In the United States, 360 sites currently use microturbines for cogeneration, which represents more than 8% of the total number of cogeneration sites and 92 MW of total capacity. Small cogeneration with district heating systems (DH) also exist mainly between state-owned buildings, such as hospitals, military, universities and offices.
For commercial or large district heating, connecting many customers with varying heat demands to a central plant for continuous operation instead of several individual plants operating sporadically makes economic sense. In addition, the cogeneration of biomass and waste is the most feasible on a large scale.
The economics and efficiency of cogeneration for district heating depend on geographic location, as district grid costs are a considerable part of the capital investment, but much-DH networks maintained should last around 100 years.
Commercial viability depends on network density
Proximity plays a big role in success. In Helsinki, Finland, cogeneration with district heating supplies around 95% of total heat demand, covering around 1,230 km of underground heating networks and over 10,000 connected buildings, serving over 600,000 residents.
District heating systems are capital intensive and could be affected by access to roads and public land. A rule of thumb for the commercial viability of cogeneration is that the heat / load density should be greater than two MWh per meter of the planned network length. In low heat density suburbs, for example, network investment costs are difficult to overcome.
Cogeneration as a powerful ingredient for urban energy transformation
For a more sustainable and renewable heating and cooling sector transition, cogeneration, with a district heating system powered by renewable energies, offers an economical path to transformation. A long-term integrated energy plan for heating and cooling is needed to coordinate the deployment of renewable energy solutions with measures to increase energy efficiency and develop the necessary infrastructure, while simultaneously avoiding conflicts between tracks and stranding assets.
In Finland, around 75% of urban heat production is based on cogeneration, and 33% of electricity is obtained in cogeneration, ranking Finland as the country with the largest cogenerated electricity market share in the world, with a district heating network of approximately 15,000 km.
Cities, towns and regions should focus on cross-sector planning to integrate the heating and cooling transition into sector plans, including energy and industry. The local energy plan for heating and cooling should be based on specific needs; macroeconomic conditions; availability of resources; the infrastructure already in place; and the level of development, accessibility and cost of technologies.