In the beginning of 2020, Aalborg CSP A/S, a Danish renewable energy and storage specialist, received an order for turnkey delivery of a customized 1.2 MW electrical heat pump system for a Danish district heating plant in Northern Jutland, Denmark. After a successful performance test, which met all requirements and achieved a high COP, the system was in middle of February 2021 handed over to the client. With a capacity of 1.2 MW, the plant is capable of producing approx. 8,000 MWh heat annually, thereby covering approx. 80% of the customers’ heat consumption.

Aalborg CSP received the order from the Danish district heating plant, Saltum Fjernvarme to deliver a 1.2 MW electrical air-to-water heat pump system. The system will help reduce the facility’s natural gas dependency as well as help stabilize the energy prices.

The integrated heat pump system in Saltum is customized to fit the district heating plant’s specific energy need, uses outdoor air as the source for heat production and ensures a more flexible energy supply.

Heat pump system delivers on promises with high COP

After having undergone and passed all performance and reliability tests in the first attempt, the plant has now been handed over to Saltum Fjernvarme, who is responsible for the day-to-day operation of the plant.

Aalborg CSP was selected as turnkey supplier of the system as their solution had the highest COP. COP stands for ‘Coefficient Of Performance’ and is a performance rating indicating the efficiency of a heat pump. When calculating the COP for a heat pump, the heat output is compared to the power supplied.

“Aalborg CSP was selected as turnkey supplier of the system as our solution provided the client with the highest COP and thus the lowest price per produced MWh” - says Per Aasted, sales and project engineer at Aalborg CSP and adds “We are happy that after a successful test phase it has been established that our plant delivers as promised. We know that it is not always the situation as heat pumps are relatively complicated piece of machinery that includes high pressure, steam and liquids which all have to be balanced. For that reason, I am extremely proud of the work that has been carried out.”

When building integrated energy systems such as the heat pump in Saltum, it is very important to obtain the maximum performance and the best possible return of investment for the local community. The COP of a heat pump plant can be calculated in a number of different ways and comparing plants can thus be difficult as all are unique. When calculating the COP of a heat pump system a number of losses within the process should be included. Just how many losses are included in the calculation differs from plant to pant. Likewise, elements such as air temperature, humidity, defrosting and district heating temperatures may also affect the COP value. The average annual COP of the heat pump system in Saltum - after having deducted all losses - is above three; even at 0 °C.

Sector coupling for higher efficiency and flexibility

While the share of renewable energy in the electricity sector continues to grow, other sectors, including the heating sector, to a large extent still depend on fossil fuels. Large electrical heat pumps have proven an efficient technology for the electrification of the heating sector and a valuable asset in creating integration and balance between energy systems and sectors.

The system in Saltum is a great example of flexible and efficient sector coupling, as the heat pump is capable of converting power from wind turbines to heat thus creating an interaction between the electricity and district heating sectors. Sector coupling is one of the keys to the sustainable energy system of the future and is considered an important tool in meeting the 2030 national energy and climate targets in Denmark.

“We chose to engage in a collaboration with Aalborg CSP concerning a heat pump for Saltum. The pump they offered had higher revenue over time, although, up-front the solution was more expensive. Our collaboration with Aalborg CSP has proceeded without any significant issues and minor bumps in the road/issues have been resolved with a good result from both parties. We hope that our consumers in terms of the price on heat will benefit from the solution we have made here in Saltum. At the same time we are pleased to have chosen a green solution, which will help us reduce our CO2 emissions” states Ole B. Hejlesen, chairman of Saltum Fjernvarme.

With a capacity of 1.2 MW at 0 °C, the heat pump system is capable of producing approx. 8,000 MWh heat annually thereby covering approx. 80% of the customers’ heat consumption. Besides offering a cost competitive solution for heat production, the integrated heat pump system also prevents emission of at least 1,150 tons of CO per year.  

Project Facts:

  • Client: Saltum Fjernvarme A.m.b.a.
  • Location: Saltum, Denmark
  • No. of customers: 370
  • Technology: Integrated air-to-water heat pump system
  • Plant capacity: 1.2 MW
  • Annual energy production: 8,000 MWh heat/year
  • Suppliers: Aalborg CSP A/S in collaboration with Innoterm and Frontmatec
  • Scope of supply: Turnkey delivery of integrated heat pump system, installation, and building.
  • Maximum temperature: 72 ºC
  • Type of heat pump: Electric air-to-water heat pump from Sabro
  • Expected system lifetime: 20 years
  • CO2 savings: 1,150 tons/year equaling approx. 70%