24 June 2014

Challenges and recent developments in applications with large scale heat pumps

Large capacity centrifugal heat pumps are reducing CO2 emissions for more than 35-years already, increasing thermal efficiency and renewable energy contribution of European district heating networks. The variety of heat sources and operating conditions of district heating systems is a big
challenge in the heat pump design and impose an individual approach to the heat pump design of each project. The key element of a heat pump system is the compressor, with characteristic that should cover all possible operating points, including minimal load
conditions. Several applications with various heat sources will be presented. The 3rd raw sewage water heat pump installed in 2008 in Sandvika (Norway) is a good example for the continuous
development of simultaneous district heating and district cooling production, balanced with sewage water as additional heat source. The big challenge was to develop a heat pump with an additional sewage water evaporator, which performs condenser function in a Summer Mode. Due to the flexibility of operating modes the heat pump copes fully automatically with
the variable demands for cooling and heating during the whole year.
As a response to the increasingly restrictive environmental regulations of refrigerants, the first heat pump installation with thermal output of 16MW using the ultra-low GWP working
fluid HFO-1234ze is in successful operation at Rolfsbukta (Norway) since commissioning in 2012. Big developments have been done recently in some large capacity heat pump projects exploiting geothermal water from Neocomian and Dogger aquifers in the vicinity of Paris. Different arrangements of high temperature centrifugal heat pumps increasing significantly the heat exploitation from geothermal wells in district heating systems will be explained. The presented examples will give an overview of recent developments and challenges in large centrifugal heat pumps technology, offering heat upgrades up to 120°C and 20MW
heating capacity per unit.