refrigeration
air conditioning
heat pumping
Ian Tansley MInstR
Winner of the J & E Hall
Gold Medal
Extending the global reach
of refrigeration
– the development of a novel,
water based technology
Copyright © 2017
Institute of Refrigeration
Extending the global reach of refrigeration – The development of a novel, water based technology
Why this topic?
This paper describes the development of a refrigeration technology that delivers highly accurate
and stable temperatures at the same time as enabling energy storage. This paper will
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Explore the challenges of storing temperature critical products in an environment with
unreliable energy sources
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Provide a case study of how a new technology has been commercialised
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Explain the potential of an innovative alternative cooling cycle using a natural process
1 Background
Every now and then new challenges force innovation and some of these end up having far reaching
consequences. A Swiss electrical engineer George de Mestral invented Velcro when, in 1941, he
went for a walk in the woods and was inspired by burrs that stuck to his clothing – a good example
of early biomimicry.
Techniques for creating and controlling cooling will be well known to many reading this paper and
there is wealth of wisdom resting in the hands and brains of members of the Institute of
Refrigeration all of which is well targeted at solving the problems set for it.
What I have done is create something quite different from conventional thinking. Why me? Is a
question I often ask myself and I think the answer lies in the context of my world. I have a
reasonable understanding of refrigeration techniques, just enough to make choices but not enough
to innovate in the pure science.
What prompted my work in this field was 30 years spent focussed on the problems faced in poorer
countries around the world, particularly in Africa and Asia. Infrastructure is always poor and
resources scarce. Also technologies do not survive unless they have a fundamental strength and
those that work best work in harmony with nature’s wishes. Fanciful words but fundamentally
true.
My journey starts with my desire to deliver the benefits of clean, renewable energy to people in
real need. Where the technology is not only an incremental improvement but almost always life
changing.
For many years I designed and delivered solar powered solutions including lights that improved
education, water pumps supplying hygienic clean water and battery powered fridges that kept
vaccines cool in the baking Saharan sunshine.
To make any of these systems work when they are new requires some skill but not much.
Designing them to last for a long time and be cost effective is another level of challenge.
Ultimately, value for money comes from the ability of the equipment to last a long time. Any
technique that relies on batteries is bound to fail within a few years no matter how well it has been
engineered. Batteries are a collection of chemicals, put together to provide electrical energy
storage but they don't respond well to working at high temperatures and this makes them
unsuitable for long term use in the tropical environment.
The other big challenge in a refrigerator is temperature control. We think of the tropics being
always hot but seasons vary. Altitude plays a large part and deserts with clear skies can
experience huge swings in temperature over a 24 hour period.
Interestingly, it is well documented that more vaccine is lost to freezing in this context. For
vaccines, too much cooling is worse than not enough with around 75% of all vaccines having been
frozen before they reach the end of their journey.
The solution to this needed to have a number of key qualities namely
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Extending the global reach of refrigeration – The development of a novel, water based technology
1.
2.
3.
4.
Be robust – To survive the harsh treatment
Be able to store energy – so that batteries are not necessary
Protect vaccines from freezing – to combat the biggest cause of damage
Be simple – complex, engineered solutions are likely to be expensive and difficult to repair
The conventional approach to solving this problem is to line the walls of the refrigerator with ice or
‘Phase Change Material’ (PCM). Ice is of course a PCM of sorts and has the great advantage that it
is cheap, safe and has an outstanding latent heat of fusion but it has a serious flaw.
We tend to think of water freezing at 0°C. We commonly talk about temperatures ‘below freezing’
and whilst it’s true that water exists in the form of ice at 0°C, it takes something more to force
water to change its form to ice. This often doesn’t happen until the water goes below -5°C and so
to be sure it’s necessary to take water below -6°C hence the minimum, single star rating
requirement for freezers is to deliver a temperature of -6°C.
Figure 1 – How water freezes
Once some ice has formed the body of water/ice will absorb more energy at around 0°C and, once
the entire body is ice, will eventually drop below that temperature.
The reason why we can supercool water in this way is because ice forms from a nucleus. This can
best be seen demonstrated one of the many videos circulating on web site like You Tube.
This is significant in the storage of vaccines as an ‘ice-lined’ refrigerator will be designed to depend
on the ice having a surface temperature around 0°C in normal operation and some success in safe
vaccine storage can be achieved this way whilst the system/refrigerator is in controlled conditions.
But that’s not the real world.
In almost all of Africa and large parts of Asia mains power supply is intermittent. By the standards
in Europe and the USA this is a gross understatement. There is absolutely no expectation of power
being supplied from the grid for any more than a few hours at a time. Often the common practice
referred to as load-shedding means that limited power is supplied to different areas of a city in turn
– so at best you might receive 6 hours of electricity per day, the generating capacity being switched
between four equal areas for a ¼ of the day each. Frequent breakdowns, strikes, sabotage etc.
mean that this pattern is likely to be interrupted causing power outages that last for days, often
weeks.
