Energy Networking
The Virtual Power Plant
Information and communications technology will play a key role in ensuring successful power plant management in the 21st century. This technology will be particularly valuable when it comes to linking a spectrum of energy suppliers into a tight networkthus creating a virtual power plant.
Connecting many energy suppliers together to form a virtual power plant poses a special challenge for information and telecommunications technology. Numerous setpoint and actual values must be compared in a decentralized energy management system, automation units have to be controlled, and forecasts of sun, wind and consumer behavior must be obtained
It's not the individual driver or the most powerful engine alone that decides who wins or loses in a Formula One race. Data from competitors has to continuously be registered, evaluated and transmitted to the drivers and the team managers. This example can be applied to power supply management as well. Anyone wishing to take pole position on the energy market these days also needs to manage a great deal of information. "In the future, IT solutions will be the decisive factor governing a power company's competitiveness," says Dr. Erich Georg, head of Instrumentation and Control at Siemens Power Generation.
The next few years will be marked by a dramatic increase in the number of distributed power supply units, including wind, photovoltaic, fuel cell, biomass, and combined heat and power (CHP) plants. Smart information management is essential when it comes to connecting such facilities with one another.
"With the help of modern communications and control technology, such systems can be operated like a single large 'virtual' power plant," says Dr. Werner Brinker, CEO of EWE AG in Oldenburg, Germany. However, to accomplish this, power companies will have to assess and forecast energy demand and available resources and draw up cost-optimized energy-use plans. In addition, market data will need to be combined with power generation data in near real-time and everything will have to be available online. That's the only way to ensure that all the information in the power generation system is networked and can be evaluated and processed by everyone involved. In a sense, such a system provides staff with a basis for making decisions at the push of a button. In theory, the technology required to do all this is already available; but today's power supply systems have to be completely transformed in order to implement it. Instead of focusing on merely guaranteeing supply and maintaining sufficient reserves, power companies will have to work in harmony to shape their collective output to meet widely varying real-time consumption.
The illustration above shows how information management for tomorrow's power supply systems could be organized. What's absolutely essential is a high-performance communications link connecting the control center to the various generation and storage units as well as to private and industrial consumers. Not everything can be managed as desired, however. For example, a shredder or a billboard can, if necessary, be turned off at night; a hospital cannot. Local, decentralized energy management systems (DEMS) are therefore needed to compare supply information with market demands. The first step normally involves analyzing the weather forecast. After all, power supply companies using renewable energy sources such as the sun or the wind need to know things like whether more sunshine or weaker winds are to be expected over the next few hours. The forecast is also important for predicting consumer behaviorif temperatures are expected to drop, for example, more energy will probably be used for heating.
"These forecasts will be used as a basis for drawing up a generation schedule composed of 15-minute blocks," says Dr. Rainer Bitsch, head of Services/Energy Concepts at Siemens Power Transmission and Distribution in Nuremberg, Germany. An online optimization system with access to energy production management and load regulation technology will collate the data. The setpoint values will then be passed on to the production, load and storage systems, which will send back current actual values.
Such systems will communicate with each other via a network composed of leased lines and switched connections. Dedicated lines and ISDN connections are the communications systems of choice when managing biomass or CHP plants online. With them, individual electrical and thermal power values can be constantly transmitted at set intervals (once every minute, for example). However, switched connections are quite sufficient for multi-hour power schedules at solar power plants as compared with home fuel-cell power systems. The data transmitted by such connections lets the distributed production units know how much power to provide over the next few hours. Connections can be established as needed should unexpected events make it necessary to compute a new data batch. Switched connections would also be used to transmit weather forecasts from a meteorological service. So-called profile-capable electric meters are required for billing, whereby power companies call up the data at least once every day, via radio or modem, for example.
Depending on the project (e.g. fuel-cell or off-peak storage heating systems), ripple control systems can also be used. These one-way communications systems do not use check-back signals. Production or storage units turn themselves on or off in response to certain high-frequency signals. Data can be transmitted via radio in regions lacking a comprehensive communications network.
