No abstract

Passive solutions in buildings have recently been rediscovered because they allow the rational use of solar radiation, which promotes energy savings. Thermal energy gained from the sun may be stored in the form of sensible heat in accumulative solid materials in a building envelope. This paper proposes an innovative solar air heater that captures and accumulates solar energy during the day and releases it during the night. The analyzed system is based on inexpensive ceramic modules, which can be used to construct thermal storage walls or solar chimneys in modern buildings. Both configurations have been tested experimentally and by a numerical model in ArCADia BIM software. Experiments have been carried out in laboratory conditions using a specially developed prototype. Among other parameters, power transferred from the solar air heater to the ventilation air in different conditions has been analyzed. When airflow was set to 150 m3/h, the maximum power observed under stable working conditions was approx. 355.0 W when the developed solar air heater operated as the solar chimney, and approx. 165.0 W when it operated as the solar thermal wall. When airflow was set to 200 m3/h, the maximum power was approx. 385.0 W. Experimental results have been used to calculate the efficiency of the solar air heater in real conditions. The total efficiency in the case of the solar chimney was estimated as 0.25, while in the case of the thermal wall it was estimated as 0.78, which resulted in an annual reduction in energy usage at a level of 190.7 kWh and 556.1 kWh, respectively (4.8 and 14.0%). In practice, these values can be significantly higher due to the possibility of increasing the length and shape of the accumulation heat exchanger.

During last years, renewable energy sources (RES) find their way into the transportation industry. Among the units which may be powered directly with renewable energy, the UAVs (unmanned aerial vehicles) market is undergoing a rapid development. In this case mainly the solar energy is used. Photovoltaic modules are mainly located on the wings, so it is often necessary to use flexible PV cells which have lower efficiency than the flat ones. This study proves that airfoil geometry modifications by partial flattening are not beneficial from the aerodynamic point of view. The lower energy conversion on photovoltaic panels must be balanced by energy storage and energy management systems. The performance of exemplary installation mounted on AGH Solar Plane has been modelled with TRNSYS software. Obtained results allowed to establish the amount of produced, stored and used energy in six different months.

One of waste heat recovery technologies are thermoelectric generators, which allow direct conversion heat to energy. In the face of shrinking fossil fuels resources, simultaneous increase of global energy demand and level of pollution it is becoming more and more important to introduce technologies enabling fullest utilization of fuels. In the paper, tests of water and air cooled thermoelectric generators mounted on the stove were described. Problems that occurred while operation of the system and its solutions were presented. Analysis of factors influencing incineration process, therefore affecting produced electrical energy was carried out. Power and voltage-current characteristics of generators were drawn up. A possible electrical energy yield in conditions described in this paper was also estimated.

Nowadays, almost 30% of total energy consumption (130 EJ) is consumed for the operation of buildings, mainly by space heating/cooling and ventilation systems, hot water preparation systems, lighting, and other domestic appliances. To improve the energy efficiency of buildings, several countries are promoting the use of renewable energy. The most promising systems include active and passive solar installations. In passive systems, the solar energy is collected, stored, reflected, or distributed by the roof ponds, natural convective loops, and the most popular direct gain walls and thermal storage walls (known as Trombe walls). This paper reviews the experimental and numerical studies devoted to the different solutions of Trombe walls, including solar chimneys integrated on the vertical walls, classic Trombe walls, Trombe walls with incorporated phase change materials, and photovoltaic Trombe walls. The actual state of the art is presented in the context of reducing energy consumption and enhancing thermal comfort. Most of the analyzed studies showed that the application of thermal storage walls allowed achieving these goals, led to lower emissions of greenhouse gases, and improved living standards. Nevertheless, there is a need for more detailed feasibility studies, including cost and environmental indicators.

Nowadays, photovoltaic systems installed in urban areas have to be an essential part of distributed generation systems, and lead to improve energy efficiency of buildings. The paper describes the operation aspects of the 7,5 kWp photovoltaic installation located on the roof of the didactic building of AGH University of Science and Technology. The significant part of the roof Is occupied by HVAC installation, so the periodic shading is occurring. It makes, that a level of energy generated in the PV system is lower than expected. The first part of the test was focused on the validating model of the installation and determine its impact on the CO2 emissions. Then, modifications in the arrangement of the panels were considered (redirecting of additional light stream). Moreover, an economic and environmental analysis of proposed improvements were conducted.

No abstract

No abstract