Is being evangelical about solar the right course?


The earlier post on whether solar gives the best bang per buck in greening our electricity ran into some opposition, as I expected. Let me consider some of the objections and issues.

As a recap, I put forward that if we are going to use our money and time to attain greener electricity, what matters is how many MWH we take off the "dirty" grid (particularly coal plant output.) I measured various ways to do that, both green generation and conservation (which do the exact same thing in terms of grid offset) and worked out their cost, the MWH they take off the grid and thus the cost per MWH. Solar PV fares poorly. Converting incandescent bulbs to fluorescent in your own home or even other people's homes fares best.

A big part of the blame lies on the fact that crystalline silicon is an expensive way to make solar cells. It is, however, quite common since many PV plants started with technology from semiconductor fabrication.

Evangelical green

One frequent objection is that purchasing expensive solar panels today encourages the market for solar panels, and in particular better solar panels. Indeed, panel makers are generally selling all they can make. Many hope that this demand will encourage financing for the companies who will deliver panels at prices that make sense and compete with other green energy.

I call this being "evangelical green." Leading by example, and through encouraging markets. While I understand the logic, I am not sure I accept the argument. * Are people who can build $1/watt (superior to grid) solar panels really not going to get funding because there is not strong demand for solar panels that cost well above grid? * How valuable is this marketing bump? Can it justify the $200/MWH higher cost of solar? * What if the money went instead into lobbying, or into investment funds targeting cheaper solar panels? * Is PV truly the right thing to encourage in this way? Might thermal-solar, wind or other forms of power be better choices?

Even if the panels are free...

I added an extra line to my spreadsheet on the cost-effectiveness of green approaches evaluating free solar panels. That is, I presumed that today's $4/watt panels (*) were free, but you still paid about $3.80 per watt for installation, grid-intertie equipment and inverters, and permits. Remarkably even free panels are worse than all the other examined methods. One hopes, of course, that free panels would cause reductions in the non-panel costs, especially permits, but this is still a remarkable observation.

(*)One commenter suggests $4.70/watt is a more accurate number. Dropping non-panel costs to $3.10 puts free PV at $121/MWH, beating the PC power supply, and perhaps the gas dryer but still losing to everything else.

If the PV industry is indeed selling all the panels it makes, and is able to get large government subsidies as well, doesn't this suggest that other promising technologies are the right thing to encourage. There may even be other technologies, like natural gas microturbines for large buildings, which are not 100% clean but are much greener than what we do now.

Another technology with much promise that gets little attention is that ancient form of solar powered lighting called the skylight. Consider that offices, warehouses and stores often have lighting on during the day while the sun shines outside. Some even have put up solar panels, which then power that lighting -- taking perhaps 2% of the light that falls on the panels and emitting it inside the building. Modern skylighting technologies can pump a vastly greater amount of that light where it is needed at lower cost. Why aren't we subsidizing that?

We can't fix the problem with just conservation

I agree with this. However, pure increases in efficiency achieve conservation but they are sacrifice-free conservation,and so never a bad idea. However, PV solar is not simply a poor buy compared to conservation, it's a poor buy compared to other forms of generation, such as solar-thermal, geothermal, large wind farms and even modern nuclear power (about which you may have other opinions, of course.)

But if your goal is to have an effect now, to spend your resources to make the world a greener place, should you not start with where you can do the most good? The answer to energy problems will come from both increased efficiency and cleaner generation, not just one of those things. What's more debatable is whether it can come from conservation through personal sacrifice.

If it's PV you want, the panels are not all of the problem

As noted, even free PV panels can't compete with other methods of going green. However, this tells us that if we want to focus on something, these other cost components might be as worth attacking, or even more attacking.

After all, all forms of local generation will require cheaper inverters and intertie, and cheaper permits in most cases. Working on those will help not only PV but other localized energy forms. For example, right now there is no way to properly use PV at all except in a large installation.

Systems that could use PV combined with grid power to replace all the DC wall warts in a house might make a big difference. In such systems, a small panel, easily self-installed with low power wiring would tie into a power supply that powered many always-on DC devices. The panel would never quite generate enough power, it would always be supplemented with a bit of grid power coming through a switched mode power supply, and full grid power at night. If this power supply was mass produced, it would allow simple panel use (replacing highly inefficient wall warts) with no costs for permits, intertie and install.

I described an early form of this idea for a solar powered PC 5 years ago, but now that I realize how inefficient all our wall warts are, it might make more sense to attack them with small solar setups than the PCs.


