Solar Biomass Gasification Research Articles

Development of machine learning-based models for describing processes in a continuous solar-driven biomass gasifier

The synergy of two renewable and efficient sources in producing clean fuels, i.e., solar energy and biomass, can result in high efficiency. In this regard, developing syngas production systems based on solar biomass gasification has attracted much attention. However, experimental setups on solar-driven gasifier processes are costly and time-intensive. In such a situation, an accurate and low-cost alternative is to develop data-driven machine learning (ML) models to predict the processes involved in solar-driven biomass gasifiers. In the present study, several ML models, including random forest (RF), RANdom SAmple Consensus (RANSAC), stochastic gradient descent (SGD), automatic relevance determination (ARD) regression, and elastic net linear (ENL) regression, were developed to accurately predict the various processing of a continuous solar-driven biomass gasifier, including CO production rate and H2 production rate (H2), carbon feeding rate, solar power input, thermochemical reactor efficiency, solar-to-fuel energy conversion efficiency, solar energy input, and carbon consumption rate. Using efficient ML methods, the eight formulas and the eight models for H2, CO production rate, carbon feeding rate, carbon consumption rate, solar energy input, solar power input, thermochemical reactor efficiency, and solar-to-fuel energy conversion efficiency are made in this study. Using the linear form can be reached the best R-Squared (R2) values for all formulas and the model, and the best R2 values are between 0.998 and 0.999 for the formulas by the elastic net and the ARD regression, and also the best R2 values are between 0.998 and 0.999 for the models by the RF and the RANSAC regressor. The R2 values for H2, CO production rate, carbon consumption rate, solar energy input, solar power input, thermochemical reactor efficiency, and solar-to-fuel energy conversion efficiency for formulas, respectively, are 0.998, 0.998, 0.999, 0.999, 0.999, 0.996, and 0.998 by the elastic net. For temperature of the carbon feeding rate, this value is 0.999 by the ARD regressor.

Concentrating solar assisted biomass-to-fuel conversion through gasification: A review

Solar energy, the most abundant and exploitable renewable energy resource, is regarded as a major energy source for the future. Nevertheless, solar irradiation is characterized by relatively low energy density, intermittency and uneven distribution. Storage of solar energy for usage during non-solar times is required to match supply and demand rates in today’s society. In this context, the application of solar energy for converting into storable, transportable, and energy-dense fuels (i.e., solar fuels) is an attractive option, with the advantage of contributing to promoting the commercialization of solar power technologies. Solar assisted biomass gasification is a promising pathway to produce solar fuels. With concentrated solar energy providing reaction heat, carbonaceous materials can be converted to high grade syngas, which could be further synthesized into useful hydrocarbon fuels. In such process, solar energy is stored in a chemical form, with solar spectrum fully utilized. Compared with autothermal biomass gasification, the usage of high-flux concentrated solar radiation to drive endothermic gasification reactions improves energy efficiencies, saves biomass feedstocks, and is relatively free of combustion by-products. This review presents a comprehensive summary of solar assisted biomass gasification, including concentrating solar technology, fundamentals of solar biomass gasification, state-of-the-art solar gasifier designs, strategies for solar intermittence management, and downstream applications.

Effect of surface material properties and operating conditions on the heat flux and temperature distributions in the cavity receiver of a solar-dish-coupled biomass gasification reactor

In this paper, a new 5.8 kW solar biomass gasification reactor is modeled by means of Monte-Carlo ray-tracing method and computational fluid dynamics. The reactor is coupled to the cylindrical cavity receiver of a parabolic-dish solar concentrator, where the incoming solar heat flux is concentrated. The absorbed heat flux distribution (flux density map) at each receiver surface is determined with the ray-tracing software SolTrace®. The sensitivity of the flux distribution to three uncertain variables is evaluated: the receiver solar absorptance, the receiver reflection type and the tracking error. It was found that the tracking error causes a pronounced increase in the flux peak at the cylindrical surface, while reflection scattering greatly reduces the flux peak at the bottom surface. Solar absorptance redirects the flux from every surface to the cylindrical surface, and so, it increases its flux peak. Reflection scattering reduces reflection losses. Two extreme flux concentration cases were found: 0.95 absorptance and 0.5° tracking error produce a 231 kW/m2 peak at the cylindrical surface; 0.25 absorptance, no tracking error and specular reflection produce a 250 kW/m2 peak at the bottom surface. The heat transfer within the reactor is modeled with ANSYS® CFX® with the flux distributions of the extreme cases as boundary conditions. The receiver temperature contours were obtained. Peak temperature locations coincided with the peak flux locations. For a 1200 K gas outlet temperature, peak temperatures of up to 1470 K were found, which exceed the material limit (1273 K). This issue is avoided by selecting suitable surface properties: solar absorptance <0.42 and a Gaussian specularity error >300 mrad.

