Solar Computing - My Experience

by Glen Gillmore

Related link: http://www.oreillynet.com/cs/weblog/view/wlg/1559



Simon St. Laurent asked about computing when off the traditional power grid.



It just so happens that I've lived with solar power for ten years. I'm sure my set up is crude, but it works fine for me. I've got two solar panels that are rated for about 125 amps. These are
connected to four 12-volt marine, deep cycle batteries. I run a television, phone answering machine, lights, Sony PlayStation, DirecTV, laptop, and my propane refrigerator's controller all from it. I
do have a generator, but it is for the recharging of batteries, microwave, washer/dryer, and dishwasher.



I'd suggest the best way to go is with an inverter located within 2 feet of the solar batteries and hard-wired into the system (no cigarette lighters or alligator clamps). 12v DC has enormous line
loss so it is more efficient to convert it to 110v AC near the source, and then run a 110v line to the laptop/printer. I've found that my configuration is very cranky if I attach a surge protector to
the line, so I don't use one when connected to solar. When connected to the generator, I use a really good one. I know of folks who run a desktop machine from an inverter, but they often spend the
night in complete darkness when their batteries have run dry.



The best inverters use SINE or MODIFIED-SINE waves. These are very efficient and often very expensive. For $50 you can find a regular one anywhere -- these will run about 300-400 watts, which
should be plenty. Get one that has a fuse and a fan. If their system is very primitive (like mine), I suggest adding meters for both amps and volts.



Depending on the laptop, you might find one that uses 12-14v DC to charge the battery, allowing a more direct solar-to-laptop charging solution. Or if you've got solar to spare, you can just be happy
converting 12v to 110v then back to 12v.



The laptop solar panels are ok, I presume. It probably won't run your laptop when the battery goes dead, but can be a solution if you only need to use the laptop 1-2 hours a day. It might take an
entire day or more to recharge.



When I first started with this, I got a catalog from Sunelco. I think it is a terrific way to get educated about all of this.



You might also look into getting solar arrays that shift with the sun on a rotating/pivotal motor. If there are enough panels, it is worth the loss from the motor. In a dense forest, I'd think
shade is a big issue/concern when considering solar power. Keeping the panels pointed at the best sun is always a good idea.



There are also river/stream/ocean generators that generate electricity from water current -- if that's available and you want to get fancy.



I live at the beach, and it gets windy - not to mention foggy. For about 3 years I had a wind generator. It worked well for a while, but it sounded like I was living on the runway of a small
airport because of the propeller noise. The diversity of wind, solar, and my generator made for a good mix. Mine died during a storm with 100mph gusts that sheered the blades right off. The same gust
(at about 6:00am) took the roof off a nearby mobile home. Even with new propeller blades, it never seemed to work well after that. If you consider this, look into a model with a head that tilts. This
forces it to stall in extreme winds. I also understand that there are some quieter models available now.



If I just wanted to power a laptop and ink jet printer, I'd get the following:




  • A 50-75w 12V Solar panel $350-$400


  • Two deep cell marine batteries, sealed connected in parallel - from any auto/marine supply (I get mine at Costco) $60 each


  • 400w Inverter $50


  • Extension cord, heavy duty $20


  • Wire, fuses, fittings, etc $40



There are all sorts of regulators and other options available, but like I said, this crude system works fine for me.