Refrigeration and the Road to Net Zero: Water-cooled Refrigeration
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INDUSTRY FOCUS
by
Stuart McLeod,
Project Manager at Oaksmere Design
Refrigeration and the Road
to Net Zero: Water-cooled
Refrigeration
Oaksmere Design and the shops across the UK and Channel Project background
John Lewis Partnership Islands, including 59 convenience
stores and 27 Welcome Break The John Lewis Partnership brought
Oaksmere Design is a locations. The supermarkets are forward its ambition to be net zero
multidisciplinary engineering served by a network of distribution carbon across its entire operations
services and contracting business centres and two head offices in by 15 years to 20353. To help
based in Ipswich that specialises in Bracknell and London Victoria. with this commitment emissions
supporting the food retail industry. Waitrose also operates an online associated with refrigeration - which
Oaksmere manages a range of delivery service with an associated contribute to operational C02e
energy and capital maintenance ecommerce store pick operation emissions through high energy
projects but has a particular strength fulfilling online orders1. consumption and the use of high
in refrigeration engineering. The global warming potential (GWP)
following article focuses specifically In 2020/21 the John Lewis refrigerant gases - are being tackled.
on Oaksmere’s design and project Partnership consumed 799,208,795
management input to Waitrose’s kWh2 of electricity and gas. The Globally the Carbon Trust estimates
THE EMA MAGAZINE • ISSUE MAY–JUNE 2021
water-cooled refrigeration rollout. highest area of energy consumption that the food cold chain is
across the estate are refrigeration, responsible for 1% of GHG emissions
Waitrose is part of the employee- HVAC, and lighting. In 2020, 97% and that the UK food cold chain
owned John Lewis Partnership, of electricity consumption across is responsible for 2-4% of GHG
which is the largest employee- the Partnership’s physical estate emissions in the UK4. Due to a rising
owned business in the UK with was from REGO certified renewable population and increasing food
over 80,000 employees known as sources and is working with landlords demand, the Economist Intelligence
Partners. Waitrose has over 331 to convert the remaining 3%. Unit predicts a 2.8% annual growth
1 John Lewis and Partners Our Business https://www.johnlewispartnership.co.uk/about.html
2 John Lewis Partnership PLC 2021 Annual Report and Accounts www.johnlewispartnership.co.uk/annualreport
3 www.johnlewispartnership.co.uk/media/press/y2020/waitrose-and-john-lewis-set-out-bold-plans-to-reach-more-customers.html
4 The Carbon Trust. Net zero cold chains for food | Carbon Trust
25
rate for commercial refrigeration in a water-chilled loop. Cascade reduced refrigerant charge are due
between 2018 - 20305. Therefore, and transcritical systems introduce to waste heat from the refrigeration
solutions to tackle GHG emissions greater complexity in design, build cycle being rejected to a water
from refrigeration play a key role and maintenance and R744 systems chilled loop, which is connected to
in meeting private, national, and require two stage compression on cabinets and coldroom equipment
international emissions targets. frozen food applications due to high housing self-contained refrigeration
discharge temperatures. loops, rather than to roof mounted
Since the John Lewis Partnership condensers. There is no mechanical
purchases 97% of electricity To summarise, water-cooled cooling required on the water
through a renewable energy refrigeration systems can reduce chilled loop, which operates at
contract this greatly reduces the the entrained volume of gas and between 40⁰C and 46⁰C, only
carbon emissions associated with the average GWP of gas entrained in dry air coolers for heat rejection
electricity consumption. The move the system by replacing the type of which negates the need for central
to water-cooled refrigeration is refrigerant gas. While CO2 systems compressor packs. The systems are
primarily to eliminate the use of also operate with low GWP gases, estimated to achieve main meter
high GWP refrigerant gases. Water- systems are more complex and electricity savings in the region of
cooled refrigeration systems can potentially hazardous. This article 20%.
dramatically reduce the entrained
volume of refrigerant gas in the
system, by helping to move away
from centralised direct expansion
systems that require large volumes
of refrigerant gas. When water-
cooled refrigeration systems are
designed to incorporate self-
contained refrigerated cabinets
operating with low GWP refrigerant
gases the benefit is amplified. In this
respect, the partnership states that
R290 and R1270, which have GWP
ratings of 3 and 2 respectively, must
be used where possible in place of
gases with higher GWP.
Fig. 1 - Cabinet ‘top box’
Cascade and transcritical CO2
(R744) refrigeration systems were focuses on a recent replacement Since the water chilled loop is
also considered due to the low scheme to help illustrate some piped to the ‘self-contained’
GWP rating of ‘natural refrigerants’ of the challenges and benefits refrigerated cabinets and coldroom
THE EMA MAGAZINE • ISSUE MAY–JUNE 2021
(R744 has a GWP of 1). There are, associated with the wider project. equipment, less pipework is needed
however, drawbacks associated for refrigerant and therefore less
with cascade and transcritical C02 refrigerant gas. Basically, creating
refrigeration systems. For example,
Water-cooled refrigeration: water-cooled integralised systems.
