The promise of big returns from small scale energy production reported in last month's NSS has prompted readers to request more information about microgeneration of electricity using wind turbines. Evoco Energy’s Fraser Marwick is happy to provide it.

The microgeneration market – and small scale wind turbine technology in particular – is geared for growth. That is not surprising when you consider the Evoco 10, our next-generation 10kW small-scale wind turbine, is capable of producing an energy yield worth up to £14,000 a year, potentially delivering payback on the initial investment in less than four years when the turbine will normally continue generating for at least 20.

Microgeneration is defined as any technology connected to the electricity distribution network with a small scale capacity. Recent estimates put the number of microgeneration installations already working in the UK at about 100,000. More than 14,000 of them are small-scale wind systems.

Also known as ‘distributed wind’ and ‘microwind’, small scale wind turbines are engineered to turn free wind energy into electricity efficiently.

How much a wind turbine can contribute to cutting your bills depends how much electricity you use, but a 10kW small-scale wind turbine is capable of producing a verified energy yield worth up to £14,000 a year to landowners in rural areas.

Crucially, microwind turbines do not interfere with livestock rearing or crop growth and can be deployed on a rural site as small as one acre, provided that the proposed site is exposed to the prevailing wind.

As with large-scale developments, small-scale wind generation has initially seen slow uptake, hampered by the disappointing performance delivered by early turbine designs of uncertain quality that were often installed in locations of poor wind resource.

All this has changed in 2011 and beyond, as the small scale wind industry welcomes the Government’s twin policies known as the ‘Microgeneration Certification Scheme’ (MCS) and ‘Clean Energy Cashback’.

MCS is an independent UK quality assurance scheme designed to provide objective reassurance to consumers about the safety, reliability and generation performance of microgeneration technologies, and the competence of those who install them.

Certifying electricity-generating technologies such as photovoltaic (PV) and micro-hydro, as well as microwind turbines, MCS is a mark of quality for manufacturers, whose designs must undergo a stringent series of performance, durability and safety tests by independent engineers.

In January this year, the first small scale wind manufacturers finally achieved the necessary requirements and those looking into wind generation can now be assured of the robustness of products bearing the MCS accredited logo.

In a bid to make choosing a reliable microwind turbine easier, the list of small scale wind turbine designs available on the MCS website was culled at the beginning of the year, from more than a hundred to less than 10 designs that are fully-accredited.

Only MCS-accredited designs are now eligible for Clean Energy Cashback payments, also known as the Feed-In Tariff Scheme (FIT), which was announced last year as a sister policy to MCS.

The scheme provides a tax-free payment for every kWh generated by small scale renewable energy generators. The schedule of tariffs, which are not funded by the Treasury but by a general increase in electricity prices, has been devised by the Department of Energy & Climate Change (DECC) to allow small scale generators to achieve percentage returns that compete with multi-million pound, megawatt-scale renewables projects.

The FIT has changed the equation of microgeneration from mitigation of personal carbon footprint – ie customers prepared to pay a premium for energy for the greater environmental good – to simple return on investment. This has dramatically broadened the appeal of small scale renewables, which can only be good for the environment.

Of all microgeneration technologies, solar thermal and photovoltaic have experienced the highest levels of adoption to date, largely due to the relative ease of installation. There were around 160,000 cumulative deployments by 2009, according to figures from AMA Research.

However, a recent announcement by DECC suggests that FIT will soon be re-focussed on the technologies that deliver the greatest carbon benefit for the money being spent. This is likely to favour small-scale solar and distributed wind power.

Despite the much greater potential return on investment, distributed wind power has taken longer to replicate the rapid growth solar has seen in the past year.

The extremely stringent MCS testing regime required of small scale wind turbines has meant that although the FIT for wind was announced in April 2010, it was only at the start of this year that the first eligible, MCS-accredited turbines became available.

Due to their higher generation capacity per pound spent, wind turbines require less assistance under the FIT scheme.

Currently, medium scale solar photovoltaic technology is rewarded with 32.9p per kWh generated while small scale wind generation receives 28p per kWh. Despite this, wind power can still offer investors the greater return.

For example, an investment of £45,000 in a wind turbine installation can deliver about 31,000kWh of electricity a year, earning approximately £12,700 from the Feed-In tariff. A photovoltaic system of a similar price could produce roughly 16,000kWh per year worth approximately £5,800.

The British Isles are ideal for wind turbines as it is said that 40% of the wind in Europe blows over them.

Yet people going into wind-powered electricity generation must be particularly cautious with regard to turbine size and siting, given the disappointing experience of some early adopters of the system, which arose from poor siting, untested technology and uncertain performance.

Although some suppliers claim otherwise, small-scale wind turbines are not generally suitable for deployment in urban conurbations, due to the general lack of usable wind in most cities.

Furthermore, rooftop installation is not generally recommended. Due to the turbulent and difficult-to-harness wind conditions that exist directly above a building, rooftop wind turbines can generate significantly less electricity than anticipated.

The ideal site is an open rural setting, free from obstruction. Alternatively,  the sails need to be 10 times the height of the nearest obstacle. There should also be a minimum separation distance of around 150m to neighbours.

Ideally, the turbine is mast-mounted and facing a prevailing south-westerly wind. The UK average wind speed is around 5.6m per second, and this wind speed or better is usually perfect for generation.

The available power in the wind increases in proportion to the cube of the wind speed, so small changes in wind speed can make a significant difference in the electricity generated and, therefore, income.

If you are in any doubt about the local wind resource, particularly at the lower end of the scale, it is worth asking an MCS-accredited installer to monitor wind speeds and frequency at a proposed site before committing to purchase.

Having decided the location is right, noise emission planning can be a thorny issue, although a typical small scale wind turbine 150-200m away from a dwelling will not disturb the occupants.

Permission is also usually required from the local electricity company to connect all but the smallest turbines to the grid.  Many larger turbines require three-phase power, but some can also connect to single phase. With single-phase power distribution widely used in rural areas, adopters must ensure they choose a compatible wind turbine design, as it is usually more costly to upgrade the electricity supply to a three-phase system than to choose a turbine model that can be connected to single phase.

Aside from siting and permissions, choice of small scale wind turbine design is another important factor.

Selecting a product designed to BSEN 61400, the small wind designation, tested under the MCS scheme ensures the chosen turbine meets stringent safety standards.

Leading turbine producers often design-in multiple safety systems to further increase both the safety of people and the life of the installation. These include:

• Automatic furling turns the rotor blades out of the wind if speeds get too high.
• Passive pitch control adjusts the angle of the rotor blades to shed excess wind if the power output becomes too high.
• Manual braking or pitch control can be engaged from the ground to prevent the rotor turning.
• Braking resistors slow the turbine in high winds by increasing electrical load on the generator.
• G83 compliant ‘anti-islanding’ protection prevents power generation during grid failure to protect the safety of those working on the line to restore power.

When correctly sited and specified, a small scale wind turbine will deliver an excellent return on investment for businesses. With regular maintenance, accredited small scale wind turbines have a design life of 20 years or more, so your investment will continue to pay off well into the future.

The UK’s wind resource represents an opportunity for an economic boom comparable to the exploitation of North Sea oil in the 1970s, but with the added advantage that wind, unlike oil, is not likely to run out anytime soon.