Abstract
In this study, the usefulness of adding a solar system to a domestic hot water supply system (boiler) was investigated. The amount of hot water consumption was determined taking into account hot water usage on workdays and weekends. Considering the amount of global horizontal irradiation 2328.2kwhm2.year for southwest region (Wadi Al-Dawasir) in Saudi Arabia and using transient analysis, the heat gain in collectors was specified at the optimal tilt. The results showed that by adding a solar system (which used water at 30 kghr) the boiler power usage reduced by 21,389 kWh per year. Based on numerical calculations, the higher flow rates in collector (60 and 90 kghr), the lower energy saving (19550 and 18663kWhyear). Dispersing nanoparticles of Pentaethylene Glycol-Treated Graphene Nanoplatelets (GNPs + PEG) into water at 0.025–0.1 vol% led to a superior energy-saving. At 30 kghr, owing to using GNPs + PEG/water at 0.025 vol%, energy saving improved by 1080kWhyear (from 21,389 to 22,469 kWhyear). Loading more nanoparticles resulted to higher energy-saving so that at 0.1 vol%, it was 23,376 kWhyear. Under the best case conditions and owing to using solar system, the boiler energy usage reduced by 26.8% (for water) and 29.3% (for GNPs + PEG/water 0.1 vol%).