Final report Task 3

IEA HPP Annex 40 Bundesamt für Energie BFE IEA Heat Pump Centre iea International Energy Agency‌

Final Report IEA HPT Annex 40 Task 3

Summary IEA HPT Annex 40 Task 3

In Task 3 of the IEA HPT Annex 40, technology developments for heat pump in nZEB have been performed. Due to the normally highly efficient building envelopes of nZEB the loads of the building are different from conventional buildings. While the space heating operation may decrease, and additional cooling need due to the risk of summerly overheating may arise. On the other hand, the DHW fraction normally has a larger share of the overall heating needs due to decreasing heating demands. Based on this load situation, heat pumps have advantages to supply different building services even in simultaneous operation with efficiency gains.
Therefore, developments performed under the Annex 40 concentrated on two aspects:

  • On the one hand the ability of heat pumps to provide different building services with the same generator led to the development of integrated multifunctional heat pumps. Due to the high integration higher investment in highly efficient components are justified.
  • On the other hand, installation of renewable energy on-site offer option to integrate these components with the heat pump, e.g. a solar thermal system could be operated directly for the DHW production, but could also serve as heat source for the heat pump. Especially the integration by a source storage, eventually as ice storage, can be beneficial both for the collector efficiency and as stable heat source of the heat pump.

In the USA the development of integrated heat pumps (IHP) has already begun in 2005 with a conceptional analysis. In the frame of the Annex 40 variants of IHP have been developed and investigated in field monitoring. Besides an electric system, which is well suited also for retrofitting, a gas engine driven system with on-board power generation in the beta-prototype have been developed. Performance results of the systems confirm the target values of 50% savings vs. the baseline systems.

In Canada and Switzerland, the integration of solar collectors as heat source for the heat pumps have been investigated. Both components or systems, respectively, have been investigated by lab testing which gave the data basis to model and validate the system. As next step the models have been implemented in a system simulations environment and saving potentials were evaluated, resulting in similar performance values as ground-source heat pumps for the respective boundary conditions. Thus, the integration of heat pump and solar components may hold further development potentials for the application in nZEB, where on-site renewable generation is installed as a standard system.

Furthermore, in Japan, an optimisation of the air-conditioning operation with VRV systems could be achieved by separating sensible and latent loads. With a dessicant system which was optimised for low regeneration temperatures, temperature for the sensible load could be optimised. The two steps together led to substantial energy saving, which were evaluated to more than 70 % compared to conventional operation, which is a big step for the air conditioning especially in regions with high dehumidification load.

Moreover, Net Zero Energy Residential Testing Facility (NZERTF) at the NIST campus has been equipped and commissioned in frame the Annex 40. The NZERTF has the capability to provide adjustable and reproducible load conditions of a typical NZEB as test environment of dedicated NZEB technologies. The first two year of operation have been shown as slightly positive balance of the test house itself, so the NZEB target could be confirmed. In the first year, the house was operated with a highly efficient air-to-air heat pump.

The developments show that even though heat pumps are already a very energy efficient technology further development potentials by systems integration and the optimisation of temperature conditions for different applications as well as the integration with other building technology may still yield efficiency gains.


IEA HPT Annex 40
Final Report Task 3