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We trust this manual will give you all the answers to the questions that you might have regarding the products. Although every care was taken to ensure the content of this manual is correct we do not accept any liability for claims resulting directly or indirectly from the application of the information contained in this manual. This manual is written specifically for the Dimples Solar product range. Any information contained therein must not be applied generally to any other solar products. Should you require any further assistance please do not hesitate to contact us. 3 Solar thermal 3.1 Introduction The sun supplies every day a multiple of the required world wide daily energy demand to the earth. The energy of the sun is available in various forms such as: -direct, diffuse and reflected solar radiation - wind - waves -the ground and in other forms. Solar thermal systems convert the energy incident from the sun on an absorber surface into sensible heat in form of hot water. Depending on the temperature required and achieved, this hot water can be used for a whole range of applications as summarised in Figure 1. Figure 1 – Approximate temperature ranges of some solar thermal applications 3.2 Solar radiation 3.1.1 Available solar radiation Solar thermal systems can only utilise the energy from the sun in form of solar radiation. The solar radiation can be incident on the solar panels in various forms which are shown Page 4 of 72 ST0133 – A 02/09 Technical manual SOLAR in Figure 2, namely direct, reflected and diffuse radiation. The various types of radiation can occur in isolation but in most cases the radiation incident on a solar thermal collector is a combination thereof. <1200 W/m. <1000 W/m. <600 W/m. <200 W/m. direct + reflected direct diffuse strong diffuse Figure 2 – Forms of incident solar radiation The solar radiation available outside the earth’s atmosphere, the so called extraterrestrial radiation, has a density of 1367 W/m.. Depending on: -the location of the solar system -the time of day and year -the “obstacles” in the atmosphere such as cloud cover and pollution -and the inclination of the solar system in relation to the sun this value varies strongly. A map of the United Kingdom and Ireland is shown in Figure 3, indicating average annual solar energy gains on the horizontal surface. Page 5 of 72 ST0133 – A 02/09 Technical manual SOLAR Figure 3 – UK and Ireland irradiation map (horizontal surface) 3.1.2 Orientation The solar irradiance shown in Figure 3 is an average value incident on the horizontal surface. As mentioned above, depending on the orientation and inclination of the solar collector the incident radiation onto the collector surface can vary although it might be in the same location. The terminology used to describe the exact location and orientation of a solar collector is described in Figure 4. The terms indicate: -longitude: geographic coordinate for East/West measurement -latitude: geographic coordinate North or South of the equator -slope: angle between the horizontal and the collector plane -azimuth: angle between South and the perpendicular to the collector pane (West +90°, South =0°, East -90°) Page 6 of 72 ST0133 – A 02/09 Technical manual SOLAR Latitude Longitude S W N E Zenith Slope Azimuth S U N Figure 4 – Terminology to describe location and orientation of solar thermal panel Figure 5 – Effect of orientation on incident radiation levels Page 7 of 72 ST0133 – A 02/09 Technical manual SOLAR Although the location of the solar thermal system can be described using the longitude and latitude of the installation, in practise the locality is being used to determine the location of the system. The effect of the orientation on the incident solar radiation levels can be seen from Figure 5. 3.3 Solar thermal system 3.3.1 Components of a solar thermal system Although solar thermal systems cover a whole range of applications, see Figure 1, the basic components used are in principle the same. A solar thermal system consists of: - solar collector -heat transfer medium - pipe work -pump and safety equipment - heat exchanger - storage facility - control unit - user Applying the above to a domestic hot water system, the individual components are identified in Figure 6. heat transfer medium solar collector pipe work pump and safety equipment storage cylinder with build in heat exchanger control unit Figure 6 – Solar system components overall view Page 8 of 72 ST0133 – A 02/09 Technical manual SOLAR Each component in the solar thermal system fulfils a specific function which is described below: Solar thermal collector The solar thermal collector receives the solar radiation, converts it into thermal energy and passes it on to the heat transfer fluid. Heat transfer fluid The heat transfer fluid circulates through the solar collector, the pipe work and the heat exchanger. It transfers the energy gained by the collector into the storage device. The heat transfer fluid has additional propert...