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

Solar biomass gasification is an attractive pathway to promote biomass valorization while chemically storing intermittent solar energy into solar fuels. The economic feasibility of a solar gasification process at a large scale for centralized H2 production was assessed, based on the discounted cash-flow rate of return method to calculate the minimum H2 production cost. H2 production costs from solar-only, hybrid and conventional autothermal biomass gasification were evaluated under various economic scenarios. Considering a biomass reference cost of 0.1 €/kg, and a land cost of 12.9 €/m2, H2 minimum price was estimated at 2.99 €/kgH2 and 2.48 €/kgH2 for the allothermal and hybrid processes, respectively, against 2.25 €/kgH2 in the conventional process. A sensitivity study showed that a 50% reduction in the heliostats and solar tower costs, combined with a lower land cost of below 0.5 €/m2, allowed reaching an area of competitiveness where the three processes meet. Furthermore, an increase in the biomass feedstock cost by a factor of 2 to 3 significantly undermined the profitability of the autothermal process, in favor of solar hybrid and solar-only gasification. A comparative study involving other solar and non-solar processes led to conclude on the profitability of fossil-based processes. However, reduced CO2 emissions from the solar process and the application of carbon credits are definitely in favor of solar gasification economics, which could become more competitive. The massive deployment of concentrated solar energy across the world in the coming years can significantly reduce the cost of the solar materials and components (heliostats), and thus further alleviate the financial cost of solar gasification.

Solar gasification of grape marc for syngas production: Solar-dish-coupled reactor basic engineering and optimization

In this paper, a new 5.8 kW solar biomass gasification reactor design is proposed. It is meant for energetic exploitation of grape marc, a residue of the wine-making industry. The design couples the reactor with a 3.0 m diameter Parabolic Dish Solar Concentrator, and contemplates controlling its temperature by manipulating the biomass inlet rate. This work aims to establish an upper limit on the reactor syngas yield under actual solar and environmental conditions, to determine the optimal dimensions of the reactor, and to evaluate the feasibility of the temperature control system. Also, a process is proposed for industrial application and practical implications are considered. The performance of the reactor was numerically simulated employing 1-min solar irradiance data, heat transfer models, reaction models and enthalpy balances. The reactor dimensions that maximize syngas production were determined. Simulation results showed an upper limit of 73 gdry basis/min for the grape marc inlet rate (stationary regime), and of 3180 Nm3 (36.68 GJ) for the total syngas yield on the grape marc production season. Solar irradiance peaks were compensated, which supports the proposed temperature control system. Several design aspects were found to have substantial impact on the reactor performance, which contributes towards prototype manufacturing.

Experimental and CFD investigation of inert bed materials effects in a high-temperature conical cavity-type reactor for continuous solar-driven steam gasification of biomass

Solar biomass gasification was performed in a high-temperature conical bed reactor for thermochemical syngas production, which represents an efficient route to promote biomass valorization while storing intermittent solar energy into carbon–neutral solar fuels. The developed solar reactor is based on a conical cavity-type receiver enabling continuous biomass feedstock injection under real concentrated solar irradiation. In this study, the use of inert bed materials is considered to directly absorb a portion of the entering solar power and to transmit thermal energy to the gas and reactive particulate phase by radiation, convection and particle-to-particle interactions, with the aim of homogenizing the reactor temperature. A fluid dynamics study of the gas/particle flow was first performed to provide insights into the reactor hydrodynamics in the case of empty cavity and cavity containing inert particles in the forms of packed-bed and spouted-bed. The beneficial effect of the inert particles bed was emphasized. The spouted bed particles play a role in retaining the reacting biomass particles longer inside the reaction zone and promote phase mixing, as also confirmed by cold tests on a replicated transparent mockup cavity. Different inert particle bed materials were then considered and experimentally tested to unravel their impact on the biomass conversion, syngas composition and yield, and gasification performance in the solar-heated reactor operated at 1200 °C and 1300 °C.

