24 replies to this topic

[digger]

Here is a very similar development.

http://www.lightningcarcompany.com/

Interesting, I wonder what the price will be?

I for one am looking forward to mainstream electric cars, not because they are any greener but because they have fantastic performance potential.

I agree fuel cells are a red herring for cars:-
generate electric
convert to hydrogen (lossy)
compress/liquefy/convert to methanol? (lossy)
distribute by road (mmm lossy)
high pressure/cryogenic storage (mmm)
charge high pressure hydrogen tank in my car (mm and mmmmm)
convert back to electric (lossy)

much better to just distribute across the existing national grid network even though there is a loss associated with this(I know it will require somewhat of an upgrade to deal with the extra demand, plus a few more power stations to say the least).

[spectrum]

How strange that this subject should appear on a pyrotechnic forum!!!! Even stranger is the amount of interest shown - fantastic actually.

I have been canvassing an idea around by coincidence:

Electric bicycles suffer from 2 problems - range and speed - these are caused by the inability to strap a big enough motor to the frame and, even more importantly, the weight of the batteries which would ideally supply sufficient power to turn them and keep them turning for long enough, i.e. deliver range.

Now what about a mini trailer attached to the rear of the bicycle aupporting this lot - the bike frame isn't man enough - the trailer actually powers the bike along by pushing it and contains the batteries and a small generator to recharge them when they get low.

The advantage is that such a contraption would still be a lot cheaper than any other form of travel, would not require insurance or road tax and would be cheap to replace - when the bike is knackerred you chuck it away and attach the trailer to another bike.

Opinion would be welcomed - am I mad - should I stick to pyro's

[digger]

How strange that this subject should appear on a pyrotechnic forum!!!! Even stranger is the amount of interest shown - fantastic actually.

I have been canvassing an idea around by coincidence:

Electric bicycles suffer from 2 problems - range and speed - these are caused by the inability to strap a big enough motor to the frame and, even more importantly, the weight of the batteries which would ideally supply sufficient power to turn them and keep them turning for long enough, i.e. deliver range.

Now what about a mini trailer attached to the rear of the bicycle aupporting this lot - the bike frame isn't man enough - the trailer actually powers the bike along by pushing it and contains the batteries and a small generator to recharge them when they get low.

The advantage is that such a contraption would still be a lot cheaper than any other form of travel, would not require insurance or road tax and would be cheap to replace - when the bike is knackerred you chuck it away and attach the trailer to another bike.

Opinion would be welcomed - am I mad - should I stick to pyro's

What sort of range would you expect an electric bike to require 20 - 25 miles? We have a few people who come to work on electric bikes; ok they are sort of a combination affair electric + pedals.

What speed were you looking for? I believe that the maximum speed allowed in law is 15mph, any faster and it is classed as a motor vehicle requiring tax, insurance, licence etc. So I am sure there must be some pretty small motors now available to achieve that speed (as a moped is only 3hp and they can do 30+mph).

I think there will be a few problems associated with generators, such as extra weight, size, low charging speed (unless it is a decent size). I think the best approach is to look at some of the more interesting new battery options that are becoming available (as Andrew has lain out).

[Andrew]

What speed were you looking for? I believe that the maximum speed allowed in law is 15mph, any faster and it is classed as a motor vehicle requiring tax, insurance, licence etc.

This has some interesting ramifications as far as mopeds go. As the 15mph refers to the maximum driven speed. As we all know, you can quite easily approach speeds of 30mph on a push bike. I used to average just over 30mph on an 80 mile round trip to work (well only the return leg; as there is a slight gradient assist). The 15mph "power" can be applied at all times, assisting your top speed to well over 30mph for even an occasional cyclist.

Here lies a loophole, how to police assisted cycles (technically mopeds)? You cannot effectively stop every assisted cycle and check that it's top speed unassisted is less than 15mph. Even if you did, being the designer you can easily rig it to limit speed to 15mph if there is no external accelerating force! Even so, what defines the limit, a fat bastard wearing a parachute would need several kW to reach 15mph. When you are cycling at the same time there is no true measure of how much power being put in by the motor and the cyclist themselves! This confusion gives rise to the ability to increase the power output and stay legal as long as you are peddling too, reason being, there is no hard "Power" or more importantly Torque legal limit, only an unassisted top speed limit. However taking the piss and nipping down the shops at 60 would probably land you in the s*it. You probably could get away with being cheeky though.



For the surprise explanation. Don't be too shocked. What did you expect? Many people who post on the forum are academics with technical backgrounds ranging from geology to rocket science, chuckle! Your bound to have someone who knows a bit about just about everything you could ask about. Your always likely to get an enthusiastic answer on this forum and other forums alike because most people here are into 'being interested in technology'.

[digger]

Just on a quick side note Andrew, what do think of the hydrazine fuel cells that don't require platinum?

[spectrum]

What sort of range would you expect an electric bike to require 20 - 25 miles? We have a few people who come to work on electric bikes; ok they are sort of a combination affair electric + pedals.

What speed were you looking for? I believe that the maximum speed allowed in law is 15mph, any faster and it is classed as a motor vehicle requiring tax, insurance, licence etc. So I am sure there must be some pretty small motors now available to achieve that speed (as a moped is only 3hp and they can do 30+mph).

