Although solar power has evolved into a low-cost electricity source, it is still not considered a viable energy source for transportation. However, this notion has been challenged recently by innovative projects – an experimental aircraft developed by Airbus managed to fly during 26 consecutive days between July and August 2018, using solar power alone.
There is a key reason why solar power deployment is challenging in transportation systems. Buildings have plenty of rooftop space for photovoltaic arrays, but the same cannot be said of vehicles, boats and aircraft – there is not much space for solar panels, and these devices must have a shape that minimises drag forces from the air or water.
The concept of solar-powered aircraft is very promising, since it is possible to have long flights without refueling – the aircraft can recharge as it flies. Of course, minimising weight is a priority, and the aircraft must be designed to glide without consuming power whenever possible.
The Zephyr S by Airbus is considered a HAPS, or High-Altitude Pseudo Satellite. Unlike commercial airplanes, which fly at altitudes from 30,000 to 40,000 feet, the Zephyr is designed to fly at 70,000 feet. Although it has a wingspan of 25 metres, the Zephyr S only weighs 75 kg. Being an HAPS, the Zephyr can deliver services similar to those of a satellite.
The Zephyr recently broke the longest flight record by a solar aircraft, taking off from Arizona on July 11 and flying for 25 days, 23 hours and 57 minutes. More experimental flights will be performed before the end of 2018, and they will launch from the Wyndham airfield, located in West Australia.
In 2016, another solar-powered aircraft also accomplished an impressive feat. The Solar Impulse 2 flew around the world in 17 separate trips. Unlike the Zephyr, which is an autonomous drone, the Solar Impulse 2 is designed for a human pilot.
Solar technology had to overcome a lot of skepticism and opposition before it became a commercially viable electricity source, but now it is capable of beating the cost of fossil fuels. However, solar power is still criticised for not being viable in transportation.
Transportation is still strongly reliant on fossil fuels, and the environmental footprint will be difficult to avoid until renewable transportation systems become viable. However, there are some success stories already: Zephyr and Solar Impulse 2 are two examples in aviation, and the world’s first solar train was announced last year in New South Wales. Also, thanks to innovation from companies like Tesla, you can now drive an electric vehicle with the output of a residential solar system.
Solar power must also overcome significant challenges in heating applications, where fossil fuels are preferred due to their low heating costs. Electric resistance heaters are affordable, but extremely expensive to operate; on the other hand, electric heat pumps can match the operating cost of gas heaters, but their high upfront cost is a barrier. However, if you live in Australia, you can get heat pump rebates through the Small-Scale Technology Certificate program – the same incentive program that provides rebates for solar systems up to 100 kW.