Trends in renewable energy: an overview

This essay deals with the prospects of supplying humanity with energy in the twenty-first century. The gradual replacement of fossil fuels by green electricity, hydrogen and biofuels is examined in the context of deteriorating climate change and the ongoing depletion of fossil fuels. The production of large amounts of green electricity through the spreading of wind-energy, photovoltaic, concentrated solar power, hydroelectric power and high temperature geothermal plants and its storage through the global interconnection of electricity grids, the spreading of pumped hydro energy storage and melting salts plants and the lithium batteries leads certainly to a future world largely but not exclusively electrical. Hydrogen will be a very important energy carrier. The production of blue and green hydrogen, their transport and usage in cars, industry and trains in the near future as well as in ships and airplanes in the distant future is outlined. Biofuels must be inevitably added to the future energy profile of mankind besides green electricity and hydrogen. The modern trend of producing biofuels from residual fatty raw materials, microalgae and agricultural/forest residual raw materials to overcome the competition with foods production for land and water as well as the residual biomass utility for the production of aircraft fuels and bio-chemicals in the near future is also illustrated. Finally, the increasing contribution of biogas/biomethane to the future energy profile has been presented.