Solar Powered PC

Submitted by brad on Mon, 2004-09-13 12:53
Topic: 
Inventions
Technology
Tags: 
power

We all would love solar power to work better, but it's hard to have it make economic sense yet, at least if you're near the grid. A solar panel takes 4 years just to give back the energy it took to build it, and it never pays back the money put in if you compare it to putting the money into the stock market. And that's with full utilization. If you use panels and batteries, any time your batteries are near full the power is being discarded, and you also have to replace your batteries every so often and dispose of the old lead-filled ones. Yuk. A grid-tie can use all the power of a panel but that's an expensive, whole-house thing.

But here's a start -- a solar-using PC power supply. My PCs, like many folks', are on all day, including the peak-demand heat of the day. Desktops draw anywhere from 50 to 200 watts even when idling.

So make a PC power supply that has 3 external connections. One for the wall plug. And two optional ones, one for a 12v solar panel and one for a battery. Then sell it with a 50w or 100w solar panel -- most importantly, the panel should not ever generate more power than the PC uses.

Because of that, during the bright part of the day, the panel will be providing most, or just barely all, of the power for the PC. The wall plug will provide the rest. At night, the wall plug would provide all the power. It's a grid-tie but it doesn't feed power back to the grid, it just reduces demand on it. The 100w panel takes 100w off the grid load during the peak demand times. And we use every watt the panel generates, we never throw any away.

This is all pretty cheap to make. Today switching power supplies, even ones that take DC, are cheap, inexpensive and efficient. This would cost more than a standard power supply, and the panels still cost around $4 per watt at the best prices available.

The battery add-on is optional, but makes this more economical. It's not much more to add the ability to draw from a battery, and to charge it (generally from wall power, not the solar) if it gets drawn down. In effect, with a battery you have a very long-life UPS. Indeed, since the solar panel can almost power the PC, during a sunny day even a small battery (an 18ah can be had for $20) might make up the difference for 6 hours or more. At night, it would drain almost as quickly as any UPS battery, but still be more efficient due to the direct connection.

This ability to have a built-in, long life UPS makes this power supply (without panel) cheaper to buy than a traditional power supply and external, shorter-life UPS. Indeed, throw on a larger battery like an RV battery and you would get a huge lifetime. An 80w PC and a 50w panel and Costco's $45 RV battery would run a PC for almost 16 hours! (Not the monitor, however.)

The thing that would make this would would be the availability of the $4/watt energy rebate in California. Unfortunately, the grid-tie requirement associated with this rebate might not apply to a system like this that combines with the grid and does not feed power back to it. However, it attains all the goals the rebate had in mind -- taking load off the grid and encouraging solar -- just on a smaller scale. With the rebate, this system becomes economical to the buyer. The supply costs only a bit more than a conventional PC and the panel is almost paid for by the rebate. It saves about $14/year on the electricity bill and is actually cheaper than the existing external UPS solution.

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Comments

Lee Ackerson

Wed, 2004-09-15 02:05

Re: Solar. Some states allow grid-tied solar systems which put energy into the grid at peak load times and you can select a rate plan which pays you more for the power you put in during the day than the power you draw out at night. So, you would want to scale your solar output to break even and using it wisely could do that.

Also, we had a guest lecturer here a couple of weeks ago talking about solar and he stated that the break-even point between the energy used to make the panel and the energy generated was about 3 1/2 years, but about 2 years of the energy to build the panel( I believe those were the correct figures) was consumed in making the aluminum frame!

Lee

Gene Carman

Mon, 2004-09-20 10:00

Actually there are a whole host of folks that rely on good solar power... long distance sailors... here is an example: http://www.svmirador.net/SolarPanels.htm

In this particular case the panels supplied enough power while in the Sea of Cortez to run refridgeration, run a water maker, power SSB radio and computer. Frankly sailors can and do live off the grid.

I understand that newer more efficient panels are on the way.

I think the real key to harnessing solar power is to not depend on one single form... the combination of passive solar heating (with passive mass storage), photovoltaics, and even focused arrays for cooking could be the solution for future energy needs.

Robert Nixon

Fri, 2004-10-08 19:33

>A solar panel takes 4 years just to
>give back the energy it took to build it

Some types of photovoltaics take less than a year to reach net energy gain, and will produce 20, perhaps 30 times their embodied energy over their lifetimes. Here are a couple of links:

http://www.apec-vc.or.jp/solar/outline/outlne09.htm
http://www.ecotopia.com/apollo2/pvpayback.htm

Seb

Thu, 2007-12-20 06:56

I'm just wondering, is it possible to buy a bulk standard desktop UPS, and connect a standard car solar power panel (trickle chargers) directly to the battery installed in it? Or would this harm the UPS?

brad

Thu, 2007-12-20 12:08

I don't know about the safety, but it's not important because this is a poor idea, and quite ungreen. For solar panels to be green, you must use their power. Trickle chargers which spend 99% of their time throwing away their power into already charged batteries are a net energy loss -- it takes a lot of power to make the solar panel at the plant. They only make sense in places that other power is not available, such as a car sitting unused for a month. In a UPS, there is plenty of power.

