Development and analysis of an integrated photovoltaic system for hydrogen and methanol production
Introduction
The main source of energy in today's society is based on fossil fuels. Carbon dioxide, which is one of the main causes of global warming, is released from the combustion of fossil fuels [1]. As a consequence of the greenhouse gas emissions (GHG), the overall average temperature and sea levels have increased by 0.4 K and 15 cm over the twentieth century, respectively. The results of GHG emissions on climate change are now one of the most important challenges facing humanity. It was reported that 40% of all species will be in danger of extinction if insufficient action is taken for GHGs [2].
Fossil fuels have a key role in today's energy policies. More than 75% of global energy demand is supplied by fossil fuels. The increase in the atmospheric carbon dioxide concentration is directly related to fossil fuel use [3]. Three methods can achieve a significant decrease in carbon dioxide emissions:
- •
Enhancement of energy efficiency of equipment;
- •
Investigation of renewable energy sources;
- •
Improvement of carbon capture and storage (CCS) technologies and chemical recycling of carbon dioxide to other valuable fuels, such as methanol [4].
The first approach will not resolve the emission issues completely. The strategy of switching to renewable energy sources at a large scale is not easy to achieve in the short term. The last option may be more probable [5]. Converting carbon dioxide to other valuable materials can be applied from any source of flue gas at existing industry emitters. The production of methanol from exhaust carbon dioxide can be one method to recycle carbon dioxide, which can help reduce the amount of carbon dioxide in the atmosphere.
The usage of carbon dioxide as a carbon source for chemical production and fuel synthesis has been examined previously. The recovery of exhaust carbon dioxide could contribute significantly to reducing climate change [3]. Carbon dioxide can be used as a feedstock in the production of many chemicals.
Although methanol synthesis technology is mature and widely available since 1923, the catalytic synthesis of methanol has attracted most attention from industry, academia, and government. Over the years, many researchers have tried to use efficient catalysts that would support the synthesis reaction [6]. Due to the vast volume of methanol needs in a wide diversity of industrial parts, the scope of commercial production has been increasing. The environmental limitations on the process have also held an essential role in the production of methanol.
Solar and wind energy are exceedingly desirable as renewable energy sources, since they can be readily transformed to electricity by wind turbines and solar cells. Nevertheless, the electricity production from these renewable sources suffers from unstable and fluctuating behaviour. The overall required and supplied solar and wind electricity do not provide a consistent supply, so it requires the utilization of energy storage options.
In this paper, a solar based integrated system for hydrogen and methanol production is investigated. Energy and exergy analyses for each part of the system are conducted. The operating conditions, including temperature, pressure and overpotential, are studied parametrically in order to give a better understanding of the system.
Section snippets
System description
A schematic of a system for solar based methanol production is shown in Fig. 1. Carbon dioxide is extracted from a CO2 capture system. Solar panels are investigated to provide the required electricity for the electrolyser. They are utilized, in order to produce synthetic fuel from a sustainable and renewable source of energy. Part of the required water is supplied by the feedback from the methanol reactor. The supplied water is passed through the chemical reactor, in order to have a role as the
Energy and exergy analyses
Thermodynamic analysis will be performed for three systems, namely:
- •
PV system;
- •
PEM electrolyser; and
- •
methanol synthesis process.
Each system is analysed individually and the results are investigated to evaluate the integrated structure. Thermodynamic analyses are performed for each system. Energy and exergy analyses are performed for the water electrolyser plant. Based on the results from the electrolyser and the amount of carbon dioxide from flue gases, the methanol plant is designed. To observe
Results and discussion
In this section, results will show the effects of temperature and current density on hydrogen production. The analyses related to methanol synthesis at different temperatures and pressures will be conducted in the second part of the section. Based on the optimum point of hydrogen production as well as the available extracted carbon dioxide from the plant, the final designed methanol plant will be modelled and efficiencies related to this designed plant will be studied.
Conclusions
This article presented a new design of a methanol production plant, which is linked with solar based hydrogen production, and analysed thermodynamically in propose a promising engineering system for chemical recycling of carbon dioxide to useful fuels. A solar based integrated system for hydrogen and methanol production was investigated. Energy and exergy analyses of the hydrogen production plant, thermodynamic assessment of a methanol synthesis plant and exergy analysis of the integrated solar
Acknowledgements
The financial support of the Ontario Research Excellence Fund is gratefully acknowledged.
References (23)
- et al.
Methanol or ethanol produced from woody biomass: which is more advantageous?
Bioresour Technol
(January 2010) - et al.
CO2 capture from power plants: part I. A parametric study of the technical performance based on monoethanolamine
Int J Greenh Gas Control
(April 2007) - et al.
Pd-modified Cu-Zn catalysts for methanol synthesis from CO2/H2 mixtures: catalytic structures and performance
J Catal
(2002) - et al.
Thermodynamic assessment of photovoltaic systems
Sol Energy
(August 2009) - et al.
Energy and exergy analyses of electrolytic hydrogen production with molybdenum-oxo catalysts
Int J Hydrogen Energy
(May 2012) - et al.
PEM fuel cell as a membrane reactor
Catal Today
(May 2001) - et al.
Energy and exergy analysis of hydrogen production by a proton exchange membrane (PEM) electrolyzer plant
Energy Convers Manag
(Oct. 2008) - et al.
Methanol synthesis from CO2 and H2: dependence of equilibrium conversions and exit equilibrium concentrations of components on the main process variables
Chem Eng Sci
(1990) - et al.
Performance assessment of an integrated PV/T triple effect cooling system for hydrogen and cooling production
Int J Hydrogen Energy
(August 2011) - et al.
Methanol synthesis from CO2 and H2 over a CuZnO-based multicomponent catalyst
Energy Convers Manag
(1997)