RandTech CHP Delivers Low-Energy Solution

Sainsbury’s bid to build a low-energy store on the Greenwich Peninsula was achieved through its low-energy design, offering a 50 per cent reduction in energy consumption compared to similar sized supermarkets. Within that energy saving package is the RandTech CHP (combined heat and power) system supplying electricity and heating to the building 24 hours a day, 7 days a week.

At the 2900 m2 (31,000 sq ft) retail store, RandTech has installed two units, the GEM 300 kWe and GEM 210 kWe employing MAN spark ignition gas engines, housed in an external plantroom within the site service area. The RandTech units generate up to 85 percent of the store’s electricity with the recovered heat from the engine being used to provide hot water to heat the building. Fresh air is drawn into the store through ground level vents and is heated as it passes over thin tubes through which the hot water flows. The rising warm air provides valuable background heating throughout the building supported by an underfloor piped heating system that converts recovered heat from the CHP into hot water via a plate heat exchanger. During the summer months this process can be reversed to cool the store by pumping free chilled water from two boreholes, 75 m deep and 450 mm in diameter, containing a 150mm pipe delivering a maximum 26 litres of water a second at a constant 12°C.

For greater control of the HVAC services, the RandTech CHP system was designed to integrate with the store’s building and energy management system (BEMS). This interface facility ensured that in the event of an incoming mains failure, the BEMS will provide a seamless ‘no-break’ transition to the standby power supply. The CHP system also maintains its own modem linked telecommunications capability for remote monitoring and control purposes.

The environmental benefit of maximising the output of the primary energy source is clear and was the driving force behind the choice of a CHP system. However, the associated cost savings offered by the RandTech system were equally significant. A typical GEM 210 installation will produce £204 worth of electricity and £74 worth of hot water from each £100 worth of gas consumed. In addition, the system will recover 75 per cent of the total generated engine heat. Another major financial factor was that the CHP system could be exempt from the Climate Change Levy that comes into force from April 2001.