooner — especially if you have data on what traffic lights and traffic are doing and it can make a big difference.
Robotaxis can always use the sweet spot of the battery charge duty cycle.
You will rarely be sent a robotaxi that, in order to get you, needs to dig deep into its maximum range.
Often demand is predictable, so if need be, vehicles can be charged above 60% only when such demand is expected or is arising.
While robotaxis will prefer to charge at night when power is cheapest, they can charge any time to get back up to the optimal level
As I’ve noted before, battery swap doesn’t work well for humans, but robots don’t mind making an appointment or driving out of their way for a swap. This makes it easy to use batteries only in the sweet spot, and to charge them only at night on cheap power.
If battery swap is not an option, there are many options to supplement range during peak demand. Vehicles can go to depots to pick up trunk batteries, battery trailers, or even slot-in units with small motorcycle engines and liquid fuel tanks. If this is cheaper than the alternatives, it’s an option.
When it gets hot, robotaxis can seek out the shade, or even places with cooling, to keep the batteries from being too warm.
Robotaxis don’t mind the loss of range all that much
As a battery ages, its capacity drops. Humans hate that — having bought a car with a 100 mile range they won’t accept it can now only do 60. For a human, that means time to replace the battery. For a robotaxi, that just means you have a shorter range, and you don’t get sent on long range trips. Or you may decide that while before, you only charged to 60% to get maximum battery life, now you charge more, knowing it will eat the remaining life, but getting the most out of the battery.
Of course, as the range drops, now you run into another problem. You’re carrying around the extra weight of battery for half the range, and it’s costing you energy to do that, especially in an ultralight car where the battery is the biggest component of the weight. (This also enters into the math of whether it makes sense to charge only to 60%.) Eventually the time comes that the battery is not practical. This is the time to sell it. Tesla and others are working to produce a home and grid storage market for used car batteries. In those applications, the weight doesn’t matter, just the cost for the remaining lifetime watt-hours. You care about the capacity, but you pay a market price for it.
Eventually, even this is not practical and you scrap to recycle the materials.
Typical predictions for Lithium-Ion run from 500 to 1,000 cycles. Tesla’s techniques seem to be beating that. With robotaxis, who knows just how many lifetime kwh we’ll be able to get out of these batteries, or perhaps even other chemistries. Turns out that human drivers like a chemistry that keeps its life as long as possible then falls off a cliff. Slow decline is harder to sell — but slow decline chemistries, like Lithium Iron Phosphate and others could make more sense for the robots that don’t care.
It’s often suggested that electric cars could be used as grid storage. Problem is, with car batteries today, it costs around 15 cents to put a kwh into a battery and get it out. That means to be grid storage, you need to have the spot price on the grid be the price you bought at, plus 15 cents, plus a margin to make it worth this. Night power can get as low as 6 cents, so this does happen, but not as much as one might hope. The problem is that the grid’s peak demand is around 4 to 7pm, which is also a peak time for driving. That’s the last time most car owners will want to drain off their batteries to make a bit of money on the power. You will only do that if you know you won’t be using the car. For a robotaxi fleet, that might be the case. Of course, selling power to the grid you will do it only at a rate that does not harm your battery or warm it up too much.
When the grid gets to a super peak, the price can really spike to attractive numbers. That’s because building extra power plant capacity just for those rare days is expensive, and so almost any price is better. Here we could talk about cars as storage, when we know their batteries are not going to be used. That’s even more true of batteries sitting in a battery swap facility.
There has been lots of buzz over announcements from Tesla that they will sell a battery for home electricity storage manufactured in the “gigafactory” they are building to make electric car batteries. It is suggested that 1/3 of the capacity of the factory might go to grid storage batteries.
This is very interesting because, at present, battery grid storage is not generally economical. The problem is the cost of the batteries. While batteries can be as much as 90% efficient, they wear out the more you use and recharge them. Batteries vary a lot in how many cycles they will deliver, and this varies according to how you use the battery (ie. do you drain it all the way, or use only the middle of the range, etc.) If your battery will deliver 1,000 cycles using 60% of its range (from 20% to 80%) and costs $400/kwh, then you will get 600kwh over the lifetime of a kwh unit, or 66 cents per kwh (presuming no residual value.) That’s not an economical cost for energy anywhere, except perhaps off-grid. (You also lose a cent or two from losses in the system.) If you can get down to 9 cents/kwh, plus 1 cent for losses, you get parity with the typical grid. However, this is modified by some important caveats:
If you have a grid with very different prices during the day, you can charge your batteries at the night price and use them during the daytime peak. You might pay 7 cents at night and avoid 21 cent prices in the day, so a battery cost of 14 cents/kwh is break-even.
You get a backup power system for times when the grid is off. How valuable that is varies on who you are. For many it’s worth several hundred dollars. (But not too many as you can get a generator as backup and most people don’t.)
Because battery prices are dropping fast, a battery pack today will lose value quickly, even before it physically degrades. And yes, in spite of what you might imagine in terms of “who cares, as long as it’s working,” that matters.
The magic number that is not well understood about batteries is the lifetime watt-hours in the battery per dollar. Lots of analysis will tell you things about the instantaneous capacity in kwh, notably important numbers like energy density (in kwh/kg or kwh/litre) and cost (in dollars/kwh) but for grid storage, the energy density is almost entirely unimportant, the cost for single cycle capacity is much less important and the lifetime watt-hours is the one you want to know. For any battery there will be an “optimal” duty cycle which maximizes the lifetime wh. (For example, taking it down to 20% and then back up to 80% is a popular duty cycle.)
The lifetime watt hour number is:
Number of cycles before replacement * watt-hours in optimum cycle
The $/lifetime-wh is:
(Battery cost + interest on cost over lifetime - battery recycle value) / lifetime-wh
(You must also consider these numbers around the system, because in addition to a battery pack, you need chargers, inverters and grid-tie equipment, though they may last longer than a battery pack.)
I find it odd that this very important number is not widely discussed or published. One reason is that it’s not as important for electric cars and consumer electronic goods.
Electric car batteries
In electric cars, it’s difficult because you have to run the car to match the driver’s demands. Some days the driver only goes 10 miles and barely discharges before plugging in. Other days they want to run the car all the way down to almost empty. Because of this each battery will respond differently. Taxis, especially Robotaxis, can do their driving to match an optimum cycle, and this number is important for them.
A lot of factors affect your choice of electric car battery. For a car, you want everything, and in fact must just do trade-offs.
Cost per kwh of capacity — this is your range, and electric car buyers care a great deal about that
Low weight (high energy density) is essential, extra weight decreases performance and range
Modest size is important, you don’t want to fill your cargo space with batteries
Ability to use the full capacity from time to time without damaging the battery’s life much is important, or you don’t really have the range you paid for and you carry its weight for nothing.
High discharge is important for acceleration
Fast charge is important as DC fast-charging stations arise. It must be easy to make the cells take charge and not burst.
Ability to work in all temperatures is a must. Many batteries lose a lot of capacity in the cold.
Safety if hit by a truck is a factor, or even safety just sitting there.
Long lifetime, and lifetime-wh affect when you must replace the battery or junk the car
Weight is really important in the electric car because as you add weight, you reduce the efficiency and performance of the car. Double the battery and you don’t double the range because you added that weight, and you also make the car slower. After a while, it becomes much less useful to add range, and the heavier your battery is, the sooner that comes.
That’s why Tesla makes lithium ion battery based cars. These batteries are light, but more expensive than the heavier batteries. Today they cost around $500/kwh of capacity (all-in) but that cost is forecast to drop, perhaps to $200/kwh by 2020. That initial pack in the Tesla costs $40,000, but they will sell you a replacement for 8 years down the road for just $12,000 because, in part, they plan to pay a lot less in 8 years. read more »
In the last few months, I have found myself asked many times about a concept for solar roadways. Folks from Idaho proposing them have gotten a lot of attention with FHWA funding, a successful crowdfunding and even an appearance at Solve for X. Their plan is hexagonal modules with strong glass, with panels and electronics underneath, LED lights, heating elements for snow country and a buried conduit for power cables, data and water runoff. In addition, they hope for inductive charging plates for electric vehicles.
This idea has come up before, but since these folks built a small prototype, they generated tremendous attention. But they haven’t spoken at all about the cost, and that concerns me, because with all energy projects, the financial math is 99% of the issue. That’s true of infrastructure projects as well.
There are two concepts here. The first is, can you make a cost effective manufactured road panel? Roads are quite expensive today, but they are just asphalt gravel and other industrial materials whose cost is measured the range of $50 to $100 per ton. A chart from Florida suggests that basic rural asphalt roads cost about $9 per square foot, all-in, including labour and grading (it’s flat there) and about $4/square foot for milling and resurfacing. Roadway modules could be factory made (by robots) but still would require more labour to install, but I still think it is a very tall order for a manufactured surface to not cost a great deal more, even an order of magnitude more than plain road. Paved roads need maintenance, and that’s expensive. It is proposed that these panels would be cheaper to maintain as you just swap them out, but I am again skeptical of this math. Indeed, one of the major barriers to proposals for electric roads (which can charge cars) is that putting anything in the road makes it prohibitively more expensive to maintain.
