Energy efficiency is extremely significant for industrial processes and technologies. Rising energy prices, depleting fossil fuels, as well as tightening regulations that impose the need to reduce GHG emissions incentivize companies to look for energy-efficient solutions. This also applies to wastewater treatment plants, which, on the one hand, are consumers of very large amounts of energy, and on the other hand, have significant potential to retrieve waste energy in the form of heat accumulated in wastewater. The authors of this publication have recognized the benefits of managing this heat. However, they have also pointed out several problems and difficulties associated with this process. By means of measured data, this publication provides a comprehensive analysis of the heat that can be recovered from wastewater treatment plants. As a result of the analyses, the locations of sites for collecting heat from wastewater have been determined, and potential technologies for this purpose have been identified. Moreover, the impact of the proposed heat recovery technology on the process of biological wastewater treatment has also been analyzed. As a result of the research, the authors developed generalized guidelines for selecting an optimal heat recovery site and the technological system designed for this purpose.

In the EU countries, almost 50% of the produced energy is used in residential buildings. More than 25% of this energy is used to produce domestic hot water, of which almost 80% is used to heat water in domestic hot water circulation systems. This is due to high expectations on the part of residents based on their comfort, in particular regarding the supply of heat for heating and domestic hot water. In the course of their long-term research conducted on real systems, the authors confirmed that the operation of domestic hot water distribution systems causes significant costs, mainly due to heat losses. Therefore, typical variants of energy optimization of such systems were analyzed. Tests have shown that selected solutions, such as the use of control automation, are not sufficient, and recommended additional thermal insulation may not be applicable due to technical reasons. With an aim of finding a solution to the problem, the publication analyzes operational data from an existing heat source and domestic hot water circulation system in a residential building. On the basis of these analyses, a solution was proposed to reduce energy consumption within the installation by means of its hydraulic optimization. The reduction of heat losses in domestic hot water installation by means of a method presented by the authors is estimated at approximately 20%.

About 55% of over 14 million Polish households live in multi-family buildings. Cooperative or housing association buildings have a large share in this group. The heat is supplied from the district heating network or from local sources. With respect to facilities fed from gas boiler rooms, the...

The temporal mismatch between photovoltaic (PV) electricity generation and on-site demand constitutes a systemic barrier to effective renewable energy utilisation in large public facilities, resulting in mandatory curtailment and measurable economic losses. This study presents the design, implementation, and techno-economic assessment of an integrated Power-to-Heat (P2H) system deployed at a Provincial Sports and Recreation Centre (WOSiR Drzonków, western Poland) with 283.7 kWp of installed PV capacity. The proposed solution converts surplus PV electricity into low-temperature heat via an electrode boiler coupled with an existing thermal energy storage (TES) system (1.5–2 m³ DHW buffer), eliminating the need for electrochemical battery storage. System operation is governed by an automation algorithm triggered by a digital signal from PV inverters, redirecting overproduction exclusively to the heating subsystem. Balance modelling based on 5-minute-resolution inverter data (2018–2023) demonstrated that annual PV surplus (59.3 MWh) virtually fully covers annual DHW heat demand under the 3 m³/d scenario (57 MWh), achieving a self-consumption ratio of approximately 100%. Dynamic thermal analysis confirmed that a 2 m³ buffer sufficiently absorbs peak instantaneous PV output (43 kWh/h), elevating water temperature by 20 K within 1.1 h. Techno-economic evaluation across three scenarios yielded annual savings of 22,100–47,700 PLN, with TES unit costs (10–30 €/kWh) an order of magnitude lower than lithium-ion battery equivalents (200–400 €/kWh). The results demonstrate that P2H sector coupling, leveraging existing gas and thermal infrastructure, constitutes a replicable, cost-effective decarbonisation pathway for public facilities with continuous low-temperature heat demand, offering a scalable model for energy transition under net-billing frameworks.

The observed climate change and the increased requirements for the share of renewable energy sources in the energy balance of various facilities make it extremely important to develop and implement technologies that increase the share of RES, cooperating with conventional technological systems for producing heat and electricity. One of the most widely used technologies in Poland and worldwide is photovoltaic cells. However, in this sector there is a significant discrepancy in energy production and consumption, which constitutes a problem diagnosed by the authors of this publication. The traditional and most common solution to this predicament is using energy batteries. Yet, they are not widely used due to their excessively high cost, among other factors. Therefore, the authors of this publication have adopted a completely different approach to solving the above problem. Their research proposes an innovative strategy involving a technological system for converting electricity to heat and an advanced control automation system that supports the operation of traditional gas boilers. The developed technology has been implemented in a large Provincial Sports and Recreation Centre. The publication presents the developed innovative technological system, as well as reveals the results of preliminary technical and economic analyses.