Denmark is ranked among the top countries in the world according to the World Energy Council (WEC) energy trilemma criteria: energy security, energy equity, and sustainability. The small Scandinavian country is known for its wind power technologies and large-scale integration of wind power into the grid. Compared to wind power, combined heat and power (CHP) plants, district heating (DH) technologies, and the underground network of pipes throughout the country has lived a relatively quiet life. However, these collective heat infrastructure networks and CHPs are fundamental for the energy efficiency of the Danish energy system and the top WEC ranking in the country. COMBINED HEAT & POWER – heat infrastructure planning in Denmark
100 years ago, daily waste was collected and trans- ported by horse carriages to the city dump.
By Katinka Johansen, Ph.D., Energy Transitions and Social Psychology, Danish Technological Institute, DTU
The First CHP Plants In the 1880s, Hamburg solved a growing waste management problem by constructing a waste incineration plant that gen- erated heat for heating purposes. The city of Hamburg had suffered a cholera outbreak in 1882. Adjacent towns prohibited the import of waste from the city to protect themselves from this epidemic. As a result, citizens of Hamburg turned to burn household waste in the streets. In neighboring Denmark, household waste management also became a challenge as populations increased due to industrialization and urbanization. In Frederiksberg, adja- cent to Copenhagen, the emergent industrial sector attract- ed workers from afar. Waste piled up on street corners and in the small open spaces, and the 75,000 inhabitants knew
World War II — again — led to an energy crisis. At some CHP plants, heat-only boilers were constructed as heat supply back- up. After the war, the existing district heating networks were expanded to integrate this additional heat production capaci- ty. Coal was still the prioritized fuel.
the health risks associated with these mountains of waste. In Copenhagen municipality, the population was also grow- ing, and therefore land for landfills was expensive. Moreover, landfills close to cities were also associated with the risk of epidemics. Inspired by the example from Hamburg, Frederiksberg Munic- ipality set out to solve this problem and constructed the first primitive waste incineration plant in Denmark. Inaugurated in 1903, this waste incineration plant produced heat and electric- ity. Horse-drawn carriages transported the household waste to the waste incineration plant. Throughout the country, this first primitive CHP plant proved inspirational. Fuel import dependency and experiences of en- ergy resource scarcity during World War I called for energy effi-
ciency initiatives and motivated the integration of CHP plants into the energy system. Power plants throughout Denmark were due for renovation in the 1920s, and many municipalities converted their power plants to CHP plants that provided heat for dwellings or institutions close by.
District Heating: Energy Efficiency, Energy Flexibility, and Fuel Diversification The fundamental idea of district heating is to harvest otherwise wasted heat from power production in CHP plants and other industries. District heating systems enable the integration of various energy sources into the energy system. For example, renewables such as wind, solar, and biomass supply energy and relatively low-quality fuels such as household waste. District heating systems enable short-term (daily) and long-term (seasonal) thermal energy storage. The technical solutions, combinations, and fuel usage in individual district heating systems can be adapted to specific local contexts and the locally available fuel resources. These characteristics may improve energy systems efficiency overall and facilitate the energy flexibility necessary to integrate more intermittent renewable energy resources into the energy system.
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The Global Energy Crisis and National-Scale Collective Heat Infrastructure Planning Policymakers and the Danish public warmly welcomed the newly discovered oil and gas reserves within the national sea territories. The Danish government now set out to create a long-term strategy for ensuring the stability of energy supplies well into the future. These strategies were outlined in the Dan- ish Energy Plan 1976, with the key policy priorities captured by
The 1950s and 1960s: The Welfare State and Population Growth Growing populations and urbanization led to the growth of the suburbs. Many of these new suburbs were planned with district heating from the outset—municipalities, and some- times jointly, invested in large, centralized CHP plants. For the end-users, district heating provided affordable, accessible, and convenient heat supplies that required little service and main- tenance.
the headlines: energy independence, fuel diversification, and energy efficiency. Energy infrastructure planning initiatives laid out in this plan focused on using waste heat from industry, in- tegrating CHP, and the harvest of locally available renewable energy resources.
In the 1960s, preliminary explorations for oil and gas had taken place in the Danish part of the North Sea, and the private entre- preneur A.P. Møller-Maersk was awarded the concessional rights to these fossil-fuel reserves. Oil was first extracted from the oil platformDanfield in 1972. That same year, the commercial trans- mission company for natural gas (DONG, now known as Ørsted) was established with the Danish state as the only shareholder.
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