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Science and Technology (2010)

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The structuring of low carbon technologies, and strategies for the development and dissemination of technologies for realizing a low carbon society

Structuring of component technologies (solar cells)


This year, our main focus was on polycrystalline solar cells. We conducted surveys on technology development trends and analyzed production costs. Development trend surveys involved studying available literature, conducting hearings with companies regarding solar panels and manufacturing equipment, and visiting plants and generation systems to gather information on current technology trends and the issues involved. Survey results were then used to develop technology scenarios. To analyze production costs, we designed plants comprising both main and peripheral equipment to allow us to conduct cost structure analysis focusing on improving conversion efficiency, production plant design and the development of component technologies.

Specifically, this involves adding up the costs of plant, energy, personnel and raw materials to conduct a quantitative evaluation of the production process from raw materials to end product. This data is then put to use in developing models to determine the possibility of cutting fixed and variable costs at each stage of production. Using these models, we developed technology scenarios that take into account the progress achieved to evaluate cost and environmental impact. We then published the results of our evaluations on polycrystalline solar cells. Details on the development of technology scenarios that consider various other types of solar cells will be given in (4). We intend to apply our detailed methods of analysis to various other types of solar cells and conduct quantitative analysis of a broader range of technology scenarios.

Structuring component technologies (storage batteries)


Lithium-ion batteries have become the most popular type of storage batteries. We therefore decided this year to examine the technologies involved in the manufacturing process of lithium-ion batteries and analyze production costs.
With regards to the production process, we analyzed the weight composition of the electrodes, electrolytes and containers used in the batteries and used the results to evaluate the production process of the various components that make up lithium-ion batteries. With regards to the technologies used in the main manufacturing equipment, we were able to determine technological trends and issues after studying patents and academic papers and by conducting hearings with equipment manufacturers.

In terms of analyzing production costs, we focused on a standard production plant with an annual output of 10GWh to conduct detailed analysis of the production equipment and facilities, the plant structure, and electricity consumption. This enabled us to determine the cost structure. We also began designing a lithium-ion battery plant with a potential annual output of 300GWh to determine which parts of the production process had room for improvement. We also studied the overall structure of the production system. Our next step will be to refine data results to conduct concrete technology evaluations, which we will then use to analyze the cost and environmental impact of various storage cell technologies.

Structuring the component technologies of solid oxide fuel cells and developing strategies for promoting widespread use.


We structured the component technologies of SOFC or solid oxide fuel cells, which have the potential of achieving the highest energy conversion efficiency. In addition to gathering information on SOFC component technologies from literature, we interviewed corporate developers and experts to further our understanding of electrodes, electrolytes, current collectors, and peripheral materials used in SOFCs.

We then categorized and consolidated our knowledge of the production methods of each component, the cell design and generation system. This allowed us to make predictions for the evolution of cell design and power generation efficiency based on current SOFC performance, and forecast future prospects for technology development.

Structuring the production process resulted in more reliable cost evaluations, including detailed information on production devices. This enabled us to develop scenarios for promoting the steady development and widespread use of SOFC as a low carbon technology. Next year, we will organize this information into a more generalized format to develop tools that can be applied to promote further low carbon technology developments.

Constructing scenarios for developing high efficiency solar cells


Comparison of crystalline silicon solar cells and CIGS thin film solar cells.
The basic structure of the crystalline silicon solar cells in use today was developed in the 1970s. Silicon solar cells have a band gap of around 1.12eV. Various technologies have been introduced to boost efficiency, including: 例えば、(1) Using an n+ layer (0.2-0.3μm) for better response to shorter wave lengths of light. (2) Creating a barrier (internal electric field) or back surface field (BSF) formed by a p/p+junction on the rear side of the cell to suppress the loss of the light emitting carrier due to recombination at the rear contact surface of the metal electrode. (3) Applying random pyramid structures or an anti-reflective coating(ARC) to trap light on the surface.

