Increasing wind penetration National wind characteristics and power generation

Studies of wind speeds in Great Britain show that there are significant periods in an average year when demand is high and wind output over the whole country is low. In particular, a typical year would have over 1600 hours when wind-generated output would be less than 10 per cent of maximum rated installed wind-generation capacity, including 450 hours when demand is between 70 to 100 per cent of peak demand (OXERA, 2003). Although the risk of system failure is greatest when demand is at its...

What happens when the wind does not blow

Wind Speed Europe Correlation

It is a rare event when the wind does not blow in a region, and an even rarer event when a larger region is considered. Taking Europe as a whole, it has been found that averaging 51 one-year onshore time series on an hour-by-hour basis leads to a minimum generation of 1.5 per cent of the installed capacity at all times. But how will a region cope with the rare event of a lack of wind or with low wind One has to consider what occurs as more wind is integrated. Several parallel developments are...

Multimodel approach for numerical weather forecast models

A study has been performed to investigate the influence of merging different NWP models on the accuracy of the wind power forecast. Three different NWP models have been used for a day-ahead wind power forecast for Germany (see Table 5.2). All three models have been used as input to the WPMS based on the ANN method. Network training was performed with data of more than one year. A concurrent data set of seven months (April to October 2004) has been used for the comparison. The RMSE percentage of...

Patterns and variability of renewable energy availability

The availability of renewable energy varies over time, with location and with the resource being exploited. The pattern of energy availability will also change depending upon the time scale being considered. For example, tidal stream energy shows very little change in energy production from year to year or month to month however, large changes in output can occur from hour to hour. Contrast this with wave power, where output tends to change less than tidal stream at the hourly level, but there...

Backup capacity and grid energy demand requirements

Conventional generation can be considered to provide two services energy production and power capacity. If wind generation displaces conventional base-load plant power capacity by reference to capacity credit and probabilistic security of power supply standards, as described, then the provision of energy also has to be re-examined, and backup capacity to ensure energy supply must be provided if needed. The relationship between security of supply, wind penetration, plant load factors and backup...

Electricity demands

Future electricity service demands in terms of type, temperature, quantity, time and weather dependency rely on the scenario context. In this scenario, it is assumed that the demands for electricity-specific services that can use no other fuel (such as computers, communications, lighting and some motive power) will generally stabilize because efficiency gains will offset growth factors such as population. The use of electricity for heating depends upon the relative availability and prices of...

Switch OFF

Frequency (Hz) Figure 11.1 Operation of the Dynamic Demand concept Figure 11.2 Impact of Dynamic Demand control (DDC) on grid frequency with 13.8GW of wind capacity Figure 11.2 Impact of Dynamic Demand control (DDC) on grid frequency with 13.8GW of wind capacity energy capacity can be absorbed without the need for additional frequency regulation. Barrett's work in progress, reported in Chapter 9 of this volume, suggests that up to 95 per cent of the UK's electricity supply could be met from...

Demand growth scenarios with various penetration levels of wind energy by

Growth Wind Penetration

As already referred to, the problem to be faced in the future is how to accommodate high levels of variable wind capacity in a power supply system if security of supply considerations (i.e. capacity credit limitations) do not allow the release of alternative conventional generation capacity. This situation is illustrated in the results of a study for the UK Department of Trade and Industry (DTI) (ILEX Energy Consulting, 2002), in which future demands were postulated along with a high degree of...

Applications of wind power forecasting

The most important application for wind power forecasting is to reduce the need for balancing energy and reserve power, which are needed to integrate wind power within the balancing of supply and demand in the electricity supply system (i.e. to optimize power plant scheduling). This leads to lower integration costs for wind power, lower emissions from the power plants used for balancing, and, subsequently, to a higher value of wind power. A second application is to provide forecasts of wind...

