Cogeneration plants designed for industrial on-site applications provide the user with energy to power his requirements from the output of the plant.

Electric power is always generated, whilst thermal energy may be in the form of steam, hot air, hot or chilled water, or a combination of one or more of these options.

By accurate dimensioning of the plant and integration of the various heat recovery systems connected to the plant, the user will achieve the optimal energy balance.

Not only from the plant, but also the balance between the energy drawn from the utility companies and the cogeneration plant.

The key design factor for a successful industrial on-site cogeneration plant is to match the energy balance of the plant to the users requirements.

This is commonly achieved by dimensioning the plant in accordance with the users heat demand, and exporting surplus electricity to the Grid, or other external consumer.

However, due to local legislation, or simply due to very low prices for such exported excess electric energy, this may not be a feasible option in some countries.

In such cases, on-site industrial cogeneration still proves to be profitable by dimensioning the plant so as to avoid surplus electric energy, while still providing as much as possible of the user's thermal requirement.

Cogeneration in district heating

District heating systems based on cogeneration are designed to take advantage of large scale energy production, compared to local heat production.

Typically, such systems are built with an accumulation tank and auxiliary gas-fired boiler in addition to the cogeneration plant.

Accumulation tanks are installed to optimise the income from electricity generation by running the plant during periods of the day when the price for exported power is high, and the thermal demand is low. Heat can then be accumulated and pumped into the system during the periods of the day when the electricity price is low. The cogeneration plant may be shut down at the same time to save costs.

Auxiliary boilers are used either to boost the thermal capacity of the district heating system during periods of peak heat demand, or, if necessary, to boost the heat from the accumulation tanks, or simply as back-up to the cogeneration plant.

While providing the required heat for subscribers, electric power is also supplied to the Grid. Cogeneration based district heating systems are therefore a very environmentally friendly method in which to produce energy.

In the case where a gas-fired cogeneration plant replaces a coal-fired boiler system, the resultant positive environmental impact is considerable, particularly with regard to the reduction of harmful emissions.