I won’t say this is impossible — but it’s all about the math. We need to see math that would show that the modular manufactured pavement approach can compete. I’m happy for that math to include future technologies, like robot assembly and placement (though realize that we’ll probably see road construction with simpler materials also done by robots even sooner.) Let’s see the numbers, how cheap can it get?
All of this is without the solar panels inside (or the electronics.) Because the solar panels have their own math. The only synergy is this: If the modular roadway can be made so that it costs only a bit more than other approaches, it offers us “free land” to put the panels, and it’s connected land in long strips to run power wires.
How valuable is free land? Well, cropland in the USA costs an average of about 10 cents per square foot. 23 cents in California. 3 cents/square foot in the rural west. Much more, of course, in urban places. The land is not that important, so the other value comes from having a nice, manufactured place in which to put solar panels.
Today solar panels are still costly. They are just getting down (primarily thanks to cheap Chinese money) to our grid price. Trends suggest they will get lower and become cost effective as a variable source of power. But until they get really, really cheap, you want to use them most efficiently.
To use solar panels at their best, you don’t want to lie them flat (except in the tropics) but rather you want to tilt them just just a bit below the angle of your latitude. Conventional wisdom also points them south, though it’s actually better for the grid and most people’s power demands if you point them south-west, losing a few percent of their output but getting more of it to match peak demand. Putting them flat costs you 20 to 30% of their output. (You can also have them motorized and gain even more, but it’s usually not cost-effective, and will become less cost-effective as panels get cheaper and motors don’t.)
To use solar panels at their best, you also want to put them where it’s very sunny. Finally you want to first put them where the local power comes from coal. When you have gotten rid of most of the coal, you can start putting them elsewhere. You can put panels in less sunny places which have power from hydro, nuclear or natural gas, but you’re really wasting your money. The ideal places are Arizona and New Mexico, with tons of sun and lots of coal. And lots of cheap, fairly low-value land.
To be fair, the biggest cost of the panels will soon be the hardware they are mounted in, along with the wires and electronics to connect them, and so perhaps these road modules could compete by being cheap hardware for that. But it seems not too likely.
In cities, rooftops provide another source of free land, much of it slanted about right and pointed in roughly the right direction. With lower cost than tearing up roads. But to be fair, right now one of the bigger cost elements is getting permits to do the construction and electrical work. Roads are far from bureaucracy-free, but at least it scales — you get permits for a big project all at once, not one house at a time. But we can solve that problem for houses if we really want to as well.
So my challenge to the solar roadway team is to show us the math. No, we don’t need to see what it cost to make your prototypes. I am sure they are very expensive, but that’s beside the point. I want to see a plan for how low the cost can go in theory, even assuming future technologies. And compare that to how low the cost for the alternatives can go in theory. And then factor in how things don’t get to that theoretical point due to bureaucracy, unions and other practicalities. Compare panels in the road to panels by the side of the road, tilted and not being driven over. Look at what paved roads cost in practice to what they could cost in theory to get an idea of how close you can actually get, or come up with a really convincing reason why one approach is immune from the problems of another.
And if that math says yes, go at it. But if it doesn’t, focus on where the math tells you to go.
The reason this is attractive is that a large part of the cost of the grid is building it to handle the peak load. Most of the capital cost is for that, and fuel costs are based on the real, variable load. Softening the peak is very valuable to the power company — to the point that power companies give rebates and credits to people who do things that will soften that peak.
This is also one of the virtues of solar. It tends to provide power during the day, which is always when the peak is. However, solar peaks at noon, while the demand peak is the hottest part of the day, which tends to be later in the afternoon. The big peak tends to be around 4-6pm when it’s hot, and people have started turning on things in their houses to get ready for dinner. On the spot markets power costs the most then.
Contrast that with the night. Because nuclear plants and some big coal plants aren’t easy to dial back, then sometimes even produce more power than is being used, and they end up discarding the power into giant resistors. That makes power at night cheap.
I’ve never seen it done, but there could even be merit in the idea of mounting fixed solar panels pointing west, so that they catch less power in the morning but do better in the later afternoon when the price of electricity is highest. I presume this doesn’t happen because net metering home owners don’t get access to the “true” spot power price which would justify this. If they are lucky they do get time-of-day metering so they sell power at a high price in the day and buy it cheap in the evening, but some don’t even get that. The harsh reality is that most grids were not built to have a lot of generation at the edges, and power companies are pushing back on net metering and grid-ties that feed back too much power. Indeed, for cost reasons here in California, people should size their solar systems to not quite meet needs, and buy the rest at the cheap “tier 1” price, rather than try to sell back.
Most solar panels are erected facing due south, tilted to the latitude which maximizes total kwh, but peaks at noon. Actually, most are mounted on a section of the roof that is closest to south. If you have to choose between SE and SW, it might be that SW is best, at least for the grid.
(Sadly, a number of solar panels are mounted on the front of houses, even if that points north! People are more keen on looking good than doing good. I hope that’s rarer than I’ve been told.)
Anyway, back to the cars
There are a few issues with using the batteries in the car for the peak load.
The peak time is unfortunately a very popular time for driving. People either want to drive in the late afternoon — it is called the rush hour for a reason — or they plan to drive soon and want their car’s battery to be full to meet their driving needs. They don’t want to find their car half-empty at 6pm because it sold power to the grid. A study of car usage patterns detailed the numbers.
The batteries in cars are expensive. Charging and discharging the battery uses up its lifetime. We don’t know how long car batteries are going to last but a typical estimate is around 150,000 miles, or about 40,000 lifetime kwh. If it’s the 22kwh pack in the LEAF (which costs $12K or so today) that’s 27 cents/kwh lifetime. Plus the cost of the electricity that went in to be resold. The peak price ranges from 25-30 cents/kwh in the west but hits as much as 48 cents in New York. So it could be profitable in New York, but barely so. Big, heavy lead batteries are more cost effective.
There are some factors, though, which could change this:
Battery packs will get cheaper, and their lifetimes will increase. That will drop the cost of putting a kwh into and out of a battery.
Cars like the Tesla model S have huge batteries, far more than they actually need. This, it turns out is quite wasteful, since you buy a lot of battery and rarely use it. If you know you don’t plan a 200 mile trip, you might be tolerant that your long-range car is half-empty at 6pm, and happy to sell that excess capacity. You already paid for the capacity, after all to give you that long-trip freedom. You will still shorten the battery life, but you’ll be paid for that.
Weather forecasts are getting quite accurate, so demand can be predicted and this managed better.
The car can also be a backup in the event of grid power outages. There, the 35 cent/kwh price (and loss of driving ability) are minor compared to the burden of having no power in your home.
Calling all cars!
Now, as you might expect on this blog, robocars are also game changers here. The inverters and equipment to feed power back to the grid are expensive, so most people won’t have them. But if the robocars have a means to plug in, they can bring the power to where it’s needed. A power company, seeing a brownout coming, could send out an alert on the net. “Calling all cars” — if you have spare capacity, we’ll buy it at the following rate. Please drive to the nearest two-way intertie and plug in soon. While ideally some sort of automatic connection would be possible, this could even be a charging lot with human staff who plug in the cars as they arrive and unplug them when they have to leave.
Such charging lots might well exist for cars that need charges at night or other non-peak times. Due to cost, cars will strongly wish to avoid charging at peak cost times. This puts them to use then. Inductive charging also works (at a loss of about 10%) and robotic plug-in is actually quite doable — there are already robotic gasoline filling stations out there. A robocar charging lot could be dense-pack, valet style, so not take a lot of land. But it would take megawatts — but that’s OK. The robots don’t care how convenient it is, so put it next to the transformer station.
One of the silly ideas I see often is the solar powered car. In 2011, I wrote an article about the solar powered robocar which explained some of the reasons why the idea is anti-green, and how robocars might help.
In the Ford proposal, there is a special garage with sun exposure and a giant Fresnel lens, which can focus light on a solar panel on the car parked in the garage, effectively a solar concentrator based PV system. The trick is that the car is able to move during the day, so as the sun moves (or rather the Earth and the garage turn with respect to the sun) the car adjusts to put the panel in the beam of the Fresnel lens. They predict they could get 21 miles of range in six hours of sunlight. That’s a bit over 5kwh, meaning the panel must generate just under a kw during those 6 hours.
Normally 1kw of solar panel is quite large, and the roof of the garage is large to make this happen. The downside is this would make the panels really, really hot, which reduces their efficiency and frankly, could be dangerously hot and also wear out the panels and roof quickly. (We would need to see what temperature parameters they plan for.)
