The Chinese market for nuclear hydrogen

Rare in nature, hydrogen can only be produced from various primary energy resources; in China, chiefly from coal. Hydrogen is already a significant chemical product in China, primarily in making nitrogen fertilizers, converting low-grade crude oils into transport fuels, and, increasingly, synthesis of coal-based alternative fuel (see Fig. 1). The amount of hydrogen produced (and consumed) in ammonia synthesis dominates the national total, but is approaching saturation point.

Production of captive H2 in China, by source

In contrast, the hydrogen consumed in methanol production witnessed rapid enlargement in the last 10 years, primarily due to deployment of coal-based methanol and dimethyl ether (DME) as alternative vehicle fuel in some coal-rich areas, such as Shanxi Province.

H2 from methanol triples in 10 years

The recent upsurge of coal-based alternative vehicle fuel will drive up the demand for captive hydrogen at an increasing pace in the near future. In 2009, six coal-to-liquid (CTL) projects, led by the 1Mt/yr coal direct liquefaction plant of Shenhua Group, the largest coal company in China, have been put into production. According to the development plans of several major coal companies in China, by 2020 coal-based oil production capacity will be around 30Mt/yr. If all the industries take the direct liquefaction route, the demand for captive hydrogen for this purpose will surpass 6Mt by then, 50% more than the total amount of methane produced in China in 2009.

In parallel with captive hydrogen, the production of by-product hydrogen has also been increasing, mainly from the coke and chlor-alkali industries (Fig. 2). This tendency is in accordance with the accelerated development of the heavy chemical and steel production industry. Hydrogen by-product is predominantly burned as a clean fuel in on-site power stations, helping conserve fossil fuels such as coal, oil and natural gas.

Production of by-product H2 in China, by source

By-product hydrogen will be a viable route for fuel cell vehicle demonstration and market penetration in advance of a large-scale hydrogen infrastructure being constructed. Half the annual output of by-product hydrogen is capable of supporting 20 million vehicles on the basis of per-unit annual mileage of 15,000km and hydrogen consumption rate of 1kg H2/100km, which is sufficient for near-term market deployment. But in the long run, when there are 150 million fuel cell-powered passenger vehicles running on the road, the annual fuel demand will be 22.5 million tons. Extra hydrogen production capacity will have to be established.

Demand: industry and transport

Interest in hydrogen arose in the 1990s due to rapid development of fuel cell technology. Since then, its mission has shifted from clean city transport to greenhouse gas (GHG) emission reduction and independence from oil imports. It is believed that electricity and hydrogen will play equal and complementary roles in a future energy system with no

GHG emissions. In fact, over the course of industrial development, major fuels have evolved in type (from coal to oil to natural gas), and in state (from solid to liquid to gas) according to a pattern of decreasing carbon and increasing hydrogen [1].

Nowadays GHG emission reduction and energy supply security create the two most stringent challenges confronting sustainable energy development in China. High carbon emissions come from high utilization of coal, which is the most abundant resource in China, but which has the highest carbon intensity. On the other hand, the fast-growing automobile market drives higher import dependence on petroleum. In 2009, oil consumption in China reached 393 Mt, with a worryingly high import dependence of 52%.

According to the Chinese government’s Outline of National Medium and Long-term Programme on Scientific and Technological Development (2006–2020), development of a diversified energy mix, including solar, wind, nuclear and biomass energy, is important in China. The development programme has also prioritised clean coal technology development, including coal gasification, liquefaction and multi-production, and hydrogen and fuel cell technology.

China’s efforts to optimize its energy structure have borne fruit; it has experienced continuous annual doubling of wind power capacity for the last four years, the largest capacity of nuclear power currently under construction, the largest hydro power capacity in operation, the largest solar power grid in operation, and so on. On the basis of this progress, the Chinese government plans to cut carbon dioxide emissions per unit of GDP by 40-45% of the 2005 level by 2020, and to increase the share of non-fossil fuels in primary energy consumption to around 15% by 2020.

With a major impact on both oil consumption and GHG emission, the automobile is at a turning point. In China as in the rest of the world, internal combustion engine hybrids using a variety of fuels will penetrate the marketplace in the near future, with improved efficiency and lower emissions. In the long run, the fuel-cell vehicle and plug-in hybrid electric vehicle is projected to take market share from conventional engine vehicles, hybrids and other alternate fuel vehicles, and finally dominate the future market.

New energy vehicles have been placed at the top of the agenda in Chinese development programmes. The potential of fuel cells, such as higher efficiencies than internal combustion engines and zero emissions, has received significant attention. During the past 10 years, with R&D support on hydrogen production, storage and fuel cells in the National High-Tech Program, China has witnessed significant progress

in these areas [2]. In the hydrogen transportation sector, since 2000 the Chinese government launched a series of national projects for development of electric vehicles, with a total fiscal investment of more than RMB 2 billion ($300 million).

