M&V Solar Water Heating Guideline - Eskom

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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1 3.3.2 Evaluation of LPSWHS in respect of Installation Site Location and Climatic /Seasonal variations In order to evaluate the LPSWHS performance and to report it for each month of the year, a monthly assessment of the energy (hot water) output is necessary. This Guideline employs a weather simulation software Meteonorm ®. The software simulates the weather information for the different locations in South Africa and generates the necessary hourly profiles for the incoming solar radiation, ambient temperature for each day of the year. This information is incorporated into the Performance Model (PM) of the LPSWHS and the its performance is evaluated and reported as per ESKOM EA’s requirements. 3.4 High Pressure and Low Pressure Solar Water Heaters Essentially, high and low-pressure solar water heating systems have a similar design and work on the same principles. However, the differences between the two are the pressures under which they operate in their normal cycle. 3.4.1 High Pressure Solar Water Heaters High-pressure SWH are connected directly to the consumer’s water supply (mains) thus developing a very high internal tank pressure (in the region of 600kpa). This pressure is the main force that drives the water through the pipes resulting in high water pressure and flow from the taps, thus providing the desired hot water service level. In South Africa, as a rule the high-pressure SWH systems have an electric back-up element. A schematic basic drawing illustrating the operation of a High-pressure indirect thermo siphon SWH system is shown in Figure 9. A high-pressure system is required to be equipped with a number of protection and safety equipment in compliancy of the following standards SANS 60335-2-21 part2 (Electrical requirements), SANS198 (Functional control and safety valves for pressurized hot & cold water supply systems) & SANS 0254 The installation of fixed electric storage heating systems and SANS0142 code of practice the wiring of premises. [5] 14
Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1 Figure 8: Principle of operation of a High-pressure indirect thermo siphon SWH system 3.4.2 Low Pressure Solar Water Heaters Low-pressure solar water heating systems in contrast to the High-pressure SWHs cannot tolerate the high pressures associated with their high-pressure counterparts and therefore have to be connected indirectly to the water supply through an additional system such as auxiliary (small) tanks that avoids the pressure rise in their main hot water storage tank. Basically, only limited pressure builds up in the low-pressure SWHs systems. Low-pressure solar water heating systems utilize the gravity to supply water through the piping system resulting in lower water pressures and associated low flows from the hot water outlets (taps). The principle of operation of a system employing an evacuate d tube solar collector is shown in Figure 10 and Figure 11. 15
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M&V Solar Water Heating Guideline - Eskom

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