Supermarkets are traditionally energy hungry operations, using high levels of power to refrigerate goods, while having to heat the space between the aisles – and provide extensive lighting. The latest store from Sainsbury seeks to reduce energy consumption – and also maximize the use of renewable generation on site.

The company is seeking to achieve a Breeam excellent rating for its store with a  2,500 sqm sales area at Dartmouth, in Devon. This rating covers both its construction, servicing and operation. Overall, the company expects to cut CO2 emissions from the store by 40% compared to a traditional retail unit.

Lighting is a major source of energy consumption, traditionally consuming about 40% of the energy used on site. The design has sought to minimize that with the extensive use of LEDs in the refrigerators and avoiding lit signage. However, the maximum gains will be achieved with the use of 82 sunpipes which bring daylight through the roof into the store. The company claims that this is the most extensive use ever made of these highly polished prismatic devices. A sophisticated computer system has been installed which can shade the sunpipes when there is excessive sunlight and adjust the artificial lights to maintain levels in the store.

The renewable energy sources include wind turbines, solar panels and a biomass boiler, which are estimated to reduce CO2 emissions by about 40% compared to traditional stores. The location at the top of a hill was appropriate for two turbines – the company is using the quiet revolution system that spin vertically, which are similar to those at  Sainsbury’s Greenwich store in south east London. “This system does not disturb the local community which was an issue raised when the Dartmouth store was being planned,” said Alison Austin, Sainsbury’s environment manager. The turbines are expected to generate the amount of electricity equivalent to the power consumed by the store’s checkouts.  Solar panels fixed above the loading bay area and the plant room power extractor fans within the storage area.

Gas has not been brought on site, as the main heating source is a wood fuel biomass boiler, which is claimed to be only the second time that a store has used such a heat source. The retailer has an agreement with a local company, which will collect and prepare the timber before delivery to the site. “The timber would have gone to landfill,” Austin explained. A heat recovery system has been installed which captures the exhaust heat from the refrigeration equipment and circulates it through ducts into the sales areas to complement the heat from the biomass boiler.

The new store uses a glulam timber frame, which are now becoming increasingly common in new supermarkets replacing steel structures which have high levels of embodied energy. The timber however had to be brought in from Austria but it will improve the store’s thermal performance.  It also allowed the company greater flexibility in design. The unsupported ‘S’ curved wave effect roof gives the inside a more airy and spacious feel, and externally it looks more interesting than a standard store.

Rainwater collection has been incorporated in the scheme with large tanks being installed underneath the car park. The water is being reused for flushing the toilets and watering the landscaping.

The delivery vehicles have a dual fuel system, running on mainly biomethane produced from landfill sites alongside a shot of diesel. They emit 60% less  CO2 emissions than standard diesel vehicles.  The store is located on the edge of Dartmouth next to a park and ride car park serving a wider area on the town’s west side. Its impact on trade in the town centre is an issue to be addressed. And with the sizeable car park, car usage will dominate. The site does include extensive cycle stands but sitting at the top of a hill they may only attract the fittest cyclists.

The construction costs were about 10% more than a traditional store but the company expects them to be recouped over quite a short period as the running costs are estimated at about two thirds of a traditional store. It is now looking at applying the lessons to a wider range of its stores including those at petrol filling stores. “The formula will have to be adapted to the location,” said Austin. Tight urban sites will pose different challenges, she added.