Carbon neutrality in municipalities can be achieved by combining individual heating and district heating solutions involving the use of renewable energy sources. Each approach has advantages and disadvantages, but the best solution depends on the specific circumstances of each municipality. As an environmentally friendly and efficient energy use, a decentralised heat supply contributes to achieving energy conservation and emissions reduction goals. Decentralised energy use, such as solar collectors with thermal energy storage or biomass as a resource, reduces dependence on centralised heat generation and transmission. The appropriate infrastructure for connection to district heating networks has not yet been built. On the other hand, it is easier to make investments to construct proper infrastructure in the case of large-scale centralised heat supplies. Moreover, a centralised heat supply with renewable energy sources can provide more inhabitants with renewable heat energy. Within the framework of the study, the possibilities of using renewable energy sources in one of the municipalities of Latvia—the Carnikava parish of Ādaži Municipality—are analysed. The study examines two scenario complexes including individual heating solutions in buildings or district heating solutions with a centralised approach. The study evaluates several alternatives to increase the share of RES (solar collectors, biomass, heat pumps, etc.) in the centralised heat supply. To evaluate individual RES solutions in various municipal buildings, this study evaluates alternatives with different technical solutions that increase the use of RES in heat supply.

As renewable energy demand grows, different sectors (especially energy and household) face increasing fuel shortages. Increasing interest in alternative biomass for heat production also increases the need to develop appropriate combustion technologies. This paper investigates studies carried out in the context of renewable energy. The main objectives of the article are to identify the trends between alternative biomass types and combustion processes and to find binding keywords between the topics mentioned. Two bibliometric methods – performance analysis and science mapping analysis – are applied to analyse scientific literature related to the specific application from the Scopus database. Performance analysis results show that the number of publications and citations on using alternative biomass in energy is increasing annually. The most significant number of publications in terms of biomass types are municipal solid waste and algae, while in terms of combustion technologies, it is about direct combustion and gasification. According to the results of scientific mapping analysis, algae has a strong link to climate change and sustainability issues.

Nowadays, energy systems are continuously impacted by external and internal conditions. The worldwide events of recent years have led to the need to consider not only the requirements for moving towards climate neutrality but also the security and independence of energy supply when creating new or transforming existing energy systems. The aim of this study was to answer the question of whether there is a possibility of transforming the energy supply process by promoting increased energy security and independence while not reducing energy demand, as well as creating high economic and environmental indicators. The research focuses on developing alternative scenarios for further decision-making studies by introducing modern energy technologies. Scenarios are analysed using the complex method developed, which includes three main steps: assessing the current situation, identifying available technologies, and assessing alternatives. The results suggest that Stirling’s technology can provide 100% energy independence for individual energy consumers. At the same time, thanks to the combination of Stirling technology and solar technologies, there is an opportunity to reduce emissions and energy production costs, but capital investment is increasing.

Flue-gas condenser is used for cleaning the flue-gases in the energy sector. In Latvia, fuel consumption in the household sector is high, so it is planned to introduce this technology in this sector. In the research process of flue-gas condenser, the focus is on reactor testing, rather than on the work of the sedimentation tank – part of the system intended for purification of water from captured particulate matter. In order to ensure good sedimentation process efficiency, it is necessary to know which parameters the process depends on. This study mainly describes the parameters affecting the sedimentation process – dependent indicators and the methods for determining them. The main conclusion is that both methods can be used during the research.

This work is a continuation of the article "Methods for Determining the Performance and Efficiency Parameters of the Flue-gas Condenser Sedimentation Tank". During the experimental determination of Particulate Matter (PM) physical parameters, a described methodology was used. The results obtained affected the choice of water purification technology. Sedimentation technology was selected but provided that a filter element should be present in the installation. The article describes the types of industrial sedimentation tanks used more often. In condition that the system should be compact, while at the same time the purification efficiency rate should be high, the new suitable design of the water treatment system was developed.