• Energy Research

Abstract In this paper, a novel design of counter flow curved double-pass solar air heater (DPSAH) is proposed, and its performance characteristics are numerically investigated and compared with various parallel designs under different flow and geometric conditions. The developed model is first experimentally validated. The hydraulic and thermal performance of various DPSAH designs (smooth curved single pass, smooth parallel curved double-pass, smooth counter curved double-pass, roughened parallel curved double-pass, and roughened counter curved double-pass) show that counter flow curved DPSAH with asymmetrically placed turbulators is thermally better compared to other designs. A maximum of 23% augmentation in thermal performance was observed. To predict the performance of the best design, new correlations for Nusselt number (Nu) and friction factor (f) are developed in terms of Reynolds number (Re) and relative roughness height (d/H). The data estimated from these correlations are in good agreement with the values of f and Nu predicted from the model.

Abstract In this paper, a novel design of counter flow curved double-pass solar air heater (DPSAH) is proposed, and its performance characteristics are numerically investigated and compared with various parallel designs under different flow and geometric conditions. The developed model is first experimentally validated. The hydraulic and thermal performance of various DPSAH designs (smooth curved single pass, smooth parallel curved double-pass, smooth counter curved double-pass, roughened parallel curved double-pass, and roughened counter curved double-pass) show that counter flow curved DPSAH with asymmetrically placed turbulators is thermally better compared to other designs. A maximum of 23% augmentation in thermal performance was observed. To predict the performance of the best design, new correlations for Nusselt number (Nu) and friction factor (f) are developed in terms of Reynolds number (Re) and relative roughness height (d/H). The data estimated from these correlations are in good agreement with the values of f and Nu predicted from the model.

This paper assesses the performance of waste heat recovery from commercial kitchen wastewater in practice. A pilot study of heat recovery from the kitchen at Penrhyn Castle, a tourist attraction in North Wales (UK), is outlined. The pilot heat recovery site was designed and installed, comprising a heat exchanger, recirculation pumps, buffer tank and an extensive temperature/flow monitoring system for performance monitoring of the waste heat recovery system. Continuous monitoring was conducted for a period of 8 months, covering the 2022 tourist season. The recovered heat from the kitchen wastewater preheats the incoming cold freshwater supply and consequently reduces the amount of energy consumed for subsequent water heating. Retrofitting the pilot heat recovery system to the kitchen drains resulted in a heat saving of 240 kWh per month on average, a reduction of 928.8 kg CO2e per year, and a payback period for the investment costs of approximately two years, depending on the cost of energy supply. The presented results illustrate the potential of this form of renewable heat in reducing the carbon footprint of water heating activities in buildings and the hospitality sector.

This paper assesses the performance of waste heat recovery from commercial kitchen wastewater in practice. A pilot study of heat recovery from the kitchen at Penrhyn Castle, a tourist attraction in North Wales (UK), is outlined. The pilot heat recovery site was designed and installed, comprising a heat exchanger, recirculation pumps, buffer tank and an extensive temperature/flow monitoring system for performance monitoring of the waste heat recovery system. Continuous monitoring was conducted for a period of 8 months, covering the 2022 tourist season. The recovered heat from the kitchen wastewater preheats the incoming cold freshwater supply and consequently reduces the amount of energy consumed for subsequent water heating. Retrofitting the pilot heat recovery system to the kitchen drains resulted in a heat saving of 240 kWh per month on average, a reduction of 928.8 kg CO2e per year, and a payback period for the investment costs of approximately two years, depending on the cost of energy supply. The presented results illustrate the potential of this form of renewable heat in reducing the carbon footprint of water heating activities in buildings and the hospitality sector.

Abstract This paper examines the possibility of integrating a photovoltaic (PV) module in a hybrid solar chimney power plant (HSCPP). Since HSCPP is a greenhouse thermal buoyancy-driven system, the surrounding high temperature environment makes PV module temperature extremely high resulting in lower electrical conversion efficiency. Various design configurations of collector duct and solar chimney are investigated using an experimentally validated numerical model to study the PV panel cooling and turbine power output. The results show that turbine power output is sensitive to diverging the chimney up to maximum static pressure recovery limit while PV module shows marginal increase in electrical efficiency. Converging the collector duct alone shows worst turbine and PV module performance. However, in case of combine designs of converging duct and divergent chimney, considerable improvement of PV panel efficiency (about 7%) was observed. The results show that about 80% of the collector area measured from the chimney axis are the most effective region for cooling the PV module where consistent temperature drop of 10–12 °C was observed. A design map vs. PV panel efficiency has been shown charting future directions for designing such energy efficient hybrid solar chimney systems.

Abstract This paper examines the possibility of integrating a photovoltaic (PV) module in a hybrid solar chimney power plant (HSCPP). Since HSCPP is a greenhouse thermal buoyancy-driven system, the surrounding high temperature environment makes PV module temperature extremely high resulting in lower electrical conversion efficiency. Various design configurations of collector duct and solar chimney are investigated using an experimentally validated numerical model to study the PV panel cooling and turbine power output. The results show that turbine power output is sensitive to diverging the chimney up to maximum static pressure recovery limit while PV module shows marginal increase in electrical efficiency. Converging the collector duct alone shows worst turbine and PV module performance. However, in case of combine designs of converging duct and divergent chimney, considerable improvement of PV panel efficiency (about 7%) was observed. The results show that about 80% of the collector area measured from the chimney axis are the most effective region for cooling the PV module where consistent temperature drop of 10–12 °C was observed. A design map vs. PV panel efficiency has been shown charting future directions for designing such energy efficient hybrid solar chimney systems.

Abstract In this paper, we report the investigation of various curved solar air heater designs that shows significant enhancement of heat transfer. We have taken the initial design proposed in the reference: Mahboub, C., Moummi, N., Brima, A., Moummi, A., 2015. Experimental study of new solar air heater design. International Journal of Green Energy 13, 521–529, and incorporated promising design modifications to further look for the avenues for thermal efficiency enhancement features. The Computational Fluid Dynamic (CFD) model was first validated by the results reported by Mahboub et al. It was observed that secondary vortex formation near the absorber wall increases the Nusselt number significantly. New correlations for friction factor and Nusselt number has been developed as a function of Reynolds number and various geometric parameters such as relative groove height and pitch ratios for different design of air heaters. It is hoped that data of parameters i.e. Nusselt number (Nu), outlet air temperature (To), thermal efficiency (ηth) and friction factor (f) presented in this paper would help researchers and industry in developing efficient designs of solar collectors.

Abstract In this paper, we report the investigation of various curved solar air heater designs that shows significant enhancement of heat transfer. We have taken the initial design proposed in the reference: Mahboub, C., Moummi, N., Brima, A., Moummi, A., 2015. Experimental study of new solar air heater design. International Journal of Green Energy 13, 521–529, and incorporated promising design modifications to further look for the avenues for thermal efficiency enhancement features. The Computational Fluid Dynamic (CFD) model was first validated by the results reported by Mahboub et al. It was observed that secondary vortex formation near the absorber wall increases the Nusselt number significantly. New correlations for friction factor and Nusselt number has been developed as a function of Reynolds number and various geometric parameters such as relative groove height and pitch ratios for different design of air heaters. It is hoped that data of parameters i.e. Nusselt number (Nu), outlet air temperature (To), thermal efficiency (ηth) and friction factor (f) presented in this paper would help researchers and industry in developing efficient designs of solar collectors.