Using an integrated approach for a comparative analysis of carbon footprints in onshore and offshore photovoltaic systems

Abstract

Taiwan faces challenges in expanding solar power due to limited land availability. Offshore floating photovoltaic (OFPV) systems have emerged as a promising alternative, supported by recent deployments on detention ponds, reservoirs, and coastal zones. Using the Carbon Footprint of Products–Product Category Rules (CFP–PCR) framework, this study conducts a comparative analysis of the carbon footprint inventory of a 100-MWp ground-based photovoltaic (LPV) system and a 181-MWp intertidal OFPV project in Changhua, Taiwan's first large-scale commercial OFPV installation, based on a lifecycle energy assessment approach. To ensure methodological consistency, unified assumptions are applied to both systems, including identical PV module type, project lifespan (25 years), degradation rate (0.5% per year), and functional unit (100 MWp). Manufacturing emissions are derived from CFP–PCR–aligned datasets reflecting Taiwan's importdependent PV supply chain, while avoided operational emissions are calculated using Taiwan's official grid-emission factor. Under these assumptions, the OFPV system produces approximately 2047.1 GWh over its lifetime, compared to 1827.8 GWh for the LPV system, representing an increase in about 12%. This corresponds to an estimated CO2 reduction of 1.013 Mt for OFPV, compared with 0.905 Mt for LPV, and an approximately 12% higher projected benefit under emissions-trading mechanisms. Environmental characteristics specific to intertidal deployment—including periodic water exposure, cooling effects, salinity, and tidal dynamics—are considered when interpreting performance differences. Given Taiwan's dense population and land-use competition, the results highlight the carbon-reduction potential of OFPV systems and support their further evaluation as a complementary strategy for solar energy expansion in land-constrained regions.