DIY solar computer system, part 1
Like a lot of semi-urban computer enthusiasts who plan on living for a few decades after the onset of global warming, I have a few computers that are always on, and I wish that I could find an economically viable way of reducing the emissions generated as a side effect of the power they require. Also, when the hard times come and grid power gets flaky or drops out entirely, it would make the local warlord happy if I could use a computer to calculate optimal irrigation ditch depths, or the like. (Note to self: learn to use abacus while leisure time still exists.)
Typically, solar arrays in urban or suburban areas are tied by an inverter to the local power grid. Such inverters cost a few thousand dollars; they both allow excess power to be released to other consumers and enable the use of AC appliances without any modifications. I live in a rented property, so installing a large solar array on the roof with an inverter in the basement is not an option. But, maybe I could run a smaller array without an inverter for DC loads only.
DC vs. AC
Computers, generally designed to connect to AC power, have as their first component a switching power supply that turns AC from the wall into DC. If I had a solar array, it would output DC, which would be converted to AC by the inverter, and then back to DC by each computer’s power supply, losing energy at each step. I call this “dumb”– why not just run the computers off of the DC directly?
The problem is that if you run the computers just off DC from the solar panel, the computers die when the sun is occluded by a cloud or a planet (at night, for example).
An alternative architecture
The system I’m building has a 24 V DC power supply fed from the grid at its core. This will run in parallel with whatever solar panel I eventually set up. For starters, I have replaced the ATX power supply that came with my desktop with a DC/DC converter from Ituner.com. I then power that from a beautiful DIN-mount Sola SDN 10-24-100P supply that I got off Ebay for $33.00 ($45.82 with shipping).
For the DC/DC converter, I looked at the pico-PSU, but rejected it in favor of the slightly larger M2-ATX-HV.
The M2-ATX-HV had a few advantages:
The M2-ATX-HV is a bit bigger, but my PC case is pretty large, so that wasn’t a concern. Including all the cables and shipping, I paid $96.40 for the M2-ATX-HV– about $30 for the advantages listed above.
Stage 1 complete
The DC system has been working reasonably well for a few weeks now. Next, I have to find a cheap way to test current sharing with a solar panel, as I don’t want to commit the full $700 or whatever for a 180 W panel until I have more evidence that it will work. I’m off to the beach to start collecting sand for a little homebrewed Czochralski action.
January 2nd, 2008 at 6:02 am
Brandon,
Interesting project, but this sounds suspiciously like a perpetual motion machine to me. How will you illuminate the solar array? I realize that the blinking LEDs on the Ethernet card provide some light, but will it be sufficient to power the entire CPU? Especially considering that your stuff (x86 architecture) dissipates so much heat… no offense, I’m just saying.
Here’s a more promising approach. Using a public internet kiosk, write a Python program of moderate complexity in an editor with a very large undo buffer. Now, return home and have a specially trained monkey repeatedly press the Undo key combination (’u’ in vim — no wonder everyone says this editor is so hard to learn) to slowly reverse the program creation process. You should find that everything else happens in reverse as well: the CPU becomes very cold, the cooling (heating?) fan spins in the opposite direction, and the power supply inputs can be used to run other appliances. Hook up a few Diebold machines and you’ve got yourself a truly ‘green’ polling place!!1!
Sure, you will have to continually inject energy into the system in the form of bananas to feed the monkey, but that will be true of any monkey-based design.
Lord K.
January 2nd, 2008 at 9:35 am
Hey Brandon, could Goelzer.org (the philanthropic arm of M W Goelzer & Associates LLC) just donate the bloody 700 bucks to solarize this thing? I really think you’re on to something here, but my understanding of analog design basically starts and ends with Ohm’s Law, so I don’t know how to help. Unless you have a question about Ohm’s Law?
But seriously, please consider: if you could devise some sort of kit for a combination solar + grid power supply that can be swapped into common OEM computers, I think a lot of hobbyists would be interested. “Kit” to me basically just means:
- a precise list of parts with links to the vendor’s site
- a set of detailed instructions for how to put everything together
- the files to print the PCB (if any… this project seems to require only finished subassemblies?)
- optional: a bucket of sand, one monkey, bananas, a Python interpreter written in Python
I’d be pretty interested in setting up a web server powered (almost) entirely by good old California sunshine. Also, if we both do this, we will be able to continue trading silly email messages even after the Hard Times come. If that’s not reason enough for you to finish this project and post the results, I don’t know what is.
Mike
P.S. Is that a Dell E521 in the last picture? It looks a lot like one I have.