Or do you have another purpose in mind, ie. doing this on a UPS that is not plugged into the wall, and does not have a load on it, as a way to recharge the battery, very slowly, for short bursts of usage later?

Seb

Fri, 2007-12-21 12:56

I have a couple of PCs running from a small UPS (which are switched on most of the day), just wondering if it would it actually reduce the load from the mains if I connected my solar power trickle charger directly to the battery. From what I understand, the power is constantly delivered to the PCs from the mains via the battery. If it something like that works, then thinking of buying a larger panel to connect to it.

Anonymous

Sun, 2008-11-09 19:52

I'd like to do the same but, an UPS only uses the battery when the power source goes off, it does not feed public power to the battery then feed from the battery to power your PC(s). Most of the hardware is designed to pre-detect a surge, brown out or failure which triggers battery usage.

I found this Blog while searching for a way to tie my solar panels into the UPS hardware while using deep cycle marine batteries for storage, to make for longer power output with multiple batteries in paralell.

Obviously, the attempt would void the warranty on all the hardware involved and would be dangerous without the safety measures of an electrician but, UPS technology is mass produced for a decent savings over renewable energy systems that involve $1000's for a single part.

If there is a way to modify the standard UPS, then renewable energy will be a cheap efficient way to get off the costly public grid.

So far I can operate a power drill, stereo and 2 60 watt bulbs for 2 hours using 1 motomaster 15 watt panel, a Xantrex inverter and a nautilous deep cycle marine battery.

I think that battery would last longer and be more effective if I attach it to an APC 500VA for output, instead of an off the shelf inverter.

Convergence of technologies between industrial and public sector are required to mass produce the effect but, it would be fun to make it happen in your garage before it's on the market.

Seb

Fri, 2007-12-21 13:03

Is there any budget solar power solutions, say $400, which quickly recover its cost? I keep looking at solar power, I can afford more, but my main concern is that I'm likely to move house within 18 months, do you have any suggestions?

brad

Fri, 2007-12-21 17:27

No solar power system can recover its cost compared to grid power, as yet, except in very specialized applications. You buy one because you want to spend more than grid power to be greener. At least compared to typical grid power. In California, with tiered grid power costing 30 cents/kwh, they can pay for themselves. With rebates you can compete with grid power. Without it's about 20 cents/kwh for solar.

Larger systems all need a charge controller before connecting to batteries. I don't have enough experience to know if it's a problem if you have this connected to a battery that is on another charger/controller. Trickle charge panels deliver so little power I presume there is not much harm that can come from direct connection of their power, that's my guess.

Ken Forgie

Sun, 2008-11-09 20:15

When I began my search for a way to do solar power replacement of the public system, I asked questions based on a piece work concept. I know it's a minimum of $20,000 in Canada to get a full system that might bring you down to 80% of your public electricity bill. However, the following piece work concept was suggested to me by Xantrex support, they said it would be more expensive in the long run but, at least we have options:

3 solar panels(size and power rating vary according to your needs), 1 1400 watt inverter 1 30 watt charge controller and 3 deep cycle 12v batteries, should replace 1 circuit in your home.

In theory, except for your stove. You can replace every circuit 1 at a time as funds become available.

In perspective, that removes the average basement from the public power grid. So far, I'm into the process 1 panel @ 15 watts $100, 300watt inverter $50, 1 12 volt deep cycle marine battery $125 and 1 7 volt charge controller $30... My next step is to get 2 more batteries and 2 more panels, then save for the $1500 inverter and I'll have all the lights in my office removed from the public utility.

I'd still like to find a use for the 4 UPS shells I have obtained from clients throwing them away. It's worth investigating their potential.

brad

Sun, 2008-11-09 20:18

Battery based solar is anti-green. It is only to be used when in remote areas where grid power is not available. Battery based solar systems throw away most of their power since most of the time the batteries are not in the deep discharge state that can accept the power. You want to grid-tie so any excess power goes into the grid to reduce the amount of coal and gas burned. Or you want to under-power so that you use all your solar power and never have any extra to put into batteries.

