New research, published Monday in the journal Nature Energy by researchers from Tsinghua University in Beijing, Harvard University and other U.S. and Chinese universities, examines a handful of factors thought to be responsible for the discrepancy, using a mathematical approach to evaluate the relative importance of each.

Wind turbines can produce only as much energy as the wind provides — so the researchers were interested in whether differences in wind flow could account for some of China’s problems. But they found that these differences played a relatively small role. Although the United States tends to get superior winds nationwide, the researchers point out that China has approached this issue by promoting more development in the regions with the best wind resources, mostly to its north and northeast.

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Instead, the findings suggest that the primary challenges to wind power in China involve lower turbine quality, delayed connections to the grid and grid operators failing to transmit wind power to users in favor of other energy sources, such as coal — all of which play about equally important roles.

These issues are capable of putting a substantial dent in China’s wind electricity output, it turns out. The researchers noted that in 2012, China’s wind-generated electricity was 39.3 terawatt-hours less than that of the United States.

“This is a large number — larger than the total amount of wind power generated in the United Kingdom in 2015, which can power around 8 million UK homes,” wrote Joanna Lewis, an associate professor and expert on China’s energy landscape at Georgetown University, in a comment on the new study, also published Monday in Nature Energy.

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To evaluate the quality of turbines in China — which, the authors note, has not been done in previous studies — the researchers used the output from a specific type of wind installation (the GE 2.5 megawatt turbine) as a standard for comparison, concluding that overall turbine quality in the United States is higher than in China. They chalked up the quality issues to a need for “technology catch-up” in domestically produced turbines, which account for most of the installations in the country. The fix in this case is relatively simple: The authors recommend a short-term switch to more international suppliers, while focusing on domestic research and development efforts and technology transfer agreements with other nations in the long term.

For grid-connection issues, the researchers pointed out that the biggest problems occurred between 2006 and 2010. During this time, wind farms below a certain size could be approved by local governments, and this often happened without much coordination with plans to expand the grid. Essentially, more turbines were built than the country had the capacity to connect. This issue has already been addressed in part by the Chinese government.

“Realizing the grid connection bottleneck, the National Energy Administration took back the approval right for small wind projects in 2011,” the authors wrote. “An agreement between wind farm developers and grid companies is at present a prerequisite for approval of wind projects.” This decision has significantly cut down on idle capacity, or wind energy that isn’t being used.

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Perhaps the most complex issue is what is technically termed “curtailment” — this is when wind power is available, but grid operators choose not to dispatch it, effectively wasting it. According to the authors of the new study, a lot of this problem is bound up in China’s lingering dependence on coal-fired power plants.

As Lewis explains in her comment, “In general, wind energy poses challenges for grid operators due to its intermittency — the wind isn’t always blowing, and it’s not always easy to predict when it will. Unless it is stored, the electricity produced from wind farms must be used at the exact moment it is generated.”

This requires a bit of a balancing act between the deployment of wind power and power from other sources — namely coal, which still accounts for the majority of electricity produced in China. But the authors note that coal-fired power plants are often not flexible when it comes to adjusting their power output, meaning it’s difficult to conduct power balancing between coal and wind without wasting energy from one or the other. This is less of an issue in the United States, where more flexible power sources, such as gas-fired systems, play a bigger role in the market.

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A primary problem for wind in China is that coal is still a priority in the northern parts of the country, where wind power has the greatest potential. In these regions, coal-fired combined heat and electricity is “widely perceived as an effective means to improve the efficiency of energy systems, because it converts the energy of fuels to a combination of electricity and heat with a combined efficiency of up to 80 percent,” the authors write.

As Lewis points out, these competing policy objectives are “creating tensions in the power sector and opposition to renewable energy policy support.” And in the past, wind has lost out. About 15 percent of wind-generated power was curtailed in China last year.

The researchers recommend several approaches to address this problem. Certain technological solutions can be used to increase the flexibility of coal-fired power generation. And prioritizing the development and installation of electricity storage systems can help reduce the amount of wind-generated power that’s wasted. And enforcing regulations that prioritize the dispatch of renewables is an important step, as well.

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These proposals would be another nail in the coffin for coal, which — despite still being the dominant power source in China — is already starting to see the tables turn. Reports indicate that coal consumption hasn’t grown since 2013 and even declined in 2015. The Chinese government has announced a moratorium on any new coal mine approvals for at least the next three years, while renewable power installations are growing.