Blowing the electricity meter backwards

25 per cent of Europe’s wind capacity can be found in Scotland – good conditions for energy companies to make some profit. Now the UK government wants the wide public as well to have a piece of this cake. A new subsidy scheme for small-scale generators of renewable energy is supposed to facilitate the installation of smaller wind turbines for communities and private households. But although Scotland offers the best conditions for residential wind turbines in the UK, if you consider the costs of wind turbines, there are only a few places where it is worth installing a turbine in the backyard or on the rooftop.

Text and pictures by Kerstin Viellehner
Video by Lisa Guggenmos and Kerstin Viellehner

Wind turbine at the Glasgow School of Art: The 2.5 kW turbine at the top of the building produces around 3000 kW a year. In a rural area this turbine could be much more efficient.

With the new renewable energy subsidy scheme for micro- and small-scale generators, a feed-in tariff (FiT) has been launched on the 1st of April 2010. This new financial support is supposed to incentivise small-scale production from solar photovoltaic, wind, hydro, anaerobic digestions and domestic-scale combined heat and power up to 5 Megawatt (MW).

In Scotland, the windiest country in Europe, especially the possibility of producing wind power on a lower scale sounds appealing. “There is a lot of excitement for smaller scale turbine projects,” says Christine McKay, Senior Policy Adviser of the Scottish Government’s Renewables Strategy and Onshore Renewables Team. “The feed-in tariff takes out the middle man and offers him the chance to saving money by producing his own electricity.”

Getting different amounts of money for different technologies

The FiT for all renewable energy sources is divided into two elements of payment:

  • The Generation Tariff guarantees a minimum payment for the electricity that is counted by the meter. This tariff differs within the renewable technologies.
  • The Export Tariff pays for the electricity, that is exported to the power grid, 3 pence per Kilowatt hour (kWh).

Generating power is paid by a fixed price per kWh – no matter if the electricity is used onsite or is exported. For wind turbines the amount of subsidy decreases with the size of the turbine. A turbine that produces less than 1.5 kW makes 34.5 pence per kWh, one with a capacity between 1.5 and 5 MW only 4.5 pence per kWh. To have a closer look at the different tariff levels, click here.

According to Dr Tim Sharpe, Co-Director of the Macintosh Environmental Architecture Research Unit of the Glasgow School of Art, the idea is that individuals can benefit in three ways: people get money for each generated kWh, they get paid for everything that is exported to the grid and additionally they can use their own electricity and can save money by reducing the electricity import from energy suppliers. “You can see your electricity meter running backwards,” he says.

The Glasgow School of Art has an own wind turbine on its rooftop and Dr Tim Sharpe has been engaged with the planning and monitoring process around this turbine. Thereof he got his expertise.

“Appropriately sited you get 5 to 8 per cent rate of return from your wind turbine,” says Daniel Borisewitz, policy manager for bio energy and heat at Scottish Renewables.

Choosing the right wind turbine

The most efficient type of a turbine: vertical axed and stand alone turbine

Generally there are two types of turbines at the moment, mast-mounted, stand alone turbines and roof-mounted ones that are integrated in the building.

However, “the classical vertical axed, mast mounted stand alone turbine is the most efficient type of turbine you can get,” knows Dr Tim Sharpe, “but therefore you need enough land to install it.”

A turbine’s capacity can differ from 100 W of the very small ones to 5 MW of ones that are already able to supply a whole community. Small systems will cost around £1,500 to 2,000, for larger systems the required amount of money is around £20,000.

According to the Energy Saving Trust, a non-profit making organization that wants to promote renewable energy sources, an average house would need a system with a capacity between 1 and 6 kW depending on size and location of the property.

How the FiT works

For example, a 6 kW stand alone turbine can produce around 7,500 kWh a year, if the site is windy enough (these figures are based on a wind speed of 5 meters per second). Considering the fact, that the Scottish average domestic consumption per meter in 2008 was 4,236 kWh, a 6kW turbine is able to power a family house.

For every kWh that is generated the owner gets according to the FiT 24.1 pence. So each year the turbine makes £1,879 – or £156 a month. With a price of about £25,000, the turbine pays off in 13 years without having exported anything. Once the installation has been allocated, the tariff remains fixed for the live time of the tariff, which is 20 years.

