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.

Keywords

Space heating / Solar water collectors / Solar air collectors / PV cells / Heat pumps / Heat extractors

References

[1] Solar Heat Worldwide. Global Market Development and Trends 2024. Detailed Market Figures 2023; IEA Solar Heating & Cooling Programme; AEE-Institute for Sustainable Technologies: Gleisdorf, Austria, 2025.

[2] Li W-T, Tushar W, Yuen C, Ng BKK, Tai S, Chew KT. Energy efficiency improvement of solar water heating systems-An IoT based commissioning methodology. Energy Build. 2020, 224, 110231. DOI: 10.1016/j.enbuild.2020.110231

[3] Zohri M, Prabowo, Suwarno, Fudholi A, Suyono T, Priandana EP, et al. Performance review of solar-assisted heat pump systems using solar collectors, PV, and PVT technologies. Int. J. Heat Technol. 2023, 41, 657-665. DOI: 10.18280/ijht.410318

[4] Badescu V. Maximization of radiation heating efficiency. Appl. Therm. Eng. 2024, 257, 124480. DOI: 10.1016/j.applthermaleng.2024.124480

[5] Badescu V. Note on the maximum photothermal heating efficiency. J. Renew. Sustain. Energy 2025, 17, 012301. DOI: 10.1063/5.0243235

[6] Bava F, Furbo S, Brunger A. Correction of Collector Efficiency Depending on Fluid Type, Flow Rate and Collector Tilt. IEA Task 45-Large Systems, IEA-SHC TECH SHEET 45.A.1. 2014. Available online: http://task45.iea-shc.org/fact-sheets (accessed on 16 December 2025).

[7] Kalogirou SA. Solar Energy Engineering: Processes and Systems; Academic Press: Cambridge, MA, USA, 2009.

[8] Carvill J. Thermodynamics and heat transfer. In Mechanical Engineer’s Data Handbook; Elsevier: Amsterdam, The Netherlands, 1993; Chapter 3, p. 118.

[9] Staffell I, Brett D, Brandon N, Hawkes A. A review of domestic heat pumps. Energy Environ. Sci. 2012, 5, 9291-9306. DOI: 10.1039/c2ee22653g

[10] Kessel A, Benitez-Rodriguez JF, Nie S, Hameiri Z, Jasieniak JJ. Semi-Opaque Perovskite Solar Cells for Color-Neutral Photovoltaic Windows. ACS Energy Lett. 2025, 10, 5314-5321. DOI: 10.1021/acsenergylett.5c02792

[11] Hasan K, Yousuf SB, Tushar MS, Das B. Effects of different environmental and operational factors on the PV performance: A comprehensive review. Energy Sci. Eng. 2022, 10, 656-675. DOI: 10.1002/ese3.1043

[12] The POWER Project. NASA Prediction of Worldwide Resources. 2021. Available online: http://power.larc.nasa.gov/ (accessed on 15 May 2021).

[13] The POWER Project. Power Data Methodology. 2026. Available online: https://power.larc.nasa.gov/docs/methodology/ (accessed on 15 June 2026).

[14] Narayanan R, Parthkumar P, Pippia R. Solar energy utilisation in Australian homes: A case study. Case Stud. Therm. Eng. 2021, 28, 101603. DOI: 10.1016/j.csite.2021.101603

[15] Biyouki ZA, Zaman A, Marinova D, Minunno R, Shayegan MA. Solar Photovoltaics Value Chain and End-of-Life Management Practices: A Systematic Literature Review. Sustainability 2024, 16, 7038. DOI: 10.3390/su16167038

[16] Weiss W, Spörk-Dur M. Solar Heat Worldwide-Global Market Development and Trends in 2017. IEA SHC, Gleisdorf. 2018. Available online: https://www.iea-shc.org/data/sites/1/publications/Solar-Heat-Worldwide-2017.pdf (accessed 15 June 2026)

[17] US Energy Information Administration. Monthly Energy Reviews (June 2026). Available online: https://www.eia.gov/totalenergy/data/monthly/pdf/mer.pdf (accessed 15 June 2026)

[18] Natural Gas Local. Rock Springs, WY Natural Gas Rates. Available online: https://naturalgaslocal.com/states/wyoming/rock-springs/ (accessed on 16 December 2025).