Businesses will deploy backup generators but these are costly to run and maintain so their use is
kept to a minimum. The mass population accepts that it will receive electricity on an ad-hoc basis
meaning that a conventional refrigerator is of no use to them at all. Health facilities are mostly under
funded so suffer the same power outage conditions as the average consumer.
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Extending the global reach of refrigeration – The development of a novel, water based technology
In the case of vaccine refrigerators this is problematic as vaccine is very sensitive and must be kept
between 2°C and 8°C to maintain its potency. The solution until now has been Ice-lined refrigerators
but as we’ve seen above this has a problem. If the surface temperature if the ice lining needs to be
around 0°C and the power outage lasts long enough to melt the ice lining (which happens
frequently), then the ice lining has to be cooled to 6 or 7 degrees below Zero to ensure it re-freezes.
This means its surface temperature is 6 or 7 degrees colder than normal and if the total range of
2°C to 8°C is only 6 degrees, there will certainly be parts of the vaccine store that are now below
0°C and that’s not going to be good for the vaccines.
Vaccines deployed in poorer countries are difficult to monitor. They pass through the vaccine Cold
Chain. The design of the cold chain varies from country to country as it’s shape is dependent on
population size and geographical spread. Most commonly it would consist of the following:
1. Central Vaccine Cold Store – Usually a large, walk-in cold room close to the airport in the
capital – Mains power is present but a back-up generator regularly used
2. Regional cold store – smaller walk-in cold room or collection of large refrigerators powered
by very poor quality mains power and predominantly relying on the regular running of a
generator
3. District store – stand alone refrigerators with capacity of 100 to 200 litres – unusual if
these have mains power – more likely they’d be powered by solar energy
4. Health Centre – small refrigerators (around 60 litres or smaller) – certainly solar powered
5. Health Posts – Unlikely to have a refrigerator relying on visits by nurses equipped with
‘cold boxes’ from further up the cold chain. This system is referred to as ‘Outreach’.
Given the lack of resources at most people’s disposal, the geographical spread of populations and
the need to reach every child, the majority of vaccinations happen under some form of outreach i.e.
they don’t happen at a health facility.
Outreach also poses some challenges as conventionally ice is used to keep the vaccines cold when
they’re not in a refrigerator – This has proved very challenging given vaccine’s sensitivity to freezing.
It is perhaps surprising to learn that the majority of vaccines are lost due to freezing, even in the
hottest climates. This is the result of the widespread use of ice to provide cooling.
All vaccines are different and all are safe between +2°C and +8°C. Some will tolerate heat and some
might even not mind being frozen. There are typically around 6 to 8 vaccine types being administered
in a routine immunisation programme. The problem comes if each of these vaccines needs to be
managed separately – something impossible in practice so one cold chain – at the lower levels one
refrigerator - must cater for all. The context is that these products are passing through many hands
and, without occurring considerable expense, it’s impossible to keep track of every batch let alone
every vaccine vial.
Vaccines are routinely monitored in their bulk form (in the Central Vaccine Store) but as the parcels
of vaccine work their way down the cold chain they get split into smaller and smaller lots and their
monetary value reduces making it difficult to justify the expense of constant monitoring.
Of course, these vaccines are no less valuable or important if you’re sitting at the end of the cold
chain waiting to be vaccinated against a crippling disease like polio or one of the killer diseases still
rife in Sub-Saharan Africa. Little comfort to know that ensuring your vaccine was safe wasn’t ‘costeffective’!
We are learning new things about vaccines all the time. Most vaccines will tolerate a high
temperature excursion above the stated +8°C to around +20°C for considerable periods but of the
common ones used in Africa for instance there are almost none that can withstand freezing. Heating
might reduce shelf life or have a small effect on potency. Freezing a vaccine will cause it to ‘split’,
separating the carrier (adjuvant) from the effective part of the vaccine (antigen). What this means
is that the active part of the vaccine, although still living, cannot bind to the required molecules and
is therefore ineffective.
Perversely every vaccine vial has on its side a vaccine vial monitor (VVM). A sticker that changes
colour if the vial is exposed to temperatures above 8°C for some time so only high temperature
excursions are detected.
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Extending the global reach of refrigeration – The development of a novel, water based technology
To judge freezing there is only a subjective test at health centre level - The Shake Test – notorious
for being difficult or impossible to execute, especially if you’re a lowly health worker, deep down the
cold chain and only saw it demonstrated on a rare and long-forgotten training session some time in
the distance past. Needless to say the shake test is not to be relied upon.