In the end, this system still falls into the pitfalls that make a green solar powered car a contradiction in terms. To be green, you must use all the power panels generate. When this car is not in the garage, its panel will produce minimal output, since as it moves about its day it will park in shade or at the wrong angle to the sun, and the panels will be horizontal. The only way to properly exploit panels is to have them at the very least facing south in a permanently sunny spot, tilted to the latitude (or sun-tracking) and combined with the grid, so every single joule they generate is put to use.
There is a minor win for solar on a vehicle, which is when you are driving, the energy is never stored, and thus battery weight can be slightly lowered and there are no storage or transmission losses. However, unless you are going to make something like the cars that compete in the solar races, this doesn’t make up for the waste of having panels whose output is mostly unused. Toyota figured out a good use for a panel on the Prius — it runs the ventilation fan, whose demand matches the sunlight and heat of the day. Every joule of that panel is used, and keeping the car cool saves on AC when driving. Had the panel fed into the hybrid battery, its output would be thrown away most of the time when the battery was not low.
As I noted in my earlier article, robocars could make better use of solar panels because they could arrange to always store themselves in the sun, pointed in the right direction, and could even go find connection stations to feed their power back to the grid if the batteries were not low. (You need some robotic ability to connect to the charging station without a human, and ideally without the 10% loss of inductive coupling but even that is tolerable.)
In that world, you could put up Fresnel or other concentrating charging stations which cars could seek out to make the best use of their panels. However, these cars are now consigned to never being garaged or parking in the shade, which is not really what we’re looking for.
This does have the advantage of not needing to plug in, though inductive charging stations are also something robocars would move themselves to. If the vehicles are used off-grid, this would be somewhat more valuable even if on-grid the panels (concentrated or not) should just feed that grid.
There’s another downside to the heat of this system. In the summer at least, you then have to spend a fair bit of energy cooling the car down. The extra energy gained from sitting in the sun might be lost in cooling if the wait was modest. A cooling fan is a good idea while in the sun.
In other News
Michigan has passed its law regulating the testing of robocars there. It’s being touted as a way to “save jobs” by preventing the flight of automaking innovation to other locations. It’s going to be a tall order. The Detroit car companies are opening labs in silicon valley, in part because it’s very difficult to recruit the very best people to come live in Detroit, no matter how cheap the housing is — and you can have a mansion in Detroit for the price of a shack in San Francisco. If Michigan wants to retain its car dominance, it will need to do even more.
Several announcements planned for CES. Delphi will be showing off their latest work, which is more ADAS related. Bosch will be showing off their prototype cars, and presumably Audi and others will return.
Results from the Ann Arbor V2V test bed are expected soon. The original plan was for the DoT to propose regulations demanding V2V in all new cars in 2013. They missed that deadline, of course, but many expect something very soon. Results of this testbed are expected to be crucial. I predict the results will be lukewarm when viewed through the robocar lens — which is to say, the V2V systems will only have been found able to prevent a tiny number of incidents which could not also be detected with advanced sensors directly on the cars. They may not publish that number, as there are incentives to make the test report as a success.
One of the biggest issues with wind and solar is that they are intermittent, and so either need storage or grid-tie to work. There really is no good storage, and generally storage-based systems are highly wasteful, throwing away most of the power you generate because you want to keep the storage near full. Grid-tie is the only green choice, but it’s expensive and requires expensive inverters and permits and more.
One solution to this to find work for your renewable energy source to do that fits well with its intermittent nature. Something that will take all the power you generate, but not mind if it comes and goes. Such loads are hard to find. One potential example is pumping water to filter a swimming pool. Its recommended to flow twice the volume of your pool every day in summer, which means around 10kwh of electricity with typical systems. Most people filter their pool using the same pump they use for vacuuming and pool maintenance, which is actually way more powerful than you need for filtering. They offer variable speed pumps, which use a low-power efficient speed for filtering and a high-power speed for vacuum and manual operations, and claim they save a lot.
For those who have a pool, the pump is using as much electricity as all their other appliances in some cases, and so it’s a win to make that greener. Unlike those appliances, the pool water can be filtered any time, as electricity is available, though you can’t let the pool go unfiltered for days, so it’s not perfect. For people who have time-of-use metering, they are wise if they only filter at night, and many do that.
The trick to perfect use of solar for pool pumping would be a smart, multi-speed pump able to run on both the DC from solar panels and the grid power. It would need to do the following:
When there is power from the solar panel, run as fast as you can on that power, filtering.
When you need high flow, switch to (or combine with) grid power for full power.
Track the amount of water filtered, as well as temperature, and when the sun did not provide enough power, run the pump at night off grid power to make up the difference.
For extra credit, have a sensor that detects how clear the water is, and adjust grid usage based on that, rather than just weather.
This system would make use of all the power from the panels. As a plus, you need more filtering in summer than you do in winter, which matches what panels do. However, you must not oversize your panels. They can’t be bigger than you need to do all your winter filtering on a series of sunny winter’s days, or you will be wasting their power then.
Key to this plan is that it’s easy to install. Put in the new pump and wire it up to panels. No inverters or electricians and perhaps not even any permits. It doesn’t feed power back to the grid or the house. This is key because panels are now getting very cheap (less than a dollar per watt) and as such installs and permits and other gear are more expensive than the panels.
There are some pool pumps with brushless DC motors sold for solar use. They are expensive and don’t do the smart tricks above, in particular using the grid to take up the slack. They depend instead on overprovisioned solar, or solar systems powering more than a
For $700 you can also buy a floating solar pool filter. This is a nice trick because it’s self-contained, though it’s a rather large thing to float in your pool. It can’t handle the whole filtering load —in fact it only handles about 25% of the load of a typical pool and uses cartridge filters. As such, you still run the regular pump and filter on some schedule, you just run it a bit less.
I noted above that you can get variable speed pumps, and that these, it is claimed, us as little as 1/5th the energy of the full speed pumps for filtering. They cost 2-3x as much as basic one speed pumps, and as a result are not very common. This bodes poorly for the solar proposal here, because if customers aren’t willing to do the up-front investment to save energy for these pumps, few would do the added task of putting up a solar panel and plugging it into such a pump. Comparatively few, that is — solar nerds would love to do it.
As always, the best place to deploy panels to do this would be the sunny, coal-oriented regions like Arizona and New Mexico, where it turns out pools are pretty popular. Once again, the math says that if your goal is to use your money and time to make the world greener, it would be far better to get people in those places to install a system like this on their pools than for you to put panels on your house in California for anything. Putting panels up in California is something you do to feel good.
Another interesting alternative is wind. Pumping water with wind is perhaps the oldest wind technology out there. In this case, you might even be able to be like an old windmill, and be mechanical, by having the turbine drive a flexible shaft down to the ground to run the pump. Presumably some clever transmission would be needed to maintain filter pressure properly at all windspeeds. You could also do traditional electrical generation from the wind and power a pump like the one above.
Wind has its positives and negatives. Unlike solar, it does not have the natural higher capacity in the summer. It can be much more intermittent. Solar panels still do around 30% to 50% of their rated power on ordinary cloudy days (though this is quite variable based on the panels and local weather patterns) so there is pumping every day. Wind in most places comes and goes. At my house, the winds are high today but it would not generally be suitable as we go weeks without much wind. Wind also prefers a tower near the pool, which has many issues.
I recently read a complaint by an EV driver that the charging station at De Anza College cost 55 cents/kwh. The national average price for electricity is around 10 cents, and at that price a typical electric car costs under 3 cents/mile for electricity. Gasoline costs about 8 cents/mile in a Prius, about 13 cents in a decent non-hybrid and 18 cents/mile in the average car which gets 22mpg. (At least here in California.) But the college’s charger’s electricity is almost 15 cents/mile in most electric sedans today, which is more than the gasoline in any gasoline car an eco-conscious person is likely to buy. (California Tier III electricity is 30 cents/kwh and thus almost as much.)
The price of charging stations varies wildly. A lot of them are free still, financed by other motivations. Tesla’s superchargers are free — effectively part of the cost of the car. It’s not uncommon for parking lots to offer free charging if you pay for parking, since parking tends to cost a fair bit more. After all, you won’t put more than 20kwh in a Leaf (and probably a lot less) and that costs just $2 at the average grid price.
This got me thinking of how the economics of charging will work in the future when electric cars and charging stations are modestly plentiful. While the national grid average is 10 cents, in many places heavy users can pay a lot more, though there are currently special deals to promote electric cars. Often the daytime cost for commercial customers is quite a bit higher, while the night is much lower. Charging stations at offices and shops will do mostly day charging; ones in homes and hotels will do night charging.
Unlike gasoline pumping, which takes 5 minutes, charging also involves parking. This is not just because charging takes several hours, but because that is enough time that customers won’t want to come and move their car once full, and so they will take the space for their full parking duration, which may be 8 or more hours.
Charging stations are all very different in utility. While every gasoline station near your route is pretty much equivalent to you, your charging station is your parking spot, and as such only the ones very close to your destination are suitable. While a cheap gas station 2 miles off your route would have a line around the block, a free charging stations 2 miles away from your destination is not that attractive! More to the point, the charging point close to your destination is able to command a serious premium. That have a sort of monopoly (until charging stations become super common) on charging at the only location of value to you.
Put another way, when buying gasoline, I can choose from all the stations in town. When picking an EV charge, I can only choose from stations with an available spot a short walk from my destination. Such a monopoly will lead to high prices in a market where the stations are charging (in dollars :-) what the market will bear.
The market will bear a lot. While the electricity may be available cheap, EV owners might be easily talked into paying as much for electricity as gasoline buyers do, on a per-mile basis. The EV owners will be forgetting the economics of the electric car — you pay the vast bulk of your costs up front for the battery, and the electrical costs are intended to be minor. If the electricity cost rivals that of gasoline, the battery cost is now completely extra.
Naturally, EV owners will do at least half their charging at home, where they negotiate the best rate. But this could be worse, as they might well be talked into looking at the average. They could pay 80 cents/kwh in the parking lot and 10 cents/kwh at home, and figure they are getting away with 45 cents and “still beating gasoline.” They would be fooling themselves, but the more people willing to fool themselves, the higher prices will go.
There is another lack of choice here. For many EV drivers, charging is not optional. Unless they have easy range to get back home or to another charging place they will spend lots of time, you must charge if you are low and the time opportunity presents itself. To not do so is either impossible (you won’t get home) or very foolish (you constrain what your EV can do.) When you face a situation where you must charge, and you must charge in a particular place, the potential for price gouging becomes serious. read more »
But I do believe in the idea of the self-driving electric taxi as the best answer for our future urban transportation. So how do you make it happen?
There’s a big problem with this vision. Electric cars today have perhaps 100 to 150 miles of range, which means 3 to 6 hours of operation, depending on the speeds you go. You can make more range (like a Telsa S) but only by adding a lot of weight and cost. But an effective taxi is on shift all day, or at least all the waking hours, and could easily operate 8 to 10 hours per day. While any taxi will have downtime during the day (particularly at off-peak hours) the recharge of the battery takes so long it’s hard to do during the day. Ideally you want to charge at night, when power is cheap. So let’s consider the options.
Large battery pack
You could make a vehicle with enough battery for a full day’s work, and charge it at night. This is very expensive today, and also takes a lot of room and weight in the vehicle, reducing its efficiency. You also need taxis at night so either way you have to have some taxis that work at night and recharge in the day, but not as many.
While battery swap did not pan out for Better Place, it actually makes much more sense for a robotic taxi fleet. You just need a few swap stations in the city. It doesn’t bother the robots if they take a while for a swap (mainly it bothers you because you need more stations.) And while humans would get very angry if they came to the swap station and saw they were 4th in line at 5 minutes/swap, robots would just schedule their swaps and get in and get out.
That’s all good, and it solves a few other problems. Taxis will be putting on lots of miles every day, and they will probably wear out their battery quickly. If the rest of the vehicle has not worn out, swap becomes ideal — replace the vehicle’s components when you need to, including the most expensive part, the battery. It also makes it easier to charge all batteries only at night, on cheap baseload power.
Swap also allows the batteries to be only used in the “easy” part of their duty cycle (from 80% to 20%) without much hassle. You only get 60% of the range, but you don’t care a lot, other than in having to
buy more battery packs. You just do the math on what’s cheaper.
A working supercharger that can recharge a vehicle in an hour solves the problem as well. Robotic taxis can always find a spare hour without much loss of efficiency. (Indeed with none as they will age by active mile or hour.) The big problem is that supercharging generally is felt to stress the batteries and reduce the lifetime of the packs. Certainly running a car on full cycle every day and supercharging it is not going to produce a happy battery.
A robocar supercharging station could do a few extra things, though. For example, you could hook the car up to a special cooling system to pump externally chilled coolant through the batteries, as heat is the big killer in the supercharge. You might even find a way to put some pressure in to keep the cases from expanding that much, as this is a big stressor when charging.
Supercharging probably has to be done in the day, with more expensive power. One charge for the morning peak and another for the evening. Some speculate it’s worth using your inventory of old battery packs to store power during the night to release in the day. Solar can also help during the day — on sunny days, at least.
While automated connection is good, you really would not have many supercharging centers, due to their high power needs, so they could have human staff to do the work.
Both the supercharging and battery swap stations do not need to be located all that conveniently for humans. Instead, you can put them near power substations where megawatts can be purchased.
More vehicles and ordinary L2 charging
If the batteries are more expensive than the vehicles, then perhaps just having more vehicles to house all your battery packs is the answer. Then you have vehicles spending their time idle, and charging at ordinary level 2 (6kw) rates. Full level 2 can add about 20 miles of range to a car like a Leaf in an hour. Depending on the usage patterns that might not be too bad. Of course it’s daytime power again, which is expensive. Urban taxis won’t go more than about 25mph on average if they are lucky, often less, particularly at rush hour. Suburban will go a bit faster. You need stations that allow a robot to recharge, which could mean inductive, or human-staffed, or eventual robotic plug-in systems. Don’t laugh at the idea of human-staffed. The robot will not be in a super rush, so stations near retail shops or existing gas stations would work fine as long as somebody can come out and tend to the robot on connect and disconnect within 5 minutes.
It may seem like more vehicles is more expensive, but that’s not necessarily true. It depends on how and why the vehicles wear out. Ideally you design the vehicle so battery and most major vehicle components all reach end-of-life at a similar time or that they can be replaced easily. That may mean a battery that can be swapped — but in the shop, not at an automatic swap station.
Plug in hybrids?
Plug in hybrids of course solve the problem, and they can charge when they can to be mostly electric and only use that gas engine more rarely. This actually creates a downside — it’s expensive to have a fossil fuel power train around to barely use it. And it adds a fair bit to the maintenance cost. This does allow for highway travel. Otherwise, you send a liquid fuel car to anybody wanting to do a long highway trip - save the electrics for the urban travel.
Very light vehicles
Today’s electrics use about 250 to 300 watt-hours/mile. OK, but not great. Efficient designs can go below 100 watt/hours per mile. That means doing 300 miles, which is enough for a full day in a city cab, needs only 30kwh (probably a 45kwh battery.) That’s a $22K battery today, but it will be a $9K battery by the end of this decade according to predictions. This might be quite reasonable.
Last year, I met Oliver Kuttner, who led the team to win the Progressive X-Prize to build the most efficient and practical car over 100mpg. Oliver’s Edison2 team won with the VLC (Very Light Car) and surprised everybody by doing it with a liquid fuel engine. There was a huge expectation that an electric car would win the prize, and in fact the rules had been laid out to almost assure it, granting electric cars an advantage over gasoline that I thought was not appropriate.
The Edison2 team made their focus on weight, though they far from ignored drag. Everybody made an aerodynamic car, but what they realized was that making the car light was key. And batteries are heavy, heavier than efficient liquid fuel engines. Hybrid systems, with both batteries and two motors are even heavier than what they built. They also developed a new type of suspension which was much lighter and allowed a simpler car.
Since the X prize, they have built electric cars as well — their techniques still work there, even if that’s not where they found the greatest X-prize results — and recently showed of their latest 1,400lb model which seats 4. (Though I can’t say I think it’s comfortable with 4.) Equally impressive, Oliver reports they have done succesful forward offset collision tests, and done well at them, contradicting a popular impression that small, light cars must be death traps on the road.
This bodes well for robocars. As I wrote 2 weeks ago, I think the small, light car is the future of transportation if we want it to be efficient, and the robocar can, by delivering such vehicles for people making shorter solo or 2 person trips — ie. the vast majority of all trips — make this happen.
Earlier, I brought Oliver in to give a talk at Google in the Greeen@Google series. Here is a video where I host him describing the car and their thinking around it. His thinking on cars is fresh and while it’s very challenging to start a new car company, here’s somebody who might just do it.
We’ve often said that in the most distant future, when car accidents are very rare, we will be able to make our cars lighter because over 30% of the weight of a modern vehicle goes into safety features. I think we can get those light vehicles even sooner.
You’ve probably seen the battle going on between Elon Musk of Tesla and the New York Times over the strongly negative review the NYT made of a long road trip in a Model S. The reviewer ran out of charge and had a very rough trip with lots of range anxiety. The data logs published by Tesla show he made a number of mistakes, didn’t follow some instructions on speed and heat and could have pulled off the road trip if he had done it right.
Both sides are right, though. Tesla has made it possible to do the road trip in the Model S, but they haven’t made it easy. It’s possible to screw it up, and instructions to go slow and keep the heater low are not ones people want to take. 40 minute supercharges are still pretty long, they are not good for the battery and it’s hard to believe that they scale since they take so long. While Better Place’s battery swap provides a tolerable 5 minute swap, it also presents scaling issues —
you don’t want to show up at a station that does 5 minute swaps and be 6th in line.
