Tesco Ireland is becoming a greener grocer as more and more of its stores incorporate more and more energy-saving elements. Indeed, Tesco’s new Cabra store in Dublin can boast of being Ireland’s first zero-carbon supermarket.
As part of its global strategy, supermarket retailer Tesco is actively working on measures to ‘create a revolution in green consumption’ and to ‘tackle climate change’. Rated the third largest retailer in the world with operations in 14 countries, the Tesco Group has set itself the target of becoming a zero-carbon business by 2050. Notably, Tesco Ireland is playing a leading role in pioneering environmentally-friendly initiatives.
Four years ago in Tramore, Co Waterford, Tesco Ireland opened the company’s first eco-store, designed and built as the world’s first PassivHaus accredited supermarket, it uses 45% less energy than a supermarket of a similar size and set a new benchmark for green technology and construction in retail.
Now the company has raised the bar on that benchmark by opening Ireland’s first ‘zero-carbon supermarket’ on a 3.4 acre site in Cabra in Dublin. The outlet has a gross floor area of 5,502m2 and is the fifth zero-carbon supermarket within the worldwide Tesco organisation. A supermarket of similar size built in 2006 would produce 2.15m Kg of CO2 each year, but Tesco Cabra produces 1.2m Kg, thanks to the energy efficiency measures put in place, more than 44% less than would be produced six years ago.
The energy efficiency measures include:
- Thirteen roof-lights, plus sun-pipes, provide the shop-floor and staff areas with daylight illumination, allowing an 18% reduction in electrical lighting.
- Energy-efficient lighting that automatically dims or brightens as natural daylight increases or decreases
- Motion-sensitive lighting ensures lights are automatically switched off in areas that are not occupied
- DALI (digital addressable lighting interface controls) controls to give greater control over lighting use
- The store is fitted with a high-performing building envelope, giving air-tightness better than 3m3/(h.m2)@50Pa
- Mixed-mode ventilation, where eight windcatchers allow for mechanical ventilation to be switched off.
- Cold-air retrieval (CAR) in refrigerated aisles recycles cold air for use in cooling warm areas in other parts of the store
- CO2 Refrigeration
- Rainwater harvesting reduces the amount of mains water used for toilet flushing
- A building energy management system and more than 50 energy sub-meters monitoring all items/areas of the store, including lighting, refrigeration, HVAC, small power and export to the National Grid to optimise energy consumption efficiency.
The Tesco Cabra store is a testament to Irish innovation in sustainable commercial development with companies such as Joe Doyle Architects (JDA), Dun Laoghaire; Precision construction Limited (PCL), Dublin; DCS Group, Tralee; JV Tierney, Dublin; F4energy CSM Ltd, Limerick; Walsin Ltd, Lisburn; Sipfit Ltd, Warrenpoint and Green BioFuels Ireland (GBI), New Ross to name just a few who all contributed to the success of the project.
CCHP Carbon Credits
Of course, the store’s operations still produce some CO2, but these carbon emissions are offset by carbon credits generated onsite by the store’s 350kWe biodiesel CCHP (combined chilling, heating and power) unit , built, installed and maintained by F4energy when it exports electricity to the national grid. The CCHP’s electrical efficiency is nearly 40%, which is very efficient indeed. Depending on the ambient temperature, waste heat for unit’s steam turbine is used to provide heating for the store’s air handling units when the weather is cold or the waste heat is used to drive the CCCHP’s absorption chiller providing cooling for the sales-floor AHUs when the weather is warm.
The amount of electricity produced by the CCHP far exceeds the store’s needs, allowing Tesco to export the surplus on to the National Grid. Not only does this exported electricity gain Tesco revenue from energy saves, the company also accrues carbon credits for displacing electricity that would otherwise be generated from burning fossil fuels, such as natural gas and bunker oil.
Because Tesco Cabra’s net CO2 emissions from electricity, gas and refrigerant use are zero or lower, it qualifies as a zero-carbon building. In fact, the amount of electricity generated by the Cabra CCHP from renewable biodiesel is such that the units output are used to offset the carbon emissions of other Tesco stores.
Tesco Ireland has been using CHP (combined heating and power) units since 2007, when it installed a natural gas powered unit at the Nutgrove Shopping Centre, which on its own is responsible for a 656 tonne saving in carbon emissions. Tesco has installed gas-powered CHPs/CCHPs at nine other locations across Ireland, but the Cabra unit is the first to be powered by biodiesel. It is an example of how Cabra is being used by Tesco to test a number of energy efficiency technologies, says Tesco Ireland’s Energy and Carbon Manager John Walsh, who also points to the pioneering use of LED lighting at the store. He said: “Will be using biodiesel CHPs at other locations? I don’t know – yes there is a saving on carbon emissions, but at the moment it’s a much more expensive way to generate electricity than natural gas!”
