Guest post by Steve Latham
Could wind make a significant contribution to our energy requirements?
Global wind power has doubled over the last 3 years, which now accounts for 2% of the world’s electricity production, and as much as 20% in some countries. It is estimated that 13% of the worlds land area has wind speeds greater than 6.9 m/s at commercial wind turbine heights, this could theoretically produce 40 times the world's current electricity production. Although the total quantity of wind energy potentially available is considerable, there remain obstacles to the substantial expansion of this industry.
Critics claim that wind power cannot replace conventional power sources since these still need to be available for when the wind isn’t blowing, and these are expensive to keep in reserve and waiting on part load, reducing overall energy efficiency. For low contributions, wind power can be considered largely additional, since reserves are always needed to cater for unexpected unavailability of the largest single power source and having a large number of smaller generating units can sometimes be beneficial.
In addition to providing replacement power, wind plants reduce emissions by forcing the most polluting and inflexible power plants offline with more efficient and flexible types of generation. However, with increasing use of wind energy in the system the proportion of conventional plant wind replaces reduces, and consistent wind power generation requires high voltage connections to wind farms over a wide area.
Further expansion of the industry may also require energy storage technologies to balance fluctuations of supply and demand; these include hydroelectricity, compressed air storage and electro-chemical batteries. The latter option is particularly interesting in view of the potential use of battery-electric vehicles in the future since their batteries could be charged overnight when power demand is low and used to supply power during peak demand periods. Peak electricity demand could also be reduced through pricing structures and switching off non-essential appliances.
In addition to to replacing carbon intensive electricity production, wind power can drive heat pumps for space heating or charge vehicle batteries for transport, reducing natural gas and petroleum use. These are more efficient methods of producing heat and work than the traditional methods they replace, so direct comparisons of energy cannot usually be made . For example, one popular book grossly underestimated the potential contribution of wind power, partly because it compared the electricity generated from wind turbines with the primary chemical energy in fossil fuel directly.
This same book also concluded that heat pumps are a more efficient method of supplying energy than combined heat and power systems. However, I suggest that both systems could be used together to provide even greater benefits, and provide a means of matching wind supply with demand, thereby increasing the proportion of wind power used.
Figure 1 below illustrates a potential combined heat and power scheme where the energy input to a heat pump could be switched between electricity, partly powered from wind if necessary; and a directly coupled natural gas or biogas powered internal combustion engine. The engine can also drive the generator directly, providing backup power if necessary. I believe that by using energy in a strategic manner like this, wind power and other intermittent renewables can be more fully utilised within the grid system
The relative price of wind relative to fossil fuel based power is dependent upon a large number of variables making comparisons difficult and sometimes controversial. However, one of the most important is the price of fossil fuels, particularly oil and gas which could substantially increase in the future as cheap supplies become depleted.
Onshore wind appears relatively competitive with current (late 2010) oil prices at 88 $/barrel (see figure 2 below). To compete at lower oil prices or much higher wind penetration rates, the external costs of fossil fuels need to be included such as the effects of future global climate change, local pollution, and sometimes hidden subsidies and military expenditure to secure supplies. When the cost of fossil fuel electricity using carbon capture, and nuclear power are compared with wind on these terms, even offshore wind schemes appear competitive. However, there are large uncertainties in the cost of deep-sea wind turbines, modern nuclear and in particular carbon capture technology, which has still to be proven on a large scale.
Figure 2: Oil price at which various generating technologies become competitive
(Lower bar subsidised, upper bar unsubsidised)
There is sometimes substantial local opposition to the installation of large wind turbines, despite assurances that they are unlikely to adversely affect wildlife or human health. One method of mitigating these problems is by providing communities with a commercial stake in the wind farm, creating local jobs and collecting revenues by exporting electricity to the grid.
In practice, governments often prefer a variety of energy sources to improve security of supply and avoid reliance on any one region. Therefore, it can be politically and economically beneficial to include indigenous wind sources as part of the overall national energy strategy.
Wind power could economically provide a significant proportion of electric power for many countries and contribute usefully to their transportation and space heating requirements. One example is shown here for the UK. However, different countries will need to use different combinations of renewable and zero/low carbon technologies depending upon the local climate and resources. To fully exploit this, a strategically managed, widely spaced grid network needs to be developed, which should ideally be linked to offshore wind and other low carbon technologies.
Posted by perseus on Friday, 14 January, 2011
 |
The Skeptical Science website by Skeptical Science is licensed under a Creative Commons Attribution 3.0 Unported License. |