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Increasing the level of energy efficiency and using renewable energy sources in the design and existing buildings is an important aspect in minimizing the carbon dioxide emissions and mitigating the climate changes. One of such solutions may be the application of a heating system using residential thermal stations (RTSs) for heating and hot water preparation individually in the premises of a given building. The main purpose of this paper was to analyze long-term filed research results on the energy consumption and efficiency of heating systems in a dormitory (building B1) and two multifamily buildings (building B2 and B3) equipped with residential thermal stations (RTSs) that are used for supplying individual dwellings with heat, as well as hot and cold water. An additional aspect of the analysis is a presentation of the structure of total energy consumption for particular purposes in the analyzed buildings and the possibilities to increase the share of renewable energy sources using solar thermal collectors for supporting the analyzed heating system.

Nowadays, the attention of designers and service providers is especially focused on energy efficiency and integration of renewable energy sources (RES). However, the knowledge on smart devices and automated, easily applicable algorithms for optimizing heating consumption by effectively taking advantage of solar heat gains, while avoiding overheating, is limited. This paper presents a simple method for taking into account the influence of solar heat gains in the form of solar radiation for the purposes of forecasting or controlling thermal power for heating of buildings. On the basis of field research carried out for seven buildings (five residential buildings and two public buildings) during one heating season, it was noticed that it was justified to properly narrow down the input data range included in the building energy model calculations in order to obtain a higher accuracy of calculations. In order to minimize the impact of other external factors (in particular wind speed) affecting the heat consumption for heating purposes, it was recommended to consider the data range only at wind speeds below 3 m/s. On the other hand, in order to minimize the impact of internal factors (in particular the impact of users), it was suggested to further narrow down the scope of the input data to an hour (e.g., 10–14 in multi-family residential buildings). During these hours, the impact on users was minimized as most of them were outside the building.

Abstract The energy efficiency of existing buildings may be increased by using new control techniques of their heating systems, especially if such methods are validated and easy to install. Hence, short-term forecasting of heat power demand is needed, in order to optimize their operation. This work presents a simple, new method of short-term forecasting of heat power for space heating, which may be easily applied in existing buildings. The method is first presented and then validated with two case studies, a multifamily building and a school, using hourly data from three heating seasons. It was found that beyond the outdoor meteorological parameters the accuracy of the method is improved by including the equivalent indoor temperature as the parameter related to the effect of the building occupant behavior. Accordingly, the resulting mean absolute percentage error of the predicted heat demand using the proposed prediction method was 3.2% and 12.0% for the two buildings. Compared to a simple model of the heat poser demand that is based only on the outdoor temperature error was lower by 61.4% and 43.2% for two buildings respectively. In addition, five profiles of equivalent indoor temperature were proposed in order to select the most accurate one for a specific building. This method may be also used in the process of predictive control of heating systems, because the external and internal parameters are measurable and predictable, which will contribute to more energy efficient systems in existing and new buildings.

AbstractThis work presents the results of experimental studies on the energy performance of an evacuated solar collector, heat pipe type, consisting of 24 tubes, over the period of 2 months. The solar collector with a gross area of 3.9 m2 is part the solar hot water test system located in Lublin (Poland). The effect of the weather conditions and operating parameters on the thermal and exergy efficiencies of the evacuated tube solar collector has been defined. The solar irradiation per month for July amounted to 80 kWh/m2, and for August, it equalled 112.8 kWh/m2. The average thermal gain was found to be in July 163 W/m2 and in August 145 W/m2, respectively. For the considered study period, the average value of energy yield in the solar collector was obtained at the level of 4.28 MJ/(m2·d). The average monthly energy efficiencies of the solar collector in July and August were 45.3% and 32.9%, respectively, while the average monthly exergy efficiencies reached 2.62% and 2.15%, respectively. Increasing the wind speed to 0.86 m/s decreases the thermal efficiency and the exergy efficiency by 67% and 41%, respectively.