Without electric boilers, the balancing of the grid will be significantly more expensive.
provide services in the very short term (milliseconds) but can provide services in the FFR market (short term) and the longer term. Heat pumps are often planned in the day-to-day planning. Electric boilers can also operate in the longer term. Due to the high flexibility, the limited costs, and the limited requirements for space, electric boilers are a very suited and cost-efficient technology for regulating the power system. The following table shows the capacity the TSO plans to use in the intraday planning in the western part of Denmark (DK- West) to maintain the balance in the energy system:
Heat planning Unlike individual buildings, DH with heat storage can utilize multiple efficient and RE sources cost-effectively, such as waste heat, heat from large-scale heat pumps, CHP units etc. This is what justifies rather large investments in DH networks integrating the buildings. Furthermore, being connected centrally, buildings can not only use RE via the DH system but also offer significant potential to support and balance the power grid. At low forecasted wholesale prices for electricity (equivalent to the high share of renewable energy in the grid), heat pumps and potentially also electric boilers are planned to operate. In addition, electric boilers will stabilize the grid frequency. At higher prices on the wholesale market (limited RE in the grid mix), where additional power is needed from dispatchable power plants, heat pumps are disrupted, and CHP plants are called into operation. Very high electricity prices indicate that the most in-efficient fossil-based power plants are in operation to serve electricity demand, which cannot be disrupted. Therefore, electricity should be avoided as a single source for heat production, and heat should instead be produced from CHP plants. Conclusion DH systems can provide very cost-efficient balancing of the power grid, which benefits both DH consumers as well as the TSO. The Danish experiences show that DH networks ensure a cost-efficient build-out of RE by ensuring that a larger share of the produced electricity can be utilized instead of being curtailed at a cost. Without the shorter-term services delivered to the grid operator, it will be much more expensive to balance the power grid, and the question is whether it is possible at all in a fully RE system.
DK1 - West
FCR
aFRR mFRR
Flexible consumption
1.0
Battery
0.4
Electric boiler
56.0
138.0
10.0
Heat pump
0.7
Power plant
8.0
20.0
Diesel engine
3.8
Table 1: Balancing tools in Denmark West, MW
From Table 1, it is clear that electric boilers play a significant role in the short-term balancing of the system as seen in the allocated capacities. Alternative to electric boilers The question is, what would be the alternative to balance the renewable power system if electric boilers were not available? Regulation on electric boilers serves two purposes, partly to absorb excess production of electricity, and partly to provide short-term balancing between production and consumption. In an energy system without any renewable sources, the short-term balance in the system is upheld with very short- term fluctuations in production from the dispatchable power plants. This is an automated procedure where the plant output is automatically regulated based on the frequency in the electric system. In an energy system almost entirely supplied from renewable sources and with limited production from dispatchable energy, it will be more difficult to keep the short- term balance. In this situation, power plants cannot adjust, and the frequency must be balanced from other sources, such as electric boilers or batteries. In the Western part of Denmark with a very high renewable energy share, the TSO purchases more than 200 MW for short-term services from electric boilers (see Table 1 above). A likely alternative would be to purchase a similar capacity from batteries at a higher cost. The very clear market signals (the hourly electricity prices) catalyze an increasing amount of flexible production/demand to produce or use electricity. Without clear signals, the flexible use of electricity is not activated, and the need for balancing services would likely be significantly higher than the 200 MW since the active balancing should handle all imbalances alone without assistance from other technologies (flexible use). Flexibility is important for the electric grid since electric boilers and other flexible sources in this situation help the electric grid and don’t add further costs to the grid.
For further information please contact: John Flørning, JNF@ramboll.com
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