Compact Solar Combisystem - High Efficiency by Minimizing Temperatures
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Posting Date | 10 June 2009Publication Date | 2007
Country | Pan European
Geographic Coverage | International
Type of publication | Report
Publisher | DTU, Denmark
Number pages | 172
Source Languages | English
Compact Solar Combisystem - High Efficiency by Minimizing Temperatures
Solar heating systems are getting increasingly popular in many European countries, mainly focused on solar domestic hot water systems. But so-called solar combisystems, which supply heat for both domestic hot water and space heating, are still only really noticable in Sweden, Germany, Switzerland and Austria. Reasons for
that, beside others, might be not sufficiently attractive energy savings, too big space requirement and too much effort and risks for installers due to the complexity of many system concepts and products available on the market. Based on elaborated knowledge in international research projects within IEA-SHC Task 26 and the ALTENER project “Solar Combisystems”, a new solar combisystem concept was developed. Therefore the focus was concentrated on minimizing the temperature in the system with the goal to reduce system heat losses and to increase the efficiency of the condensing natural gas boiler and the solar collector. The major
task was to enable high domestic hot water comfort at any time, independent of the auxiliary set temperature in the solar tank. For a condensing natural gas boiler in combination with a flat plate heat exchanger hot water unit, a hydraulic and control concept could be developed, which ensures the required hot water comfort without the need of high temperature in the solar tank. As a consequence it is possible to use the auxiliary volume in the solar tank at any low temperature level required by the actual space heating demand. This strongly improves the operating conditions for a condensing natural gas boiler and reduces the heat losses of the tank and, most important of all, the pipes within the system. The compactness of the total hydraulic system, which is installed in a closed 60 x 60 cm cabinet as a technical unit, leads to further reduction of heat losses, the possibility to use heat recovery effects, and several practical advantages like attractive appearance, easy transport and simple and fast installation. Due to the concentration of all technical parts in the technical unit, it is possible to combine it easily with standard tanks of any size in order to achieve the requested energy savings. The hydraulic and control concept was designed to be used with great advantage in combination with condensing natural gas boilers, but it can be also combined with pellet-, wood- or oil boilers just by adjusting some control parameters. Theoretical investigations including system simulations with TRNSYS showed for
this new solar combisystem concept a potential of up to 80% more energy savings compared to existing, conventionally controlled solar combisystems. After development and test of the first prototype in the laboratory, a demonstration system was built which replaced an old conventional natural gas heating system in a onefamily house. Measurements in practice showed how this new natural gas - solar heating concept performs in comparison with the old one.
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