Recycling Thermal Energy

by Edward Thompson

As concern about global warming grows, we all now know that steps have to be taken to reduce carbon consumption. On an individual level everybody is in favour of carbon saving in principle, but most people have done very little in practice. Part of the reason for this is that it is difficult to know what to do. Human beings are reluctant to change their habits.

Some may resolve to turn down their thermostats one degree next winter, or not jet off for a foreign holiday next year. Others feel good because they have increased their loft insulation. But most people feel that anything they may do individually is not significant enough to make a difference, but their conscience still troubles them because the gathering climate change issue spells big problems for future generations. Nine of the last ten years are amongst the hottest years on record.

Should we adjust our buying patterns and exert our power as consumers? Perhaps we can pass-off the problem to someone else! All families spend a lot of money in supermarkets.

What are supermarkets doing to combat climate change?

Supermarket chains, increasingly powerful forces in our economy, have become very large consumers of energy. They transport food around the world, spend energy expelling heat to the atmosphere to keep food cool and fresh, distribute packaging on a vast scale and then burn fossil fuels to heat up their emporiums so that we all feel comfortable enough to buy large quantities of food as we bow down at the new temples of consumerism.

Consumers are putting pressure on supermarkets to respond and they are doing so. There is a whole set of things that supermarkets can do to reduce the carbon consumption of their suppliers, their customers and themselves. They can:

• encourage the shift towards local, in season, produce
• encourage their customers to recycle plastic bags
• look at the architecture of their stores and
• shift toward using natural lighting and well tuned energy management systems.

They can also address the carbon intensive issues of the expense of cooling their food (and buildings in summer) and heating their buildings in winter with fossil fuels.

Tesco are addressing these issues seriously and are exploring ways to reduce their carbon emissions. These include using timber frame construction instead of metal to reduce embedded carbon, and adopting natural refrigeration systems using uses CO₂ instead of HFCs.

The "greener living" section of Tesco's website states its position: As a global business Tesco recognises an important role in helping to minimise climate change. To achieve this, in 2009 Tesco committed to:

• becoming a zero-carbon business by 2050
• reducing the emissions of the products we sell by 30% by 2020
• helping our customers to reduce their carbon footprint by 50% by 2020
• halve emissions from our 2006/7 baseline portfolio of buildings by 2020

These are ambitious commitments from a large organisation and Tesco now has a dedicated team exploring the ways in which it can reduce the carbon footprint of its stores and meet its commitment to "halve emissions from our 2006/7 baseline portfolio of buildings by 2020".

As part of this objective, Tesco has chosen ICAX's Interseasonal Heat Transfer as the sustainable heating and cooling source for its new store at Greenfield, near Oldham, which opened in December 2010.

The ICAX design provides cooling in summer by extracting heat from the supermarket and, instead of blowing heat into the atmosphere like an air conditioning chiller, ICAX stores the heat in ThermalBanks in the ground for recycling in winter.

ThermalBanks

An ICAX Thermalbank is constructed by drilling a set of 120 metre deep boreholes in the ground and using Rehau piping to heat exchange with cold ground in the summer (thus heating the ground). ICAX exchanges heat with warm ground in winter to recycle the summer heat back to the store in winter. Mother earth can be used as a Thermalbank if you know how to treat her.

When heating is needed in winter the ICAX system extracts the stored heat from the Thermalbank using a heat pump and distributes it within the building. This recycling of waste heat through the Thermalbank allows ICAX to deliver a significantly higher Coefficient of Performance than would be achieved using a traditional "unassisted GSHP". This saves on the cooling cost in summer and the heating cost in winter.

ICAX Skid recycles thermal energy

Interseasonal Heat Transfer is controlled by the ICAX Skid which looks at the most cost effective energy source at any given time, and enables the transfer of heat from where it is available most easily to the areas of the building that need heat. If heat is not available from these sources the system looks to extract heat from the solar charged Thermalbank using a heat pump and ground heat exchangers. The system also has access to an air source heat pump for those spring days when the external air temperature is rising and the heat store in the ground is depleted at the end of the heating season.

The ICAX Skid uses an intelligent approach to save energy and re-cycle heat whenever an opportunity arises.

Detailed design is critical

The detailed design of IHT follows the adage that every little helps. The sum of the innovations incorporated into the ICAX Skid leads to calculations that using Interseasonal Heat Transfer at the Greenfield Store will save 41% of the carbon emissions that would otherwise have been released if the standard approach had been used. The standard approach is to use air conditioning chillers to waste heat to the atmosphere in summer, and to burn gas to heat the building in winter.

There are many small things that Tesco can do to save carbon emissions and it is already doing them – every little helps.

There are some big things that Tesco can do to save carbon emissions with the help of Interseasonal Heat Transfer and it is now doing just that – every big helps too.

See also: Greenfield Supermarket recycles thermal energy.