Solar Water Heaters

Q: What is a solar water heater ? Solar water heater systems use sunlight to heat water. The main parts of the system are a collector, a water storage tank and circulation system. The collector is a glass panel fitted with black water pipes that absorb the sun’s radiation. The storage tank is usually made of steel and is insulated from the cold. The circulation systems consists of the water pipes that move the water between the collector and water storage tank.

Q: How do solar water heaters work ? Cold water is pumped (or flows by pressure) to the collector where the sun heats it. The heated water flows back to the collection tank. Since hot water is lighter than cold water, the heated water in the pipes moves up towards the tank, which sits at a higher level, and the cold water sinks from the tank to the bottom of the collector, creating a natural circulation cycle. When you turn on the hot water faucet in your house, the hot water from the top of the tank flows to the faucet.

Q: What is the difference between an active water heater system and a passive system ? In an active system the water is pushed into the collectors by an electric pump. The collector and tank do not have to be near each other. Passive systems rely on gravity or water pressure to circulate the water through the collectors. The water storage tank is placed above the collectors. Most systems in Israel are passive.

Q: What happens if I want to take a hot shower at night ? The water storage tanks are insulated very well and will keep the water in the tank hot for many hours after the sun goes down.

Q: What happens during winter when the days are cloudy ? Inside the water storage tank there is a heating element that can be turned on by a switch inside your house. If you used up all the hot water in the tank or there was not enough sunlight to warm the water, you can turn on the heating element. Depending on the size of the tank and the weather outside, you can usually get enough hot water for a shower or laundry within 20-30 minutes of turning it on. Many homes have a timer which can automatically turn the element on and off during the winter days. During the cloudy winter days, I set the timer to turn on 30 minutes before my morning shower. Index

Q: Why are solar heating system so popular in Israel ? During the 1950's there was a fuel supply shortage in Israel and restrictions were placed on when people could heat their water. Many Israelis started to purchase solar water heaters. In 1980, the Israeli Knesset (Israeli Parliament) passed a law making solar heating mandatory for new residential buildings. The law has saved Israel and its citizens millions of shekels in energy costs. As the systems improved and mass production lowered the cost, more companies entered the field and today purchasing and installing (usually by the builders) a solar water heating system is commom practice. 28 years after the Israeli government's decision to promote the use of solar water heaters, Israel is still one of the top countries in the world (percentage of population) using solar heaters and saving money on water heating bills.

Q: What size storage tanks are available in Israel ? Water storage tanks range from 30 to 300 liters. The tank size for the daily hot water needs of an average family is 150 liters.

Q: What does an average solar water system cost in Israel ? The cost of a system depends on the size of the water storage tank and the number of collectors installed. A system consisting of a 150 liter storage tank and two collectors is around 2,800 - 3,500 Shekels (July 2008). This includes installation. Index

Q: What is the warrenty for solar water heating systems ? The warrenty (from selected vendors) for the system listed above is 8 years for the collectors and storage tank.

Q: Do the solar water heating systems require maintenance ? Solar water heating systems require periodic inspections and routine maintenance to keep them operating efficiently. Also, from time to time, components may need repair or replacement. On an annual basis, visually check if any new construction or objects are blocking the collectors. Shading can greatly affect the performance of solar collectors. Dusty or soiled collectors will perform poorly. Periodic cleaning may be necessary in dry, dusty climates. Check storage tanks and piping for cracks, leaks, rust, or other signs of corrosion. If you use the heating element on a cloudy day and the water is not getting warm quickly, it could be that dirt and small pepples (that sometimes get through the Israel water system) may have accumulated around the heating element. You should contact the installation company to clean the storage tank and the heating element inside.