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Solar Water Heating and Tankless Water Heater

How does a Solar Water Heating system work a Tankless Water Heater? First let us a take a look at how solar hot water heating works.

In general there are solar collectors that capture the sun's heat and transfer it to some liquid medium. That liquid medium can be the hot water used later or a special liquid that transfers the heat through a heat exchanger to the water, warming it.

The solar collectors can be made from different materials. Copper and Glass are common. If you look at your car's radiator you'll see fins attached to a series of pipes. Here the engine's heat is transferred through antifreeze or water to the radiator. The radiator will then RADIATE the heat to the surroundings and therefore cooling the engine's cooling fluid. The fins provide added physical radiation area for faster cooling and smaller radiator.

Now, Solar Water Heating works just like that, only the process is reversed. The fins or other surface expanding area is used to capture the sun's heat and heat the water or some other fluid.

All solar water heating systems have a storage tank and circulation system. The water is heated in the solar panels and then stored in a storage tank that looks like the regular storage water heater tank. The solar tank is much better insulated and retains the heat better since it doesn't have a venting flue like the traditional tank.

In a direct solar system the water in the storage tank is then circulated through the panels to be heated when exposed to the sun and return to the tank again. This system can work without a pump or with a pump, depending on the system's design.

A temperature controlled mixing valve will then mix the water from the tank with fresh cold water to get the desired water temperature that is set to. There are various safety components to control the water pressure and temperature in the panels and the tank and prevent over heating of the components.

Combined with Tankless Water Heater

The tankless water heater's computer always measures the incoming fresh cold water temperature and adjusts its gas burner's so the set hot water temperature can be achieved. The measurement of the outgoing heated water and the incoming water happens many hundred times a minute. The computer then regulates the gas supply to the burner and measures the burner's efficiency and regulates the oxygen for optimum combustion.

The incoming water to the tankless water heater can be of any temperature, almost. The computer can normally vary the combustion from approx. 5% to 100%. A simple example without consideration of water volume is if the hot water temperature is set to 120 deg. F and the incoming water temperature is at 60 deg. F the combustion would be set for 100%. If the incoming water temperature is 120 deg. F then the combustion is set to 0% and the burner would not be fired up. The tankless water heater is able to "pass through" the incoming water if it is approx. equal to its set hot water temperature but it CANNOT cool the water.

A solar water heating system can easily be used with a tankless water heater. It is one of the most economical ways of heating water. The outgoing heated water supply of a solar heating system can be the incoming water supply of the tankless water heater. Anytime the water is below the desired hot water temperature the tankless water heater would heat it to the set temperature and if already at that temperature it would simply "pass through" the hot water.

If such a system is designed and sized properly it can be run with a small tankless water heater that will act only as an auxiliary heater  to the solar system during cloudy days and be very cost effective and energy saving.

About the Author

Al Sagafi has extensive engineering and field experience in energy conservation and renewable energy production. He is actively involved at http://www.JustTankless.com and http://www.allied-solar.com. He holds California State General Building and Electrical Contractor licenses.

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