Prospective life cycle sustainability assessment and decision support for solar electricity and industrial heat under uncertainty: a service-specific evaluation of PV, CSP, and CST

The transition to climate-neutral energy systems requires sustainability assessments that capture future technological, economic, and supply-chain conditions while preserving functional comparability. This study develops an integrated prospective life cycle sustainability assessment (pLCSA) and decision-support framework for utility-scale photovoltaic (PV), concentrating solar power (CSP), and concentrating solar thermal (CST) technologies in high-irradiance Southern Europe. Separate functional units are applied: 1 MWh of net electricity delivered for PV and CSP and 1 MWh of useful heat delivered at the industrial interface for CST. PV and CSP are therefore compared only within the electricity service, whereas CST is evaluated separately as an industrial-heat pathway and is not included in a cross-service ranking. Dynamic inventories represent changes in efficiency, material intensity, recycling, grid carbon intensity, and cost for 2025, 2035, and 2050. Seven environmental, economic, and socio-technical indicators are integrated for the PV-CSP comparison using entropy weighting and the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS), followed by 10,000 Monte Carlo iterations and stakeholder-priority and dispatchability sensitivity tests. The electricity-service TOPSIS scores are 0.613, 0.613, and 0.667 for PV and 0.387, 0.387, and 0.333 for CSP in 2025, 2035, and 2050, respectively. In the calibrated rank-acceptability sensitivity, which combines independent ± 20 % indicator variation with explicitly specified preference-weight uncertainty, PV is first in 96 %, 76 %, and 73 % of simulations. Employment-focused weighting and a dispatchability weight of approximately 20 % reverse the PV-CSP preference, demonstrating that the electricity ranking remains conditional on decision priorities. CST shows declining GWP, water use, CAPEX, and levelised heat cost and increasing recyclability and maturity across the same horizons, but these heat-service trends are interpreted without ranking CST against electricity technologies. The framework provides transparent data provenance, service-specific functional units, and quantified sensitivity while acknowledging limitations in storage equivalence, land use, resource depletion, and social-data completeness.