R744 systems have extremely high
Through the generations The system also operates with
operating and standstill pressures, The latest specification currently natural refrigerant with very low
which can be hazardous if pipework on the estate is known as GWP values. Figure 1 provides
is damaged. In some places system 3rd generation water-cooled an illustrative example of the
pressures can be up to 120 bar, refrigeration. The main benefits of self-contained refrigeration unit,
compared to just 2 or 3 bar found reduced energy consumption and colloquially known as a ‘top box’,
5 The Economist. The cooling imperative - forecasting the size of future cooling demand (2019) http://www.eiu.com/graphics/marketing/pdf/
TheCoolingImperative2019.pdf
26
which sits on top of each cabinet. The second generation of water- Furthermore, 3rd generation
While the 3rd generation represents cooled refrigeration chilled the systems are less complex than
the current specification, it is worth water and glycol mix to two generation 2.
reviewing previous generations separate temperatures through
to understand the journey of a complex set of pipework.
innovation. HT cabinets were served by a
Project brief
temperature between -6 and 0⁰C At Waitrose Norwich, all existing
The first generation of water- and LT cabinets were served by a shopfloor LT and HT refrigerated
cooled refrigeration chilled the temperature between 6 and 12⁰C. A cabinets were replaced with 3rd
water and glycol mix to between key difference between generations generation water cooled cabinets
18 and 24⁰C, which was achieved 1 and 2 was that HT cabinets did not and several smaller air-cooled
via hydrocarbon water chillers have their own condensing units, integral cabinets, each of which
providing progressive ‘free cooling’ rather they used the water glycol were entrained with R1270. The
below 18⁰C. Ultimately this meant mix directly in the coil of the cabinet seven existing cold rooms were
central refrigeration plant was to provide the required cooling replaced with four cold rooms
required for the water chilled loop. duty (secondary refrigeration). that occupied a similar footprint.
Like generations 2 and 3, the system Natural refrigerants were also used Cold rooms incorporated into
utilised cold aisle air retrieval and in generation 2 water chiller plant, wider water-cooled systems had
waste heat recovery to increase so there was also a large benefit previously been fitted with self-
secondary benefits to store heating for GHG emissions. Energy usage contained air-cooled or water-
and cooling. The average annual requirements were, however, greater cooled units, that were housed
energy savings, when comparing due to lower cooling requirement. directly on top of the cold rooms.
against a standard direct expansion Furthermore, the system was more At the time, system design was
system, were estimated in the complex to build and maintain. transitioning to incorporate a new
region of £35,000. First generation self-contained refrigeration unit also
water-cooled systems also displaced The main benefits of 3rd generation capable of rejecting heat to a water-
R404A with a significantly reduced water-cooled refrigeration, chilled loop. Since the new system
volume of natural refrigerant, when compared to 1st and 2nd was still in trial, the cold rooms were
helping to achieve large GHG generation, is there is no need fitted with direct expansion HFC
emissions reductions. to chill the water-cooled loop. evaporators entrained with R448A.
THE EMA MAGAZINE • ISSUE MAY–JUNE 2021
Figure 2 – Roof mounted dry-air coolers
27
Figure 3 – Internal pump station for the water chilled loop
Since the 3rd generation water- online in a coordinated effort stock. In the last year there has also
cooled cabinets have a condensing between the electrical, mechanical been a rapid expansion of the store
unit on each cabinet rejecting heat and refrigeration contractors and pick ecommerce operation, which
to a water-cooled loop, the roof Waitrose merchandising. Four new increases foot traffic overnight as
mounted condensers were rendered direct expansion condensing units online orders are fulfilled by in-store
redundant. The same was true for were located on the roof condenser picking teams. To minimise disruption
the central compressor packs given platform to serve the cold room to online orders, the Waitrose
that each self-contained cabinet also evaporators, two for the HT plant Norwich ecommerce operation was
houses its own compressor within and 2 for the LT plant. The fluid temporarily relocated to a nearby
the ‘top box’ providing cooling for medium for the water-cooled loop store. Furthermore, planning for the
the cabinet. Instead, centralised was water with 15% MonoPropylene project had to be carried out during
pumps were required to circulate the glycol. All reclaimed R404A/R407A Covid restrictions, which introduced
chilled water and glycol mix. Finally, was removed and sent for re- new ways of working.
