When talk turns to wind power, for most people the first image that springs to mind is one that consists of many huge turbines dotted across the landscape or out at sea. It is very much a large-scale vision. Yet today there is increasing interest in wind turbines that are small enough to mount in backyards and local parks, and on the roofs of houses and office buildings. Could these turbines, that in many cases look like attachments for a giant hand held cake whisk, become a big part of the energy future?

As with any nascent technology it is not an easy question to answer, but what has become clear in recent months is that they are slowly moving towards the mainstream. This has been particularly evident in the UK, with the recent move by German and European power major RWE—through its UK utility RWE Innogy—to take a minority shareholding and make a capital injection into Quiet Revolution Ltd, a small wind turbine company based in London.

Founded in 2005, Quiet Revolution has installed its flagship product, the 6kW QR5, on a number of rooftops in England. There is one located on top of King's College School in Wimbledon and a large pub chain has begun installing them as well. The QR5 is a vertical axis wind turbine, rather than the conventional one that is horizontal, and is particularly suited for local energy production in built-up areas that can be installed either on buildings or as a stand-alone turbine.

When a company the size of RWE gets involved the market certainly takes notice. And the group states that it sees the local supply of electric power to individual buildings from renewable energy becoming increasingly significant, with small wind power units on roofs making a major contribution to this goal. In this case, says Crispin Leick, head of the Ventures Division of RWE Innogy, “the purpose of our involvement is to take this promising technology towards mass production, so that it will become commercially usable.”

The potential is also underlined in two recent reports. The first is the August 2008 report from the UK's Carbon Trust and the Meteorological Office, which states that in theory small wind systems could contribute around 11 percent of the UK's electricity. On paper it is a figure that can only be described as “very significant,” though it needs to be noted that this is “could” and not “will.”
The second is from the British Wind Energy Association (BWEA) in its "First BWEA Small Systems Report" published the following month. It stated that it identified very strong annual growth for small wind turbines in terms of units installed and projected that the three previous years of interrupted growth would continue through 2008 and into 2009, with the UK retaining the mantle of world leader in small systems technology. It added that the growth is driven not just by technological improvements, but also by a realization that there are huge energy savings to be made by deploying small turbines.

There are certainly opportunities, but what both reports also highlight is the fact that challenges, barriers to development and some “unknowns” exist.
The BWEA report highlights the continuing consternation at the UK Government's lack of clear guidance to local planning authorities, which it says would assist those wishing to generate their own renewable energy. It states that in 2006 as part of the Micro-generation Strategy there was a commitment to address planning as a barrier to deployment, but industry, local authorities and consumers are still waiting for detailed planning guidance and permitted development rights to be issued. It also recently stated that it was important the Government came out with much stronger backing for the burgeoning sector.

The UK's Carbon Trust and Metrological Office report also touches on planning, but also underscores downsides in relation to the turbines being too small and inefficient to be cost competitive, as well as the issue of the optimum location.
On this last point, the study indicates that for the UK as a whole, the majority of electricity and carbon savings are available from small turbines in rural areas—four times as much as urban areas irrespective of costs, and considerably more given economic drivers. It says that turbines in some rural locations, where wind speeds are generally higher, could provide cheaper electricity than the grid, but it appears that in many urban situations, roof-mounted turbines suffer from wind turbulence and may not pay back their embedded carbon emissions.
Quiet Revolution acknowledges that in an urban or built-up environment some wind turbulence is inevitable—unless the turbine is sited well above any surrounding buildings—it says that this is the primary reason for opting for a vertical axis wind turbine as such a design doesn't require wind from a consistent direction to continue producing power.

Reducing costs, improving efficiencies, streamlining government support, grants and subsidies, and having strong regulatory and planning guidelines are obviously paramount. And with these in mind, the Carbon Trust has recommended a number of improving existing policy measures including using a criterion in any new grant schemes to measure likely carbon savings; and, having higher limits for stand-alone turbines under permitted development rights to help maximize the overall carbon savings of small-scale wind energy, given the sensitivity of electricity generation to height.

Going forward it is also important to throw in a few “unknowns.” For example, how might fossil fuel prices impact development? And will the UK renewable energy goals for 2020, which month-on-month look further away, lead to more small wind, particularly if they prove easier to build than other forms of renewable generation? It should be stressed that this is not an exhaustive list.
The overall goal needs to be stimulating the growth of more productive, lower cost turbines, and there have been some positive signs. RWE's recent investment is obviously one, particularly as it has as the scope for mass production that should bring down costs, and looking outside the UK, in the United States only recently, New York Mayor Michael Bloomberg announced that he is interested in installing wind turbines on top of the city's buildings.

As with any new technology, these goals are critical. If output efficiency is not improved, and costs remain high, small wind will be little more pie in the sky.