Grid infrastructure and storage technologies
The energy transition also presents major challenges for our electricity grids. Increasing demands are being placed on distribution grids due to the large number of photovoltaic plants and the wind farms being built. This is particularly the case in rural regions where at times more electricity is being produced than is consumed (Security of Supply).
Electricity grids must be in a position to accept electricity as necessary despite increasing levels of weather-dependent feed-in to the grid from renewable energy sources and to make electricity available. If we are to achieve this goal, we need to use new technologies to create ‘smart’ balancing mechanisms. The district of Bitburg-Prüm in the Eifel hills was selected as a model region and we have been trialling the Smart Country project there since 2011 to test the interaction between different components such as renewable and conventional generation of electricity, energy storage and grid operation in a smart grid. We are testing newly developed voltage regulators for protecting against voltage fluctuations, recording and communicating real-time production and consumption data, and using a biogas storage unit to compensate for peaks in supply and demand. In May 2012, the project received the Smart Energy Award 2012 from the Hessian State Government.
Smart Operator project
Smart solutions are increasingly required to facilitate integration of renewable energies into the distribution grid. In August 2012, RWE Deutschland launched the ‘Smart Operator’ project to develop smart grid solutions at low voltage. 250 test households in the local communities of Kisselbach and Wincheringen (Rhineland-Palatinate) and Wertachau (town of Schwabmünchen in Bavaria) will be connected to a smart low-voltage grid over a period of two years. A control box designated as ‘Smart Operator’ records the current grid status and independently optimises the flow of electricity. It also creates a communication interface for the test households. For example, this enables the use of selected ‘smart’ domestic units that can be calibrated to ensure that the maximum amount of surplus electricity from renewable energy sources is used. The aim of the project is to contribute to ensuring that some of the expansion of low-voltage grids is only required at a later date or is rendered completely superfluous.
Electricity conductors from the next generation
We are committed to development of line infrastructure in order to ensure effective transmission of electricity in the future. We use high-temperature conductors for this purpose. This means that the transmission lines can be heated to higher temperatures than conventional lines and are therefore able to transmit more electricity. They are ideal for upgrading existing distribution grids in rural areas experiencing strong growth in decentral energy generation. They can generally be suspended from existing masts. Hunsrück is a region with strong growth in wind energy, and the test line can transmit twice the amount of electricity over a distance of twelve kilometres compared with conventional lines under otherwise identical environmental conditions. In August 2012, RWE Deutschland set up a high-temperature transmission line on an existing high-voltage line near Argenthal (Rhineland-Palatinate).
In January 2012, "AmpaCity" was added to the large number of projects we are currently running. This project offers new perspectives for operating electricity grids in inner-city areas. The world’s longest high-temperature underground superconducting cable based on the latest technology will be laid in Essen, the location of the headquarters of RWE AG. The materials used for this are able to transmit electricity with negligible losses at very low temperatures of around −200°C. By contrast with conventional superconductors, which have to be cooled to -270°C, high-temperature superconductors permit industrial operation and hence facilitate cost-effective application over the medium-term. This system permits the transmission of large amounts of electrical power at low voltage. It also represents space-saving technology. The advantage for local communities is that valuable land in inner-city areas is not required for grid operation and can be used for other purposes. Work on laying the cable started at the beginning of 2013. The project partners are RWE Deutschland, Nexans as manufacturer of cables and cable systems, the Karlsruhe Institute for Technology, and the Jülich Research Centre as project manager.
New energy storage
The sun and wind are not available day and night. The integration of electricity generated from renewables is therefore becoming increasingly important. If only a small amount of electricity generated from renewables is fed into the grid, conventional power plants have to supply additional electricity. By the same token, they have to reduce their output or even shut down power generation altogether when strong winds start to generate a lot of electricity or solar generation increases. Another factor is that the current capacity available on transmission grids in some regions today is reaching its limits when the wind turbines are operating at full power.
Expanding the capacity of electricity storage systems can provide assistance here. However, established pump-storage technology is not adequate because on the one hand pumped storage is only available for a few hours, and on the other hand the potential for expanding pumped-storage power plants is limited. This is why we are developing alternative energy storage.
Since October 2012, a research and development team from RWE Power at the Coal Innovation Centre in Niederaußem has been looking at possibilities for storing electricity with a new pilot plant ‘Power to Gas’. The aim of this system is to store surplus electricity temporarily as chemical energy in the form of natural gas. Later on, the gas is converted to electricity or supplied to the heating market.
Construction of the ‘Power to Gas’ pilot plant for storage of electricity based on hydrogen also started up in Ibbenbüren in October 2012. From 2013, an innovative technology based on electrolysis from the project partner CERAM HYD will be tested at the plant operated by RWE Germany with a power output of 100 kilowatts. This technology efficiently converts excess electricity generated from renewable energy sources into hydrogen. The hydrogen generated is fed into the regional RWE gas grid and after storage can be converted back to electricity as necessary. RWE Power is developing an adiabatic compressed-air energy storage system in the ADELE project as an additional technology option.