Making Germany s Energy Transition Possible

Transcription

1 Making Germany s Energy Transition Possible Germany has boosted renewables prodction over the last decade, reaching 31 percent in the first part of However, efficient se of that energy reqires that transmission and distribtion networks be pdated. Text: Rhea Wessel Photos: Andréas Lang Green switch Solar rooftops are contribting to Germany s goal of raising the share of renewables to 35 percent by 2020.

2 Kolmnentitel Kolmnentitel Across Erope, demand for renewable power is increasing rapidly. Governments and the EU are pshing to achieve energy independence, and have introdced market incentives to stimlate both prodction and, more recently, consmption of green energy. Local grids mst be pdated for efficient distribtion of energy generated in wind parks (above: Netze BW wind park at Niederstetten) and locally from solar, biogas, and hydropower installations. 24 Living Energy No. 11 December 2014 Living Energy No. 11 December

3 Energy Management P ower generated from renewable energy sorces, sch as wind, sn, and water, is not only increasing stability demands on grids, it is making them more complex: The once linear path of power from the prodcer to the ser is becoming a power matrix of mltilayered systems, with dispersed renewable power sorces being fed into the grid at mltiple voltage levels, often far from where the energy will be consmed. To accommodate these changes in the energy mix and varios voltage levels, transmission networks mst be bolstered to carry energy across long distances with low losses, and to maintain stability particlarly in heavily loaded AC systems. Likewise, distribtion networks mst become smarter and more capable of controlling and reglating a network with mltiple flctating infeeds. Germany, in particlar, looks set to benefit from new technologies in both network areas that will help the contry efficiently transmit high-voltage power made far from the place it is needed, and then convert and distribte it more Dispersed generation leads to fzzy load flow, creating new challenges for grid operators. efficiently on a local basis. German companies have bilt some of the world s largest offshore wind farms in the North Sea and operate large onshore wind farms in the contry s northern flatlands, yet demand for power is high in economic centers like Mnich, hndreds of kilometers to the soth. As we follow the stream of energy from way p north where it is prodced to deep in Bavaria, we see how new technologies HVDC PLUS (highvoltage direct-crrent transmission) in fll-bridge topology with DC compact switchgear, and intelligent sbstations will help enable the socalled energy transition in Germany and spport the contry in meeting its goal of sing 35 percent renewables by These technologies are making it possible to move from an energy chain to a power matrix in the transmission and distribtion grids. They help operators deal with what is often called fzzy load flow that comes from dispersed generation, sch as rooftop photovoltaics prodcing energy in low and medim voltage, or offshore wind parks prodcing high volmes in high voltage. HVDC PLUS will help German energy transmission companies provide dynamic, reliable grid access to offshore wind farms at the reqired voltage, and it can also be sed to spport the AC system at particlar nodes. HVDC is seen as the backbone for what some experts and policy makers have dbbed the sper grid, or a highcapacity transmission network for efficiently moving high-voltage power to load centers. By 2018, Germany plans to have parts of its first HVDC overlay grid in operation, which will, along with other links, eventally carry power from the North Sea to the soth of Germany. Some 6.5 gigawatts of offshore wind power are expected to be prodced in Germany by 2020, and these lines will play a crcial role in bringing that energy to load centers. An important featre of HVDC PLUS based on voltage-sorced converter (VSC) technology is its black-start capability. This significantly improves system recovery after a blackot. In 2010, Siemens bilt the first HVDC PLUS link with ndersea cables in San Francisco in the Trans Bay Cable project. Similarly, the first HVDC PLUS project with a land cable will connect the power grids of France and Spain in The projects in Germany present an additional technical challenge de to plans to se DC transmission lines on existing AC overhead towers. From North to Soth: a Vision for an HVDC Overlay Grid A segment of the project in Germany, dbbed the Ultranet, is being planned by Amprion and TransnetBW and wold back p existing AC networks by carrying energy from Osterath to Philippsbrg by overhead line (in a so-called point-to-point configration). Siemens has bid to provide an HVDC PLUS system that wold later operate with mltiple terminals. Marcs Häsler, Portfolio Manager for HVDC soltions at Siemens, says, As it develops an HVDC overlay