Hydrogen as a renewable energy source

[Dave2002]

umslopogaas

I'd guess that the gas in the tank of the first vehicle that stopped was LNG - Liquefied Natural Gas - http://en.wikipedia.org/wiki/Liquefied_natural_gas

This is mostly methane under pressure to reduce the volume, but with some other gases and impurities mixed in.

[Gordon]

...Incidentally, I dont know if there are gas-powered cars in the UK,...

Yes there are. Many taxis have been converted to Liquified Petroleum Gas LPG. A tank sits in the boot. Some petrol stations supply it but not all by any means. It's supposed to be cheaper but the engine has to be modified to burn it.

http://www.thegreencarwebsite.co.uk/blog/index.php/2010/02/12/lpg-conversion-a-helpful-guide/

[Dave2002]

umslopogaas

I'd guess that the gas in the tank of the first vehicle that stopped was LNG - Liquefied Natural Gas - http://en.wikipedia.org/wiki/Liquefied_natural_gas

This is mostly methane under pressure to reduce the volume, but with some other gases and impurities mixed in.

Sorry, I was wrong, and thanks to Gordon for pointing out that most liquefied/compressed gas cars run on LPG - usually a mixture of butane and propane.

There have been prototypes of methane powered cars running with an internal combustion engine -

http://www.bbc.co.uk/news/uk-england-bristol-10881080

http://www.dailymail.co.uk/sciencetech/article-1300546/Dung-Beetle-The-methane-gas-powered-car-leaves-waste.html

Methane can be obtained from waste material, and is sometimes known as Biogas.

Methane can also be used as a fuel for fuel cells. There are several routes. In one the methane is used to generate hydrogen, which is then used as a fuel for a hydrogen fuel cell. It appears that methane can also be used directly as a fuel in some newer types of fuel cell, but these are possibly too experimental at present to be used in practical vehicles.

The energy content of different fuels is given on a table on this page - http://en.wikipedia.org/wiki/Heat_of_combustion - though it's only in terms of energy/weight. Hydrogen comes top, followed by propane, then butane, gasoline, diesel, ethanol etc. What is needed for a vehicle is not only based on energy for a given weight though, but a practical volume for the stored fuel. Gas bag vehicles have been used, in desperation, in the past - http://www.lowtechmagazine.com/2011/...-vehicles.html - isn't there a Dad's army programme which features one?

Reducing the volume of gas fuels presents problems. The gas can either be compressed or liquefied, which increases its effective density - this has to include the weight of the containment vessel, and possibly any cooling equipment needed to maintain the liquid state. An alternative way of using gases is to combine them chemically to form solids which are fairly stable at normal temperatures and pressures, with a release reaction required when the gas is to be used. Fuel cells which can work directly with liquids and solids are an ongoing area of research.

[Gordon]

Brazil has had an ethanol fuel policy for some time:

http://en.wikipedia.org/wiki/Ethanol_fuel_in_Brazil

[Dave2002]

Brazil has had an ethanol fuel policy for some time:
http://en.wikipedia.org/wiki/Ethanol_fuel_in_Brazil

Brazil is rather special, with a large land area, and in a sunny region. I believe it works quite well for them. In the USA moves towards use of ethanol seem to have stalled, as ethanol as a vehicle fuel can, if not done well, lead to a requirement for more energy in, than energy out. OK - there have been farm subsidies, but these have caused problems. There is not much point in moving towards ethanol production if this does not overall reduce other fossil fuel usage, which I think has been the case in the USA.

Brazil has been producing alcohol for cars for years. I believe that it works for them, and does not increase the overall use of other fossil fuels.

I have a friend who told me that in his much younger days he went out with some friends one evening, and returned late at night. They ran out of petrol. It just happened that they had a bottle of whisky in the car, which they poured into the petrol tank, and apparently it got them all home - though the engine ran bit roughly.

I like the fact that in Brazil they apparently mix petrol with the ethanol, not to improve it as a fuel, but to stop people from going down to the petrol station with a few bottles to buy the liquid cheaply to use as chasers later on in the day!

[Eine Alpensinfonie]

Brazil's use of ethanol is dependent upon their policy of clearing vast areas of rainforest for growing sugar.

[Dave2002]

Brazil's use of ethanol is dependent upon their policy of clearing vast areas of rainforest for growing sugar.

Is this strictly correct? I don't know - but if there was a one off clearance of sufficient rainforest to make ethanol production sustainable, then in overall terms that might not be so terrible. I am aware that deforestation in Brazil is bad, but I don't think it's only being done for ethanol production - quite often for very ordinary sounding reasons, and often the wood which is cut down is not used effectively anyway.