given that the function of the water manufacturing and banking. All
chilled loop is to act as a medium for control panels were replaced, and Site access presented a challenge for
THE EMA MAGAZINE • ISSUE MAY–JUNE 2021
heat rejection, with all water-cooled the frozen food, meat and dairy the removal of existing cabinets and
fixtures condensing at a suitably chillers were fitted with a trapped delivery of new cabinets, due to door
high enough temperature, waste man & gas leak detection system. heights and locations. For instance,
heat removal is possible by use of the front doors lead to a busy main
simple roof mounted dry-air coolers. road which has limited parking
Operational feasibility and is on a slight incline, while the
All redundant compressors were Waitrose stores usually remain open warehouse shutters are obstructed
decommissioned and removed in for the duration of a replacement by a loading dock leveller. The fire
accordance with a suitable phasing scheme and in most cases, stores are escape doors, which lead from a
plan to ensure existing packs were operational 24 hours a day, although ramp directly to the sales floor,
unaffected by light loading. The new not trading, and 7 days a week provided the best access but they
water-cooled plant was brought as night teams work to replenish are neither wide nor tall enough.
28The solution was to remove a set of than 4) in the air-cooled integral net zero, innovative refrigeration
handrails next to the door, build a cabinets. technology must remain at the
temporary platform and temporarily forefront of system design. The
increase the height of the door. Based on recent recorded challenges faced at Waitrose
The new layout of the cabinets refrigerant leak rates, water-cooled Norwich in converting the entire
also presented a challenge in that refrigeration at Waitrose Norwich is system to water-cooled refrigeration
drainage had to be relocated from forecast to save 36 tonnes of CO2e illustrates both the scale of
a gravity fed system at the location annually from direct emissions. the challenge and the scale of
of the existing cabinets to a vacuum Across all sites completed in 2020 achievement when we face issues
fed system located in the warehouse. there is an estimated annual saving head-on. While 3rd Generation
of 2336 tonnes of CO2e. In 2021 the water-cooled refrigeration
A crane was required to remove the projected figure increases to 3125 represents a step on the journey
existing direct expansion condenser tonnes of CO2e. to net zero in refrigeration. The
units from a roof mounted steel next step on the road to further
support structure and install the The projected estimated energy improvements are to utilise A2L
new dry air-coolers. Fortunately, saving at Waitrose Norwich, based gases in the coldroom plant.
there was sufficient space on the on like for like savings between
roof to build a new steel structure, January and March, is 1,039 MWh, Continuous improvement to system
alongside the existing structure, which represents a like for like design has also led to the adoption
to house the new condensing unit main meter saving of 24.5%. The of new self-contained units, which
required for the coldrooms. reduction in energy consumption is provide an improved solution for
mainly attributable to the removal cold rooms. The self-contained units
To minimise disruption to of centralised refrigeration plant. reject heat to the water-cooled loop
customers, sound deadening in the same manner as the current
material was placed on the roof There is also an energy reduction system, but they have an improved
to prevent vibrations through the benefit in replacing fixed-speed lifespan. The new units have been
supporting steels and into the store. compressors with inverter-driven incorporated into the standard
The existing compressors were compressors, which is a benefit specification from 2020 and they will
removed from an internal plant specifically associated with the be incorporated into future systems.
room by cutting up the equipment evolution from 1st to 3rd generation To date nearly 200 Waitrose shops
and removing piece by piece, water cooled refrigeration. The across the estate have undergone
making room for pumps required for energy reductions are partly offset a water-cooled refrigeration
the water-cooled refrigeration loop. by an increase in consumption at replacement. In line with the John
Installation of the new pipework the cabinets, however the result Lewis Partnership’s net zero 2035
was completed in the four weeks is still an overall reduction. Aside ambitions, the aim is to replace
leading up to the installation of the from a 24.5% cost reduction, the all existing direct expansion
new cabinets and cold rooms. reduction in energy consumption refrigeration systems with water-
also translates to a 24.5% reduction cooled refrigeration by 2030.
THE EMA MAGAZINE • ISSUE MAY–JUNE 2021
in carbon emissions related to
Project evaluation energy production, transmission,
and distribution. Author’s profile:
Prior to the water-cooled refrigeration
project at Waitrose Norwich, there Stuart McLeod is a Project
was approximately 700kgs of R448A Manager for Oaksmere Design with
Future plans
(GWP 1390) entrained in the system. responsibility for delivering client
The water-cooled refrigeration project Leveraging innovation in energy efficiency projects. Formerly
reduced the entrained volume to refrigeration design has led to an Energy Manager for Morrisons
64kgs of R448A across the cold rooms, massive reductions in energy Supermarkets, Stuart has a range of
52.1kgs of R1270 (GWP 2) across the consumption and GHG emissions experience across HVAC, lighting,
main cabinets and 3.35kgs of mixed from refrigeration. As we continually refrigeration, demand response and
hydrocarbons (with a GWP of less strive to meet the challenge of sustainability reporting.
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