17 September 2009

China's electricity demands blowing in wind

Wind alone has the potential to meet China’s electricity demands projected for 2030.

The switch from coal and other fossil fuels to greener wind-based energy could also mitigate CO₂ emissions, thereby reducing pollution, according to a report from a team of environmental scientists from Harvard and Tsinghua University.

“The world is struggling with the question of ‘how do you make the switch from carbon-rich fuels to something carbon-free?’ ” said Michael B. McElroy, Gilbert Butler Professor of Environmental Studies at Harvard’s School of Engineering and Applied Sciences (SEAS) and lead author of the report.

China has become second only to the U.S. in its national power generating capacity, 792.5 gigawatts per year with an expected future 10% annual increase, and is now the world’s largest CO₂ emitter. “The real question for the globe is: What alternatives does China have?” McElroy asked.

While wind-generated energy accounts for 0.4% of China’s current electricity supply, the country is rapidly becoming the world’s fastest growing market for wind power, trailing only the U.S., Germany, and Spain in terms of installed capacities of existing wind farms.

Development of renewable energy in China, especially wind, received a boost with passage of the Renewable Energy Law in 2005; the law provides favorable tax status for alternative energy investments. The Chinese government also created a concession bidding process to guarantee a reasonable return for large wind projects.

“To determine the viability of wind-based energy for China, we established a location-based economic model, incorporating the bidding process, and calculated the energy cost based on geography,” said Xi Lu, a graduate student in McElroy’s group at SEAS and a co-author of the report. “Using the same model, we also evaluated the total potentials for wind energy that could be realized at a certain cost level.”

To help with their model, researchers used meteorological data from the Goddard Earth Observing Data Assimilation System at NASA. In addition, they assumed the wind energy would come from a set of land-based 1.5-megawatt turbines operating over non-forested, ice-free, rural areas with a slope no more than 20%.

“By bringing the capabilities of atmospheric science to the study of energy, we were able to view the wind resource in a total context,” said Chris P. Nielsen, executive director of the Harvard China Project, based at SEAS, and a co-author of the report.

The analysis showed a network of wind turbines operating at as little as 20% of their rated capacity could provide potentially as much as 24.7 petawatt-hours of electricity annually, or more than seven times China’s current consumption. The researchers also determined wind energy alone, at 7.6 U.S. cents per kilowatt-hour, could accommodate the country’s entire demand for electricity projected for 2030.

“Wind farms would only need to take up land areas of 0.5 million square kilometers, or regions about three quarters of the size of Texas. The physical footprints of wind turbines would be even smaller, allowing the areas to remain agricultural,” Lu said.

By contrast, to meet the increased demand for electricity during the next 20 years using fossil fuel-based energy sources, China would have to construct coal-fired power plants that could produce the equivalent of 800 gigawatts of electricity, resulting in a potential increase of 3.5 gigatons of CO₂ per year. The use of cleaner wind energy could meet future demands and, even if only used to supplement existing energy sources, significantly reduce carbon emissions.

Moving to a low-carbon energy future would require China to make an investment of around $900 billion (at current prices) over the same 20-year period. The scientists consider this a large but not unreasonable investment given the present size of the Chinese economy. Moreover, whatever the energy source, the country will need to build and support an expanded energy grid to accommodate the anticipated growth in power demand.

“We are trying to cut into the current defined demand for new electricity generation in China, which is roughly a gigawatt a week—or an enormous 50 gigawatts per year,” said McElroy. “China is bringing on several coal fire power plants a week. By publicizing the opportunity for a different way to go, we will hope to have a positive influence.”

For related information, go to www.isa.org/manufacturing_automation.