Ian

Tue, 2011-01-11 12:04

I live in the mountains on private property where the owner provides electricity via a diesel generator + inverter / battery array. His property and he won't consider PV. Anyhow an issue I have run into is when he runs the generator the sine wave is dirty so it throws my UPS into a conniption fit and essentially causes the transfer relay to bounce. My search for a UPS that can handle this has been pretty dismal so far, but I am still looking.

Anyhow I came up with the brilliant idea of a solar+battery power source for my PC. This way I could run my PC 24/7 reliably and not worry about the UPS getting smoked. I am on my second UPS now... first one lasted 3 months before the relay fused. My job requires my main system to be up and running 24/7/365 and normally this is possible, but currently I have not been able to do so and it's has been having an adverse effect on my ability to do what I need to.

So what I am trying to do is get a clear answer as to how and what I will need to build an independent solar+battery powered system to run my main PC. My last check shows peak wattage at 400, and that is when I am working with databases and compiling code. Average wattage is around 180 - 200watts (this is a multi-drive (RAID) system with a dual output graphics card).

My thought was this:

2 - 230W solar panels
2 - 12V AGM batteries
1 - 600W Inverter
1 - Charge regulator

Where I live I am in the mountains with 6.25hours of solar potential and I have a clear unobstructed view south.

Does this sound reasonable?

brad

Tue, 2011-01-11 14:26

I suspect the first step, unless you truly need a super-powered PC, would be to switch to a high powered laptop. This of course has a built in UPS and is probably easier to make tolerant of the bad power or able to run on the DC power. Since you did not do that, I presume you really need all that power but there are ways to make desktops much lower power. New monitors with LED backlights draw much less power than older CCFL ones. You can also consider having a desktop that suspends quickly and you bring it up when you want to do the intense compiler builds etc. (Check into distcc which will spread compiler builds among other machines, including ones in the cloud if you have enough bandwidth but I presume you don't.)

More rarely you can find desktop pcs built on lower power laptop components. But your laptop is going to idle at more like 10 to 20w, not 180 watts and that will make all the difference, and it's a lot cheaper than all the equipment you have.

Ian

Tue, 2011-01-11 16:33

Laptop doesn't have the drive capacity I need. There are a total of 10 drives in my system set-up in RAID 10 on an OpenSuSE Linux system. This system runs dual 30" monitors with an HDMI feed to my TV. That's where the majority of my power draw comes from, the drives. Although I am in the process of moving to green hybrid drives for laptops. Since the SATA connections in a laptop is identical to that in a PC and there is no significant voltage differences in operations, I am finding I can reduce, noise, heat and power consumption by moving to the 2.5" laptop hybrid green drives from Seagate. I should have the drive conversion complete within the next month or two.

Anyhow this primarily is a database and application development workstation I use at home that runs several virtual machines for application testing. But it's also my personal computing and entertainment system when I am not working. Basically it's my all in one solution, hence why so many drives.

At night it's part of a distributed network for protein folding and a genome project. Otherwise I would just get a 17" laptop with an external storage drive and not worry about it. When the generator is up, I am down which is why I need to find a solution. If I can find a reasonably priced UPS that can handle dirty voltage coming in, then that is the route I would run. Right now I am entertaining the idea of a solar/battery power source.

davea0511

Sun, 2011-01-30 05:27

This is what ... over 6 years old ... but it's a great ideal and such a controller still doesn't exist. There are similar things, but none of them are designed to tap 100% of the power of the panel live, and store none of it, which is as Brad says is the most economical use of solar power. In fact, the most efficient way would be to feed into the DC voltage of the computer. What you're looking at then is a solar computer PSU, just a PSU with a 12V input, which is how this should be designed. There are 12V panels that can be daisy chained.

Or a 12V to variable output DV to DC transformer, which you should be able to plug into any laptop.

Sadly, the bulk of Americans are a bad fit (and always will be) for onsite solar because they're either apartment dwellers, up north, back east, have poorly placed roofs and trees, etc

Besides, it's unlikely that the average 1m^3 of onsite panels will ever provide much more than 100Watts.

Like with Brad here, I've racked my brain for solutions and this one even crossed my mind, but ultimately concluded *fair* power-offsetting as the only solution.

I say *fair* because the problem is that all the power-offset solutions (and there are 100's of companies that will take your money to "offset your power") are total ripoffs because they don't give you ownership of the panels that they purchase with your money - and instead keep the generated power to line their pockets - it's a pock mark on the green industry that has yet to be fixed.

So I did something about it when I founded net0power. Make your PC greengridded, and then have net0power send you a check for the power + incentives (minus space rent and maintenance) earned in the southwest where they'll go. Check out greenthepower.com for more info. It's not live yet ... we're still in the startup phase.

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