2018 Volume 97 Issue 2 Pages 53-63
Although OTEC has good characteristics as a base load power supply, from view point of stability and resource amount, it has not been put to practical use because of its high power generation cost. In our previous paper1), the OTEC generation cost was shown to be reduced to 43.4 ￥/kWh, with 1.25 MW output capacity facility by optimizing the system with water intake and generation equipment. However, it is still much higher than the value, 5 - 10 ￥/kWh, of the coal fired power generation cost. It causes the difficulty of commercial application of OTEC system. The major factor of the high generation cost is low temperature of hightemperature side heat source. In this study, we conducted a conceptual design on the non-concentrating type solar heat collecting system as a low cost auxiliary equipment of the high-temperature side heat source in OTEC. We also optimized the total system by optimizing of the power generation equipment to fit to the temperature range, and estimated its power generation cost for larger scale system. By the calculated results with Kume island conditions, optimum high-temperature side temperature was 95 °C, and generation costs were 11.3 ￥/kWh for 10 MW, 7.0 ￥/kWh for 100 MW and 4.6 ￥/kWh for 1 GW output for each. These figures are comparable or even cheaper than the cost of other renewable systems, and it suggests the competitivity of OTEC to coal fired plant. Although this power generation system is a combination of the past technologies, we found that this kind of technology fusion among many fields in different industries remarkably contributes to the cost reduction with cost engineering and optimization. Additionally selecting the site blessed with solar radiation is expected to reduce the generation cost dramatically. Worldwide there are many sites suitable for this power generation method, suggesting that it will lead to full - commercialization of renewable energy as a base load power supply.
