Sector coupling: using renewables-based electricity for heating and transport

The term ‘sector coupling’ refers to the replacement of the use of fossil fuels in transport, heat supply and industry by the use of electricity from renewable energy. Up to now, the potential for reducing carbon emissions in this way has been little used. There are also very few links between the different sectors of the energy system. By dovetailing these sectors using dedicated interfaces and smart management systems, synergy effects can be harnessed for the entire system.

  • Gas

Power-to-Gas systems convert renewable electricity into hydrogen by electrolysis. Further chemical processes are then undertaken to change hydrogen into to methane, quasi natural gas, or even liquid energy carriers. These chemical energy carriers have the big advantage that they can be stored in large quantities and over long periods of time. It is also possible to transport large quantities of energy in the form of methane via existing gas networks. The methane is then available for heat generation in buildings or in industrial processes. It can also be converted back into electricity using gas-fired power plants. As part of SINTEG, several projects are being used to test in practice how chemical energy sources can be produced using electricity from renewable energy. In the NEW 4.0 showcase, for example, an electrolyser is being used to generate hydrogen, which is then fed into the existing gas network or used at a hydrogen filling station to refuel fuel-cell vehicles. The DESIGNETZ project is testing how methanol can be produced from water and flue gas from a power plant using renewable electricity.

  • Heating

Heat has traditionally been generated using oil and gas. While it used to be the case that electricity was hardly used for this purpose at all, now about one in three new buildings is equipped with power-to-heat technologies and can thus be heated efficiently using electricity based on renewable sources. One example of this is heat pumps, which usually work by taking heat from the air or the ground and can be used to generate three or more units of heat from one unit of electricity. As part of the SINTEG showcase C/sells, around 1,000 electric storage heaters, heat pumps, CHP systems and district heating transfer stations are being integrated into a virtual power plant and managed in a way that enables electricity from renewable energy to be used as efficiently as possible. In the WindNODE project, a large power-to-heat plant is being built based on the principle of an immersion heater and connected to an existing district heating network. The thermal output of the system is equivalent to that which would be produced by around 60,000 household kettles. These projects represent just two of many other power-to-heat concepts that are being tested in practice as part of the SINTEG programme.

  • Transport

Electricity is already being used to power trains on a large number of routes. But the vast majority of cars still run on petrol and diesel. Using electric mobility, which has seen rapid development in recent years, it is now possible to power electric cars and lorries using renewable electricity. In the WindNODE showcase, for example, a scalable power storage unit consisting of several hundred disused electric car batteries will be installed. The power storage unit can react quickly to fluctuations in the power grid and balance these out. Using these batteries a second time means that they are used for longer and resources can be saved. As part of the C/sells showcase, a networked charging infrastructure for electric vehicles is being set up across a particular city district and is being optimised by working together with other local energy producers and consumers.

  • Industry

Large quantities of fossil fuels like coal and gas are also used in industry. Here, power-to-heat technologies or methane from power-to-gas plants can be used to supply production processes with heat. New, power-based production processes can also be used. One example of this is the use of microwave technology in drying processes. An example from SINTEG is a project part of the NEW 4.0 showcase, in which experts are testing how induction coils can be used for preheating steel parts and are looking at how these can be flexibly controlled. In another project within the DESIGNETZ showcase, electrolysis furnaces of an aluminium smelter are being converted in order to enable output to be increased or reduced by a quarter. One example of this is heat pumps, which usually work by taking heat from the air or the ground and can be used to generate three or more units of heat from one unit of electricity.

Flexibility: consumers base their consumption on the state of the energy supply

Consumers who have the flexibility of being able to shift their energy use to a different point in time can react flexibly to the state of the energy supply. This enables renewable energy to be used in the best way possible. It also allows energy networks to be eased in critical situations. Digital technologies are being used to flexibilise the exchange of energy the different energy sectors.

  • Private households

Although private households consume significantly less energy than industrial companies, the flexibility they can offer can still be put to good use. Heat pumps can be run, for example, when plenty of wind power is available, and electric cars can be charged using solar power from the roof of the owner’s house. In this way, private households can also make a contribution to making the energy system more flexible.

  • Transport

The transport sector is undergoing deep-reaching changes. On the one hand, the trend towards electric mobility is picking up speed and, on the other, autonomous driving will lead to completely new traffic concepts. Electric cars are equipped with large batteries that could be used in the future to stabilise the electricity grid.

  • Industry

If we are able to run industrial processes at a high intensity at times when there is an excess supply of energy, we can make an important contribution to flexibilising the energy system. Companies could be remunerated for this service, for example on the balancing markets, leading brand new business models to emerge.

The SINTEG programme is testing in practice how energy producers and consumers can each be made more flexible and coordinated with one another. This involves equipping the individual components of the energy system with communication interfaces which enable them to communicate their operating status and also receive instructions. This allows them to react flexibly to the energy supply. As part of SINTEG, numerous projects are testing various ways of making the energy system more flexible. In the DESIGNETZ showcase, for example, experts are developing a smartly networked biogas network system consisting of biogas plants and flexible block-type thermal power stations. The network system is controlled by a self-learning neural network that ensures that renewable energy is used as efficiently as possible. SINTEG is also focusing on expanding virtual power plants. The C/sells project, for example, is integrating generation plants and flexibility options into a virtual power plant. The aim is to optimise how the plants operate as part of an integrated network and to take the strain off the electricity grid.