Thermal Solar Systems: Passive and Active Solar Design

While photovoltaic solar power is definitely popular due to its ease of installation and connection, anyone considering solar power for their home may want to consider a thermal system. As opposed to photovoltaic panels, which use semiconductor materials to convert solar heat directly into electrical energy, thermal systems use the heat from the sun to heat a particular substance (most commonly, water is the substance, though there are others) and then use that substance to generate electrical energy.

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There are two main types of thermal solar power: passive and active. Passive solar power actually doesn’t really generate electricity at all. It is kept in mind during the design and construction of the house to position it such a way that the sunlight can provide heat to anything that needs it. For example, one might use lots of windows to let the sunlight shine in more areas of the house so that no electric heater is needed. It’s much the same way a car heats up underneath the sun: heat gets in much easier than it gets out. This technique can also be used with hot water systems.

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Active solar systems are the systems that produce electrical energy. While photovoltaic systems are considered active, they are not thermal. The difference between them is that active thermal systems use the heat radiated by the sun to power a turbine, which, in turn, generates electricity. This is done through the use of heat collectors placed on the rooftop. These heat collectors look very similar to the photovoltaic panels, yet not as many are required for thermal systems as are usually needed for a photovoltaic one. Typically, these are placed in a location that maximizes the amount of sunlight that hits it each day. While you want to keep that in mind, be careful not to place it too far off centre or it may end up looking like acne on a house.

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Once these thermal collectors get the heat, it then uses the heat to generate steam or convection currents to power a turbine. The turbine can then generate electrical energy. This is similar to how windmills generate electrical power (the wind turns the blades of a turbine, which generates the electricity). The benefit of a thermal system is that it may be capable of producing AC (alternating current) voltage, whereas photovoltaic systems produce DC (direct current) voltage. Since most household appliances are already designed to run on AC voltage, it saves the need for an inverter to convert DC to AC.

Thermal systems can indeed bear their own benefits. Passive technology, though not really new, should be kept in mind, particularly if designing a new home. This will save on both the electric bill and on the greenhouse gases that would otherwise be emitted. It makes sense why so many are making the change. Will you be next?