The study modeled a closed ammonia OTEC cycle whose evaporator received heat from a PVT field through an intermediate heat exchanger. The PVT coolant simultaneously cooled the photovoltaic cells and delivered recovered heat to the OTEC cycle. The analysis compared this hybrid with Case A, an uncooled photovoltaic array beside a standalone OTEC plant, and Case B, an actively cooled array that rejected its recovered heat to ambient.

Researchers optimized collector aperture area, specific heat-transfer-fluid flow, evaporator conductance and one of five commercial photovoltaic technologies. NSGA-III simultaneously optimized net plant power, system exergy efficiency and the crossover price, defined as the break-even electricity price for the incremental hybrid investment. Annual energy was calculated from long-term monthly solar climatology, with no thermal storage credited at night.

Machine-learning surrogates replaced repeated high-fidelity calculations during the search. Gaussian-process models were selected for the physical regression targets, while gradient-boosted trees classified whether a cycle solution existed. The annual hybrid energy increment relative to the uncooled reference had a cross-validated R² of 0.9980 and mean absolute error of 0.19 kWh per square metre per year.

Among 26 front designs re-evaluated with the full model, 25 were feasible. The surrogate overestimated the crossover price relative to the uncooled reference by a mean $0.002 per kilowatt-hour, and its Spearman rank correlation with verified values was 0.9985. Verification also identified one design that violated the evaporator approach limit by 0.012 K, which was removed from the reported results.

The verified Pareto front covered net hybrid outputs of 39–588 kW and exergy efficiencies of 11.6–21.7%. A selected knee design used 2,411 m² of collectors with TOPCon cells and delivered 459 kW at 19.7% exergy efficiency, but had a verified crossover price of $2.53 per kilowatt-hour. Multicrystalline silicon produced the lowest crossover price because its larger temperature coefficient produced a greater benefit from cooling; efficiency alone did not determine the ranking.

Relative to the actively cooled array, routing recovered heat to the OTEC evaporator had a coupling crossover price of $0.12–$0.13 per kilowatt-hour along the design-site front, below the reported diesel-cost range. This comparison excluded the cost of obtaining the cooled PVT field because that hardware was common to both configurations. The result supports using recovered heat once a PVT field has been justified for other reasons, rather than using OTEC coupling alone to justify the field.

At an electricity price of $0.40 per kilowatt-hour, the break-even PVT-specific cost was $43–$82 per square metre, compared with a documented range of about $200–$550 per square metre. A 20,000-draw Monte Carlo analysis produced a 5th–95th percentile crossover-price range of $1.76–$3.74 per kilowatt-hour, and every draw exceeded $0.80 per kilowatt-hour.

The analysis was limited to a steady-state model, one ammonia-based plant scale, no thermal storage and uncertain utility-scale PVT procurement costs. Collector areas above 2,000 m² and conditions outside the design-site climatology were extrapolations, and the diesel range was regional rather than a site-specific avoided-cost estimate.

Subject of Research: Techno-economic optimization of a hybrid photovoltaic-thermal and ocean thermal energy conversion plant

Article Title: Locating the economic threshold of a hybrid PVT/OTEC plant: a surrogate-assisted multi-objective optimization with high-fidelity verification

Article References: Ahmadi, M., Aghanajafi, C., & Vojdani, M. M. (2026). Locating the economic threshold of a hybrid PVT/OTEC plant: a surrogate-assisted multi-objective optimization with high-fidelity verification. Results in Engineering, 32, Article 113607. https://doi.org/10.1016/j.rineng.2026.113607

Image Credits: AI Generated

DOI: 10.1016/j.rineng.2026.113607

Keywords: PVT/OTEC hybrid, photovoltaic-thermal, ocean thermal energy, techno-economic optimization, crossover price, surrogate modeling, NSGA-III, high-fidelity verification, Locating, economic, threshold, hybrid