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Solar collectors are devices that enable the use of solar radiation, e.g., for hot water preparation or space heating. They are playing an increasingly important role in Europe and around the world, mainly due to the easy availability of the sun, as an energy source. The advisability of their use depends on a number of factors, of which climatic conditions are an extremely important one. This paper presents the results of energy simulations of a solar collector-based domestic hot water system for the capitals of five selected Central and Eastern European Countries (CEEC): Riga, Warsaw, Prague, Bratislava, and Zagreb. Using TRNSYS software, a theoretical model of the system was developed and dynamic simulations were carried out for the entire year. The amount of useful energy generated by the flat-plate collectors, their efficiency, as well as the auxiliary energy requirements and the amount of energy needed to meet the load were estimated and compared. The extent to which changing the area of solar collector affects the operation and efficiency of the system for different locations was also analysed. The results showed that in terms of efficiency, the use of solar collectors is most favourable in placed southernmost Croatia and in Slovakia, where it was also achieved the lowest annual auxiliary energy demand. The least favourable location turned out to be Riga. It is also worth noting that regardless of location, the area of solar collector has a significant impact on the efficiency of the entire system.

Heat pumps are increasingly popular in individual buildings and could help to meet expectations of ambitious energy-environmental European goals until 2050. This paper presents the results of energy simulations conducted in TRNSYS for a single-family building depending on its location in selected European cities. For each city, air source heat pump (ASHP) was considered as an energy source for heating and cooling the building, and then an economic analysis was carried out including investment costs of air source heat pump and a comparison of operating costs of ASHP with other alternatives (i.e. gas boiler, oil boiler, or air conditioners). The results of the simulations showed that with the current energy prices the use of air source heat pumps is the most beneficial in temperate warm transitional climate (Krakow). It was also indicated that the implementation of special tariffs (reduced prices) for electricity that supplies renewable energy devices would make heat pumps unmatched as a source of heating and cooling in the residential sector.

The publication presents a design solution for circular multi-pipe thermal insulation and an example of an existing heating installation consisting of six individual heating pipes in the building of the Bialystok University of Technology. In the paper, the arrangement of six heating system pipes in circular thermal insulation was designed in such a way that one heating pipe is centrally located in the circular thermal insulation, the other five heating pipes are located at the vertices of a regular pentagon inside the circular thermal insulation. Heat loss calculations were made using the Boundary Elements Method (BEM) with the actual boundary conditions in the room where the existing heating installation is located. Additionally, the ecological effect was determined in the form of reduction of pollutants emitted into the atmosphere resulting from heat losses for the developed multi-pipe thermal insulation. The calculation results showed a significant reduction in heat losses as a result of the use of multi-pipe thermal insulation in relation to the existing single heating installation. The use of multi-pipe insulation undoubtedly follows the trend of energy-saving heat transport and is an alternative to the commonly used single pipes.

Becoming the world’s first climate-neutral continent by 2050 is currently the most ambitious European goal. Heat pumps are the example of the key technology, which could help to achieve the aim by heating, cooling and domestic hot water (DHW) preparation in an ecological and energy-efficient way. This article characterized a heat pump market in Europe between 2009 and 2020 with a special regard to France, Spain, Poland and Lithuania, for which a more detailed study was presented. The analysis was performed primarily on the grounds of statistics data provided by the European Heat Pump Association (EHPA), which determined the number of heat pumps sold based on standard questionnaires from national heat pump associations, statistical offices and research institutes. The highest number of heat pump sold in analysed period of time was recorded in France, Italy, Sweden, Norway, Germany and Spain. Poland was in the middle of the list, while Lithuania was one of the last countries. Considering the number of heat pumps sold per 1000 households, Norway was the clear leader, followed by Estonia, Finland, Sweden and Denmark. Lithuania was placed 12th, while Poland was only 18th. In terms of the type of lower and upper heat source, air-to-water and air-to-air heat pumps were the most popular choices, while ground source heat pumps were the least popular. The development of the heat pump market has been influenced by social, environmental, economic and technological factors.