Domestic Water Heating

In a conventional water heating system, cold water is fed from the city supply or your well into the gas, oil or electric water heating system where it is heated to about 125 degrees f. Needless to say, this takes a great deal of fossil fuel- either directly in the form of fuel at your boiler, or indirectly by fueling your electric utility’s electric plant.

With your solar hot water system cold water is fed to the solar storage tank installed next to your existing water heating system. A pump circulates a water and antifreeze mixture through the solar collectors where it is heated. The heated fluid is pumped through the heat exchanger which is in the solar hot water tank where it transfers the heat to the domestic hot water for use throughout your home.

This antifreeze is propylene glycol- a harmless compound used in ice cream and soft drinks. The glycol water in the ‘solar loop’ never comes in contact with ‘domestic’ hot water you use around the house.

A benefit of this design is that your available supply of hot water is essentially doubled by the addition of the solar hot water tank. Owners of solar hot water systems almost never run out of hot water.

The control unit continually monitors the temperature of the fluid in the collectors and the temperature in the tank. If the fluid in the collectors is significantly warmer than the water in the tank, the pump circulates the fluid through the collectors.

Your pump switches off automatically when there is insufficient sunlight and the collectors are no longer able to raise the temperature of the water in the storage tank. This happens when the sun is at a very low angle or when there is a thick cloud cover, and at night. The pump automatically starts again when enough sunlight is available. Your solar hot water system is used in conjunction with your existing water heating system, or a with a very efficient ‘on-demand’ water heater. This system will automatically provide back-up during periods of heavy demand or decreased solar hot water production.

Temperatures in your solar storage tank can be as high as 140 degrees F in winter and over 190 degrees F in the summer months. When you turn on a hot water faucet in your home, your water requires no, or very much less heating, to get to your required temperature. Often, the water from the collector is too hot and it is mixed with cold water at a tempering valve to produce the same uniform temperature at the tap or shower that your family is accustomed to.

Space heating

Solar heated water can be used to suppliment existing of new radiant or hydro air space heating systems. Solar hot water is a good match for these heating systems since they  operate with lower temperture water. Baseboard heating uses very hot water and more baseboard heating must be added to work with solar.

As with a domestic hot water system, a solar hot water space heating system uses a 'closed' plumbing loop to transfer heat from the collectors to the storage tank. A space heating system, though, will require more collector area and larger hot water storage capacity. The solar heated water for space heating is 'boiler water' and remains in your heating system.

A solar radiant floor will require a back-up system, just as with the domestic hot water system.

A tempering valve regulates the temperature of the fluid in the loop by adding cold water or additional hot water from the back-up heat source.

Solar space heating systems almost always heat your domestic hot water as well and have a separate storage tank for this purpose. DHW is a year round hot watre use and solar should be used for this whenever possible.

Some designs use an array of solar collectors to heat a pool in the summer, and then heat a radiant floor in the winter.

Swimming Pool Heating

Solar pool heating is a simple process. Only solar collectors and PVC pipes and fittings are needed. The pool itself is used as the storage tank, and in most cases your existing pool pump is used.

Filtered pool water is pumped from your pool to the solar collectors. The heated water is returned to the pool (through the automatic chlorinator or salt water chlorine generator if there is one). The process continues until the pool reaches your chosen temperature.

A roof sensor attached to the collector will detect if there’s enough solar energy to heat the pool; if the pool is below the selected temperature, water will be pumped through the collectors. The process can be automated with the same valves and controls that run a basic pool and spa configuration. A regular, manual, valve may also be used.

The Solar collectors can be much simpler than those used to provide hot water for your house since the required temperature is much lower. For this reason it is still economical to install the relatively large collector area need to heat a pool. As mentioned above, high temperature collectors such as evacuated tubes or flat plates can be used in situations where both a pool in the summer and a radiant floor in the winter need to be heated.

Bright sunshine is not necessary for your system to work. On cloudy days and in hazy conditions there is usually sufficient solar energy for the system to provide the required amount of heat.