Figure 2. Hourly peak power in buildings, with and without Leanheat control
HOFOR sees district heating Flexumers as an important measure to minimize fossil-based peak load production and incentivize renewable-based heat-producing units. The same principle of peak power optimization can be utilized in de- mand-response solutions for district heating concerning charging and discharging the thermal energy in the building mass. Leanheat can offer flexibility from an aggregated build- ing stock, making it possible for the district heating company to produce heat and use it in the buildings when it is most beneficial economically or ecologically. The DH company will thus reduce the use of fossil-based heat sources and prior- itize renewable-based ones. For example, with the advanced knowledge of the building thermal mass, Leanheat Building can enable price signals to adjust the building heat supply to take advantage of low-cost periods, for example, when there is a large share of fluctuating renewable energy in the system. Case example: optimization of domestic hot water storage tank control. Having data available from communicative components or controllers gives a high degree of freedom for testing and val- idating new functionalities. Besides the heating supply to the building, the domestic hot water (DHW) system is also relevant for improving performance based on digitalization and AI. As part of the HEAT 4.0 project (Digitally supported Smart Dis- trict Heating, IFD ref. no.: 8090-00046B), the operation of DHW storage tanks was analyzed to develop a control method for reducing the district heating return temperature and the peak power. One of the test site installations is shown in figure 3.
Leanheat’s AI learns how the building’s thermal mass reacts to ambient conditions and evaluates the flexibility potential based on the forecasted weather and set comfort require- ments. The district heating utility can then use the estimat- ed flexibility to minimize the load during peak-load periods. For example, during the morning peak, the control allows the discharging of the heat previously stored in the buildings by reducing the supply temperature for space heating by up to 30%. After this, it is recharged as soon as possible before the following day. The variation of supply temperature during this period still ensures that the thermal comfort in the building stays within the recommended limits. As presented in Figure 1, the initial results of the demonstra- tions for the cluster of 17 buildings show that the average morning peak decreased by 14%, compared with the average peak consumption before the implementation of the smart control. The connected buildings also reduced their heat- ing energy consumption, predictively factoring in upcoming changes in weather, such as solar radiation and wind. Based on the demonstration results, the overall economic and envi- ronmental benefits of Flexumers in Copenhagen will be quan- tified by mid-2023. The peak demand data measured at the buildings in Figure 2 show that the maximum peak power has decreased from 27.5 kW/building to 21.5 kW/building (-22%). The calculation compares the highest peak during load shifting to the high- est measured peak in the previous heating season at the same outdoor conditions.
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