Whilst sharp practice is very rare in the vaccine cold chain, it cannot be denied that faced with being
blamed for having vaccines go bad in your care, you might be tempted to pass them down the line
so that they expire under someone else’s care. Stock management is a problem.
This goes to emphasise the need for cooling technologies to be robust and not to rely on human
intervention. In this environment technologies need to be helpful and corrective, not challenging and
dangerous.
In the past kerosene driven absorption refrigerators have been deployed in some quantity – the
promise of cooling available anywhere that the high density fuel can reach is tempting. The lessons
learned from this are that a commonly used fuel is easy to steal and, given that temperature is
regulated by adjustment of a wick, the product is going to go out of temperature frequently.
Temperature excursions might be considered as the least of the worries with many health facilities
being destroyed by fires caused by this type of device. These units are now being replaced around
the world with solar driven refrigerators.
One problem remains from this old kind of device and that’s the challenges surrounding defrosting.
In hot and humid environments, as many of these units are, frost builds up quickly. This has a couple
of damaging consequences as frost will reduce the efficiency of the cooling device and what is to be
done about defrosting? The devices are in constant use, always containing vital vaccines. If these
vaccines are removed from the cooler they need to be put into a chilled space whilst defrosting takes
place – a process that could take a number of hours, even in tropical conditions.
Any ‘frozen plate’ type cooling system will form ice. This ice will grow as successive wet air is
introduced and whilst the refrigerator will have been designed to keep the frosting separate from
the vaccine, the encroachment of ice into the vaccine storage space is commonplace, once again
presenting freezing conditions to the vaccine.
In terms of managing energy inputs solar energy can also be said to be intermittent and it comes in
various degrees of strength as the sun rises and falls in the sky but it can, at least, be predicted and
relied upon. Some degree of energy storage is also necessary with solar driven refrigerators to
ensure cooling is available at night time. I have experienced temperatures above +40°C at night in
Northern Nigeria.
A lot is known about solar energy with maps, data sets and software freely available to make
accurate predictions on the statistical probability of the incidence of solar energy falling at any point
on the planet. These systems can get confused by micro-climates that produce significant anomalies
but knowing under what conditions these are likely to occur and using some local knowledge it
relatively easy to avoid being confused by these.
What water does
As luck would have it the same material that we use to make ice with its phenomenal energy storage
capacity has a singularly unique and useful property.
Water is heaviest at 4°C
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Extending the global reach of refrigeration – The development of a novel, water based technology
Figure 2 – Water – Density v Temperature
By heating water we make it lighter and like air it will rise. But cooling water below 4°C also makes
it lighter. That’s why ice floats when it’s dropped into a glass of water.
This happens because, when heated, water molecules gain energy and spend some of that energy
bouncing off each other and thereby taking up more space (becoming less dense). As the liquid cools
the molecules slow down, more and more until they have very little energy. At this point (4°C)
they’re packed quite close together. As the liquid cools further, the water molecules start to arrange
themselves in preparation for the phase change into a crystalline solid. This means they have to
take up particular positions relative to each other and this pushes the molecules apart taking up
more space again. The closer they get to freezing the more space is taken up. In other words the
same material becomes less dense again so ice will float.
To make use of this we create a body of water inside an insulated vessel. If we apply cooling to the
water near the top of the vessel the water inside cools and falls to the bottom. The warmer water is
lighter so remains at the top. The more cooling is applied, the more water is cooled to 4°C thereby
cooling the vessel from the bottom up.
Figure 3 – How Sure Chill Works – Part 1
Once all the water has reached 4°C something extraordinary happens. As further cooling is applied
the water cooled is now colder than 4°C. It is lighter and therefore it rises. Once its cold enough it
starts to form ice at the top of the vessel, building a body of ice progressively downwards.
Of course the water below can only be at 4°C. If it were any hotter or colder it would rise and mix
with the water/ice at the top.
If cooling is stopped when ice is formed, the system sits in equilibrium with water at 4°C in the
bottom half and ice in the top.
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Extending the global reach of refrigeration – The development of a novel, water based technology
Assuming the vessel is in a warm environment, heat enters the system and warms the 4°C water.
This warmed water rises, meets the ice and is cooled again maintaining 4°C water below. As heat is
introduced it simply melts the ice. It will not affect the 4°C.
Figure 3 – How Sure Chill Works – Part 2
The system can now be used as a refrigerator – so long as here is ice above, the water below will
all be at 4°C. Ice can also be loaded into the system manually, like dropping more ice into a glass
or it can be built using the water inside the vessel by a conventional refrigeration system. It’s worth
noting that there is a very narrow band of temperature gradient between the lower surface of the
ice and the water at 4°C. This means that its possible build a compartment, surrounded by water
that has a consistent surface temperature from top to bottom. This ensures that the air temperature
at top and bottom of the compartment is also at a consistent temperature.
