Assessment of the Feasibility of Implementing Shower Heat Exchangers in Residential Buildings Based on Users’ Energy Saving Preferences

Horizontal Shower Heat Exchanger as an Effective Domestic Hot Water Heating Alternative

Wastewater has significant potential as a source of clean energy. This energy can be used both within external sewer networks and on the scale of individual residential buildings, and the use of shower heat exchangers appears to be the most reasonable solution. However, in the case of Poland, the problem is still the unwillingness of society to use this type of solution, caused mainly by the lack of space for the installation of vertical drain water heat recovery (DWHR) units and the low efficiency of horizontal units. In response to this issue, the efficiency of a new compact shower heat exchanger designed to be mounted below the shower tray, as well as its linear counterpart, was investigated under various operating conditions. In addition, the financial efficiency of using the compact DWHR unit with average water consumption for showering was evaluated. For this purpose, discount methods were used to estimate the financial efficiency of investments. The study showed that the compact shower heat exchanger has higher efficiency than its linear counterpart. Depending on the temperature of cold water and the flow rate of both media through the heat exchanger, it achieves efficiencies ranging from 22.43% to 31.82%, while the efficiency of the linear DWHR unit did not exceed 23.03% in the study. The financial analysis showed that its use is particularly beneficial when the building uses an electric hot water heater. The investment’s sensitivity to changes in the independent variables is small in this case, even with low water consumption per shower. The only exceptions are investment outlays. Therefore, the compact DWHR unit is a clean energy device, which in many cases is financially viable.

Introducing a Calculator for the Environmental and Financial Potential of Drain Water Heat Recovery in Commercial Kitchens

Food service providers like restaurants, cafes, or canteens are of economic importance worldwide, but also contribute to environmental impacts through water and energy consumption. Drain water heat recovery from commercial kitchens, using a heat exchanger, has shown large potential to decarbonise hot water use across food services, but is rarely deployed. This work translates previous findings on the technical feasibility and heat recovery potential for commercial kitchens into a publicly available calculator. It facilitates decision-making towards recovery and reuse of the freely available heat in kitchen drains by estimating both financial costs and payback time, as well as environmental burdens associated with the installation and environmental savings from avoided energy consumption. Environmental burdens and savings include, but are not limited to, carbon emissions. Further, the tool highlights key aspects of the technical implementation to understand installation requirements. The tool is freely available and could contribute to the uptake of heat recovery in the food service sector, ideally in conjunction with policy support through financial incentives or subsidies.

Users’ Sensations in the Context of Energy Efficiency Maintenance in Public Utility Buildings

Research towards understanding the relationship between maintaining thermal comfort and energy efficiency in the public utility buildings was undertaken among 323 1st year students during class hours. Questionnaires surveys and measurements of indoor conditions were performed. The article identified students’ sensations and perceptions concerning indoor conditions. Temperature, relative humidity, air velocity and CO2 concentration measured to assess room conditions showed that the auditorium had almost comfortable conditions according to the literature guidelines. The indices used to assess students’ perceptions were: Thermal Sensation Vote (TSV), Thermal Preference Vote (TPV), Air Freshness Sensation Vote (AfSV), Air Movement Preference Vote (AmPV), and Relative Humidity Preference Vote (RHPV). The interpretation of these indicators showed that while the students’ requests for temperature changes and increased air movement are adequate for the air conditions in the room, the evaluation of stuffiness and requests for changes in humidity levels are surprising. Striving uncritically to meet the desired room parameters, according to the users votes, can lead to deterioration of the air and not only the increase in energy consumption but even waste it. Better understanding of users’ preferences and behaviour and further application of this knowledge indirectly aim at increasing energy efficiency in buildings.

Peak Power of Heat Source for Domestic Hot Water Preparation (DHW) for Residential Estate in Poland as a Representative Case Study for the Climate of Central Europe

Due to the energy transformation in buildings, the proportions of energy consumption for heating, ventilation and domestic hot water preparation (DHW) have changed. The latter component can now play a significant role, not only in the context of the annual heat demand, but also in the context of selecting the peak power of the heat source. In this paper, the comparison of chosen methods for its calculation is presented. The results show that for contemporary residential buildings, the peak power for DHW preparation can achieve the same or higher value as the peak power for heating and ventilation. For this reason, nowadays the correct selection of the peak power of a heat source for DHW purposes becomes more important, especially if it uses renewable energy sources, because it affects its size and so the investment cost and economic efficiency. It is also indicated that in modern buildings, mainly accumulative systems with hot water storage tanks should be taken into account because they are less sensitive to design errors (wrongly selected peak value in the context of the uncertainty of hot water consumption) and because they result in acceptable value of peak power for DHW in comparison to heating and ventilation.