As charge is stored, an electrocaloric material will heat up

Friday, November 17th, 2023

Heat pumps — refrigerators, air conditioners, heaters — consume 30 percent of the world’s electricity, but capacitor-based heat pumps could “pump” more efficiently:

Compressing a gas will heat it up while lowering the pressure cools it down. However, various other materials undergo similar heating and cooling in response to other external influences, including physical stress, magnetic fields, or electric fields. In many cases, these materials remain solid despite experiencing significant changes in temperature, which could potentially simplify the supporting equipment needed for heating and cooling.

In the new work, done by researchers mostly based in Luxembourg, the researchers focused on materials that change temperature in response to electric fields, generically known as electrocalorics. While a variety of configurations have been tested for these materials, researchers have settled on a layered capacitor structure, with the electric field of the material changing as more charge is stored within it. As charge is stored, an electrocaloric material will heat up. When the charge is drained, they’ll draw in heat from the environment.

This has a significant advantage regarding the power needed for the device to operate since the current generated when draining the capacitor can just be used to power something. There’s a little energy lost during the round-trip in and out of storage, but that can potentially be limited to less than one percent.

The thing that uses power is the fact that the capacitors are entirely solid-state—on their own, they’ll just sit in either the source or sink environment. So, you either have to expend energy to physically move the device between the environments or transfer heat from the electrocaloric device to some other material that does the moving. In this case, the researchers simply exchanged heat with the source and sink by pumping a liquid through the electrocaloric material.

For the electrocaloric device, the researchers created a multilayer capacitor using a lead/scandium/tantalum oxide material. This was crafted into a series of parallel plates with gaps in between them, which allowed fluid to flow through the device.

The hardware worked by adding charge to the capacitor, which would heat the fluid in its immediate vicinity. That fluid would then be pumped to exchange heat with one environment, warming it up. While that was happening, the charge was drained from the device, cooling the fresh fluid that had been pumped into place. That cooled fluid was then pumped out to exchange heat with a separate environment, allowing the cycle to be repeated. Over time, this would gradually cool the first environment while heating the second.

And it worked. Heat was effectively transferred between the two environments, and measurements suggested that the device itself was capable of changing temperature by as much as 21° C. That’s a 50 percent improvement over the best electrocaloric device previously demonstrated. The cooling power is the equivalent of 5.6 watts, which works out to be about 116 W/kg of material.

It was also quite stable. The researchers built up a voltage difference of 400 V across the capacitor without any sign of breakdown, and performance remained steady across 100,000 cycles tested for this publication. Based on accelerated aging tests, the researchers estimate that one of these devices would last over 30 years in typical conditions.

The researchers also calculated its Carnot efficiency. This was higher for tests where the total temperature difference was relatively small. Assuming the power stored in the capacitor was put to use, the hardware can reach 64 percent of the maximum theoretical efficiency, which is considerably higher than any previous electrocaloric device.


  1. Jim says:

    This is very cool, but I think that we should wield the all-encompassing modern regulatory state to make our heat pumps 100x less efficient so as to accelerate the development of sustainable energy (nuclear is the only sustainable energy) and force the global warming of our planet so that growing times lengthen, forests expand, glaciers recede, San Francisco drowns, and the ice and snow blanketing Antarctica melt away to reveal Atlantic artifacts of impossibly ancient origin and strange technologies beyond comprehension.

    Fortunately, nothing is beyond our reach.

  2. Bomag says:

    ”accelerate the development of sustainable energy”

    Yeah; the ethos of our time is encapsulated by the adage: “To save the village, we had to burn it down.” Fossil fuels now suck, according to the Narrative, so its infrastructure and products all have to go.

    And the whole throw-away society plan. I spend my days driving to a big box store; loading up on the latest fashions; on the way home, the chip in my head reveals a multitude of new and improved products I must buy; so I swing by the landfill; dump my now obsolete stuff; go back to the store to make my life even better.

    I guess it all ends when the landfills are full.

  3. Freddo says:

    Dear Bomag, you are stuck in the old paradigm. Please get with the time and start consuming digital product.

    Get fed the outrage of the day, update your hashtags accordingly to show you believe and you care. Watch digital content, spend additional money on day-one content and DLC. Never notice that the news and series about the war in Oceania have been scrubbed by the AI and replaced by new content. Celebrate early cozy time online as your smart heating turns off early to save the planet.

  4. Jim says:

    That’s an astute observation, Freddo.

    Indeed that was the old paradigm: stay in school, don’t do drugs, go to college, get a middle-class office job by accident, buy a house, mail-order endless medium-quality imported manufactures, “invest” in your “401K”, retire, have a pension, suckle at the teat of Social Security Administration, abuse aspirin and Bengay until eventual expiration, etc.

    The new paradigm, as you suggest, is somewhat different: stay in school, use doctor-approved amphetamines and other drugs, go to something calling itself “university”, graduate with a mountain of nonbankruptable debt, barely get any office job if you’re lucky (maybe), don’t buy anything because you can’t afford anything, eat the bugs, live in the pod, accept the microchip, be assigned to the fifteen-minute city, etc.

    The old paradigm was skewered by Fight Club. The new paradigm they call Degrowth because the alternative was Shrinkage.

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