A FEASIBILITY STUDY OF CONCEPTUAL DESIGN FOR
Takashi Sato, Akiyoshi Hamada, Kazuhiro Kitamura
INTERNATIONAL CLEAN ENERGY NETWORK USING
HYDROGEN CONVERSION TECHNOLOGY
ELECTRIC POWER DEVELOPMENT CO., LTD.
New Energy & Technology Development Department
15-1, GINZA 6-CHOME, CHUO-KU, TOKYO, 104 JAPAN
Clean energy is more and more required worldwide in proportion to actualization of global environmental issues including global warming . Therefore, it is an urgent task to realize promotion of worldwide introduction of clean energy which exists abundantly and is widely distributed in the world, such as hydropower and solar energy, while reducing the dependence on fossil fuel. However, since the renewable energy, differing from so called fossil fuel, is impossible to transport for long distance and store as it is, its utilization is subject to be limited.
As one possible resolution of this kind of issues, "International clean energy network using hydrogen conversion technology" which enables conversion of renewable energy from low cost hydropower into hydrogen energy and also into the transportable and storable form, is a meaningful concept. This system technology enables dealing of this hydrogen energy in international market as in the same manner as fossil fuel. It is considered to enable promotion of international and large scale introduction of such clean energy, along with the contribution to diversified and stabilized international energy supply.
In this study, based upon the above-mentioned point of view and assumption of two sites, one on supply side and another on demand side of hydrogen energy, three systems are presumed. One of the systems consists of liquid hydrogen as transportation and storage medium of hydrogen, and the others intermediately convert hydrogen into methanol or ammonia as an energy carrier. A overall conceptual design of each system spanning from hydrogen production to its utilization, is conducted in practical way in order to review the general technical aspects and economical aspects through cost analysis.
This study is administrated through the New Energy and Industrial Technology Development Organization (NEDO) as a part of the International Clean Energy Network Using Hydrogen Conversion (so-called WE-NET) Program with funding from the Agency of Industrial Science and Technology (AIST) in Ministry of International Trade and Industry (MITI) of Japan.
The long term purpose of WE-NET is hydrogen production using renewable energy such as hydropower and solar energy, conversion of the hydrogen into energy medium suitable for easy transportation and finally construction of large scale and concentrated utilization system through marine transportation to consuming site. In this study, high efficiency and large scale water electrolysis with solid polymer electrolytes which utilizes renewable energy generated from hydropower, is presumed as hydrogen production method. As to the transportation and storage method of hydrogen, each system which consists of liquid hydrogen, methanol and ammonia as an energy carrier respectively, from a standpoint of acquisition of improved hydrogen density per unit volume, is presumed. Also, as hydrogen utilization form, adoption of large scale and concentrated utilization using clean and high efficiency hydrogen combustion turbine by hydrogen-oxygen burning, is considered. The system constitution discussed in this study is shown as Figure 1.
2. STUDY OF OVERALL CONCEPTUAL DESIGN OF EACH SYSTEM
As overall conceptual design of each system under practical level spanning from hydrogen production to its utilization, generation output of 1,000 MW at the hydrogen combustion turbine (efficiency at power transmission end : 60%) and marine transportation distance of 5,000 km are assumed, and facility capacity, energy balance of each process and system energy efficiency (which is defined as the ratio of total electric energy at power transmission end in the hydrogen combustion turbine to total energy brought from outside the system in the hydrogen production and marine transportation process ), are obtained. Also, in the course of economical review of each system, the cost is analyzed making hydrogen cost and generation power cost at hydrogen combustion turbine to be index value.
Liquid hydrogen transportation system
As to liquid hydrogen transportation system, it is assumed that vaporized gas which is generated in each transfer, storage and marine transportation process of liquid hydrogen, is used for its re-liquefaction at loading site or feeding to the hydrogen combustion turbine power station at unloading site and for navigation fuel during marine transportation. The result is shown as Figure 2 and Table I.
