Tuesday, December 26, 2006

Here's a Great Idea I Haven't Implemented....Yet

Our largest use of fossil fuels was for home heating. The legacy system in our house when we bought it, was oil. With no insulation in the house, we went through a lot of oil! When we moved to our present house in 2000, the price was just over $1/gallon. Last year it was $3.50.

When deciding what to do going forward, we had already purchased a new efficient boiler. This was done by our builder in the early part of our renovation to our house, and when it happened, I was not thinking hard about long-term energy use and the best way to go about it. Some thoughts had crossed my mind regarding solar heating, but with solar, you still need a backup source, for the sun isn't shining all the time, and given the efficiency boost, I was thinking more about the great improvement the new system was going to give instead of dumping the entire technology. With time, we could then implement solar systems to reduce our use of oil. That was plan anyway.

That all changed earlier this year when the decision was made to try to get off of the oil entirely, and in a later post, I'll explain why we went with a geothermal heatpump, but here I want to discuss something we haven't done as yet: the solar wall. Check out this website: www.solarwall.com

The solar wall is brilliant. In its simplest description, it is a black piece of metal, put on a sun-facing side of the building, and it has holes in it to suck in the air heated near the surface of the metal, for the surface becomes hot by exposure to the sun's rays. If you are looking for an inexpensive method of seriously reducing you heating bills, it is worth looking into purchasing a solar wall system.

A really ingenious system is the PV/solarwall "co-gen" unit. Here you put a solar wall in tandem with photovoltaics, so you get power and heat at the same time. The combination is especially powerful, for the PVs are less efficient the hotter they get, and the solar wall can help with that problem by taking the heat away from the PVs, and as the PVs are dark, they are already the right color and produce a lot of heat by themselves. According to the website, payback times can be cut by as much as two-thirds by having the combined unit. I believe this, although it should be pointed out that the main cost of the combined system would be the PV part, and you'd probably get a better return dollar for dollar by just installing the solar wall.

A great critique of solar power is the book The Solar Fraud: Why Solar Energy Won't Run the World by Howard C. Hayden. You can get a copy of this book on Amazon.com. I don't buy all of his arguments, and he definitely has a nuclear bias, but the book is well argued and worth reading.

One of his criticisms of solar-generated electricity is that the efficiency of the solar cells is low (20% or less), and that it isn't likely to increase, due to the inherent physics of converting sunlight into electricity via the photoelectric effect. Technically, Hayden is correct, for there are good physical limits, and so far, all panels that get great efficiency, say 30% or better, all use elements that will probably remain expensive, and none get the 50% or more efficiency one would like.

But this criticism of power conversion is true of most methods of producing electricity or any kind of work (the internal combustion engine is one of the worst!). The problem is that it is easy to convert work to heat, but harder to convert heat back to work. The work-around for all efficient power units is to use the heat for other processes. For example you can use the heat to boil water to make steam that then gets turned into work by turning turbines. The most efficient power plants do that. The solarwall with the PV tie does something similar. It uses both the heat and power, and it is a great piece of engineering.

If your budget is limited, and you really want to do something to reduce your reliance on fossil fuels, definitely check out the solar wall. A properly planned system will save you money and significantly reduce your use of either heating oil or natural gas.

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