Wind power has been blowing hot for over a decade as one of the leading renewable-energy sources.
According to BP’s Statistical Review of World Energy 2012, the yearly growth rate of global cumulative installed wind power capacity has been above 20% since 1996 and averaged over 25% a year in the last decade. This means capacity has been doubling roughly every three years. The 40 GW of capacity added in 2011 was greater than that of any other renewable-energy technology, according to the Renewables 2012 Global Status Report published by REN21.
By the end of last year, global installed wind capacity was nearly 240 GW. China boasted a 26% share of this, having added a whopping 17.6 GW – almost 40% – to its capacity last year alone. In second place was the US, with a 20% share. After leading the rankings until 2007, Germany’s share shrank to 12% after recording relatively sluggish growth of 7% in 2011.
Although the top ten countries notched up 87% of global capacity, nearly 50 countries added wind capacity last year, showing that its appeal is broadening. More than half of this new capacity was in developing countries.
When wind power output is measured as a proportion of total electricity generated, Denmark leads the pack, with 28% in 2011, followed by Spain, with 15%. Globally, however, wind accounted for 437 TWh of generated electricity in 2011 – just 2% of electricity generated from all energy sources and less than 0.5% of total world primary energy supply.
Wind power is a fairly mature technology, having been around since the 1970s. Turbine efficiencies have increased considerably, as designs have improved and turbines have become bigger. The average size of turbines sold in 2011 was 1.7 MW, whereas the biggest new designs generate up to 7.5 MW.
At present, more than 98% of wind power capacity is onshore. But offshore installations are growing – most notably in Europe. Offshore sites often offer stronger, less variable winds and do not compete with scarce land resources or attract as much local opposition. However, they are more expensive to erect. Small-scale wind turbines – often owned by individuals or communities – are also growing rapidly, especially in rural areas.
Global investment in wind power in 2011 totalled $84-billion, down 12% year-on-year but still nearly one-third of investment in renewables. In the renewables space, wind power may be in the process of being eclipsed by solar photovoltaic power.
In some countries, such as the US and Germany, investment has been partly driven by government incentives. But wind power has become commercially competitive with fossil-fuel-based electricity in some areas, thanks to falling costs driven by increasing industry competition, scale and efficiencies. The energy return on investment ratio for wind power is estimated to average 18:1 globally, which compares favourably to a global average of around 15:1 for oil and gas.
The biggest downside to wind power is its intermittency. Average load factors are about 25% 30%, since wind blows with variable strength, and sometimes not at all.
This means that wind power has to be twinned with either large-scale electricity storage – such as pumped hydro – or backup generation like open- or closed-cycle gas turbines. In the longer-term future, if plug-in battery electric or hybrid vehicles were rolled out on a mass scale, they could potentially provide a storage mechanism for wind power. But this vision relies on significant improvements and cost reductions in battery technology.
Another way to handle wind power variability is to feed it into larger, more sophisticated high-voltage grids. This is what several European countries have been doing.
Another drawback of wind turbines is that they use copious amounts of less environmentally sustainable materials, such as steel and concrete. And the electric motors currently rely on rare-earth metals, whose supply is increasingly uncertain as monopolist China has been taking steps to curb production and exports. The expected life span of a modern wind turbine is 20 to 25 years – a lot less than conventional power stations.
Moreover, the manufacture, installation and maintenance of wind turbines currently depends on a fossil-fuel-powered industrial system. Try to imagine using wind power – or other renewables – to mine iron-ore, produce steel, transport massive turbine components to inaccessible places and erect them on sturdy concrete foundations.
So, although wind has been a renewable- energy powerhouse in recent years, closer inspection reveals it to be very much a product of the fossil-fuel-based industrial age. It remains to be seen whether today’s wind power technology is truly sustainable or is merely a bridge to other as-yet-undeveloped durable technologies.