Methanol transportation system
The methanol transportation system is the system that produces methanol by synthesis of hydrogen produced from the hydrogen production facility and carbon mono oxide from a coal gasification furnace, transports it by methanol tankers to consuming site and then reforms the methanol and separates hydrogen to be utilized. In this system, it is assumed that the methanol is used for navigation fuel of the tankers and for energy source required for reforming and separation of the methanol. The result is shown as Figure 3 and Table I.
Ammonia transportation system
The ammonia transportation system is the system that produces ammonia through synthesis process of hydrogen produced by the hydrogen production facility and nitrogen produced by a nitrogen production facility, and then, cracks and refines the ammonia and utilizes hydrogen after transportation of the produced ammonia to consumption site by ammonia tankers. In this system, use of heavy oil as tankers' fuel and off-gas in the cracking process and hydrogen in refinery process as energy source required for cracking and refinery of the ammonia, is assumed. The result is shown as Figure 4 and Table I.
As to economical review, facility installation cost corresponding to installation capacity of each process is to be obtained through unit installation cost of each fundamental process with consideration of scale factor. Also, hydrogen cost and power generation cost at the hydrogen combustion turbine are obtained from average yearly cost during service life (including depreciation cost of the facilities, business reward, fixed property tax, insurance fee, repair cost, personnel expenditure, cost for utilities and overhead charges), which is calculated in consideration of service life of each process facility. Infrastructure improvement cost such as land cost, berth facility construction cost and so on are not counted because of their uncertainty. The result of estimation of hydrogen cost and power generation cost at the hydrogen combustion turbine is shown as Table II.
The results of this study indicate the following:
- In the case of hydrogen energy transportation with premise of large scale concentrated utilization of hydrogen, the system which uses liquid hydrogen as an energy carrier is of the most efficient energy system.
- In order to decrease power generation cost by the hydrogen combustion turbine, it is required to improve system energy efficiency and to decrease facility installation cost. Decrement of power generation cost through future technology development such as optimization of the system and realization of lower cost process, can be well expected, since the liquid hydrogen transportation system is the technology of which practical use will be expected at the timing of year after 2020 in the WE-NET, and the cost estimation in this study shows just assumption value for the time being. On the other hand, it seems rather hard to decrease substantially the cost of the methanol and ammonia transportation systems , since they are cost-calculated based on the established technologies at present, even though there exists some cost reduction factor such as development of new synthesis process and also hydrogen separation process.
- In the case that expected date of practical use of large scale concentrated hydrogen energy utilization technology will be later than 2020, it seems quite important to develop steadily the liquid hydrogen transportation system that stays on still technically premature stage at present.
4. FUTURE WORK
The target of the WE-NET project is to reflect fruition of the technology development to the image of future hydrogen society, in other words, to contribute effectively to settlement of the energy and environmental issues by timely realization of practical use of the fruition. In the first stage of research and development (1993 to 1998) of this study, a long term technology development considering the hydrogen produced overseas from renewable energy has been promoted. However, in the second stage research and development (1999 to 2003), the technology development emphasizing the following items of diverted utilization technologies and of which industrial utilization can be expected in relatively short term, is now being planned in order to accelerate introduction of the hydrogen energy system that is featured by excellent characteristic in environmental aspects, into the future society.
The system technology which was a significant theme in the first stage research and development and of which a long term target was large scale concentrated utilization of power generation by hydrogen combustion turbine, is one of promising energy alternatives in the future when bulk transportation of hydrogen will become possible, therefore, elemental technology development as a long term research and development item is now planned to be continued.
- Technology development of power generation related to hydrogen diesel engine and co-generation system utilizing it.
- Technology development related to hydrogen automobile system and public transportation system in connection with hydrogen supplying station.
- Technology development of a pure hydrogen-feed solid polymer electrolytes fuel cell which has excellent characteristic as for its application to a hydrogen automobile, and of which application to energy conversion field can be well expected.
We would like to express our sincere gratitude to those who belong to sub-task teams and have offered very useful data, and those who belong to NEDO and other WE-NET related projects, and have given very effective comment to us on putting together various kind of data into the present article.
- International Clean Energy Network Using Hydrogen Conversion (WE-NET) : NEDO Annual Summary Report on Results, 1994-1996.