A lot of what you are suggesting is inaccurate- which is unfortunate if this blog is widely read, which I suspect it isnt.

Given the fact you are still assuming $4/watt panel prices it is clear your industry knowledge is pretty low and your statements reflect that. lists current module pricing.

Its a shame you are peddling this.

Also- regardless of install cost, solar is one of the most effective ways of generating baseload electricity. Thus, you need to compare the return on a 'peaker plant' that only operates a few hours a day, as the numbers on those are not favorable. This opportunity cost of avoided use of such technology doesnt show up on your spreadsheet, nor should it.

Calling solar wasteful is irresponsible

I am surprised at your attitude, considering how the site you point out not just backs up my numbers, but provides more pessimistic ones in many cases. It cites a current average of $4.70/watt retail, higher than the $4 figure I used, but also indicates the range is wide, and some panels have been found under $3/watt. I think it's a good number for an aggressive shopper (I have paid less myself) but it doesn't change the equation much if you use $4.70 -- you can play with the spreadsheet and plug it in yourself.

If you think I am "peddling" (I have nothing to sell) false numbers, you need to show me what you think the correct numbers are. The solarbuzz site you refer to offers numbers suggesting a residential unsubsidized price of solar in a sunny climate of $370 per megawatt hour, higher than the number I calculated, though they rate a better $208/MWH for large industrial/generation PV plants. While a better number, it is still not good enough.

You have it entirely backwards on baseload electricity. Solar is terrible for baseload. It is good at peak load times only. (You may have just gotten your words backwards there, if so, I apologize.) However, the situation I am examining here (see the earlier articles for more detail) is the considering of a solar plant for a home or office, with the goal of reducing the use of the dirty grid. Solar, by providing power mid-day, saves a power company from having to build peak-load plants but I don't care too much about their cost of building plants. If I am interested in making the world greener, I care how much fuel they burn, and that's pretty related to how many MWH they have to generate. (The nuclear baseload capacity does not emit air pollution of course but people are of varying opinions on how green it is.)

If you think my numbers are wrong, show your numbers. Look, I want PV to work, I understand all its advantages, but today I can't find math that shows that it works, that shows it as a good choice for making the world greener in terms of dirty MWH removed per dollar of expenditure on PV.

Even if you happen to live in a sunny location with a large, flat, southerly-inclined roof, regulations discourage you from putting up six times the number of PV panels you need and sending the extra to your shady neighbors. You could install the extra panels and gift the electrons back to the electric company. But if you want to sell them, welcome to the world of Being A Regulated Utility. At least in California.

This is correct, but in California you are crazy if you put up so much PV that you go net-negative on your meter. California has a tier system. You pay a low rate on your first 360 kwh, and really high rates above 720 kwh. So your goal is to get your total grid usage to about 360kwh, and then pay the cheap price for that much grid power. Or even to drop only to 720kwh. Only this way can solar compete with grid in California. If you overgenerate and take yourself below tier 3 or tier 1 or even to 0, you are paying more and your panels will never pay for themselves.

If you are doing this out of a desire to do good for the world and make it greener, as I have been learning and showing, there are far better places to spend your money making a greener grid.

For electric cars, add time-shifting power generation to the list of benefits.
Cars charged at home at night, driven to work, plugged into the grid which
discharges them. This reduces peak load on the conventional power
generation system. So, as anon notes above, peaker plant costs become
a factor in the equation.

I see this talked about for electric cars, or more often for hybrid cars which, in a brown-out, would offer their dirty gasoline generators. The latter is of course not a green solution at all. I don't see the all-electric solution happening very often. Right now the biggest barrier to electric cars is people don't think their batteries provide enough range, and that finding a place to plug them in is a pain, and that once they are discharged not only do you need to find such a place but the car has to sit there a long time. They compare that with gasoline's "stations everywhere, refuel for another 300 miles in 4 minutes."

So, unless you are really sure an electric car will not be needed by its owner for quite some time, they won't let you do this. Peak electric demand is at 4 pm, just before rush hour, and no owner driving then will let you drain their battery.

You could use the batteries of electric cars in airport parking lots and those of people on vacation and the like. That could help, though you would have to pay them for the extra cycles on their batteries which will reduce lifetime.

But none of this changes the total MWH load on the grid. Since peak load comes from natural gas (and some hydro I suspect) and base load from coal, nuclear and hyrdo, you might end up moving load from natural gas to coal with the use of batteries in this fashion.

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