An Integrated Marine Photovoltaics–Seawater Electrolysis System for Hydrogen Production in the Coastal Cities of Andhra Pradesh State in India

Hydrogen is becoming more widely recognized as a vital product and is being used in mobility, numerous industrial operations, and household heating applications. Given the wide range of applications, the demand has grown more than threefold since 1975 and still continues to rise. With the threefold increase in demands, supplying hydrogen to users has now a major business worldwide. As of 2021, the hydrogen demand stood at 90 Mt, and most of it is supplied from fossil fuels resulting in close to 900 Mt of CO2 emissions. Hence, in the quest to achieve carbon-neutrality in hydrogen production, concepts like blue and green hydrogen have become buzz terms where the production process and the type of energy used will determine whether the hydrogen produced is low-carbon or not. For instance, if the produced hydrogen is from natural gas, the process must incorporate carbon capture, utilization and storage concepts to claim the produced hydrogen under low-carbon, called blue hydrogen. Whereas if the produced hydrogen is from water based on electrolysis, then the process must be powered by a low-carbon source such as solar, wind, and other renewables to be considered under low-carbon, called green hydrogen.

In this study, we focus in particular on the green hydrogen production process where it contains seawater reverse osmosis (SWRO) coupled to proton exchange membrane (PEM) electrolysis and powered by marine photovoltaics (MPV). We applied systems thinking to SWRO, PEM, and MPV; we designed this integrated marine photovoltaics–seawater electrolysis approach for hydrogen production. As an illustrative case study, we first modelled a representative model of a hydrogen production unit with a capacity of 4000 Nm3/h. Based on the proposed production capacity, the SWRO system and MPV system are further modelled. Second, the designed 4000 Nm3/h hydrogen plant is tested for its production performance in India's 9 coastal cities (Srikakulam, Vijayanagaram, Visakhapatnam, East Godavari, West Godavari, Krishna, Guntur, Prakasam, and SPSR Nellore) of Andhra Pradesh State. Third, by considering the local weather conditions, the practical energy performance of off-shore and on-shore MPV is investigated to understand the overall impacts on the net production rates of hydrogen.

The results of this study include the designed system's specifications, MPV energy yields (on-shore: 4.06-4.49 kWh/kWp; off-shore: 4.90-5.72 kWh/kW), capacity factors (14-23%), performance ratios (78-86%); SWRO’s freshwater production yields; and net hydrogen production rates from PEM electrolyser. It is observed that the same system performed differently in 9 coastal cities, and the observed yields are varied when different uncertainties were considered. The key reason for this variation is the energy outputs from the off-shore and on-shore MPV. Overall, we believe that the proposed approach will help establish hydrogen production and distribution-based business in these 9 coastal cities of India. Also, the given long coastal line of the Andhra Pradesh state favours commercial production and could also help drive e-mobility.