Contents
The generation of energy in Germany is still primarily dominated by fossil and nuclear fuels. In future, however, electricity obtained from wind, water, biomass, the sun and the Earth’s interior will gain in importance, helping to reduce further the negative environmental consequences of using coal, natural gas, oil and nuclear fuels and lowering our dependence upon finite resources and energy imports.
By increasing the exploitation of renewable energies, however, and particularly of wind energy, which is highly weather dependent, new challenges arise both for the structure and operation of the electricity grid and as regards the adaptation of conventional power stations. The fact that a proportion of Germany’s power stations will have to be renewed over the coming decades provides the scope necessary to design and implement these measures.
Political and economic energy decisions have a medium to long-term impact and must be prepared strategically. Bearing this in mind, research regarding “Planning of the Grid Integration of Wind Energy in Germany Onshore and Offshore” (the dena Grid Study) was therefore carried out under the direction of the Deutsche Energie-Agentur GmbH (German Energy Agency - dena). The study analyses the impact on the electricity grid and the conventional power pool in Germany if the use of renewable energy sources (RES), and particularly wind, is increased, and offers solutions for the integration of these sources. The key results are described below.
Onshore. The dena Grid Study first discusses the expected development of onshore wind energy for each region in Germany until the year 2020. To this end, all areas shown in the regional planning programmes of the Länder and the regions (regional and zoning plans) as suitable for the use of wind energy were evaluated. These wind energy development forecasts incorporated information on the medium area required by a wind farm, uncertainties as to the availability of the designated areas and possible restrictions resulting from the wind farm approval process, as well as assumptions regarding the corresponding time frame and the extent of the repowering projects (the replacement of old power stations with new).
Offshore. The fundamental feasibility of the wind energy projects applied for in the North and Baltic Seas was evaluated on the basis of the following parameters: Status of the approval procedure, conflicts of use, proposed technology and location (distance from the coast, depth of water). The timeframe for the individual projects was based on planning data for the environmental impact analysis, planning permission, pipeline planning, technical planning, financing, delivery dates and construction phases. The result showed that offshore wind farms will mainly be built in the North Sea (see Table 1). Capacities of 9.8 GW are expected by the year 2015 and of 20.4 GW by 2020.
| Installed wind capacity in Germany, in GW | |||||
| Year | 2003 | 2007 | 2010 | 2015 | 2020 |
| Onshore | 14.5 | 21.8 | 24.4 | 26.2 | 27.9 |
| North Sea | 0 | 0.4 | 4.4 | 8.1 | 18.7 |
| Baltic Sea | 0 | 0.2 | 1.0 | 1.7 | 1.7 |
| Total | 14.5 | 22.4 | 29.8 | 36.0 | 48.2 |
Table 1: Development of installed wind energy
in Germany to 2020 in gigawatt (GW)
The development of the other renewable energies was evaluated on the basis of selected third-party analyses. In total, renewable energies with a total capacity of 47.3 GW can be expected to be installed and generate around 120 TWh electrical energy by the year 2015. This corresponds to 20% of gross electricity generation (see Diagram 1).
Diagram 1: Development of electricity generated in Germany from renewable energy sources until 2015
The onshore and offshore wind energy development forecast assumes that the political and economic setting will generally be positive. If this should change, the increase expected for the use of renewable energies will take longer. This is particularly true of the development of offshore wind energy, as the forecasted development timeframe is ambitious, particularly where the following factors are concerned:
Onshore grid upgrade and extension. The regional concentration in the development of wind energy will result in a strongly altered load flow in the German grid and regional bottlenecks will occur. These can, however, be eliminated by upgrading and extending the grid (see Diagram 2):
These grid construction measures would extend the existing interconnected network by a total of 850 km or around 5% by the year 2015.
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Diagram 2: Extension of the German electricity grid by 2015 |
By 2010: 460 km
By 2015: a further 390 km
Caption
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The cost of adapting the electricity grid (380/220 kV) to the increased amount of wind energy being fed into the system by 2015 amounts to a total of Euro 1.1 billion.
