AbstractA new solar-biomass power generation system that integrates a two-stage gasifier is proposed in this work, in which two types of solar collectors are used to provide solar thermal energy with different levels for driving the biomass pyrolysis (about 643K) and gasification (about 1150K), respectively. The qualified syngas produced is fed into the combined cycle system for power generation. The thermodynamic performances of the proposed system are improved with the overall energy efficiency of 26.72% and the net solar-to-electric efficiency of 15.93%. The exergy loss during the solar collection and gasification is reduced by 19.3% compared with the scheme of using one-stage gasifier

Bai, Zhang

Hong, Hui

Jin, Hongguang

Liu, Qibin

Elsevier - Publisher Connector 

Thermodynamics Evaluation of a Solar-biomass Power Generation System Integrated a Two-stage Gasifier 

1876-6102 © 2016 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license 
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of CUE 2015
doi: 10.1016/j.egypro.2016.06.134 
 Energy Procedia  88 ( 2016 )  368 – 374 
ScienceDirect
CUE2015-Applied Energy Symposium and Summit 2015: Low carbon cities and urban 
energy systems 
Thermodynamics evaluation of a solar-biomass power 
generation system integrated a two-stage gasifier 
Zhang Baia,b, Qibin Liua,*, Hui Honga, Hongguang Jina 
a Institute of Engineering Thermophysics, Chinese Academy of Sciences, No.11 North Fourth Ring Road, Beijing 100190, China 
b Uinversity of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China 
Abstract  
A new solar-biomass power generation system that integrates a two-stage gasifier is proposed in this work, in 
which two types of solar collectors are used to provide solar thermal energy with different levels for driving the 
biomass pyrolysis (about 643K) and gasification (about 1150K), respectively. The qualified syngas produced is fed 
into the combined cycle system for power generation. The thermodynamic performances of the proposed system are 
improved with the overall energy efficiency of 26.72% and the net solar-to-electric efficiency of 15.93%. The exergy 
loss during the solar collection and gasification is reduced by 19.3% compared with the scheme of using one-stage 
gasifier.   
 
© 2015 The Authors. Published by Elsevier Ltd.  
Selection and/or peer-review under responsibility of CUE 
 
Keywords: solar energy, power generation, two-stage gasifier, hybrid 
1. Introduction 
Various renewable energies, including solar energy and biomass, are viewed as alternatives for the 
alleviation of the current energy and environment concerns. Moreover, the technical route of solar 
thermochemical is promising to deal with the low energy density and intermittent nature of solar energy [1-3]. 
The concentrating solar energy as the heat source of the high-temperature process can be used to 
drive the biomass-steam gasification, in which the solar thermal energy is converted into the chemical 
energy. Therefore, the solar energy is easily converted to valuable chemicals and low-carbon footprint 
transportation fuels [4-6]. 
In this work, the biomass gasification process is divided into two stages of biomass pyrolysis and char 
gasification. A two-stage gasifier is integrated in the proposed solar-biomass power generation system.  
 
* Corresponding author, Qibin Liu. Tel.: +86-010-82543031; fax: +86-010-82543151. 
E-mail address: qibinliu@mail.etp.ac.cn. 
Available online at www.sciencedirect.com
 2016 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license 
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of CUE 2015
 Zhang Bai et al. /  Energy Procedia  88 ( 2016 )  368 – 374 369
 
