Active solar heating

Active solar heating systems are a novel approach to improving the energy efficiency of your home; compared to putting photovoltaic cells on the roof, they can be attractive, and inconspicuous.  The basic mechanism of an active solar system is to put a solar collection surface, usually of a dark color, with tubes that transfer the heat transfer fluid to a storage tank.  These are called active systems because any electricity generated is used to move the heating fluid around the system, where it can do the most good.

Active solar heating systems are easier to retrofit into a house, because they use much of the existing infrastructure, or because they can be part of a remodeling job in the attic.  Important considerations in this style of solar heating systems are the choice of the working fluid.  If you're using air, the warm air from the system heats up a bed of rocks or clay pellets, which then re-radiate heat back into the system after nightfall.  Air-driven active solar heating systems are the most affordable ones on the market, and the simplest ones to install and maintain; you never have to worry about your air-pipes freezing and bursting, for example.

Solar heating with water as the working fluid takes advantage of the incredible thermal capacity of water as a liquid; water is one of the most efficient heat transfer systems around, which is why wet clothes are a risk of hypothermia.  Water requires a pumping mechanism, which air flow systems do not, but it's also much more efficient per unit volume of heat transfer fluid.

One of the mechanisms used on active solar  heating sytems to make water run efficiently, and to power the pumps needed to make them work, is a refrigerant cogeneration system, or a small photovoltaic system (small photovoltaic systems are also used to power fans for directing air flow in air driven systems).  The refrigerant will heat up, expand, charge a compressor, which discharges and moves water through the system at a faster rate than it circulates.  This can also be used to power an air conditioner, which can be a nice benefit. 

The second major advantage of a water driven system is that it can completely replace your hot water heater system if you have a reservoir that's large enough, and you get enough sunlight.  For homes that are built with these systems in mind from the time the plans are drawn, you can make a water-heating system that runs warm water through hose underneath a sealed concrete floor, as part of a ground floor heating system, with the southern facing wall painted a dark color, and used as the primary collection point from the get go.

Active solar heating solutions are affordable, environmentally friendly, and a good investment in the resale value of your home; even if they won't pay for themselves in the immediate term with reduced utility bills.