• Energy Research

The study presents an investigation of thermal energy consumption for heating in an educational building located in the north-eastern part of Poland in 2017–2020, after deep thermomodernization. An evaluation of the actual energy effects was made based on measurements carried out over a 4-year operational period. They were compared with the results of theoretical calculations included in the energy audit and an attempt was made to describe the reasons for the discrepancies. The planned and achieved economic efficiency indicators were assessed and the amount of reduction of pollutant emissions was determined. The performed analysis allowed for an assessment of the impact of deep thermomodernization in terms of reducing heat energy consumption for central heating purposes, as well as reducing greenhouse gas emissions such as CO2, SOx, NOx and benzo(a)pyrene to the atmosphere. The implementation of thermomodernization in buildings led to savings of about 43% in terms of heat energy consumption for heating and a reduction in pollutant emissions. The theoretical savings based on the audit were 50.4%. The obtained results show that deep thermomodernization contributes to the improvement of energy and ecological efficiency in educational buildings, however, without the possibility of using subsidies, the investment is unprofitable. All the obtained results were discussed with the available literature sources and have been summarized with appropriate conclusions.

This work presents the results of a study that used a model based on rough set theory (RST) to assess the brine temperature of vertical ground heat exchangers (VGHEs) to feed heat pumps (HP). The purpose of this research was to replace costly brine temperature measurements with a more efficient approach. The object of this study was a public utility building located in Poland in a temperate continental climate. The building is equipped with a heating system using a brine–water HP installation with a total capacity of 234.4 kW, where the lower heat source consists of 52 vertical ground probes with a total length of 5200 m. The research was conducted during the heating season of 2018/2019. Based on the data, the heat energy production was determined, and the efficiency of the system was assessed. To predict the brine temperature from the lower heat source, a model based on RST was applied, which allows for the analysis of general, uncertain, and imprecise data. Weather data, such as air temperature, solar radiation intensity, degree days of the heating season, and thermal energy consumption in the building, were used for the analysis. The constructed model was tested on a test dataset. This model achieved good results with a Mean Absolute Percentage Error (MAPE) of 12.2%, a Coefficient of Variation Root Mean Square Error (CV RMSE) of 14.76%, a Mean Bias Error (MBE) of −1.3%, and an R-squared (R2) value of 0.98, indicating its usefulness in estimating brine temperature. These studies suggest that the described method can be useful in other buildings with HP systems and may contribute to improving the efficiency and safety of these systems.

On the basis of experimental studies, the operational power of four borehole heat exchangers (BHE) under real conditions was determined. The research was carried out in 2018–2019. The theoretical power of the BHE was verified with its operating power. The amount of thermal energy absorbed from the ground by individual BHEs, the operating temperatures obtained at the inlet and outlet of the exchanger, the annual brine flow rate, and the average operating power of the tested wells in two heating seasons were compared and analyzed. Both in 2018 and 2019, none of the examined exchangers achieved an average unit capacity of a well. The aim of the work is to verify the specific ground thermal efficiency indicators adopted for the design of the lower heat source, determined using the computational method and the TRT test with data obtained on the basis of experimental tests. The differences between the results of the tests of the operating parameters of the analyzed BHEs were shown. The data obtained in real conditions is valuable in the research and development of the BHE system.

