What is Cogeneration (Combined Heat and Power)?

Conceptual Schematic of a Gas Turbine Cogeneration System
Conceptual Schematic of a Gas Turbine Cogeneration System

Cogeneration, or Combined Heat and Power (CHP), is generally defined as the simultaneous generation of electricity and useful thermal energy (usually in the form of steam, hot water or chilled water) from a single source of primary energy.

The fuel is combusted in the prime mover which produces electricity by driving a generator and useful thermal energy is recovered from the high-temperature exhaust gas using some form of a heat recovery device. The preferred fuel for a modern cogeneration system is natural gas which is the cleanest form of fossil fuel.

The prime mover usually consists of internal combustion engines such as gas engine generators or combustion turbines such as gas turbine generators.

The heat recovery device can be a heat recovery steam generator (waste heat boiler) for steam generation, or it can also be a heat recovery hot water generator for hot water production.

Cogeneration Efficiency 75%
Cogeneration Efficiency 75%

A Cogeneration systems’ ability to recover waste heat significantly reduces the primary fuel consumption for each unit of useful energy generated. Consequently, Cogeneration plants have high overall fuel efficiency, typically 75% or higher.

When compared to the conventional system of separate generation of electricity and thermal energy, cogeneration systems offer numerous benefits, including higher primary fuel efficiency (up to 50% higher efficiency), lower fuel consumption, lower operational costs, reduced greenhouse gas emissions, reduced emission of pollutants such as NOx, CO, and lower carbon footprint.