As well as bringing forward new sites in saturated markets, this technology looks likely to open up whole countries to wind energy.
Around 50% of locations with potential for wind-farm development globally are classed as low wind, with wind speeds of 7.5m/s or lower. The principal factor that has encouraged manufacturers and developers to investigate this market is that many countries are saturated with wind farms, with the best sites already developed. Low-wind turbines are therefore proving popular in southern Germany and parts of the US.
Proximity to population centres
China and India have a large number of sites with low-wind resources. In China, the government is specifically targeting low wind to mitigate the transmission problems the industry has faced in more remote areas. Low-wind sites are typically closer to the higher population densities in Beijing and Shanghai and therefore suffer less from curtailment. Almost 70% of China experiences low-wind conditions, in particular, the central and southern provinces of Fujian, Guangdong, Guangxi, Anhui, Hunan, Hubei, Jiangxi, Yunnan and Guizhou.
In 2011, the government's 12th five-year plan set a target for 20GW of wind to come from such sites, out of a total of 100GW wind it wanted to see developed. It offers a specific tariff for low wind, at CNY 0.61/kWh ($0.010/kWh) compared to CNY 0.51-0.58/kWh for higher wind-speed areas (see map, below).
More efficient turbines
Technology developments are coming on apace (see page 6). Longer blades, taller towers and smaller generators are minimising the amount of energy production lost due to the lower wind speeds. German manufacturer Nordex reports that some turbines it has installed in low wind sites are achieving capacity factors of 40%, which is a figure more normally seen offshore. However, increased capacity factors come with an increased capital price tag.
If a developer simply transfers existing equipment to a low-wind site, typically they will lose energy if nothing else is done, explains David Williams, senior renewables analyst at consultancy GL Garrad Hassan. Power curves need to be designed to maximise yield. "You're not going to catch-up entirely with a site that's got better resource, but you can minimise your additional expenditure," he says.
Juan Diego Diaz, marketing director at Spanish turbine manufacturer Gamesa, agrees that power curves are an issue. "What we are doing is trying to adapt power curves to specific sites," he says. "We have developed technology to tune the power curve and adapt it to every site and even every single position. This is the future. Advanced control systems are becoming more important day by day."
Manufacturers have been doing well off the back of the new designs. Some have made a strategic decision to focus on the low-wind market rather than on offshore. One of these is Nordex, which announced in 2012 that it was cancelling its 6MW offshore turbine in favour of developing its N117 2.4MW low-wind model.
It has now installed 188 of these machines since serial production began last summer. "This is our bread-and-butter machine at the moment," a Nordex spokesman says. "Eighty per cent of new orders in the first quarter of this year are based on this turbine."
Gamesa reports that 25% of the 2.6GW it installed in 2012 was in the low-wind market.
Enercon has also been targeting the low to medium speed wind market. The company has the advantage of dominating one of the main low-wind markets - Germany - with more than 50% of market share, according to consultancy Deutsche Windguard.
Southern Germany, specifically Bavaria, is regarded as a key area for development of low-wind sites since it needs to reduce its reliance on nuclear power as part of Germany's "Energiewende" and has few wind farms at present.
Enercon launched its E115 2.5MW turbine last September, following the launch of the E92 2.3MW model in May 2012. The firm recently signed a deal with Finnish power company Kotkan Energie Oy to provide the first E92s to a project in Finland, where wind speeds are typically low.
Those developing low-wind sites have specific obstacles to overcome, not least the logistics associated with transporting longer blades and taller towers. The ability to find solutions will depend on the market in which the turbines are being installed.
"In Europe you can find suppliers that have very big trucks to transport almost anything you want," Diaz says. "A 54-56 metre blade is not an issue in Europe. But a 56-metre blade is almost not possible in most of the sites in India." In response to this, Gamesa has designed a low-wind turbine specifically for the Indian market, the G97 with 47.5-metre blades.
Such innovation could bring wind power to entirely new markets that were previously not considered viable. Thailand is one such example. Chinese manufacturers are already eyeing the potential, with Goldwind signing a deal for three GW109/2500 low-wind turbines for the Theppana wind farm in the north-east of Thailand in September. "Thailand has a very good tariff and, compared to other countries in that region, it has easier finance and a more stable political structure," says Liming Qiao, China director at the Global Wind Energy Council.
Gamesa's Diaz believes that low-wind technologies will help countries in the Middle East and Africa that urgently need more energy, such as Saudi Arabia, Quatar, Namibia and Kenya. "Low wind technologies will allow countries to install cost-competitive megawatts," he says.
The potential for low wind to open up new sites could be substantial, says Williams of GL Garrad Hassan. "If you looked beforehand at 7m/s as your cut-off mark for what is an economic site, and this technology can bring that down to 6.5-6.7m/s, then you're going to be opening a good new tranche of sites," he says. "Low wind is not a game changer — it's working at the edges of the envelope, but it's pushing it a bit wider," he says.