How Solar Water Heating Works
Solar Thermal Fundamentals:
- Capture heat from the sun on your roof
- Store this heat in a water tank
- Use it when you are ready for it
Solar energy is harnessed for productive use in the home in two fundamentally different ways. Solar electric (PV) converts electromagnetic radiation from the sun into electricity while solar thermal water heating systems convert solar rays into heat (this discussion will cover only solar thermal water heating systems). The available sun energy varies throughout the year, but we can design systems for our area that maximize annual production. Because solar systems offset the use of fossil fuels with free energy from the sun, there are financial and environmental benefits associated with their use.
SolarWerks in Chicago:
- We have comparable hours of annual sun to anywhere in the US outside of the desert southwest.
- Energy demand is higher in the northern climates so the value of a solar system is greater.
- Illinois is serious about developing renewable energy systems and has attractive incentives to encourage them.
- We currently have modest electricity rates and high natural gas rates—both are poised to go up.
Solar hot water systems consist of three major components: the solar collectors (panels), a solar storage tank and a circulation system. Flat plate solar collectors are composed of an insulated aluminum box with a tempered glass front. Behind the glass is an absorber plate connected to a grid of copper pipes. A south facing roof with unobstructed sun all year from 10am to 2pm is ideal for a solar water heater (9am - 1pm or 11am - 3pm works great too).
Solar collectors connect to a liquid-to-liquid heat exchanger via insulated pipes or hoses that are plumbed into the solar storage tank. This tank, which is usually slightly larger than a traditional water heater, stores the solar-heated water and supplies it to your existing water heater.
Solar hot water systems in our climate circulate a non-toxic antifreeze mixture to heat the water in the storage tank. When the sun shines on the collectors, the fluid absorbs the solar energy and becomes hot. A pump circulates the fluid through the insulated hoses to the heat exchanger, which transfers the heat from the fluid to the water in the solar storage tank. The fluid is then pumped back to the collectors and the process begins again.
Solar hot water systems are very reliable, with a long and successful track record in the Chicago area. The collectors and insulated piping can last the life of the home. The circulating pump, tank, non-toxic antifreeze mixture and other minor components are subject to wear and may need to be replaced eventually. The system should be checked every five to ten years by a qualified service technician.