The biodiesel used is supplied by Green BioFuels Ireland (GBI) and is made from recycled vegetable oil and tallow. GBI operations manager Joe O’Byrne said: “Our primary market is supplying biodiesel for transport and that is likely to remain the case – the national target is that by 2020 biofuels will comprise 10% of all road fuels and at the moment we are only at 4.16%. Our contract with Tesco is our first heating contract and is a very welcome development that could be a major stepping stone into a valuable secondary market.”
The Cabra store, built on stilts over an at grade car park and a basement-level car park, was designed by Dun Laoghaire based Joseph Doyle Architects, a 12-person practice that has had a relationship with Tesco Ireland for the past 15-years.
Doyle says that even before you start examining the energy-efficiency measures within the new building, the Cabra store provides an indication as to how Tesco Ireland’s supermarket design has evolved over the decade and a half. He pointed out that this was a brownfield site, where for reasons of space a basement car park needed to be excavated to sit beneath the building and where construction is on quite a tight footprint surrounded by existing ‘live’ buildings. Cabra is like quite a few neighbourhoods in Dublin where there is an existing demand for a new supermarket but there is limited potential site availability and certainly no greenfield site to locate one. The store is to the rear of the Maple Centre, which was a development that wasn’t doing as well as it should have been, but it has now been boosted by the presence of Tesco. The immediate neighbourhood includes a library and social welfare office. It really is a holistic development that fits in with the surrounding community.”
Consultant engineers on the project were JV Tierney with the main contractor being Precision Construction, two firms that have worked repeatedly with Tesco Ireland in the past.
JV Tierney Associate Director Andrew Clifford said that while the practice acted as main consultants on mechanical, electrical, sprinkler and environmental design, it also used the specialist skills of its sustainable-design subsidiary JVTE to deploy the company’s most innovative engineering designs yet for this zero-carbon project. “We used thermal modelling software to assess the stores predicted performance. We used this information to set out the challenge to be met in order to ensure the store achieved zero-carbon status. JV Tierney worked with the Design Team and with Tesco’s Carbon/Environmental Teams to deliver on this challenge.
“The major difference between a typical Tesco Store and the Zero Carbon Store in Cabra is the ability of the building to operate as a naturally ventilated building when conditions allow. From the computer simulations modelled, we were able to demonstrate that this contributed to a significant reduction in the energy demand. Another major impact on a store’s energy consumption is the lighting. In Cabra, there are a number of large roof-lights installed evenly across the sales floor allowing natural daylight to aid lighting on the sales floors. The same principle was applied in the staff areas. The use of natural lights allows us to dim the buildings lighting throughout the day to achieve Tesco’s required lighting levels. The effect of this natural light gives a reduction of about 18% on the lighting load.”
The two-level car park under the building is lit using DCS Group LED lighting, which has reduced the energy consumption of the car park lighting by 50% and the lamp life has increased by six times compared to a standard fluorescent lamp. To further reduce the energy usage, the lighting is being separated into zones which are controlled via a time clock and PIR sensors. Additionally LED fittings were installed for the fridges and freezers on the shop floor further reducing the electrical consumption throughout the day.
Building work was to a fairly tight schedule: enabling works starting in January 2011; basement excavation and construction starting a month later; construction of the store itself, on stilts above the basement, started in May; the building was water-tight in September and was handed over to Tesco in October, with the store opening on November 21st.
The enabling works included demolishing an existing building that had been occupied by eircom and this work was complicated by the fact that it required the careful removal and disposal of asbestos. The fabric of the demolished building was crushed, for re-use off site, and the majority of the material excavated for the basement, 45,000m3, was also recycled.
“During excavation there were 5,000 loads removed over 47 days, which equates to 212 truck movements on site per day or a truck every 3.1 minutes,” said Pat O’Sullivan, MD of Precision Construction (PCL). “This was a logistical challenge, complicated by the restricted working hours on site set by the local authority – Monday to Friday 8am-7pm and Saturday 8am-2pm. We also had to ensure that the existing services network – mains water, foul water, surface water, gas, electricity, public lighting, telephone, broadband, etc, were maintained for our neighbours in the Maple Centre and the Dunard Housing Estate.
“PCL prides itself on a ‘can do’ ethos and we put a lot of effort into liaising with residents’ associations, local businesses and community groups to ensure good relationships were maintained. Truck movements were managed to avoid peak rush hour traffic and ongoing road sweeping and additional dust suppression was provided for neighbours. We also liaised with Dunard Football Club regarding development of their pitch and new kits for the club, liaised with Dunard Boxing Club regarding their clubhouse and new equipment and we sponsored a number of other community projects.
“This was a reduced carbon build and every single component, every truck movement, every decision was put through a ‘green filter’ where we set measurable and challenging targets on monetary and carbon costs, so that truck movements involved back loads where possible and 93% of demolition waste was recycled. We provided premium quality staff facilities and invested in the training of our people to ensure complete buy-in and that the labour force was committed to building greener.”
