University of Alabama, Birmingham
PEM electrolysis for production of hydrogen from renewable sources
Critical Review 2
CE 674 - Green Building Design and Sustainable Construction
July 25, 2016'
Bibliography: Bibliography: Barbir, F. (2005). PEM electrolysis for production of hydrogen from renewable energy sources. Solar Energy, 78(5), 661'669. doi:10.1016/j.solener.2004.09.003 In-line Citation: (Barbir, 2005)
In this publication, the author makes a case for using a hydrogen electrolizer as a component of energy production. The significance here is to fill in where other sources of energy may be inaccessible, intermittent, or as an option for off-grid operation. Several constructs of each are discussed and evaluated.
As an authority on the subject, Dr. Barbir covers the inner workings of a proton exchange membrane (PEM) electrolysis system. He describes the operation and possible uses, limitations and economics of such a system. He does not advocate that these are to be stand-alone systems, rather to be an integral component of a total power generation package. This could be a combination of photovoltaics (PV), standard grid, or wind. These systems can be used as a stand-alone system, but if it is as a cleaner option, a power source used to run a system must also be green as well.
Dr. Barbir finds that certain situations, such as remote locations, off-grid systems or grid-supported systems may be able to maximize the use of green power, given that the hydrogen created can either be stored, shipped or piped for use. Since hydrogen can be stored, a PV system can supply electric needs and run the hydrogen generator (HG). Once the sun goes down, the hydrogen can be used to continue operations. It seems that there may be a niche for such a device, but a narrow one since these are generally expensive.
The article shows on Google Scholar to have been cited 490 times and 6 versions available. Many of the articles first on the list are either research paper related to similar systems, or analysis on emerging technologies. Special terminology used isn't necessarily defined including 'PEM'.
About the Author
Dr. Frano Barbir has spent more than a half of his 25-year engineering career directly involved in development of PEM fuel cells and fuel cell systems. He led the teams that designed and built fuel cells and fuel cell systems and put them in practical applications. He is the author or co-author of more than 140 publications on fuel cells and hydrogen energy, published in technical and scientific journals, books, encyclopedias and conference proceedings. He is also co-inventor on several fuel cell related patents.
Dr. Barbir is currently a professor at the University of Split, in Split, Croatia. He is faculty of the electrical, and mechanical engineering and naval architecture; chair for the thermodynamics, thermotechnics and thermal engines. He also serves as a senior consultant to the United Nations Industrial Development Organization - the International Centre for Hydrogen Energy Technologies (UNIDO-ICHET).
The audience here can be of any technical background. However, most likely, this is aimed at technical persons interested in power generation. They will also be looking for solutions for alternative fuels and combination systems. These individuals will likely be searching for specific pieces of equipment that will fit niche situations allowing for better reliability in a type of system requiring a second or third source rely on to match the kind of reliability typical of the grid. If these systems are to be integrated into electric generation packages, the reader must appreciate the concepts proposed, even if not to the same technical depth as the author.
Since this is a developing technology with few manufacturers, economics is a big consideration. Due to the additional cost of purchase, installation and operational design, these systems currently work best in remote locations, or if the cost of grid electricity is sufficiently high. PV combined with PEM electrolysis systems currently show the most promise for getting the most for the dollar. Other alternative fuels options for powering the unit are hydroelectric power and wind power. As long as the primary alternative fuel power source is relatively steady, the HG can make up for the fluxuations experienced with wind and solar power.
Research in this area has potential, but like many proposed ideas, development must occur. Dr. Barbir is attempting to make a small bridge in this to shore up some of the short-comings of some other more developed sustainable electric generation sources such as wind, solar or lower grid reliance. If there is a limited source or no source, these kinds of systems could definitely add a viable option where none exists.
The author has invested decades of his life in the support of studying the application of hydrogen power. He notes that hydrogen can be used in just like fossil fuels without the same kind of pollutants emitted. He also advocates that the conversion process to other forms can be more readily and easily done compared to petroleum. Since hydrogen is not naturally occurring in nature, it is more of akin to electricity, which must be produced for use. It can then be generated, moved if necessary, and then used on site. His analysis is from a sustainability perspective between hydrogen, electricity and renewable energy sources, with water being the feedstock to the HG.
Finally, the cost and generation of hydrogen can be expensive using traditional grid electricity. The efficiency of conversion is fairly efficient at greater than 70% which makes the choice expensive. Others, according to citations by Dr. Barbir, have suggested that hydroelectric or nuclear power could be used during off-peak hours. Still other research suggests the use of large PV plants cold be utilized and then piped or shipped to the point of use. PV plants can be viable if the cost of solar panels are around $0.2 to $0.4/W.
The Method: PEM Electrolysis
Dr. Barbir describes the differences between a PEM electrolysis and a PEM fuel cell. While schematically looking very similar as shown, they actually work in opposite directions. This schematic gives a good relative sense of operation upon close inspection. The construction of both is also very similar. The PEM fuel cell performs more like a battery running on hydrogen, while the PEM electrolysis system works to release hydrogen from water.
