Global available solar energy under physical and energy return on investment constraints

The amount of energy striking the earth’s surface in one hour is higher than global annual societies energy use, yet the fraction of incoming solar radiation that can be harvested is significantly constrained. A global grid-cell methodology was adopted to assess the available global solar energy potential taking into account four constraints: land-use, solar irradiation, solar-to-electric technology, and net energy. Net energy is the amount of energy that is delivered to end-users, after subtraction of the energy inputs needed for capital infrastructure and operation. Both photovoltaic and concentrated solar power technologies are considered. The resulting constrained solar potential worldwide was estimated at 1098 exajoules per year, of which 98%, 75%, and only 15% can be extracted if the system needs to deliver an energy return on energy invested set at 5, 7.5, and 9, respectively. The resulting global solar potential is substantially lower than most previous estimates. Depending on how high the energy return needs to be relative to the energy investment needed to maintain a sustainable society, the achievable potential will be significantly constrained. The effect is especially significant in lower solar radiation regions. The European Union holds only 2% of the global solar net energy potential.