The role of wind power in providing capacity

The total available capacity on a network should always exceed the peak demand met by the network, and this difference is known as the plant margin (or backup). A plant margin is required to ensure that demand will be met to a specified level of reliability as no generating capacity is 100 per cent reliable, the provision of more capacity than is needed to meet demand is essential for the long-term reliable performance of the electricity network. The size of the plant margin is related to the...

Effect of wind farm power output forecasting

Short-term forecasting of wind farm output has been worked on for more than 15 years within the wind industry (see Chapter 5 and Giebel et al, 2003). It has a function in contributing to making wind more predictable. This allows for the conventional plants to plan ahead to adjust their output appropriately. During earlier years, it was largely of interest to grid operators. More recently, the owners of wind farms have also been taking an interest for two reasons. First, in some regions they are...

Total extra costs of wind energy

The total extra costs of operating an electricity network with increasing amounts of wind are now of considerable interest due to the recent increases in the price of gas. The differences between the generation costs from wind and those from gas are narrowing, and it is quite likely that wind energy might become cheaper. The total extra costs of wind energy take into account the following extra costs associated with variability, as discussed in the previous sections extra generation costs (if...

Where are the wind resources

This chapter takes as a starting point the recent study Sea Wind Europe (Greenpeace, 2004), which identifies the magnitude of the offshore resource by country, the annual yield in gigawatt hours (GWh), the capacity in gigawatts (GW), the area occupied in square kilometres (km2), and the percentage of available area for the periods of 2003-2010, 2011-2015 and 2016-2020. A recent report by the European Wind Energy Association (EWEA, 2004) provides further material and, with earlier studies, gives...

Differences The effects of wind speed and scheduling procedures

The characteristics of wind tend to be similar the world over and the same applies to electricity networks - but there are some differences. The extra costs of reserve in Great Britain and a number of American electricity jurisdictions are similar (see Figure 2.6) but significantly higher figures are quoted for Germany. This is due partly to the way in which the electricity network is operated, and partly to the lower wind speeds that prevail there. In Germany, as well as in some other...

List of Contributors

Professor Dennis Anderson is an emeritus professor of energy and environmental studies at Imperial College London. He was formerly the Energy Adviser of the World Bank, Chief Economist of Shell and an engineer in the electricity generation industry. David Andrews is a chartered engineer, and has been Energy Manager with Wessex Water for 10 years. He has worked in the energy business for most of his professional life, specializing in small-scale power generation using engines. Dr Mark Barrett...

Wind power and backup

Concern has been expressed regarding 'backup' or the additional plant that is needed to offset the variability of renewables, such as wind power. Some authors have suggested that backup equal to 65 per cent of the installed capacity of wind power (PB Power and RAE, 2003), or even 100 per cent of the capacity of wind power (Laughton, 2002 Fells Associates, 2004), would be required to be installed in response to the development of wind power on an electricity network. One method of quantifying...

Example The Wind Power Management System

Wind power forecasting is an integral part of the electricity supply system in Germany. The Wind Power Management System developed by ISET is used operationally by three of the four German transmission system operators (see Figure 5.11). The system consists of three parts 1 the online monitoring, which performs an upscaling of online power production measurements at representative wind farms to the total wind power production in a grid area 2 the day-ahead forecast of the wind power production...

Anticyclones and largescale variability

The major questions concerning the relationships between variability of energy sources and grid power supplies occur when small-scale random local variability gives way over longer time periods to large-scale changes affecting much of the grid system supply from wind. Such large-scale variability would occur for wind and wave power when a substantial high-pressure weather system anticyclone moves in over the whole country or a large part of it and - with little or no wind - wind power output...

Hourtohour variation in output

A key aspect of variable-output renewable resources is the rate of change in power output over time. The rate of change in output of a wave, wind or tidal stream electricity generator depends upon two factors - the sensitivity of the device to changes in environmental conditions and the degree to which environmental conditions change. Nordex N80 wind turbine power function Nordex N80 wind turbine power function Figure 3.4 Power transform curve for a typical large wind turbine Consider the power...

