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Solar Process Space Heating and Cooling

Residential properties are often ideal locations for PV, solar hot water, passive heating, and daylighting technologies but are typically impractical for other renewable applications.  Large commercial and industrial buildings have the additional advantage of being able to utilise further technologies such as: ventilation air preheating, solar process space heating, and solar cooling.

Often large buildings will need a ventilation system as a requirement to maintain indoor air quality.  Heating this air in a cold climate will likely require large amounts of energy.  A solar ventilation system, however, can preheat the air thus saving energy and cost.  A system design capable of doing this may, for example, incorporate a transpired collector.  This type of collector is essentially a thin, metal panel (usually black) typically mounted on a south-facing wall and thus ideally positioned to directly absorb the Sun’s heat.  With many small holes distributed throughout the panel, air can pass through the collector and enter a space in which the air streams can mix together.  This air, now heated, is then drawn into the building’s ventilation system.

Dealing with large commercial buildings provides an ideal opportunity to install solar water heating systems on a large scale.  The basic principles are similar to that used on a residential property but designed to a bigger capacity.  A typical system will consist of solar collectors, a pump, heat exchanger, and large water storage tanks.  Evacuated-tube collectors and linear concentrators are two of the common types of collectors used. These can operate at high temperatures with high efficiency.  Linear concentrators are built with long, rectangular, u-shaped mirrors angled to focus sunlight onto tubes running the length of the mirrors.  Fluid within these tubes is then heated up by the concentrated sunlight.  The heated fluid then feeds the hot water system. N.B. The principles of how an evacuated-tube functions is described in the Solar Hot Water section of this website.

It may at first appear contradictory, but it is also possible to use the heat from a solar collector to actually cool a building.  To understand this concept we must consider the solar heat as an energy source used to drive Thermally Activated Cooling Systems (TACS). These systems exploit the endothermic results of chemical reactions.  Examples of such TACS include solar absorption systems and solar desiccant systems. A solar absorption system uses thermal energy to evaporate a refrigerant fluid which in turn cools the air.  Solar desiccant systems , however, use the solar thermal energy to regenerate desiccants that dry and thus cool the air.  The initial high cost incurred by these TACS can deter deployment and thus their use is currently not widespread.