The idea of using solar radiation to generate air convection that can subsequently be converted to an energy source has been around since the start of the 20th century, when a Spanish Colonel called Isidoro Cabanyes proposed it in a scientific magazine. Solar Updraft towers, also called solar wind or solar chimney plants, provide a very simple method for renewable electricity generation, with a constant and reliable output. Other renewable energy sources such as wind turbines and solar arrays suffer from high diurnal and seasonal fluctuations, or unpredictable patterns of output.