The main purposes of a HVAC-system are to help maintain good indoor air quality through adequate ventilation and to provide thermal comfort.
Cooling or heat rejection of air-conditioning systems is based on thermodynamic principles and involves heat transfer between fluids. Heat generated from the process is released to the environment. According to the different cooling medium of condenser, air-conditioning system can be divided into two categories, namely air-cooled and water-cooled system. In general, water-cooled air-conditioning systems have a higher COP (Coefficient of Performance) than air-cooled air-conditioning system and thus provide energy savings.
The condenser cooling system in a water-cooled air-conditioning system can be of different types; cooling tower or liquid-cooled air cooler. If the building site is situated near seawater, seawater cooled condenser cooling offers substantial energy savings of up to 30%.
A conventional air-conditioning system is design for production of 6/12°C cooling water for use in ventilation cooling surfaces. When the seawater is cold enough (below 5.5°C) the system can operate in free cooling mode i.e. generation of cooling is maintained without the use of the cooling machine. The seawater is directly pumped to a seawater plate heat exchanger and used to cool the cooling water. The free cooling system is highly energy-efficient since only the seawater pumps are running and not the compressors.
When the seawater temperature is between 5.5°C and 11.5°C, the seawater plate heat exchanger is used for precooling of the cooling water, before it’s cooled by a compressor chiller system to the desired temperature. The seawater is then used to cool the refrigerant in the condenser. When the seawater temperature is above 11.5°C, the seawater is too warm to be used for free cooling, and the chillers provide all cooling.
In order to protect the seawater plate heat exchanger from fouling and clogging, the Bernoulli Filter is vital component in a seawater cooled HVAC-system to provide particle free seawater.
Case story: Copenhagen Opera House
In August 2000, the A.P. Møller and Chastine Mc-Kinney Møller Foundation donated an opera house to the Danish state. The Opera building was designed by the internationally known architect Henning Larsen. The Opera House is located right up to the waterfront on the island of Holmen - specifically called the Dock Island, in Copenhagen Harbour. The Opera opened with a Royal Command Performance on 15 January 2005.
The Opera building is totally 41,000 m2 - and has more than 1000 rooms including a sound proof rehearsal auditorium for the orchestra. The Opera has 6 main stages- one main stage with five other stages directly connected - where large productions and setups can be changed with various decorations and easily moved around when needed. The Opera House can seat between 1490 and 1700 guests depending of the stage setup and size of orchestra to obtain the optimal performance.
The indoor climate of the Opera House is controlled by a seawater cooled HVAC-system. The HVAC-system is based on free cooling and compressor-based cooling using ammonia, R717, as refrigerant.
When the seawater from Öresund is cold enough the cooling is based solely on free cooling which generates great energy-savings in terms of lack of compressors. The seawater is pumped by the seawater pumps and passes through Bernoulli Filters, 3 x BSG 150, before entering the seawater plate heat exchanger to cool the cooling water. The Bernoulli Filters protect the seawater plate heat exchanger from getting clogged up by dirt or organic growth from the seawater.
When the seawater is too warm to be used in free cooling, the seawater is used for condenser cooling in the chiller system.
Facts and figures
Customer: Copenhagen Opera House
Application: Seawater cooled HVAC
Filter model: 3 x BSG 150
Filtration: 1,0 mm
Operating flow: 3 x 160 m3/h
Operating pressure: 2 bar g
Design pressure: 10 bar g