Think again about eVTOL aircraft charging systems based on electric car charging systems. Josh Portlock, chief technology officer of Electro, an Australian company that manufactures electric aircraft charging products, conveys this message.

In order to scale with global demand for electric aviation, Portlock said at the Vertical Aviation Safety Team (VAST) conference recently, we need high power standardized charging infrastructure. “Aviation charging is very different from automotive charging. Aircraft can’t drive right up to the charger like a car can, and they have wingspans to deal with. You need to move the charger and plug it into the aircraft because it’s likely out on the apron, with maybe half a dozen aircraft that might be in the way. You want to make sure that you can, as quickly as possible, start charging an aircraft.”

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A SYSTEM FOR CHARGING EVTOL VEHICLES

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In addition, aircraft will need more power, which means thicker, longer, and heavier charging cables, integrated cooling systems with MW capability, high voltages to the site, and the ability to bank power both from the grid and from solar panels on-site.

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It is also important that the industry continues to work on the standardization of charging hardware, including power plugs, so that these requirements can be met. It is estimated that there are more than half a dozen different DC fast-charging standards around the world, according to Portlock. “Now, that is fine if you are a Tesla [electric car] and you make millions of cars, employ hundreds of engineers, and can cater to all those different standards when you ship your cars around the world; but that isn’t so good if you are an aircraft manufacturer with an international market with a low volume. As a result, you want to make sure that the same aircraft can be charged in all parts of the world using the same standard. Obviously, the longer the range of [eVTOL] aircraft gets, the more likely it is that you will be able to fly between regions, between countries, without having to use adapters and carry additional charging hardware with you."

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A wheeled, portable, DC fast charger with dual ports, rather than AC/DC charging converters on the aircraft or AC couplers on power plugs, can easily be moved by one person up to the aircraft. The Rapid series DC chargers from Electro are available in power ranges of 30-80 kW and are compatible with SAE AS6968, which defines the design and minimum performance requirements for the connection set of conductive charging systems for electrically powered aircraft.

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Wi-Fi and Bluetooth connectivity allow for telemetry reporting and over-the-air software updates on the 80-kW charger. It is rated IP53 for resistance to water sprays and dust. The Comité Européen de Normalization Electrotechnique developed IP, or "International Protection," to rate the durability of electronic devices.

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By focusing on DC charging, Portlock says we eliminate the weight, cost, and complexity that come with plugging directly into an AC outlet. There are many adapters available in the automotive industry, but some of them are illegal and not recommended from a safety standpoint. If you don't have to carry around extra items in aviation, there's something I want to avoid."

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Electro developed the Electro Management System (EMS) concurrently with the chargers, which Portlock calls "the brain" of the charging system. This feature is on our latest smart chargers, which we sell to aircraft manufacturers for installation on the [aircraft instrument panel] or [charging] inlet, allowing [customers] to quickly adopt AS6968 and communicate with redundant battery pairs using their preferred battery management system.

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The EMS can be mounted on the outside of aircraft and serve as an inlet management system, which allows the [ground] charging crew to quickly assess whether the batteries are ready for the next mission. The EMS on the outside of the aircraft eliminates the need for human presence in the cockpit while charging, allowing ground crews to monitor the charge and decide when to finish. Pilots can concentrate on flying, ground crew can concentrate on charging, and the operation can be much more efficient." The EMS with the charger enables remote monitoring, billing, and maintenance, including over-the-air updates. Additionally, it allows charging to be started remotely.

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“If required, we can wake up the aircraft over the charger and start charging remotely,” Portlock said.

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Moreover, the company is developing 200- and 400-kW superchargers for large electric aircraft, but their use depends on the availability of enough electricity at the airport or vertiport. It is the energy systems that are the real bottleneck in the charging infrastructure. How will the energy be generated?” Portlock asked.

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POWERING THE GRID

A multi-pronged approach is needed, according to him. In airports, grid connectivity is often limited, so adding energy storage systems to supplement peak power is important. Solar energy is a sensible, cost-effective, and renewable way to recharge those energy storage systems. Balancing is the key. Solar and storage batteries shouldn't be in excess, and you shouldn't have too many of them. This system must be sized according to the energy demand of your fleet, he said.

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As opposed to focusing on whole-airport solutions, Electro is developing "smart hangars" to help airports, aircraft manufacturers, and operators size solar and storage systems. Several components of the smart hangar are connected via smart communications systems and chargers to form a scalable solution. Hangar systems can grow to meet changing fleet sizes, and multiple hangars can be linked to create a "virtual power plant" on the airport.

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Portlock explained that smart hangars are composed of more than half a dozen subsystems. Our chargers and the smarts inside them communicate with the energy storage systems and the renewable energy sources. To prevent brownouts of the grid connection, you also need solar inverters and smart meters. For example, lithium-phosphate batteries can be used for affordable fixed-energy storage systems, and then repurposed aircraft batteries can be used as supplements later on. For airports in the future, a scalable battery architecture is crucial. Basically, the virtual power plant is the overlaying cloud software that communicates with all of the systems, including multiple airport hangars, to aggregate and share the power."

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"Dynamic load management" is essential to the success of the system, according to Portlock. Optimize your sustainable energy consumption, minimize your capital expense, and monetize your smart hangars. When you distribute energy locally, you can actually trade energy with your neighbors, so if you oversize your solution, you're sharing the excess energy, even if it's done to future-proof for self-consumption in the future.

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Customers will develop smart hangar capabilities in stages, he said. “First, you need to size your smart hangar for energy self-consumption, so that you can power your first couple of aircraft and your existing terminal loads, like air conditioning and lighting, using sustainable energy. By doing this, you combine your sustainable energy and storage systems with the existing grid connection. On the embedded network, you can trade peer-to-peer once you have enough distributed energy solutions within the airport. Rather than fitting it back into the main grid with a minimal return on investment, this method fully utilizes your excess solar with your neighbors.

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If enough energy storage and solar systems are aggregated at the airport, you can augment the grid with multi-MW capabilities, allowing virtual power plants to aggregate distributed energy and control peak demand and frequency. Providing battery backup systems for emergency services within the airport district is another way to give back to the community," Portlock said.

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Despite this peer-to-peer renewable capability, Portlock said small airports and heliports still require from-the-grid electrical upgrades. In a nutshell, it's a mixture of the two. It's important to have a grid connection for overcast days and to have renewable energy for affordable power.”

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