cogen

Cogen, short for cogeneration, refers to the simultaneous production of electricity and useful heat from a single energy source. By utilizing the heat that would otherwise be wasted in electricity generation, cogeneration achieves higher overall energy efficiency than conventional separate generation of electricity and heat.

Most cogeneration systems use a prime mover such as a natural-gas-fired internal combustion engine, a gas turbine, or a fuel cell to drive an electrical generator. The exhaust or hot fluids from the prime mover are routed to a heat recovery unit, where the heat is captured to produce steam, hot water, or space heating. This configuration can be scaled from micro-CHP units for individual buildings to large industrial CHP plants feeding district heating networks.

System efficiencies of 70-90% are possible depending on design and heat demand; this compares with typical efficiencies around 35-50% for conventional separate production. Benefits include lower fuel use per unit of useful energy, reduced emissions, on-site reliability, and peak-load reduction for the electricity grid. The environmental impact depends on the fuel and the heat demand profile; using waste fuels or renewables can further improve sustainability. Heat-led or electric-led operating strategies optimize the match between heat demand and electricity generation.

CHP is common in industrial facilities, large commercial buildings, hospitals, and district energy systems. Micro-CHP units serve single buildings or small campuses. Tri-generation adds cooling through absorption chillers using the recovered heat. Biomass, coal, or oil-fired CHP plants are also used where appropriate, though modern policies often favor low-carbon fuels.

Economic viability hinges on capital cost, fuel price, incentives, and the value of on-site electricity and heat. Policy frameworks, tariffs, and grid access rules influence deployment. Life-cycle emissions are typically lower than separate generation when heat is effectively utilized.