The Tesla Model S is an amazing car, hugely fun to drive and zippy, cool on the inside and high tech. Driving around a large metro area can be done without range anxiety, which is great. I would love to have one — I just love $85K more. But a long road trip, particularly on a cold day? There are better choices. (And in the Robocar world when you can get cars delivered, you will get the right car for your trip delivered.)
Electric cars have a number of worthwhile advantages, and as battery technologies improve they will come into their own. But let’s consider the economics of a long range electric. The Tesla Model S comes in 3 levels, and there is a $20,000 difference between the 40khw 160 mile version and the 85kwh 300 mile version. It’s a $35K difference if you want the performance package.
The unspoken secret of electric cars is that while you can get the electricity for the model S for just 3 cents/mile at national grid average prices (compared to 12 cents/mile for gasoline in a 30mpg car and 7 cents/mile in a 50mpg hybrid) this is not the full story. You also pay, as you can see, a lot for the battery. There are conflicting reports on how long a battery pack will last you (and that in turn varies on how you use and abuse it.) If we take the battery lifetime at 150,000 miles — which is more than most give it — you can see that the extra 45kwh add-on in the Tesla for $20K is costing about 13 cents/mile. The whole battery pack in the 85kwh Telsa, at $42K estimated, is costing a whopping 28 cents/mile for depreciation.
Here’s a yikes. At a 5% interest rate, you’re paying $2,100 a year in interest on the $42,000 Tesla S 85kwh battery pack. If you go the national average 12,000 miles/year that’s 17.5 cents/mile just for interest on the battery. Not counting vehicle or battery life. Add interest, depreciation and electricity and it’s just under 40 cents/mile — similar to a 10mpg Hummer H2. (I bet most Tesla Model S owners do more than that average 12K miles/year, which improves this.)
In other words, the cost of the battery dwarfs the cost of the electricity, and sadly it also dwarfs the cost of gasoline in most cars. With an electric car, you are effectively paying most of your fuel costs up front. You may also be adding home charging station costs. This helps us learn how much cheaper we must make the battery.
It’s a bit easier in the Nissan LEAF, whose 24kwh battery pack is estimated to cost about $15,000. Here if it lasts 150K miles we have 10 cents/mile plus the electricity, for a total cost of 13 cents/mile which competes with gasoline cars, though adding interest it’s 19 cents/mile — which does not compete. As a plus, the electric car is simpler and should need less maintenance. (Of course with as much as $10,000 in tax credits, that battery pack can be a reasonable purchase, at taxpayer expense.) A typical gasoline car spends about 5 cents/mile on non-tire maintenance.
This math changes a lot with the actual battery life, and many people are estimating that battery lives will be worse than 150K miles and others are estimating more. The larger your battery pack and the less often you fully use it, the longer it lasts. The average car doesn’t last a lot more than 150k miles, at least outside of California.
The problem with range anxiety becomes more clear. The 85kwh Tesla lets you do your daily driving around your city with no range anxiety. That’s great. But to get that you buy a huge battery pack. But you only use that extra range rarely, though you spend a lot to get it. Most trips can actually be handled by the 70 mile range Leaf, though with some anxiety. You only need all that extra battery for those occasional longer trips. You spend a lot of extra money just to use the range from time to time. read more »
One of my first rules of robocars is “you don’t change the infrastructure.” Changing infrastructure is very hard, very expensive, requires buy-in from all sorts of parties who are slow to make decisions, and even if you do change it, you then have a functionality that only works in the places you have managed to change it. New infrastructure takes many decades — even centuries, to become truly ubiquitous.
That’s why robocar enthusiasts have been skeptical of things like ITS plans for roadside to vehicle and vehicle to vehicle communications, plans for dedicated highway lanes with special markers, and for PRT which needs newly built guideways. You have to work with what you have.
There are some ways to bend this rule. Some infrastructure changes are not too hard — they might just require something as simple and cheap as repainting. Some new infrastructures might be optional — they make things better in the places you put them, but they are not necessary to operations. Some might focus on specific problem areas — like special infrastructure in heavy pedestrian areas or parking lots, enabling or improving optional forms of operation in those areas.
Another possiblility is to have robocars enable a form of new infrastucture, turning it upside down. The infrastructure might need the robocars rather than the other way around. I wrote about that sort of plan when discussing a solar panel on a robocar.
A recent proposal from Siemens calls for having overhead electric wires for trucks. Trolley buses and trams use overhead electric wires, and there are hybrid trolley buses (like the Boston T line) which can run either on the wires or on an internal diesel. These trucks are of that type. The main plan for this is to put overhead wires in things like shipping ports, where trucks are running around all the time, and they would benefit greatly from this.
I’ve seen many proposals for electrication of the roads. Overhead wires are problematic because they need to be high enough to go over the trucks and other high vehicles, but that makes them harder to reach by low vehicles. You need two wires and must get good contact. They are also damn ugly. This has lead to proposals for inductive power supplies buried in the road. This is very expensive as it requires tearing up the road. There are also inductive losses, and while you don’t need to make contact, precise driving is important for efficiency. In these schemes, battery-electric cars would be able to avoid using their batteries (and in fact charge them) while on the highway, vastly increasing their range and utility.
Robocars offer highly precise driving. This would make it easier to line up on overhead wires or inductive coils in the road. It even would make it possible to connect with rails in the roadbed, though right now people don’t want to consider having a high voltage rail on the ground, even on a highway.
It was proposed to me (I’m trying to remember by who — my apologies) that one new option would be a rail on the side of the highway. This lane would be right up against the guardrail, and normally would be the shoulder. In the guardrail would be power rails, and a connector would come from the left side of the vehicle. Only a robot would be able to drive so precisely as to do this safely. Even with a long pole and more distance I am not sure people would enjoy trying to drive like this. A grounding rail in the roadbed might also be an option — though again tearing up the roadbed is very expensive to do and maintain.
There is still the problem of having a live rail or wire at reachable height. The system might be built with an enclosed master cable and then segments of live wire which are only live when a vehicle is passing by them. Obviously a person doesn’t want to be there when a car is zooming through. This requires roboust switching eqiupment for the thousands of watts one wishes to transfer. You also have to face the potential that a car from the regular lanes could crash into the rail and wires, and while that’s never going to be safe you don’t want to make it worse. You also need switching if you are going to have accounting, so only those who pay for it get power. (Alternately it could be sold by a subscription so you don’t account for the usage and you identify cars that don’t have a subscriber tag who are sucking juice and fine them.)
There is also the problem that this removes the shoulder which provides safety to other cars and provides a breakdown lane. If a vehicle does have to stop in this lane for emergency reasons, sensors in the rail could make sure that all robocars would know and leave the lane with plenty of margin. They would all have batteries or engines and be able to operate off the power — indeed the power lines need not be continuous, you don’t have to build them in sections of the road where it’s difficult. If other cars are allowed to enter the lane, it must not be dangerous other than physically for them to brush the wires.
It’s also possible that the rail could be inductive. The robocar could drive and keep its inductor contact just a short distance from the coils in the rail. This is more expensive than direct contact, and not as efficient, but it’s a lot cheaper than burying inductors in the roadbed. It’s safe for pedestrians and most impacts, and while a hard impact could expose conductors, a ground fault circuit could interrupt the power. Indeed, because all vehicles on the line will have alternate power, interruption in the event of any current not returning along the return is a reasonable strategy.
For commuters with electric cars, there is a big win. You can get by with far less battery and still go electric. The battery costs a lot of money — more than enough to justify the cost of installing the connection equipment. And having less battery means less weight, and that’s the big win for everybody, as you make the vehicles more efficient when you cut out that weight. Of course, if this lane is only for use by electrified robocars, it becomes a big incentive to get one just to use the special lane.
The power requirements are not small. Cars will want 20kw to go at highway speed, and trucks a lot more. This makes it hard to offer charging as well as operating current, but smaller cars might be able to get a decent charge while driving.
Update: When I first wrote this, I was under the mistaken belief that Better Place only swapped one type of battery module. At present they only support one, but their swap stations are designed to support up to six kinds, as long as they can be loaded and unloaded from below.
Recently, electric car battery-swap company Better Place announced delivery of their first cars in Israel. Israel is a country of small size where it makes sense to deploy a technology like this with a chicken and egg problem. They hope to have enough battery swap stations that people feel they can drive an electric car and refuel it as quickly and conveniently as a gasoline buggy.
I remain skeptical about battery swap for electric cars, but think robocars solve many of those problems. Here’s why:
To have a workable battery swap system, you need to standardize the battery module, ideally having just one or two form factors and electrical characteristics. Just one to start, in fact. This has many downsides:
A large part of the innovation in electric cars today is in the batteries. A big part of what Tesla did was their new cooling system. Designers all want to be able to play with chemistries, voltage, controllers and more. They might give up playing with size and placement but not those things.
It’s still an issue to not be able to vary size and shape of the battery, at least for people wanting to build cars of unusual shape.
A large part of the cost of an electric car today is the battery. With the swap system, you can’t buy the battery with the car. You get whatever battery you are swapped. That’s good in some ways, but eliminates open market competition on these systems because there is only one buyer — the swap company.
