The ubiquitous heating and cooling technology used today in everything from heat pumps to refrigerators and air conditioners – that make our lives more comfortable, safer and convenient – comes at a price because they fuel global warming.
Irish company Exergyn believes it has found an alternative approach.
Home life as we know it today would not be possible without heat pumps and refrigerators and the technology they are based on. Outside the home too, these essential systems work to keep our supermarket foods cool, preserve medicines and control the temperature of our energy-hungry data centres.
Most heating, ventilation, air conditioning and refrigeration technologies require the use of refrigerant gases – hydrofluorocarbons or hydrofluoroolefins. These gases, which have high global warming potential, often leak from equipment, driving further warming.
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Exergyn, based at Dublin City University’s innovation hub Alpha, has developed a technology it says eliminates the need for these refrigerant gases, replacing them with a metal alloy that provides a similar performance but without the damaging environmental costs.
“In simple terms, we use a metal instead of a refrigerant gas and that metal cycles between two internal states,” said Kevin O’Toole, cofounder of Exergyn and its chief technical officer.
“All we’re doing differently is that instead of using this gas, we’re using the shape memory alloy metal to do the heating and cooling work. And, fundamentally, the difference is that metals don’t leak. That lack of leaking prevents any of the issues with the environment because nothing is getting into the atmosphere.”
The refrigerants in heating, ventilation, air conditioning and refrigeration technologies are powerful drivers of global warming. For example, the most commonly used one is R134a, which has a global warming potential 1,540 times greater than CO2. This means each kilogram of R134a released in the atmosphere traps heat equivalent to 1,540kg of CO2.
The R134a refrigerants leak out into the atmosphere in the normal operation of pumps or refrigerators, resulting in a “blanketing effect” in the atmosphere, trapping more heat and intensifying global warming.
Legislation
In 2016, the European Union signed up to Kigali Amendment to the 1987 Montreal Protocol, a legally binding international agreement focused on phasing down the production and consumption of hydrofluorocarbons. Despite this, gas refrigerants from heating, ventilation, air conditioning and refrigeration technology are still leaking into the atmosphere and manufacturers are under pressure to find new technology that will comply with the amendment.
The newer hydrofluoroolefins have lower global warming potential than the hydrofluorocarbons but, on the downside, they degrade into persistent microplastics which are a serious risk to human health.
The EU is set to ratify the Kigali Amendment as new regulations under the Reach framework are set to come into force between now and 2027. This is creating a sense of urgency among heating, ventilation, air conditioning and refrigeration manufacturers as it means they must phase out use of the high global warming potential hydrofluorocarbon and hydrofluoroolefin technologies by the mid-2030s.
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The pressing need for less environmentally destructive heating, ventilation, air conditioning and refrigeration technologies has led to several natural refrigerants being tested, including propane, CO2 and ammonia. However, each of these has drawbacks such as flammability, a need for high pressure to work and toxicity as well as operational inefficiency.
“Propane has an A3 flammability rating which means it is quite explosive,” said O’Toole. “Carbon dioxide needs very high pressure to operate and that means the cost is very high and efficiency is very low. Then ammonia is poisonous; it smothers people.”
That has left the heating, ventilation, air conditioning and refrigeration industries facing a technological impasse and opens an opportunity for others, such as Exergyn, which says it can provide safer refrigerants, with zero leakage operating at high efficiency and in regulatory compliance.
Exergyn says its technology can break the dangerous positive feedback loop in operation at present which could lead to catastrophic climate outcomes, where gas refrigerant leakages amplify global warming, which in turn creates more demand for cooling systems, and leads to more refrigerant leakage.
Refrigerants
Exergyn was set up in 2012 and, from the start, its goal was to focus on energy recovery from low-grade waste heat from industrial processes. In 2016, following the Kigali Amendment, the company reframed its mission to directly tackle the issue of problematic refrigerant gases used in heating, ventilation, air conditioning and refrigeration systems.
The idea Exergyn came up with was to replace the gaseous refrigerants with a solid metal alloy, known as a shape memory alloy, which was made mostly from nickel and titanium. The alloy displays the electrocaloric effect, which means that as it is compressed or decompressed, it shifts between two solid states, austenite and martensite, absorbing or releasing heat as it does so.
“This means that instead of boiling a liquid refrigerant into gas, and back again, our technology mechanically cycles this metal, heating or cooling it without changing it into a gas or liquid,” said O’Toole. “Crucially, metals don’t leak like gases so this eliminates refrigerant leakages entirely,” he added.
When the metal is compressed, O’Toole said, it undergoes an internal phase transformation which releases heat. When it is released, after the load is removed, the metal reabsorbs heat by shifting back to its original phase.
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By compressing and decompressing strips or layers of the metal alloy inside a heat pump, the Exergyn system moves heat efficiently, whether that involves heating a building or cooling a data centre, without the use of a gas. As metals don’t leak, or degrade, there are no harmful emissions from this process.
Domestic heating accounts for a large part of Ireland’s carbon footprint and this will increase, as heat pumps grow in popularity in the coming years both for heating homes and cooling processes in industry. Data centres are also important. Ireland hosts a growing number of such centres, which have large cooling demands that are currently dependent on hydrofluorocarbons or hydrofluoroolefin-based systems.
Ireland’s future
Exergyn says its gas-free heat pump technology provides Ireland with a way to reduce future greenhouse gas emissions, both from reductions in the use of cooling refrigerants in heating, ventilation, air conditioning and refrigeration technologies and increased energy efficiency.
The company is currently experimenting with the use of advanced 3D metal printing techniques in partnership with DCU, and with Fort Wayne Metals in Castlebar, Co Mayo. The goal is to produce a range of bespoke metal alloys with enhanced heat transfer properties that can unlock energy efficiencies.
Though still a small company, with fewer than 50 employees, it has global ambitions. To realise its goals, it wants to avoid competing directly with big original equipment manufacturers, but rather to license its intellectual property in partnership with such established players.
Rather than compete directly with major equipment manufacturers, it plans to license its technology to industry partners.
Exergyn’s partnership with Carrier Global Corporation, a big operator in the heating, ventilation, air conditioning and refrigeration sector, has provided it with access to the scale and distribution networks necessary to reach millions of users. Exergyn provides it with a technology the group can integrate quickly to expand its market, offering cleaner, safer products that meet all regulations.
Meanwhile, a sister company called Nexeryn is exploring applications of the technology in the medical device sector where rapid heating and cooling methods are also needed, and for precision actuation systems in the aerospace industry and vibration dampening products for the automotive industry.
