CBus Case Study

Background
The UK’s commercial sector accounts for 19 per cent of total annual electricity consumption, a colossal amount of energy use at a time when overall demand across all user groups is rising. Taking steps to reduce energy consumption in commercial premises can have a substantial impact on both costs and carbon emissions.

Challenge
As one of the UK’s largest grocery chains, Sainsbury’s has recognised the challenges that climate change brings. As a result, it decided to make efforts to reduce energy expenditure in its stores. This also ties in with the company’s commitments to demonstrate “Respect for our environment”. One of those key commitments is to reduce operational carbon emissions by 30 per cent absolute and 65 per cent relative (to 2025).

Solutions
One of the key ways for Sainsbury’s to achieve this was to use lighting in stores more ef ciently. Research showed that a digital lighting control system can provide an energy saving of approximately 30 per cent if it is implemented correctly. However, it was important that in addition to being cost ef cient, any changes to the lighting system should not impinge on customers’ in-store experience.

Prior to the installation, lighting used approximately 20 per cent of a new store’s energy usage. The only way of controlling light was manually through relay panels which tended to be bespoke depending on the size of the stores and who was the installing contractor. Sainsbury’s was looking for a standardised solution to minimise consumption by utilising daylight as much as possible and also cut the energy by effectively managing less frequently used areas during operational hours. One other key requirement was to ensure that during non- trading hours, lux levels be set to a minimum level to allow for maximum energy ef ciency while still allowing staff enough light to restock the shelves.

Sainsbury’s, in conjunction with Schneider Electric and Symphony Automation, an expert C-Bus system integrator, developed a design that could be used in all supermarkets regardless of layout. Special consideration was given to utilising natural sunlight through the use of daylight harvesting technology in order to become less reliant on arti cial lighting.

Sainsbury’s tested a number of different systems before choosing to install Schneider Electric’s Clipsal C-Bus system in 400 of its stores across the UK. Schneider Electric was chosen due to both cost effectiveness and reliability of the system.

Results
Under the banner of “Project Graphite”, Sainsbury’s have started to roll out LED lighting across their entire estate and as part of this initiative have retro tted over 400 C-Bus systems. Project Graphite was recognised recently for its work in LED lighting both by Lux (Retail Project of the Year and Client of the Year) and CIBSE Building Excellence Awards (Lighting for Building Performance). Sainsbury’s was also energy audited independently by a reputed institute to verify the impact of installing C-bus system in their store.

For example, its store at Kings Lynn – Hardwick Place was tted with daylighting panels and the ambient lighting was set up so that it uctuated with natural daylight to maintain a constant 650 lux at 1-2 m above oor level. This delivered a performance of 13.6W/m2 over 12 months, a 35 per cent saving in lighting electricity and 14 per cent of the total store consumption. The saving in electricity costs was £35,000 and carbon was 187T CO2 e (Carbon Dioxide Equivalent).

The Clipsal C-Bus system has helped drive signi cant cost and consumption reduction across Sainsbury’s UK estates. In total it has reduced the lighting load by 30% and made the company 0.5 million in energy savings. In one year the system saved Sainsbury’s as much as 50 tons of CO2 emissions and £33,000 per store. In addition the system has actively and considerably reduced maintenance and down time costs across it’s estates.