Swap machines are expensive, take land and still take five minutes, arrival to departure. That’s almost as quick as filling up with gas, but a typical gas station has 8 pumps, and some have many more. If there are several cars in line at a single swap station, you’re in for a serious wait.
On the plus side, people actually need swaps more rarely than they imagine. A 70-100 mile range car will hardly ever feel the need for a swap — in many ways the availability of the swap makes you feel more comfortable about the car, even if you rarely use it. It’s better than the level 3 charge which can damage the battery and still takes 15-20 minutes.
I think robocars (cars able to move while empty to the swap station) solve many of these problems. They solve them because while robocars (particularly those operating as taxis) need to run all day and thus want to swap batteries, the cars can move to the swap station on their own, when they are not serving somebody.
There is much less need to standardize, though it does help. Your car simply goes to a swap station that has its type of battery available.
While it wastes energy and a little time, it doesn’t bother the robot to have to go a few miles to find such a station. You don’t need one on every popular route.
The robot can schedule an appointment for a swap if need be. Not that it really minds waiting a lot, unless it has a job to do. But with a scheduled swap it might even do one while carrying a passenger, if it happens to be passing a swap station and can book a no-wait appointment for the time it will be passing, and the passenger doesn’t mind the 3 minute stop.
Most typically, this will be used by taxi fleets. Each taxi fleet can have their own swap station, for the type of battery cases they like. They can program their taxis to take jobs that bring them closer to the swap station when they will be running low. You can get buy with just one swap station for the whole fleet, or perhaps just a few. The taxi fleet can have a mixture of cars of different swap types and cars without swap ability. The latter can’t run all day and must spend time in charging stations as planned.
With robocars, you can solve range problems not by swaping the battery, but by swapping the car. If you have a car that is running low, it can stop in a convenient lot to have you switch quickly to a taxi with lots of charge. Then the car you were in can head off for charge or swap in no paticular rush.
By allowing lots of types of battery form factors and swap stations, you allow innovation and competition in these areas, which in the long run is a win for the customer. Anything that blocks competition may sound good at first but quickly bogs things down.
Now I still want to credit Better Place for working to solve the range and range anxiety problems of electric cars. There will still be competition because I don’t expect all electric car vendors to want to be compatible with their system. But I think their technology comes into its own best when the cars can worry about the swap rather than the drivers.
I often see people say they would like to see solar panels on electric cars, inspired by the solar-electric cars in the challenge races, and by the idea that the solar panel will provide some recharging for the car while it is running and without need to plug it in.
It turns out this isn’t a tremendously good idea for a variety of reasons:
You’re probably not going to get more than a couple hundred watts of PV peak power on a car with typical cells. Even properly mounted on a roof in a sunny place like California, each peak watt delivers an average of about 5 watt-hours in a day, so 200 watts gives you 1kw-h. That’s good for around 4 to 6 miles on today’s electric cars. Not a huge range boost.
While thin film panels don’t weigh a lot the power they provide during actual driving would normally be only a minor boost. My math suggests they weigh more than the battery for the power they will provide while operating.
Panels on a car will instead be mounted flat, cutting about 30% of their output. Normally you want to tilt to the angle of the sun.
Cars are often in the shade, even parked indoors. Unless you work to pick your parking to have sun all day, you’ll only get a fraction of the power.
If you do leave your car in the sun, in many places that means it will get quite hot, you’ll burn up some of the solar energy cooling it down. (Indeed, the solar panels sometimes found on today’s hybrids and EVs don’t charge the battery, they just run a cooling fan.)
The worst one: If your battery is not somewhat discharged, it doesn’t have any place to put the solar energy, and so it is just thrown away. But due to range anxiety, people prefer their electric cars be kept full. It takes careful planning to use that energy.
A car is a very bumpy place, so you need more rugged panels than what you might put on a roof.
It is possible to get more than 200w on a car — some of the solar challenge cars that exist to be nothing but panels have gotten around a kw by using high price, high-efficiency panels. But it’s still generally much better to just put the panels on a roof where they will realize their full potential, and feed the grid, and charge from the grid.
However, on Friday I was teaching a class on the future of Robocars to my students at Singularity University and in the exercises some students wondered if they might do something for solar powered cars. (I was impressed since the students, having had only a short time to think about the issue, have to work to bring up something new.)
Robocars might solve some of the problems above, and thus possibly make sense as a place to put panels.
A robocar parks itself and can move. So one with a solar panel can move around to make sure it’s always in the sun, and that the sun is striking it from the right angle. It can’t move too far or too often without wasting some of the power, but it can do something.
When the batteries get so full that they are not making proper use of the solar energy, a robocar can find a charging station, not to charge but rather to sell excess power back to the grid and other cars. (This presumes charging stations are set up this way.)
Robocars could dock with other robocars that are more discharged and offer them the extra solar power, no charging stations involved — though fancy robotics are needed on the charging interface, or human beings who can do the connections.
If a robocar has an actuator that can tilt the panels, it can do even better. While an ordinary car could have this, an ordinary car would not have the ability to rotate in the plane of the ground to track the sun without another actuator.
It’s still not great, but it might improve things. Generally it still may be better to have the panels on rooftops and get the most from them. However, when we start thinking about super lightweight cars, cars that travel for under 100 watt-hours/mile, as well as higher efficiency panels, we might get some value if the panels are light.
It’s also expensive to install panels on top of existing facilities. Turns out that while panels are dropping below 1$/watt next year thanks to cheap Chinese capital and manufacturing, the cost of install is still over $2/watt. Cost of install on newly manufactured buildings — or cars — can be cheaper because it’s designed in from the start. The car already has the complex electrical system, while houses need to add them if they go solar.
People really are in love with the idea of a solar powered car. It’s not really possible to go green this way right now, but the future might bring something interesting.
The “burning” question for electric cars is how to compare them with gasoline. Last month I wrote about how wrong the EPA’s 99mpg number for the Nissan Leaf was, and I gave the 37mpg number you get from the Dept. of Energy’s methodology. More research shows the question is complex and messy.
So messy that the best solution is for electric cars to publish their efficiency in electric terms, which means a number like “watt-hours/mile.” The EPA measured the Leaf as about 330 watt-hours/mile (or .33 kwh/mile if you prefer.) For those who really prefer an mpg type number, so that higher is better, you would do miles/kwh.
Then you would get local power companies to publish local “kwh to gallon of gasoline” figures for the particular mix of power plants in that area. This also is not very easy, but it removes the local variation. The DoE or EPA could also come up with a national average kwh/gallon number, and car vendors could use that if they wanted, but frankly that national number is poor enough that most would not want to use it in the above-average states like California. In addition, the number in other countries is much better than in the USA.
The local mix varies a lot. Nationally it’s about 50% coal, 20% gas, 20% nuclear and 10% hydro with a smattering of other renewables. In some places, like Utah, New Mexico and many midwestern areas, it is 90% or more coal (which is bad.) In California, there is almost no coal — it’s mostly natural gas, with some nuclear, particularly in the south, and some hydro. In the Pacific Northwest, there is a dominance by hydro and electricity has far fewer emissions. (In TX, IL and NY, you can choose greener electricity providers which seems an obvious choice for the electric-car buyer.)
Understanding the local mix is a start, but there is more complexity. Let’s look at some of the different methods, staring with an executive summary for the 330 wh/mile Nissan Leaf and the national average grid: read more »
Nissan is touting that the EPA gave the new Leaf a mileage rating of 99mpg “gasoline equivalent”. What is not said in some stories (though Nissan admits it in the press release) is that this is based on the EPA rating a gallon of gasoline as equivalent to 33.7 kwh, and the EPA judging that the car only goes 73 miles on its 24kwh battery.
There is a huge problem with these numbers. If it were possible to convert perfectly, a gallon of gasoline actually has about 36kwh, so possibly the EPA is factoring in the 7% loss of electrical distribution. But in reality it isn’t even remotely possible to convert fuel to electricity perfectly.
The Department of Energy, for example, offers a number which puts under 13kwh as the energy equivalent of a gallon of gasoline. That’s how many kwh you get out of the plug if you burn coal, gas or oil with roughly the same energy as that gallon of gas. With the DoE’s number, the Leaf is getting a combined mileage of around 36 mpg-equivalent. That’s not a bad number, but there are many gasoline cars that do better than that. Even a Lexus hybrid does similar to that. This is no minor error, it’s a massive one, and it’s highly unlikely that Nissan or the EPA are unaware of it. This gives the impression of an attempt to make the Leaf seem way, way better than it is to promote electric cars. The problem with that is that when people learn the truth, they are going to be unhappy, and will be soured on electric cars, Nissan and the EPA.
