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First Liquid-Heat Engine Can Upcycle 70% of the World’s Waste Heat Into Clean Energy

Luminescent’s circular solution uses isothermal processes to capture and store waste heat, transforming a previously inaccessible resource into zero-waste power.

As the world battles rising inflation, a cost-of-living crisis, climate change and more, it’s clear that the fossil-fueled status quo is not working. Fossil fuels may have seemed like the crutch we could depend on, allowing us to build, develop and evolve; however, the reality is that they are now causing the world to burn, inflate and divide.

Fossil fuels currently account for an estimated 81 percent of global energy production, with a mere 13 percent generated by renewables. By 2050, it is estimated that 90 percent of the world’s electricity must be derived from renewable energy in order to ensure human sustainability. As harnessing renewable energy sources gains traction, scientific minds and bold innovators are searching for ways to tap into the unlimited amount of energy available without the heavy environmental cost.

Israeli startup Luminescent is one such innovator breaking new ground in renewable power. The company has developed the world’s first liquid-based, isothermal heat engine that can upcycle waste heat — heat released as a by-product of any industrial, thermal or mechanical process — efficiently and affordably. Globally, an estimated 70 percent of the world's energy is waste heat; and it has the potential to generate hundreds of gigawatts of zero-emission energy. The problem is that typical waste-heat projects are under 7 Megawatts and are uneconomical, with simple payback longer than seven years. Luminescent has found a way to turn this previously impractical renewable resource into zero-emission energy whilst doubling efficiency and halving costs, without the use of rare minerals.

External heat engines (non-internal combustion) used today operate adiabatically — meaning they do not allow for heat transfer, using gases or vapors. This limitation — together with the poor thermal density of gases per volume — leads to the engines being large in size, expensive and inefficient, with engines smaller than 10 megawatts; and any energy generated inaccessible to the majority of power grids and generators. In contrast, Luminescent’s engines allow for liquid heat transfer via isothermal expansion of air bubbles — meaning the temperature within the engine remains the same, despite the changes in volume and pressure.

“Our engine is the first engine that is based on liquid and is isothermal. Because of these two parameters, we can achieve a third of the cost compared to other existing technologies. And because of that, we can have between two to three years of simple payback,” Doron Tamir, co-founder and CEO of Luminescent, explains to Sustainable Brands® (SB).

Luminescent’s breakthrough of enabled heat transfer is a result of its innovative nozzle, which is integrated into the engine’s design. The nozzle allows for heat-transfer liquid (for example, hot water, hot oil, hot molten salt) — which has larger orders of magnitude of thermal energy per volume than any gases — to be mixed with pressurized air bubbles, which expand isothermally for kinetic energy transfer.

“Whilst the liquid is in the nozzle, we inject air bubbles, nitrogen bubbles or vapor bubbles; these gases expand whilst suspended in the liquid because they attract the heat from the surrounding liquid, maintaining the temperature gap,” Carmel Rotschild, associate professor at Israel Institute of Technology and co-founder and CTO of Luminescent, told SB. “That’s it — the nozzle is designed in such a way that when the bubbles expand, the liquid accelerates to maintain fluid and its position which generates thrust.”

The process converts the heat and initial pressure inside the nozzle into kinetic energy.

“Generating electricity from kinetic energy of liquids is extremely simple — similar to every hydroelectric system,” Rotschild explains.

Luminescent says its engines can store enough energy to power 600 average-sized homes for 20 hours, emit zero greenhouse gases, have 1,000 times more power density than conventional waste-heat plants/engines, and have a comparable reduction on CAPEX. Through the isothermal processes, the company has said it can transform any 100-550℃ heat source into energy, doubling the efficiency of operations and providing up to 70 percent more power than existing operations.

Luminescent is currently involved in two pilot schemes involving steam and gas pipelines — with industry players in mining, manufacturing and energy all eagerly awaiting the results. Luminescent has recently received $7 million seed round funding led by Grove Ventures’ General Partner Lior Handelsman, with participation from European climate-first VC Extantia Capital.

"Finding clean energy solutions is pertinent to global markets and our planet; and therefore we've decided to partner with Luminescent as they introduce their revolutionary isothermal heat engine that ingeniously upcycles previously untapped waste heat," Handelsman says.

Luminescent’s first commercial product rollout is set for later this year.

“In five years, we hope that we will be fully commercial in our first market of iron and steel companies; and start our second market, which is long-duration storage — we have a fantastic long-duration storage solution based on our engine. If we succeed in accessing these two markets, it will be amazing,” Tamir says.