grid, Germany is planning several mltiterminal links. The idea is to develop stepwise from point-to-point terminals to something like a radial DC grid in the next 10 to 15 years. Eventally, Germany s lines can be connected to those of other contries to create a Eropean sper grid. He adds, Right now, we are planning a sort of sper highway with one-direction energy flow and with a few terminals. The sper grid wold be an exciting way to se renewable energy in a more efficient way, to increase grid stability and develop markets for exchanging energy across borders. The technical challenge for Siemens in the Ultranet project was to enhance the HVDC PLUS system to be able to operate with overhead lines (as opposed to ndergrond cables). The answer it fond was the new Siemens HVDC PLUS technology in fll-bridge topology, which allows selective falt clearing on overhead lines in radial mltiterminal systems throgh VSC technology. Fast disconnection, a prereqisite for selective mltiterminal applications, will be made possible with 500-kilovolt DC Photo Offshore: Siemens SylWin converter station SylWin1 in the North Sea provides offshore grid connections and can transmit enogh wind power onshore to power 900,000 homes. Space-saving gas-inslated switchgear from Siemens serves as the fse box of this installation. To accommodate changes in the energy mix and facilitate the shift from several big nclear power plants to many distribted renewable sorces, transmission grids mst be bolstered to maintain stability and to allow low-loss transmission. 26 Living Energy No. 11 December 2014 Living Energy No. 11 December

4 Energy Management The Expert Voice: Rik W. De Doncker Rik W. De Doncker is the Director of the E.ON Energy Research Center (E.ON ERC) at RWTH Aachen University in Germany. He also directs the Research CAMPUS Flexible Electrical Networks (FEN) of RWTH CAMPUS Clster Sstainable Energy. He arges that there is a greater role for DC in or energy systems. Do yo see DC coming back on a wider scale in power distribtion? The main problem DC faced dring the early days of electricity was the fact that the DC transformer did not yet exist. Since power semicondctor devices were invented, engineers have been able to realize so-called power electronic DC transformers, i.e., DC-to-DC voltage converters. Since these conversion systems operate at higher freqencies than the 50- or 60-hertz AC grid, these DC transformers can be bilt lighter, thereby sing less materials (magnetic steel and copper). As the nmber of power electronic applications increases, the cost of power electronic converters is decreasing. I expect DC transformers to become more efficient and cheaper than classical 50- and 60-hertz AC transformers. How can DC transmission and distribtion help integrate renewables? DC transmission and distribtion are ideal for renewable power sorces and more distribted generation systems (e.g., small-scale combined heat and power applications), since they offer higher efficiency than 50-/60-hertz AC soltions. We shold not forget that photovoltaic systems basically prodce DC energy. The AC grid (and the AC grid code) reqires expensive converters to reglate and convert DC into AC. High-power wind trbines (above 2.5 megawatts, typically bilt offshore) se fll-converter systems to first rectify to DC and then invert back to the grid AC voltage and freqency. How do DC grids contribte to the safety, stability, and cost-efficiency of power distribtion? DC transformers can actively reglate the voltage and the power flow between DC voltage grids. Their mltiterminal capability allows DC grids to be interconnected so that the energy can be roted in the local and regional grids and does not need to be fed into the transmission grid. Classical AC transformers do not have that fnctionality. That is why the AC distribtion grid is radial, top-down. Frthermore, DC transformers intrinsically can limit overload and short circit crrents, allowing operators to coordinate short-circit protection electronically. As DC distribtion in cables and wires has no skin and proximity effects, DC systems can carry twice the power rating of AC systems, keeping the (peak) inslation voltage identical. What will the ftre transmission and distribtion grid look like? Most scenarios for CO 2 -netral electrical energy prodction in Erope show that abot one third of the installed energy prodction and power base will be installed at the transmission level, one third at the distribtion level, and the remaining third at low-voltage networks in bildings and homes, providing balancing power at each voltage level. DC distribtion lends itself better for ndergrond cables. Also, second-generation high-temperatre spercondctors (HTS) are only spercondctive with DC crrents. As HTS cables can carry very high crrents, fewer transformation levels to medim- or high-voltage levels are needed. This fact also saves costs when switching over to DC grid