So, having whipped the furnace demons, it’s time to move on and investigate other means of reducing our energy usage. The next obvious step is either solar or wind. I presumed that solar was right out, after all I do live in Seattle, so I jumped to wind.
Making a long story short – fuggetaboutit. Wind is ridiculous for the small home, cost for a single, small, turbine will run about $1,000. With a production well below the kilowatt range, you’re talking about a payback period measured in decades. It is clearly more efficient to throw that kind of money at your electrical provider and let them build a small wind farm for everyone.
So I picked up looking as solar. Solar for electricity falls in to the same ridiculous bucket as wind. However, solar water heating is very economical. That was a surprise. A couple of years ago The Seattle Times ran this article as a quickie to get people excited about the possibilities of solar in Seattle. Then I started finding stuff like this, explaining this newish technology for solar water heating. This is not your father’s solar panel.
Basically they use evacuated tubes with copper bars on the inside. The vacuum makes a perfect thermal insulator, and the reflective coatings trap radiation from escaping. This allows for maximal energy gathering. Very, very cool. So how well does it work?
Well, I had a 20 tube system installed. This is what is looks like:
And here is a close-up of an evacuated tube. Fwiw, the tubes are made out of an impact resistant glass, a baseball bat takes about 20 good whacks to break thru. Even if a tube does go down, it just drops the efficiency of the system. My system is warranted for 20 years. Woot! Below you can see they put a thin "fin" on each copper bar to catch as much sun as possible, which then termally transfers up each copper bar to the insulated header, where a glycol mixture is heated.
Yeah, yeah, but does it work? Here’s what it looks like outside my window right now… (it’s about 68F)
and here’s the temperature at the solar panel (120F). It would be higher, but it’s currently heating water…
Wow. Ok, ok, so it seems to work. Real life impact? A quick tour of PSE.Com and here are the results (drum roll please)….
We went live on the solar panels on May 14. Our gas usage for water heating has been halved during our cloudy months. Because we have a hot water re-circulating system (yes, on a timer), our house bleeds more energy than a house that just has a static tank.
Net gain for the environment: Over 12 lbs of carbon per day saved. For us, about $1.50 per day during the cloudy months. In summer we’ll save even more. With federal tax credit, etc, payback looks to be in the 11 year range. Very affordable.
Careful with the "halved" analysis. You can tell from the graph that the data is quantized to integers. And seeing as how on even on some pre-solar days usage dropped to 1, I think it’s fair to say that a typical day might not actually be much higher than the mid-point (presumably anything above 1.5 is rounded to 2 and anything below is rounded to 1).You need to look at numbers with a lot more precision than single digits before you go thinking that you’ve actually cut your energy usage in half.