Nowadays energy crises are characterized by their intensity, i.e. for a short period of time they can cause significant consequences on the economy and overall living. The impacts of energy crisis are mainly reflected indirectly through misbalance in electrical energy production, which is main component and foundation for all socio-economic processes. In addition, the current coincidence of the energy crisis (high price of natural gas) with the heating season reveals and emphasizes the importance of the heating energy. The aim of this paper is to analyse the role, advantages and disadvantages of existing district heating (DH) systems with cogeneration power plants CHP), as an important link in the country power system, especially in times of energy crises. In the analyses as a reference system is considered the DH system in Skopje, Republic of North Macedonia. Assessment for the influence of the fluctuation in heat consumption in the DH system on the power system is performed by using simulation software for energy modelling of the district heating system in Skopje, linked with the data for yearly (hourly basis) electricity consumption. Additional economic assessment is conducted to determine cost competitiveness of DH system with other individual heating technologies available in urban areas. Results reveal that district heating systems with cogeneration power plants in densely populated urban areas are cost optimal heating system and extremely important link in country energy chain, providing energy stability, along with potential consequences in case of longer (un) foreseen interruptions in operation.

The world's economic growth has lea to increased energy needs that have to be satisfied with higher electricity production from both conventional and renewable energy sources. Due to the reduced fossil fuel stocks as well as environmental pollution caused by conventional power plants priority is given to the expansion of renewable energy sources. Motivated by the need to study the competitiveness, eco-friendliness and reliability of renewable energy, research was conducted on the effect that different energy types have on the environment, population, and economy. The aim of this paper is to analyze the ethical dilemmas of renewable energy as constraints for increasing the renewable energy share in the generation of electricity and replacement of fossil fuels, considering the production process intensity, noble materials depletion, and climate change caused. The extensive analysis showed that although renewable energy is in principle a clean and inexhaustible energy source, it can cause burdens on nature and society.

The decrease in conventional energy resources, environmental pollution issues and climate change are the leading factors inducing the increase of energy efficiency criteria. Trends to improve energy efficiency are mainly aimed at the construction sector as one of the leading sectors in energy consumption. In the paper the performance of the decentralized solar assisted heating systems (SAHS) for climatic conditions in Macedonia was analysed in order to assess its possibility to be integrated as part of the district heating system. The analysis is based on a holistic approach, in which the performance of the SAHS is generally functionally dependent on four factors: (1) the characteristics of each component, (2) the system structure and mutual interactions of the components, (3) the management method and (4) specific energy consumption for heating of the building. The specific analysis is directed toward the assessment of the solar fraction of the SAHS as a function of the building energy performance and system heating temperature range. The numerical modelling of the processes occurring in systems was performed with the dynamic simulation software TRNSYS. Both dynamic models of the solar bivalent system and reference building were developed. The dynamic model contributes to the flexibility of conducting parametric analysis. The obtained results from the parametric analysis were condensed in a general table upon which the analysis of system performance was performed.