[19] SOLARGE project. Solar Heat for Large Buildings. Available online: https://www.scribd.com/document/486874535/SOLARGE-Best-Practice-Catalogue-en#google_vignette (accessed on 16 December 2025).

[20] SolarTech. How Do Solar Water Heaters Work? Complete Guide 2025, SolarTech, 9 July 2025. Available online: https://solartechonline.com/blog/how-solar-water-heaters-work/ (accessed on 16 December 2015).

[21] ALTENER Program. Sun in Action II-A Solar Thermal Strategy for Europe, Volume 2, The Solar Thermal Sector Country by Country, ALTENER Program, Contract 4.1030/C/00-002/2000.

[22] Hydro Solar. Solar Water Heating Systems Cost in USA and Canada-A Complete Guide by Hydro Solar. 25 November 2025. Available online: https://hydrosolar.ca/blogs/news/solar-water-heating-systems-cost-usa (accessed on 16 December 2025).

[23] ARDCorp & B.C. Ministry of Agriculture. Assessing the Feasibility of Using Solar-Thermal Systems for Your Agricultural or Agri-Food Operation [Factsheet]. Government of British Columbia/Government of Canada, Growing Forward Initiative.

[24] AIR. Solar Air Heating and Ventilation. Australian Institute of Refrigeration, Air Conditioning and Heating. 2019. Available online: https://airah.org.au/Common/Uploaded%20files/Archive/IndustryLeadership/PUSCH/2019_PUSCH_1.pdf (accessed on 16 December 2025).

[25] Chopson P. Solar Panel Cost-Residential + Commercial. COVETOOL. Available online: https://help.covetool.com/en/articles/4529706-solar-panel-cost-residential-commercial (accessed on 16 December 2025).

[26] PVGIS. Residential Solar Panel Installation Costs: Complete Guide 2025. PVGIS, August 2025. Available online: https://pvgis.com/en/blog/residential-solar-panel-installation-costs (accessed on 16 December 2025).

[27] Riley DM, Fleming JE, Gallegos GR. A Photovoltaic System Payback Calculator; SANDIA Report SAND2016-5624; Sandia National Laboratories (SNL-NM): Albuquerque, NM, USA, 2016.

[28] ASHRAE. Organic Rankine Cycle Power Generation, Pratt & Whitney. Available online: https://aeenewengland.org/images/downloads/AEE_ASHRAE_JointMeeting_March2013/orc_power_generation_pratt_and_whitney.pdf (accessed on 15 June 2026).

[29] EUREKA. Comparison of Thermoelectric Generators and Organic Rankine Cycle Systems. Eureka. 10 September 2025. Available online: https://eureka.patsnap.com/report-comparison-of-thermoelectric-generators-and-organic-rankine-cycle-systems (accessed on 16 December 2025).

[30] Li K, Garrison G, Zhu Y, Moore M, Liu C, Hepper J, et al. Thermoelectric power generator: Field test at Bottle Rock geothermal power plant. J. Power Sources 2021, 485, 229-266, DOI: 10.1016/j.jpowsour.2020.229266

[31] Padinger R, Algenbauer S, Schmidl C. Best Practise Report on Decentralized Biomass Fired CHP Plants and Status of Biomass Fired Small- and Micro Scale CHP Technologies. IEA Bioenergy, Task 32, February 2019. Available online: https://task32.ieabioenergy.com/publications/best-practise-report-on-decentralized-biomass-fired-chp-plants-and-status-of-biomass-fired-small-and-micro-scale-chp-technologies/ (accessed on 15 June 2026).

[32] Gaur A, Tiwari GN. Exergoeconomic and enviroeconomic analysis of photovoltaic modules of different solar cells. J. Sol. Energy 2014, 2014, 719424. DOI: 10.1155/2014/719424

[33] Tiwari GN, Mishra RK, Solanki SC. Photovoltaic modules and their applications: A review on thermal modelling. Appl. Energy 2011, 88, 2287-2304. DOI: 10.1016/j.apenergy.2011.01.005