- Renewable & Alternative Energy
Solar Thermal Energy: How Sunlight Is Exploited For Affordable Home Heating And Constant Hot Water Supply
Long before solar panel arrays were used to convert solar energy to electricity for domestic applications, people had found ways to utilize solar energy to produce heat. Ever since the ancient years, people knew that placing a container with water on direct sunlight would cause its temperature to increase. They actually used the knowledge they had acquired everyday; in spring, summer or days with much sunlight, women would take advantage of solar energy in cooking or clothes washing. At those years, many women would save up on firewood, since they could cook meals in homemade solar "ovens" when sun was shining much.
In more recent years, people have been using water tanks/boilers which can heat water for house needs (for example for showers) through collectors which attract and enhance the energy.
Solar thermal energy is a sub-category of active solar systems and is the technology that exploits solar energy in order to produce heat. This heat can be manipulated to contribute to a residence heating system, thus decreasing its needs for fuel or electricity derived heating systems. In typical residence applications, water is the basic medium which is used for heat transfer; in standard, non-solar energy systems, water is heated through burning fuels or gas, circulates to radiators in the rooms or transferred below the floor (floor heating systems).
The same idea can be followed, with more than acceptable results with solar energy. Depending on the facility, water can be heated through a specialized solar heating system, after which it can follow the same route to radiators. In regions which have many days of sunlight even in colder seasons, such as in winter, the efficiency of such solar thermal systems is very high and such installation can offer significant decrease on residence heating costs. However, even in regions with less amount of sunlight throughout the year, solar thermal systems are developed and under use with great success.
The basic principle of a solar thermal system is that its installation aids and contributes to house heating while fuels systems are used simultaneously. The fraction of solar thermal contribution to the residence needs and of course the reduction of fuel consumption are relevant to the amount of solar radiation in the region where the system is utilized (thus the geographical location), the size of the system and its particular characteristics and other factors. As experienced in certain solar thermal systems in South Europe and the Mediterranean, such system can supply the whole thermal needs of a typical household. In Northern countries, there will be need for additional systems, but their use will be limited and the cost will be kept low. In floor heating systems, even with little sunshine there can be a large impact on the environment and a serious drop of house heating expenses.
In days of no sunlight, the system is able to monitor the temperatures of its buffer tank, which is an inactive container of water; when the temperature of that water is below the setpoint limit (set by the manufacturer of the system) an auxiliary heating system, usually the one used as conventional house heating, is turned on. The solar reservoir actually includes two heat exchangers - one coming from the collector and the second is connected to a heating boiler. If there is no need for hot water in the residence, the reservoir is able to keep the water warm for several days, depending of course on the weather and size of the system. Residences with proper insulation will have magnificent results with a solar thermal system, because there will be less energy losses.
The main parts composing a solar thermal system are:
- Solar panels, collectors
- Plumbing equipment and the relative mounting hardware
- Buffer tank
- Solar Station
- Controller-Automation Systems
Installation And Costs
A solar heating system can be installed at any stage of a house construction. The best results will be obtained when the house itself has been built to incorporate low energy emission standards; that means, a well insulated construction with windows facing the South and less energy losses from the roofing and walls. Nevertheless, the installation can be completed even when a house has been constructed already, because it requires no modification to existing heating systems.
Solar panels are used to collect the solar energy, ensuring high absorption and consequently a larger contribution to the heating needs of the residence. Collectors are typically placed on the roof, at a spot which is not shadowed by other constructions or trees, and preferably at a spot where the roof will be able to support its weight and which will be convenient for the plumbing connections. A standard collector is a rectangular, flat plate which contains small tubes carrying water or other fluids (some carry anti-freeze solutions). Those tubes are mounted on a metal absorber plate, painted black to achieve higher sun rays absorption. The back and sides of the collector are properly insulated to make sure there are no energy or heat losses at this initial part of the system. The water/fluid passing through the tubes is heated.
The cost of a solar thermal system installation varies on many factors; the plant size, the purposed reduction in fuel consumption, the size of the house and the number of residents, and the quality/origins of the relative equipment. A high quality system coming from a respected manufacturer will cost more, but will be guaranteed against failures for longer and will be able to achieve higher performance throughout the year and for many years to come.
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