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Solar Thermal

Domestic Hot Water (DHW) Systems

Solar thermal information is listed on our website for your reference. We are not available to advise, supply nor install solar thermal systems. Please contact a professional plumber in your area who can advise you on that technology.

Over a horsepower of energy per square yard falls on your roof on a sunny day. You can capture this energy to heat your domestic hot water using a number of different methods.

If your motivation is to use alternative energy to save money on your fuel costs, this is the first place to start. There are many possible ways to use solar hot water. In general, anything that requires water to be heated can benefit from solar energy. Some projects make sense, some do not. Pool heating and domestic hot water are the most common uses of solar thermal and offer the most appealing return on investment.

In a solar hot water system, heat from the sun is transferred directly to water or a glycol mixture circulating in a collector. There are two types of circulating systems in common use: the open-loop and the closed-loop.

A closed-loop system circulates a water and glycol mixture through the collector, where it absorbs heat. It then passes through a heat exchanger, where it transfers the heat to the water in a storage tank or a pre-heat hot water tank. The pre-heat tank becomes the cold water supply for an existing domestic hot water tank.

There is no need to drain a closed-loop system in the winter because the glycol mixture does not freeze, so total hot water production will be higher than with an open-loop system. If your home is already equipped with an electric or gas-fired hot water heater, a closed-loop hot water heater will work the best.

An open-loop system circulates the solar heated water directly into the hot water tank. Customers who use a wood stove with a water jacket in the winter may easily add a solar collector to use the sun for hot water in the summer. This system is the simplest to install, but it must be drained in freezing weather.

Thermosiphon or Pump
A thermosiphon occurs when the hot water tank is located above the collector. Heated fluid has a lower density than cold fluid. Natural convection causes the heated liquid to flow into the water tank. This system is most similar to the hot water coil found in many wood or oil stoves and requires no circulation pump.

A thermosiphon system is often not practical especially if you want your collectors mounted on the roof. This configuration requires a circulation pump in the system. This type of pump draws very little energy and is often powered by a small solar electric module. When the sun is shining, it is heating and pumping water. A solar electric powered circulating pump means no complicated differential controllers are required.

There are many different collectors used in solar domestic hot water (SDHW) systems. The most common is the flat plate grid collector. This is a series of pipes connected to a top and bottom manifold. These collectors are usually glazed and insulated. Typically a 4 ft x 10 ft (1.2 m x 3 m) collector will produce as much energy in full sunlight as a 2kW hot water tank element.

The simplest and least costly form of circulating heater is a rubber tube mat connected between two header pipes. These collectors are unglazed and uninsulated. They are usually used for swimming pool heating but are also used seasonally for domestic hot water. These are the least efficient form of water heater and the least expensive.

No form of solar hot water heating will be 100% effective in the Canadian climate. For cloudy periods a backup water heating system is required. If you have an existing electric or natural gas hot water tank or wood stove, your backup is in place. Solar water heaters may be used for space heating. In space heating systems the solar heated water circulates through a radiator or pipes laid in the floor of the area to be heated.



An Introduction to Solar Water Heating Systems
Solar energy is a clean and abundant energy resource that can be used to supplement many of your energy needs. Solar energy can be utilized as a form of heat, such as solar water heating, and as electricity, such as solar photovoltaics.

A buyer's guide to Solar hot Water Heating Systems

Heating your building with Solar Energy
A simple technology can dramatically reduce fuel consumption and heating costs, particularly for buildings with a high demand for fresh air. The concept: use solar energy to preheat outside air before it is introduced into a plant or other facility. The warmed air can be distributed as is, further heated in a building's primary heating system or used as combustion air for industrial furnaces.


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