Large scale electrical grid flexibility control of heat pumps (SLAV)

In a power system with a large share of intermittent sources, such as wind and solar, the need for flexibility to balance variations in electricity production will increase. Flexibility, or demand response, can help reducing problems due to bottlenecks and shortage of capacity in the electricity grids, as well as avoiding curtailment of renewable energy sources. This project has investigated possibilities and constrains for a concept where residential heat pumps are aggregated and controlled via the manufacturers cloud service to support the power system with flexibility with focus on Svenska kraftnäts ancillary services, local flexibility markets or bilateral agreements. The project covers several aspects, such as technical constraints of heat pumps, electricity market and power grid barriers, cybersecurity issues and the information chain with focus on suitable communication protocols. The project results are based on expert interviews, literature review and field tests.

Results from the project shows that the electricity market has several barriers that hinder heat pumps from offering demand response. One barrier is the minimum bid size for the balancing markets, which requires aggregating many heat pumps. Another barrier is the need to have the same balance responsible party (BRP) for all customers in a bid, but there are several BRPs in Sweden. A third barrier is the demand of real-time measurement of flexibility resources by the balancing service provider. This is a potential problem since today’s heat pumps lack electricity meters, which risk to lower the accuracy of demand response measurements.

Within the project technical experts from the heat pump manufacturers were interviewed. They have a common ground in how fast their heat pumps can be controlled to decrease or increase power consumption. The auxiliary heater can change power in a second, but it may need new software adapted for flexibility. On/off compressors can also be turned off in a second, but they need some time to restart. Variable speed heat pumps are much slower to change power. It can take minutes to start or stop them or control their speed when they are already running. 

The project has investigated different ways to communicate between the aggregator, the cloud services and the heat pumps. Seven different communication standards were evaluated, mainly higher-level protocols, also referred to as communication middleware. OpenADR and IEEE 2030.5 are two US-based standards that have great potential for enabling demand response from heat pumps. A potential drawback is that they are not that common in Europe today. Interesting European alternatives are EEBus and EFI/S2. All these four standards are free to use or can be bought at limited costs. They are not ranked here as further work is needed to recommend any of them before the others.

Heat pumps need to be controlled over the Internet to effectively contribute to flexibility. This can, as for all internet-connected devices, make them vulnerable to cyberattacks. The threat from cyber-attacks has to be taken seriously as hacked heat pumps could, at least in the future, cause severe problems not only for the heat pump owner but also to the national power system.