Combined Heat and Power Plant

A cogeneration power facility that maximizes energy efficiency by producing electricity and heat simultaneously.

Combined Heat and Power Plant

Overview

A combined heat and power plant (CHP; Korean: 열병합발전소, 熱竝合發電所) is a power generation facility that recovers waste heat discarded when fuel is combusted to produce electricity and supplies it together as heating, hot water, and process steam. Whereas conventional thermal power plants typically remain at an electricity generation efficiency of 35–45%, CHP achieves an overall efficiency of 70–90% when electricity and heat are combined, resulting in very high energy utilization efficiency. It is also called cogeneration and has become core infrastructure for city-level district heating (district energy) and process heat supply in industrial complexes.

Key Details

Operating Principle and Configuration

A CHP plant largely consists of a prime mover (gas turbine, steam turbine, internal combustion engine, fuel cell, etc.), waste heat recovery equipment, heat exchangers, thermal storage tanks, and heat transmission pipeline networks. Fuel combustion drives the prime mover to run a generator and produce electricity, while high-temperature exhaust gas or turbine steam discharged from the prime mover is recovered through a heat recovery steam generator (HRSG) and heat exchangers to produce hot water at 90–120°C, which is sent to the district heating pipeline network. To respond to load fluctuations, a method of storing heat in thermal storage tanks and releasing it during peak hours is widely used.

Main Types

Gas turbine combined cycle type: A method that generates power with a gas turbine burning natural gas and then uses the exhaust heat to produce steam that additionally drives a steam turbine. This is the mainstream type for large-capacity district heating CHP.
Extraction-condensing steam turbine type: A method that extracts part of boiler steam for power generation and part as heat, widely used in industrial complexes.
Internal combustion engine type: Small-scale, distributed CHP using reciprocating engines, suitable for buildings, hospitals, and factories.
Fuel cell type: A method that recovers waste heat from the fuel cell power generation process, with high efficiency and low emissions.
Trigeneration (CCHP): A method that adds cooling to heat and power, using absorption chillers to meet summer cooling demand.

Economic and Environmental Value

Because CHP obtains electricity and heat simultaneously from one unit of fuel, it can reduce fuel use and greenhouse gas emissions by at least 20–30% compared with producing heating heat with a separate boiler. In addition, because it is located near urban centers, transmission losses are low, and it has a significant distributed generation effect that reduces the burden of transmission and distribution facility investment for large power plants. In Korea, under the District Energy Business Act, CHP plants are registered as district heating operators and are subject to regulation of heat tariffs, with the Korea District Heating Corporation and private power generation companies active as major operators.

Major Facilities and Safety Management

Because high-pressure steam and high-temperature water are handled, regular inspection of boilers, turbines, and piping and management of safety valves are essential, and heat transmission pipe leak monitoring and remote control systems are operated. Recently, cases of introducing IoT sensors and digital twins to detect equipment abnormalities early and optimize operation based on heat demand forecasting are increasing.

Latest Trends

In 2024–2025, the role of CHP is being reorganized as carbon neutrality policy and energy security issues intersect. First, conversion of aging coal CHP facilities to LNG or biomass co-firing is expanding, and demonstrations of hydrogen and ammonia co-firing are underway. Second, attention is being drawn to waste heat network projects that recover waste heat from large-scale continuous heat demand sites such as data centers and semiconductor factories and link it to nearby district heating networks. Third, sector coupling technologies that flexibly convert between electricity and heat by combining large heat pumps and thermal storage tanks are being introduced, contributing to mitigating renewable energy variability in the power system. Fourth, AI-based demand forecasting and optimal operation algorithms are being applied to CHP facilities to further raise efficiency, and measures to use small modular reactors (SMRs) as district heating heat sources are also being studied. In Korea, pressure to raise heat tariffs, investment in replacing aging pipes, and policies to expand district energy supply areas have emerged as major issues.