Nomenclature 
A Energy level 
E  Exergy 
HHV High heat value 
m Mass flow rate 
P Power 
η Efficiency 
The line-focus solar collectors (LFC) and the point-focus collector (PFC) are used to provide the solar 
thermal energy for driving the gasification process, and the system thermodynamic performances are 
investigated. 
2. System description 
2.1. Physical Properties of Biomass 
The corn straw is an abundant herbaceous biomass resource in China, which is selected as the 
gasification feedstock. The biomass sample of corn straw is collected as follows.  
The pyrolysis experiment of corn straw is firstly conducted, by a program-control electrical furnace, 
with the temperature of lower than 673 K, the tar yield ratio can reach 19.5% as reported in Table 1. The 
chemical composition as air-dry basis of the biomass sample and the char (solid product from pyrolysis) 
are determined and summarized in Table 2.  
Table 1. The product yield of pyrolysis / wt.% 
 Tar Water Char Gas 
Corn straw 19.50 22.13 38.26 20.11 
Table 2 Chemical compositions of the biomass sample 
Sample 
Proximate analysis / wt.%  Ultimate analysis / wt.%  HHV/ 
MJ·kg-1 Mad Aad Vad FCad  Cad Had Nad Sad Oad  
Corn straw 3.94 7.1 69.56 19.39  41.49 6.05 2.35 0.19 38.88  16.51 
Char* 0.36 18.65 22.81 58.18  59.28 3.90 4.60 0.25 12.96  25.67 
* produced by pyrolysis 
2.2. System description 
The new solar-biomass power generation system consists of a solar-assistant biomass gasification 
subsystem and an advanced Brayton–Rankine combined cycle with a SGT-900 type gas turbine, as 
illustrated in Fig. 1. During the gasification process, the biomass pyrolysis is firstly conducted to yield tar 
and char with the temperature of lower than 673 K. Subsequently, the processes of tar crack and char 
gasification are carried out, at the temperature of higher than 1000 K, for producing syngas. 
The biomass gasification reaction heat is provided by the concentrating solar energy. The LFC is 
used to drive the pyrolysis and generate the steam as the gasification agent, meanwhile the PFC with the 
370   Zhang Bai et al. /  Energy Procedia  88 ( 2016 )  368 – 374 
 
beam-down concept is employed for providing the gasification reaction heat. The system operation 
parameters and the design condition are listed in Table 3.  
Table 3. Main assumptions of the system 
Items value 
Gasification temperature & pressure  1150K/18bar 
Pressure ratio (π) 15.3 
Gas turbine inlet temperature (TIT) 1422K 
Primary steam temperature & pressure 764K/56bar 
Low-pressure steam temperature & pressure 533K/6.9bar 
DNI  765 W/m2 
Collection temperature & efficiency of LFC 643K/51.70% 
Collection temperature & efficiency of PFC 1150K/38.71% 
After the condensation and clean-up, the solid particles of ash and other corrosion compositions, like 
H2S, etc., are removed from the syngas produced. The qualified syngas as the gas fuel is fed into the 
power generation unit. The HRSG and the steam turbine installed employ the dual-pressure system 
without a reheat steam configuration. 
Air
HRSG
Solar gasifier
Heliostats
Hyperboloid
reflector
Steam
Turbine
GT
Compressor Combustor
GT
Turbine
Cooling
tower
Condenser
Syngas
clean-up
Biomass
H2O
 
