Is bigger always better? Designing economically feasible ocean thermal energy conversion systems using spatiotemporal resource data. (1st March 2022)

• Record Type: Journal Article
• Authors: Langer, Jannis; Infante Ferreira, Carlos; Quist, Jaco
• Is Part Of: Applied energy. Volume 309(2022)
• Publication Date: 2022-03-01
• Subjects: OTEC -- Modelling -- Economic Analysis -- LCOE -- Off-Design Performance; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2021.118414
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: We studied ocean thermal energy conversion's economics under off-design conditions. Our design model works for any system size, location, and temperature profile. In most analysed cases, conservatively designed systems yield the lowest cost. The electricity cost of a 136 MWgross plant are as low as 15.12 US¢(2021)/kWh. We give technical and regulatory recommendations to reduce investment costs further. Abstract: Ocean Thermal Energy Conversion (OTEC) produces electricity using the temperature difference between warm surface and cold deep-sea water. OTEC systems in literature only limitedly consider seasonal seawater temperature variations and thus might not be adequately sized for off-design conditions. This potentially leads to techno-economically sub-optimal design choices. This paper sheds light on which design approach yields the most economically feasible OTEC system considering off-design conditions with 19 years of seawater temperature data in 3-h time steps. We find that systems sized for worst-case thermal resources yield the highest and steadiest electricity production. If seawater temperature variations are moderate, these systems also perform best economically in terms of Levelized Cost of Electricity (LCOE) . We demonstrate our model for a 136 MWgross plant in Ende, Indonesia, with an LCOE of 15.12 US¢(2021)/kWh against a local electricity tariff of 15.77 US¢(2021)/kWh. The model is validated for different cost assumptions, system sizes, and temperature profiles to be useful globally. We give recommendations to curb costs and to move large-scale OTEC closer to today's state of the art, e.g. by using multiple smaller seawater pipes instead of few large pipes. The model is useful to prove OTEC's global economic feasibility and to promote the technology's commercialisation.