• Energy Research

Abstract The use of pre-set thermostatic radiator valves (TRVs) contributes to the reduction of energy consumption and the increase of the energy efficiency of the existing heating systems in buildings. However, there are limited long-term experimental studies that document the level of energy savings achieved by the use of TRVs, quantified for three different options of their utilisation. Long-term field data were collected over several heating seasons from nine existing multifamily residential buildings organized into three groups characterized by different modernization activities using TRVs. The first group includes the cases where the buildings are equipped with TRVs without hydraulic balance of the heating system with pre-set TRVs; the second group encompasses buildings that were already equipped with TRVs and then a hydraulic balancing of the heating system was performed by means of a pre-set; finally, the third group of buildings considers the simultaneous installation of TRVs and hydraulic balancing of the heating system using pre-set TRVs. The energy savings ranged between 7.1% and 23.3%, depending on the range of modernization activities using TRVs with or without hydraulic balance. The payback time was less than 2.5 heating seasons in all cases.

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.

The radiant floor heating/cooling systems are more often used in new designed and modernized buildings, what renewed the interest in the study of the characteristic parameters, which are taking in to account by dimensioning or detailed scientific analyzes of such a systems. Very important and fundamental characteristic parameters for radiant floor are heat transfer coefficients. This article presents the results of experimental research on heated/cooled radiant floor conducted in the laboratory room in the climatic chamber, which aim was to estimate experimentally the values of heat transfer coefficients for the surface of cooled/heated radiant floor. The values of radiant, convective and total heat transfer coefficients were developed on the basis of the amount of heat emitted from the radiant surface and by the use of proper and clearly defined reference temperature depending on the kind of heat transfer coefficient. It was noticed, that the values of heat transfer coefficients for heated/cooled radiant floor, which are commonly used in practice, are overestimated, even in the range of 10–30%.

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.

Abstract Smart control of energy supply to the existing buildings may increase their energy efficiency. However, to the best of the authors’ knowledge, there are no simple, general, automated, widely applicable and accurate methods for the creation of energy model of the building, which may be used to calculate the actual energy consumption of a heating system or for their prediction. This work presents a new simplified method for generating the energy characteristics of buildings and their heating systems, without the influence of occupants. The method requires as input only the actual heat supplied to the heating system and the local outdoor weather conditions (i.e. temperature, wind speed and solar insolation) of a building. The output is a building energy model in terms of an equivalent outdoor temperature. It was found that when determining the correction due to the wind, the data from the night hours (e.g. from 11.00 p.m. to 4.00 a.m.) should be used in order to exclude the impact of solar radiation and minimize the interaction of users. On the other hand, the correction due to the influence of solar radiation should be obtained using data with low wind speeds and time periods from 10.00 a.m. to 2.00 p.m. on weekdays for residential buildings or from 10.00 a.m. to 2.00 p.m. on the weekend for public buildings in order to minimize disruptive effects of wind speed and the impacts from occupants. This method may be used to generate a simple building energy model and to accurately determine the duration and the amount of heat power supplied to a building for space heating, for periods when the impact of occupants and other internal heat gains are kept to a minimum.

Abstract The application of regulation valves in new and existing buildings allows for proper hydraulic balance of the heating system and in this way it may increase the energy efficiency of heating installation. Unfortunately, to the best of authors’ knowledge, there are no long-term field studies that present the level of energy savings achieved by means of commonly used valves in engineering practice, such as thermostatic radiator valves (TRVs), under risers differential pressure control valves (DPCVs), pressure independent balancing radiator valves (PIBRVs), as well as a combination of them. This article presents the results of field research conducted during 6 heating seasons in 16 multifamily buildings assigned to four groups, depending on the type of heating system modernization. The buildings in the first group had existing on-off valves located near the radiator that were replaced with TRVs, and hydraulic balancing of the heating system was performed by means of a pre-set. The second group of buildings was characterized by the installation of DPCVs under the risers of heating installation which was already equipped with TRVs; the third group encompasses the buildings with simultaneous installation of TRVs and DPCVs. The final group consisted of buildings in which the existing TRVs were replaced by pressure independent balancing radiator valves. The energy savings were calculated based on average heat consumption before and after modernization and ranged between 14.6% and 23.8%, depending on the type of the installed valves or their combination. The calculated payback time for the analyzed modernization actions was in the range between 1.4 and 4.9 heating seasons.

Abstract Nowadays, modern heat supply technologies are preferred by the decentralized municipal sector because they considerably reduce heat transfer losses. One such solution is a heating system using residential thermal stations (RTS). The advantages of a heating system with RTS, as compared with hot water storage vessels, include stabilizing heat costs, saving energy and a decrease in heat transfer losses. This paper presents the results of an experiment investigating heat consumption in a residential building using RTS. The building, located in Lublin, Poland, was supplied by the local district heating network. The energy consumption was monitored from April 2007 to April 2009. The efficiency of this system was 71.4% during the period when heat was required (winter) and 61.5% during the summer; an annual average efficiency of 67.1%. The energy consumption of the space heating system varied from 0.03 to 0.53 GJ m−2 of the flat's surface area, with the average value being 0.22 GJ m−2. The influences of the location of the flat within the building and the surface area of the flat on the quantity of heat required for space heating were analysed. Specific attention was paid to the occurrence of local heat flows between flats.

Abstract The education of energy users is one of many possibilities to reduce the energy consumption in existing multifamily buildings. Unfortunately, to the best authors’ knowledge, there is no long term experimental evaluation of energy savings, which may be achieved in flats where heat cost allocators were installed. This article presents the results of experimental research conducted during 17 heating seasons (from 1997/1998 to 2013/2014) in a multifamily building located in Poland. The heat cost allocators were installed in the right part of the building (part R) in 1996 and in the left part of the building of the same size (part L) in 2011. In the summer 2005, thermal renovation of external walls of the analysed building was made. The energy consumption in part R of the building was on average 26.6% and 30.5% lower than in part L for the period before and after thermal renovation of external walls of the building, respectively. After the installation of the heat cost allocators in part L of the building, the amount of heat used for heating was also analysed. The comparison of saved energy to the cost of installing, reading, and maintaining the heat cost allocators was made.