Fig. 1. Schematic diagram of the novel solar-biomass power generation system 
2.3. System evaluation criteria 
The system energy efficiency ηsys and net solar-to-electric efficiency ηsol-elec are used as the overall 
evaluation criteria, which can be formulated as: 
sys solar bio bioP Q HHV mK   / ( )          (1) 
sol-elec ref solarP P QK  ( ) /          (2) 
 Zhang Bai et al. /  Energy Procedia  88 ( 2016 )  368 – 374 371
where, P and Pnet represent the total generated power of the proposed system and the reference system, 
respectively; Qsolar is the collected solar thermal energy; HHV and m are the higher heat value and the 
mass rate for the biomass, respectively. 
Additionally, the EUD (Energy-Utilization Diagrams) method [7] is employed to investigate the 
exergy loss of the system, the exergy balance of the energy-conversion process and the energy level can 
be computed as follows: 
E H T S'  '  '0            (3) 
A E H ' '/              (4) 
3. Results and discussion 
3.1. Energy level upgrade of the solar thermal energy  
In the solar-biomass gasification, the solar thermal energy is used to provide the reaction heat and 
drive the gasification process. And the EUD for the solar-biomass gasification process is illustrated as 
shown in Fig. 2. The EUD is used to graphically show the variations in energy quality and energy 
quantity, the energy donor (Aed) and the energy acceptor (Aea) exist in an energy-transformation process.  
For the typical solar-biomass gasification process with high-temperature solar energy introduced 
(1150K for the case study), the energy level of solar energy can be improved from 0.741 to 0.9 as the 
energy level of the produced syngas. Whereas, if the gasification process is switched to employ the 
proposed two-stage solar-biomass gasification technical mode, in which the pyrolysis and the water 
evaporation processes are driven by the mid-temperature solar energy of 643 K, the energy level of the 
required solar energy is reduced to 0.68, and more energy level upgrade ratio of the solar energy can be 
achieved. In addition, compared to the one-stage gasification mode, the proposed system can converted 
more heat resource of the solar energy into the chemical form, which accounts 9.25% of the required net 
exergy of the solar thermal energy. 
0 50 100
0.0
0.5
1.0
'E
extra
Asolar
A'solar
ATIT
Asyngas
200
A
'H / MW
1.25 Abiomass
 
Fig. 2. The EUD diagram of solar gasification process  
3.2. Thermodynamics analysis of the system 
According to the evaluation criteria, the system performances evaluation with the two two-stage 
solar-biomass gasification concept under the nominal condition is conducted, the energy and exergy 
372   Zhang Bai et al. /  Energy Procedia  88 ( 2016 )  368 – 374 
analysis of the proposed system are summarized in Table 4. The solar energy approximates 51.08% of 
total energy inputs. Correspondingly, due to the inferior collection efficiency of the PFC accompanying 
with more irreversible loss, the largest energy and exergy losses are produced in the solar collection 
process, which accounts for 29.48% and 23.48%, respectively.  
Additionally, the heat loss of the stack gas and the steam condensation contribute to the second 
largest energy loss, which totally take up the proportion of 28.54%. While, for the exergy analysis, the 
second largest energy loss item is generated in the syngas combustion processes, which accounts for 
17.90% of total input. 
Whereas, compared with the scheme of using one-stage gasifier, the proposed solar collection 
system in the work is redesigned with an improvement achieved, the energy loss during this process is 
reduced by 13.81% and exergy loss by 19.3%. 
Table 4. The energy & exergy balance of the system 
 Energy analysis Exergy analysis 
 Energy / MW Ratio / % Exergy / MW Ratio / % 
Biomass 136.37  48.92 145.31 59.86 
Solar energy 142.38  51.08 97.44 40.14  
Total 278.75  100 242.75 100 
 OUTPUT 
Generated Power 74.48  26.72% 74.48 31.53 
 Energy loss / Exergy loss 
Solar collection  82.17  29.48 56.99 23.48 
Gasification unit - - 17.25 7.11 
Gas condensation 27.27  9.78 16.08 6.62 
GT combustor - - 43.45 17.90 
Gas turbine 13.41  4.81 20.22 8.33 
HRSG - - 5.53 2.28 
Exhaust gas loss 27.27  9.78 2.39 0.99 
Steam turbine 0.32  0.11 3.22 1.33 
Condenser 52.30  18.76 2.96 1.22 
Other 1.54  0.55 0.18 0.07 
Total 278.75  100 242.75 100 
3.3. System performance  
The overall energy efficiency ηsys of the proposed system is 26.72%, which can be further improved. 
Firstly, the hyperboloid reflector and the CPC are used for reflecting sun light downward and improving 
the concentrating ratio at the expense of increasing the energy loss, which results in a low collection 
efficiency of the PFC, therefore it can be optimized in the future work. Additionally, the sensible heat 
recovery of syngas is not to be considered in this work. If a part of sensible heat is reutilized for 
evaporating the water (gasification agent), the ηsys can be improved to 29.48%. 
 Zhang Bai et al. /  Energy Procedia  88 ( 2016 )  368 – 374 373
The concentrating solar energy is introduced for driving the biomass gasification, then converted 
into the electricity with a favorable efficiency ηsol-elec of 15.93% under the design condition. ηsol-elec is 
varied with the pressure ratio (π) and the gas turbine inert temperature (TIT) as shown in Fig. 3. 
Compared with the scheme of using one-stage gasifier, an improvement of 1.16~1.42 percentage point is 
achieved in this work.  
6 8 10 12 14 16 18
12
13
14
15
16
17
18
 with one-stage gasifier
 with two-stage gasifier
4
3
2
1
4
3
2
 
