Analysis and selection criteria of photovoltaic panels for DHW

The article discusses the issue of selecting power of photovoltaic panels for heating domestic hot water (DHW). It is indicated that the price of installation is several times lower than a couple of years ago. The authors present a method of selecting system power depending on DHW installation’s heating requirements and the building’s energy consumption. This algorithm allows for central heating requirements that are crucial in case of heating a building with solid fuel appliances. The described selection method uses heating power details obtained while drawing up Energy Performance Certificates, or the so-called heating degree-days, which enable to precisely determine the heating requirements in individual days of the year and select appropriate power of PV installation for the building’s energy performance. In addition, the authors have calculated the heating losses occurring in different elements of installation and showed their influence on the system’s power selection. The last part discusses the possibility of integrating PV installation used for heating DHW with the building’s central heating system, in order to use the energy surplus

Model for the Discharging of a Dual PCM Heat Storage Tank and Its Experimental Validation

The important topic of modelling tanks filled with phase change materials (PCMs) is discussed in this article. Due to the increasing use of heating and cooling installations, tanks containing two types of PCMs are the subject of many experimental analyses. However, there are still deficiencies in their models, which are presented in this paper. The theory model was created in order to design two tanks, each with a volume of 2 m3. They were filled with water and containers with two PCMs. The modelled tanks were meant to replace the existing water tanks that were previously used in the solar heating and cooling installation in a research building located in the southern part of Spain. After the tanks were assembled, the model was validated during the summer period when the designed storage tanks supported the operation of the solar system operating in the cooling mode. The created model consists of a 1D description of the heat transfer in the storage tank, and also a 1D description of the phase change in the containers with the PCMs. The model takes into account the front of the phase change and also discusses its impact on the thermal efficiency of the tanks. The agreement of the water output temperature is very good and validates the model, which can then be used to provide further details on the operation of the storage system—in particular, heat fluxes or a fraction of solid or liquid PCM

Development and Results from Application of PCM-Based Storage Tanks in a Solar Thermal Comfort System of an Institutional Building—A Case Study

An important element of a solar installation is the storage tank. When properly selected and operated, it can bring numerous benefits. The presented research relates to a project that is implemented at the Solar Energy Research Center of the University of Almeria in Spain. In order to improve the operation of the solar cooling and heating system of the Center, it was upgraded with two newly designed storage tanks filled with phase change materials (PCM). As a result of design works, commercial material S10 was selected for the accumulation of cold, and S46 for the accumulation of heat, in an amount of 85% and 15%, respectively. The article presents in detail the process of selecting the PCM material, designing the installation, experimental research, and exergy analysis. Individual tasks were carried out by research groups cooperating under the PCMSOL EUROPEAN PROJECT. Results of tests conducted on the constructed installation indicate that daily energy saving when using a solar chiller with PCM tanks amounts to 40% during the cooling season

Analysis and selection criteria of photovoltaic panels for DHW

The article discusses the issue of selecting power of photovoltaic panels for heating domestic hot water (DHW). It is indicated that the price of installation is several times lower than a couple of years ago. The authors present a method of selecting system power depending on DHW installation’s heating requirements and the building’s energy consumption. This algorithm allows for central heating requirements that are crucial in case of heating a building with solid fuel appliances. The described selection method uses heating power details obtained while drawing up Energy Performance Certificates, or the so-called heating degree-days, which enable to precisely determine the heating requirements in individual days of the year and select appropriate power of PV installation for the building’s energy performance. In addition, the authors have calculated the heating losses occurring in different elements of installation and showed their influence on the system’s power selection. The last part discusses the possibility of integrating PV installation used for heating DHW with the building’s central heating system, in order to use the energy surplus

Investigation of the efficiency of a high temperature heat storage charging

The article presents the results of the test of a heat storage filled with chamotte brick. The air parameters were used as the basis for determining the heat stream represented by a working medium, which was then compared with the stream accumulated in the material filling the deposit. Additionally, heat streams were shown for individual segments of the deposit. The efficiency of heat accumulation was determined for each of them. They showed that the efficiency of accumulation process was highest in the deposit’s first segments and the lowest in the last segments, where the air was the coldest. The dynamics of the efficiency’s shift was different for each of the observed segments. In the area closest to the inlet of hot air, the dynamics of the process of heat accumulation decreased the fastest and after one hour only a slight increase of efficiency was visible in the function of time. In the accumulation material placed closest to the outlet, the process of absorbing heat was very fast, starting from the 20th minute before the tests were completed. The smallest changes in the process’ character, throughout the whole time of testing, were recorded in the middle layer

