80% of the world's primary energy supply comes from fossil fuels, primarily oil and coal [1]. Solar energy is important as an alternative energy source as fossil fuel resources are limited and their use is associated with a number of negative environmental effects – such as global climate change and air pollution. The Intergovernmental Panel on Climate Change (IPCC) estimates that about 70% of all greenhouse gas (GHG) emissions world-wide, particularly carbon dioxide (CO2) emissions, come from energy-related activities. This is mainly from fossil fuel combustion for electricity generation, heat generation and transport [2]. Avoiding dangerous climate change and staying below a 2 °C warming requires cutting global emissions rapidly [3]. Energy efficiency and energy from non-fossil fuels, such as renewable energy, are thus important for achieving a global low carbon transition.