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PublicWind Energy in Agriculture
In recent years there have been significant advances in the development of wind turbines and in the regulations governing the generation and sale of electricity within the UK. Here we hope to answer some of the many queries we receive from farmers, horticulturists and smallholders - generally, anyone interested in developing wind energy for domestic use. There are two basic systems possible for using wind turbines to generate electricity, grid-connected or stand-alone. Which one will suit you best is very dependent on your individual circumstances. Grid-connected systemHere the output of the wind turbine generator is directly connected to the existing mains electricity supply. This type of system can be used both for individual wind turbines or for wind farms selling (exporting) electricity to the National Grid. If for export, such a wind farm would not directly serve the electricity needs of the farmer, but would be a business in its own right involving the generation and sale of electricity. A grid connected wind turbine or turbines can be a good proposition if your consumption of electricity is high. Then the energy produced by the wind system can be used to reduce the energy taken from the grid. The value of avoided electricity purchases is generally significantly higher than the value that can be obtained from exporting power to the grid. When a wind turbine connection to the mains supply is made it has to be approved by your local Regional Electricity Company. They will insist on the connection being to a high technical standard and therefore cost, incorporating power import and export metering and approved electrical protection equipment. They may also limit the size of the wind turbine that may be connected in a particular area depending on the loading of the electrical distribution system in the vicinity. For this reason it is easier to obtain a grid connection if the local grid is generally reliable and not overloaded. For small wind turbines the cost of grid connection can be a substantial part of the total project cost. For this reason grid connection is generally a better option with larger wind turbines - usually 60kW or above. Stand-alone systemsSmall wind turbines are available which are generally used for generating electricity for charging batteries that can be used to run small electrical applications, often in remote parts of a farm where it would cost a lot to run cables from a mains power supply. Typical applications are electric livestock fencing, small electric pumps, lighting or any kind of small electronic system needed to control or monitor remote equipment, including security systems. The most common sizes of small wind generators are about 50W in a 12m/s (24 knot) wind; such a machine has a rotor about 900mm in diameter. These can be easily installed on a 'DIY' basis. Typical useful output would be in the order of 0.5 to 1kWh per 24 hours, depending on the windiness of the site. Machines typically of 250W, 1000W or larger are also available. These deliver more energy but require proportionately greater battery capacity and hence are more costly. Water pumpingWind pumps are also available. These are mechanical devices that use a multi-bladed wind-vane to drive a piston pump located down a borehole or well. These were once a common sight in the countryside and are still widely used in some countries like Australia and the USA. At least two UK manufacturers still produce wind pumps of this kind, as do a number of overseas suppliers. The technology is distinctly 'agricultural' and robust; wind pumps if properly maintained have been known to run reliably for many decades. It is also possible to obtain wind-electric pumping systems in which a wind turbine generates electricity to power a submersible electric pump; this technology is relatively recent. It should be noted that wind pumps require a storage tank, typically of about 3 days supply, to ensure availability of water at times when there is little or no wind. Siting A Turbine
The electricity produced by a wind turbine over a year depends critically on the annual mean wind speed at the site - for example, a site with 10% higher annual mean wind speed than another produces more than 20% extra energy. Sites only a hundred metres apart can be significantly different. The ideal site is on a smooth and exposed hill top or rise, clear of any obstructions such as trees or buildings within a few hundred metres, yet not so far from the farm or electricity connection that the cost of underground cable is excessive. To assess the average wind speed at a particular site, it is possible to hire a mast and monitoring equipment. Consultants and developers may be able to suggest possible hirers of equipment. Several months of data at least are required to achieve an accurate figure - the longer the better. The local planning authority may impose further restrictions on siting, depending on the expected noise output from the turbine, and its appearance in the landscape. Depending on the location and the height of the turbine, it may not be necessary to get planning permission if the equipment proposed is purely for agricultural purposes for use on agricultural land, but you are advised to contact the planning authority anyway. Wind turbine manufacturers, of large and small systems, will be able to advise on all aspects of siting. EconomicsOnly general principles are stated here, as the situation can change rapidly. Wind turbine manufacturers will be pleased to provide detailed calculations, and in some cases may guarantee a minimum annual output. However, you should also be aware of available grants and the effect on your rates bill. At the time of writing, grants for energy equipment for rural diversification are not available centrally from DEFRA but some may be administered by local branches A not insignificant operating cost is the payment of rates. Uniform Business Rate is generally payable on a formula valuation basis related to the rated power of the turbine. In England, this is £5 000 per MW, at 41.6 pence in the pound, which equates to £2.08 per installed kW. In Scotland, £5 000 per MW at 45.8 pence works out at £2.29 per installed kW, and in Wales £2 000 per MW at 41.2 pence gives £0.82 per installed