Security of Supply. Dynamic grid analyses have shown that certain faults can result in large-scale voltage drops and critical grid situations. If, for example, a regional voltage drop of more than 20% were to occur as a result of the three-pole short-circuit of a busbar, those wind turbines which were taken into operation before 2003/2004 and are therefore governed by the Grid Codes in force at that time would have to disconnect from the grid. These additional disconnections would worsen the critical grid situation and could result in a sudden loss of generation of over 3,000 MW. This value exceeds the primary control reserve level maintained by UCTE (Union for the Coordination of Transmission of Electricity) to compensate for short-term power station failure and could thus put the reliability of supply in the German and European interconnected network at risk.
In principle, technical measures exist to solve this problem both for the grid and for wind turbines, but a detailed examination of their use and coordination is still outstanding. Only if such solutions can be implemented in good time can the forecasted development of wind power be completed by 2015 without lessening the security of supply. The measures include voltage-supporting devices such as phase shifters, the technical adaptation of old wind turbines built before 2003 to the standards of the new Grid Codes, an accelerated repowering of wind farms and the further enhancement of the Grid Codes.
Grid extension and conventional power stations. The extension of the transmission network will also have an influence on the geographic distribution of the conventional power stations still to be built. The reason for this is that wind energy dominates a high percentage of the northern German transmission capacities in periods of strong winds. In such periods only a small portion of the grid is available for the transmission of electricity from conventional power stations. When new, fossil-fired power stations are planned either for new northern locations or as replacements for closing nuclear power stations in the north, a competitive situation arises between wind energy and the new power plant capacities. New transmission capacities can neutralize this congestion.
Exchange of energy with neighbouring countries. On a few days in the year and under certain conditions (strong winds and low loads) excess electricity is generated in Germany. When this happens, a larger amount of electricity must be sent abroad. Large-scale power generation from wind energy converters in Germany considerably impairs the reliable operation of the grids in neighbouring countries. As a result, cross-border interconnectors and transmission lines in border areas are operated close to their n-1 reliability limit at weekends with strong wind conditions and during low-load night-time hours. Regulations need to be introduced by UCTE regulating the temporary, excessively high exchange of energy between its member countries.
The level of additional electricity exports resulting from wind energy was assessed in the grid study. Depending on the underlying assumption, these will amount to between 1 and 7 TWh/a in 2015. In comparison, the total energy exchanged by Germany in 2003 amounted to approx. 26 TWh/a. The development of wind energy will therefore make only a low contribution to the total volume of energy exchanged by Germany.
Contribution to guaranteed capacity. The wind power capacity credit describes how much of the total installed wind power capacity can be considered guaranteed for the coverage of maximum seasonal load. The analyses assume that the supply of energy is 99% reliable. In Germany, the maximum seasonal load occurs during particularly cold periods. The capacity credit thus describes how much of the conventionally generated power is not needed as a reserve in the long term to guarantee the supply of electricity.
By the year 2015 the total installed wind power capacity will have increased to 36 GW. A total of 2.2 GW of this capacity can contribute towards the guaranteed capacity for coverage of maximum loads. In other words, the installed capacity of the conventional power stations in 2015 can be reduced by 2.2 GW as a result of the development of wind energy. Additional power stations are not needed as a reserve. Sufficient capacities will be available from the conventional power station to offset the limited contribution of wind energy to the coverage of maximum loads in 2015, but these will be exploited to a far lesser degree due to the increased use of wind energy.
In addition, the installed capacity of the conventional power station will drop by a further 3.5 GW as a result of the development of non-intermittent renewable energy sources (biomass and geothermal energy).
Regulation and Reserve Power. The amount of regulation and reserve power provided by wind depends directly on the accuracy of the wind forecast. The greater the forecast deviates from actual input, the higher the amount of regulation and reserve power required. Sufficient positive and negative regulation and reserve power must be available at all times to compensate in the short term for unexpected changes in wind energy input. A basic differentiation is made between primary and secondary power and between minute and hourly reserves.
Previous experience with the provision of energy from wind turbines in a wide area network has shown that influence on primary regulation tends to be low. This could, however, change once very large wind parks have been connected to the grid and the interruption output after a simple fault situation exceeds the output of large thermal power plant. Similarly, switching a very large, regionally concentrated wind farm off when wind velocity is high could in principle make additional primary and secondary regulation necessary.
