The role of SMA technology in the fight against climate change
Written by Dr. Kevin O’Toole, Managing Director and Co-founder of Exergyn
Shape memory alloys (SMAs) are a unique group of metals which have the potential to revolutionise the heating, cooling and air conditioning (HVAC) sector and more. The global HVAC sector is a multi-billion euro industry, which is growing annually by over 5 percent. However it currently has a big problem: traditional HVAC systems, such as your home air conditioning system, utilise special gases called ‘refrigerants’ to perform the heating and cooling work. Whilst these refrigerants are very efficient, they also come with a downside, namely their highly detrimental impact on the environment. The Rocky Mountain Institute, a thought leader in climate change policy, has identified refrigerant management as the number one problem which industry as a whole must address if we wish to arrest or reverse the global warming pattern [1].
To give some context; an indexing system measuring the global warming potential (GWP) of a refrigerant gas is used to classify and rank their impact on the environment. A GWP of 1, for example, equates to a single molecule of the refrigerant having the same impact as a single molecule of the already vilified CO2 molecule if released into the atmosphere. These refrigerants are gases, and their leakage either while being in use, or at end of life, is common and unstoppable. This is why your car needs to have its refrigerant topped up every so often, because it escapes into the atmosphere. It may surprise you to hear that almost all of the common refrigerants in use today have GWPs in the thousands! The workhorse of industry and air-conditioning is a refrigerant which goes by the name of ‘R134a’. This has a GWP of 1430. So, in effect it is one thousand four hundred and thirty times more potent than CO2 when released into the atmosphere. This is a major problem for the industry.
Luckily, government bodies and regulators are aware of these issues. Today’s current batch of refrigerants are what we call HFCs and their GWPs range from the high hundreds to over 9000 in some cases. These came after CFCs, famously known for causing a hole in the ozone back in the 1980’s and 1990’s until their regulated removal. The GWPs of CFCs were in the tens of thousands. Regulators have laid out a roadmap over the next 10-15 years where the world will transition to the new generation of lower GWP refrigerants mostly made up of HFOs [2]. HFOs have a lower GWP (however they are still in the 10’s and 100’s), but come with the added penalty of increased toxicity, explosivity, lower efficiencies, or a combination of all three. Regulators have a tough decision as they either must choose between allowing people to live comfortable lives in air-conditioned spaces in an increasingly warm world, or potentially causing irreversible damage to the environment in the longer term, which in turn requires more cooling. It’s an impossible situation.
Working in conjunction with our global HVAC partner, we have proven that SMA can match the performance of R134a as a HVAC material, and that viable alternative HVAC systems can be developed using SMA. Currently we have a 50kW demonstrator unit in operation. For reference, a 50kW system is large enough to provide heating and/or cooling to up to 20 standard 2-bed apartments. Crucially, SMA based systems have zero GWP, meaning they have no detrimental impact on the environment. They also offer other advantages such as silent, safe operation. They are non-toxic and non-flammable. Rudimentary calculations show that if all of the refrigerants in the world’s HVAC systems were replaced by SMA, we could knock up to 1oC off global temperatures. In a world where we are trying to limit temperature rises to less than 2oC as a best case scenario, this is huge!
Using SMA for heating and cooling provides regulators with the ideal solution to their dilemma, one that allows for comfortable living combined, with efficiencies (and therefore costs) in line with current systems, and with zero environmental impact. We haven’t even considered the possibilities for the technology in other related fields such as automotive, aerospace and power generation, all of which are suffering from similar environmental issues. The opportunities are numerous.
SMA’s themselves are a super interesting technology. They are metal alloys primarily made of Nickel and Titanium and which exhibit two distinct states – one called Martensite and the other, Austenite. From the outside both states look the same, but at a micro level, they are almost like two different metals. By applying and releasing an external load onto the material, we can force the material to cycle between these states. This causes the cyclical release or absorption of a huge amount of heat, which in turn results in a heating or cooling effect. So, in a lot of ways, they do what refrigerants do, only SMA does it as a solid, leak-free, zero GWP, clean material.
We haven’t even scratched the surface of what’s possible with SMA yet. In many ways, the world of SMA is akin to the wild west. There are some well understood SMA blends, but there are many many more awaiting discovery. Our current systems and predictions of future performance are based solely on the few well understood blends available to us today. These already compete with the best performing refrigerant based systems today. However, who is to say that these are the most optimum blends? A minor change, for example, in the ratios of the metals in the SMA can have a profound impact on its behaviour. Our teams are actively scanning the blend landscape everyday, in doing so they are peering into the future. New blends are emerging all the time with unique advantages which can be retrofitted into the existing design, causing an uptick in efficiency.
Our goal is to inspire industry to choose the cleaner, more environmentally friendly SMA option – not because they feel they must, but because it makes the most business sense to do so. My feeling is that this logical appeal to the pockets of global businesses, coupled with regulators realising they have options, will drive a cleaner environment as a by-product of its adoption. It’s a win-win for everyone.
[1] https://www.drawdown.org/solutions/refrigerant-management/technical-summary
[2] https://www.icscoolenergy.com/guide-to-f-gas-regulation-and-the-hfc-phase-down/
