July 3, 2014 12:00 am JST

Japan at cutting edge of turning black coal more green

TORU HATANO, Nikkei staff writer

TOKYO -- Coal-fired power provides much of the energy needs for Asia. But these plants pollute the air and contribute to climate change by releasing particulate matter and carbon dioxide.

     Coal is a cheap and abundant resource, which makes it the easiest fuel to use for emerging and developing economies to satiate their rapidly growing need for electric power.
 
     They are not alone. Even Japan now acknowledges the importance of coal in its national energy policy.

     If countries plan to use more coal-fired power plants despite the environmental effects, they can at least adopt technologies that help make these plants friendlier to the environment.

     Japan is at the cutting edge of so-called green coal technology. One of the best examples of this effort can be found on an island in the Inland Sea.

Better than LNG

The island of Osakikamijima is part of Hiroshima Prefecture and home to a new, 100 billion yen ($986 million) project. The experimental coal-fired power plant being developed there by Electric Power Development, or J-Power, and Chugoku Electric Power would emit 30% less CO2 than standard plants and operate with an energy efficiency of better than 55%. This would make it more efficient than conventional coal-fired plants by over 15 percentage points.

     J-Power and Chugoku Electric are currently building a pilot plant based on the integrated coal gasification combined cycle (IGCC). By the fiscal year ending March 2022, they plan to integrate this with a fuel cell system and ultimately establish the technology for what is known as the integrated coal gasification fuel cell combined cycle (IGFC).

     In a regular coal-fired power plant, the coal is burned to boil water, which creates steam to drive turbines that generate electricity.

     In an IGCC plant, the coal is roasted and gasified to produce syngas, which is burned to drive a gas turbine. The waste heat is also captured and used to create steam to drive a steam turbine. Electricity is generated two separate times, and the result is an energy efficiency of 46-48%, which is better than a plant burning liquefied natural gas.

     An IGFC plant goes even further, as the hydrogen produced during the gasification of coal is used in fuel cells to generate electricity. This kind of plant promises to be even more energy efficient than IGCC alone because electricity is generated three separate times in one burn.
 
     "There is a good chance that the overall cost of these kinds of power generation will be cheaper than LNG power generation," said Masao Sotooka, director in charge of technology at Osaki CoolGen, a joint venture set up by J-Power and Chugoku Electric to run the island project.

     There are so many steps involved in IGCC power generation that the initial construction costs for an IGCC plant would be high. But to generate a given amount of electricity, the fuel costs would be less than half those of an LNG plant. Construction costs would inevitably come down through economies of scale.

Stronger materials

In Japan, the push to reduce greenhouse gas emissions stymied the construction of new coal-fired plants for many years. But that changed after the March 2011 earthquake and tsunami disaster, which shut down the country's nuclear power plants. The cost for fuel for thermal power plants has also risen.

     The Japanese government sanctified the new attitude toward coal in April when the cabinet approved a strategic energy plan that positions coal as a "base load" energy source. With coal energy back in favor, the focus is on developing technologies for more efficient energy production.

     That includes not only new processes like IGCC and IGFC, but also a renewed focus on better ways to generate electricity through the conventional burning of coal.

     One way to improve the energy efficiency of a steam turbine is to boost the temperature and pressure of the steam. With new materials capable of withstanding higher temperatures and pressures, subcritical power plants -- the mainstream until the 1970s and which had an energy efficiency of 36% -- gave way to supercritical power plants with an efficiency of 38%. Those were then surpassed by ultra-supercritical (USC) power plants, with an efficiency of 39-41%. Today, research is on advanced USC (A-USC) plants, which aim to compete head-on with IGCC technology, with an energy efficiency of 46-48%.

     Japanese manufacturers have aided this evolution by developing such technologies as turbines capable of withstanding temperatures of around 620 C for USC power plants.

     They are also participating in the development of A-USC power plants. Toshiba will soon enter the final stages of testing a nickel-based alloy that can withstand temperatures as high as 700 C. Other leading manufacturers involved in the push include IHI and Mitsubishi Hitachi Power Systems, a joint venture of Mitsubishi Heavy Industries and Hitachi.

     For the project taking place on Osakikamijima, Mitsubishi Hitachi Power Systems subsidiary Babcock-Hitachi is working on gasification equipment.

     "Lacking much in the way of natural resources, Japan conscientiously strives to make the most of its use of fuels," said Tetsuo Otsuka, director of the research and development department at J-Power.

Here to stay

Electricity production broadly falls under the categories of thermal power, nuclear power, hydropower and renewable energies.

     Before the earthquake disaster, thermal plants generated roughly 60% of Japan's electricity and nuclear plants accounted for around 30%.

     Today, Japan depends on thermal plants for about 90% of its electricity due to the closure of nuclear power plants.

     The main fuels used for thermal plants are coal and natural gas. At a fuel cost of roughly 4 yen per kilowatt-hour, coal plants generate electricity for half the cost of natural gas plants, but they also emit twice as much CO2.

     Renewable energies like wind and solar provide only around 2% of Japan's electricity. Since they are dependent on the weather, they are not suited as base load sources for the power grid. Solar power, for example, has an operating efficiency of only around 12%, compared with the roughly 80% of a coal-fired power plant.
 
     The International Energy Agency estimates that global electricity production will increase by around 70% between 2011 and 2035, and that 33% of all electricity in 2035 will be generated using coal. Though coal's share would fall below the 41% of 2011, the material would still be the most widely used fuel for power production.

     Coal will never be totally green or emit zero CO2 like wind and solar power. But given its continued importance for electricity generation, the world needs coal plants that are more energy efficient and friendlier to the environment.

     Japan recognizes this need, which is why it has positioned coal power technologies as a pillar of its infrastructure export policy. Emerging economies show great interest in Japanese technologies, as seen by the order won by a consortium including Mitsui & Co., IHI and Toshiba to build and operate a huge USC coal-fired plant in Malaysia.

     In the U.S., the administration of President Barack Obama has proposed an Environmental Protection Agency regulation to cut CO2 emissions from thermal power plants by 30% from 2005 levels by 2030.

     A viable IGFC technology could help achieve that goal. The project on Osakikamijima also includes plans to test methods for separating and recovering CO2. So technologies developed in Japan could help give coal a new image.