Powering the planet: Chemical challenges in solar energy utilization

TLDR

Global energy demand is projected to double by midcentury, and while fossil fuels could meet this need, the cumulative CO₂ emissions necessitate carbon‑neutral energy, making solar—the largest renewable resource—an attractive option that must be stored and dispatched on demand due to insolation intermittency. The study aims to develop large‑scale, carbon‑neutral energy production, particularly by storing solar‑converted energy in chemical bonds through highly efficient photosynthetic processes that reduce land‑area requirements. The approach involves capturing and converting solar energy into chemical bonds, producing oxygen from water and reduced fuels such as hydrogen, methane, methanol, or other hydrocarbons.

Abstract

Global energy consumption is projected to increase, even in the face of substantial declines in energy intensity, at least 2-fold by midcentury relative to the present because of population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of CO(2) emissions in the atmosphere demands that holding atmospheric CO(2) levels to even twice their preanthropogenic values by midcentury will require invention, development, and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable energy resources, solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. In view of the intermittency of insolation, if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user. An especially attractive approach is to store solar-converted energy in the form of chemical bonds, i.e., in a photosynthetic process at a year-round average efficiency significantly higher than current plants or algae, to reduce land-area requirements. Scientific challenges involved with this process include schemes to capture and convert solar energy and then store the energy in the form of chemical bonds, producing oxygen from water and a reduced fuel such as hydrogen, methane, methanol, or other hydrocarbon species.