Different Types of Plants for Cogeneration
When we speak of cogeneration, it refers to the concurrent electricity production to energize operations while acquiring useful steam or heat for industrial processes. To have the simultaneous supply of electricity production, cogeneration plants are needed. There are topping cycle plants that produce electricity from steam turbine primarily. The drained stream is condensed while the released low temperature heat from the condensation is being used for water desalination or district heating.
For industrial processes, the bottoming cycle plants of cogeneration release heat with high temperature. To feed an electrical plant, a waste heat recovery boiler is fed. Apparently, the used of bottoming cycle plants is only done when the industrial processes require for a high temperature such as metal manufacturing and furnaces for glass.
Huge cogeneration systems provide heating power and water for an entire town or industrial site. The most common cogeneration plants are as follows:
- Gas Turbine or Combustion Turbine – this cogeneration plant uses waste energy released from gas turbines. The waste energy is commonly known as natural gas and extracted by a rotary engine from a combustion gas flow. The plant has a combustion chamber in-between and an upstream compressor connected to the downstream turbine. The gas stream is the combustor is added with energy in which fuel is combined with ignited and air. As the environment of the combustor increase pressure, the combustion of the fuel increases its temperature as well. The energy extracted from the plant is in the form of thrust, compressed air, and shaft power, or in any combination. These energy forms are used to power tanks, generators, ships, trains, and aircraft.
- Gas Engine – this cogeneration plant runs on a gas such as natural gas, landfill gas, producer gas biogas, and coal gas. This plant is heavy duty, slow reviving, and an industrial engine that is capable of operating continuously in full productivity for a period of time and with high fraction for many years. It also has an indefinite lifetime compared to a gasoline automobile that is lightweight and high reviving.
- Biofuel Engine – this cogeneration plant uses wide range of fuels in which some are derived from biomass. The fuels can be liquid fuels, solid biomass, and various biogases. Today, biofuels are gaining increased attention from public and scientific sectors because of different driven factors such as the concerns of greenhouse emissions from fossil fuels, the need for increased energy security, and oil price spikes. Bioethanol is a biofuel in form of alcohol that is made from fermented sugar components of plant materials such as starch and sugar crops. Meanwhile, biodiesel is made from recycled greases, animal fats, or vegetable oils, and this biofuel form as fuel for vehicles and as diesel additive.
- Combined Cycle – is a cogeneration plant that has the characteristics of utilizing more than one thermodynamic cycle that is similar with a power producing engine. With two or more combined thermodynamic cycles, such as the Rankine cycle and Brayton cycle, there is an improved overall energy efficiency.
Steam Turbine – is a cogeneration plant that uses heating system to condense the steam for steam turbine. It extracts thermal energy from pressurized steam and translates it into rotating state.