Supplying cities with energy through collective heating and cooling

The challenge
Today, approximately 50 percent of the world’s population is living in urban areas and by 2050, this number is projected to be almost 70 percent. This global urbanisation increases the population density and consequently puts pressure on future cities’ supply of resources, which includes  heating and cooling of residential and commercial buildings.

The future
Multiple benefits are to be obtained by transforming the cities’ energy supply from individual systems to a collective district heating and cooling system. These include an efficient supply of stable and reliable heating with low heat loss, cost-effective cooling of large residential and office buildings as well as the possibility of integrating multiple and flexible clean energy sources, which is a way towards creating fossil free cities.

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With people moving closer together in smaller areas, the distance between buildings and areas is also shrinking. This is evident in the increasing amount of the so-called ‘mega-cities’ with +10 million inhabitants. Although urbanisation indeed creates some serious challenges and increases the pressure on resources like water and energy, the high density also entails an opportunity in terms of efficiency and stability. When people are living in areas with high density, individual heating and cooling solutions can be replaced with district and collective energy systems. In these areas, individual city components are placed close together and each apartment, building and district can be connected to a larger energy plant. In this centralised system the operation, management and maintenance is optimised through innovative processes, which allow for a highly efficient energy supply when heated or cooled water is moved around the city through underground pipes.

In both district heating and cooling, the process utilises surplus value from one place and moves this value to areas and buildings with a need for either higher or lower temperatures. As 50 percent of the global annual energy consumption is used for heating and cooling, the potential energy savings of district energy systems are high and important when creating a sustainable and integrated city. District cooling is mainly relevant in cities, where buildings are close – consequently, the distance from the cooling demand is relatively close to a central cooling plant. Even cities situated in cold climates can utilise the potential of district cooling for buildings with higher cooling demands, e.g. office buildings, hotels and hospitals. Compared to traditional air-conditioning modules, district cooling is 5-10 times more energy efficient.

A key advantage of the district energy system in cities is the potential of integrating multiple energy sources in the production of energy, as it is centralised in one plant and not divided into millions of individual heating and cooling systems. The central plant can thus more efficiently adapt and convert its functions to suit the challenges and technological possibilities of the future. This also enables a way to solve another global challenge of cities, which is the intense increase of waste from both households and industry. The waste, which is not recycled, can be used for incineration and consequently serve as a valuable resource in a combined heat and power plant.

Connect with us: Charlotte Gjedde, Project Manager,