IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask A Report, November 2009
Advantages
• No parasitic (additional electric) energy for hot water preparation.
• Low legionella risk because only a very little volume is kept warm.
• Little space requirement.
• Little effect of the circulation circuit if the circulation return line is connected at the
height that corresponds to the temperature level of the circulation return line
• Little heat losses due to the compact design.
Disadvantages
• Low peak power, therefore depending on comfort requirements, the auxiliary set
temperature must be significantly higher than the domestic hot water set
temperature.
• Depending on details of how the heat exchanger is designed and where in the store it
is located, the minimum temperature in the store that can be reached due to the
incoming mains temperature can be relatively high.
• Scaling problems possible if temperature in heat store exceeds 60°C.
• Maintenance and replacement is almost impossible, depending on the design.
Flat Plate Heat Exchanger Unit
The last step of the development to reduce the volume of DHW (1-2ltr) which is kept warm is
to prepare DHW in the continuous-flow principle by an external flat plate heat exchanger.
Fig. 5: External flat plate heat exchanger unit for DHW (left: SOLVIS, GER/right:
Sonnenkraft, AUT)
Advantages
• Peak power is limited, but the power can easily be adapted using a correctly
designed heat exchanger, depending on the requirements.
• Low return temperature to the heat store.
• Best usage of the stored energy in the tank.
• No scaling problems if flow temperature is limited.
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