A geoexchange system transports heat from where it's generated to where it's needed by capturing heat from the earth, a body of water or waste heat sources like refrigeration (e.g. ice rinks and grocery stores), waste water effluent and sewers. This heat is recovered by placing heat exchangers around the various heat sources to extract the heat, which is then transported to the buildings that require the energy.
Biogas and biomass
Alternative energy solutions powered by biogas or biomass can produce both heat and power. A biogas power plant gathers methane from biological material (e.g. landfills and animal manure from farms), whereas a biomass power plant generates energy from wood and wood by-products (e.g. residue from forestry and sawmills). The simplest method of converting biogas or biomass to energy involves burning biogas or wood products in a boiler to produce steam, which is then used to turn a turbine. This turbine is connected to a generator that can produce heat and electricity.
Sewer and landfill gas
Sewer and landfill gas are generated by the decomposition of raw material, which produces methane that can be combusted for thermal energy on-site and then used to generate electricity. It can also be injected into a pipeline for combustion off-site.
As a highly available source of energy, solar power can be used as an alternative energy source in district energy systems. The solar energy that is generated can be used to produce hot water and electricity.