Refrigerants have been one of the most defining features of our modern-day technological world. It is because of refrigerants that we can preserve food, transport it from one place to another, and make perishable items useful for consumption over a longer period.
The market of refrigerant products is growing and will continue to grow, according to market estimates. Available data says that the total value of refrigerant products worldwide was 20.05 billion US dollars in 2022, and it could go up to 36.77 billion US dollars by 2030, more than 1.8 times in eight years.
However, the growth in the refrigerant market does not suggest that the industry is becoming stagnant. In fact, increasing sales and market expansion do not preclude innovation. Instead, this growth often drives the development of new technologies and approaches. A recent research effort led by the Department of Energy’s Oak Ridge National Laboratory has led to a new scientific understanding that could help achieve solid-state cooling.
In the next segments, we will dive deeper into understanding this phenomenon better.
The Transformative Paradigm of Solid-State Cooling
The primary achievement of the team of researchers has been bridging the knowledge gap in the science of atomic-scale heat motion. At a more functional level, the success of the research rests on a deeper understanding of materials and devices.
The material, in this case, is a nickel-cobalt-manganese-indium magnetic shape-memory alloy that can be deformed and then returned to its original shape by driving it through a phase transition either by increasing temperature or by applying a magnetic field.
The device, on the other hand, comprises a suite of neutron-scattering instruments that can examine a material at the atomic scale.
How the Material Emerged as an Optimal Candidate for Solid-State Cooling
The experiment showed that nickel-cobalt-manganese-indium magnetic shape-memory alloy could be driven through a phase transition by increasing temperature or applying a magnetic field.
When subjected to a magnetic field, the material underwent a structural and magnetic phase transition: it absorbed and released heat, in simpler terms. This effect is core to the phenomenon of solid-state cooling. In other words, solid-state cooling harnesses this effect to provide refrigeration.
In this cooling mechanism, the material attains what is known as the ferroic glassy state, which enhances its ability to store and release heat.
While elaborating on the science behind the experiment, Michael Manley, senior researcher in the Neutron and X-ray scattering group at ORNL, said the following:
“Neutron scattering shows that the cooling capacity of the magnetic shape-memory alloy is tripled by the heat contained within these local magnon-phonon hybrid modes that form because of the disorder in the system. This finding reveals a path to make better materials for solid-state cooling applications for societal needs.”
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The Magnon-Phonon Hybrid Modes
The magnons and phonons are alternatively known as the spin waves and vibrations. They exist as a couple in the material in synchronized dance forms in small regions distributed across the disordered arrangement of atoms. The regional behavioral pattern of the magnon-phonon hybrid modes has crucial implications for a material’s thermal properties.
Explaining the implications of these hybrid modes and their movements, Manley further said:
“Long- and short-range interactions manifest as localized vibrations and spin waves, which means they’re getting trapped in small regions. This is important because these extra localized vibrational states store heat. Changing the magnetic field triggers another phase transition in which this heat is released.”
Altogether, the experiment opened up a new frontier in solid-state cooling research by showing that the proper control of functions of the magnetic-shape memory alloy can lead it to become a heat sponge and prepare it for efficient solid-state cooling without the need for traditional refrigerants or mechanical components.
While this research is definitely a breakthrough, one must always remember that solid-state cooling is not a recent phenomenon. Theoretically, the phenomenon has existed since 1834, when French physicist Jean Charles Athanase Peltier discovered the Peltier effect.
In the coming segment, we briefly look into the phenomenon of the Peltier Effect and Thermoelectric Coolers that leverage the Peltier effect.
The Genesis of Solid State Cooling and Thermoelectric Coolers
Scientifically, the Peltier effect is defined as the “phenomenon in which a conductor, maintained at a constant temperature and with an electric current flowing through it, experiences the generation of a thermal current. This thermal current helps to carry away the heat produced by the electric current.”
In other words, the Peltier effect emerges from a situation where the electrical current flowing through the junction connecting two materials emits or absorbs heat per unit of time at the junction to balance the difference in the chemical potential of the two materials. T
The Peltier effect helps formulate an electronic refrigerator known as a Peltier cooler. The Peltier devices are also known as Thermoelectric coolers that consist of an array of semiconductor materials, composed of bismuth telluride, connected in series and sandwiched between two ceramic plates.
With direct current passed through a TEC, electrons in the semiconductor material move from the hot side to the cold side, carrying heat with them and causing one side of the device to cool down while the other side heats up.
The reason why the scientific community is still deliberating on the phenomenon of solid-state cooling and is interested in exploring it is because it has many benefits and real-life applications. We will look into these advantages and applications in the segments to come.
The Many Benefits and Applications of Solid-State Cooling
Solid-state cooling could become more energy efficient than conventional refrigeration systems as they are capable of converting a higher percentage of electrical energy into cooling power.
They are also more integration-compatible when it comes to renewable energy sources, including solar panels. Apart from having a low carbon footprint, solid-state cooling does not contribute to ozone depletion and is, therefore, more environmentally friendly than refrigerant or other fluid-based cooling technologies.