h s
ol
-e
le
c
S
1: 1573K   2: 1473K
3: 1373K   4: 1273K
1
TIT
 
Fig. 3. Variation of ηsol-elec versus π and TIT 
4. Conclusions 
A new solar-biomass power generation system integrates a two-stage gasifier is proposed, and the 
thermodymics performances of system are evaluated. The main research findings can be summarized as 
follows: 
(1) The energy level of the concentrating solar thermal energy is upgraded to 0.898 and converted to 
the syngas. by driving the biomass gasification  
(2) The total exergy loss produced in the gasification and solar collection of the proposed system is 
reduced by 19.3%, compared with the scheme with one-stage gasifier. 
(3) The system thermodynamic performances are improved, and the overall energy efficiency and 
the net solar-to-electric efficiency reach to 26.72% and 15.93%, respectively.  
Copyright 
Authors keep full copyright over papers published in Energy Procedia 
Acknowledgements 
The authors appreciate financial support provided by the National Natural Science Foundation of China 
(No.51276214, No.51236008). 
References 
[1] Service RF. Solar fuels. Biomass fuel starts to see the light. Science 2009;326:1474. 
374   Zhang Bai et al. /  Energy Procedia  88 ( 2016 )  368 – 374 
[2] Jacobson MZ. Review of solutions to global warming, air pollution, and energy security. Energ Environ Sci 2009;2:148–73. 
[3] Piatkowski N, Wieckert C, Weimer AW, Steinfeld A. Solar-driven gasification of carbonaceous feedstock-a review. Energ 
Environ Sci 2011;4:73–82. 
[4] Kruesi M, Jovanovic ZR, Steinfeld A. A two-zone solar-driven gasifier concept: Reactor design and experimental evaluation 
with bagasse particles. Fuel 2014;117:680–687. 
[5] Bai Z, Liu Q, Lei J, Li H, Jin H. A polygeneration system for the methanol production and the power generation with the 
solar–biomass thermal gasification. Energy Convers Manage 2015;102:190–201. 
[6] Nzihou A, Flamant G, Stanmore B. Synthetic fuels from biomass using concentrated solar energy – A review. Energy 
2012;42:121–31. 
[7] Ishida M, Kawamura K. Energy and exergy analysis of a chemical process system with distributed parameters based on the 
enthalpy-direction factor diagram. I&EC Process Des Dev 1982;12:690–69. 
 
Biography  
Qibin Liu is a Professor of Engineering Thermophysics at the Chinese Academy of 
Sciences (CAS). Dr. Liu’s current research includes: solar thermal power, solar 
thermochemical technology, and analysis and optimization of energy systems. He has 
published more than 60 research papers. 
 
 


file:///data/remote/core/dit/data/elsevier/pdf/34c/aHR0cDovL2FwaS5lbHNldmllci5jb20vY29udGVudC9hcnRpY2xlL3BpaS9zMTg3NjYxMDIxNjMwMjAyOA==.pdf

Thermodynamics Evaluation of a Solar-biomass Power Generation System Integrated a Two-stage Gasifier

Abstract

Similar works

Full text

Available Versions

Elsevier - Publisher Connector

Elsevier - Publisher Connector