In the energy world of the past, different energy carriers operated separately with distinct boundaries. In the future, the complementarities of electricity, gas or heat will be a supporting element to provide greater flexibility to the global energy system.


InterFlex investigated the use of cross-energy carrier synergies to relieve distribution grid constraints in an efficient and cost-effective way. Through sector coupling, InterFlex supported the transition of the energy sector towards the decarbonisation of traditionally fossil fuel-based sectors such as heating and transport, which also helps to facilitate the overall integration of a higher share of renewable energy.

Gateways between networks can be exploited to increase the combined system efficiency and release new flexibilities and thereby reduce grid investments.

Steering of HVAC (Heating, Ventilation and Air-Conditioning) building assets to manage thermal peak demand: In the mornings and evenings, the heat demand is higher than at other times of the day, resulting in peak loads in a district heating network. At the same time, the building temperature often increases due to social behaviour so that there is no real need for extra production. E.ON, in its role as operator of Malmö’s heat network, exploited in the Swedish demonstrator the thermal inertia of the building’s envelope, i.e., the inbound heat in the building. Heating devices of the buildings (HVAC) could be controlled and the corresponding thermal loads be shifted in time without impacting the customers’ comfort.

Coupling of two urban thermal networks to enhance the global system efficiency and provide flexibilities to the electrical distribution grid: E.ON operated a commercial heat pump in Malmö, where waste heat from a data centre was upgraded to a useful temperature and delivered to a local heat network, providing thermal energy to commercial customers. At the same time, cooling was produced and provided to the data centre and surrounding commercial buildings, showing an overall high efficiency. In case of high electricity demand in the distribution system, the heat pump could be switched off, and the buildings and facility could be supplied by conventional district heating, and by using redundant cooling installations.

Use of thermal household storage devices to provide flexibility to the distribution grid: The efficient use of thermal energy storage to relieve distribution grid constraints was implemented in the French demonstrator Nice Smart Valley and the Swedish demo in Simris. Distributed power-to-heat assets, such as heat pumps and hot water boilers were steered according to DSO’s needs. In the case of the heat pumps, the operation of these assets was optimized by considering the thermal inertia of the buildings and household envelopes. In case of a local renewable over-generation in an islanded microgrid, the surplus energy was used to heat the water tanks, instead of curtailing the RES production (balancing).

Dual-fuel (gas/electricity) hybrid heating systems to relieve distribution grid constraints: In the French demonstrator household and commercial hybrid heating devices were implemented to provide flexibility to the electrical distribution grid. Residential heaters as well as a hybrid roof top unit for large commercial buildings, both containing condensing gas boilers and an electric heat pump, were used during winter demand peaks, when switching from the heat pump to gas, providing reliable remote controlled flexibility in the form of a reduced electricity demand.

Gas-fuelled micro-CHP units to provide additional electric production and thereby flexibility to the grid: Nice Smart Valley experimented an Internal Combustion Engine micro- CHP that produced power and heat thanks to a gas engine coupled with an electrical power generator. Flexibility (electricity production) could be activated according to grid needs.

The gas/electrical flexibilities have the advantage of being reliable, programmable, quick to activate and long lasting. This makes it an interesting type of asset for long-lasting flexible capacity, which is highly valuable for winter peaks or for network incident management. In addition, the tested solutions had no impact on the gas network because of its high capacity; no gas grid constraints exist today, neither are they expected in the near future.



 The InterFlex demonstrators on Cross-Energy Carrier Synergies successfully implemented innovative equipment and IT-solutions, for a global cost optimisation beyond the electric system. For this aim, thermal networks were integrated in order to work side by side with the electric system, for example to absorb DER production peaks.
In particular, the Swedish demonstrator in Malmö developed efficient tools for load peak shaving, and market-ready solutions for certain small-scale district heating sectors, thereby sustaining the decarbonisation of the heating sector.


 Hybrid residential and commercial assets fuelled by both electricity and gas were tested in the French InterFlex demonstrator and have shown their performance. The gas resource provided easily controllable flexibility as an alternative to batteries or curtailment.





 District heating constitutes a strong asset for cross-energy carrier synergies where the corresponding thermal networks are in place. However, the latter are not equally well developed in all parts of Europe and still need to be promoted.


Another challenge to be underlined is linked to business and profitability aspects. The driver for enrolment of multi-fuel customers and more globally the incentive for the use of cross energy carrier flexibility will be inherently bound to the price spread between the various sources of energy.


In most InterFlex countries, the flexibility service provider monetizes the flexibility and will manage the risk bound to fluctuating asset profitability.


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