FEATURE ELECTRIC TRANSPORT


On land, sea and in the sky: the future for electric transport


Growing public concern for greenhouse gas


emissions is just one reason for the shift towards electrification. But with global electric car sales growing, can we also electrify transport in the marine, aerospace and defence industries?


Ben Smye, head of growth at online materials search engine Matmatch, comments


T


ransport makes up 14% of global emissions. In addition to road vehicles, military activity


is the most oil-exhaustive activity on the planet, with the US Air Force (USAF) being the single largest consumer of jet fuel in the world. The B-52 Stratofortress, for example, is


one of the USAF’s strategic bomber planes. With eight turbojet engines, this guzzles 500 gallons of fuel per minute – in just ten minutes of flight, it uses as much fuel as the average driver does on the road in one year. As a result, mechanical and design engineers


are looking to make a fundamental change in the way we power the various transportation methods around us.


ELECTRIFICATION Electrification offers a more sustainable means of powering a system, but is it powerful enough to operate a naval vessel or an aviation system? Firstly, the requirements for electrical motors


in aircraft or seagoing vessels compared to electric vehicles significantly differ. These modes of transportation must withstand extreme conditions and require a greater power to weight ratio from electric motors. While conventional electric motors – which are traditionally composed of copper, iron and permanent magnets – may be suffice for electric cars, they will not be enough to get an aircraft off the runway. Design engineers therefore need to develop


electric motors which generate greater thrust per unit weight – and, for this, high- temperature superconductors (HTS) are a key enabling technology. HTS materials lose their electrical resistance below a superconducting transition temperature and are making high power, low weight, motors possible as a result. For conventional superconductors, the


transition temperature is usually so low that the superconductor needs to be cooled using liquid helium at around 4 Kelvin (-269˚C). HTS, however, can operate at comparatively high temperatures and be cooled by the cheap and abundant coolant, liquid nitrogen, which boils at 77 Kelvin (-169˚C).


12 AUTUMN 2020 | ENERGY MANAGEMENT It’s for this reason that at Matmatch we are


seeing companies working to further decrease the cost of manufacturing HTS, with the aim of making the price comparable to copper.


ALL AT SEA Being able to electrify naval vessels could mean new shipping routes that allow for expansion into one of the least explored parts of the Earth – the Arctic. To do this, however, the vessels need to have efficient subsystems and propulsion systems capable of travelling long distances. So, how can HTS help achieve this? While electric ship propulsion has been around


since the 19th century, it has traditionally been limited to small vessels. HTS wire, however, can conduct the same current as a copper cable in about one tenth of the cross section. So, when used to replace copper windings and permanent magnets, HTS wire can provide a huge weight reduction and can create a higher, more intense, magnetic field. This allows for much more compact, higher power, electrical motors. For naval vessels, HTS are also being


implemented in degaussing coil systems. The system encircles the vessel with superconducting cables that can neutralise the ship’s magnetic signature and reduce the chances of the vessel being detected by enemy ships, submarines or magnetically activated mines. For these types of electronic and magnetic


applications, companies tend to use copper or silver. C110, for example, which features 99.9% of copper content and is the purest grade of oxygen-free copper, offers the highest electrical and thermal conductivity values available from a commercially available copper alloy and is not susceptible to embrittlement when hardened. C110 also has high ductility and is readily cold worked, making it suitable for electronics in naval vessels and other marine applications. Replacing copper in motors and cables in


seagoing vessels with HTS can help significantly increase the distance that ships can travel, reduce the journey time, reduce risk of detection, minimise the amount of energy


used by the marine sector and allow them to travel for longer distances.


UP IN THE SKY Similarly, the aviation industry can greatly benefit from the electrification of aircraft. One of the biggest challenges for aerospace engineers is being able to lighten the overall load of the aircraft without jeopardising its output. To tackle this issue, engineers can replace the copper cables that are traditionally used in the aeroplane’s motor with HTS cables. In fact, with NASA’s NX-3 aircraft, the plane


is designed to use several superconducting electric motors to drive its distributed fans, which in turn lowers the fuel burn and emissions. The aircraft also makes use of HTS cables to distribute power from a superconducting generator to the motors. In addition to offering greater benefits for


the environment, electrical propulsion means quieter aircraft. During an operation, air forces can hold an advantage over the enemy by reducing the probability of detection.


LOOKING TO THE FUTURE Whether it’s electric propulsion or power distribution in an aircraft or sea vessel, HTS can offer greater power per kilogram, lower noise and reduced emissions compared to conventional electric motors. Despite the advantages, the adoption of


HTS in propulsion has many hurdles to overcome and this is down to the complexities of the technology and the associated developmental costs. But, we will undoubtedly see the next


generation of cleaner and quieter military aircraft and vessels using this technology in the years to come. It is expected to become increasingly more popular as the price of manufacturing HTS becomes comparable to copper, making electrification a viable option for aerospace and defence companies.


Matmatch www.matmatch.com


/ ENERGYMANAGEMENT


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