Reducing greenhouse gas emissions is a prevalent challenge faced by commercial aviation. The sector contributes 2.6% of global emissions, and, as the sector lags behind others in the decarbonization process, that percentage might increase to as high as 5%.
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By 2030, much more people will travel by air, and the current airline commitments to utilize low-carbon alternative fuel will only partially offset that expansion.
Solar Energy for Aircraft
The amount of sunlight that reaches the surface of the earth in an hour is sufficient to meet all of the world's energy needs for a complete year.
Solar energy systems use photovoltaic (PV) panels to convert sunlight into electrical energy. This power can be transformed into electricity and used in the aircraft industry.
Solar energy via photovoltaic panels was recognized as an alternate energy source during the 1970s fuel crisis. Due to their use as an ecologically beneficial option, solar-powered aircraft have recently gained the general public’s and aviation industry’s interest. Unlike conventional aircraft, solar-powered aircraft use photovoltaic panels to collect solar irradiance and convert it into electrical energy.
Preference of Solar Powered Aircrafts over Traditional Aircraft
Solar-powered aircraft have a huge potential for high-altitude and long-endurance (HALE) missions because of the infinite supply of solar electricity.
Solar-powered aircraft can be built to fly close to space (around 20–100 km) just above the atmospheric flight zone and below the spacecraft flight region.
Depending on the aircraft system's endurance and the availability of sunlight, they can cruise continuously for months or even years, which is something that conventional airplanes cannot do due to their operational constraints.
How Does a Solar-Powered Aircraft Work?
The basic concept is to cover a particular area of the aircraft with solar cells, such as the wings and tail.
Photovoltaic panels transform solar energy into electrical energy when exposed to the sun's beams. The solar panel direction and the sun’s brightness are two elements that affect how much energy is produced.
The circuit that manages the power transmission output has a programmable microcontroller. The control and transmission systems for power ensure that solar panels produce the most energy possible. The majority of the electricity produced is used to power the aircraft's electronics and propulsion system. Batteries used when there is little sunshine are recharged using the extra energy.
The fundamental idea is to use aircraft to transport solar energy, and the solar panels that cover the aircraft can accomplish this. Radiative energy is transformed into electric energy using these panels. The battery that powers the electric motor is charged using this electric energy.
The motor-mounted propeller continually creates thrust. As a result, the air's dynamic action propels the aircraft and produces a force on its wings in opposition to the weight's downward force. The battery is the only source of energy during the night.
Advantages of Solar-Powered Aircraft
Solar-powered aircraft are environmentally friendly. The most significant benefit of solar-powered flights and the underlying reason for their development is that they rely on a clean source of energy that has no negative environmental effects.
Solar energy has a significant advantage over fossil fuels because it is a free, clean, and renewable energy source.
Disadvantages of Solar-Powered Aircraft
Traditional flights are less affected by weather variations than solar-powered flights. Traditional aircraft can be delayed by the weather or have their trip become more challenging, but solar-powered aircraft can only fly in certain weather conditions, especially for long-distance flights, as they need to recharge in the air.
Although solar energy is practically free, the equipment and technologies needed to harvest and use it are very expensive, particularly considering the scale at which single-rider aircraft would need to be operated.
The First Solar-Powered Aircraft and the Modern Aircraft
Electric power has long been used to propel flying machines. The first one was the hydrogen-filled French dirigible, which triumphed in a 10-kilometer (km) race near Villacoulbay and Medon in 1884.
When gasoline engines arrived, electrical propulsion for air vehicles was abandoned, and the field was inactive for nearly a century. At the time, the electric system was superior to its sole opponent, the steam engine.
In front of excited spectators and photographers, Solar Impulse 2 touched down in Abu Dhabi in the early hours of July 26, 2016. The plane completed what many had thought was impossible. After 14 months and 550 hours in the air, it flew 25,000 miles around the globe, crossing four continents, two oceans, and three seas without using any liquid fuel. The only source of electricity for the vessel was the sun's bright rays.
Construction of Solar Impulse 2, the Round-The-World Solar Airplane
Video Credit: SOLAR IMPULSE/YouTube.com
Recent Research and Developments in Solar-Powered Aircraft
Solar fuel cells, such as other competing technical methods, have been developed to produce electricity in fixed systems. Current R&D efforts focus on developing reliable, low-cost, high-performance energy networks for aviation applications.
Rapid technological advancements are being made to improve and expand the use of solar aviation. In this context, organic photovoltaic systems are significant. Organic photovoltaics (OPVs) are made from organic materials that are diverse and versatile, offering endless chances to enhance a broad range of characteristics. Organic molecules are cheap and have good light absorption properties, enabling coatings as thin as several hundred nanometers to be utilized for this purpose.
A recent advancement in solar-powered aircraft is the development of the Zephyr S aircraft. The Zephyr S aircraft, also known as a drone and a pseudo-satellite, took flight from the United States Army's Yuma Proving Ground in Arizona. It was designed to remain in the air for extended periods, enabling it to act as a military sensor platform.
Continue reading: Recent Developments Making Hydrogen Aviation a Reality
References and Further Reading
Abbe, G., & Smith, H. (2016) Technological development trends in Solar‐powered Aircraft Systems. Renewable and Sustainable Energy Reviews, 60, 770–783. https://www.sciencedirect.com/science/article/abs/pii/S1364032116000836
Gao, X.-Z., Hou, Z.-X., Guo, Z., & Chen, X.-Q. (2015). Reviews of methods to extract and store energy for solar-powered aircraft. Renewable and Sustainable Energy Reviews, 44, 96–108. https://www.sciencedirect.com/science/article/abs/pii/S136403211400956