The vision for China’s transition toward the hydrogen economy breaks down into three stages. By 2020 there will be a technology development phase focusing on research to meet customer requirements and establish a business case. By 2050 a market penetration phase will have begun, aiming for cultivation of electric power and transport market and infrastructure. Beyond 2050 there will be a fully developed FCV market and complete infrastructure. Fuel cell vehicle demonstration activities in China began with a Global Environmental Facility/United Nations Development Programme/China fuel cell bus project. Three fuel cell buses purchased from Daimler-Chrysler were demonstrated for 16 months beginning in June 2006, with total operation mileage of 92,116km. The buses later provided service for the Beijing Olympic games marathon competition. Also during the Olympics, 20 fuel cell-powered cars were demonstrated for 66 days, with total mileage of 76,000km and hydrogen consumption of 20,000Nm3. During the Shanghai World Expo 2010, 196 fuel cell vehicles, fueled with a purified by-product hydrogen from a suburban coke plant, will be demonstrated. In addition, an ambitious January 2009 government programme aims to promote large-scale commercialization of new energy vehicles in the public transport systems by making hybrid, electric and fuel cell buses and taxis available, initially in 13 cities. The government will provide a one-off subsidy for the purchase of these vehicles. By 2012, over 60,000 clean buses and taxis are expected to be running in China.

China’s annual energy consumption in 2020 has been estimated to reach 4500Mtce, (megatons coal equivalent) in which non-fossil fuel accounts for 675Mtce (15%), natural gas 304Mtce (6.76%), oil 750Mtce, and coal 2771Mtce (61.6%). China is estimated to be the world-leading importer of natural gas and crude oil by then. With predicted oil demands of around 530Mt/yr, and stable domestic production of 180Mt/yr, the country would have an import dependence of up to 66%, threatening safety of the economy and social stability. Coal can only be of little help to alleviate this problem. Although it is China’s largest fossil-fuel resource, it will reach its maximum exploitation capacity by then. Large-scale construction of conventional CTL plants will only shrink coal consumption in other areas, and restrain economic development as a result.

A novel idea is to shrink the role of coal in CTL to supply only the carbon in production of synthetic oil, and to supply the necessary input hydrogen and heat from nuclear energy, specifically those from high-temperature gas-cooled reactors (HTGR). The fluctuating and dispersed nature of renewables would make them unsuitable for energy supply for this purpose.

Supply: nuclear heating

HTGR study in China can be traced back to the 1970s. The nation’s first 10MW (thermal) high-temperature gas-cooled test reactor (HTR-10) reached its first criticality in 2000, and then successfully connected to the electric grid in 2003. HTGR technology is on a course toward commercialization. Supported by a national science and technology major project, the first high-temperature gas-cooled reactor pebble-bed module (HTR-PM) is being constructed in Shandong Province. The HTR-PM plant features 200MWe output from two reactor modules. The construction of the plant is scheduled to be completed by the end of 2013.

Two particular advantages, inherent safety and high outlet temperatures, make HTGRs more versatile than other nuclear reactor types. The design of the modular HTGR ensures that the maximum fuel temperature will never exceed the fuel’s design limit for any accident, so there are no emergency cooling measures. The reactor’s inherent safety enables it to be closely incorporated with other industrial facilities. Its high outlet temperature allows it to be a high-temperature heat source for many industrial processes, replacing coal, oil or natural gas. At present, its core outlet helium temperature can reach between 700-950°C. Even higher outlet temperatures are envisaged when the current research for better materials and improved fuel proves successful.

In the CTL process, which requires a large quantity of heat input and captive hydrogen, the HTGR performs three functions: it supplies nuclear heat to assist steam reforming and for high-temperature thermo-chemical production, and supplies heat and electricity for the high-temperature electrolysis of steam.

The efficiency of nuclear-based hydrogen production is considerably higher than conventional means. The whole process efficiency (from primary heat to hydrogen) of conventional electrolysis is between 25-35%, but the efficiencies of both the sulfur-iodine hydrogen production cycle and high-temperature electrolysis are higher than 50% [3]. With heat output of 250MW per module, the HTR-PM can produce 27,400ton/yr of hydrogen, enough to operate 183,000 fuel cell cars.

Chinese research on hydrogen production from the HTGR started in 2003. In the project, a laboratory-scale (10L/h) thermo-chemical water-splitting hydrogen production cycle system was established, the feasibility of the process was demonstrated, and a 1L/h high-temperature steam electrolysis system was set up and demonstrated. Supported by the HTR-PM project, bench-scale (60L/h) hydrogen production systems for both methods are planned to finish in 2014. An out-of-pile pilot demonstration plant with hydrogen output on the order of 1000m3/h is planned for construction in 2015-2020.

The proposed roadmap for nuclear-based hydrogen production could be: demonstration of HTGR as a high-temperature heat source incorporated in coal-based poly-generation plant before 2020; commercialization of nuclear-based hydrogen systems for coal-based alternate fuel synthesis in 2020-2030; and enlargement of nuclear-based hydrogen production to meet the demand of hydrogen for fuel-cell vehicle transport beyond 2030.

The imperatives of greenhouse gas reduction and security of supply tend to conflict with sustainable energy development in China. The tension will inevitably worsen if left alone. As it requires major oil consumption and produces large GHG emissions, the automobile transport sector is at a turning point. It is moving away from conventional internal combustion engines toward zero-emission plug-in hybrid electric vehicle and fuel cell-powered vehicles. Hydrogen demand is envisaged to be increasing in China. Large quantities of primary energy will be consumed for the production of this secondary energy carrier. The conventional CTL process will lead to a large amount of extra GHG emissions and threaten the coal supply. One solution in the near term is to offer the hydrogen and/or heat required for the oil synthesis process from nuclear energy, supplemented with coal for necessary carbon only. In the longer term, the HTGR could become the main hydrogen source for fuel cell-powered vehicles.

Kun Yuan, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, P. R. China