On Location: Crowne Plaza Copenhagen Towers — the world’s greenest hotel

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Smoke ‘em if you got ‘em. Or something to that effect. The new Crowne Plaza Copenhagen Towers, one of the greenest hotels in the world, sits on a natural aquifer in which the hotel “mines” for a sustainable passive HVAC system, a similar methodology to geothermal here in the States.


“In order for energy consumption and CO2 emissions to be as low as possible, the hotel insisted on the most innovative energy technology throughout the building,” says Jens Norgaard, application manager for Grundfos Commercial Building Services. With the aid of  one of the most advanced ATES (Aquifer Thermal Energy Storage) systems, cold groundwater is used for the cooling of the guest rooms in the summer. Conversely, the heat rejected from this process is reused for heating in the winter.


Combined with the building’s variable airflow volume (VAV) ventilation system, the hotel is ensured that guest rooms, lobby and conference facilities are cooled, heated and ventilated individually, and in accordance with the actual load. The system delivers 4.1 MW of cooling and 2.4 MW of heating.


The ATES system delivers cooling and heating system represents one of Denmark’s first groundwater-based cooling and heating systems, and its total annual energy is 51 kWh per square meter for heating, air conditioning, domestic hot water and ventilation. The system has a projected payback of approximately six to seven years.


Ground water from a 46 F cold well is circulated through a heat exchanger that cools water in the hydronic air-conditioning system. In the process, the groundwater is heated and returned to a warm well in the aquifer. The warm well and the surrounding groundwater heats up to approximately 60 F during the cooling season.

During this process, no active refrigeration is required, and the COP is as high as 41. The “free cooling” process covers up to 60% of the building’s total cooling need. Two ammonia chillers remain on standby to cover peak loads between 60% and 100%. Heat rejected from the chiller’s condenser is stored in the warm groundwater well. By reversing the flow, the warm groundwater is available for heating during the winter season.


Jens Norgaard gives a media presentation and tour at the hotel.

Groundwater pumps and all other pumps, both in the ATES system and in the hydronic air conditioning and heating systems, are provided with frequency converters in order to let the pumps adapt to variations in flow requirements.

Grundfos delivered all pumps for the building’s air conditioning, heating and water boosting. The following products were supplied specifically for the ATES system:

• 3 pcs. NB 65 200/129 end-suction pumps w/external frequency converters — primary hydronic heating pumps.

• 3 pcs. NB 125 315/290 end-suction pumps w/external frequency converters — primary hydronic cooling pumps.

• 2 pcs. NBE 65 250/254 end-suction pumps w/internal frequency converters — dedicated to the chiller’s condenser circuits.

• 2 pcs. NBE 100 200/195 end-suction pumps w/internal frequency converters— dedicated for the chiller’s condenser circuits.

• 1 TPE 80 340/4 inline pump  w/internal frequency converter — serves primary cooling tower circuit.

• 1 TPE 80 370/4 inline pump w/internal frequency converter  —serves secondary cooling tower circuit.

All sun-facing facades are equipped with ultra-thin solar panels, and the installation constitutes Northern Europe’s largest private array of solar cells, producing annually more than 200 kWh. This constitutes around 15% of the hotel’s annual power consumption. The total solar cell capacity is 270 kWh. The remaining 85% is bought as green energy produced by wind turbines.

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