technology. DC cables emit less electromagnetic noise and have ltralow magnetic fields (abot one tenth of the earth s magnetic field) compared to three-phase AC wires, which also prodce alternating fields. No dobt the pblic will accept DC cables faster than AC overhead lines, de to the Not in my backyard! phenomenon. Overhead line at Oberstetten In the context of Germany s energy transition, innovative soltions are reqired at the intersection of transmission and distribtion grids. compact switchgear, a gas-inslated technology nder development that will work in conjnction with the fllbridge technology. Häsler says the fll-bridge topology provides a powerfl converter capable of reversing the polarity of the line voltage, at least for a short period of time, in order to extingish DC crrent and deionize the electric arcs reslting from lightning strikes on overhead lines. Dring normal operation, the DC voltage is like a battery in yor car. It s always constant at a certain voltage. Bt the fll bridge allows s to control the voltage electronically. This is important whenever distrbances on the DC side are to be expected, Häsler says. Offshore Gas-Inslated DC Switchgear DC compact switchgear technology needed for mltiterminal arrangements will be sed to redce the size of components in converter stations as well, and to provide safe encapslation. Marking a major milestone in innovative soltions for HVDC technology, Siemens has developed gas-inslated DC switchgear for 320 kilovolts, a typical voltage to accommodate offshore cable connections. The technology allows the size of the DC switchyard in converter stations to be redced by p to 95 percent. This is of special interest for installations on HVDC offshore converter platforms, since space can be redced from roghly 4,000 to 200 cbic meters. The technology is market-ready, and the first installation is expected by Denis Imamovic, who is responsible for gas-inslated soltions for DC at 28 Living Energy No. 11 November 2014 Living Energy No. 11 December

5 Energy Management Energy Management Intelligent sbstations can monitor and control both medim- and low-voltage distribtion grids and actively ensre stable voltage. Siemens, says: As a portfolio manager, it s my job to look to the ftre. I have to start developing prodcts now that will be needed in five years. We have developed gas-inslated 320-kilovolt DC compact switchgear for offshore applications, and now we re working on 500 kilovolts for land-based projects in Germany. According to Imamovic, the main advantage of the technology is its compactness. Compared to air-inslated technology that keeps high-voltage parts away from the grond and from each other over distances of several meters, gas-inslated technology redces the inslation distances to several centimeters. By ptting the switchgear into a compact gas-filled enclosre, Siemens redces the size of the eqipment and provides safe encapslation. We achieved gas inslation for HVDC systems by developing a new material that can withstand the DC voltage, sing resin-impregnated paper inslation technology, Imamovic says. Experts believe that companies working in offshore energy are especially interested in the compact switchgear made possible throgh gas-inslated technology since it redces space reqirements. Frthermore, new transmission technologies, partly ndergrond, are needed, becase in Erope prodction is far away from where energy is needed, and the energy mst be delivered across long distances to consmers. Gas-inslated technology has a crcial role to play within the entire system. If gasinslated technology for DC can become as matre as it is for AC, that wold be a breakthrogh. Germany, in particlar, needs space-saving soltions and transmission technologies with high efficiencies, de to the energy transition. Distribtion: Welcome to the Bavarian Capital Meanwhile, as we wind throgh the half-timbered villages of Germany s north into the castle-stdded hills and montains of the soth, we arrive at the spot where Mnich s famos indstrial brands and its eqally famos beer halls need electricity to sstain operations. There, in the Bavarian capital, energy provider Stadtwerke München is aiming to prodce enogh green electricity at its own plants by 2025 to meet the power reqirements of the entire mnicipality of Mnich, which stand at arond 7.5 billion kilowatt-hors per year, according to Florian Bieberbach, the head of the provider. This wold make Mnich the first city in the world with over a million inhabitants to achieve this goal. As part of this, Stadtwerke München is investing in offshore wind prodction in the North Sea. Wind is a good sorce of renewable energy for s becase we can make great progress toward or goal with individal projects, says Bieberbach. Once that energy arrives in Mnich perhaps throgh advanced transmission lines like the ones discssed above the local grid will also reqire pdating, if the energy from the north is to