Higher heat recovery temperature and lower heat supply temperature result in higher heat capacity & efficiency To get the highest heat pump efficiency, and lower the price of heat, Ringsted DHC needs to recover the heat at the highest temperature possible. The HP02 heat pumps operate at a high heat recovery temperature (51°C> 28°C surplus heat from the straw boiler scrubber), resulting in a high heat capacity of 962kW and a COP of 7.1. HP03, which uses waste heat from HP01, the CHP and from cooling the heat plant room, also runs at a high heat recovery temperature, and as a result has a heat capacity of 310kW and COP of 6.2. The final supply heat temperature is 58C, which is low enough to enable the high efficiency of all three units. HP01, which is challenged by operation with heat recovery from the lower ambient air temperature during the winter months and air-to-refrigerant heat exchanger approach temperature while also supplying a higher heat capacity of 6.829-9.500kW, at a corresponding COP of 3.0-4.1 (depending on outside air temperature). The heat recovery methodology utilized for the Geoclima heat pumps enables improving the overall heat plant COP and heat capacity of the plant (by up to 21% and 31% respectively). Maintaining a balanced temperature and utilizing cooling with resulting recovered heat has also helped to make the plant’s equipment more reliable.
The unique challenges of installing heat pumps at Ringsted DHC For Geoclima and Unicool, who designed and delivered the heat pumps units for Ringsted DHC, one of the biggest challenges was optimizing heat pumps to handle extremely variable temperatures. Condensers had towork from50°C to 67°C, while the evaporator was handling temperatures from 35°C to 21°C – a big step up from the 6/7°C evaporator cooling temperatures compressors work with for comfort cooling. Geoclima also needed to ensure temperature control at a variety of floating water flows, which could drop from 100% at full load, to just 10%. With any vapor compressor, it’s critical for the design to be optimizedto theconditions inwhich itwill operate. ForRingsted DHC’s HP02 and HP03, this required two different optimized compressor designs : a medium- and high-lift version. The medium lift version is the optimal efficiency solution for HP02 units, which consistently supply a heat forward condenser temperature of 57°C. HP03, which is required to periodically supply 67°C hot water temperature incorporates the higher lift-optimized compressor design.
CHANGE (EXCESS HEAT) 4%
HEAT PUMP 45%
SLURRY TANK
AGRICULTURE SUPPLIES STRAW
SOLAR PARK
WINDMILLS
NATURAL GAS
biomethane
35 C SMOKE
HYDRO
EXT. STRAW HEATING WORKS
EXT. CHP
50 KV
95 C
95 C
HALMKEDLER 17.000 KW VARME
GASMOTOR
TRANSFORMER
58 C
10 KV
75 C
72 C
13.000 kWHeat
10 kV
Uses electricity when there is environmentally friendly electricity Produces electricity when the electricity grid lacks power
57,7 C
10 KV
NEW LITTLE HEAT PUMP
31 C
60 C
USED ALL YEAR
0,4 kV
FERTILIZER WATER NPK
0,7 kV
58 C
NEW BIG HEAT PUMP
49 C
95 C
1.000 kW EL
0,7 kV
1.000 kW EL
49 C
Heat ACCUMULATOR 3400 M3 Water
NEW Flue gas cooler
47 C
31 C
NATURAL GAS - USED WHEN NOT WIND, WATER OR SOLAR TO LOW POWER
6.000 kW
49 C
Air 5 C
49 C
95 C
57 C
105 kW
2 C
49 C
8.000 kWHeat
900 kW Heat
53 C
49 C
57 C
49 C
49 C
57 C
57 C
70 C
70 C
ILLUSTRERET/TEGNET AF OLE B. WINTHER/SOFIE MALM
Illustration by Ole B. Winther / Sofie Malm
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