So far only vapour compression systems have been employed by Sure Chill for the purpose of
freezing the water but there’s no reason that any other means capable of creating ice cannot be
used.
The technology is being used in over 40 countries in the form of a vaccine refrigerator with over a
dozen models of various sizes being manufactured in factories Africa and India. There is considerable
scope for expansion into other areas of refrigeration.
Might this work well for food?
Many foods will respond well to being refrigerated keeping fresh for longer and the target
temperatures for most foods (most particularly fruit and vegetables) is in the same range as
vaccines. In fact, it’s probably the same chemistry supporting the Sure Chill technology that makes
this true. Increased molecular activity through heating will increase the speed of the chemistry of
decomposition. Keeping at 4°C means the activity is least. Freezing can be helpful in some cases
extending shelf life even further but many foods are damaged by the process of freezing and when
brought back to edible conditions their structure is lost.
Around 30% of the world’s food is wasted each year. In Europe, and extraordinary statistic is that
200 million people could be fed from EU food waste. It totals 88m tonnes a year, and has a value of
Euro 143 billion. Of this, 52% is wasted at the point of consumption with much of this blamed on
poor management (over-buying) and misunderstandings about use-before and sell-by dates. Can
manufacturers of food product rely on the quality of domestic refrigeration to chill the product as
intended? How many households run their refrigerators in conditions used in the domestic
refrigerator performance tests? (check out your own fridge at Christmas) How many consumers
assume that putting a case of warm beer in the fridge with that leftover chicken will have no adverse
effect? Better quality cooling is bound to help but is only one component of the solution.
In poorer countries, where the food is being grown, most of the waste happens before the food
leaves the country. A strong example of this is green beans in Kenya. At the farm 26% of the beans
are discarded and a further 25% of the remainder are wasted at the Pack house. That’s a total of
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Extending the global reach of refrigeration – The development of a novel, water based technology
44.5% of the crop that goes to waste. Also in Kenya as much as 12% Tomatoes, 20% Avocados,
23% Mangos and 45% Bananas go the same way.
How about drinks?
Most soft drinks are designed to be consumed refrigerated. Despite the acceptable temperature
range of 0°C to 7.2°C for popular soft drinks this range is more the result of an acceptance of the
possible rather than a statement of the ideal. Temperature has a marked effect on taste – if you
doubt this try a warm cola. Our ability to taste sweetness is temperature dependent. There are
extraordinary levels of sugar in ice cream just so that it can be tasted when eaten cold.
Managing grid loads
Another benefit of this technique that has widespread benefit in industrialised countries is the ability
of the refrigerator to store energy. Much is being made of the use of Tesla’s new batteries to enable
loads on the grid to be balanced and for energy to be stored in a meaningful way. Another way to
think about this is for the energy to be stored within the refrigerator. Whilst we don’t need to provide
power-free cooling for days and weeks like we do in poorer countries, having a cheap, easy energy
storage built into every domestic refrigerator in, for instance the UK, could provide the National Grid
with a significant amount of flexibility. Refrigerators of this type could be designed to deliver faster
and more accurate cooling as well as better temperature distribution that would respond better to
over-load conditions.
Conclusion
We may not have reached the coverage that Velcro has today but with so much unrealised potential
there is no doubt that we’ve only seen the beginning of what this technology can do to improve the
lives of people around the world.
About Ian Tansley
Ian is an inventor with 30 years’ experience designing products and
working internationally to tackle difficult energy related problems.
Inventor of the Sure Chill Technology, Ian collected the Institute of
Refrigeration’s highest award, The J&E Hall Gold Medal, last year for his
innovative work.
References
Vaccine Wastage Assessment - UNICEF
http://www.mofa.go.jp/mofaj/gaiko/oda/seisaku/kanmin/chusho_h24/pdfs/a20-12.pdf
Super-cooled Beer ‘trick’ https://youtu.be/2jaguiubSIo
Global Food Losses and Food Waste FAO Report
http://www.fao.org/docrep/014/mb060e/mb060e00.pdf
Refrigeration for the Dairy and Horticulture Sector – Energy For Impact – Report commissioned for
The Sure Chill Company, August 2016
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Extending the global reach of refrigeration – The development of a novel, water based technology
Join us at this free open meeting
either by webinar below (to listen in live on 2nd February 2017 or be sent
a recording after the presentation)
https://attendee.gotowebinar.com/register/5606715832185243394
or register below to join the presentation at 5.15pm on 2nd February 2017
at the Hilton Garden Inn, Temple Way, Bristol, BS1 6BF
Register at: https://www.eventbrite.co.uk/e/cooling-with-intermittent-power-development-ofa-high-efficiency-water-based-refrigerator-tickets-27626124482
Hilton Garden Inn
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There is limited on-site
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Row
Presented before the IOR on 2nd February 2017
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