Global cooling

The US Environmental Protection Agency (EPA) is getting serious about the phase-out of greenhouse gases that contribute to climate change, especially so-called hydrofluorocarbons (HFCs).

Last month, the Agency finalised a rule that will reduce greenhouse gas emissions by up to 64 million tonnes over the coming decade, with a special focus on HFCs and HFC-containing blends that are used in retail food refrigeration, foam blowing and commercial vehicle air conditioning – putting the refrigeration technology industry under more pressure than ever to make mobile cooling more sustainable.

“[The EPA’s] action delivers on the President’s Climate Action Plan and the administration’s commitment to acting on climate,” EPA Administrator Gina McCarthy commented on the Agency’s globally publicised foray. “This rule will not only reduce harmful greenhouse gas emissions, but also encourage greater use and development of next generation … HFC alternatives.”

But it’s not just President Obama’s new Climate Action Plan that is pushing the issue to the top of the agenda. The UK Carbon Trust is equally insistent on acting quickly, stating in March that global demand for cooling could grow to three times the current UK electricity capacity by 2030 – mainly due to the world’s expanding population and a growing middle class demographic in emerging markets like China and India.

“It is estimated that up to half of the perishable food in developing countries rots before ever reaching the market, largely due to the absence of cold chains,” says Professor Richard Williams, Head of Engineering and Physical Sciences at the University of Birmingham – adding the combined food wastage would occupy a land area the size of Mexico, consumes 250 km3 of water per year, and accounts for up to 3.3 billion tonnes of global carbon production.

As a result, the race for developing climate neutral transport technology that will be able to stop food wastage without harming the environment is now well and truly on, with global market research company Research and Markets anticipating a Compound Annual Growth Rate (CAGR) of 17.95 per cent between 2014 and 2019.

The majority of that growth is said to come from progress in the mobile fridge market. According to the Birmingham Energy Institute, traditional transport refrigeration units (TRU) are disproportionately polluting, as the typically unregulated diesel powered auxiliary engines they use can emit up to 29 times more potentially carcinogenic particulate matter than a modern Euro VI diesel truck engine.

With political pressure rising by the day and environmentally friendly technology becoming increasingly viable, some of the leading businesses in mobile refrigeration are now frantically trying to take the lead in next generation cooling technology. Globally renowned brands Carrier and Thermo King, for example, have both dedicated substantial resources to exploring just how they can help catalyse change and protect stratospheric ozone.

The first action point for both will be implementing a more suitable chemical that is less aggressive on the environment. Breaking down a typical TRU, there are two main elements that have a hand in creating harmful emissions – one being the power source itself, and the other being the refrigerant. As one of the most widely used refrigeration cycles for mobile technology is vapour-compression refrigeration, in which a refrigerant undergoes phase changes between gaseous and liquid states to produce cold, the chemical choice is key to meeting the new EPA standard.

While many different gases can be used to produce cold, the one used in most systems today is a synthetic refrigerant known as R-404a, which has a Global Warming Potential (GWP) of 3,920 – meaning it releases the equivalent of 3,290 times the global warming impact of a single kilogram of carbon dioxide. With the new EPA ruling, R-404a use will be forbidden from 2020, prompting companies like Carrier and Thermo King to move on to a substance called R-452a, which claims a much-reduced GWP of 960 – around 45 per cent less than that of what is commonly used today.

“R-425a is non-toxic, non-flammable and significantly better for the environment, with a greatly reduced carbon footprint,” says Kelly Geddes of Carrier Australia – a vast country where efficient refrigeration technology is vital to maintain a stable cold chain.

But according to Geddes, swapping a very harmful chemical for one that is less harmful is only one step to leading transport refrigeration into the future. He says that further down the track, trailer refrigeration equipment will use completely natural refrigerants with a vastly reduced GWP rating. “Carrier, for one, is currently evaluating new technology that is a completely self-sustaining system, using a thermo-chemical reaction in a loop with a natural refrigerant to produce cold.”

In fact, Carrier has already shown a prototype of the system at last year’s IAA Commercial Vehicles Show in Hanover, Germany, with carbon dioxide R744 used as the refrigerant – marking what Geddes says is an ‘important milestone’ in the development of over-the-road refrigeration. The much talked-about prototype stood out for using a refrigerant with a GWP of just one – an enormous reduction from R404a’s rating of 3,920.