be distribted efficiently, along with the power being prodced locally with traditional methods or solar panels, biogas installations, and hydropower stations. That s where intelligent sbstations from Siemens can help by providing network monitoring, remote control of networks, and reglation of the load of energy in medim- and lowvoltage distribtion grids, withot grid expansion. Essentially, intelligent sbstations are compact medim-voltage switchgears (also gas inslated) with commnication capabilities that can detect potential overloads of operational eqipment and ensre voltage stability, said Brno Opitsch, Senior Key Expert Energy Management, Energy Atomation at Siemens. Making Germany s Energy Transition Possible Germany alone has roghly 575,000 transformer sbstations, many of which are ending their technology life cycle and are p for refrbishment or replacement to keep otage times low. Across Erope, the nmber of transformer sbstations (often called Ring Main Units) in operation is estimated at 4 million. In the USA, the nmber of pole-top stations is roghly 11 million. Replacing these is always a qestion of money and a qestion of time, says Bernd Schüpferling, the Senior Key Expert for Control Technology MV Switchgear at Siemens. Siemens offers new installations of intelligent transformer sbstations or retrofits conventional transformer sbstations with electronics for monitoring and telecontrol, making the sbstations progressively more intelligent. Photo : Siemens Level One intelligence for monitoring allows for fast falt localization in the distribtion network. The sbstation s remote terminal nit (RTU) is eqipped with a commnications connection and short-circit, earthfalt direction indicators, along with crrent sensors and voltage sensors. If a constrction crew hits a line and the associated sbstation is otfitted this way, the short-circit indicators will note the failre and commnicate it throgh the RTU. When a sbstation is pgraded to Level Two intelligence for telecontrol, a motor operating mechanism of the switch disconnectors or circit Loads to match renewable feed-in Increasing sales of electric cars like the BMW i3 are creating new demands on the grid, for instance at solar-powered charging stations. breakers is added so that hman intervention is not necessary locally at the sbstation and downtimes can be minimized. If a line is hit, reroting takes place at the control center or even in a decentralized way in the distribtion grid, making the network a self-healing system. Load flow optimization, on so-called Level Three, is an important capability in regions where lots of renewables are fed into the grid, since it can prevent energy losses and maintain stability. Featres inclde reglation algorithms for reglated distribtion transformers. Siemens intelligent transformer sbstations are designed holistically from end to end, with a focs on compatibility, standards, and redced size. Or application starts at the bottom with the switchgear, inclding the motors, the IEC sensors, the commnication, and all the eqipment for the control center, says Schüpferling. With a complete Siemens soltion, or cstomers know that all components are compatible and optimized for working together. In addition, de to the standards to which the technology is designed, operators have fll data compatibility at all levels. Opitsch says, If yo once enter a parameter, for instance for the RTU, the same parameter can be sed 30 Living Energy No. 11 December 2014 Living Energy No. 11 December

6 Trning Point Germany s Shift to Renewables Germany s energy transition, its move to increase the amont of renewables in the German grid, experienced fits and starts as the contry s capacity for generating renewable energy was expanded rapidly over the past decade. After the nclear accident at Fkshima in 2011, Chancellor Angela Merkel sped p plans to phase ot nclear plants. The last shtdown is planned for Looking ahead, some consmers are worried abot the costs they carry for the energy transition throgh a renewable energy srcharge. Still, by 2022, the goal is for Germany to se 35 percent renewables. Some highlights: Germany fonds the Federal Environment Agency. Global oil prodction throttled; the government promotes energy efficiency with reglations for maximm sage amonts. A key stdy says that Germany cold make an economically sstainable transition from fossil and nclear fels to renewables. Unlike other Eropean contries, Germany completely opens p the retail electricity market to competition Scheme annonced to spr demand for solar roof panels. Fel-efficient and clean cars get a boost de to an incremental tax on gasoline. The Renewable Energy Act (EEG) goes into force, garanteeing preferential prices to prodcers of renewable energy financed by end sers of electricity. Plans are sealed to decommission nclear plants in Germany ntil roghly Germany s Network Agency takes over as the reglator of the electricity