A 1.5 kW roof mounted turbine has an average generation of 1,753kWh. With the price of circa £6,500 and a FiT of 34.4 pence per kWh, the turbine has a payback time of 15 years.

It all depends on the siting

But no matter if the turbine is roof- or mast-mounted and no matter how many kWh it is supposed to produce in general, in the end “efficiency-wise it all depends on the siting,” explains Daniel Borisewitz from Scottish Renewables.

In comparison to the rest of the United Kingdom Scotland offers the highest potential for successful small-scale wind installations because of its relatively high wind speed. This states the Energy Saving Trust that did a one year lasting field trial of domestic wind turbines.

Nevertheless an area with average annual wind speeds under 6 meters per second (m/s) is not applicable of producing enough electricity for a satisfying cost-performance ratio. The British Department for Energy and Climate Change offers a wind speed database, where interested individuals can check if their area is windy enough.

In remote places like Scoraig wind turbines perform best.

It goes without saying that the windier a site is, the better the results. According to the Energy Saving Trust the energy content will increase eight-fold, if the wind blows only at twice speed. Turbines at a site with a wind speed average of 8 m/s produce circa 75 to 100 per cent more electricity than on an area with only 6 m/s.

Not surprisingly the best performing sites in the field trial were those with free standing wind turbines in remote rural locations.

Too much turbulence in urban areas

Turbines sited in urban areas did not achieve sufficient results because obstacles such as buildings or trees cause too much turbulence – and turbulences in turn reduce the wind speed.

“Take Edinburgh as an example. In theory there should be good wind speed but there are too many buildings and trees. To really be able to use that wind effectively, you’d have to have a 30 meter tower or something like that to get enough wind,” says Hugh Piggott.

Hugh Piggott can be called as an expert in small wind turbines. He has built wind turbines on his own for more than 30 years and teaches other people how to build them (see video below).

Dr Tim Sharpe thinks the same way: “In an urban environment you get much more complicated airflow. So the turbine needs to be robust enough to be able to tolerate that. I think if you have a house in a rural area it is probably worth putting a turbine on it, if you are in an urban area, it is probably not.”

If the efficiency is not high enough, the wind turbine takes too long time to pay off and there is no benefit of the tariff. “Well sited a turbine will give you a payback time of 8 to 10 years,” explains Daniel Borisewitz, “So only after this time you start to make money.”

With the new FiT people need to be realistic about where to install the turbine. Dr Tim Sharpe from the Glasgow School of Art: “With the grant people have got for their turbines so far, they got money anyway – no matter where it was put and how much was produced. If you want to make money now, you have to be much more concerned about that.”

A place where it can work

An example, which shows successfully the use of small scale level wind power, is a community called Scoraig in the Highlands, far away from “the rest of the world”. It is only accessible by foot or with a small boat. Because of being so remote it is also not connected to the power grid.

Hugh Piggott moved to this place in the 1970s, and began to build small wind turbines to supply his own house and the dwellings of his neighbours with electricity.

Considering the fact that stand alone turbines are the most efficient ones and remote areas the best places to install one, it is mainly the people in the rural areas that can really benefit by small wind turbines. They have enough space to erect a stand alone turbine in the backyard and appropriate wind speed with only little turbulence to make the turbine running fast enough.

“The location is terribly important and it is really going to work a lot better in rural situations. I wouldn’t say that this is something anyone can do,” says Hugh Piggott.

Besides, not having the neighbours as close to your property as in urban areas means also that one does not have to care so much about possible nuisance complaints because of noise or shadow flickers.

Criteria for wind turbines

Installing wind turbines is supposed to be allowed under the following conditions:

  • Wind turbines on buildings are not allowed to exceed 3 m (including blades) with an maximum diameter of 2.2 m or swept area of 3.8 m2
  • Free-standing wind turbines are allowed with a mast height of not more than 11.1 m (including blades). Furthermore they have to be installed at least 100 m away from the neighbour’s property.
  • Wind turbines must not be louder than 45 decibels.

For more information about wind power in Scotland, see also “Scotland’s energy sector catches tailwinds”

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