Since solar hot water systems come in a wide variety of designs, your renewable energy contractor will determine which type of collector, circulation system, storage tank and backup system to use to meet your solar hot water needs.
Solar collectors – the background
Solar collectors – Solar hot water works by first absorbing the sunlight and converting it to heat using a solar collector. Your renewable energy contractor will evaluate your site to determine if adequate sunlight is available. Your solar collectors should be mounted on a site that receives ample, unobstructed sunlight throughout the year. Solar water heating is one of the most efficient solar technologies when used in the proper location.
Active Solar Water Heating Systems – Active systems are the most common solar water circulation systems used. These systems use electric pumps to efficiently circulate fluids through the collectors and into the tank. Since active systems storage tanks do not need to be installed above or close to the solar collectors, they are a good choice for colder climates.
Passive Solar Water Heating Systems – Passive systems do not use a pump to circulate fluids but use natural convection or gravity. Typically they may not be as efficient as active systems but they are less expensive and tend to last longer. Passive systems work well in warm climates.
Storage Tanks – Your renewable energy contractor will estimate the required tank size to meet your hot water needs. Most solar hot water systems incorporate a well-insulated storage tank so the hot water can last for a few days. An 80 gallon storage tank is usually sufficient for 3 or 4 people.
Backup system – Solar hot water systems typically supply up to 80% of hot water needs. During summer months, the system may provide almost all hot water needs. When there is less solar energy available in the winter or on cloudy days, a backup system using gas, electric or solar photovoltaic panels supplements hot water supply.