Power companies have been facing a completely new situation since the deregulation of the energy market, as long-term contracts are being replaced by daily competition. They must therefore continuously ask themselves how much energy they can produce and how much they need to supply. They also need to know how expensive it is for them to generate electricity and at what price they can purchase and resell it.
What's more, power companies require reliable answers to these questions within minutesnot just for the current moment, but for a period of several days. That's the only way they can plan in advance. When a supply bottleneck occurs, a power company can purchase electricity at a power exchange or, if it is producing a surplus, sell the excess at a profit. "Having the right information available at the push of a button is a precondition for competing on the power market," says Dr. Paul Girbig of Siemens Power Generation. New IT solutions such as Siemens' PROFIT Cockpit (see box) assist operators in making decisions. The system takes into account parameters such as process engineering states, maintenance and repair measures, fuel and operating costs and income from the sale of electricity. With the help of integrated forecast modules, information can be generated to predict loads, calculate production costs and plan for spare parts.
A number of pilot projects relating to smart power distribution networks are now under way in Germany. One such project is "EDISon" (German acronym for Power Distribution Networks with Innovative, Distributed Energy Transducer, Storage and Communications Systems). Run by a consortium of 17 companies and research institutes, EDISon is slated to design a concept for a new, decentralized network structure incorporating a communications system by 2003. "The network needs to be smart and modular," says Dr. Heribert Schmidt from the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany. The project's partner organizations will develop not only the systems, but also the standards and communications interfaces. The EDISon project is headed by the Karlsruhe municipal power company, the Fraunhofer ISE, EUS GmbH, Gelsenkirchen and Siemens AG.
A second project is now under way to install a DEMS processing system at a power generation site located on a former military base in Werl, Germany, by 2010. The site consists of a wind power station, a biomass district heating plant, a solar power plant, and several electrical and thermal loads. In addition to Siemens, the project's partners include Saarberg Fernwärme AG and the Institute for Technology and Knowledge Transfer at the University of Paderborn/Soest. Projects like these provide valuable experience, which the participants hope will put them in pole position in the race to implement the power supply systems of tomorrow.
Sylvia Trage
Where Will We Get the Power for Next Weekend?
Energy management with Siemens PROFIT CockpitMark Conrad, the production manager of a power company, has to manage a power generation system composed of eight generating units: four coal-fired power stations, two waste-fuelled power plants, and two gas turbines used only to provide reserve power, due to the higher fuel costs involved. Conrad has two goals: to maintain power generation at a reliable level so as to meet the demands of supply contracts, and to produce energy at the lowest possible cost. As a first step, he turns on the PROFIT Cockpit software's "Production" feature, which gives him an overview of the entire production flow. He selects a specific time in the future (the weekend of April 23 and 24 in the illustration) and sees that load capability (the maximum amount of energy the generation system can produce) will decline drastically at that time.
Although demand can just barely be met, the costs will be high. The red areas indicate that expensive reserve power will have to be used. Why? Conrad takes a close look at the status of the generation units for the weekend, and sees that Coal Plant 1 will be shut down for maintenance (red). The gas turbines, which were in reserve, will now have to go into operation, although they are very costly at 15 /MWh. Conrad then checks if the maintenance work on Plant 1 can be postponed. Cockpit says no because the plant has a leak in the high-pressure unit, which requires a boiler pipe to be repaired. Conrad then checks if he can save costs by using an existing energy procurement agreement. His hopes are quickly dashed, however, as Cockpit indicates that the agreement's price of 18 /MWh is even higher than operating the gas turbines. He still has the option of purchasing electricity at the power exchange. To do this, he switches Cockpit from "Production" to "Market" and from there to "Purchase." A diagram on the screen shows how much power he would need to purchase, when and at what price, if he wishes to acquire it more cheaply than he could generate it himself. Conrad then transmits the diagram to the Purchasing Department. If there is power available on the spot market at the price and time given, he will still be able to provide energy on the weekend at a reasonable cost.