Below are pages 1-7 only of the third(3rd) report(15pages).
High Schools in New South Wales.
(H2 & Fuel Cell Science & Technology Education)-Yr 2003 / 4)
*In accordance with the NSW Office of The Board of Studies the following subjects could facilitate hydrogen and fuel cell science / technology education for students.
Ø Industrial Technology:
*Engineering and automotive focus. - 1
*Renewable and/or alternative energy sources - 2
Ø Design & Technology:
*Specific project focus. - 3
Ø New Science:
*Students could engage in investigating fuel cell technologies. - 4
*Historical and current research, applications and implications of
technological developments for science, society, and the environment. - 5
Ø Module 9. 2 Stage 6 chemistry;
*Structure and chemistry of a dry cell or lead acid battery plus one other
type of cell. Students must present the cost, practicality, and impact on
society and the environment of each cell type.- 6
Teachers can develop units of learning within their power and control, so students get the opportunity to embrace such new and emerging technologies. Basic fuel cell science
In 1839 Sir William Grove was electrolysing water using platinum electrodes. When he turned off the power source he noticed a current flowing in the opposite direction. The platinum electrodes had absorbed some hydrogen and oxygen respectfully, and then the hydrogen was oxidised (by giving up its electrons). The electrons flowed over to the now platinum cathode where oxygen was waiting. Sir William called the cell a “Gas Battery”.
Towards the end of the 19th century, the German physical chemist Wilhelm Ostwald demonstrated that fuel cells were more efficient than the internal combustion engine. He went on to predict that the 20th century would be “the Age of electrochemical combustion”.
Several decades passed before further development was done on the fuel cell. The above picture shows Francis Bacon working in his laboratory in 1955.The Bacon Cell used hydrogen with an alkaline electrolyte; it was the first practical fuel cell demonstrated. Bacon used porous sintered nickel powder for the electrodes, so the gas could diffuse through to reach the electrolyte.The space race was intensifying at about the time Bacon’s cell was becoming world known. The space program needed good power supply sources for space exploration. The Bacon cell was modified for the 1960’s Gemini space program to supply power and water for space travel.
The above picture represents Space Shuttle Orbiter’s fuel cell power plant. It produces 12kW of electricity, weighs 98kg and occupies 154 litres.
4 & 5 The “gas battery” of 1839 by Sir William Grove had no conducting electrolyte between the electrodes. The cell however managed a small current to be detected as mentioned earlier. For a fuel cell to be effective as with the Bacon Cell, an electrolyte must be present so ions can move through the electrolyte to facilitate a flow of electrons (electricity) through the connecting wire between the electrodes. A flow of charged particles (ions) in an electrolyte is not electricity, but allows for electricity to be generated.The electrolyte is a chemical compound dissolved into water and is referred to sometimes as being aqueous with the symbol (aq.). The electrolyte is carefully chosen knowing what gases are going to be applied to the electrodes, and consequently the chemical reactions that will happen.The Bacon Cell showed that with an electrolyte (liquid), as long as hydrogen and oxygen were supplied, an electrical current would be generated. This now represented a significant breakthrough, as the chemical energy within the hydrogen and oxygen gases were being converted to electrical energy, as with a flow of electrons in the wire between the electrodes. Such electricity produced from the chemical energy within the hydrogen and oxygen can of course power an electric motor, light bulb or even a spacecraft.
The fuel cell is like a battery but batteries are very heavy and they do not last very long. A battery does store chemical energy within, and does produce electricity when the battery is connected in a circuit. Small batteries are used everywhere in the world today in many electronic devices, but a battery cannot power a building, spacecraft or car effectively. To reuse the rechargeable battery, it must be recharged with electrical energy from a power socket. A battery powered car does not last very long as it runs out of power after 60-80 Kls, and then needs charging for hours. The space program of 1960’s and onwards showed how fuel cell technology could be relied upon by the space program to supply continuous high quality power whilst the fuel was supplied. The by-product of the PEM fuel cell is ultra-pure water (H2O).
Looking at the fuel cell at this time scientists and engineers pondered on whether they could find a solid electrolyte material to conduct the charged particles (ions) in the fuel cell. The reason is that if a solid material could be found it could allow for a small complete fuel cell unit, which then would allow a “stack” of them to be put together to get much greater electrical output.A compact single fuel cell then in a “stack” configuration would allow for the possible usage of the fuel cell to power a car or a bus.The solid electrolyte called the “membrane” is the ion conducting material which allows for the flow of electrons between the electrodes.
Above: The first modern PEM fuel cell of the late 1980’s.
Below: Early applications of the PEM fuel cell stacks.
1989 -The fuel cell stack at the left had a power density of 100watts/litre.
1996 -The fuel cell stack at the far right had a power density of 1100watts/litre.
Thus from 1989 to 1996 the power output per size of the stack increased over ten (10) times.
