In recent years, the summer season in Iraq has become longer and hotter than before, leading to high cooling loads inside buildings and increased demand for electrical energy. The use of sustainable energy and insulation techniques for building envelopes are reasonable solutions for overcoming harsh weather conditions and reaching acceptable thermal comfort levels. In this study, a survey on more than 60 residential buildings in Al-Amarah City, Iraq, was conducted on 21 July 2018 to examine the nature of the most common construction materials used in the building envelopes. Furthermore, the cooling loads of building envelope elements, e.g. roof, external walls and windows, was calculated using the cooling load temperature difference/solar cooling load/cooling load factor method of ASHRAE. The results were tabulated and compared for each combination of elements. The results showed that reflective glass is the optimal choice for exterior windows. The 'clay"“insulation"“fired clay bricks"“cement mortar' and 'cement mortar"“thermo-stone bricks"“cement mortar"“gypsum mortar' combination layers performed well for roof and external wall installations, respectively. Several recommendations were deduced from this study, which can be used as guidelines for construction authorities in Al-Amarah City and individuals interested in energy-efficient buildings.

Purpose: – The purpose of this paper is to explore a model for thermal convection in a plane layer when the density-temperature relation in the buoyancy term is quadratic. A heat source/sink varying in a linear fashion with a vertical height expressed as z was allowed, functioning as a heat sink in an area of the layer and as a heat source in the remainder. Design/methodology/approach: – First, the authors present the governing equations of motion and derive the associated perturbation equations. Second, the authors introduce the linear and nonlinear analysis of the system. Third, the authors transform the system to velocity-vorticity-potential formulation and introduce a numerical study of the problem in three dimensions. Findings: – First, the linear instability and nonlinear stability thresholds are derived. Second, the linear instability thresholds accurately predict the onset of instability. Third, the required time to arrive at the steady state increases as Ra tends to RaL. Fourth, the authors find that the convection has three different interesting patterns. Originality/value: – With the modernday need for heat transfer or insulation devices in industry, particularly those connected with nanotechnology, the usefulness of a mathematical analysis of such resonance became apparent. Thus, this study is believed to be of value.

The operational temperature highly influences the efficiency of the solar photovoltaic (PV) module, in which high temperature decreases the output power accordingly. In this work, a polycrystalline PV module is modified using a finned phase change material (PCM) panel attached to the rear as a thermal energy storage unit to decrease and regulate the operating temperature under hot weather conditions in southern Iraq. For this purpose, local Iraqi paraffin wax is used as a PCM loaded into a galvanized steel panel that has internal smooth wavy fins to improve the PCM poor thermal conductivity and accelerate its melting and solidification rates. Experimental results showed that the modified PV module temperature is decreased by up to 16°C compared with the reference PV module, resulting in maximum output power of up to 38.4% more than an identical reference PV module. Moreover, the electrical efficiency of the modified PV module is improved respectively by 34% and 37.2% on the first and second day of the experiment over the reference PV module, indicating remarkable electrical and thermal performance improvement.