Pushing the Ultra Envelope: Advanced Power Technologies Are Mainstream in China

China, which continues to build more new coal plants than any other nation, is also on the forefront of deploying the most advanced coal plant technologies. However, these advanced units could face unanticipated challenges.

As China continues to build out its power infrastructure, the country is seeking to find a balance in fueling its economy while doing so in an environmentally responsible way. China consumes more coal than all of the other countries on the planet combined. While hydro, wind, solar, and nuclear will continue to be added to China's energy portfolio, coal will remain the dominant fuel for power generation. In 2015, electricity produced from coal accounted for 73% of total output, and projections only have that tapering off a bit in the years to come.

China has ample coal reserves, along with its well-established domestic coal market, sophisticated import capabilities, and leading research centers on coal. As a result, the country has invested heavily in finding ways to make thermal power generation and transmission more efficient and environmentally friendly. There is no question that China is the world leader in implementing cleaner coal technologies, particularly ultrasupercritical (USC) power plants and ultra-high-voltage DC transmission to fulfill its needs (Table 1). As shown in "THE BIG PICTURE: Future Coal Fleet" in the January 2016 issue of POWER, China had roughly 50% of all advanced coal units, including USC, in 2014, and it is expected to have more than half of the advanced coal units globally in 2040-despite the temporary suspension of new coal-fired plants through 2018, which was widely reported this past summer.

Table 1. Leader with USC plants. China leads the world in the utilization of all coal-fired power technologies, from subcritical to advanced technologies like supercritical and ultrasupercritical (USC) boilers. Data represent installed (operating, shut down, and deactivated) capacity for major generating countries. Source: Platts UDI World Electric Power Plants Data Base, September 2016 release

USC plants, with significantly higher thermal efficiencies and lower emissions per MW produced than supercritical plants, combined with China's highly complex and somewhat uncertain renewable mix and transmission infrastructure, could present challenges for Chinese producers in the years ahead. The country's combination of assets could mean more load following or more frequent startups and shutdowns for thermal units. Equipment will be pushed to its limits. The power industry will need to focus on precise control and insight into the health of operating assets to maintain a robust electricity infrastructure.

Optimizing Clean Coal

Emerson is well experienced with USC plants-its Ovation controls are used on more than half of these Chinese facilities (Figure 1), which operate at approximately 320 bar and 600C (4,600 psi and 1,120F). These conditions approach the limits of metallurgy, and the standard configuration is generally a 1,000-MW unit. Due to their high pressures and temperatures, USC units are able to achieve significantly higher thermal efficiency than conventional drum units-typically, 44% to 46%, compared to the 32% to 34% for a state-of-the-art drum unit.

1. Hot market.Emerson has supported the commissioning and operation of many ultrasupercritical plants in China, like the Huaneng Qinbei power plant pictured here. Courtesy: Emerson

China has moved aggressively to push technology development for coal-fired plants, and continuing research is targeting a next generation of plants operating at even more extreme conditions (5,300 psi and 1,300F). Although these designs result in significantly higher thermal efficiencies and lower emissions per MW produced, they present some unique challenges. Operating at the limit of current metallurgy means there is very little margin for error for control, and equipment is pushed to its limits; precise control and insight into the health of operating assets are key to maintaining a reliable fleet. It is critical that utilities focus on controls to ensure that the technology envelope can continue to be pushed.

Overcoming a Gridlocked State

With a focus on air quality improvement, along with adopting USC technology, the trend is to relocate generating plants away from major population centers. Moving plants further away from load centers poses a different problem though: How do you get electricity from the plant to where it's needed? Enter ultra-high-voltage (UHV) transmission.

The State Grid Corp. of China, the world's largest electricity provider by revenue, put the world`s first 800 kV DC transmission system into commercial operation in 2010 and has since been building to larger scales. In 2015, a line from Zhudong to Chengdu was commissioned that carries 10,000 MW at 1,100 kV. This technology is scaling so successfully that China is evaluating its use to export power to Europe over a distance of 6,000 kilometers at a proposed 1,500 kV. China is also moving to export UHV technology via the State Grid Corp. and has projects currently under way in Brazil; others are proposed for India, Russia, and Kazakhstan.

The Environment for USC Development

These massive projects are the result of China's centralized development process, which is detailed in periodic plans, the latest of which was released last year as the 13th Five-Year Plan, covering 2016 to 2020. The 12th Five-Year Plan began addressing air pollution by placing an emphasis on air quality control systems and by paying better attention to efficiencies. Our estimate is that the majority of new coal plants will be of the 1,000-MW USC variety, as indicated in recent studies.

Much of the focus of the 13th Five-Year Plan continues the emphasis on improving air quality and reducing energy intensity, and this means ramping up investments in nuclear and renewable power. China's installed wind capacity has surged in recent years to over 145 GW, as compared to the 74 GW installed in the U.S., but it is still challenged with getting wind power to market due to transmission limitations. Curtailment rates (effectively, wasted power) in some regions may be as high as 30% due to insufficient local demand and the inability to move power to where it is needed.

Nuclear power is also a key initiative in China, with 35 reactors currently in operation and another 20 under construction, according to the World Nuclear Association. Currently planned projects will take China's nuclear generating capacity to 58 GW by 2021 and 150 GW by 2030. China is also planning to export nuclear plant technology via the State Nuclear Power Technology Corp.

It's clear that the power market in China is getting more and more complex. Along with having to integrate a vast amount of renewables into the power mix, the 13th plan will likely introduce a carbon trading market. For the coal fleet, this could mean more load following, or it could require more frequent startups and shutdowns. Because of these unknowns, it is especially critical that companies invest in a technology infrastructure that will allow them to meet these impending challenges. USC plants are difficult enough to operate at baseload, and they are even more challenging if you start mixing in the prospects of plant cycling.

While the rest of the world can learn from China about how to apply advanced power technologies successfully, Chinese power generators should take note of lessons learned in other areas of the world. As more renewables are added to China's generating mix, operators may not be running their USC plants as designed and could face forced outages and availability challenges. Because of these unknowns, it is critical that companies invest in a technology infrastructure that will allow them to meet these impending challenges. a-

-Bob Yeager(Robert.Yeager@emerson.com) is president, Power & Water Solutions for Emerson Automation Solutions.

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