Impact of Flexibility Implementation on the Control of a Solar District Heating System
Abstract
:1. Introduction
2. Methodology
2.1. Case Description
2.2. Optimisation Problem Solving Strategy
- Selection: the individuals of a population are sorted according to the value of the fitness function and chosen or not for crossover (akin to natural selection).
- Elitism: the higher-ranked individuals are passed on to the next generation with no change (akin to cloning).
- Crossover: two individuals are chosen as parents and their chromosomes are combined to create new “child” individuals that, if they are a feasible solution, pass to the new generation (akin to sexual reproduction).
- Mutation: single chromosomes of an individual have a chance to acquire a new value; if feasible, the child solution passes on to the next generation (similar to a natural mutation).
3. Results and Discussion
- Having a model capable of predicting how changes in the operation of a network affect its behaviour, combined with optimisation enabling the benefits of heat network inertia to be exploited. The ability to vary the mass flows ensures that energy already in the system is not wasted and that supply arrives on time. This is performed in a number of ways. When there is surplus energy in the system, mass flows can be reduced, thus lowering the return temperature. When demand is expected to go up, mass flows can be increased to raise the supply temperature of the network in anticipation. When demand goes up before the network is ready to meet it, mass flows can be increased to reduce the time during which end users risk a loss of QoS.
- The inertia of the network alone might not be sufficient to play the role of buffer whenever steep changes in supply or demand occur. While it can be harnessed to reduce costs, when sudden or major imbalances occur, it is also feasible to exploit the flexibility of the end users. Buildings do not immediately lose their comfort zone when heat is interrupted (unlike electricity, where any curtailment is immediately felt), allowing a small window in which supply can be reduced or completely cut out without the consumer noticing. This window varies from end user to end user, but a general flexibility function can be used to help the demand to rebalance the network and to prevent any major losses in the QoS. The use of a flexibility function is cheaper than reactive generation, aiding also in reducing costs.
- A second use of the model in combination with optimisation, regardless of having a flexibility function or not, is a different management of existing storage. Instead of using storage for excess energy during sunny hours and overproduction during evening hours, optimisation proposes using it more dynamically to avoid or reduce the use of fuels in the boiler room. In this way, even if the storage does not reach its maximum load, costs will still be reduced, and the solar fraction of the system met.
4. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Component | Nominal Capacity/Size |
---|---|
Gas boiler | 6 MWth |
Biomass boiler | 3 MWth/0.75 MWth (min.) |
Heat pump | 40 kWel |
Solar field | 1.7 MWth peak (2340 m2) |
STTS | 150 m3 |
Parameter | Value |
---|---|
Cost of electricity [EUR/kWh] | 0.14 |
Cost of gas [EUR/kWh] | 0.039 |
Cost of biomass [EUR/kWh] | 0.023 |
Gas boiler investment cost [Mio EUR] | 1.20 |
Biomass boiler investment cost [Mio EUR] | 2.10 |
Solar collector field investment cost [Mio EUR] | 1.35 |
Lifetime of all components except gas boiler [year] | 20 |
Gas boiler lifetime [year] | 25 |
Interest rate [%] | 3.75 |
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Betancourt Schwarz, M.; Veyron, M.; Clausse, M. Impact of Flexibility Implementation on the Control of a Solar District Heating System. Solar 2024, 4, 1-14. https://doi.org/10.3390/solar4010001
Betancourt Schwarz M, Veyron M, Clausse M. Impact of Flexibility Implementation on the Control of a Solar District Heating System. Solar. 2024; 4(1):1-14. https://doi.org/10.3390/solar4010001
Chicago/Turabian StyleBetancourt Schwarz, Manuel, Mathilde Veyron, and Marc Clausse. 2024. "Impact of Flexibility Implementation on the Control of a Solar District Heating System" Solar 4, no. 1: 1-14. https://doi.org/10.3390/solar4010001