On the path toward day and night continuous solar high temperature thermochemical processes: A review

Abstract

High temperature solar thermochemical processes for fuels and chemical commodities production have been studied for decades and their feasibility is now proven. However, industrial deployment is limited and one of the main reasons is that the variability of solar energy hinders a priori day and night continuous solar process operation. Nevertheless, solar intermittence is now very well managed for Concentrated Solar Power (CSP) electricity production. Indeed, thermal storage up to 600°C is demonstrated and CSP electricity is base-load capable. However, far beyond electricity, heat supply is the major need in industry. This work reviews the recent works published or patented in the field of continuous operation of high temperature solar thermochemical processes (>600°C). There is currently a strong commitment toward day and night solar processes operation since it could improve durability, quality of the products, efficiency and economics of such technologies. Indeed, industrial processes are mainly continuous and daily start up and shut down strongly limit the production capacity of the solar-driven processes, which represents a major lock for scale up. For the first time in this paper, day and night continuous high temperature solar processes are reviewed and categorized. The reported works show the great innovation activity in this field and the various options investigated to date. The main outcomes show that continuous heat supply is possible thanks to hybridization or thermal energy storage. Highlights: Round the clock high temperature solar thermochemical processes are reviewed  Hybridization (fuel, electricity) enables day and night operation  Hybrid solar/autothermal process can operate 24h a day  Heat storage can supply solar heat at night, either directly or indirectly  The solar flame concept is presented for continuous high temperature heat supply

Thermodynamic and Experimental Investigation of Solar-Driven Biomass Pyro-Gasification Using H2O, CO2, or ZnO Oxidants for Clean Syngas and Metallurgical Zn Production

“…The leading renewable energy sources consist of solar, biomass, hydropower, wind, and geothermal. Noticeably, renewable biomass and solar resources can be integrated within a solar gasification process [1]. The solar gasification process represents a promising avenue to convert solid carbonaceous materials into green synthesis gas (H 2 + CO) [2].…”

“…Alternatively, the gasification reaction with solid oxidants is possible [13]. Solid ZnO oxidant represents a favorable candidate for solar biomass gasification because its reduction temperate with carbonaceous materials is moderate (as compared to the thermal dissociation of ZnO (ZnO↔Zn + 1 2 O 2 ) which requires temperatures above 1500 • C [14]), and it suitably matches the gasification temperature [15].…”

“…This ZnO reduction process using biomass as reducer allows operating at much lower temperature than that required for the solar thermal reduction process (ZnO → Zn(g) + 1 2 O 2 ), as part of the two-step ZnO/Zn redox cycle for H 2 O and CO 2 splitting [16,17]. The produced solid Zn derived from solar thermochemical conversion process can be recycled to ZnO after reacting with H 2 O (Equation ( 13)) or CO 2 (Equation ( 14)) to produce H 2 or CO in a two-step cycle [18,19]:…”

Techno-Economic Assessment of Solar-Driven Steam Gasification of Biomass for Large-Scale Hydrogen Production

“…On the one hand, the solar process allows for the production of a highquality synthesis gas with a higher gas output per unit of feedstock, and on the other hand, the solar process is highly dependent on an intermittent heat source, which requires an initial substantial investment. The question is, therefore, not simple, and requires detailed investigation to highlight both technical aspects related to the management of the heat source variability [17][18][19][20] and economic and financial aspects for accurate cost evaluation [21][22][23]. In a previous work [19], a dynamic mathematical model of an up-scaled MW steam solar gasifier was developed.…”

Solar-hybrid Thermochemical Gasification of Wood Particles and Solid Recovered Fuel in a Continuously-Fed Prototype Reactor

“…Since then, other reactor designs, including packed beds [20,25], fluidized beds [18,26], spouted beds [15,27], vortex flow [21,28], drop tube [16,29], and molten salt [10,30] reactors were tested to convert a wide variety of feedstocks such as biomass, coal and different kinds of waste with either steam or CO 2 as an oxidizing agent. Recent exploratory work on hybrid solar gasification makes use of O 2 as a means to maintain the process temperature during sun-lacking periods thanks to combined solar heating and in-situ oxy-combustion [31][32][33][34]. Recently, the concept of coupling solar energy with thermochemical reactions to energetically upgrade biomass has been extended to hydrothermal processes [35,36].…”