Solar Hot Water Heaters
Before you buy and install a solar water heating system, you need to first consider your site's solar resource. The efficiency and design of a solar water heating system depends on how much of the sun's energy reaches your building site. Your contractor should figure out both the orientation and tilt of the collector to maximize your solar water heating system's performance.
A variety of solar water heaters are available commercially, most of which should last 15 years or longer. The choice of the right type of solar water-heating system depends primarily on the climate where you live. The crucial fact is that if a water-filled pipe is exposed to freezing conditions, the water inside the pipe will freeze and the pipe will burst. They are divided into three categories:
- Active systems - uses pumps to move the heat-transfer fluid,
- Thermosiphon systems - where the heated water rises naturally from collector to storage tank, and
- Batch systems - where the solar collector is the water tank.
Collector Size
Basically the size involves determining the total collector area and the storage volume you'll need to meet 90%–100% of your household's hot water needs during the summer. A general guideline is around 20 square feet (2 square meters) of collector area for each of the first two family members.
Storage Volume
A small (50- to 60-gallon) storage tank is usually sufficient for one to two or three people. A medium (80-gallon) storage tank works well for three to four people. A larger tank is appropriate for four to six people. A larger storage volume tank increases the capacity to deliver hot water and lessens the risk of running out of hot water..
Active Water Heaters
Active water heaters use solar panels or collectors to trap the sun's heat. Water running through the collectors increases in temperature as it absorbs heat. The warmed water is then pumped to a storage tank. These systems are called "active," as opposed to "passive" because they use electric pumps to move the water from the collectors to the storage tank. In passive systems water moves naturally because of a temperature difference. if use effectively, active Water Heaters can save up to 70% of a family's annual hot water costs . For instance, doing laundry, dishes, etc. during the day.
Below is a historical perspective on solar hot water heaters.
In the 1890's 30 percent of the homes in Pasadena, California were equipped with solar water heaters.
By the 1920, ten of thousands of solar water heaters had been sold. However the discovery of oil, which inexpensive at that time, started replacing the solar systems with heaters burning fossil fuels. Today, solar water heaters are making a comeback and over a half a million solar water systems are in California residence and businesses.
