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'Green Heat' in a UK City

by the CADDET UK National Team

INTRODUCTION

Sheffield Heat and Power Limited (SHP) was formed in 1988, after a five-year intensive market research programme. It began as a joint venture between Sheffield City Council and EKONO of Finland, an international engineering group with proven experience in combined heat and power (CHP) and district heating schemes. British Gas joined the scheme with a one-third share in 1992. Now the scheme heats over 3,600 homes, and most city centre consumers.

WASTE TO HEAT

The Sheffield 'green heat' scheme utilises heat from a local waste incinerator (which has a refuse capacity of 150,000 tonnes/year) to operate an independent district heating system within Sheffield city centre.

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The waste incinerator, Sheffield

The initial capital cost was 14 million pounds sterling. The heat produced by burning the refuse is used to generate steam via a water-tube waste-heat steam boiler. The steam then passes to three shell-and-tube heat-exchangers (two rated at 18 MW and one at 25 MW) where it is condensed to produce a high-temperature hot water supply which passes directly to the SHP community heating system.

The hot water is pumped through a 36 km network of pre-insulated underground pipes, linking the main arterial network and clients' buildings. Heat is transferred into the customer's own heating system using a heat-exchanger. The maximum output temperature is 120 C, and the average heat loss 0.1 C/km. The connected district heating load exceeds 130 MW and consumes about 120 GWh/year of thermal energy.

'Green heat' is already supplied to all types of developments within the city centre, including hospitals, universities, offices, public buildings, retail outlets, leisure centres and housing estates.

BACK-UP

Security of supply is essential to the success of the scheme. The pipelines incorporate an electronic monitoring system and full back-up facilities. Stand-by and peak overload heat generation capacity is provided by four boiler plants situated throughout the network, ensuring integrity of supply. However, the fundamental reliability of the system is demonstrated by the fact that between 1988 and 1994 standby boiler plants were used on only five occasions.

CLINICAL WASTE

SHP formed a subsidiary to operate the UK's first independent commercial clinical waste incineration plant. Completed in March 1991 and costing 1.5 million, the plant serves the Sheffield and Area Regional Health Authorities. Fitted with waste heat recovery equipment, it provides 2 MW of thermal energy to the district heating network.

THE BENEFITS

The 'green heat' scheme is one of the most environmentally acceptable methods of providing heat and energy. Burning refuse cleanly and efficiently, it reduces fossil fuel consumption, confines the emission of suitably cleaned exhaust gases, and minimises damage to the atmosphere. Every building connected to the scheme means that another source of pollution the building's boiler installation is turned off.

Over a seven-year period, from 1988-1995, carbon dioxide emissions of about
270,000 tonnes were saved. It is estimated that the use of a renewable energy source saved over 871 GWh generated from fossil fuels between 1988 and 1995, based on annual consumption figures.

Other environmental benefits include extending the life of landfill sites and cutting methane production by reducing the need to landfill waste.

FUTURE DEVELOPMENTS

SHP is continuing to develop the scheme which has recently completed its fourth phase. A
10 million programme has been initiated to improve the incinerator plant, in line with European standards.

7 million is being invested in a 6.8 MWe steam turbine scheduled to start generating electricity in February 1998. The electricity will be sold to the local distribution grid as well as meeting on-site demand at the Bernard Road Incinerator Plant.

The steam turbine is seen as the first step in running a large-scale heat and power station to serve a greater part of the city. A number of other sites are being investigated as potential small-to-medium-scale CHP generation plants to supply environmentally friendly heat, electricity and even cooling to more areas of the city.

SHP also operates a consultancy division offering know-how to other large organisations and local authorities who wish to consider the feasibility of setting up their own CHP/district heating schemes.

For more information contact UK National Team in Oxfordshire.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.