Sustainability of renewable energy systems with special referenceto ocean thermal energy conversion schemes.

Abstract

It was required to determine relative merits of commonly used renewable energy (RE) systems for which estimation of their individual sustainability percent achievable was chosen as the single criterion assessment tool. The methodology developed for estimating sustainability included identification of individual sustainability indices (SI) and examining the scope of sustainability percent input /kWh power generation for each of SI indices and summing them up estimating total sustainability accrued from respective RE systems. The RE systems studied included photo-voltaic (PV) cells, bio-fuels, on-shore & off-shore wind energy and OTEC schemes. Coal power plant being commercially viable was studied as the referral energy scheme. Nine SI indices identified for study included resource potential, greenhouse gas saving, influence on flora & fauna, effects on human health, land loss aspects, food and potable water security, economy evaluation, and improvement in quality of life from economic growth. Total sustainability achievable showed the highest in OTEC, followed by wind, bio-fuels and PV, respectively. SI index on quality of life showed RE schemes like OTEC & bio-fuels competing equally with coal power plant having poor sustainability with the least power generation cost; whence Hybrid OTEC showed the highest sustainability with high power production cost. Four fold approaches have been suggested for reducing power generation cost of OTEC. (i) Adopting economically viable scheme of not less than 40 MW. (ii) Heating up the working fluid with solar irradiation, terming SOTEC scheme. (iii) Saving cable laying cost, from hydrogen production utilizing the power generated. (iv) Hybridization of OTEC scheme.