Combined Heat and Power (CHP) or Cogeneration
A combined heat and power plant uses a fuel fired engine to generate power while simultaneously capturing the excess heat produced for heating purposes. Using the waste heat and creating electricity on-site makes the system more efficient than a traditional one fuelled by carbon intensive electricity.
These systems can require a lot of maintenance and are best suited for buildings which have a constant need for heat so that the excess heat is not wasted.
Furthermore, depending on the carbon emissions factor of your electricity grid, these systems can actually increase the carbon footprint, especially over time, as the electricity grid gets cleaner. Learn more about cogeneration.
District Energy
A district energy system is one that centralizes heating and cooling energy generation and distributes this energy to a larger area including many buildings, such as a neighbourhood. District energy systems traditionally use high-temperature boiler plants that distribute high-temperature water through insulated steel piping; this heat is then used directly at each building.
More recently, lower temperature systems are being used which allow much easier tie-in of renewable energy generation and eliminate the need for boiler plants.
An example is the ambient temperature district energy systems which extract low-grade heat from sewers or geo-exchange systems and deliver ambient temperature water to each building which can be used for heating or cooling. These systems are much more efficient and can share energy on a district scale.