The secondary regulation levels to be maintained were not examined explicitly in the dena grid study. It was assumed on the basis of previous experience, however, that deviations due to inaccurate forecasts could also be compensated for without additional secondary regulation.
In contrast, the need for minute and hourly reserves will grow as wind energy increases. According to the study, an average of 1.2 GW of positive reserve power had to be available one day in advance in 2003. The maximum requirement was 2 GW. In 2015, the average reserve power required will rise to 3.2 GW, or 9% of the installed wind capacity. The maximum level will amount to 7 GW. As the provision of wind energy continues to be developed, the need for negative reserve power can also be expected to rise. In 2003, an average of 0.75 GW had to be available one day in advance, while maximum levels of 1.9 GW were reached. In 2015 these values will rise to an average of 2.8 GW (8% of the installed wind capacity) and a maximum of 5.5 GW.
Calls on reserve power. In addition to the capacity which must be maintained to compensate for inaccurate wind energy forecasting, more reserve power will be called on as wind energy is developed. The call on positive reserve energy will rise in total from around 2.1 TWh/a in 2003 to 5.6 TWh/a in 2015. 42% of this will come from hourly reserves and 58% from minute reserves. The wind-related call for negative minute reserves will rise from 0.6 TWh/a in 2003 to approx. 2.3 TWh/a in 2015. Reserve energy will mainly be provided from pumped storage power stations.
Generation of electricity in the conventional power station. On the one hand, wind energy can replace electricity from conventional power stations which are being closed down due to age or to the phasing out of nuclear energy. On the other, it will also supplant electricity generated by existing, conventional power stations if their output has to be reduced due to the input of wind power which has precedence under the priority regulation for renewable energies (EEG). The dena grid study uses three scenarios to examine what happens when conventional electricity is replaced and supplanted by wind energy (see Diagram 3).
Diagram 3: Change in installed capacity of fossil-fuelled power stations
from 2003 to 2015, with and without wind energy development
These economic analyses show that changing the fuel mix in fossil-fuelled power stations is dependent upon the development of fuel and CO2 certificate prices. The development of wind energy will merely strengthen or weaken the characteristic trends. In all scenarios the development of wind energy means an increase of 20% to 30% in the installed capacity in gas turbine power stations between 2003 and 2015 compared to development without wind energy.
Diagram 4 shows the changes to be expected in power stations by 2015 as against 2003 if the use of renewable energy sources is increased. It is firstly noticeable that the phasing-out of nuclear power can be compensated for in all scenarios by an increase in renewable energies. The way the conventional power station is used depends on price movement for natural gas, and for lignite or coal (including CO2 certificate).
It can be seen that in all scenarios the development of wind energy will guarantee that carbon dioxide emissions from electricity generation will either remain constant or even fall by the year 2015, despite the phasing out of nuclear energy. The development of wind energy will thus contribute to the mitigation of climate change and to resource management and will help to reduce our dependency on fuel imports.
Diagram 4: Changes in power stations between 2003 and 2015
Caption:
These analyses of Germany’s power stations show that by the year 2015 renewable energies could meet around 20% of the country’s energy requirements, and at the same time reliably replace 5.7 GW of conventional power. In essence, this would mean fuel savings and a no more than minor replacement of power station capacities. The renewal of Germany’s power stations over the next few years will thus be carried out only to a (naturally) limited extent using renewable energies, whereby the current high level of security of supply (99 %) will be maintained. Wind farms, hydro and photovoltaic plants, biomass and geothermal power stations must all be combined with new, efficient and quickly regulable power stations in order to maintain the high degree of supply security in Germany.
The development of wind energy shifts the structure of the power system towards flexible power stations with a lower cost of capital and higher fuel costs. Accordingly, if wind energy is developed further, fuel costs can be reduced, the cost of capital lowered for conventional power stations and the cost of CO2 certificates avoided. These savings are offset against the costs of grid feeding pursuant to the EEG. The cost of providing reserve energy is included in these total costs, but is not listed separately in the grid study for methodical reasons. All calculations are based on an inflation rate of 1.5% p.a. until 2015.
