Transient Simulation of a Building-Integrated Hybrid Solar Collector/Nocturnal Radiator with In-Built Thermal Storage for Space Cooling in Owerri, Nigeria

The transient model of a hybrid solar collector/nocturnal radiator with thermal energy storage for solar water heating and its nocturnal radiative cooling was deployed in simulating space comfort cooling in Owerri in southeast Nigeria. The physical system comprises a spectrally selective absorber with 12 copper tubes spaced 0.1 m apart, an area of $1.704{\mathrm{m}}^2$, a thickness of $1.03\times {10}^{-3}\mathrm{m}$, a 20-μm-thick polyethylene film 20 mm from the absorber surface, and two 300-L hot- and cold-water storage tanks installed in a $142.6\text{-}{\mathrm{m}}^3$-envelope room. Water was pumped at a flow rate of $8.33\times {10}^{-2}\mathrm{kg}/\mathrm{s}$ from the two tanks through the system for daytime heating and nighttime cooling, respectively. The following day, cooled water from the cold storage tank was utilized to provide comfort cooling within the envelope room. The temperature histories of the different components that make up the system, namely, the hybrid SCONOR, cold storage tank, and building indoor (room) temperatures, as well as the energy absorption and losses from the hybrid plate, were studied. The results obtained show that maximum energy absorption occurred around the bond region, whereas the lowest energy absorption was along the collector fin width. Also, after sunset, the SCONOR witnessed continuous losses until it reached the ambient state for nocturnal radiation to commence. Water cooled to a minimum of 18°C during nocturnal radiative cooling phase, while the cooled space temperature fluctuated between 26.6°C and 26.8°C. The indoor room temperature depression varied over 0.1°C–5.7°C from ambient temperature. Ambient temperature ranged from 25.6°C to 32.5°C during the day. Parametric analyses showed that an aluminum substrate showed the best promise in terms of the thermal performance of the integrated energy system.