Cogeneration reduces fuel use for a given energy output and eliminates losses when electricity is transmitted and distributed. American power plants that rely on fossil fuels have an average efficiency of 36%. This means that at most power plants in the US, 64% of the energy required to produce electricity is lost in the form of heat that is released into the environment.
Natural gas boilers are commonly used to generate thermal energy and have an efficiency range of 75-85%. Separate heating and electricity from the grid reduce fuel use by around half. CHP systems typically attain total system efficiencies between 65 and 80% by collecting and reusing heat from on-site electrical generation. The efficiency of specific systems is close to 90 percent.
The technology and system design of a CHP unit determines its efficiency. Listed below are the efficiency of the five most popular CHP power sources (also known as “primary movers”):
- Reciprocating engine: 75–80 percent
- Combustion turbine: 65–70 percent
- Steam turbine: 80 percent
- Microturbine: 60–70 percent
- Fuel cell: 55–80 percent
Transmission and Distribution Losses
CHP also helps reduce the environmental impact of generating electricity because none of it is wasted in the form of heat or light as it travels through power lines. The average transmission and distribution losses across the five major electricity grids in the United States range from 5.2% to 5.6%, with a national average of 5.3%. (Source: eGRID). When the grid is already under stress from heavy use and temperatures are high, losses might increase. CHP further reduces fuel use, helps prevent the need for new transmission and distribution infrastructure, and eases grid congestion during times of high energy demand by eliminating losses associated with conventional electricity delivery.
Benefits for The Environment
Emissions of greenhouse gases and other air pollutants are lowered by combined heat and power (CHP) systems because less fuel is burnt per unit of energy produced and distribution losses are eliminated. This means it has the potential as a tool for reducing carbon emissions from power plants.
Comparing a CHP system to conventional electrical and thermal energy production, the environmental benefits are clear. When compared to conventional power plants, these ones utilize less fuel to generate the same amount of energy since they recover and repurpose heat that would otherwise be squandered during the generation of electricity.
Reduced fuel consumption leads to lower emissions of greenhouse gases like carbon dioxide (CO2) and other pollutants like nitrogen oxides (NOx) and sulfur dioxide (SO2).
The following illustration compares the CO2 emissions from conventional energy sources with those from a combined heat and power (CHP) plant that generates 5 MW using natural gas.
Economical Benefits of CHP
As a result of its great efficiency, CHP can significantly cut down on monthly energy bills. CHP systems often attain total system efficiencies of 60–80%, compared to 50% for conventional methods, by capturing waste heat associated with electricity production through waste heat recovery technology (i.e., purchased utility electricity and an on-site boiler). Simply put, they have a lower fuel requirement for the same amount of energy production. They are useful in lowering electrical costs since they often run on natural gas, which is less expensive than purchased electricity. As a result of the CHP’s output, less electricity is needed, which means lower bills.
CHP can help homeowners save money by delaying the need to buy new heating equipment. Connecting a building to a combined heat and power (CHP) system allows for the provision of district heating (steam or hot water) and district cooling services (chilled water) for the provision of space heating, household hot water, and air conditioning. Services like this eliminate the need for costly on-site installation and maintenance while freeing up valuable floor and roof space for more lucrative enterprises.
The revenue streams of businesses can be safeguarded by implementing CHP because of the on-site generation and enhanced reliability it provides in the event of a natural disaster or an interruption in the supply of power from the grid.
Reduced reliance on grid electricity means that facilities are less vulnerable to future spikes in electricity rates. Also, a CHP system can be set up to run on several fuels including natural gas, biogas, coal, and biomass, thus a building can have fuel-switching capabilities to protect itself from rising fuel costs.
A steady flow of electricity to buildings at all times ensures that operations may go as planned. A resilient building is one that is able to prevent, endure, and recover from power outages brought on by storms and other disasters. Unpredictable power service poses a real threat to the health and prosperity of various businesses and institutions. Cogeneration heat and power (CHP) systems are self-contained, on-site power plants that can be configured to function independently of the local utility grid. In addition to being able to keep running in the case of a disaster or grid outage, CHP systems can be built to continue supplying electricity for essential functions, increasing the resilience of the facility.