Solar technology is undoubtedly one of the most exciting forms of clean energy available. The mainstream uptake of solar technology and keen interest in experimenting with solar power has led to numerous innovations and inventions. With 2015 now over, it’s time to review some of the most inspiring solar innovations it brought us. Powered by clean, green energy from the sun, these are five notable solar inventions from 2015.

The world’s first solar hot air balloon

The first solar-powered hot air balloon took flight in 2015 at the International Fiesta in Bristol. Powered by air heated by the sun’s rays rather than the standard propane burner, the balloon was made by UK-based hot air balloon maker Cameron Balloons. The successful design was the result of much experimentation by a team of designers and engineers. In addition to observing the strict certification rules set out by the Civil Aviation Authority on materials that can be used, the company had to overcome the challenge of materials and designs that were too heavy and fragile.

As the solar power heated the air to only 40 degree Celsius (about half the temperature of a typical hot air balloon), the materials had to be light but durable. In the end, the engineering team found success by coming up with a two-sided design with a black side that collected heat and a shady side that trapped it. The balloon could be turned by activating vents, so that the pilot could direct whichever side towards the sun to give the balloon more lift or to reduce lift.

Solar panel cooling technology

2015 was also the year in which a team of three Stanford University engineers invented a special coating for cooling solar cells. While solar cells rely on the heat of the sun to generate power, the temperature impacts their conversion efficiency. When applied to solar panels, the silica-based coating captures and emits thermal radiation, leading to cooler solar panels.

The invention was based on earlier research by the same team of engineers that explored materials to radiate infrared heat back into space without heating the atmosphere. As engineer Professor Shanhui Fan explained, the thermal overlay lets sunlight pass but radiates the heat out to ensure cells operate more efficiently. Tests carried out showed that the coating cools solar panels by as much as 13 degrees Celsius, which could translate to a significant boost of 1 per cent increase in cell efficiency. This new cooling material could be used in other applications, such as paintwork on cars and other surfaces.

Ripasso solar electricity generation system

Solar energy generation continued to push past its boundaries in 2015, with companies like Sweden’s Ripasso producing a new solar electricity generation system that has been described as the most efficient of its kind in the world. The invention uses massive mirrors arranged in the shape of satellite dishes to concentrate raw solar energy into a tiny ‘hot point’ that drives a Stirling engine to generate power.

The Stirling engine was invented in the 1800s and is completely emission free. While current residential solar panel systems turn around 15%-18% of the sun’s energy into useable power, the Ripasso system is able to convert around 34% of the sun’s energy hitting its 100-square-metre dishes, which turn to follow the trajectory of the sun through the day. If the system comes to market, a single dish may be able to supply enough energy for 24 homes.

Solar-powered desalination

Access to clean, cheap, drinkable water is a struggle for many people around the world, but we might be just a bit closer to reaching the goal of plenty of safe water for everyone thanks to solar technology. In 2015, the $140,000 Desal Prize (organised by USAID and partners), was awarded to a team from MIT and Jain Irrigation Systems who invented a solar-powered desalination system. The device removed salt from seawater by applying an electrical current to draw out salt particles. The system also disinfects some of the water by utilising UV light.

Solar-powered desalination isn’t a new concept, but such systems require little maintenance and high durability to be scalable and efficient. The winning team put its invention through rigorous testing by running it continuously for 24 hours and filtering 2,100 gallons of water per day. Further refinements could see the system being used to desalinate large volumes of seawater for larger scale users such as farms.

Solar sunflowers

Film director James Cameron is well known for his interest in green issues. In 2015, he gifted five solar sunflowers to his wife, Suzy Amis-Cameron. Measuring nearly 30 feet in diameter with a 16-feet stem, the sunflowers are made of solar panels and were installed at Amis-Cameron’s non-profit school in California, the MUSE School. The massive flowers not only deliver a spectacular visual impact, they generate around 300 kilowatts hours of power per day, or as much as 90% of the school’s power requirements.

The solar sunflowers rotate by following the location of the sun in the sky to maximise capture, and if there are strong winds, the sunflowers will automatically adjust themselves to lie flat. Cameron has patented his solar sunflower design, but the patent will be widely available and open source to encourage more people to make use of solar power.