Flexibility At What Cost? Climate, Economic, and Grid Impacts of Power–Heat Cross-Vector Flexibility in a Residential Energy System across Swedish Electricity Price Zones

Sammanfattning

The increasing share of weather-dependent renewable energy in the European electricity system, as a consequence of the European Union’s climate ambitions, has led to increased spot price volatility, negatively affecting consumers due to unpredictability. This case study assesses how flexibility (including power-heat cross vector flexibility) in residential buildings can affect annual costs, emissions, and electricity usage from the grid during peak hours in all electricity price zones in Sweden (SE1-SE4), compared to conventional residential energy systems using district heating and power from the grid only. Local conditions, such as spot prices, outdoor temperatures, and solar irradiation, were varied for each price zone. A model was created to replicate the energy system from a demonstration site in Kungsbacka, located in the Swedish electricity price zone SE3, and it was validated using measured data before extrapolating the results for all price zones, respectively. The technologies included in the model are solar collectors, photovoltaic cells, an accumulator tank, an electric battery, a local DC-grid enabling electricity sharing between buildings, and an electric boiler, as well as connections to both the power grid and the district heating grid. The results show a potential climate benefit when assessing emissions with historical average emission factors, with significantly reduced emissions from the flexible residential energy system in all price zones. The larger power-to-heating interaction found in SE1 and SE2 resulted in the largest emission reductions. On the other hand, although annual operating costs were decreased, the necessary investments for the technologies enabling flexibility resulted in increased annual total system costs compared to the base case in all price zones. The lowest price increases were found in SE1 and SE2, where a change in discount rate (from 5% to 2%) would have enabled an overall economic benefit. The PVs, the DC grid, and the electric battery were found to be cost driving investments relative to their system benefits. The load on the power grid was drastically increased in all price zones compared to the base case from running the electric boiler, potentially reinforcing bottlenecks in the grid. Still, the flexible energy system could aid in balancing spot prices and facilitating more renewable energy production in the energy mix. Future studies should evaluate the system under future market conditions, include alternative district heating mixes, and apply multiple approaches for assessing emissions and grid effects to better capture system-level impacts.