Solid-state cooling also scores high in the aspects of reliability and durability. Since they consist of no moving parts or circulating fluids, they experience mechanical failure less and require less maintenance. Many consumer appliances can leverage the technology of solid-state cooling.
Some such appliance instances include refrigerators, air conditioners, or wine coolers. There is increasing deliberation on how to use solid-state cooling in electric and hybrid vehicles to cool batteries and other components. It could contribute to enhanced performance and increased range.
A solid-state cooling mechanism is also deemed fit as an alternative cabin cooling system in modern vehicles. A scientific study looked into the feasibility of an automotive air conditioning system in automobiles that would utilize solid-state cooling. Results showed that applying small and flexible TE cooling devices provided more possibilities for an efficient automotive air conditioning system.
The study also investigated the velocity and temperature profiles of the localized TE cooling built for better human comfort by providing uniform air flow in the cabin. An estimated improvement of almost 9% was obtained when this arrangement was compared with the conventional refrigeration system regarding human comfort.
Many benefits and applications of solid-state cooling have inspired companies to invest research and resources in solid-state cooling techniques and methods.
In the segments to follow, we will discuss some such companies and their specific solutions.
#1. CUI Devices
CUI Devices is known for its range of Peltier devices. It offers a portfolio of single-stage Peltier modules, multi-stage Peltier modules, and Peltier cooling units.
The CPM-2F 6.0 Amp Peltier cooling unit, for instance, comes with an enhanced seal structure for water resistance and thermal stress absorption. It can be installed easily and caters ideally to the needs of high-density, high-power industrial applications and refrigeration.
The company also has two more variants, CPM-2C and CPM-2H, offering optimal services at the scale of 7 and 8.5 Amp, respectively.
If we look at the overall product profile of CUI Devices in this space, it carries a range of single-stage and multi-stage Peltier modules as well as Peltier cooling units, ranging in size from 3.4 to 70 mm with profiles as low as 1.95 mm and current ratings from 0.7 to 20 A and temperature deltas from 70 up to 105°C. The company boasts of its products’ improved reliability, superior performance, and enhanced cycle life.
CUI Devices, headquartered in Tualatin, Oregon, United States, is an electronic components manufacturer offering interconnect, audio, thermal management, motion, and sensor solutions. In October 2023, the thermal management group of CUI Devices launched a thermal design service to identify potential hotspots, optimize airflow, and design effective cooling systems tailored to a customer’s specific needs.
#2. Coherent Corp
Coherent Corp’s cooling systems offer a range of industrial and telecom solutions, including a range of standard and customized formats, all built around a common “Core” based on efficient TEC devices. Apart from TEC devices, this core also integrates heat/cold sinks, thermistors/RTDs, and wiring harnesses.
One of Coherent’s most well-known solid-state cooling technology products includes Climatherm (CTA) air-to-air cooling systems. Based on the company’s solid-state TEC cooling technology, the solution protects customer electronics from extreme conditions with up to 250 W of cooling power in a lightweight, compact package.
The product’s coolers feature a RoHS EU-compliant, compact, lightweight design and deliver highly efficient heat transfer. Typical applications include electronic enclosure cooling, food and beverage storage, battery cabinet cooling, and laboratory instruments.
According to the latest available financial records, the company registered an annual revenue of US$5.16 billion for the year ending on June 30, 2023. It was a significant increase from the previous year’s record of US$3.317 billion for the year ended on June 30, 2022.
The Future of Solid-State Cooling
To put it mildly, the future of solid-state cooling looks promising beyond doubt. The scientific and commercial technology communities across the globe have realized its potential as something that could take the challenges of global warming and climate change head-on.
Apart from the experienced and established names, innovative companies like Phononic have emerged. Their solid-state cooling, refrigeration, and HVAC innovation use just water mixed with naturally available CO2, with a GWP of just 1, delivering the lowest GWP rating in the industry. Here, GWP stands for Global Warming Potential.
Phononic believes that its solid-state design has the potential to represent an exciting new way of reducing greenhouse gas emissions, supporting UN climate goals, and meeting the market’s demanding performance needs.
However, there are some challenges that Solid-State Cooling will have to address in order to efficiently meet thermal needs in electronics in the future. It has to become affordable, as the cost of thermoelectric materials could be notably higher compared to traditional cooling systems. The researchers will have to work more aggressively and expeditiously in exploring alternative materials and more cost-effective manufacturing processes to solve this challenge.
Scaling up production with solid-state cooling at the core will also face an efficiency challenge as thermoelectric materials still lag behind traditional vapor-compression systems in certain applications. Scientists will have to conduct more vigorous testing to discover ways to enhance the efficiency of thermoelectric materials.
Finally, solid-state cooling systems will have to improve their thermal management profiles so that they can efficiently dissipate the heat generated on the hot side of the thermoelectric cooler. This is crucial for maintaining the system’s optimal performance.
Globally, researchers have realized the benefits of solid-state cooling. They are investigating new materials and performance-improving techniques. Hopefully, we will soon see greater adoption of solid-state cooling in industrial and commercial use cases.
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