Solar Impulse 2, a solar-powered aircraft, has entered the second week of its historic 35,000km (five month) journey around the world. Piloted by Andre Borschberg and Bertrand Piccard, it is the first airplane able to fly day and night without a drop of fuel.

This record-breaking flight is a demonstration of the growing viability of clean energy. Deutsche Bank forecasts that, based on current fossil fuel prices, solar will produce power as cheaply as gas in two thirds of the world before 2020; the International Energy Agency expects solar power to become the dominant source of electricity globally by 2050.

Here are some fantastic speakers on sustainable technologies, renewable energy and behaviour change: