Uses of Solar Thermal Energy in Solar Heating and Cooling
Residential and commercial users generally install low solar thermal collectors as a heating facility for swimming pools. A simple solar thermal heater can be composed of a series of black painted pipes layered in an insulated box and framed with glass, plastic, or metal panels. Potable water runs through these collectors and into the storage tank. Potable water can be cycled several times into the collectors and back to the tank again to increase water temperature.
The thermosyphon system uses this configuration. The tank is placed above the collectors and takes advantage of the hot water’s natural tendency to rise above cold water. As hot water is drawn out for use, untreated potable water is fed through the collector.
Water tanks under the collector need an electric pump to drive the water inside the collector. Such a system needs an anti-freeze or anti-corrosive chemical to treat the circulating fluid. A heat transfer fluid is also required to heat the end-users water supply.
Space Heating and Cooling
Low temperature collectors are also use for space heating. This is necessary in colder parts of the world, especially during winter season. Huge quantity of electricity is needed and if the building is well designed for solar insolation, a building can be cost and fuel-efficient and can provide a comfortable habitat.
A simple solar space heating configuration is the installation of a Trombe wall. This is an enormous black painted wall and has a double-glazed skin to prevent the sun’s heat from escaping. UTC or unglazed transpired collectors are perforated sun-facing walls used for pre-heating ventilation. Transpired collectors’ short payback period of 3 to 12 years makes it a cost-effective alternative to Trombe wall and other glazed collector systems.
Space cooling is not as technical as space heating and can be done through natural methods like planting deciduous trees. The leaves serve as shade during summer and its branches and limbs let the warmth of light pass through during winter. Other cooling solutions include installation of dome roofs and thermally massive structures, shaded windows, and bamboo structures. For mechanical space cooling methods, use of absorption refrigeration cycles and desiccant cycles are proven methods to promote a cooler space.
This technology has been used for years in developing countries. A solar cooker is composed of wooden box lined with insulation and covered with a reflector. The reflector concentrates the heat of the sun to the pots, which are painted black to maximize heat absorption. The cooking time is relatively slower but is compensated by the lack of fuel cost. This cooking method is normally used in regions with strong and sufficient sunlight.
The Scheffler solar cooker configuration is much like concentrated solar power (CSP) as it uses a parabolic dish with a single axis tracking the course of the sun throughout the day. Since the reflector system has a focal point, it can reach high temperatures, allowing faster cooking time. Larger Scheffler solar cookers have been in production since 2008.
Solar thermal energy can be used to dry crops, woods, and food products like grains, fruits, and fish. Solar drying is a low cost solar thermal technology that uses transpired plate air collectors that are based on black materials or fabric. It is also environmentally friendly and improves the quality of the crops with minimal cost.
Solar Water Distillation
This is useful in regions where clean water is not always available. Solar thermal collectors heat the potable water where it evaporates and condenses at the bottom of the covering glass.