The Stratobus project is led by Thales Alenia Space (TAS). It is a new concept for an autonomous airship, operating at an altitude of about 20 kilometers. This is in the lower reaches of the stratosphere, but well above air traffic and jet streams. Stratobus will be able to carry a 250kg/5kW payload. Use of Stratobus covers a wide range of potential applications, including e.g. border and maritime surveillance, telecom and gps augmentation. The platform itself is a high-altitude airship measuring about 100 x 030 meters. The Stratobus platform will require continuous significant energy input to offset the wind. It will feature a number of technological innovations, in particular to make sure it captures the Sun's rays in all seasons, a power generation system and an ultra-light reversible fuel cell for energy storage.

Supplying the platform's energy storage system

Stratobus use solar energy to power payloads and the electric propulsion system, and therefore need to store energy that can be used at night when no solar power is available. The energy storage system is a regenerative fuel cell system (RFCS) consisting of an electrolyser, water-, hydrogen- and oxygen storage tanks, a fuel cell and auxiliary components. RFCS technology is preferred over other energy storage technologies due to low mass and corresponding high specific energy (Wh/kg), which is essential for the Stratobus platform. The degree of innovation in this project is high and exclusive designs/ solutions must be developed by Prototech including among others:

- High efficiency fuel cells

- Compact high pressure electrolyser

- Advanced manufacturing process to reduce mass and production cost

- System integration and autonomous operation without maintenance.