News in the WSJ on Sept 28th reported that China’s wind farms, which as I have noted before* , have some connectivity problems in joining the electrical grid. That information is nothing new, but the rest of the article’s discussion piqued my interest.
Apparently, the Chinese government is planning to ensure ample supplies of wind (even when it is not blowing) by balancing the load not with fast-starting natural gas plants, as some US wind farms utilize to manage the load, but with slow-starting and arguably heavy-polluting coal plants.
What is not common knowledge is that producing power is not as easy as connecting a wind farm into a preexisting grid. Wind power fluctuates and varies and sometimes needs to be shut down/curtailed if wind speeds exceed say 35 mph, or blow at less than around 5 mph. Too much or too little wind on the grid can cause power shortages. (A very basic explanation of load management and peaking is HERE). A news article on the problem of variable loads being matched with hydroelectric power is HERE.
According to NERC, which (under FERC’s supervision) can assess fines and create rules to ensure electricity reliability in the US, “Wind machines “ramp up” and trail off so fast that the grid is likely to need new generators fired by natural gas that can start up or shut down faster than the ones in service now.” (NYT).**
When I read the WSJ article, I could not initially believe what it was saying. For a country run by engineers and geologists, one would think that China would be well aware of the difficulties in cycling up and down different types of power. Natural gas is a good match for wind power because it is easy to cycle up quickly. Coal, however, takes longer to cycle up. For coal to be an efficient match to mitigate the variability of wind power, coal plants will need to be on constantly.
Considering that coal is a relatively cheap source of energy, wouldn’t it be cheaper for Chinese power plants only to invest in coal and run the plants at 100% capacity rather than constructing wind plants while running coal power plants at 50% and then scaling up their use when needed? By matching coal with wind, most potential environmental gains are negated since coal’s emissions constantly flutter into the atmosphere. Still, it could be said that some reduction in carbon output is better than none at all. But the matching of coal to wind certainly drives wind power’s costs up– for China’s economic detriment and only marginal environmental gains. (It could be that China is hoping the build-out of wind power helps them when the Copenhagen environmental carbon market targets are achieved; or that natural gas can be matched to the wind farms after certain pipelines are completed.)***
Why is China using coal instead of natural gas? China simply does not have very much natural gas. (EIA) Natural gas only accounted for 3% of China’s total energy mix in 2006, compared to nearly 70% provided by coal. (EIA). And of that, only 29% was used for electric power or residential and commercial uses as of 2005. (page 4, Yang Dengwei; 32% was used for industrial fuel) This should change, however, due to pipelines that China is constructing from bordering countries that have natural gas surpluses. And of course, Liquid Natural Gas technology also raises the amount of imports that China can receive. By 2011, China hopes to “raise the ratio of natural gas in its total primary energy consumption by 1 to 2 percentage points.” (China Daily). China’s natural gas consumption rose from 50 billion cubic meters in 2005 to 76 billion cubic meters in 2008, to an estimated 86 billion cubic meters in 2009. (China Daily).
I suspect that China may eventually decide to go down the route of battery storage of excess wind power in order to better manage the loads. But battery storage technology is still a bit expensive, “costing roughly $3 million per megawatt plus millions for start-up and testing.” (Scientific American).
When China’s excess natural gas pipeline capacity comes online, the country may also begin greater utilization of natural gas to manage wind’s load, but natural gas supplies will still be dwarfed by China’s coal– and natural gas prices may rise again like they did in Summer 2008. If a majority of China’s natural gas supplies are imported (as appears likely), in order to preserve energy security, Beijing may want to discourage generators from using natural gas to provide safety from wind’s variability. Hydroelectric power could also be paired to wind power. However, hydroelectric power is mostly concentrated in China’s south, whereas much of China’s wind resources are located in the North (Inner Mongolia, Xinjiang, etc.). Perhaps nuclear could balance the wind grid like coal currently does, but most new nuclear plants are to be built on the coast and near China’s south.
It will be interesting to examine how successfully China marries coal to wind generation and what sort of effect this will have on China’s future electricity pricing.
*In my older post I perhaps noted China’s wind connectivity problems a bit too harshly given that the US also has some grid connection problems regarding wind since even more so than in China, a great deal of US wind capacity is far from its citizens and will require long transmission lines to provide wind. This transmission problem helped lead to the demise of part of the Pickens Plan for a massive wind farm in Texas.
**At the very least, “[b]atteries or flywheels, both of which can store energy, may be needed to smooth out the production of wind farms, which stop producing power when the wind stops, or when the wind goes faster than the turbines can handle.” (NYT) [which leads to patents like THIS.]
*** Interesting fact. Due to the need for wind to be matched to more reliable sources of power, wind farms are not 0 carbon emission investments. One study reported that; “Increasing the capacity of wind energy on the Austin Energy grid causes increased usage of these less efficient peaking units. In other words, as more wind energy is generated, there is a drop in the overall efficiency of fossil fuel based energy on the grid, resulting in greater carbon emissions per unit of energy from the nonrenewable sources. . . For purchased wind energy from Austin Energy, with a 20 percent capacity of wind energy, each megawatthour of electricity would increase the emission from the fossil fuel sources by 60 lb of CO2 . While this CO2 emissions rate is lower than the current UT plant emissions of 694 lb/MWh, it is also not zero. Instead of the purchased wind energy being 100 percent carbonfree, the reserve offsets result in 91 percent carbonfree energy” (Is Wind Energy Hot Air?, UT)