City of London

Citigen owns and operates the unique combined heat and power plant in the heart of the City of London, providing around 25MW of electrical output to the national grid. This CHP generation process also produces up to 28MW of heat and chilled water which are delivered to our client's premises to meet their heating and air conditioning requirements.

The scheme is one of only four large-scale urban CHP systems in the UK and one of only two to produce and distribute chilled water for use in air conditioning.

Citigen serves numerous City of London buildings including the historic Guildhall, the Barbican Arts Centre, the Guildhall School of Music and Drama, the Museum of London and London Central Markets (Smithfield) as well as other major commercial customers.

The main Citigen site is situated behind a listed building frontage and has been home to power generation in different forms since 1893. At its centre lie 2 Wärtsilä Vasa 18V46GD internal combustion engines capable to run on either natural gas or distillate fuel. The engines are equipped with twin ABB VTR 5644-42 turbochargers.

The cooling system on the plant is divided into high, medium and low temperature systems and includes a number of heat exchange components that are able to reclaim useful heat energy from the exhaust gases, the engine jacket, oil cooling system and the turbocharger intercoolers. This heat energy is distributed to Citigen's clients at a normal operating temperature of around 105°C. A number of boiler plants provide back-up generation.

During the summer months, heat is used to generate chilled water at 5°C using 2 absorption chillers (one retained as standby) rated at around 5.5MW each. Alternatively, two screw compression chillers rated at around 550kW each can be used to supply low levels of chilled water demand.

In addition to providing a secure, reliable source of electricity and hot and chilled water for heating and air conditioning, the plant is designed to be environmentally friendly being fitted with flue gas treatment and a selective catalytic reduction system.