Transmission grid operators need to precisely predict the feeds of electricity from renewable energy a few days in advance so as to market these as effectively as possible on the electricity stock exchange EPEX. A heavily fluctuating supply of solar and wind energy makes these forecasts more difficult. Researchers at the Fraunhofer Institute have therefore developed a software system together with TenneT TSO GmbH that pools a range of forecasts so as to create one sole reliable one.
A heavily fluctuating supply of sun and wind energy makes forecasting feeds more difficult. (Photo © adimas - Fotolia.com)
Electricity is something we take for granted. A touch of a button and on goes the light. However, in actual fact a great deal of effort goes into providing energy. Experts have to calculate precisely when and how much electricity is needed since demand fluctuates. For instance, at the weekend when offices and shops are closed less energy is needed than on Monday. And on a cloudy day people switch on the lights at home earlier than on sunny days. Transmission system operators, in particular, have to know in good time when electricity is generated from renewable energies as they have to transport this electricity all over Germany and sometimes market it themselves.
Sun and wind energy fluctuate enormously
Transmission system operators strive to plan feeds from renewable energy for the next day as precisely as possible. A challenge here is the available quantity of sun and wind energy which although subject to constant rise overall are also both subject to heavy fluctuations by their very nature. For instance, the wind energy feed at German transmission system operator TenneT TSO can vary within just a few days between several hundred and approx. 9000 megawatt. With photovoltaics this variation in output is possible within just a few hours – corresponding to the difference between the output of a small gas turbine and nine large conventional power stations. For a good while now services have existed that pre-calculate the weather and the resulting production of green electricity. So as to achieve as accurate as possible predictions the forecasts of a variety of suppliers are used. These are summarised into a forecast for the day ahead in an optimised »meta-forecast«. Added to this are forecasts for other regenerative energies like biomass, hydroelectric power, geothermal power and landfill gas. These all combine into the entire forecast quantity of green power. If this is gauged in good time green electricity can be sold in advance at the EPEX electricity stock exchange.
The forecast and thus also sale at EPEX still has room for improvement – something demonstrated by the Fraunhofer AST application centre located in Ilmenau with its new energy management solution EMS-EDM PROPHET®. This program generates an improved overall forecast by drawing on a variety of individual ones. The entire calculation process consists of some 15,000 individual steps – requiring a huge degree of software automation.
The available quantity of sun and wind energy is growing constantly but it is also subject to heavy fluctuations. (Photo © pat fauve - Fotolia.com)
Forecasts every 15 minutes possible
However, the software can go one step further. It is not only able to calculate electricity a day in advance, it can produce precise forecasts every fifteen minutes by correcting day-ahead projections using short-term forecasts on the spot market every 15 minutes. This means TenneT TSO GmbH can react very quickly to feed fluctuations. Optimising the marketing of renewable energy on the EPEX means revenues from renewable energy can be maximised and the need to resort to using balance energy is minimised. This in turn helps reduce the renewable energy levies that every consumer pays through their electricity bill.
At present, this program is being used for the spot market for solar, wind, water and geothermal power. In the near future the software will be able to include other energy sources such as biomass. The data from the EMS-EDM PROPHET® system can also be used for websites online. These are made available to services like the information platform of the German transmission system operator EEG/KWK-G (www.eeg-kwk.net or www.transparency.eex.com). »A flexible software solution is particularly important given the rapid changes to prevailing circumstances,« explains Dr. Christian Schulz, grid manager for renewables at TenneT TSO GmbH. Due to the high degree of automation of the EMS-EDM PROPHET® system users can react swiftly to regulatory changes.
New requirements and greater complexity through liberalisation of the energy market
Energy markets in Europe are currently undergoing massive changes due to liberalisation and the promotion of increased feeds that fluctuate both centrally and decentrally. Rising to the future challenges of economic, ecological, efficient and safe energy supply requires a holistic approach to the processes involved in energy supply.
EMS-EDM PROPHET® is made up of high-performance time series management, comprehensive energy data management with modules for grid usage and accounting grid management, a scheduler for the automation of business processes and an optimisation and prediction module for sustainable energy management. In this way the holistic application solution provides optimum support for the different functions and activities of all market players – from energy generation to retail and distribution.
Incidentally, users of the EMS-EDM PROPHET software solution and those interested in it should note down the following date in their diaries: 11-12/09/2012 will see the holding of the 2012 users’ conference at Hotelpark Stadtbrauerei Arnstadt. In addition to numerous practice-oriented lectures and workshops this year will also include a separate exhibition area.
Sources: Fraunhofer Institute, EDM Prophet