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Solution: |
The necessary energy is taken from the wastewater of a nearby sewage plant, constituting an energy source with a potential of 266 million kWh waste heat per year. The refrigerating capacity of the heat pumps is 4.3 MW, with a heating capacity of 5.6 MW at 62°C outlet temperature. Around 50% of the heat energy is taken from the treated wastewater from the sewage plant, with another 30% from the waste heat emitted by the building and the technical systems. If no room heat is needed, the waste heat from the refrigerating machine is cooled down again using the treated wastewater. This applies particularly in the summer, when the many automated letter sorting systems demand an increased cooling load of 4.9 MW.
The whole ammonia system is installed in a plant room of around 70 m². Three Sabroe reciprocating compressors are used for first-stage refrigeration at an evaporation temperature of 5°C and a condensation temperature of 30°C. In heat pump mode, five Sabroe high-pressure reciprocating compressors compress the ammonia and generate a temperature of 65°C. The high-pressure liquid is supercooled and expanded in two stages via the intermediate pressure vessel. The coefficient of performance (COP) in the heating phase was calculated at 4 without supercooler.
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