Electricity + Control August 2017

TEMPERATURE MEASUREMENT

Conclusion The ATES system has completely fulfilled expec- tations as the highly rewarding crown jewel of the Crowne Plaza Copenhagen Towers’ envi- ronmentally friendly smart HVAC system, and the savings have long ago repaid the initial in- vestment.

age of heated and cold water respectively. This was achieved by two stages of drilling to a depth of 110 metres at two locations near the hotel. Summer cooling In the summer, cool water from the ground, at 7 - 9˚C, is pumped via one set of wells to the hotel basement, where it is sent through a heat exchanger removing heat from the hotel internal air-conditioning circuit. Then it is pumped back down to a heat reservoir where the heat accumu- lates and is stored during the warmer months. In the air-conditioning circuit, water cooled in the heat exchanger circulates in the building to cool rooms to the desired temperature. This cooling system covers 90% of the total cooling demand with no active refrigeration. Two make- up combined heat-pumps/chillers guarantee suffi- cient cooling capacity in peak-load periods. This part of the process is what results in cool- ing power 40 times the electricity consumed by the installation – impressive savings given that it costs six times more to cool, than to warm water. Variable Speed Drives (VSDs), on fans, pumps and compressors in the entire system play a crucial role in achieving such outstanding energy efficiency. Winter heating In winter, water from the underground reservoir, which has accumulated heat during the summer period, is pumped through the heat exchanger and back down to the wells. In the heating circuit, wa- ter heated via the heat exchanger is sent through the two heat pumps which further raise the tem- perature to 55˚C. This heated water is then circu- lated to warm up hotel rooms and offices. High efficiency at part load is key Inside the building, ac drives ensure good control of the heat pump compressor. The two GEA Gren- co heat pumps have a combined heat pump perfor- mance of 2 400 kW and are fitted with -controlled screw compressors, which enable the system to adjust the heat capacity continuously from low to full performance, with an optimum efficiency. VLT drives ensure good control of pump func- tion for water circulation to and from the natural groundwater aquifer. All ground water pumps are controlled by ac drives in the form of VLT HVAC Drive FC 102. VSDs are essential for significant savings and enhanced functionality for the pumps that propel heat around the hotel’s internal heating and air conditioning systems.

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Jesper Thurbo is Global Director, HVAC at Danfoss Drives A/S.

sargentr@danfoss.com Jesper.Therbo@danfoss.com www.danfoss.com