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Beneath the surface

Following the installation of ground-source heat pump technology at its Crayford store, Sainsbury’s is rolling it out across its portfolio.

Sainsbury’s recent announcement that it is to install ground-source heat pump technology in up to 100 stores has been seen as a ground-breaking move in the proliferation of the technology.

It follows the company’s success with geothermal technology at its Crayford store in 2010, enabling it to supply 30 per cent of its energy from on-site renewable sources.

And while several companies will take responsibility for the installations, namely EO.N and Geothermal International, with the technical solution varying by partner, the functionality will be the same for the geothermal systems being installed, and is based upon the concept installed at the Crayford store. Each partner’s intellectual property is unique, thus there is no need for licensing agreements.

Sainsbury’s head of engineering, sustainability, energy and environment Paul Crewe says: “The technology is being considered for larger stores only, and being modular it can be tailored to suit an individual store’s requirements.

“As it is a closed loop borehole system there are no geological issues in terms of requiring access to water aquifers. So far the concept has been suitable for 99 per cent of the sites that have initially been reviewed – the only restrictions are water protection zones where it cannot be used.”

The systems are suitable for both new stores and retrofits, with four of the existing systems being the latter type. Retrofitting to either an existing store or as part of an extension incurs six to eight weeks of ground work in a limited part of the store’s car park, but once completed there is no other impact on customers.

Furthermore, the technology is being considered only for larger supermarkets where there is a car park owned by Sainsbury’s.

Mr Crewe said: “Gas usage can account for up to 30 per cent of a store’s energy demand, and this is all for space heating and domestic use hot water. The geothermal system removes the need for conventional gas boilers, and so for new stores it is not installed and in extensions/refits it is removed.

“The system supplies the total heating demand for the whole building. However, due to our optimised store design, we do not require any form of air conditioning for cooling on the sales floor at all. The geothermal design significantly enhances the performance of our refrigeration system, lowering its energy demand and enabling us to capture its waste heat, as well as significantly lowering its carbon footprint. We do, however, install electric immersion heaters within the hot water tanks as a backup for food safety reasons.”

There are no other supplementary or back systems installed to the geothermal technology, which, Sainsbury’s says underlines the level of commitment it has to the technology and its partners.

Mr Crewe said: “It means we support ‘right first time’ installation and commissioning, as well as continuing maintenance. This is perhaps unlike other organisations who install multiple systems with elements that can be turned off if proving problematical. An added benefit of this approach is that our data is clean and not muddied by other systems – we can see exactly what is happening and how it is performing. As the technology, IT and controls are evolving rapidly, we are already on the third generation of the geothermal systems, giving easy access to the required data.

Furthermore, the geothermal system has a double benefit: it is firstly an enabler for sub-critical CO2 refrigeration; and secondly, it reduces our carbon footprint by reducing not only the store’s energy usage, but also avoiding the impact of direct emissions from traditional refrigerants [HCFC and HFCs].”

While Sainsbury’s installed the first system at Crayford in September 2010, it now has five others installed, with plans for 20 by 2013. As with all new technology, the process of integrating into existing systems plus maximising the benefits continues to grow.

Mr Crewe says: “Inevitably the process will become faster over time. The technology forms an important part of the journey towards our 20 by 20 Sustainability Plan targets, and our stretching goal to reduce our operational carbon emissions by 30 per cent absolute and 65 per cent relative compared with 2005. Although our partners are responsible for running the geothermal technology on an ESCO (energy sevices company) style contract, we have already begun delivering a plan to upskill our service engineers. Through our work in our Carbon Academy we are training our FM contractors with the appropriate knowledge where they interface with the geothermal systems.

“This is another case where service engineers are acquiring new skills – not just natural refrigeration, but where it interfaces with low carbon geothermal systems.”

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