and gas markets. The EEG is amended to improve conditions for offshore wind power, among other points. Chancellor Merkel, who had in 2010 said she wold extend the life of some nclear plants, reverses that position. The contry instead speeds p the phaseot of nclear power, with plans for the last shtdown in In the first part of 2014, a particlarly snny period, Germany s share of renewable energy in the grid was 31 percent. Snset for Biblis The nclear plant at Biblis in Hesse, Germany (above) was closed down in March Using the electric generator as a motor (rotating compensator/phase shifter), it contines to feed reactive power into the grid in synchronized condenser operation for grid stability. at all levels from the sbstation to the controller. This seamless engineering saves costs. With arond 575,000 transformer sbstations in Germany, saving one hor per sbstation is a lot of savings. Netze BW: One Operator s Experience Netze BW, a distribtion network operator in Germany recently signed a contract to modernize the distribtion grid in the Niederstetten area of the state of Baden-Württemberg to accommodate the increasing amont of renewables being fed into the grid and improve stability. It is installing a distribted grid area controller (also called a regional controller) from Siemens in the Nieder stetten sbstation, which is based on a Siemens Sicam energy atomation system that controls voltage and falt management, and provides the commnications connection. In case of a falt, the system can restore affected grid sections withot hman intervention, acting as a self-healing system. Netze BW is eqipping nine secondary sbstations located at the most important nodal points with fll energy atomation technology and five sbstations with voltage measrement systems in the dead-end feeders to monitor the network. Voltage management is made possible sing two medim-voltage in-phase reglators, which inclde power qality measrement on the primary and secondary sides. These are installed for long-range voltage control. abler for Germany s energy transition. The sbstations are market-ready at a time when two trends have converged: Not only is demand for intelligent transformer sbstations high to integrate renewables in the grid and replace aging technology advances in telecommnications and electronics have made the technology faster and allow for more cost-effective transmission of monitoring and control data as well. Withot intelligent distribtion networks, Germany s move to renewables wold stall, not only de to grid instability from the overcapacity of green energy, bt also de to the sheer cost of expanding the physical grid and the large amont of disrptive constrction that wold be needed in commnities. Frthermore, it wold be impossible to implement The voltage controllers receive their tap change commands from the distribted grid area controller, based on the distribted voltage measrement in the medim-voltage grid. Martin Konermann, the technical head of Netze BW, says, Germany s energy transition will take place in the distribtion networks. We want to make the transition possible withot hge costs and withot a loss of energy secrity. This project will make a big contribtion to these goals. Looking Forward: New Load Demands Reqire Intelligent Sbstations Indeed, intelligent sbstations like the ones being bilt and tested in Niederstetten are seen as the ftre of energy distribtion and as a key ennew-generation storage (see separate article in this isse on page 36). In Germany, intelligent sbstations are a game changer, says Opitsch. Looking forward and otside of Germany, demand for renewable energy is increasing rapidly for a variety of reasons, sch as a psh by Eropean leaders to become energy independent and select incentives to boost consmption of green energy (after years of incentives to spport prodction by individal consmers, or prosmers ). In Norway, for instance, the government s tax regime to boost sales of electric cars and penalize the prchase of traditional ones is creating new demands on the grid. Opitsch says, It s the conterpart to integrating renewables. Now we ve got new load demands, since most drivers want to charge their cars at the same time when they re home from work in the evenings. Schüpferling smmed p the otlook for intelligent transformer sbstations. Ten years ago, we saw small pilots and installations of intelligent featres for sbstations. Bt now many factors have come together. Renewables are being prodced in high volmes, operators know something mst be done to integrate them into the grid more efficiently, and the technology is now available as an off-the-shelf indstrial soltion. These trends are very promising for Germany s energy transition. p Rhea Wessel is an American freelance writer based near Frankfrt, Germany. Her work has appeared in The New York Times and the Wall Street Jornal. 32 Living Energy No. 11 December 2014 Living Energy No. 11 December