Solar Biomass Gasification Combined With Iron Oxide Reduction for Syngas Production and Green Iron Metallurgy

The solar gasification of biomass with iron oxide for combined syngas and iron production was investigated. Both solar energy and biomass are promising renewable energies. The process of gasification converts solid carbonaceous feedstocks into either fuels or chemicals. However, conventional processes require partial combustion of the feedstock for energy supply and inherently suffer from high oxygen production costs and low syngas calorific value due to dilution with combustion products. Chemical looping gasification using solid oxides is an alternative option to tackle these issues. By supplying concentrated solar energy as the high-temperature heat source, it is possible to produce even more syngas from the process while enabling solar energy storage into dispatchable fuels. This work proposes to explore solar biomass gasification over iron oxide at high heating rates, representative of the conditions obtained in solar reactors. Thermodynamic equilibriums of gasification reactions between 100 and 1500°C were calculated and experimental results obtained at 1100°C with a specially designed induction furnace were reported for biomass gasification with iron oxide, water or carbon dioxide as oxidizing agents. Solid products analysis showed that iron oxide can be reduced to metallic iron depending on the proportion of the oxygen carrier. These results indicate that iron oxide is an effective material for solar biomass gasification producing both syngas and iron via a novel green metallurgical process.

Dynamic simulation and control of solar biomass gasification for hydrogen-rich syngas production during allothermal and hybrid solar/autothermal operation

Solar biomass steam gasification using concentrated sunlight offers an efficient means of storing intermittent solar energy into renewable solar fuels while upgrading the carbonaceous feedstock. Such solar-driven (allothermal) processes have demonstrated the ability and the effectiveness for the production of high quality hydrogen-rich syngas, but they suffer from inherent barriers related to the variability of solar energy caused by cloud passages and shut off at night. The concept of hybrid solar/autothermal gasification appears promising to meet the requirement for stable and continuous operation under fluctuating or intermittent solar irradiation. To date, dynamic modelling to simulate coupled solar/combustion heating and steam gasification using real solar irradiation data has never been proposed and could be used to predict the annual performance of large-scale solar gasification plants. In this study, a dynamic mathematical model of a scaled-up solar gasification reactor was developed. The model was composed of a system of differential equations that were derived from unsteady mass and energy conservation equations. After an experimental validation step with the results from a lab-scale solar reactor, the dynamic model was applied at large scale to determine the reactor temperature and syngas production evolution during continuous day and night operation in both solar-only (allothermal) and hybrid solar/autothermal modes. Different reactants feeding management strategies were proposed and compared with the aim of achieving enhanced syngas productivity and optimized use of solar energy during solar-aided steam gasification. It was shown that the hybrid mode with partial oxy-combustion of the feedstock and dynamic feeding control results in the most stable process operation upon fluctuating solar power input, while ensuring continuous production of H2 and CO at night and during cloudy periods.

Investigation of a solar-biomass gasification system with the production of methanol and electricity: Thermodynamic, economic and off-design operation

A new solar-biomass gasification polygeneration system is developed to efficiently utilize renewable energy in this work, with the production of liquid fuel methanol and electricity. In the system, the collected high-temperature concentrated solar energy with a beam-down optical configuration is used to drive biomass gasification, the cotton stalk is selected as feedstock, and the produced syngas is fed into the reactor for methanol synthesis. The un-reacted syngas and the system waste heat are efficiently utilized via the combined cycle to generate electricity. The designed biomass consumption rate and power capacities are 100 ktons/year and 32.7 MWe, respectively. The thermodynamic and economic performances of this polygeneration system are investigated, and the on-design energy efficiency and the exergy efficiency of the system reach to 51.89% and 51.23%, respectively. According to the off-design evaluation within a typical year, the annual production of methanol and electricity are 54.80 ktons and 50.85 GW·h, respectively. Compared with the reference system which consists of a typical methanol synthesis system with biomass-steam gasification and a solar tower power generation system, the annual averaged efficiency of the proposed solar-biomass polygeneration system is increased to 48.35% from 41.09% of the reference system, and the monthly averaged efficiency is varying in the range of 46.65%–49.05%. In addition, the specific biomass consumption rate is reduced by 27.33%, and the levelized cost of methanol is 361.88 $/ton with reasonable economic competitiveness. The polygeneration system achieves competitive thermodynamic and economic potential, and provides an alternative and promising way for efficiently utilizing abundant solar energy and biomass resources.

Thermodynamic and economic analysis of a solar-biomass gasification system with the production of methanol and electricity

The thermodynamic and economic performances of a solar-biomass gasification polygeneration system are investigated in this work. In the system, the collected high-temperature concentrated solar energy with a new beam-down optical configuration is used to drive biomass gasification, the cotton stalk is selected as the feedstock, and the produced syngas is fed into a methanol synthesis reactor for methanol production. In addition, the un-reacted syngas and the system waste heat are efficiently utilized via a combined cycle to generate electricity. The designed methanol production and power capacities are 51.2×103 tons/year and 32.7 MWe, respectively. The numerical simulation of the polygeneration system is implemented. The on-design energy efficiency of the system reaches to 51.89% with the exergy efficiency of 51.23%. According to the system off-design evaluation within a typical year, the annual averaged system efficiency is up to 48.35% with the monthly efficiency in a range of 46.65%-49.05%, and the levelized cost of methanol is 361.88 $/ton. The solar-biomass gasification polygeneration system with methanol and electricity production achieve favorable thermodynamic and economic performances, which contributes to reducing CO2 emission and provides an alternative way for efficiently utilizing the abundant renewable energies of solar and biomass resources.