A Granite Bed Storage for a Small Solar Dryer

The article presents the concept of a high-temperature solar dryer with an internal bed storage. Granite was selected as the material for filling the bed storage, and an emphasis was put on its versatile use and favourable thermal and mechanical properties. Experimental tests were carried out for the charging process of the bed storage, which was filled with granite spheres with three different diameters. The influence of the sphere’s diameter on the charging and discharging process of the bed storage was analysed. The results of the experiment allowed a conclusion to be drawn that the use of a granite storage bed could prolong the operation of the considered dryer by two hours

Investigation of the efficiency of a high temperature heat storage charging

The article presents the results of the test of a heat storage filled with chamotte brick. The air parameters were used as the basis for determining the heat stream represented by a working medium, which was then compared with the stream accumulated in the material filling the deposit. Additionally, heat streams were shown for individual segments of the deposit. The efficiency of heat accumulation was determined for each of them. They showed that the efficiency of accumulation process was highest in the deposit’s first segments and the lowest in the last segments, where the air was the coldest. The dynamics of the efficiency’s shift was different for each of the observed segments. In the area closest to the inlet of hot air, the dynamics of the process of heat accumulation decreased the fastest and after one hour only a slight increase of efficiency was visible in the function of time. In the accumulation material placed closest to the outlet, the process of absorbing heat was very fast, starting from the 20th minute before the tests were completed. The smallest changes in the process’ character, throughout the whole time of testing, were recorded in the middle layer

Linear concentrating collector as an air heater in the heating system of building in Polish climatic conditions

The article presents the analysis of the performance of a concentrating collector in the heating system of a residential building. Air was used as the working fluid. The heating requirements of the building were determined for each day of the year. The amount of direct irradiation reaching the absorber’s surface on all the days of the year was determined with the use of hourly meteorological data for Wroclaw, shared by the Ministry of Infrastructure and Growth. It was assumed that the collector is equipped with a tracking system working in one axis. Calculations and comparisons were made for the amount of solar irradiation for three values of the receiver’s inclination angle: β1=60°, β2=90° and β3=30°. Statistical method was used in order to determine the optimum inclination of the mirror and the amount of flowing air. This method involves creating a plan of experiment with three levels of changeability for two input factors. In the last stage, the amount of heat obtained from the installation during all the days of the year was analysed. The gains were juxtaposed on the diagram with the building’s heat demand. The analysis has shown that the heat requirements can be met only partially

The Influence of the Shape of Granite on the Heat Storage Process in a Rock Bed

Granite is one of those materials that due to its thermal parameters is used as a filling for storage beds, including high-temperature ones. The article analyzes local material that was extracted in Strzegom, Poland. The purpose of the paper is the assessment of storage material with regard to its cooperation with a heat source that is available for a short time, e.g., a solar installation. Three different shapes of granite material were tested: rock, cube and sphere. Each shape has its advantages and disadvantages, which are associated with economic and strength aspects. The article presents experimental tests of the material, which were conducted in order to determine the efficiency of the charging process. The results show that rock-shaped granite filling elements are characterized with the best parameters during the charging process, and that they obtained the highest first- and second-law efficiency in the entire tested range of inlet air temperature and flow rate. The efficiency of the cube-shaped granite was lower than the sphere-shaped granite. This means that the efficiency does not directly depend on the coefficient of sphericity of the elements that fill the storage bed. The determination of the second law efficiency showed that the highest use of energy supplied with hot air occurs after 1 h of charging the accumulator in the case of all the analyzed geometries. At the end of the paper, the influence of the obtained results on the process of modelling the charging of a storage bed filled with elements of non-spherical geometry is also discussed

Analysis of the Possibilities of Using a Heat Pump for Greenhouse Heating in Polish Climatic Conditions—A Case Study

This article presents an analysis of selecting a seasonal heating system for an existing greenhouse. The analyzed object is located in Poland near Wroclaw, where summer flowers are grown. Appropriate thermal conditions must be ensured continuously for four heating months. The primary source of heat in the examined flower greenhouse was a coal-fired furnace. The analysis presented in the article shows a method of thermal balancing the object, determining heat demands in the analyzed period using the experiment plan, and also selecting a new heating system in the form of a heat pump. The analysis of the operation of the heating system was performed for air and ground source heat pumps to determine the profitability of their application in Polish climatic conditions. An economic analysis was also included and the investment impact on pollution emissions was calculated