Professor Sati N Bhattacharya Director, Rheology and Materials Processing Centre School of Civil and Chemical Engineering RMIT University 124 Latrobe St, Melbourne, Australia Tel: 613 9925 2086 Fax: 613 9925 2268 Email: Satinath.Bhattacharya@rmit.edu.au
Review on Hydrogen Research
Mr.Arindam Banerjee has developed a conceptual framework for the creation of a hydrogen economy in the Australian context. His report analyses the potential benefits of a hydrogen economy(economic and environmental). It highlights the fact that Australia could not only meet its increasing energy demands but at the same time become a world leader in taking initiative to move towards green technologies for energy generation and consumption. Since hydrogen storage is a challenge the above mentioned idea directly looks at use of piping network for transportation of hydrogen. Based on this novel framework developed by Mr. Banerjee the following report looks at the technical challenges associated with making the hydrogen economy a reality.
The Hydrogen economy is one of the probable green technology based solutions which could replace the oil driven economies looking at future environmental concerns. Scientifically an optimized hydrogen economy would operate with zero carbon emissions and produce soft water as a by product making it an lucrative solution. This fact is further validated by the amount of funding allocated for the development of a hydrogen economy globally. A lot of technical and economic challenges exist before the concept of a hydrogen economy can be put to commercial use. The following review outlines various project stages involved in making the hydrogen economy a reality in the Australian context.
Challenges in a hydrogen economy:
The major challenges involved in developing an hydrogen economy are as follows
1) Selection of proper technologies for production of hydrogen
2) Design of a piping network for transportation of hydrogen in gaseous or in liquid form Design of valves and compressors for transportation of hydrogen.
3) Design of valves , compressors and sensors for transportation of hydrogen.
4) Thermodynamic studies on hydrogen energy cycle for generation of electricity
5) Cost optimization studies to make the project as cheap as possible.
Selection of proper technologies for production of hydrogen:
There are three basic procedures for generation of hydrogen they are Electrolysis by use of direct current, generation of hydrogen via a fuel cell and finally generation of hydrogen from fossil fuel sources. Among these technologies direct route electrolysis is energy intensive compared to others but at the same time is pollution free. The generation of hydrogen by fuel cell technology (microbial sources can be used) is cost effective but the power generation rate is comparatively lower as compared to direct electrolysis. Finally the last method is to use fossil fuel sources which is relatively expensive as compared to fuel cell technologies and has higher carbon emissions as well but it provides a relatively stable throughput. The procedure for generation of hydrogen would be actually a optimized mix of all the three mentioned technologies with cost, geographic location, and carbon emission as boundary conditions for a optimization problem. Also further research and development in this area could lead to improvement in efficiency and throughput rates for fuel cell technologies resulting in economies of scale with respect to fuel cell technologies.
Design of a piping network for transportation of hydrogen in gaseous or in liquid form
The piping of natural gas using steel pipes is a well known technology. A lot of research has been put in to understanding the economics of piping of hydrogen using existing technology. The literature suggests that the piping of hydrogen is going to at least 50% more expensive as compared to natural gas due to the following reason.
Firstly Hydrogen is more corrosive as compared to natural gas. The problem of hydrogen embitterment due to hydrogen corrosion and documented .So the cost of hydrogen resistant pipes is going to costlier using conventional technologies for transportation like say steel pipes. Secondly special fittings and valves have to be designed using the conventional piping mechanism to eliminate hydrogen permeation which would further increase the cost. Finally handling of specially designed pipes and valves would result in increased labour costs which would further add on. It has been proved in the literature that the major cost in laying a piping network is the labour cost and hence is an important factor.
There are other possible research alternatives to eliminate this problem and make the piping of hydrogen more sustainable and cheaper probably comparable or even cheaper as compared to pumping natural gas or other fuel gases. The possible research in this area will be discussed later in the report. Also the cost of pumping hydrogen like other forms of energy is dependent on the geographic location and the demand which result in economies of scale.
Design of valves, compressors and sensors for transportation of hydrogen
The design of valves, compressors, connecting ports and sensors are very important for the use of a piping network in an hydrogen economy. The reason being that the use of special materials for hydrogen transportation would require special accessories as well. Further the sensitivity of the valve also needs to be optimized as per the energy load. The current gas compressions systems need to be modifies considering the corrosive nature of hydrogen as compared to natural gas or steam. Also the liquefaction of hydrogen will take place at much higher pressures and lower temperatures changing the overall efficiency of the compression cycle. Hence design studies of the accessories to be used are very important for the success of a hydrogen economy.
Thermodynamic efficiency of hydrogen energy cycle for generation of electricity
It has been known since ages that the Carnot cycle is the best thermodynamic cycle for generation of energy and hence is the bench mark for any kind of thermodynamic studies. The reason being that a Carnot cycle is a completely reversible cycle and operates infinitesimally slowly maintaining reversibility of the process at every stage. All other commercially used energy cycles cannot be operated so slowly and are not completely reversible. Hence the efficiency of any other commercially used energy generation cycle will always be lesser than an idealized Carnot cycle. The conversion efficiency of a fuel cell under idealized conditions can be higher or equal to Carnot cycle but the overall efficiency of energy conversion i.e. hydrogen - electricity - hydrogen can never be greater than a idealized Carnot cycle. Though there is sufficient literature in this area the claims need to be verified experimentally. Also further studies on the conversion efficiency of hydrogen - electricity - hydrogen need to be calculated experimentally and suitable thermodynamic models need to be developed before actually commercializing.
Cost optimization studies on hydrogen generation and supply
The generation and supply of hydrogen has to be cost effective in the sense approximately at least equal to the case of a gas electricity generation system to make it economically competitive. Also the additional benefits of using hydrogen as compared to conventional technologies will make the proposition even more effective. The key to cost optimization is to develop and select suitable technologies for generation and transportation of hydrogen. The possible research projects to reduce the generation and transportation cost of hydrogen will be discussed further in this report.
Project planning and scheduling:
The diagram below illustrates the various stages involved and the time lines required for development of a workable model for use of hydrogen energy. The overall project would require around 6.5 - 7 years before it can be commercially converted in to a real time system. Also with sufficient amount of manpower and funding the time scale of lab scale studies can be reduced suitably.
Role of Rheology and Material processing Centre (RMPC): (Example proposal)
Proposal 1: The design of hydrogen transmission piping networks using polymer nanocomposites.
The transmission of hydrogen using conventional steel pipes is not a viable solution since hydrogen is highly corrosive (hydrogen embrittlement). Also the rate of permeation of hydrogen from the conventional pipes is very high. The cost of laying specially designed steel pipes is very high making hydrogen transmission uneconomical as compared to natural gas. Development of reinforced polymeric composites with reduced permeability is a good alternative to be used .The use of such composites will not only eliminate the problem of hydrogen corrosion and embrittlement at the same time make it cost effective and comparable to that of natural gas transmission. Such a kind of project has been taken up by the Argonne research lab in USA.Once a suitable material is selected then a piping network design can be made and sensors can be incorporated in to the system to monitor flow rates and pressure of hydrogen inside the pipes .Once the piping network has been designed then hydrodynamic and thermodynamic modelling of hydrogen flow through the pipes becomes very essential since this will help in determining the suitable points for installing compression ports . Also further work would be to incorporate valves and joining ports with in the piping system. Then this network can be used commercially.
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