IGM Colloquium: Solar energy harvesting and storage - an integrated approach

In the 16^th century Thomas More described an ideal and sustainable city in his book Utopia. Today´s an ideal city should comply with the Near Zero Energy Building directive (nick name for the Energy Performance of Buildings Directive (2010/31/EU)) and going beyond. PV electricity is already today the cheapest if produced in countries with high solar irradiance; the world’s cheapest price for electricity of 2017 was for a PV farm in Saudi Arabia [1].

PV electricity is, however, only generated during the daylight time and then just partially dispatchable. To make it fully dispatchable it is necessary to store and batteries is a technology of choice. Among electricity storage technologies redox flow batteries (RFB) emerged as promising offering very low storage costs [2], independent power from storage capacity, very reliable and robust operation. The all vanadium RFBs display an energy density of ca. 50 Wh/L but the use of non-aqueous solvents for dissolving the redox pairs promises to bring soon this energy density to values which ideally can reach 1 kWh/L. The storage of electricity in an electrochemical fluid instead of a solid such as in conventional batteries opens the doors to the electrochemical fuels that can be easily stored and transported.

More recently, it was proposed the direct conversion of sunlight into storable electrochemical fuels using photoelectrochemical panels. These panels comprehend just a glass window coated with a semiconductor and an ion-exchange membrane; the positive and negative electrolytes pass through charging and heating up in a cogeneration process. The solar redox flow batteries promise to bring the cost of stored electricity to even lower values making the dream of self-energy sustainable cities a closer reality.

References
[1] - https://www.thenational.ae/business/energy/world-s-cheapest-prices-submitted-for-saudi-arabia-s-first-solar-project-1.663842 – consulted in February 2018.
[2] - http://energystoragereport.info/study-flow-batteries-beat-lithium-ion/#sthash.lfBTEoYs.dpbs – consulted in February 2018.


About the author

Professor Adélio Mendes (born 1964) received his PhD degree from the University of Porto in 1993. Full Professor at the Department of Chemical Engineering of the Faculty of Engineering of the University of Porto. Professor Mendes coordinates a large research team with research interests in dye sensitized solar cells and perovskite solar cells, photoelectrochemical cells, photocatalysis, redox flow batteries, electrochemical membrane reactors (PEMFC, H-SOFC, chemical synthesis), methanol steam reforming, membrane and adsorbent-based gas separations and carbon molecular sieve membranes synthesis and characterization.