This research was carried out to compare selected forecasting methods, such as the following: Artificial Neural Networks (ANNs), Classification and Regression Trees (CARTs), Chi-squared Automatic Interaction Detector (CHAID), Fuzzy Logic Toolbox (FUZZY), Multivariant Adaptive Regression Splines (MARSs), Regression Trees (RTs), Rough Set Theory (RST), and Support Regression Trees (SRTs), in the context of determining the temperature of brine from vertical ground heat exchangers used by a heat pump heating system. The subject of the analysis was a public building located in Poland, in a temperate continental climate zone. The results of this study indicate that the models based on Rough Set Theory (RST) and Artificial Neural Networks (ANNs) achieved the highest accuracy in predicting brine temperature, with the choice of the preferred method depending on the input variables used for modeling. Using three independent variables (mean outdoor air temperature, month of the heating season, mean solar irradiance), Rough Set Theory (RST) was one of the best models, for which the evaluation rates were as follows: CV RMSE 21.6%, MAE 0.3 °C, MAPE 14.3%, MBE 3.1%, and R2 0.96. By including an additional variable (brine flow rate), Artificial Neural Networks (ANNs) achieved the most accurate predictions. They had the following evaluation rates: CV RMSE 4.6%, MAE 0.05 °C, MAPE 1.7%, MBE 0.4%, and R2 0.99.

In this paper, a method to determine the thermal conductivity coefficient λ in a 200 μm thick heat reflective paint layer, filled with polymer nanospheres with a Total Solar Reflectance (TSR) of 86.95%, is proposed and presented. For this purpose, a “hot box”-type (cube-shaped) test rig was built to carry out experimental tests to measure the temperature distribution on the surface of a double-layer wall containing the material under investigation. Together with the experimental studies, a CFD numerical model was prepared to understand the nature of flow and heat transfer inside the cube—the test chamber. Based on the proposed measurement and analysis method, the thermal conductivity coefficient of the heat reflective coating layer was λ = 0.0007941 W/m∙K.

Abstract The main aim of the thermomodernization of historic churches was to reduce energy consumption for heating and improve air quality by reducing the amount of pollutants emitted into the atmosphere. Calculation methodology was adopted in accordance with the Decree of the Minister of Infrastructure on the detailed scope and form of an energy audit [4] , [5] and based on the fuel indexes (WO) and CO2 emission (EC) for reporting under the Community Emissions Trading [13] . We have achieved a significant reduction of the annual heat demand and the reduction of emissions: SO2, NOx, CO2 and dust as a result of the modernization, with the exception of the Church in Chlopkow (No. 1). The results of the energy and environmental analysis show the validity of the religious buildings thermomodernization and upgrading their heat sources. These effects are necessarily connected with the economic effects. Practical application of this paper was to show the possibility of carrying out thermomodernization upgrades for reducing demand for heating, for thermal power and protecting the environment.

Abstract The aim of the installation of photovoltaic panels in the object of the Water Park was to use the possibility of supporting the production of electricity using solar energy. The article shows the adopted technological solution installation of photovoltaic and presents the results of the analysis of plant performance in real conditions, not just computational theory. The analysis of the installation work was performed on the basis of monitoring of operating parameters conducted in 2012–2013. The use of photovoltaic helped reduce CO2, SO2, NOx and dust emissions into the atmosphere on the value of installed power and reduce the amount of electricity drawn from the network (In Poland still based on coal and lignite). The results of energy and environmental analysis show the validity of installation of photovoltaic in objects like Water Parks. Energy and environmental effects combine necessarily the economic effects. It also helps to promote the local market to other forms of energy generation as well as improves the energy security of the Warmia and Mazury province, as well as part of the European Climate Change Programme (ECCP), which has lead to coordination of activities towards the reduction of greenhouse gas emissions.

Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.

In this study, based on 19 years of research, an analysis of thermal energy consumption for heating was carried out on a group of 22 residential multi-family buildings located in a temperate continental climate. The buildings were constructed with two different technologies based on prefabricated elements, and most of them were equipped with central heating cost allocators. A predictive control system for the central heating system was installed in the analyzed buildings, followed by a deep thermo-modernization. An evaluation was made regarding whether the use of a change in the method of central heating control, from the traditional one, which takes into account only the variable external temperature, to weather control, increases the energy efficiency of the thermo-modernized buildings. In addition, the cost-effectiveness of the modernization measures was analyzed by determining economic efficiency indicators; therefore, it was possible to identify the modernization variant that, with limited investment costs, could achieve the best energy efficiency resulting from the European energy policy.