The application here is for power demand where no grid source is available. In this section the author covers the different types of set ups using different arrangements of power sources, with and without grid supply. The variations suggested by the author are PV, wind, PEM fuel cell systems as a source of electric output. A PV or wind system can be set up to be the sole source of power or they can both be used at the same time. This set up will take the demand completely off grid, and adding a PEM electrolysis as the secondary power to stabilize the supply. For additional support a PEM fuel cell could also be added as another source of electricity
Since this is a developing technology with few manufacturers, economics is a big consideration. Due to the additional cost of purchase, installation and operational design, these systems currently work best in remote locations, or if the cost of grid electricity is sufficiently high. PV combined with PEM electrolysis systems currently show the most promise for getting the most for the dollar. The most efficient design he points to is keeping the HG operating in a constant steady state. Other alternative fuels options for powering the unit are hydroelectric power and wind power. As long as the primary alternative fuel power source is relatively steady, the HG can make up for the fluxuations experienced with wind and solar power.
Finally, an amazing suggestion for application is unmanned aircraft. The author cites research being done that would place solar panels on the wings and a PEM electrolysis system onboard. The hydrogen would then be stored in the wings of the aircraft. The benefit claimed is that the aircraft could stay airborne without having to land for fuel. The application suggested here is to replace satellite systems. He maintains that this set up could be less than the price of a satellite, and discusses the issue of weight. What I don't find mentioned is the additional equipment that a typical satellite is equipped. A similar suggestion is to use these in space for orbiting satellites.
First noted is the size of the PV/PEM electrolysis system. To get the most out of the HG, it must be running at a steady state near maximum capacity. The best way for this to be done is to undersize the HG compared to the PV array. The remainder of the solar generated electricity could be used with the excess being wasted or going to the grid, if connected to one. An additional option is to add batteries to store the excess energy.
Under a direct one to one sizing in a PV/hydrogen generator set up is that the solar panels operate in fluxuations with the sun. HG work best under steady-state condition, and make best economic sense. The generator requires a certain input to operate effectively. At some point in the operation of a HG may build up hydrogen, but will not permeate the gas across the membrane which can create a safety hazard. Intermitted or variable power also interferes with the operating temperature. The hydrogen generator works best at the optimum design temperature. A variable power source would not allow for a generator to run at the best design temperature.
An HG can be designed to produce hydrogen at a required pressure, then stored in pressurized tanks. With proper design to adjust for the pressurized system, the only apparent loss seems to be the hydrogen loss across the membrane. This design can be used to provide stored hydrogen for pipelines, automobiles or tanks. The oxygen that is produced can be stored and later used but requires special safety considerations.
As with any other design, customer needs and capital investment must be considered with regards to efficiency. An HG will produce more hydrogen at higher pressure, but do so less efficiently. If efficiency takes precedent, a lower voltage can be used but will be more expensive. In efficiency also occurs across the membrane particularly at higher pressures.
Power matching and auxiliary equipment impact the efficiency of the HG. If the source power is variable, significant efficiency is lost. At a steady-state power input with DC/DC voltage regulators the efficiency can be as high as 93% or higher. However, this occurs within a very narrow range even with tuned PV sources.
The final design concern of interest mentioned by the author is performance degradation over time. Dr. Barbir states that the voltage over time must increase along with a graph that shows this, he ends by saying degradation can be minimized. Initially, the HG will require higher voltages to stabilize. This is akin to a break-in period. Design considerations must be given to these changes so as to properly size an HG for use.
Dr. Barbir concludes that these PEM electrolysis systems are a viable option to be paired particularly with PVs. He also notes that this is currently not a large scale solution as an alternative fuel, but rather as an additional support to alternative fuels where none other exist. While he does mention other possible uses such as rockets or satellites, he recognizes that the cost of a PV system, the HG, and economics must be considered. For those special situations, this could serve as a great option to support industry needs for power.
The writing style at first seemed a bit fundamental and lacking some clarity. Although the doctor may be functional if not fluent in the English language, it took me several reads to grasp what he was saying. There are also some typographical errors that were over looked. The sentence structure seemed a bit erratic causing me to have to reread the sentence first, without the additional information in parenthesis to get the point. Then go back and read in the additional information. Most of the graphs and basic schematics were helpful but it seemed at the end times he contradicted them. He states that the voltage over time increases and that the end of life performance must be considered for efficiency or generation rate. He then concludes that this can be minimized. If I had to consider this as an option, I'm not quite sure which situation would prevail, although a safe bet would be to go with end of lifecycle expectations.
Dr. Barbir at times keeps the level of discussion high and I felt like he needed to describe or define certain aspects better to improve understanding. For those who might be interested in this emerging technology will likely not be as versed as he in the subject matter. This would help give design engineers considering options a better handle on how these might serve power demands in special cases.
Regardless of the shortcomings, there is quality information provided. It can lead those interested in such technologies
I have been interested in alternate sources of energy.
Bio collected from: Who is Who in Croatian Science, Web.
Frano Barbir: Scientist details (2003) Available at: http://tkojetko.irb.hr/en/znanstvenikDetalji.php?sifznan=9106&podaci=biografija (Accessed: 17 July 2016).
Bibliography: FRANO BARBIR, Ph.D. (1999, March ). Retrieved July 17, 2016, from http://marjan.fesb.hr/~fbarbir/ In-line Citation: ('FRANO BARBIR, Ph.D,' 1999) from web.
Web: Hydrogen Generator - G4800. (n.d.). Retrieved July 17, 2016, from http://fuelcellstore.com/hydrogen-equipment/hydrogen-production-electrolyzers/hydrogen-generator-g4800
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