A distributed cogeneration system with a two-stage solar-driven biomass gasifier for heating, power and hydrogen in Northern China

In this work, a cogeneration system with a two-stage solar-driven biomass gasifier is proposed to achieve the multiple outputs, i.e., generating power and heating during the heating period and producing hydrogen during the non-heating period in Northern China. The thermodynamic performances of the system under the design and off-design conditions are investigated. The solar-biomass gasification is divided into two stages, i.e., pyrolysis and gasification in sequence. The mid-temperature solar energy (around 673 K) from parabolic trough collectors is utilized to drive biomass pyrolysis, and the high-temperature solar energy (around 1150 K) from heliostats with point-focus solar collection technology is used to drive the gasification. In the heating period, the gasified syngas as a solar fuel is directly fed into a gas turbine for generating electricity, then a heat recovery steam generator (HRSG) is deployed to produce steams for heating. An energy storage module (i.e. gas tank) is introduced to offset heating at night. The primary energy efficiency of the system is 56.1%, while the rate of stored energy to the syngas based chemical energy is up to 35.66%. The energy storage module weakens the influence of time-varying solar irradiations on system performances, and the steady and efficient utilization of solar energy are achieved. In the non-heating period, the gasified syngas can be converted into hydrogen with the water-gas shift reaction. The above results indicate that the proposed system provides a promising complementary utilization approach of multiple energies (solar energy and biomass) in Northern China.

New solar-biomass power generation system integrated a two-stage gasifier

A new solar-biomass power generation system that integrates a two-stage gasifier is proposed in this paper. In this system, two different types of solar collectors, concentrating solar thermal energy at different temperature levels, are applied to drive solar-biomass thermochemical processes of pyrolysis (at about 643K) and gasification (at about 1150K) for production of solar fuel. The produced solar fuel, namely gasified syngas, is directly utilized by an advanced combined cycle system for power generation. Numerical simulations are implemented to evaluate the on-design and off-design thermodynamic performances of the system. Results indicate that the proposed system can achieve an overall energy efficiency of 27.93% and a net solar-to-electric efficiency of 19.89% under the nominal condition. The proposed two-stage solar-biomass gasification routine exhibits improved system thermodynamic performance compared to that in one-stage gasification technical mode, and the provided heat resource is in a good match with the requirements for the biomass gasification procedure. Under given simulation conditions in this paper, the energy level upgrade ratio in the proposed two-stage solar-biomass gasification system for the introduced solar thermal energy is as high as 32.35% compared to 21.62% in one-stage gasification mode. Meanwhile, the daily average net solar-to-electric efficiency on the representative days reaches to the range of 8.88–19.04%, while that of 9.97–15.71% in one-stage model. The research findings provide a promising approach for efficient utilization of the abundant solar and biomass resources in western China and reduction of CO2 emission.

Investigation of thermodynamic performances for two solar-biomass hybrid combined cycle power generation systems

Two solar-biomass hybrid combined cycle power generation systems are proposed in this work. The first system employs the thermochemical hybrid routine, in which the biomass gasification is driven by the concentrated solar energy, and the gasified syngas as a solar fuel is utilized in a combined cycle for generating power. The second system adopts the thermal integration concept, and the solar energy is directly used to heat the compressed air in the topping Brayton cycle. The thermodynamic performances of the developed systems are investigated under the on-design and off-design conditions. The advantages of the hybrid utilization technical mode are demonstrated. The solar energy can be converted and stored into the chemical fuel by the solar-biomass gasification, with the net solar-to-fuel efficiency of 61.23% and the net solar share of 19.01% under the specific gasification temperature of 1150K. Meanwhile, the proposed system with the solar thermochemical routine shows more favorable behaviors, the annual system overall energy efficiency and the solar-to-electric efficiency reach to 29.36% and 18.49%, while the with thermal integration concept of 28.03% and 15.13%, respectively. The comparison work introduces a promising approach for the efficient utilization of the abundant solar and biomass resources in the western China, and realizes the mitigation of CO2 emission.