Renewable Energy

Flying Cell Towers Enabled by 29.1% Efficient Single-Junction GaAs Solar Cells

Alta Devices introduced a new solar product that enables flying cell phone towers. According to the company, the solar product combines record-setting solar efficiency with specialized packaging and integration in the first-ever dedicated unmanned aireal vehicle (UAV) solution designed to fly at 60,000 feet for years at a time. Such specialized UAVs can serve as platforms for cellular and IoT connectivity.

The solar product, called AnyLightTM Solar for high altitude long endurance UAVs helps maximize power as well as minimize weight. (See image above). It is based upon world-record efficiency single junction gallium-arsenide solar cells, also features sufficient protection from the harsh environment commonly found in the Earth’s stratosphere.

High altitude long endurance (HALE) UAVs that fly at stratospheric levels (sometimes also referred to as high altitude pseudo satellites (HAPS)), are an critical new aircraft category and can include airships, airplanes, and/or balloons that can fly at altitudes of 20 kilometers (60,000 feet) for extended periods.

In addition to being used for a variety of communications (such as cell phone connectivity and others), these aircraft can be utilized for intelligence surveillance and reconnaissance (ISR), search and rescue, border patrol, mapping, and many other applications. Solar power is critical for these unique aircraft, especially because the goal is to fly for years without having to refuel.

NASA HALE UAV

Flight at this altitude requires solar technology that is more rugged than the type used in terrestrial installations, but it also has to be different from the solar cells used in space. For example, at 60,000 feet, ultraviolet radiation from the sun is considerably more intense than on the earth’s surface. Unlike in space with zero gravity, the generation of lift for stratospheric vehicles that operate at these altitudes is critical.

Therefore, to allow the aircraft to carry a useful payload and enough batteries for night flight, the solar technology used must be extremely light-weight.

Also, in contrast to both terrestrial and space applications, at 60,000 feet, mechanical stresses during flight can be very hard on the aircraft surface and solar panels. So, the solar material must be flexible and durable.

The single junction gallium-arsenide solar cells produce what the company describes as industry-leading power-per-unit-area under high-altitude operating conditions.

Alta has worked closely with its HALE customers, leaders in aerospace innovation, to solve critical challenges related to the mechanical and electrical integration of this technology onto multiple aircraft platforms.

The company developed a unique, lightweight packaging solution that protects the solar cells from the extreme UV, ozone and the thermal environment of the stratosphere while preserving a smooth, aerodynamic surface.

Other crucial issues that the solar panels addressed include being able to withstand mechanical stresses and vibration expected during flight.

Alta devices had to develop methods for the successful co-curing of the solar materials into lightweight composite structures.

Optimizing Solar Array for Stratospheric Aircraft

Optimizing a solar array for an aircraft demands complex configurations that minimize electrical mismatch, maximize cell packing factor, and let the design utilize the maximum surface area for solar.

Alta worked with its customers to understand these requirements and developed advanced module designs that address these issues, thus offering an easy-to-integrate solution that maximizes system performance, while reducing the amount of work required during installation.

“Alta Devices recognizes that our aerospace customers need to innovate every aspect of these new and complex aircraft systems. With our new HALE solar solution, they now have one less thing to worry about. This will simplify the design process and significantly reduce the complexity involved in manufacturing these aircraft,” Alta Devices CEO, Jian Ding, commented.

Alta Devices HALE Solar Product Specs

The Alta Devices HALE solar product, called Anylight Solar for HALE is now available. The product utilizes the company’s recently announced 29.1% world-record efficiency single junction solar cell.

It delivers a performance of over 300W/m2 under high-altitude operating conditions. This product provides industry-leading packing density of up to 94% including diodes and connectors. Aerospace-grade UV and ozone-resistant materials encapsulate the lightweight gallium arsenide solar material its multi-year life.

Alta Devices’ engineers that have extensive expertise in integration are available for customer support and advice on optimal integration techniques such as co-curing or adhesives.

Anylight Solar for HALE features a mass of only 170 g/m2, and can bend to cover curved surfaces. It can be seamlessly integrated into plastic, carbon fiber, fiberglass, or foam molding along with tailored electrical voltage and current output optimized to the power system.

Designed to withstand harsh stratospheric conditions that include high levels of UV, ozone and thermal cycling. The company claims that Anylight Solar for HALE is the first solar technology designed specifically for HALE and HAPS aircraft.

Overview
  • First solar technology designed for stratospheric flight
  • No glass used: solar package includes aerospace-grade flexible film and adhesives designed for multi-year life
  • Testing completed by Alta Devices to ensure technology can withstand stratospheric UV radiation, ozone, thermal cycling and other stressors
  • Experienced Alta Devices team can provide solar product layout and integration support.

Finally, Alta Devices is ramping its production capability in response to its customers, who plan to manufacture a multitude of HALE aircraft in the near future.

Alta Devices
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