Towards Pollution Reductions and Decarbonization of District Heating Systems

Global climate change significantly affects the energy usage of district heating and cooling systems, especially when planning new operations or maintaining existing ones. These systems typically rely on fossil fuels as their energy source and are often located in densely populated areas, leading to a significant negative impact on air quality. The pollutants they emit, such as CO2, SO2, NOX, and dust particles, vary depending on the type of fossil fuel used, with coal being the worst and natural gas representing the least hazardous option. Given the growing emphasis on renewable energy sources like geothermal, solar, and wind power, and the availability of energy-efficient technologies, current research aims to develop new technologies for district heating systems that can reduce their negative environmental impact, lower pollutant emissions, and facilitate the decarbonization of this energy sector. In recent years, the city of Skopje has faced severe environmental issues, particularly during the winter season. Apart from city traffic, the underdeveloped district heating system, which only covers 40% of the city’s heating needs, is a major contributing factor. The remaining heating comes from conventional sources such as wood, wooden residuals, or wooden pellets, significantly worsening air quality and citizens' living standards. Moreover, due to lower economic standards and high costs of heat energy from district heating companies, many users have switched to alternative heating sources like air conditioning, heat pumps, or other environmentally unsuitable energy sources. This paper focuses on addressing the problems and potential solutions for transitioning the district heating system to a more sustainable model. Starting from the now outdated 1st and 2nd generation district heating systems, the primary goal is to facilitate a smooth transition from the widely accepted 3rd generation to the improved 4th generation of district heating systems. The district heating systems in Skopje currently fall between the 2nd and 3rd generation and urgently require transformation towards the fourth generation. While some countries, such as Denmark and the UK, propose moving towards the fifth generation of district systems, it appears that the fourth generation still offers significant advantages over the proposed fifth generation, considering the existing heating systems, economic factors, and expected benefits.