Heating water with the sun can be accomplished in a number of ways. In areas where the temperature drops below freezing, solar domestic hot water (DHW) systems typically use flat plate collectors with an antifreeze solution to avoid problems with freezing.

The collectors are usually mounted on a south-facing roof and tilted at an angle that depends on the latitude and design of the system. The latitude of the Chippewa Valley is approximately 45°N. To take best advantage of winter and summer sun angles, the panels are usually elevated to 45° from horizontal in our region. A non-toxic antifreeze solution cirulates through insulated tubing from the collectors to a heat exchanger, where the heat is transferred to a water storage tank. A controller activates a circulating pump to bring hot fluid from the collectors to the heat exchanger whenever the panels are warmer that the water in the storage tank. The circulating pump is powered by a small solar electric panel or by connecting to the home electrical system. The solar powered system does not require a controller because the circulating pump only comes on when the sun is shining and conditions are right for heating water. Hot water from the storage tank can be fed into an existing water heater or plumbed to bypass an existing water heater to go directly into the hot water piping.

With this system design, the existing hot water system can act as a backup hot water source for times when there is little sunshine. A better backup system is an instantaneous (tankless) water heater that only comes on when the solar heated water isn't hot enough. These tankless units have the added benefit of higher efficiency compared with convertional gas or electric water heaters, and they produce a constant source of hot water that never runs out.

Typical System Costs

A solar DHW system for a typical home is comprised of 2 flat plate collectors (4 ft x 8 ft) and an 80 gallon water storage tank connected to the existing water heater. Depending on the hot water usage of the household, the solar DHW system could produce up to 60% or more of the annual hot water needs, providing a significant savings in operating costs.

We also install systems that incorporate instantaneous (tankless) water heaters for backup water heating. The tankless water heater would replace an existing conventional gas or electric water heater.

For more details on solar DHW design, please look over the schematic of a typical system. We can schedule a site assessment to determine the suitablility of a solar DHW system at your home. Please contact us for more information.