| 摘要 |
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1. Background and Research Objectives
Recently, the Korean government has selected the hydrogen and fuel cell technology as a new growth engine and is fostering it as a core industry for ��Low Carbon Green Growth.�� Hydrogen is an energy carrier, and can be produced from a wide variety of energy sources such as fossil fuels, nuclear power, biomass, geothermal, wind, and solar energy, eventually replacing the current carbon economy which rests on overuse of fossil fuels as well as nuclear power. Accordingly, major industrial countries keep investing into R&D activities in anticipation of a hydrogen economy.
Major concerns in transition to a hydrogen economy include the economic feasibility of fuel cells in the practical application, the construction of a cost effective hydrogen infrastructure along with an optimal mix of feed stocks for hydrogen production. Economic feasibility can be enhanced through R&Ds and mass production which will lead to improved efficiency and reduced system costs. It also is recommended that the government start and build a minimum hydrogen supply infrastructure to initiate the head start in transition to the eventual hydrogen economy. A systemic approach is needed since hydrogen flows through multiple steps of production, storage, transportation, and conversion.
In this context, this study focuses on finding an optimal scale of fuel cells for each sector, namely, residential/commercial sector and power sector, taking those models selected to be analyzed for economic feasibility; deriving an optimal mix of feedstock for hydrogen production, and finding an efficient hydrogen supply system based on the long-term strategies and roadmap of the watershed report(2005) "A National Vision of Hydrogen Economy and Action Plan".
2. Methodology
This study adopts several approaches and methodologies in solving problems to be faced with in each chapter.
First of all, economics of fuel cell system was examined by applying benefit/cost(B/C) analysis, using fuel cell system models selected based on power load as well as heat load typical for residential use, resulting in NPV and B/C ratio. Then, a sensitivity analysis was performed with significant variables such as system cost, fuel cost. In the case of fuel cells for power generation, similar approach was adopted except for using a scenario approach in terms of policy variables such as feed-in tariff and RPS. In fact, it is too early to explore economic feasibility of fuel cells which still remain in the stage of technological validation and demonstration. However, it is worthwhile to guess when it will be economically feasible and what policy tools are needed to make it happen in the foreseeable future. Second, regardinog the optimal mix of feedstock for hydrogen production, a newly developed methodology, Benefit, Opportunity, Cost, Risk (BOCR) AHP was applied. The existing AHP method employed in the previous 2006 study revealed its limitation as an approach in deriving the optimal mix of feedstock for hydrogen production. BOCR-AHP method uses the quantitative variables such as opportunities, risks, costs and benefits. Candidate feedstock include natural gas, surplus electricity, byproduct gas, coal, nuclear power, bioenergy, solar energy, and wind power.
Third, an optimal system of hydrogen supply infrastructure was built, using a two-tiered approach. First, hydrogen production system is grouped into central off-site and distributed on-site. Second, an integer programming to optimize the supply system of hydrogen.
Hydrogen production, if seen in terms of production site, can be categorized into a central off-site plant of large scale hydrogen production and a distributed on-site station. In addition, hydrogen transportation implies that hydrogen produced in a central off-site plant is delivered to an end-user, that is, a filling station. For a distributed on-site production of hydrogen, the object to be delivered is feedstock such as natural gas, naphtha, LPG, etc., but not hydrogen.
The optimization model for the hydrogen supply system is formulated as an integer programming. The objective is to determine the schedule of the hydrogen supply locations and amounts that minimizes the total hydrogen production and transportation cost while satisfying supply and demand limits. The optimal hydrogen supply plan is obtained by applying the well-known LINGO optimization software.
