Energy Effectiveness and Economic Competitiveness of Two Emerging Solar Space Heating Technologies

ABSTRACT: This study provides a comprehensive long-term energy performance evaluation comparing traditional solar space heating systems (water and air collectors) with emerging alternatives, namely photovoltaic (PV)-driven heat pumps and photothermal solar heat extractors. The comparison is performed per unit collection area under idealized heat use and storage assumptions, rather than as a full building-level heating system analysis. Utilizing hourly meteorological and radiometric data from Rock Springs, US (2001–2022), the results reveal that while solar water heat extractors are more efficient than traditional heaters, their heating gain factor remains below 1.2, whereas emerging solar air heat extractors demonstrate low future potential. Over annual cycles, crystalline silicon PV-driven heat pumps outperform traditional solar water heating due to their superior efficiency under the low-to-moderate solar irradiance levels that dominate the heating season, despite traditional systems performing better at peak heat fluxes. Ultimately, this underscores that long-term technology dominance is strictly non-linear and governed by local radiative climates. Complementing the technical study, a preliminary economic screening is performed based strictly on component capital costs, without factoring in long-term operational dynamics such as maintenance, degradation, or discounting. Within this simplified financial framework, the analysis indicates that crystalline silicon or CdTe PV-driven heat pumps can viably replace solar water collectors (unless domestic hot water is a primary requirement) or expensive closed-circuit air collectors. Conversely, solar heat extractors remain viable only in niche applications with exceptionally high thermal energy costs exceeding 0.25 USD/kWh. By establishing these boundary thresholds, this work provides a streamlined decision-making framework that identifies the economic domains in which emerging PV-heat pump configurations achieve market viability relative to traditional thermal systems.