{"id":13982,"date":"2021-03-31T14:58:20","date_gmt":"2021-03-31T21:58:20","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=13982"},"modified":"2021-03-31T14:58:20","modified_gmt":"2021-03-31T21:58:20","slug":"massless-batteries-for-aircraft","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/massless-batteries-for-aircraft\/","title":{"rendered":"Massless Batteries for Aircraft?"},"content":{"rendered":"

What if the weight of the batteries in an electric airplane could virtually disappear?\u00a0 Researchers at Chalmers University of Technology in Gothenburg, Sweden have come up with an improved structural battery that exceeds the results of earlier research<\/a>.\u00a0 So-called \u201cmassless batteries,\u201d although not as energy dense as cylindrical or pouch lithium-ion batteries, could be worthy substitutes.<\/p>\n

The idea of making airplanes from materials that would provide energy from their inherent properties has been of interest for years.\u00a0 Your editor wrote an article on \u201cThe Grand Unified Airplane\u201d for Kitplanes<\/em> magazine<\/a> in 2013 based on the idea of combining solar power, piezoelectric flexing of wings, and structural batteries.\u00a0 The ultimate goal was to create a machine that would move through the air on the energy of flight itself.\u00a0 This might seem an unreachable fantasy, but material scientists are bringing us closer to the dream.<\/p>\n

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Chalmers University points out, \u201cStructural battery composites cannot store as much energy as lithium-ion batteries, but have several characteristics that make them highly attractive for use in vehicles and other applications. When the battery becomes part of the load bearing structure, the mass of the battery essentially \u2018disappears\u2019\u201d.\u00a0 Illustration: Yen Strandqvist<\/p><\/div>\n

Headlining their report with a rather non-academic boast, Chalmers University promotes its, \u201cBig breakthrough for \u2019massless\u2019 energy storage.\u00a0 \u201dThey follow with an intriguing first paragraph.\u00a0 \u201cResearchers from Chalmers University of Technology have produced a structural battery that performs ten times better than all previous versions. It contains carbon fiber that serves simultaneously as an electrode, conductor, and load-bearing material. Their latest research breakthrough paves the way for essentially \u2019massless\u2019 energy storage in vehicles and other technology.\u201d<\/p>\n

Before getting too excited about that \u201c10 times\u201d claim, recognize that previous structural batteries did not display high energy densities, the property that keeps the Energizer Bunny hopping.\u00a0 Chalmers notes the new battery has an energy density of 24 Watt-hours per kilogram, only about 20 percent that of comparable lithium-ion batteries.\u00a0 It\u2019s slightly less than one-tenth that of the best battery packs used in state-of-the-art aerial vehicle.<\/p>\n

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Chalmers structural battery shows considerably higher strength, energy density than those of previous researchers<\/p><\/div>\n

Chalmers explains why this is not a total loss.\u00a0 \u201cBut since the weight of the vehicles can be greatly reduced, less energy will be required to drive an electric car, for example, and lower energy density also results in increased safety. And with a stiffness of 25 GPa (GigaPascals equaling 3,625,943 pounds per square inch), the structural battery can really compete with many other commonly used construction materials.\u201d\u00a0 Depending on the weight of composite materials used, the structure might be no weightier than a more conventional equivalent.<\/p>\n

Consider, though, a possible application of such energy-storing materials.\u00a0 Let\u2019s use the 24 kW\/hr materials applied to Calin Gologan\u2019s Solar Elektra One,<\/a> introduced in 2012.\u00a0 The plane was a 3\/3 machine, 1\/3 structure, 1\/3 batteries, and 1\/3 payload including pilot.\u00a0 Each third was 100 kilograms (220 pounds).\u00a0 Imagine being able to replace half the structure with Chalmers\u2019 structural battery material.\u00a0 50 kilograms (110 pounds of the airframe would be capable of storing 1,200 Watt-hours per kilogram, shaving 4.6 kilograms (10.1 pounds) from the battery weight.\u00a0 Not a big number, but still 1.5 percent of the total aircraft weight.\u00a0 Chalmers researchers predict up to three times the energy density for future products, so that would equal a 4.5 percent reduction.\u00a0 As on the Grand Unified Airplane concept, if those structural panels were also solar collectors, even more benefit could accrue in terms of extended range.<\/p>\n

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Calin Gologan’s PC Aero One, a 2012 design, light as it is, would benefit from structural batteries.\u00a0 Greater strength and energy density are coming, according to researchers<\/p><\/div>\n

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Chalmers\u2019 research is linked to earlier efforts by Emile Greenhalgh at Imperial College in London, who was affiliated with work at Volvo<\/a> to develop structural body panels that would store energy.\u00a0 Ongoing research was named by Physics World as one of 2018\u2019s ten biggest scientific breakthroughs.<\/p>\n

Leif Asp, Professor at Chalmers and leader of the project explains, \u201cPrevious attempts to make structural batteries have resulted in cells with either good mechanical properties, or good electrical properties. But here, using carbon fibre, we have succeeded in designing a structural battery with both competitive energy storage capacity and rigidity.\u201d<\/p>\n

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Doctor Johanna Xu with a newly manufactured structural battery cell in Chalmers\u2019 composite lab, which she shows to Leif Asp. The cell consists of a carbon fiber electrode and a lithium iron phosphate electrode separated by a fiberglass fabric, all impregnated with a structural battery electrolyte for combined mechanical and electrical function. Image: Marcus Folino<\/p><\/div>\n

The new battery has a negative electrode made of carbon fiber, a positive electrode made of a lithium iron phosphate-coated aluminum foil, separated by a fiberglass fabric, in an electrolyte matrix. \u00a0Researchers \u201cdid not choose the materials to try and break records \u2013 rather, they wanted to investigate and understand the effects of material architecture and separator thickness.\u201d<\/p>\n

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The samples of Chalmers structural batteries shows different materials used<\/p><\/div>\n

Further research financed by the Swedish National Space Agency will attempt to enhance the performance of the structural battery. \u00a0\u201cThe aluminum foil will be replaced with carbon fiber as a load-bearing material in the positive electrode, providing both increased stiffness and energy density. The fiberglass separator will be replaced with an ultra-thin variant, which will give a much greater effect \u2013 as well as faster charging cycles. The new project is expected to be completed within two years.\u201d<\/p>\n

Leif Asp, leading this project too, estimates that such a battery could reach an energy density of 75 Wh\/kg and a stiffness of 75 GPa (10877830 psi) \u2013 about as strong as aluminum, but at a much lower weight.\u00a0 He\u00a0takes an optimistic view.\u00a0 \u201cThe next generation structural battery has fantastic potential. If you look at consumer technology, it could be quite possible within a few years to manufacture smartphones, laptops or electric bicycles that weigh half as much as today and are much more compact.\u201d<\/p>\n

And in the longer term, it is absolutely conceivable that electric cars, electric planes and satellites will be designed with and powered by structural batteries.<\/p>\n