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The more I delve into this topic the more detail I want to address, so rather than cover all three energy storage options in this post I’ve decided to give a more detailed look at hydrogen. Keep a look out for a look at compressed air and battery electric in the next two weeks. Hydrogen is the darling of the media, car manufacturers and oil companies alike. The general public seems fairly convinced that hydrogen vehicles are going to be the way of the future and a simple replacement for oil. Just about every car manufacturer has done at least a fuel cell concept, if not a ‘production ready model’ or even consumer testing. Hydrogen can be filled up in more or less the same way as conventional cars meaning that consumers can continue in their established transport patterns. It can be produced from a variety of different sources including electricity and has the potential to be created with zero emissions. Best of all the only thing to come out of the tailpipe of a fuel cell vehicle is water vapour.But is hydrogen really the miracle cure for oil dependence and transport environmental damage that everyone thinks it is?

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As a preface, the first thing that needs to be noted in answering that question is that hydrogen, unlike petroleum or natural gas, is not actually a fuel source, it is just an energy carrier. We can’t mine, harvest or extract hydrogen from the earth; we have to make it ourselves. That means we need to put energy in to make hydrogen so we can get it back out again in our cars. The problem with that is that it isn’t a very efficient or necessarily green process and that’s not the only obstacle, Popular Mechanics lists 4 major hurdles for hydrogen to become the fuel that powers our transport needs:
At present the vast majority of hydrogen production uses heat and pressure to extract hydrogen from natural gas. The process uses fossil fuels, energy for the heat and pressure and releases CO2. So the hydrogen produced can hardly be called green. The cheapest alternative method to produce the 150 million tons of hydrogen required to replace current passenger cars is coal gasification. Costing around US$500 billion, the process would produce 600 million tons of CO2. The cheapest CO2 free way of doing it would be nuclear at $840 billion and requiring 2000 next generation reactors compared to the 103 existing nuclear power stations in the US. If you covered an area greater than California in wind generators you could match current fuel prices after the 3 trillion dollar setup cost. Pretty much any replacement for oil is going to take similar scale investment (for example Battery Electric Vehicles would require about 50% of these estimates) but you get an idea of the scope of the change that needs to happen for us to replace our current transport situation.
I’m going to try and keep the next two short but you can read more about them here. Hydrogen is light, giving it quite a good energy to weight ratio of 3 times that of natural gas. The problem is that it is also not very dense, even if cooled to the point where it turns into a liquid you would still require three times as much space as an equivalent gas (petrol) tank. If compressed to 10,000 psi, 250 times more pressure than your average tires, you would need 4-5 times the amount of space for a tank for the same range as an equivalent petrol car. There are also certain materials which can absorb and release hydrogen but they are heavy and expensive.
Trucking it will take 11% of the energy in each load just for the truck. Pipelines cost about a $1 000 000 per mile. Small scale on site production via electrolysis or natural gas is less efficient than large scale but could potentially be the best of the not very good options. Or in the distant future in car production may be possible though it would be using up our aluminium reserves.
You can use hydrogen in an internal combustion engine and get about a 25% better fuel economy than traditional ICE’s. Considering ICE cars are only 20-25% efficient anyway we’re not getting much bang for our buck. Fuel Cells can bump this to 45% total efficiency with light duty but this drops to 36% under high loads. Not to mention that Fuel Cells are so expensive that Ballard, a leading fuel cell researcher for the past 25 years worth 600 million has abandoned its fuel cell program as prohibitively expensive. The Wall Street Journal even quoted Toyota and GM big-shots implying that fuel cells were too expensive for any near term production, though the manufacturers have played down those comments. But even with the efficiency of Fuel Cells the total well to wheel efficiency of hydrogen cars ends up at around 17-22%. When compared to electric vehicles, hybrids or even efficient petrol or diesel cars this is not very smart use of energy, especially considering the scale of implementing such a system, discussed above.

Perhaps the biggest thing we can use to evaluate the effectiveness of fuel is its well to wheel efficiency, if not its availability or cost viability. Hydrogen vehicles are not the best option on any of these counts. Their efficiency fails to compete with the other options. When they would be widely available is anyone’s guess; GM says a decade , The EU suggests 2030, but some have guessed up to 100 years, not to mention the chicken and the egg car and distribution problem. And as we saw in the last paragraph hydrogen cars are prohibitively expensive with fuel cells and not very efficient as an ICE. I fail to see where all the enthusiasm stems from for hydrogen cars, people just don’t seem to be aware of the numbers. When you look at the facts, H2 cars are too wasteful, too expensive and too far away.
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