As said in my previous article the self-cooling trail is literally littered with technological failures. There are thousands and thousands of patents about self-cooling containers and still we haven’t seen any reliable one in the market. In this issue we will have a look at the self-cooling developments and a look into the future of self-heating/self-cooling technology.
The self-cooling technology boils down to two options: endothermic chemical reactions and heat pump technology using water vapour as the heat transfer fluid.
Endothermic reactions tend to be weak. By contrast water evaporation can be a powerful cooling process, as evaporation of 10 ml of water can theoretically cool 330 ml of water by 18°C.
In Italy Freddo Freddo, the sister product of the earlier mentioned Caldo Caldo, employs the endothermic reaction between sodium thiosulphate pentahydrate and water.
I suspect that ScaldoPack is using an identical cooling system, in other words identical salts and water, as its cooling track is not that forceful.
Heat pump technology is finding commercial success in Europe for party keg sizes of beer. German CS-Metallbau GmbH developed a self-cooling refillable keg using Zeolite/Water-Vacuum Adsorption Technology. Zeolite is a non-toxic mineral that exists in nature. In dry conditions it adsorbs large quantities of water. Under vacuum the process makes it possible to produce ice.
But this article was intended for single-serve beverage packaging and not multi-litre packaging. So let’s have a look at the developments in that category.
Instant Cool Can
In 2006 a partnership of Tempra Technology and Crown Holdings introduced the Instant Cool Can. The Instant Cool Can was said to be a 100% safe and environmentally friendly self-refrigerating process that cools using brilliantly simple water evaporation. Tempra stated that in fact, it’s proven to lower beverage temperature by a minimum of 30°F (16.7°C) in just three minutes.
The design used thermal, insulating and vacuum heat pump technology, according to the description. The self-contained can was about the size of a 500 ml beverage can, holding approx. 300 ml (10 oz.) of beverage. This includes the beverage container itself, and the integral self-cooling device.
The can never made it to the market and is one of the additions to the “Gallery of Failures”.
Why did I refer to this Instant Cool Can. Well, recently, to be precisely in February this year, the online BeverageDaily.com proclaimed that “US firm Joseph Company International is launching the world’s first ‘self-chilling beverage can’ using licensed technology, even tested by NASA”. The test markets are “selected convenience stores” in Southern California and Las Vegas.
Mitchell Joseph himself told BeverageDaily.com how the technology worked: “There’s an inner unit called a heat exchanger, an HEU, and inside is an organic, renewable vegetable source done from activated carbon made from coconut shells.
The adsorbent that goes on there [….] reclaims CO2 that is already in the atmosphere, bringing it in and clearing the air away from it, and using that as the source of CO2.
Once you push the button on the bottom of the can, it then releases the CO2 from the activated carbon – it’s not absorbed, it’s adsorbed – then that becomes the last stage of your refrigeration system basically”.
The story is a bit wary, but it comes down to: “The can uses CO2 reclaimed from the environment and activated carbon ascertained from a renewable vegetable source”. Whether it works I can’t tell you. I haven’t seen it in the market. To be honest I haven’t been in Southern California or Las Vegas recently, but I haven’t heard of it anymore either. For the time being I believe that Joseph’s claim, that the Chill Can would “revolutionise the beverage industry, and the way the consumer perceives a cold drink”, looks a bit premature.
What’s left? Let’s have a look into the future.
The Future of Self-Heating and Self-Cooling
First we go back to 2006. In that year at the Solar 2006 Conference in Denver researchers of the Rensselaer Polytechnic Institute detailed that they’re making progress in developing a thin-film technology that ultimately could turn beverage bottles into climate control systems.
The ABE system being developed by Rensselaer Polytechnic Institute accomplishes the jobs of both cooling and heating, yet operates silently with no moving parts, using a thin-film technology that adheres both solar cells and heat pumps onto surfaces.
“The ease of application would make it possible to seamlessly attach the system to various surfaces”, RPI researcher Steven Van Dessel said. “It also may be possible to one day use the ABE system to create packaging materials for thermal control, which could lead to things like self-cooling soda bottles”.
