Sunday, June 6, 2010
The heat is up
When most people think of sun and going green, they immediately relate to solar power. While a PV array is part of the NobHillHaus' concept, it is not the only way the resource sun (of which we have plenty out here) can be harnessed. By far the simplest is to use the energy of the sun directly to heat the water to be used in the house.
A solar water heater can be a very simple device- and if you browse the web, you'll even find sites that show you how to build your own using old refrigerator parts. It is really amazing, what is current happening in underground green technologies.
There are 2 basic systems of solar water heaters: A passive system (i.e. essentially a big storage tank on the roof that uses the sun to preheat water from the city's water supply. The pre-heated water then passes thru a backup heater and when the water isn't warm enough anymore- e.g. when you and your whole family have your morning shower- the backup heater kicks in.
This system does not contain any moving parts, is simple (does not contain a secondary circuit) and works only for non-freezing conditions (i.e. NOT in Big Bear). However, if the water is either too hard or too soft, the system may suffer damage over the years and it is to our surprise- since a lot of large format copper tubing is used- actually more expensive than an active system.
Which leads us to the other option:
An active system has a separate loop from the water tank to the rooftop heating panels (they're much smaller in size and cost way less than the passive panel).It also needs a pump(which needs power and is a moving part that can break down)to circulate the water in the loop. Heat is exchanged with incoming city water in a tank. At the exit of the tank is an instant backup heater for emergencies.
In our case, the active system was 30 less than the passive one, so the decision was a no-brainer. But everyone needs to evaluate the situation in regard to their own personal needs. There's a lot of different suppliers out there (ProgressiveTube for passive, Heliodyne and Sunearth for active systems).
Whichever you choose, you can be assured, that you save quite a bit of CO2 and fossil fuel.