Now I will agree that there is justifiable debate over the right way to do this calculation. The DoE works from its calculation of the average efficiency of power plants in the USA. People in areas with more efficient power will do better using electricity than those close to old coal plants (which are the big drag-down here.) The DoE also counts BTUs in nuclear plants (which provide about 20% of U.S. energy) as BTUs even though no fossil fuel is burned and no greenhouse gas is emitted. People must judge for themselves how “dirty” they think nuclear BTUs are, and how to value an electric car in areas where most of the electricity is nuclear. Even harder to judge are the 10% of US kwh that come from hydro. Hydro doesn’t even have BTUs or pollution, though it does come with environmental destruction. If you live in the Pacific Northwest or parts of Canada where most of the power is from hydro, you may judge the 99mpg number as more realistic, though in this case the concept of a gasoline equivalent is stretched pretty thin.
If you live in California, which burns almost no coal and gets most of its power from natural gas, and then nuclear, the real number isn’t as bad as the national average, but it’s still nowhere close to 99mpg. If you live in a place that is almost all-coal, like Utah or New Mexico, electric cars are not so great an idea — their only environmental advantage is that the fuel source is domestic rather than imported, and the coal is burned elsewhere, not right next to you.
There are other electric cars that are more efficient than the Leaf, but the big reality is that to really beat out the 50mph gasoline hybrids you need to make your car lighter.
“But wait,” some people say. We can run our electric car on solar or renewables and all is wonderful! Don’t get me started on this. There are no solar electrons. Installing renewable generation can be a good idea, but you must tie it to the grid for it to work. Not tying solar or wind or other sources to the grid is highly wasteful, because the power is discarded any time the battery is not empty (or worse, not connected.) Grid tie makes the grid greener, and people who do that can feel good about it if they do it well, but it does’t make driving more than a tiny smidgen of a percent greener than it was.
Shame on Nissan and the EPA. I hope that at least, Nissan will only sell the car in places with electricity that is well above average in quality, and refuse to sell it in places where the power is mostly from coal.
Not that I don’t understand the motivation. Had the EPA rated the car with the DoE methodology number of 36mpg, it might well have killed the car at the starting gate. It’s an interesting moral question if it’s right to lie to kickstart a technology which will become better with time. They could also have lobbied for a more reasonable but generous mpg, perhaps derived from the best natural gas plants, which would have offered a number in the 50s. Not nearly as exciting but not a car-killer, though the comparison to the Prius or Insight would not look so good.
It would have been best if they had just developed a new standard, like watt-hours/mile or miles/kwh, and leave it to the press and local power utilities to publish local conversions between “kwh” and gallons. (Not the dealers, they can’t be trusted of course.) It actually would be quite handy if every power utility were to publish, for each zone the local efficiency of the power grid in terms of BTU/kwh or greenhouse effect/kwh.
Update on Chevy Volt: The numbers for the Volt were released. As a plug-in Hybrid that can go 35 miles on its batteries and then has a gasoline engine, they rated it as 97mpg while on the battery (similar false number to the Leaf) and 37mpg while on gasoline. These numbers are actually roughly the same when using electricity at the grid national average.
Sad to say, but if you live in a place where the power comes from coal, the math seems to say you should remove most of the batteries and save the weight.
I’ve written before about solutions to “range anxiety” — the barrier to adoption of electric cars which derives from fear that the car will not have enough range and, once out of power, might take a very long time to recharge. It’s hard to compete with gasoline’s 3 minute fill-up and 300 mile ranges. Earlier I proposed an ability to quickly switch to a rental gasoline car if running out of range.
A company called EMAV has proposed a self-propelled battery trailer to solve this problem. While I am not sure how real the company is, the idea has value, particularly when it comes to robotics. As I have written, robocars can solve the “range anxiety” problem in several ways; mainly that robots don’t care about how convenient charging is, and people don’t worry about the range of a taxi beyond the current trip. But batteries are still an issue, even there.
The trailer proposal has the car hitch on the small trailer (which has room for cargo as well) and it provides the extra batteries you need when dong a long trip. The trailer is also motorized so it puts no load on the possibly small car that is “towing” it. EMAV imagines you might buy this, keep it charged, and only put it on when you need to do a long trip.
That could work, but presents a few problems. First of all, cars are much less nimble when they have a trailer on them. Backing up is much harder, and in fact novices will get completely stymied by it. You take an extra-long parking space if you can fit at all. There’s also extra drag.
We might solve the maneuvering problem a bit with a mildly robotic trailer that has a link to the car controls, making backups and turns more natural. This can be done either with steerable wheels on the trailer or just independent motor wheels which can be turned at different speeds. Such a trailer might be able to couple much more closely with the car, possibly going right on the tail so that it acts like an extension of the vehicle. This might also solve the parking problem.
Things could also be aided by making the couple and decouple very simple and easy. That’s a tall order because of safety issues, and the need for a high-current wire. The ideal would be an automatic decouple, so you could temporarily drop the trailer off somewhere if you needed to handle roads and parking where a trailer isn’t workable. Even better but harder would be an automatic recouple, obviously requiring some more sophisticated robotics in the trailer, and a fully safe coupling system.
With standardization, trailers like this could be left on lots all over a city. Anybody with a compatible electric car could, if they needed it, stop off at a convenient lot to grab a trailer. (The trailer would also be in a charging station, making automatic coupling even harder.) With the trailer grabbed there would be no range anxiety. The trailer could simply provide power, or it could go further and charge the car at high speed, allowing the trailer to be dropped off at another charging station an hour or so later. (While this sounds nice, battery chemistries may doom this plan, since you now are putting two batteries through heavy use cycles to get one unit of charge into the car, doubling the battery lifetime cost of the energy.)
While eventually trailers would need to get back to their base after one-way trips, there are lots of ways to encourage various drivers to do that. As long as the dropped
trailer is not entirely empty, you can offer drivers who take it back a ride without using their own battery, for example.
This approach might be better than the battery-swap stations planned by “A Better Place.” The Better Place battery swap is cool, but requires all cars that use it be designed around its one particular battery configuration, and that people not own their own batteries. The swap stations are expensive and land intensive, while trailer depots would require nothing but a little land and a charging station for the trailer. A special trailer hitch is a much smaller modification of a car, too.
(One variation of the “PRU” trailer has the trailer contain a diesel generator rather than a battery pack. This of course has the range of liquid fuel, and doesn’t even need a charging station where you drop it of. It’s not being particularly green when used in this fashion of course, a bit worse than a serial hybrid car. If the trailer is heavy enough it could physically push the car and not need an electrical connection to it, though people might get highly confused by steering in such situations.)
As a cheaper and more flexible version of battery swap, this approach could be good for robocars too. Robots, unlike people, will not feel too burdened by the issues of driving a vehicle with a trailer, especially if they can control the trailer’s motors or steering. Parking’s easier too, especially if they can do robotic docking and undocking. While I have written how important it is that people don’t care about the range of a taxi, the owner of a taxi cares about the duty cycle. If they robotic taxi has to spend too much of its time recharging, the return on investment is not nearly as quick. The trailer approach, like the battery swap approach, means downtime only for the batteries, not the vehicle. If the trailers are themselves simple robocars, they can move at low and safe speeds to come meet robocars that need them for a range boost. Even if not, they need not take up much space and they’re easy to scatter everywhere for quick access. Indeed, the car itself might always use a trailer and thus have only enough battery power within it to get from one trailer to the next.
Looking at new electric cars like the Nissan Leaf, we see that to keep costs down, cars with a range of 100 miles are on offer. For certain city cars, particularly in 2-car families, this should be just fine. In my particular situation, being just under 50 miles from San Francisco, this won’t work. It’s much too close to the edge, and trips there would require a full charge, and visits to other stops during the trip or finding parking with charging. Other people are resisting the electrics for lesser reasons, since if you ever do exceed the range it’s probably an 8 hour wait.
An alternative is a serial hybrid like the Chevy Volt. This has 40 miles range but a gasoline generator to provide the rest of the range and no “range anxiety.” Good, but more expensive and harder to maintain because electric cars are much simpler than gasoline cars.
Here’s an alternative: The electric car vendor should cut a deal with car rental services like ZipCar and Hertz. If you’re ever on a round trip where there is range anxiety, tell the car. It will use its computer and internal data connection to locate a suitable rental location that is along your route and has a car for you. It will make all appropriate reservations. Upon arrival, your electric car would transmit a signal to the rental car so that it flashes its lights to guide you and unlocks its doors for you. (The hourly car rental companies all have systems already where a transmitter unlocks the car for you.)
In many cases you would then pause, pull the rental out of its spot and put your electric in that spot. With more advanced robocar technologies, the rental would actually pull out of its spot for you. Zipcar has reserved spots for its vehicles and normally it makes no sense for the renter to have just pulled up in a car and need the spot, but it should work just fine. At Hertz or similar companies another open spot may be available.
Then off you go in your gasoline car. To make things as easy as possible, the negotiated contract should include refill of gasoline at a fair market price rather than the insane inflated price that car rental houses charge. Later come back and swap again. read more »
Numbers for buses are now worse at 4300. Source data predates the $4/gallon gas crisis, which probably temporarily improved it.