Precision Construction worked in partnership with Northern Ireland firm Sipfit to produce a customer-made insulated cassette timber panel – a SIP – that proved very successful in meeting U-values, air-tightness levels and environmental and architectural requirements. O’Sullivan said: “The building was built to an air-tightness level to achieve three cubic meters per hour at 50 Pascals or less, we actually achieved an average of 0.65 cubic meters per hour at 50Pa for the entire building.”
Explaining the system used, Sipfit’s owner Eamonn Connolly said: “Structurally insulated panels (SIPs) are a composite panel that provide superior insulation and air tightness with a light weight structural frame. Sips are structural and load bearing. The panels are bonded in a press and form a beam and we provide structural calculations certifying all our buildings.
“Delivering a zero-carbon store is not ‘run-of-the-mill’ – it requires an air tightness 10% better than PassivHaus and is based upon a fabric first methodology whereby the SIPs superior thermal performance, reduced thermal bridging and market leading air tightness are key.
“Developed in the United States, SIPs are a construction method that is becoming increasingly prevalent in Europe with the ongoing low-carbon journey and the rising fuel prices. The construction industry is conservative by nature, but we believe it is about to go through transformational change arising from the low-carbon and low-energy build agendas. Currently, we employ 13 people and our business is primarily UK based, but we are already starting work on Tesco Newbridge as part of its scheduled 10-year ‘refresh’ and we are in ongoing discussions re other Tesco projects in the UK.”
Another company involved in the Cabra project and looking to Tesco for repeat business is Walsin, a Lisburn-based architectural glazing company that has also worked regularly with Precision Construction. Founded in 1995, Walsin is an approved fabricator for Schuco and Metal Technology and has a growing portfolio of projects in the UK ‘from London to Aberdeen’, says Design Manager Stephen Moore. “Happily, we are much busier than we were two years ago and are getting a lot of repeat business. The great thing about working with Tesco is that they are a supply-orientated company – they know what they want and they specify it exactly. They’re very easy for us to work with. On the Cabra project, one of the key factors was just-in-time delivery, so that the glazing installation and the timber-panel installation were coordinated perfectly.”
Lighting and Energy Management
The LED lighting used on freezers and in the car park at Tesco Cabra was supplied and installed by DCS Group and its manufacturing sister company Frontline LED. Based in Tralee and founded by Donal Sugrue, DCS Group started by doing electrical contracting work with Tesco and branched out to provide energy and workplace management services to the commercial, education, industrial, retail and healthcare sectors. Sugrue then founded Frontline LED to design, manufacture and install energy-efficient LED lighting. Notably, at Tesco Cabra, all three elements of its services were/are used: energy management, workplace management, and LED lighting. DCS enjoys an extremely close relationship with Precision Construction, so much so that they recently co-sponsored a schools energy-efficiency competition.
While what has been achieved by DCS at Cabra is notable, what it has achieved at Tesco Stillorgan is spectacular, as that store is believed to be the first supermarket in the world to be fully illuminated by LED lighting. Such is the stir caused by Stillorgan among retailers that many of them are crossing the Irish Sea from the UK to see what has been achieved. More than 400 LED luminaires have been deployed across the shop floor, with accent lighting covering the bakery, deli, refrigerated storage and off-line areas. Overall lighting levels within the store have increased by 200% while the overall lighting load, and energy consumption, has dropped by 20%.
Notably, the LED lighting units come with built-in emergency packs, so they can perform as their own back-up safety lighting in the event of power failure. Additionally, at the lighting unit the current is converted from AC to DC to allow the LED lighting to work, so that the units can be easily installed onto existing legacy power systems.
DCS and Frontline have also overcome the one draw-back that has prevented LED lighting from being adopted more widely, a ‘cold’ colour. By using specialist coatings, the LED lighting in Stillorgan and Cabra has a warmth similar to that found with incandescent lighting – indeed the particular tone used is bespoke and is known as ‘Tesco white’. For another job, at Cork IT, DCS and Frontline provided LED lighting with an even colder colour tone to give a more clinical ambience!
There are more than 100 separate energy-saving measures in use at the Cabra store, says Walsh. “Not all of these measures will be used in all future Tesco stores. Cabra is a test-bed to see what really works. Tesco’s approach to climate change has three parts.
“We will lead by example and will keep cutting our own emissions, working on energy-efficiency and using new technology to produce renewable energy at our stores. We are committed to becoming a genuinely zero-carbon business by 2050.
“We will work even more closely with our suppliers to reduce emissions embedded in the products that we sell.
“And we want to empower customers and help them lead low-carbon lives by making green products more affordable, more available and more attractive. Working with others, we will also identify clear ways in which our customers can reduce their personal and domestic carbon footprints.”