Combined Heat and Power (CHP), also known as cogeneration, is referred to as the process of using a heat engine or power station to produce electricity and useful heat simultaneously. Usually, CHP, a type of distributed generation system, is located at or near the consumption point. In fact, CHP is proven extremely beneficial in generating useful thermal energy and electrical power. So, there is no need to purchase electricity from the local utility and then after burning fuel in a boiler or furnace to produce thermal energy.
CHP is inherently capable of providing higher efficiency and avoiding transmission losses in the time of delivering electricity from the central station power to the end-user. This obviously results in reduced energy use and greenhouse gas (GHG) emissions.
Every CHP operation is associated with several processes including recovery of wasted thermal energy to generate cooling, heating, electricity, or other thermal energies. The most common CHP configuration is known as a topping cycle. The topping cycle is usually referred to as a cogeneration process in which thermal energy generates electricity followed by useful heat application in industrial activities. In the topping cycle, fuel is first burnt in a heat engine or prime mover to produce power. After that, the waste heat from the power generation equipment is utilized to distribute useful thermal energy to the site.
For example, a gas turbine or reciprocating engine produces electricity by burning fuel and then uses a heat recovery unit to capture the useful thermal energy generated from the prime mover’s exhaust stream and cooling system. Alternatively, steam turbines use the high-pressure stream from a fired boiler to produce electricity before transmitting the lower pressure steam to an industrial process or district heating system.
In fact, it is possible to use waste heat steams to generate power. In this process, fuel is at first burned in a boiler to distribute thermal energy to an industrial process, and then the waste heat retained from that process is used to generate power. That is why it is often called waste-to-heat power.
No doubt, CHP technology can be installed quickly with few geographical limitations. In fact, it provides a cost-effective way to use a variety of fossil fuels and renewable fuels. The usage of CHP technology is mostly seen in industrial, large commercial, and institutional applications. The size of a CHP system can vary from 5 kW to several hundred MW. However, to run it efficiently, there is always a need for continuous thermal demand. That is why It is designed with the aim of meeting the user’s thermal baseload demand.
No doubt, CHP is not so popular outside of the industrial, commercial, institutional, and utility sectors. However, it is constantly providing highly efficient electricity and useful thermal energies to some of the vital industries, urban centers, largest employers, and educational campuses in the United States.
Our country currently has the capacity of generating 85 gigawatts (GW) of electricity. However, the largest part of US electric generation does not make use of waste heat. As a result, the average efficiency of the utility of our country has remained at approximately 34% since the 1960s. In fact, the total energy loss due to wasted heat in the US power generation sector is greater than the total energy consumption of Japan. In fact, CHP is responsible for currently supplying only 10% of our country’s electricity. However, it has more capacity and should supply more.