Light (capacity) rail numbers are significantly worse — reason unknown. San Jose’s Light rail shows modest improvement to 5300 but the overall average reported at 7600 is more than twice the energy of cars!
Some light rail systems (See Figure 2.3 in Chapter 2) show ridiculously high numbers. Galveston, Texas shows a light rail that takes 8 times as much energy per passenger as the average SUV. Anybody ridden it and care to explain why its ridership is so low?
Heavy rail numbers also worsen.
Strangely, average rail numbers stay the same. This may indicate an error in the data or a change of methodology, because while Amtrak and commuter rail are mildly better than the average, it’s not enough to reconcile the new average numbers for light and heavy rail with the rail average.
I’ve made a note that the electric trike figure is based on today’s best models. Average electric scooters are still very, very good but only half as good as this.
I’ve added a figure I found for the East Japan railway system. As expected, this number is very good, twice as good as cars, but suggests an upper bound, as the Japanese are among the best at trains.
I removed the oil-fueled-agriculture number for cyclists, as that caused more confusion than it was worth.
There is no trolley bus number this year, so I have put a note on the old one.
It’s not on the chart, but I am looking into high speed rail. Germany’s ICE reports a number around 1200 BTU/PM. The California HSR project claims they are going to do as well as the German system, which I am skeptical of, since it requires a passenger load of 100M/year, when currently less than 25M fly these routes.
I have some admiration for the PETA prize for vat-grown chicken. A winner of this prize would strongly promote PETA’s ethical goals, as well as many environmental goals, for the livestock industry is hugely consumptive of land, as it takes far more grain to feed animals than it takes to feed us, per calorie.
One part I admire, in a sardonic way, is the way it will make some people’s heads explode. The environmental destruction of livestock, and the cruelty, are well established. However many of the people who believe that most fervently also are very suspicious of synthetic foods, especially at this level. They would never say it, but they sometimes take actions which amount to choosing the starvation of people over the introduction of GMOs in the food supply. Not that the latter does not have its risks and unanswered questions, but that the costs are so high. PETA’s vat-grown chicken will cause massive debate when it comes.
But the contest is too hard (and has a 2010 deadline that seems designed to be impossible.) It requires a meat that people can’t tell from chicken that matches the market price of chicken and can sell. Oddly, it doesn’t require that the process be more efficient than chicken factory farms in terms of energy or land, though the cost pushes that way. But reproducing the texture and structure of chicken is a hard problem. Current work on vat-grown meat suggests less textured versions (for use in sausage and ground meat forms) will come first.
So I would propose a lesser prize, the production of vat-grown egg white, egg yolk and/or milk. As liquids, the task is probably an easier one. And these products have so many uses in foods, even if you can’t make something that fries up like an egg.
Of course vegetarians (as opposed to vegans) eat eggs and diary, though the PETA variety of vegetarian will insist these products come from humane farms, with free range animals, no hormones and no forced production. The agribusiness dairy and egg farms are not this way, they will point out — and they also consume a lot of land and generate lots of methane. And others will point out that overuse of eggs and dairy has health issues. But it’s a real prize.
The other way I would make their prize more winnable (if that’s their goal) would be to remove the requirement of of being indistinguishable. Instead, I would make the creation of a superior product qualify for victory. Instead of having an independent panel say “I can’t believe it’s not chicken,” I think it would be sufficient to have them say, “This is not chicken, but I like it as much or better than chicken as a meat.” And to prove this the market, where people are buying it instead of the equivalent bird. It’s true that an exact duplicate would have a faster adoption curve, but the wholly new food would get there eventually if people found it tasty. Tofu is tasty but chicken eaters don’t say they prefer it to chicken.
With eggs and dairy I think a perfect reproduction is more possible, in that you “just” have to duplicate the mammary tissue that produces the milk, for example. And this must be living, which may be a lot harder than the vat grown meat which may never fully be classed as living tissue. But my intuition says it will be easier, and fairly dramatic in effect.
I’m impressed with a great interactive map of the U.S. power grid produced by NPR. It lets you see the location of existing and proposed grid lines, and all power plants, plus the distribution of power generation in each state.
On this chart you can see which states use coal most heavily — West Virginia at 98%, Utah, Wyoming, North Dakota, Indiana at 95% and New Mexico at 85%. You can see that California uses very little coal but 47% natural gas, that the NW uses mostly Hydro from places like Grand Coulee and much more. I recommend clicking on the link.
They also have charts of where solar and other renewable plants are (almost nowhere) and the solar radiation values.
Seeing it all together makes something clear that I wrote about earlier. If you want to put up solar panels, the best thing to do is to put them somewhere with good sun and lots of coal burning power plants. That’s places like New Mexico and Utah. Putting up a solar panel in California will give it pretty good sunlight — but will only offset natural gas. A solar panel in the midwest will offset coal but won’t get as much sun. In the Northeast it gets even less sun and offsets less coal.
Much better than putting up solar panels anywhere, howevever, is actually using the money to encourage real conservation in the coal-heavy areas like West Virginia, Wyoming, North Dakota or Indiana.
While, as I have written, solar panels are a terrible means of greening the power grid from a cost standpoint, people still want to put them up. If that’s going to happen, what would be great would be a way for those with money and a desire to green the grid to make that money work in the places it will do the best. This is a difficult challenge. People sadly are more interested in feeling they are doing the right thing rather than actually doing it, and they feel good when they see solar panels on their roof, and see their meter going backwards. It makes up for the pain of the giant cheque they wrote, without actually ever recovering the money. Writing that cheque so somebody else’s meter can go backwards (even if you get the savings) just isn’t satisfying to people.
It would make even more sense to put solar-thermal plants (at least at today’s prices,) wind or geothermal in these coal-heavy areas.
It might be interesting to propose a system where rich greens can pay to put solar panels on the roofs of houses where it will do the most good. The homeowner would still pay for power, but at a lower price than they paid before. This money would mostly go to the person who financed the solar panels. The system would include an internet-connected control computer, so the person doing the financing could still watch the meter go backwards, at least virtually, and track power generated and income earned. The only problem is, the return would be sucky, so it’s hard to make this satisfying. To help, the display would also show tons of coal that were not burned, and compare it to what would have happened if they had put the panels on their own roof.
Of course, another counter to this is that California and a few other places have very high tiered electrical rates which may not exist in the coal states. Because of that — essentially a financial incentive set up by the regulators to encourage power conservation — it may be much more cost-effective to have the panels in low-coal California than in high-coal areas, even if it’s not the greenest thing.
An even better plan would be to find a way for “rich greens” (people willing to spend some money to encourage clean power) to finance conservation in coal-heavy areas. To do this, the cooperation of the power companies would be required. For example, one of the best ways to do this would be to replace old fridges with new ones. (Replacing fridges costs $100 per MWH removed from the grid compared to $250 for solar panels.)
The rich green would provide money to help buy the new fridge.
An inspector comes to see the old fridge and confirms it is really in use as the main fridge. Old receipts may be demanded though these may be rare. A device is connected to assure it is not unplugged, other than in a local power failure.
A few months later — to also assure the old fridge was really the one in use — the new fridge would be delivered by a truck that hauls the old one away. Inspectors confirm things and the buyer gets a rebate on their new fridge thanks to the rich green.
The new, energy-efficient fridge has built in power monitoring and wireless internet. It reports power usage to the power company.
The new fridge owner pays the power company 80% of what they used to pay for power for the old fridge. Ie. they pay more than their actual new power usage.
The excess money goes to the rich green who funded the rebate on the fridge, until the rebate plus a decent rate of return is paid back.
To the person with the old fridge, they get a nice new fridge at a discount price — possibly even close to free. Their power bill on the fridge goes down 20%. The rest of the savings (about 30% of the power, typically) goes to the power company and then to the person who financed the rebate.
A number of the steps above are there to minimize fraud. For example, you don’t want people deliberately digging out an ancient fridge and putting it in place to get a false rebate. You also don’t want them taking the old fridge and moving it into the garage as a spare, which would actually make things worse. The latter is easy to assure by having the delivery company haul away the old one. The former is a bit tricky. The above plan at least demands that the old fridge be in place in their kitchen for a couple of months, and there be no obvious signs that it was just put in place. The metering plan demands wireless internet in the home, and the ability to configure the appliance to use it. That’s getting easier to demand, even of poor people with old fridges. Unless the program is wildly popular, this requirement would not be hard to meet.
Instead of wireless internet, the fridge could also just communicate the usage figures to a device the meter-reader carries when she visits the home to read the regular meter. Usage figures for the old fridge would be based on numbers for the model, not the individual unit.
It’s a bit harder to apply this to light bulbs, which are the biggest conservation win. Yes, you could send out crews to replace incandescent bulbs with CFLs, but it is not cost effective to meter them and know how much power they actually saved. For CFLs, the program would have to be simpler with no money going back to the person funding the rebates.
All of this depends on a program which is popular enough to make the power monitoring chips and systems in enough quantity that they don’t add much to the cost of the fridge at all.