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Electric and Alternative Vehicle Fuels


As far as I can tell, there’s little difference environmentally between the hardware of a battery and a fuel cell. That’s canvassed in this post.

Where they differ is in full-cycle efficiency:

Environmentally, compressed-air hardware is likely to be relatively benign. Simple mechanical stuff, made from pretty prosaic materials that should be readily recycled. The carbon fibre tanks might present some challenges though.

What makes you think they haven’t tested the vehicle(s)?

Given the limitations, I’m surprised that anyone thinks there’s a market for compressed-air vehicles. More than one commercial enterprise seems to believe there is. Like hydrogen, inefficiency is evidently not the problem I think it is. I must be missing something


Sometimes efficiency is not a relevant metric. I learnt this decades ago when I did some development for a remote computer installation. That particular computer was terrible or worse performing the particular application (that is irrelevant for this discussion) and used gobs of electricity and esoteric cooling. I queried the cost vs the use. The reply was that the location was remote, the computer had another primary use but could get ‘the job’ done, and it was uneconomic, unsafe and impractical to send any physical items out of the remote district. Result, the primary job and ‘my job’ got done within the constraints. Efficiency was not a consideration.

In 1981 a major oil company installed a supercomputer (about $10 million + $2.5 million installation!) for a single intensive application whereby the machine ran at 12% efficiency. The board of directors was ecstatic because prior to that installation the application running on the most powerful general purpose computer of the times could rarely complete in a timely manner or before it crashed. The company literally used the application to make $250 million decisions. All 1980’s currency.

Although computer use is not fuel efficiency, I suggest the analogy to fuel efficiency is relevant because an outcome can be good regardless of efficiency getting there. If fuel X is easy and cheap to produce and store, all the bits are plentiful and renewable, it is easy to transport, use, and delivers enough power, why is efficiency important in its own right, other than as an academic discussion (that admittedly might lead to better efficiency, that would be an incremental profit issue).


Quite so. But are there any applications for the air motor where its other advantages outweigh its inefficiency and the combination of features and efficiency is better than alternatives such as battery?

The Di Pietro engine site gives these examples:

  • workshop or indoor transport
  • motorbike
  • lawn mower
  • go-kart
  • small car
  • sailing boat power assist
  • engineering test rig

Nothing jumps out a me.

Although, for those who must have beverage while they work, if you could power a ride on mower you could have a cooled drink cup as a selling point as existing ones only have uncooled cups.


Perhaps. Is it irrelevant in the context of vehicular transport?

Does the Tata design use Di Pietro technology?


I suspect the CAC (compressed air car) has been tested and the results are underwhelming. Until they are published they do not exist as evidence.

There are also records to be set which is a good way to gain promotion for your brand. None yet by the French project. Perhaps too Toyota are secretly working on a competitor?

The science behind the science if you are interested in petrol vs battery vs compressed air. Noted that the article is from 2009, so the relative battery weights may now be less. Basic physics and thermodynamic laws have not changed.

A reasonable suspicion is having maximised the range for the air storage by minimising the vehicle weight and using carbon fibre pressure vessels there are only a few remaining obstacles. Aside from cost!
One might be that they are trying to create a better air motor with high efficiency. And one that is durable and does not consume or leak lubricating oil! Whale oil used to be the go to. These days there are a range of synthetic hydrocarbon based and silicon oils.

The overall concept has considerable scope to provide additional benefits to offset inefficiencies. Aside from free cooling in the vehicle from the expansion of the air used, the compression of the air used in the supply produces large amounts of waste heat. This could be used in industrial processes, domestically for hot water or with a Peltier device recover some electrical power. It may be useful to keep an open mind.

Atmospheric propulsion of underground railways was a nineteenth century invention that was commercialised (briefly). It failed largely due to the primitive design leather based seals not being up to the task. It was as an aside also not very energy efficient, but enough to make it work. Today there are visions of high speed travel in evacuated tubes. It’s not necessarily the science that’s holds solutions back.


A neighbour next to our previous home had a lathe and he was in the process of constructing miniature steam engines from scrap metal.

He had finished the actual engines but had not constructed the boilers prior to them moving and selling the lathe.

He demonstrated the operation of the dual piston engine by connecting the steam inlet to a line from his air compressor.

It operated at an astonishing speed which would have probably put the Flying Scotsman to shame.


Tata is apparently using MDI technology.
The company has great expectations.


There’s only two - 0-100 km/h and 400 m time. If alternate fuel can give me ~2.5s and <10s respectively for <20k$ I’m in :wink:


ahh, so not quite as fast as a bicycle* :wink: Not very impressive at all!

*Todd Reichert on a faired recumbent bicycle in 2016: 144.17 km/h (89.58 mph) -0.6% grade[9], unpaced


An alternative with a few downsides:
From one of the comments:
“Test at Auburn university showed my vehicle to be 37 % more efficient fueled with wood vs gasoline
According to Auburn the vehicle is 67% environmentally cleaner than a totally electric car and net carbon neutral ( if charged from the Alabama grid )”


Apologies beforehand but since this is getting a bit to the edge there is more than ample hot air emanating from Canberra to power any number of high power air driven vehicles. And then there is hay.

‘The average thousand-pound horse who relies on hay for all their forage typically eats fifteen to twenty pounds of hay per day.’

