Airships powered by the sun? 

Flying is the most damaging transport mode for our climate – at least, up until now. However, work is already underway to investigate technical alternatives to conventional aircraft, including airships with highly efficient solar cells and extremely light onboard batteries.

Professor Christoph Pflaum from Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) – together with Professor Agnes Jocher from the Technical University of Munich (TUM) and FAU student Tim Riffelmacher – has investigated which route a solar airship would have to take to fly from London to New York as quickly and as climate-friendly as possible. The findings were published in the International Journal of Sustainable Energy.

Pflaum, an expert in numerical simulation using high-performance computers, believes that solar-powered airships offer a quick and cost-effective solution for making aviation more environmentally friendly. “By relying on solar airships, we can significantly reduce the impact of aviation on the climate,” he says.

The researcher has developed a deep enthusiasm for solar-powered air travel throughout his investigations and enthusiastically enumerates its various advantages. “Solar airships are undeniably environmentally friendly, since they are outfitted with exceptionally light and immensely efficient thin-film solar cells that recharge continuously throughout the flight. Consequently, no combustion-related discharges are produced during the airship’s operation,” he explains.

The airship’s battery only requires power from the grid to recharge before take-off. When compared to long-haul cargo flights, solar airships generate less than 1% of CO₂ emissions. For medium-haul flights, the figure is approximately 1.4%, while for passenger transport, it is roughly 5%.

“Currently, the solar airship we are discussing does not exist, but there is a company in California that is making significant investments in developing a fully rigid airship, which will be the first of its kind in 90 years. This airship will provide ample space and excellent protection against wind and weather,” Pflaum enthuses.

“We must adjust our expectations regarding flight time, however, since an airship travels much slower than an aeroplane,” notes Jocher.

Several FAU students conducted simulations and calculations in their Bachelor’s and Master’s theses to determine how fast an airship equipped with solar cells could fly and which route it would need to take to optimise wind and weather conditions and sun position. Most recently, Riffelmacher’s Bachelor’s thesis addressed Charging optimisation of the battery in a solar airship with simulated annealing.

Based on their work, Riffelmacher and the other students demonstrated that national, continental, and even intercontinental flights with acceptable flight duration are feasible. “According to our calculations, a flight across the Atlantic from New York to London takes about two days and one night,” summarises Pflaum. “In the opposite direction, from London to New York, we calculated a flight time of three days and two nights.”

Riffelmacher examined battery usage during day and night in his simulations. “The battery is charged before the flight and must then last for long distances,” explains the young researcher. “This is easier said than done, since there is no sun at night and the solar cells do not generate electricity.” However, optimising the charging process can make many things possible.

Pflaum believes that the slower pace of travel in airships could also be an advantage for passengers who are looking for a more relaxed and comfortable way of travelling. With ample space for amenities like dining rooms, lounges, and stylish double rooms for passengers, airships could provide a unique and luxurious travel experience that is not available on conventional aircraft.