kilowatt. These rates apply to new projects. Existing projects should have reduced payments, but 'Transitional Arrangements' are applied to limit the percentage change in any financial year. England, Scotland and Wales all have different arrangements. Valuations have not changed in Northern Ireland. Contact your local authority for more information. If the electricity is consumed entirely on your farm's premises, it may be that no rates are payable. Wind turbine manufacturers will be able to advise you. If you lease the use of your land to a wind farm developer it would be normal for the developer to take responsibility for any rates which will arise. If some of the electricity produced is to be used directly on the farm to produce heat then, for a fair economic comparison, the production cost should be compared with the cost of heat from oil or gas fired heaters, which is less than the cost of the same heat produced from mains electricity. Possible usesIsolated FarmsIsolated farms not connected to the national electricity grid can make use of wind power for a variety of purposes including domestic electricity, water pumping or even in some cases heating. The correct choice of technology in such situations is a specialised task depending on many factors, and so far as wind turbines are concerned particularly the energy requirements (power levels and spacing of end-uses) and the wind regime. In some cases separate small dedicated power sources applied to each application will offer the most cost-effective solution, while in others a centralised power system possibly including a wind turbine operating in conjunction with a diesel generating set may be best. The BWEA may be able to suggest sources of specialised technical advice for those wishing to investigate the possibility of using windpower for isolated farms not having any mains electricity supply. See also Centre for Alternative Technology publications. Grid-connected turbines: buying your ownIf the farm is already connected to an electricity company's 415 volt three phase network, then the wind turbine can be also connected. There should be no connection to other electricity consumers between the farm and the electricity board's transformer. The wind turbine will absorb some 'reactive power' from the grid when it is generating, and this will be charged for by the electricity company. Grid-connected turbines: hosting a wind farmDepending on circumstances, it may be that the most attractive option is to enter into an agreement with a wind turbine manufacturer or other organisation to allow them to install several turbines - a 'wind cluster' or 'wind farm' - on your land. A small fraction, typically 1% or less, of the land is taken up by the turbines and associated access roads. There will also be some disturbance during construction and maintenance. In return, you get a regular income, either a fixed sum or a percentage of the value of the electricity sold, and you avoid any responsibility for maintaining the turbines. Alternatively the farmer can act as the developer. In any case the farmer is well advised to make an independent assessment of the sites potential, and in particular evaluate the expected long term wind resource. This puts the farmer in a much better position to negotiate with would-be developers. The BWEA understands that if a wind farm is built on a 'set-aside' land then only the area of land actually occupied by the turbines - or the area of land that can no longer be cropped - plus any additional access roads, not the whole area of the wind farm, is excluded from the 'set-aside' scheme. Issues such as these need to be included in the leasing arrangements when a Third Party developer is involved; clearly such issues can be complex and it is important to retain professional advisers to assist in making any such arrangements. The Renewables ObligationThe Renewables Obligation provides market stimulation for all forms of renewable energy by requiring all electricity supply companies to buy a proportion of their electricity from renewable sources. This is a valuable source of income for people operating wind farms. Follow this link to find out more about the Renewables Obligation. A farmer having lots of wind-swept land, such as moorland for example, might consider approaching wind farm developers. They will determine if the local wind regime is adequate for commercial wind electricity generation, and if so what kind of scheme is most suitable, if the farmer were to rent them the space to install a cluster of wind turbines or even a small wind farm. This would avoid the farmer having to get involved to any great extent in the technicalities of wind farm planning as the developer would take the initiative. Further InformationUseful Addresses
Useful publications
You could also contact your local NFU branch, electricity company, planning authority or the local ADAS office for further information. A list of wind turbine manufacturers is available from the National Wind Turbine Centre, NEL, East Kilbride, Glasgow G75 0QU. The Met Office, London Road, Bracknell, Berkshire RG12 2SZ can sell you either raw wind data or summary data for your nearest meteorological station. Alternatively, if you know your Ordnance Survey grid reference, you can get an estimate of the annual mean wind speed at that location using the UK wind speed database. The BWEAThe BWEA sometimes exhibits at the Royal Show and welcomes enquiries from farmers at that event. The BWEA has organised two successful events on wind energy on farms, jointly with the RASE, and hopes further such meetings may be organised in the future. The BWEA publishes a series of factsheets on wind energy, similar to this one. These are listed at Information on wind energy. If you would like to receive any further information, please write to the BWEA enclosing a large SAE. AcknowledgementsThis factsheet has used information from 'Wind Generators on Farms' (February 1984), produced by Bob Pringle at the North of Scotland College of Agriculture. The BWEA also wishes to thank J S Robertson (Welsh Office), W G Stevenson (Scottish Hydro-Electric), Tom Buchanan (Vestas - Danish Wind Technology) and W M Somerville (Windharvester Ltd) for their help and co-operation. The factsheet was further updated by Gareth Ellis of ADAS, Silsoe and by Peter Fraenkel of IT Power Ltd. |
