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Generating Electricity

R&D staff at the integrated research facility for combustion and flue gas treatment research, Babcock-Hitachi K.K. Kure Division, Akitsu Works, Hiroshima Prefecture, Japan

Coal Attracts Renewed Interest as an Energy Resource

The IEA (International Energy Agency) estimates that about 1.6 billion people still live without electricity. Total electricity consumption is projected to rise sharply with the economic growth and insatiable demand of developing nations.
So, what types of energy will support this increase in global energy consumption? The IEA, estimating future electric power generation by energy source, projects that coal-fired thermal power generation will continue to rise and reach 46 percent of total electric power generation in 2030.
The greatest reason for this growth is that coal is a resource with a stable supply. Coal reserves are plentiful and distributed across many regions. If resource extraction continues at today's rate, we may run out of oil in 41 years and natural gas in 61 years, but there are coal reserves for 155 more years, providing a stable supply into the future. With advances in denitrification and desulfurization technologies, which remove the nitrogen oxides (NOx) and sulfur oxides (SOx) that cause acid rain, coal has been attracting renewed attention as a resource for the stable supply of comparatively low-priced electricity.

Electric Power Generation Plants (1970–2030)
[image]Electric Power Generation Plants (1970-2030) Coal-fired power generation is projected to continue steadily increasing because of stable supply and advantageous generation costs. [Sources] 1997–2002: IEA, “Energy Balances of non-OECD Countries” (2004), 2005–2030: IEA, “World Energy Outlook” (2007)

Toward More Efficient Coal-Fired Electric Power Generation

It is, however, also essential to address the emissions issue because large quantities of CO2 are released when generating electric power from coal, which is a fossil fuel. Hitachi has been working to improve the efficiency of coal-fired thermal power, seeking to reduce CO2 emissions by generating more electricity from a smaller amount of coal.
Coal-fired thermal power plants burn pulverized coal inside boilers to generate steam, providing pressure to rotate steam turbine generators. In this process, the electricity generation efficiency increases as the steam temperature and pressure rises. The technology called supercritical pressure thermal power generation is based on this fact. Hitachi has succeeded in commercializing ultra-supercritical pressure thermal power generation with steam at a world-record temperature and pressure of 620°C and 25 MPa (250 times atmospheric pressure).
This technology has improved transmission end (net) efficiency (an indicator of the percentage of input energy converted into electric power) from 30 percent to 42 percent, reducing CO2 emissions by approximately 20 percent compared with conventional power plants. Hitachi is now working to further increase the steam temperature to 700°C to achieve a transmission end efficiency of 48 percent.

High Efficiency Coal-Fired Power Plant
[image]High Efficiency Coal-Fired Power Plant
The basic process of coal-fired thermal power generation is to burn pulverized coal inside a boiler and generate the steam to rotate a turbine. The combustion exhaust gas is eliminated after cleaning using desulfurization and desulfurization equipment. Hitachi has developed all of the technologies needed for more environmentally friendly coal-fired thermal power plants.

Analysis Technologies Support Reliability

It normally takes 36 months from the start of contruction to completing a thermal power plant. In other words, three years is needed to prove new technologies. To overcome this limitation, Hitachi has been developing analysis technologies for computer simulations of the combustion conditions inside boilers. Hitachi's simulations showing the combustion of pulverized coal are among the most precise in the world. Extremely reliable boilers that can withstand ultra-high pressures are a key component for ultra-supercritical pressure steam power generation. These analysis technologies have made Hitachi a pioneer in this field.
Since the early 1980s, Hitachi has been accumulating technologies for future coal-fired thermal power generation. Hitachi's 40 percent market share for denitrification and desulfurization equipment demonstrates this.
The Hitachi Group has constructed eight ultra-supercritical pressure thermal power generation plants in Japan and 21 overseas, including the Walter Scott, Jr. Energy Center Unit 4 in the U.S., making Hitachi a world leader.

[image]Walter Scott, Jr. Energy Center Unit 4
Walter Scott, Jr. Energy Center Unit 4

Together with J-POWER and the Chugoku Electric Power Co., Inc., we have begun working on the commercialization of integrated coal gasification combined-cycle power generation, which gasifies coal as a fuel to turn gas turbines but also turns steam turbines using exhaust heat.
We are also working to develop exhaust gas CO2 recovery technologies through this joint project.
Coal burning technologies brought about the Industrial Revolution and remain indispensable for our daily lives. Hitachi will continue striving to develop innovative technologies for the future, sustainable use of coal consistent with the needs and expectations of our stakeholders.

(Published in July 2008)