Wind energy for rural businesses

October 18, 2013 by  
Filed under Wind Energy Tips

The Northern Ireland branch members of I Agr E recently enjoyed a talk on the subject of “Wind Turbines – opportunities and constraints” by Mr Barry Meeke, Managing Director of Co Tyrone based Silverford Renewables.

His company was formed in 2009 to supply, install and maintain wind turbines.

He represents several manufacturers whose products include, amongst others, the Danish designed Gaia-Wind turbines. As the company had just completed its 24th installation of the popular 133 model much of the talk centred around it. As well as discussing the technical features of the product, Mr Meeke (a graduate mechanical engineer) discussed the environmental constraints for site approval, turbine design technology and the application of engineering skills to take a project through from planning to full service operation. He also can supply other larger turbines such as the 50kW Endurance E-3120.

Site approval

When it has been established by records or monitoring that a site is potentially suitable the process can begin. Not every site which initially looks good is feasible as wind pattern can be upset by turbulence from buildings or other nearby structures. The typical overall project timescale can be 12 – 18 months. The required planning application system will check visual appearance in relation to the site and whether the proposed turbine size is appropriate to the business. A range of official bodies and business interests need to be consulted to check how it may affect them. One of the criteria is background noise which should not exceed 35dBa at the nearest neighbour’s boundary fence or amenity space. This evaluation will include the combined effect of any other turbine operating within 1 kilometre. There are also considerations of potential interference with other installations such as communication towers, phone masts or fixed telecom links for local water pumping stations.

Encouraging renewable power generation

Most installation owners will plan to take advantage of incentives to spill excess power to the grid. These exist because of the national need to displace dependency on fossil fuel imports and the contribution from renewable energy sources is recognised by a system of Renewable Obligation Certificates (popularly referred to as ROCs) which have monetary value. Northern Ireland Power co-ordinates these locally for Ofgem (short for the “Office of Gas and Electricity Markets “which is the national regulatory authority for the UK energy market). As the payments are funded by a levy on the industry, energy customers pick up the cost. As the installation of renewable energy source capacity increases these incentives are gradually being reduced. At the time of the talk the reward rate for supply from installations under 250kWs was set four times higher.

Producers get paid to export to the grid although it still is financially best to use as much as possible of their own power on site.

Grid compatibility

Up to now the local grid has been designed for distribution and so it may not always be suitable to accept additional power inputs from generation in remote rural areas. For example, feeding in more than 20kWs on a single phase connection could upset the 3 phase balance further back. The ideal link- up location would be close to a sub station. Such connection carries a cost and some turbine owners in Northern Ireland have successfully applied for grant aid assistance for this under the Rural Development Scheme, Control systems within the grid control whether or not the quality of input from specific turbines is acceptable.

The Turbine and its technology

The main discussion centred on the popular Gaia –Wind 133. It is an established Danish sourced design optimised for average wind speeds between 4.5 and 7 m/sec targeted at the agricultural, rural residential and light industrial sectors. It has a 2 blade GRP 13m diameter rotor sweeping 133 square metre at a fixed rotational speed of 56 rpm. The large diameter rotor is a key aspect of increased efficiency compared with smaller types. It drives its marine grade generator through an 18:1 reduction gearbox. The generator is rated at 11kW for 400V at 50Hz. The nacelle and rotor weigh 900 kg and is normally mounted on an 18m tower. The large diameter 2 bladed design is said to produce up to 80% more energy than other similarly rated conventional machines.

The 133 has an integrated microprocessor with multiple sensor inputs. The data collected includes wind speed, power, voltages, currents and phase, vibration and temperature alerts.

It has 3 levels of system protection which include:-

(1) Passive stall of blades to limit power input when wind speed is too fast.

(2) The control system activating a mechanical brake in the event of wind speed exceeding 25m/s, abnormal vibration, grid disconnection or the generator overheating.

(3) Use of the manual override button to apply the mechanical brake. Centrifugally activated aerodynamic brakes within the rotor tips take off pitch by distortion when wind speed is too high.

The wind power industry works to the standards of:

Cutting in when wind speed reaches 3.5 m/sec

Cutting out when wind speed gets to 26m/sec or a 3 sec gust of 26 m/sec (56mph).

Getting the Gaia – Wind 133 turbine on site

The components, including the tower sections are modular and fit within a standard shipping container. On site, a high strength concrete raft base is cast in advance incorporating 1.5 tonnes of steel and 18 cubic metres of concrete. The sectionalised tower construction facilitates the use of a modest sized (30 t) crane. It was especially interesting to hear the engineering detail of how the structure is placed and bolted together.

Ongoing maintenance

The installations require an annual service which typically costs around £360. It includes brake pad replacement, shear bolt checking and gearbox oil sampling as well as any other fault investigation.

The speaker’s professional engineering background and his in-depth knowledge of both the technical and practical aspects of his business proved to be an ideal platform for a most interesting discussion This expanded topics including :-

Make up, design and performance of the turbine blades

Machine interaction with the grid

The operation of the protection systems during extreme weather conditions.

The chairman thanked Mr Meeke for all his efforts in preparing and delivering such an informative and enjoyable presentation.

More detail of the products and services available from Silverford Renewables is available at www.silverford.com or Tel 0845 2723502

Next meeting

The next I Agr E event is a visit, at 2.30pm tonight (Wednesday 16th October) to the manufacturing facility of Fleming Agric-Products Ltd. At Newbuildings Industrial Estate, Victoria Road, Newbuildings, BT47 2SX. The company is a well known manufacturer of machinery for agriculture and countryside care. This is a unique opportunity to see a local modern design and manufacturing facility in operation. Visitors should first go to Reception from where the tour will start.

November meeting

The November meeting will take place at CAFRE, Greenmount Campus, Antrim at 8.00pm on Tuesday 19th November 2013 when Mr Chris Eakin, Ireland Manager, Michelin Tyres will talk on the subject of “Tractor and Trailer Tyres”.

Visitors are always welcome at I Agr E meetings.

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