Active Building Envelope (ABE) systems
Active Building Envelope (ABE) systems make use of solar energy and are a new technology for space heating and cooling, which integrate photovoltaic (PV) and thermoelectric (TE) technologies. In the ABE systems, a PV system is used to transfer solar energy directly into the electrical energy. This electrical energy is subsequently used to power a TE system.
Depending on the direction of electrical current applied to the TE system, ABE systems can operate in a heating or cooling mode, and can compensate for thermal losses or gains that occur through a building’s envelop or other thermal enclosure.
It is not surprising that we haven’t heard a lot about this interesting development after the first announcement. Research projects tend to consume a lot of time and the accent often lies on a range of industries, in this case from aerospace (advanced thermal control systems in future space missions), to the automotive industry, where it could be applied to windshields and sun roofs, giving the ability to heat or cool a car’s interior. Furthermore I read that attached to various building surfaces the system possibly renders conventional air conditioning and heating equipment obsolete.
In this lucrative field of potential applications the use of the system in packaging technology is certainly pushed somewhere in the background.
But whatever the case it is a development that we need to keep an eye on as it surely will surface in the future self-cooling and self-heating packaging formats.
Up till this point we have only spoken about self-heating or self-cooling of liquids, i.e. beverages. However the increasingly convenience-orientated consumer requires a means to heat all types of food and beverages including high viscosity liquids and solid products, i.e. thick soups, snacks including wraps, fajitas, stuffed pita bread, ready meals, pasta, rice and stews. To date the technologies for self-heating have been confined to quicklime/water reactions (with the exception of HeatGenie), where heat output is lower but the reaction is safer. But heating times can be long for solid food products since heat is transferred from the heating source to the product purely by conduction. The existing heating systems also have the risk that the solid food in contact with the heating unit is burnt, while the outside surface of the food is still cold.
Note: Although HeatGenie uses a different fuel source, the result doesn’t fare better in cases of solid food.
Direct Steam Heating
Although the company is victim of its failed developments and dissolved as of 11 Feb 2011, we have to take a look at a new heat transfer process Thermotic Developments came up with. The so called direct steam heating, ensuring excess water is present during the lime/water reaction, is a highly efficient system which transfers heat to the product by injecting steam directly into and through the food. Steam is a very effective medium for transferring energy, with 1g steam delivering around 2KJ of energy.
This is a very important development for heating ready-meals. So important that Crown, a company apparently very much interested in the field of self-heating and self-cooling, included the steam process in its vision of the future self-heating containers.
Ahead of the Pack Expo Las Vegas 2011, the PMMI (Packaging Machinery Manufacturers Institute) challenged the design community to envision how packaging will drive consumer purchasing decisions in 2020 and submit their ideas of what consumers will see on retail shelves in the year 2020.
Crown Packaging Technology took a shot at the future with its entry “The Fresh Can” visualising the upcoming and very promising trend of self-heating/self-cooling of on-the-go meals.
The Fresh Can
Shelf stable ambient foods, including vegetables, pasta, soups and ready-to-eat meals, can be heated in seconds thanks to in-can steaming technology from small self-heating pucks in the base of the package or heating by induction on ‘smart surfaces’. Steam heating provides improved taste and freshness and the all-metal construction is 100% recyclable. Metal packaging also saves energy by eliminating the need for refrigeration and freezing and reduces food waste by controlling portion size.
The interesting point in this concept is not the self-heating in itself, but the fact that Crown thinks in terms of steaming. In general, self-heating packages are using calcium oxide and water for the thermal reaction in a closed environment separated from the food stuff and this energy source is not sufficient for thoroughly heating of solid food.
Of course, Crown as a manufacturer of metal containers, talks about steaming ready-meals packed in metal containers. In my opinion there is no limitation to metal containers. Personally I see a bright future for self-heating in plastic/paperboard containers. Don’t forget we already do steam ready-meals in plastic containers with an auto-venting lid.
So here ends my story for today. Watch the developments in solar thin film as a new energy source for self-heating or self-cooling technology and watch the developments of self-steaming containers for ready-meals and other solid food products.