In 1999, UNSW succeeded in developing a 25% efficiency monocrystalline silicon solar cell with a theoretical efficiency of roughly 28%. This was the result of developing a PERL structure (Passivated Emitter and Rear Locally Diffused) to prevent surface and electrode contact recombination. It still holds the world record for high efficiency. Further efficiency may be achieved by improving the production process to improve silicon material quality, reduce crystal defects and achieve an optimal structure. However, there are limits to this. With CIGS thin film solar cells, however, by changing the GA/GA+In ratio, it becomes possible to adjust the band gap over a range of 1eV~1.68eV. The band gap to match the solar spectrum and enable the highest efficiency is ideally 1.4eV. In CIGS solar cells, however, a high efficiency of up to 20% has been reached with a band gap of 1.15eV (Ga/(Ga+In)~0.3). This is the highest efficiency achieved for thin film solar cells.

Because CIGS solar cells are less expensive to produce than silicon solar cells, boost the efficiency of this type holds greatest promise. We will conduct comprehensive comparisons and analysis of tandem and quantum dot solar cells to develop scenarios for improving efficiency.

Designing scenarios for developing low carbon technologies in an aging society, a significant factor in realizing a low carbon society in Japan


This year, as the first step towards achieving the objectives described above, we focused on solar cells and storage batteries to determine how delays or advances in R&D affect low carbonization and economic growth. For instance, the use of storage batteries in next-generation vehicles produced the following results.

Supposing vehicle sales in 2030 to consist of 40% hybrid vehicles, 20% plug-in hybrid vehicles and 10% electric vehicles. According to the current technology scenario, the cost of electricity would fall to 40yen/Wh in 2020, whereas if development were to be accelerated, the same target could be reached two years earlier in 2018. If, however, developments were to be delayed, resulting in a five year delay in reaching the 40yen/Wh level, accumulated economic expenditures(the total cost of development minus total amount of savings resulting from improved efficiency)from the introduction of electric, hybrid and other next-generation vehicles would be 1.1 trillion yen, compared to 0.64 trillion yen (current scenario) or 0.45 trillion yen (accelerated development scenario). When we look at clear targets for introducing new technologies and reducing CO2, the loss sustained by society as a result of delaying R & D would be 1.7 times greater than if development were to commence as scheduled. We also conducted similar technology scenario studies on solar cells.

We at LCS are creating precise quantitative technology scenarios for each of these low carbon technologies. We will apply these scenarios as well as create new scenarios for technologies other than solar cells and storage batteries, and provide detailed references for developing optional measures.

We have also created a list of low carbon technologies, with special emphasis on service systems (software), products and technologies necessary to create a smart community. We considered the issues at stake for each of the respective categories and clarified whether or not social experiments had already been conducted. If not, we determined whether such experiments were necessary. In compiling the list of technologies, we also took into account how effective they would be in stimulating economic growth and employment in an aging society and how useful they would be to the elderly. We plan to create a list of measures for an aging population, correlating key subjects and issues with low carbon technologies.

Research on concentrated and distributed energy management


Since electric power is difficult to store, it is necessary to maintain a constant balance between power generation and usage. Thermal power generation plays an important role in balancing demand and supply. A drop in output or an increase in output fluctuation due to climatic change resulting from the introduction of nuclear power generation and renewable energy will impact the electricity system's ability to balance supply and demand and restrict the introduction of such energy sources.

Up to now, most of the responsibility of adjusting supply and demand has fallen on the supply side, through such measures as daytime operation of pumped storage hydroelectric power stations, adjusting pumping up speed to regulate input, improving flexibility of thermal power plants, improving operation of hydroelectric plants, and controlling wind power generation output. New measures could be considered for the first time for also adjusting supply and demand at the demand side. These might include proactive demand management by using heat pump water heaters and by adjusting EV charging times, restricting PV generation and storage.

This year, we analyzed and evaluated conventional electricity systems and incorporated the above factors to develop demand-supply models for 2030 to 2050 in connection with energy models, referring to the Ministry of Environment's 2030 mid-term roadmap based on the Basic Energy Plan. Based on these models, we carried out trial calculations to determine the combination of storage batteries and other new measures necessary to maintain a stable balance in supply and demand.