Implications for conventional plant capacity needed

All study results indicate that for low levels of penetration, the firm power capacity displaced equals the mean power delivered by wind generation i.e. measured by the total wind generation average load factor , but decreases with increasing penetration of wind Rockingham, 1980 Halliday et al, 1983 Grubb, 1986, 1988 Swift-Hook, 1987 . This diminishing return in the value of wind capacity reflects the increasing importance of the possibility of little output from all sources of wind generation....

Reserve and standby generating capacity on the UK National Grid

On the UK National Grid system there is approximately 1.5GW of 'spinning reserve' - typically, this takes the form of a large power station that is paid to produce at less than its full output. Such a station might have four generating sets each of 660MW, giving a total output of 2.64GW, but might only be operating at 2GW with the steam boiler full but the steam valve not fully open. On request from the National Grid control centre, this valve can open and deliver an extra 640MW in 20 to 30...

Wind energy penetration levels

Although the British and Danish system operators have both stated that the limits to wind energy penetration are economic rather than technical, this has gone largely unnoticed. There is still a feeling that high wind energy penetrations will cause severe technical problems but this is simply not the case. Extra costs are incurred but these can be quantified. A recent Danish study Pedersen et al, 2006 has suggested that these extra costs reach a maximum value of around 15 MWh of wind. If...

Wind predictability

In general, wind is perceived as unpredictable but this is not strictly true. Weather forecasting techniques enable average wind speeds to be predicted with reasonable accuracy, but not necessarily the hour-by-hour variations. In some parts of the world, however, such as the Californian passes, the winds do have an established diurnal cycle, which benefits system operators. Although there are significant differences in the way in which electricity jurisdictions operate, there is a reasonable...

Security of power supply and planning margins

Historically, in the development of national electricity supply industries, the planning process has sought to ensure that sufficient spare generation capacity is available, over and above that needed to meet the maximum peak load demand, in order to account for contingencies. To do so requires having sufficient spare capacity in order to meet not only expected generating plant outages for repair and maintenance, but also unexpected events causing breakdown of plant and, thus, non-availability...

Smoothing effect

The power output of wind farms fluctuates. These fluctuations are very difficult to forecast, and even if the power output on a particular day is predicted well, the fluctuations will cause a forecast error. The larger the wind farm, the smaller will be the fluctuations and the corresponding forecast error. If many wind farms are forecast together, the forecast error decreases further. In addition, the aggregation of large regions with several gigawatts of installed capacity will lead to a...

References

Bell, K., Ault, G. and McDonald, J. 2006 'All eyes on wind', IET Power Engineer, June July, pp30-33 Boyle, G. ed 2004 Renewable Energy, 2nd Edition, OUP and the Open University, Oxford E.ON Netz 2004 E.ON Netz Wind Report Wind Year 2003 - An Overview, E.ON Netz Gmbh, Bayreuth, info eon-netz.com Grubb, M. J. 1986 The Integration and Analysis of Intermittent Sources on Electricity Supply Systems, PhD thesis, Cambridge University, Cambridge Grubb, M. J. 1987 'Capital effects at intermediate and...

Combinedcycle gas turbine generating plants

Heat Recovery Steam Vertical

CCGTs consist of a gas turbine s that produces about two-thirds of the power from the plant. A single steam turbine set utilizes the steam generated in a Heat Recovery Steam Generator HRSG to produce the remaining third. The gas turbine operates by compressing air to a pressure of about 20 to 25 bar, burning natural gas in the compressed air and then expanding this through a combustion turbine, which then drives a compressor and an alternator. Some forms of CCGT have the set of steam turbines...

Power demand and supply Daily load curves

In the British system covering England, Wales and Scotland, the total daily power demand varies between a minimum summer load of about 22.4 giga-watts GW and a winter peak above 59.4GW National Grid, 2006 . Figure 1.8 illustrates the demands during the two days, with minimum and maximum demands, respectively, over the 12-month period of 1 July 2005 to 30 June 2006, the areas under the curves representing daily energy demands supplies and the heights of the curves representing the average...