Post
by kman » Mon Jul 12, 2010 1:23 am
I've been browsing several dedicated solar forums lately, the two requests I see that come up most often from beginner solar enthusiasts are:
1) solar air conditioning
and
2) solar refrigeration.
It generally takes very little time for the people who really know their stuff to convince others that it's either impractical or downright impossible to do at this time. Solar just isn't there yet. (refrigerators are somewhat possible, but fairly impractical, while AC is pretty impossible... but it's still usually more cost-effective to go with a propane-based fridge over solar)
The issue with solar is you usually can't run the output directly into the device to run it, you need to tame it into a bank of batteries first to smooth the power output. The solar panels basically exist to recharge the batteries at the same time as the electrical devices draw power from the battery bank.
The biggest issue with the batteries (other than sheer cost!) is the size and weight of the battery banks you need to smooth out the voltage swings throughout the day, and to deal with cloudy days, winter, etc. (that last is obviously not an issue for us on the playa, but we do get nights!)
Even with the right batteries, the panels needed to push 1500w into a hungry AC unit would be prohibitively expensive, while the generator needed to run one (while loud and non-green) could easily be had for under $500. (more like $1k for a nice quite honda, but still)
Best prices I see on eBay for solar panels tends to be $200 for 100w. So that's $3k in panels alone. Then you need a really good (or several really good) charge controllers to tame the output (many hundreds of dollars there) and a pretty impressive bank of batteries to dole out the smoothed out power (many hundreds, if not thousands, and an obscene amount of weight).
Vs. $1k for a generator, and a hundred or two in fuel (at the most).
This is a bare-bones explanation, not meant to be comprehensive, in case there are any experts reading this getting ready to crank up the flame machines... There's a lot more that goes into it. Battery banks can only be depleted so far without seriously damaging them, so extra capacity over what you'd think has to be factored in. The conversion from DC battery current to AC current via inverters is not 100% efficient, so you lose a percentage of the power you're generating right there, too (easily 10-20%, depending on a lot of other factors)
I look forward to the day when we can run power-hungry devices off of renewable, clean energy like solar and wind. But outside of theoretical solar models and massive wind farms, we're not at the point where it's practical for most individuals to do so, particularly not for a short event like burning man.
One thing you can do with solar, however, is run a swamp cooler, which only needs power for a water pump and a fan. But even there, scaling a swamp cooler up big enough to cool a big dome is going to be a little challenging. I think it could be done, actually, but you're still going to pay a LOT more for the solar rig to run the swamp cooler than you would just to buy a generator, and you'd have much lower temps with the real AC, too.
)