The reason why companies like Carrier are not jumping straight to the R744 solution is affordability, says Geddes. For now, the classic vapour-compression technology is still too price-competitive to make carbon dioxide a serious alternative, but work is underway to even the playing field in the near future.

Until then, there is still one TRU element left that will need consideration to achieve a green refrigeration solution – the power source. According to research by the California Environmental Protection Agency’s Air Resources Board, one of the most promising engine technologies at the moment lies in hydrogen fuel cells. Considered a clean energy source, fuel cells generate electrical power by driving chemical reactions using hydrogen and air – resulting in a quiet and efficient process that, unlike a diesel or electric engine, produces no pollution. The only by-products are water and heat.

The US Department of Energy (DOE) has been working on developing a fuel cell based refrigeration unit since 2013, but a commercial application has not been achieved just yet. For now, all that Kriston Brooks, who has been overseeing and evaluating the project on behalf of the DOE’s Pacific Northwest National Laboratory, can say is that fuel cells can “potentially provide a clean, quiet and efficient alternative by powering the electric motor [on a fridge unit].”

However, work is now underway to make the young technology more viable for mass applications in trucking – two North American fuel cell manufacturers, Nuvera and Plug Power, recently received $650,000 ach from the DOE’s Office of Energy Efficiency and Renewable Energy to work with Carrier and Thermo King on getting it production ready.

Nuvera will be working with Thermo King to develop a fuel cell based refrigeration unit using the company’s Orion fuel cell stack, while Plug Power is linked with Carrier and a company called Air Products to equip trucks on Long Island with its GenDrive product. Even though Nuvera’s recent acquisition by Nacco Industries has postponed the Thermo King project somewhat, Kriston Brooks is expecting ‘real world’ demonstrations as early as mid-2016.

In the meantime, the race will continue on the other side of the world in London, with engine technology start-up Dearman developing a piston engine transport refrigeration system that uses liquid nitrogen as a source of both emission free power and cooling. The engine uses the same vapour compression process that refrigerants undergo, but the emphasised phase changes instead drive a piston engine. The liquid form of nitrogen expands about 700 times in volume when it boils into a gas, which occurs when it is introduced to ambient heat. The process also exhausts a lot of cold, providing what Dearman calls ‘free refrigeration’.

“Utilisation of liquid nitrogen for both refrigeration and power is an exciting concept, especially for transport applications. The technology can provide not only potential savings in fuel consumption and emissions, but also better cold chain temperature control and stability,” says Jon Trembley, COE Lead Cryogenic Applications at Air Products, a company collaborating with Dearman on projects that have received millions in government grants to ensure the UK will be part of the expected cold chain boom in the developing world.

In fact, Dearman CEO, Professor Toby Peters. has already been in talks with India’s National Centre for Cold Chain Development (NCCCD) to create an environmentally friendly solution to India’s growing need for cold technology – saying there is a huge growth in middle classes in India and Asia and their lifestyles are going to be built on cold chain distribution.

Back in the UK, Dearman is now working on ways to replace the liquid nitrogen with liquid air, as both share many of the same properties and therefore work in much the same way. In June this year, the company opened a dedicated R&D facility to focus purely on liquid air engine design – and preliminary results are “more than promising.”

Reportedly, initial research has shown that using Dearman power for a 40’ refrigerated trailer would repay its investment within three months – meaning commercial viability of the concept is almost within reach. However, there is no guarantee that liquid air will actually progress to mass deployment, according to a 2013 paper by the University of Birmingham’s Centre for Low Carbon Futures*.

Despite growing awareness of liquid air’s technical and industrial advantages, the paper warned that the move from the demonstration to the commercialisation phase could still see the project fail. Dearman CEO Peters is less pessimistic about making the leap and already busy pushing ahead the liquid nitrogen solution for the Indian market – hoping it will give the liquid air project a much needed boost. “We are looking at 1,000 to 1,500 engines in those countries by 2017, and to be in manufacturing, producing 10,000 a year by 2018,” he says. “By 2019, we will be looking at manufacturing, and assembly with partners in those markets.”

Regardless of which technology will eventually succeed, with a variety of environmentally friendly alternatives on the boil and legislation closing in on industry, the refrigerated transport market is now right on track to making the next evolutionary leap.

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