Efficiency Limit of Molecular Solar Thermal Energy Collecting Devices

Abstract

As a larger fraction of energy is based on solar energy and other renewable energy sources, technologies for energy storage and conversion is becoming increasingly important. Molecular solar thermal (MOST) is a concept for long-term storage of solar energy in molecules and release of the energy as heat with full regeneration of the initial materials. The process is inherently closed cycle and emission free. No assessment of the fundamental efficiency limits of the technology has been made. In this report, efficiency limits and fundamental factors for molecular design of molecular solar thermal systems are discussed. Maximum efficiencies and potential temperature gradients are estimated using a number of basic assumptions on desired storage lifetimes and energy losses. The predicted maximum solar energy conversion efficiency is 10.6% at a S1–S0 gap of 1.89 eV. At this S1–S0 gap, the stored energy is able to create temperature differences of ∼300 °C. Several existing systems have an energy storage density i...