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Hotel employs latest tech to cut energy use

The new Crowne Plaza Copenhagen Towers features state-of-the-art energy technology throughout.

One of its most significant features is an innovative ground water cooling system that supplies the heating and air conditioning for 366 guest rooms, conference rooms, kitchen, restaurant and offices in an adjoining wing.

The building is also equipped with 2,500 specially adapted solar cell panels mounted on three of the hotel’s four facades, designed to provide about 15 per cent of the building’s annual electricity requirements. The installation constitutes Denmark’s largest private array of solar cells, producing 200 GWh per year. Both systems are equipped with Danfoss VLT frequency converters and TripleLynx solar inverters.

The ground water cooling system required two lots of drilling to a depth of 110 m at two locations near the hotel. In the summer, cool water from the ground (at 7 to 9 deg C) is pumped through a heat exchanger, then to a heat reservoir where the heat is stored during the warmer months.

The cooled water from the heat exchanger is circulated to cool rooms so that no active refrigeration is required, resulting in a COP (coefficient of performance) as high as 40.

In winter, water from the reservoir, which accumulates heat during the summer period, is pumped through the heat exchanger and back down to the wells. Heat from the heat exchanger is sent through two heat pumps, which raise the temperature to 55 deg C to heat hotel rooms and offices.

“The combination of ground water cooling and heat pumps is an innovative solution,” says Copenhagen Towers’ property director Peter Andersen.

“It allows us to recycle heat from the summer months and use it during the cold winter months.” The installation represents Denmark’s first ground water-based cooling and heating system and is predicted to save up to 90 per cent of the hotel’s heating and air conditioning energy consumption.

Smart heat pumps

The two GEA Grenco heat pumps have a combined performance of 2.4 MW and are fitted with frequency converter controlled screw compressors, which enable the pumps to adjust the heat capacity continuously from low to full performance, with the same efficiency.

Heat pumps do not always run at full capacity and it is therefore important for energy consumption that efficiency is high, irrespective of whether the system is working at full or half capacity.

All ground water pumps have VLT frequency converters. Speed control of the pumps that propel heat around the hotel’s internal heating and air conditioning systems is also performed by frequency converters. These are designed to help ensure good capacity control and afford superlative energy savings for the pump system.

The solar cell panels mounted on the hotel’s facades are currently the largest installation of their kind in northern Europe. Each of the Crowne Plaza’s south-facing facades is covered with ultra-thin, high-tech solar cells.

These generate approximately 170,000 kWh per year, roughly 15 per cent of the electricity consumption of the hotel. The hotel buys the remaining 85 per cent in the form of green energy produced by wind turbines from DONG Energy.

As the country’s first hotel to register under the UN Global Compact, Copenhagen Towers is a leading light in Denmark’s drive for sustainable construction.