Built environment 
Reprinted from: European Heat Pump NEWS Issue 4 | December 2011. Permission granted
A new study by Ecofys and Prognos upon initiative of the German Federal Ministry of Economy and Technology (BMWi) is analysing the contribution of heat pumps in a future German electricity market with a larger renewable energy source (RES) share. Political targets are set to achieve 80 percent renewable electricity production until the year 2050. This considerable change will lead to residual loads, caused by large amounts of highly volatile renewable electricity production. To maintain a stable futures system storage and peak shaving options are necessary and heat pumps are singled out as one technical solution to achieve this.
Germany’s goals for implementing renewable electricity sources into the system are set to 35 percent (2020), 50 percent (2030) and 80 percent (2050) of the gross electric power generation.
The main share will be covered by wind energy and solar PV power [3]. The main draw back of more RES electricity is the lack of controllability of power output. The power generation depends on the local meteorological conditions, such as wind speed and solar irradiation. It will vary from the demand, potentially causing supply and grid stability issues, if not handled carefully. Heat pump technology may play a major role to store electric energy in the form of heat and to overcome differences in supply and demand of electric energy.
The market environment is generally perceived positive for heat pumps. Today, they can already be controlled to a limited extend by the grid operator via the ripple control signal. They can switch off heat pumps in times where demand exceeds production in order to decrease the load on the grid. To improve this potential, a shift in heat pump operation is necessary: where today the focus is on efficient provision of heating, cooling and hot water, the future operation mode must maintain consumer comfort while at the same time give high priority to including the largest possible share of RES electricity. It is such a system that is needed to provide the required dispatchable capacity. Consequently this type of system is analysed for two functions:
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Heat pumps can be used to store heat using the thermal inertia of the building structure, the interior and materials. This is ‘overheating’ is limited to a small temperature difference (2°K) and can only cover a shorter timeframe of off-grid operations. Thus, its load balancing impact is similarly limited. A range of two degrees Kelvin is set, as humans can only recognise temperature differences greater 2°K – thus comfort is unaffected.
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An optimised system would have to be equipped with an additional/enlarged storage tank. The storage capacity of the system defines its off-grid and peak shaving capacity. The physical infrastructure will have to be enhanced by a sophisticated co
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What the true potential of heat pumps is, as dispatchable load to increase the system flexibility;
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What impact can be observed for heat pumps positive/ negative adjustment potentials in grid stability;
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What the impact on overall systems efficiency of power-optimised and -operated heat pump systems;
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How heat pumps compare to electric mobility and pump storage power stations;
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What economic effects occur on the grid and the individual systems level; and
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Do sufficient incentives exist to make heat pumps as dispatchable load a reality?
The heat pump market in the scenario is expected to develop as follows:
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Scenario A Scenario B
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Heat pump stock in 2020 975 000 units 1 230 000
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Heat pump stock in 2030 1 550 000 units 2 200 000
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Heating capacity until 2030 17,3 GW 24 GW
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Installed electric capacity until 2030 3,7 GW 5,3 GW
Volatile renewable energies (on- and off-shore wind and PV) is expected to provide 80 GW by 2030. Fifty percent of the installed electric heat pump capacity is assumed to be available for load management. The assumed potential of storing electricity in form of domestic heat is realised either via available storage volume and its maximum temperature level, or via the heat capacity of the building structure.
Releasing additional potential by using larger heat storage tanks is only briefly covered in the report. It must be noted that the increased flexibility will cause higher installation costs. The costs can be expected to be moderate for the communication module and the smart meter, which are the only accessories needed if the buildings heat capacity is used. The cost is higher, if additional heat buffer tanks are used. PA
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