Written by Frank Hare
The first thing to understand about hydrogen is that it not a basic energy source. It is a conversion product requiring the expenditure of other energy to extract hydrogen from water or natural gas. Whether one uses natural gas or electrolysis of water to obtain hydrogen, energy is lost by as much as 65% by the time one gets to reconvert the hydrogen back into electricity in the fuel cell. One ready hydrogen source is the Sun, but we can comfortably rule that out for now.
In the USA there is in being The California Fuel Cell Partnership which includes eight motor manufacturers including Ford, Toyota, and General Motors. The intention is to develop hydrogen powered vehicles, yet at the same time compete with each other. A somewhat tricky situation indeed. They all operate in one building where they have their own service area, which in essence means that they are all developing their own design but with common technology regarding the application of the hydrogen power source.
The hydrogen is not burnt as with other fuels, but is used to power a fuel cell which in turn produces electricity to drive an electric motor. This of course is not new technology as hydrogen suppliers will tell you. Enquiries as long ago as 1960 seeking to get hydrogen into cars was being bandied about, but then the relatively cheap oil based fuels were never under threat from an unproven technology, so the status quo remained. It wasn’t till world politics, followed by the hike in oil prices in the 1970’s that things began to change. From the 1980’s to the present day the word environment has had quite a different emphasis. In the mean-while hydrogen was being used in many chemical processes including the hydrogenation of margarine as an example.
Hydrogen is notoriously difficult to store and as liquid is a non starter in relation to the motor car due to the ultra low temperature of the gas which has to be sustained. We are therefore dealing with a gaseous fuel which is highly flammable and difficult to smell or see when alight. Clearly designers have to be certain of the safety aspects at all costs.
At this point one can see the reasons for the long period of development which is being estimated before we see production quantities coming off the conveyor belt and onto the roads.
In these columns we have highlighted various experimental vehicles using hydrogen technology across the globe, most of which are of the hybrid design. In the dim distant past there have been vehicles using hydrogen as a fuel, with a large bag of hydrogen on the roof. However the Hindenberg crash put paid to that idea.
These hybrid cars use both fossil fuels and fuel cell technology. Running primarily on petrol or diesel alongside an electric motor which is battery sourced, being charged during braking and long even spells of driving. The motor cuts-in in slow traffic, which is especially useful in urban travel, being silent and pollution free. Notably Honda and Toyota sell such vehicles today with over 100,000 already on the road between them. But the ultimate aim is the hydrogen only powered vehicle, being manufactured in production line quantities and at a price we can all afford. This is what the The California Fuel Cell Partnership is all about.
So how will the hydrogen only vehicle work?
Stored hydrogen under pressure is pumped into a ‘cell’ constructed from fibres called proton exchange membranes. A ‘cell’ like a battery, has positive and negative electrodes (anode and cathode). The hydrogen is supplied to the negatively charged cathode, where a chemical catalyst strips away electrons from the hydrogen atoms. Electricity is generated when these electrons flow across the anode. The remaining positively charged hydrogen atoms called ions, diffuse across a special membrane to react with oxygen from the air to produce water. The cell uses the hydrogen to generate 86 kilowatts of electric power which can be stored in a capacitor or used immediately.
The California experimentation will have to answer some difficult questions.
- Will the ‘cell’ last for 150,000 miles?
- Where will we refuel?
- Will the fuelling station be safe for the public to handle?
- Will the public accept the new technology?
- Can hydrogen be produced in quantities that make the retail price acceptable?
The present filling stations handing petroleum fuels are, as we all know, businesses offering not just fuel. Any move to hydrogen will have to be sustained by similar set ups to maintain the facilities that we have come to expect. In other words, keep the forecourt as the centre of fuelling, whatever that fuel is.
We should not expect quick answers. The transition to sole hydrogen tech-nology is some way off; maybe as long as 20 years. Nobody can say exactly, but the fact is we are on our way. So we had better get used to the idea.