Below: Applications of PEM fuel cell stacks below show NECAR 2 of 1996 much smaller than NECAR 1 of 1994,due to the fuel cell stack’s improved power to size ratio.
NECAR (1) 1994 NECAR (2) 1996
We have now come to understand the fundamental developments of the fuel cell from the beginning. The modern fuel cell with a membrane (solid electrolyte-Proton Exchange Membrane [PEM]) has allowed for the anticipated applications as above. The focus from the early 1990’s has been to improve efficiency and reduce the cost of the fuel cell.
The membrane in the above diagram is called Nafion® and the H+ ion is cleary visible as being conducted through the membrane (solid electrolyte). Notice how close all three layers are together. In fact an interface between the gas/membrane/catalyst is essential for the MEA to operate. The interface must happen at both electrodes as above.The membrane material being Nafion® is a material produced by Dupont, and compared to earlier solid electrolytes, lasts thousands of hours before it deteriorates. However good Nafion® is, it is still expensive to make at around US$700 / m2 .As well the catalytic material coating the electrodes is very expensive being that of platinum. The electrodes being carbon cloth and or paper are porous and are relatively inexpensive.
Platinum, rhodium and ruthenium are all metals which are used in PEM fuel cells. Platinum is ~US$13,500/kg and rhodium about ~US$33,000/kg. These metals all have at least one of their ions, an incomplete d-sub-level of electrons, with s- and p-sub-levels within easy reach. Electron pairs can thus be donated by reacting gases into the vacant orbitals in the metal atoms or ions. All this means is that there is a good chance chemical bonds will be formed with the catalyst layer and the gases.The metal-hydrogen (M-H) bond at the catalyst layer cannot be too strong nor too weak. If the bond is too strong the reaction surface would become blocked and nothing else could react to keep the fuel cell going. If the M-H bond were too weak, then nothing would happen at all in the first place. If we look at the M-H bond strengths for iron, cobalt, copper, silver and gold, these bond strengths are too weak. For niobium, tantalum, molybdenum and tungsten, the bond strengths are too strong.
The platinum metals are thus still the best choice as catalysts for overcoming the activation energy barrier in electrochemical reactions, involving hydrogen and oxygen. Modern PEM fuel cells now work efficiently with about .1mg cm-2 of platinum at the anode. This achievement is a twenty-fold improvement over the earlier PEM fuel cells of the 1990’s.
The MEA is the heart of the PEM fuel cell and much work is currently being done to find cheaper and thinner membranes whilst maintaining durability. The reduction of oxygen at the cathode does require high activation energy and is a major cause of voltage losses. However, platinum loadings of .3mg/cm-2 are currently being achieved for the cathode. As for the anode, platinum loadings of .1mg/cm-2 are being achieved.
The PEM fuel cell has other components as above which hold the MEA in position within a fuel cell stack assembly. The end plates and bipolar plates are as well areas where costs can be reduced. The material used for these plates has been graphite and stainless steel, which both need machining to achieve shape and gas flow channels. Newer plates are being used that are a graphite-resin which uses molds, so the plates can be made faster and cheaper without machining them.
Non-platinum catalysts are as well being researched around the world at present so platinum group metals do not have to be used in the future. This would make the fuel cell even cheaper, although platinum levels have dropped dramatically over recent times. Different membranes have been discovered in years 2003 and 2004 by US and Japanese companies, which they say will drop the cost of manufacturing the new and more efficient membranes by up to 90% within eighteen months. A major tool that is being used in the world of research and development today in the area of fuel cells is nanotechnology. Nanotechnology is the study of materials and their behaviours at the nano-scale of a metre. Material science and the study of these materials more generally, are of course going to grow dramatically in the near future.
Western Australia has hydrogen fuel cell buses operating in Perth as of the 12.09.04,as part of a global trial. Micro-fuel cells are to power 19.5 million laptop computers, mobile phones and other small electronic devices by year 2014.Stationary fuel cells will power housing in Japan in year 2008 and the mass production of the fuel cell vehicle is planned for year 2015.
NECAR 4 generates 75hp(55kW) with top speed of 140 k/hr.
It can travel 450 Kls on a single tank of hydrogen gas and emits
Hoku Scientific has developed a new low operating temperature membrane with the potential to outperform Nafion® and other leading membranes used in PEM fuel cells. The Hoku Membrane™ has fundamental design advantages over these technologies, affording it substantially lower production costs while actually increasing system performance. Furthermore, this new membrane design offers more favourable results than other membranes with regards to temperature stability, proton conductivity, and humidity sensitivity. Performance advantages are achieved by using alternative materials that have a higher propensity for conducting protons while maintaining thermal stability. These materials are economical to produce and can be assembled with relatively inexpensive procedures such as tape casting.
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Stephen V. Zorbas(1995-2013)