TY  - EJOU
AU  - Karimi, Mehran 
AU  - Heidarigoujani, Hesamodin 
AU  - Jahangiri, Mehdi 
AU  - Anaraki, Milad Torabi 
AU  - Janaki, Daryosh Mohamadi 

TI  - Heating the Future: Solar Hot Water Collectors for Energy-Efficient Homes in Sweden
T2  - Energy Engineering

PY  - 2026
VL  - 123
IS  - 2
SN  - 1546-0118

AB  - The technical, economic, and environmental performance of solar hot-water (SWH) systems for Swedish residential apartments—where approximately 80% of household energy is devoted to space heating and sanitary hot-water production—was assessed. Two collector types, flat plate (FP) and evacuated tube (ET), were simulated in TSOL Pro 5.5 for five major cities (Stockholm, Göteborg, Malmö, Uppsala, Linköping). Climatic data and cold-water temperatures were sourced from Meteonorm 7.1, and economic parameters were derived from recent national statistics and literature. All calculations explicitly accounted for heat losses from collectors, storage tanks, and internal and external piping systems, and established solar-fraction equations and NPV methodology were applied. Sensitivity analyses were conducted to determine optimal collector area and hot-water storage volume. Additionally, a Monte Carlo uncertainty analysis (10,000 iterations, ±10%) and break-even subsidy/carbon-credit assessments were performed. The discount rate for NPV calculations was set at 0% for capital interest with a 5% reinvestment return over a 25-year lifespan. The highest annual solar heat yield (8017.5 kWh) was obtained in Malmö with 32 m<sup>2</sup> of ET collectors, meeting 52.7% of total heating demand. Annual CO<sub>2</sub> emissions were avoided by FP and ET systems by approximately ~9.07 and ~10.55 tonnes, respectively. Economic analysis showed that no payback was achieved without government allowance; however, at a $0.05/m<sup>2</sup> allowance, positive NPV was exhibited at all stations. Lower levelized heat costs were delivered by FP systems, while ET systems demonstrated consistent superiority under climatic and economic variability according to the Monte Carlo analysis. Optimal design parameters were identified as 32 collectors and a 1680 L heating buffer tank, and Sankey diagrams highlighted collector losses as the dominant inefficiency. It was concluded that properly designed SWH systems, when supported by targeted subsidies, can significantly reduce fossil-fuel demand and CO<sub>2</sub> emissions in Swedish residential buildings. This work provides the first city-specific technical–economic–environmental dataset for Sweden, establishes a foundation for a national solar-heating atlas, and informs policymaking toward 100% renewable energy targets; beyond the baseline evaluation, explicit subsidy and carbon-price thresholds, quantified uncertainty ranges, and loss-flow visualizations are also provided, reinforcing the robustness and policy relevance of the findings.
KW  - Optical losses; heating losses; net present value; gas boiler; buffer tank

DO  - 10.32604/ee.2025.070190