Cogeneration: what it is, applications and advantages

 What is cogeneration?

Cogeneration is an energy solution, which produces all final energies every consumer center needs: electricity, heat and cold.

A cogeneration plant is usually made up of alternative engines, gas or steam turbines, which transform available energy in fuel. Normally fossil fuels, such as gas or oil, are transformed into mechanical energy and residual or exhaust heat. Mechanical energy is usually transformed into electrical energy through an alternator, and the residual heat can be recovered in the form of steam, hot water, thermal oils and hot gases, as thermal fluids and disposed for their thermal applications.

An important action plan would be to increase knowledge of cogeneration among citizens, executives and authorities, since it is a complete solution which is not always well understood, but of great importance, since it contributes directly to the fundamental pillars of European policy: climate change, security of supply and competitiveness.

Benefits of cogeneration

The main benefits of energy cogeneration are:

– Energy efficiency, which allows to reduce the country’s energy bill and the dependence on imports. Increasing cogeneration in a country can provide security of supply.

– Less impact on environment: By taking advantage of the same energy generation process to obtain electricity and heat, fewer CO2 fossil fuels are burned, reducing pollution, in the water and in the air. A very important factor in the fight against climate change.

– Reduction of economic cost

– It enables to industrialize areas far away from electricity distribution networks.

Types of cogeneration plants

There ares several cogeneration systems:

Simple cycle to generate steam or hot water: Gas, diesel or fuel oil are generally used as fuel. It is based on the production of low pressure steam or thermal oil, and on the use of the high temperature cooling water circle of the engine.

Simple cycle to harness direct gases: by harnessing directly heat from exhaust gases, without these passing through a boiler.

Cogeneration with steam turbine: This use is currently limited as a complement to combined cycles or plants of residual fuels such as biomass and waste.

Cogeneration in combined cycle with an alternative engine: The existing heat in the engine’s exhaust gases is recovered in a recovery boiler, by producing steam, which is used in a steam turbine, to produce more electrical or mechanical energy. The electrical performance of these plants is high while the thermal one is much lower.

Cogeneration with gas turbines: Here, part of the energy is transformed into mechanical energy which, with the help of an alternator, will transform it into electrical energy. Although it has an electrical performance normally lower than that of alternative engines, it has the advantage that they allow an easy recovery of heat from the exhaust gases.

Trigeneration

Trigeneration or “Trigen” is the simultaneous production of mechanical or electrical energy, heat and refrigeration, but from a single fossil fuel or solar thermal energy.Trigeneration arises from cogeneration energy and the addition of a new demand: cold.

Cogeneration applications

The suitable industries to install cogeneration plants are those with high thermal consumption and many hours of operation.

– Industrial sector: Chemical, petrochemical, ceramic, food, automotive, oil refining, CO production, waste treatment, pulp and paper, purification and water treatment

– Service sector, especially for air conditioning (hospitals, schools, universities, hotels, heated swimming-pools, airports, malls)

Cost of implementation of cogeneration projects

For this kind of projects, the amounts to be invested are usually very high, so they are not always possible for investors or for the cogeneration company in charge of managing the corresponging project. For this reason, funding must be sought to deal with initial disbursements.

In Spain internal funding (shareholders) or external can be used, and usually state funding, such as ICO loans or fundings from the IDEA, have been used.

Regulation of cogeneration

ROYAL DECREE 661/2007 of May 25, which regulates the electricity production under special regime“Promoting high-efficiency cogeneration based on the demand for useful heat is a priority for the European Union and its member states, in view of the potential benefits of cogeneration, in terms of saving primary energy, eradicating losses in the electricity grid and reducing emissions, in particular greenhouse gases……, increasing energy efficiency and improving security of supply, by creating a framework to promote and develop cogeneration. Despite this and the fact that cogeneration in Spain is a key energy tool for more than 600 factories in industrial sectors such as food, chemical, paper, refining, ceramics, automotive and so on, in our country cogeneration is not going throug its best moment. For this reason, the Government must become aware of it, as it has been requested from these sectors, in order to support the development of cogeneration and renewable energies, as other countries of the European Union are doing, for example Germany and Italy.

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