Hay is roughly $0.90/kg online. Taken as $6.00 a day. The horse can go 80-100 km per day, say $0.06 per km. For @draughtrider the 400m seems about 13 seconds. All rough and rounded.

If time and temperament are not of the essence hay seems like it could be a goer.


On a slightly different note, when I visited the Motorola Museum at their headquarters in Chicago as part of a tour in in 1993, I was surprised to learn that one of their first products were automobile gasoline heaters.

Certainly something that definitely required an alternative energy source.



Then again:
" the predecessor of the auto was also a major polluter. The faithful, friendly horse was charged with creating the very problems today attributed to the automobile: air contaminants harmful to health, noxious odors, and noise."


This thread is about fuels, not pollution. That is off topic :laughing:


Every fuel has its :thinking: emissions.


Hopefully the mind can be open to alternate suggestions.

Not necessarily. Doesn’t it depend on exactly what the predecessor to the automobile has been eating as to how off?
Some parts of the world did recycle such pollution as a fuel after solar processing. A possible early example of renewable green energy.

Although this is more of an alternate vehicle solution than just about an alternate fuel. The fuel meets the key criteria of being a renewable, green and sustainable.

Back in the 21st century.
Would it be appropriate to consider that we may see a number of different options for transport fuels come into prominence? There are separate needs for power and range depending on each use. Each may be better served by swapping to the most suitable solution for the task? Today’s one size fits all motor vehicles are an inefficient solution most of the time. They survive relatively unchanged because they are low cost when compared with need, versatility and usefulness?

Is it useful to also consider the best match between vehicle type and design for a usage against the fuel or propulsion options?

Given the rise of the Uber and autonomous vehicles, a drop off at the tavern down the road using a light weight lower powered vehicle should be cheaper to use than a four seater with luggage better suited to the cross town airport run?

May it also be that in the near future we do not need every solution to be super efficient or zero carbon? if a retrofit can transform some of our vehicles rather than replacement is that acceptable? And if it halves the carbon production is that still Ok as a half step rather than waiting for a solution that is still to be provided


You are into the realm of the vehicle’s emissions, not the fuel’s, although the dots can be connected. Left to its own chemistry, no vehicle included, hay seems pretty eco friendly. Compare it to the petrol [et al] cycle from exploration to production to use. :laughing:

You made good points :slight_smile:


I’m not sure there is a way to close that loop without the horse choking … and either way, one horse is still only approximately (varying according to the various definitions of horsepower) a horsepower of one … my steel horse has nearly 200 times that, and while not perfect, is far less cantankerous than the horse I once owned :wink: Efficiency is no contest …


Totally off-topic but, in an earlier incarnation, what’s now called “trickle-down economics” was known as “horse and sparrow”. The idea was that, if the horse was fed enough grain, then some would pass through for the sparrows to eat. To paraphrase Marie Antoinette: "Let them eat "- well, you get the idea.


Not really. It depends if in looking at alternative fuels you choose to prioritise direct economic outcomes (CO2 emissions excluded) or climate change (CO2e reduction benefits).

A third choice is to ignore both as transport is an enabling technology and the end justifies the means. There is no need to consider either. Style, power and noise are all enabling features to be considered ahead of cost.

This may help to explain the recent spin from the Prime Minister for Marketing and references to any 26%-28% reduction in greenhouse gas emissions only mentioning the electricity sector. Perhaps only the domestic consumption portion? Nothing about transport.

The heavy lifting if it is to be done in transport appears to also have been left to the consumer. Pick a fuel, pick a new technology. Even Brisbane’s bus fleet which had a signficant CNG (Natural Gas) powered fleet has moved back to diesel power!

Technology aside the economic considerations appear to be still in favour of no change. A liquid fuel whether hydrogen at pressure, ammonia, electrolytes or similar that offers easy quick refueling would appear to be the easy option. If it offers better power that is great. If it is lower cost that is great. If it offers better power, convenience and low cost does the carbon footprint matter? Probably very little to a market economy.

In a market economy the alternatives to petroleum and diesel fuels will need to compete against the untaxed cost of these products. That the cartel in oil supply can as it chooses up volume and lower prices is demonstrated in recent history. Just how low they will go before they cease production might be the key factor in how cheap alternative fuels need to be. This is very cheap given the alternatives need varying amounts of investment in new technology and distribution.

On one count electric battery power has an edge other than the very expensive battery technology and weight penalties.
On the other hydrogen fuel whether for fuel cells or a multicylce combustion heat recovery system appears an easier drop in to existing vehicle designs.

Neither (personal view) are green low carbon solutions. How well they meet the criteria of low carbon depends on how the fuel source is produced and the environmental overhead of manufacture of each.

In looking for other options it is easy to find other already developed and more sustainable alternatives including bipedal motion and circular bipedal motion. If only you could get carbon credits for using them? Currently the average bipedal motor under Australian operating conditions produces 22t annually of CO2e greenhouse gases. Annually over 10,000km that’s approx 220gm/km or slightly worse than a Toyota Prius. There is plenty of upside though if you look at other users.

Notably in the UK the average bipedal motor under similar conditions produces approx 7t annually of CO2e. It’s not clear if this is due to low mileage, differences in energy production (more kippers?), or the weather? Some of the Scandinavian nations extract even better performance, although France still leads the way with endurance testing.