Annual costs and savings after 2003 were calculated on this basis in the dena grid study and shown as the net additional cost of wind energy development for the years 2007, 2010 and 2015 (see Diagram 5).
Diagram 5: Net additional cost of wind energy development to 2015 compared to 2003
Caption: Basic scenario, Basic scenario + CO2, Alternative scenario
In all scenarios the costs saved by the conventional power station lie below the level of payment for additional wind energy input. However, the gap narrows in all scenarios between 2007 and 2015. Generation-related costs play a significant role in this development. The disparity will decrease if future fuel prices should exceed the values assumed in the scenarios which, in contrast to current fuel price trends, have been set at a conservative rate.
In 2007 the real additional charge for every additional kWh of wind energy fed into the grid will amount to between 6.3 and 6.5 cent, depending on the scenario. This level can be expected to fall to 3.0 to 4.3 cent per kWh by the year 2015. The total additional net charge for the additional energy generated by wind between 2003 and 2015 amounts to Euro 1.6 billion to Euro 2.3 billion, depending on the scenario.
Increase in electricity costs for household and industrial consumers. Due to the subsidization of all renewable energy sources (including wind), the cost to the private household will have increased by between 0.9 and 1.1 cent per kWh by the year 2015, depending on the scenario. This charge covers electricity costs and a grid fee for the grid extension measures described in Chapter 3. It also includes the fees provided for in the EEG for the input of electricity from renewable energy sources.
Wind development alone will cause an increase against 2003 of between 0.4 and 0.5 cent per kWh for the private household by 2015, depending on the scenario.
The privileged customer (industry) falls under the special compensation regulation of the EEG, and the development of wind energy will therefore only increase his electricity costs by between 0.03 and 0.04 cents per kWh in the year 2007, depending on the scenario. In 2015 they will have risen 0.15 cent per kWh against 2003 in all scenarios. The electricity costs cover wind energy-related cost increases in the power system including those for reserve power, minus savings in fuel costs and cost of capital. A corresponding cost reduction under the EEG hardship clause is also priced into these figures.
The integration of wind energy and other renewable energies in Germany requires a technical adaptation of the interconnected national transmission and distribution network and of Germany’s conventional power stations in the years to come. It will therefore be necessary to upgrade 400 km of existing power lines and to build a further 850 km of new lines by 2015, extending the national grid by 5%. Investment costs for these alterations required by 2015 will amount to a total of Euro 1.1 billion.
The various analyses of the power pool have shown that renewable energies could provide around 20% of the energy required by the year 2015, at the same time reliably replacing 5.7 GW of conventional energy. In essence, this would mean fuel savings and a no more than minor replacement of power station capacities. The renewal of Germany’s power stations over the next few years will thus be carried out only to a (naturally) limited extent using renewable energies. Wind farms, hydro and photovoltaic plants, biomass and geothermal power stations must all be combined with new, efficient and quickly regulable power stations in order to maintain the high degree of supply security in Germany.
The selection of technologies and fuels used in the conventional power station will be influenced by the development of wind energy only to a very limited extent. In contrast, the development of conventional power stations as a whole will be affected significantly by fuel prices trends and the CO2 certificate price. This latter is greatly dependent upon the form that emissions trading takes.
The development of wind energy is associated with additional costs. These arise mainly from the construction of wind parks and their connection to the grid and from the reduced utilization of the conventional power station together with the higher reserve power required. On the other hand, the conventional power stations will also register savings from the reduction in fuel costs. The sum of additional costs and savings estimated in the various scenarios will result in net additional costs from the development of wind energy of between € 1.5 billion and € 2.3 billion p.a. by 2015. On average, the development of wind energy in the period 2003 to 2015will result in an increase in electricity costs of approx. 0.5 ct/kWh for the private household.
The dena grid study was financed by associations and private companies from the wind energy and electricity grid sectors, plant manufacturers and the conventional power station sector together with the Federal Ministry of Economics and Labour. It was coordinated by dena. The framework of the grid study was agreed by a project steering committee. After perusal of the final report, the financing bodies have decided to commission a further report examining the development of renewable energies for the generation of electricity up to the year 2025, with in-depth studies of selected topics.
