Perhaps the ULTIMATE in Green water heating technology is the solar water heating system. After all, what could be more Green than utilizing the ultimate FREE energy sourceSUNSHINE! Solar water heaters take the heat and energy from the ever abundant sun itself and transfer the energy to water using solar energy collectors. Solar water heaters are rated for efficiency using their own special factors.
The first is the solar energy factor, which is measure of the total energy delivered by the system divided by the conventional electrical or gas put into the system. The higher the solar energy factor, the more the system relies on solar energy and the more efficient. The solar energy factor is rated between 1.0 to 11. The next rating used is the solar fraction. The solar fraction scales from 0 to 1.0 and is the portion of solar use in the total water heating load. Thus a solar water heater that has a 0.5 solar fraction derives approximately half of its total energy load from the sun.
The most important component of the solar water heater is the solar collector. The solar collector is the part of the system that absorbs the suns energy and transfers it the hot water system. Flat plate collectors utilize a dark absorber plate, usually housed in an insulated box and sometimes covered by glass. The dark absorber plate absorbs the suns energy and transfers the heat to the water in the insulated box.
Integral collector storage systems or ICS solar systems use black tubes where cold water passes through and is pre-heated before entering a conventional backup water heater. Evacuated tube solar collectors are fairly complex and expensive systems that utilize air-evacuated glass tubes that prevent heat loss, and contain metallic fins and pipes that are coated in heat transferring material that transfers heat to the fluid that moves through the glass tubes. Although each type of solar collector is uniquely engineered, they all share the purpose of absorbing the solar energy and transferring it to the water heating system.
After the solar collectors have done their job, the heated water must travel into the homes water system. Active systems utilize direct circulation with a water pump that moves the water from the collectors to the backup water storage tank. Or they use indirect circulation with a non-freezing heat transfer fluid that moves through the collectors and a then through a heat exchanger that moves the heat to the water. This active indirect system is the best for freezing climates, as the anti-freeze fluid is the only fuild exposed to the cold, while the heated water stays insulated and absorbs the heat via the heat exchanger.
Passive solar water heating systems don;t use pumps, but instead rely on thermosyphon principles. Warm water rises, cool water sinks, so the heated water is stored on the roof in a tank, while the cooler water naturally sinks down below. These systems must be carefully designed due to the extra weight of water storage on the roof system!
All solar water heater systems usually have a backup heating source, such as electric or gas that heats the water in the storage tank in case of cloudy days. However, overall solar systems are amazingly efficient. Many homeowners are initially shocked at the initial cost of a solar system, but actually they can save money in the long run.
According to the U.S. Department of Energy Solar water heaters can use 50% to 80% less fuel than a conventional water heater. This can add up to a pretty hefty sum of money over a few years time! A solar water heater typically will pay for itself within 4 to 8 years when installed in a sunny climate. Because of the longterm financial savings, solar water heaters are very frugal investment when they are rolled into a mortgage during new construction, or refinancing. By the time the heater is paid for in the mortgage, the energy savings will have paid for the system and then some!
Remember the frugal principle of solar energy: SUNSHINE IS FREE! Popular solar brands are Fafco, Rheem, Apricus, Helodyne, Solahar and Stiebel-Eltron. Contact a contractor that specializes in solar water heaters to get an estimate and start using this free energy source to heat your water today!