Solar hot water (SHW) systems use the “greenhouse effect” to heat water or air in a thermal collector and suitably-sized storage tank or ducting system to supply hot water and heat for use in homes and businesses. SHW for domestic hot water works as a pre-heat system that operates along with your existing heating source by preheating the incoming cold domestic water, with the existing hot water heater as a backup.
The same solar heated water can be used to provide space heating. There are also thermal collector/fan systems that heat the air directly and are very efficient room heaters. If the sun is shining, your home or business is heated with clean, inexpensive solar energy. If the sun is not shining, then additional heating is provided by your backup system.
Over a year, a SHW combi-system can provide as much as 60 to 65 percent of all water heating needs and 20 to 50 percent of your space heating needs, even in cold climates. During the summer months, the system operates at its maximum, with little extra heating from conventional sources required. Excess heat must be used (pool, hot tub, commercial process) or dissipated. Given that about 60 to 80 percent of the average family’s energy use comes from the cost of heating the home and heating water, the savings garnered from an SHW combi-system (and the increase in home resale value) will usually pay the cost of installation within seven to ten years. This is accomplished by reducing your energy bill and your reliance on imported fossil fuels. Over the 30+ years of the system’s life, your SHW combi-system should leave a lot more money in your pocket, compared to conventional heating systems.
There are two main types of solar space heating systems: active and passive. Passive systems (e.g., sunroom) absorb thermal energy from the sun through appropriately-sized and specified windows and store this energy in structures of high thermal mass (wood, tile or masonry floors and walls). The stored energy can then be released into the room space during the night hours, maintaining a more stable temperature environment. Active systems absorb heat through collectors and store the thermal energy in tanks or radiant flooring and panel systems. As shown in the diagram below, active solar hot water systems are made up of collectors, storage tanks, the solar loop (piping, controls, heat exchangers, circulators, gauges, valves, etc.) and heat distribution systems (e.g. radiant floor heating). Thermal collectors, either flat plate evacuated tube or forced air, absorb the thermal energy in sunlight. Generally, the collectors should be south facing (+/- 30 degrees), at a 45-degree angle to the horizon and unshaded from 9 a.m. to 3 p.m. Less than optimal orientation can be compensated for with additional collectors. In a hydronic system, a pump circulates a glycol-water mixture transferring heat energy from the collectors through a heat exchanger to a solar storage tank. Solar storage tanks can range in size from 60 to 120 gallons for domestic use and from 160 to 2,500 gallons for commercial use. In a forced air system, air is heated in collectors and circulated with low-power fans.
Frequently asked questions about combination systems include:
1. How much space is required for collectors in order to adequately heat my house?
2. What are other options for getting rid of excess hot water in the summertime?
3. Will my system be technologically obsolete within a few years?
4. What maintenance is required?
To learn more about space heating, contact us.
