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This study presents a research of envelope systems entailing elements that use and control incident solar energy to deliver renewable thermal or electric energy to the systems providing heating, ventilation and air conditioning to buildings. A simulation model of an office building was developed in the simulation program TRNSYS. A photovoltaic / thermal system was integrated into the building´s southern facade to generate electricity and to increase the temperature of the air flowing through the channel behind the photovoltaic modules. Subsequently, the electricity generated was used to power the heat pump and the warm air was used as the primary fluid for the heat pump to generate thermal energy for space heating in the winter. The useful energy gain and power production increased with increasing length of the photovoltaic modules and the air flow rate through the channel in the periods, when there was enough solar radiation impinging on the facade. In January to April, the benefits of the photovoltaic / thermal system were minor because of the low levels of low solar radiation and insufficient efficiency of the system components.

A new way of obtaining the algebraic relation between the nodal values in a general one-dimensional transport equation is presented. The equation can contain an arbitrary source and both the convective flux and the diffusion coefficient may vary arbitrarily. Contrary to the usual approach of approximating the derivatives involved, the algebraic relation is based on the exact solution written in integral terms. The required integrals can be speedily evaluated by approximating the integrand with Hermite splines or applying Gauss quadrature rules. The startling point about the whole procedure is that a very high accuracy can be obtained with few nodes, and more surprisingly, it can be increased almost up to machine accuracy by augmenting the number of quadrature points or the Hermite spline degree with little extra cost. [ABSTRACT FROM AUTHOR]

Globally, rising temperatures, together with the growing population, urbanization, and improved living standards, are driving a sharp increase in energy demand in the building sector. Space cooling and heating are the major areas of energy consumption. The building's roof slab thermal performance significantly impacts the heating and cooling requirements. Various studies investigated incorporating phase change material (PCM) to enhance the thermal characteristics of roof slabs. In this paper, the effective utilization of macro-encapsulated PCM in reinforced cement concrete (RCC) roof slab is investigated numerically. This research explored the effect of shape, heat transfer area, and thermal shading with the same amount of PCM on the impact of the reduction of inner roof temperature. Validation of the model with the experimental results is done for the current study. A total of 12 different cases, along with a reference case, were examined. In addition, the structural performance of the RCC conventional slab and slab with PCM capsules is also examined. Findings of the study include: cuboid with less thickness was found as the best shape. The increment in heat transfer area leads to better thermal performance while also providing the best case, with 3.2 °C and 1.2 °C peak and average temperature reduction. The thermal shading phenomenon was found to have positive results for the winter solstice. The deflection of all the slab cases was observed to be within the limits.