3. Major Findings and Policy Implications
Major findings of this study are as follows:
First, economic feasibility is too low which is not unusual at this junction. Operation in terms of power load following, heat load following, even complex load following shows B/C ratio and NPV as follows:
�� power load following: 0.41, -1,371,000 Won
�� Heat load following: 0.38, -1,445,000 Won
�� Complex load following: 0.41, -1,36o,00 Won
However, when sensitivity analysis is conducted in anticipation of cost reduction and indirect benefits incurred from installation of fuel cells shows a very positive B/C ratio and NPV. If system cost is reduced half as high as the current one, it reaches break even point, with B/C ratio higher than 1.
Third, economics of fuel cell for power generation use shows more encouraging, if not all positive. A multiple series of scenarios are adopted to explore economic feasibility of fuel cells for power generation: FIT scenario, RPS scenario, and FIT+(heat trade) scenario. Analytical result shows that positive NPV and B/C ratio for scenarios of FIT and FIT+, but negative ones for scenario of RPS.
Fourth, using BOCR-AHP, an optimal mix of feed stocks for hydrogen production was derived. Analytical result shows that coal was ranked in the first place (0.378 points, sharing 19.5%), followed by nuclear power (0.286 points, sharing 14.8%), natural gas (0.282 points, sharing 14.6%) in the upper level. This result is partially, not fully reflected in building an optimal system of hydrogen supply infrastructure in the following chapter.
Fifth, the maximum hydrogen production from new and renewable energy in 2040 is estimated to be 1,778 thousand tons if we adopt a cost effective hydrogen supply system. The previous study estimated the hydrogen production from it in 2040 was 4,502 thousand tons, but this hydrogen supply plan is difficult to achieve because of the lack of the potential domestic resources of new and renewable energy.
Sixth, the average hydrogen supply cost by central off-site hydrogen production in 2040 is estimated to be $2.69/kgH2, if nuclear power is included for hydrogen production. If we do not utilize nuclear power as a source of hydrogen production, the average hydrogen supply cost in 2040 is increased to $2.94/kgH2. In addition, the average hydrogen transportation distance with and without an option of nuclear power is estimated to be 55.1km and 49.6km, respectively.
Last, an optimal mix of feedstock for hydrogen production should be derived in consideration of the climate change, the energy security, the energy cost, the economic pervasive cost, and the social acceptance. Nuclear power can be an influential energy source for the off-site hydrogen production. In spite of the lack of the social acceptance of nuclear power, it is desirable that nuclear power will be included as an energy source for hydrogen production because of its superiority in terms of cost and environment.
4. Suggestions for Further Studies
This study focuses on finding the optimal hydrogen supply system as a part of pathways towards a cost-effective hydrogen economy. However, potentiality of hydrogen production sites is not taken into a full consideration. It was assumed that hydrogen production by nuclear and coal were restricted to existing sites. Neither were domestic hydrogen production prices by energy source fully analyzed. Accordingly, further research is called for to address the analysis of energy sources and plant sites for hydrogen production.
In addition, it is needed to analyze the hydrogen infrastructure. The details of hydrogen fueling stations and delivery systems need to be determined for the analysis of the hydrogen infrastructure. Also, it grasps influences and potential changes on existing energy sources and infrastructures when the hydrogen infrastructure is introduced.
It was already stated that the systemic approach is needed for an efficient transition to hydrogen economy. The objectives of hydrogen economy can be achieved efficiently and effectively by a systemic approach. The DOE(department of energy) is developing a couple of system analysis tools for analyzing and modelling of the hydrogen economy system. In this regard, Korea needs to develop an analytical model which is suitable for analyzing domestic hydrogen economy.
Last, it is desirable that economic impact analysis of materialization of hydrogen economy will be conducted. The objectives of the impact analysis are to develop a consistent and integrated framework which evaluate the impacts of hydrogen economy on Korean economy, evaluate the costs and timeliness of various scenarios of a developing hydrogen supply infrastructure, identify most economic routes and financial risks of hydrogen production, and evaluate impacts on Korean energy markets in terms of prices and consumption for coal, natural gas, renewables and electricity.
Language: Korean |
