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Cogeneration

  1. Get To Know Energy > Multimedia > Infographics > Cogeneration

CHP (cogeneration)

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Under conventional arrangements, private users and companies buy their electricity from a power company and their fuel from the corresponding suppliers. This is a convenient means of supply but it is also costly and inefficient because it results in large losses in the form of unused energy.

CHP (Combined Heat and Power generation, also known as cogeneration) is a good alternative, because it is more economic and more ecologically friendly.

It allows electricity demand to be met without transmission losses, and it also makes use of residual heat. This means a saving in fuel and a reduction in the emission of pollutants.

CONVENTIONAL ARRANGEMENT

(Electricity from Power Company/Heat in industry)

La cogeneración supone una buena alternativa energética, más económica y ecológica. Permite cubrir la demanda de electricidad sin pérdidas por transporte, aprovechando además los calores residuales. Así se ahorra combustible y se reducen las emisiones contaminantes.

COGENERATION SYSTEM

Cogeneration System

CHP SYSTEM(Power and heat in industry)

With CHP, the user simultaneously produces two different types of useful energy, generally electricity and heat. This means that all the user's energy needs can be met with a considerable reduction in energy losses and thus in the amount of fuel used to produce this energy.

Four CHP technologies are commonly used, Different energy consuming industries use different ones depending on their heat and power needs, since each system offers different yields for each energy type.

Advantages

  • Reduces transmission losses, since the electricity is produced at the point of consumption.
  • The reduction in energy costs contributes to an improvement in company competitiveness.
  • Residual heat is made use of, thus producing a higher yield from the fuel. - This saving in fuel represents a reduction in emissions of pollutants into the atmosphere (CO2, SO2,NOx).

1. CHP with gas turbine

Sectors where this system is commonly used:

  • Industry: automotive, ceramics and tile-making, chemicals.
  • Services Sector: hospitals, hotels and sports complexes. (Places where, for example, it is used to obtain domestic hot water and for heating swimming pools).

This system offers high electricity efficiency and good heat harnessing. In addition, it is one of the least pollutant energy-generating technologies: emissions of CO2 and NOx are cut to half and SO2 emissions are eliminated altogether.

Recovery boiler

The residual gases are used to generate steam or hot water. For this purpose, they are piped into a boiler where they are used to heat the water to meet all or some of the plant's heat requirements.

Alternator

The turbine's mechanical energy turns the power generator to produce electricity.

Combustion chamber

Place where the natural gas is burned with compressed air. The gases given off during combustion are driven into a gas turbine to generate mechanical energy.

Compressed air

Compressed air generated by a compressor connected to the same shaft as the gas turbine.

Residual energy

High temperature gases (500º/600º).

2. CHP with steam turbine

Sectors where this system is commonly used: Widely used in industries that use large amounts of thermal and electrical energy, such as pulp and paper mills and the chemical industry.

This was the first CHP system to be developed and is habitually used with residual fuels, such as biomass or incinerable fuels. It generates less electricity but the overall efficiency of the facility is higher.

Residual Gases

The high temperature of these gases enables them to be used for heating water.

Boiler

Generates the steam required for the entire process, using the heat produced in combustion

Steam turbine

The high pressure steam is driven into a steam turbine, connected to an electric alternator, to produce electricity..

Steam at lower pressures

This low pressure steam is used in the production process.

3. CHP with a reciprocating engine

Sectors where this system is commonly used:

  • Primary sector: greenhouses
  • Industry: wood and cork, textile industry
  • Services sector: hospitals and sports complexes

This system offers very high electrical efficiency rates, although heat harnessing is slightly reduced. In some cases it is also used for producing cold through absorption.

Recovery boiler

The residual gases from combustion are introduced into a recovery boiler where low pressure steam or hot water are produced.

Reciprocating engine

This engine performs combustion and produces rotation, turning the alternator to produce electricity.

Other residual heat

The heat from the engine's cooling systems is also used to produce hot water.

4. Combined-cycle CHP

Sectors where this system is commonly used:

Industry: Electrical

It has sometimes been questioned whether this system is really CHP or cogeneration, since it generates only one type of energy, and not two. Nonetheless, its excellent performance in producing power makes it one of the most important technologies used by power companies for producing this "rich" energy.

* For more information, see Combined Cycle section.

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