I think there will be a few problems associated with generators, such as extra weight, size, low charging speed (unless it is a decent size). I think the best approach is to look at some of the more interesting new battery options that are becoming available (as Andrew has lain out).

To answer your questions:

1. Range - certainly much more than 25 - 30 miles. The rane is limited to around this figure normally I believe because of the difficulties in strapping batteries to a lightweight bicycle frame. If the batteries (which determine the range) can be mounted on an independent platform, i.e. a trailer, then in theory the range can be increased without burdening the frame of the bike. if you can attach a generator too then the range could be vastly increased, maybe limitless subject to the generator keeping up with the demands of the batteries / vehicle.

2. Top speed - 15mph is the limit I understand, I am not sure what tolerance applies, but as much as can be legally achieved.

3. Generator weight - is this a problem?, I would like to think that having addressed the matter with the batteries, the same solution may be applied to the generator.

I think the design should address the following factors, in this order:

1. Range
2. Power - accelleration perhaps more than top speed - again this is something which
can be achieved through carrying the additional load on an independent body.
3. Serviceability - the design should be such that every component can be easily
replaced, so Lead / Acid batteries, commercial run-silent generator etc. The fact
that bikes are so cheap nowadays means that the unit can be kept far longer than
the bike, when the bike is knackered chuck it away and transfer the trailer to a
new one.

The feature of a trailer is attractive I believe because it makes the whole package more versatile in that it can carry a load, unlike a commonplace electric bike - the workings being hidden inside.

[starseeker]

Point on interest. Did you know that you can get 700W motors that are an inch in diameter and an inch and a half long, that are 95%+ efficient and have no brushes?

The day of the electric car came and went (well was assassinated by the US). But it's coming back, faster than you might think!

Would these motors be the brushless type used for model car racing etc,?

[Andrew]

Yes your right. These brushless motors are commonly found as model motors. These days you can get brushless motors that have powers of hundreds of kilowatts that fit into the hub of a car wheel, they are about the size of a disk break!

Hydrazine = dead. It is very very toxic. Look at the bottle the wrong way and it will kill you! Added to this Hydrazine is almost hypergolic with air. As you probably know already it's not the safest of chemicals. Some Soviet re-entry capsules used Hydrazine in the land break motors. The cosmonauts needed to stay inside for an hour or so to allow the Hydrazine to get to safe levels before exiting. There are vast areas of the south American rainforests that are devoid of life after Hydrazine fuelled rocket failures on the pad.

Hydrazine will not make it to mainstream cars any time soon as fuel because of the safety reasons. If it's generation in situ could be mastered AND it could be guaranteed that there would be no releases into the environment then it may be considered. Even then, the generation in situ means carrying along a load of other chemicals and water = loads more weight. This in turn will lead to a more expensive system that is difficult to maintain and probably has an energy density far below that of lead acid batteries! I think that hydrazine fuel cells will only find a place in common fuel space missions any time in the near future.

[digger]

Hydrazine = dead. It is very very toxic. Look at the bottle the wrong way and it will kill you! Added to this Hydrazine is almost hypergolic with air. As you probably know already it's not the safest of chemicals. Some Soviet re-entry capsules used Hydrazine in the land break motors. The cosmonauts needed to stay inside for an hour or so to allow the Hydrazine to get to safe levels before exiting. There are vast areas of the south American rainforests that are devoid of life after Hydrazine fuelled rocket failures on the pad.

Hydrazine will not make it to mainstream cars any time soon as fuel because of the safety reasons. If it's generation in situ could be mastered AND it could be guaranteed that there would be no releases into the environment then it may be considered. Even then, the generation in situ means carrying along a load of other chemicals and water = loads more weight. This in turn will lead to a more expensive system that is difficult to maintain and probably has an energy density far below that of lead acid batteries! I think that hydrazine fuel cells will only find a place in common fuel space missions any time in the near future.

So you don't think the Daihatsu polymer storage technology will reduce some of these risks by storing the Hydrazine as Hydrazone in a granulised polymer? (my initial thoughts were I don't want hydrazine or its hydrate anywhere near me in a vehicle). HYPERMEC catalysts are delivering a peak power of 700 mW/cm2 this tech. Ref the Engineer 14-27 Jan issue.

[Andrew]

So you don't think the Daihatsu polymer storage technology will reduce some of these risks by storing the Hydrazine as Hydrazone in a granulised polymer?

As I said

Hydrazine will not make it to mainstream cars any time soon as fuel because of the safety reasons.

If it's generation in situ could be mastered AND it could be guaranteed that there would be no releases into the environment then it may be considered.

This is a tall order.

HYPERMEC catalysts are delivering a peak power of 700 mW/cm2 this tech.

The power density of the cells is not of concern here. It is mostly the energy density of the fuel that is important! (both by volume and mass). As long as the power density of the cells is reasonable it's OK. Carrying Hydrazine gives you a fantastic energy density.

Hydrazine has a molecular weight of 32g/mol, but to make it in-situ you need one mol of Hydrazone and two mols of water (plus an excess and chemicals to make the conditions right for hydrolysis). The most basic Hydrazone has a molecular weight of 88g/mol + 2 of water at an extra 36g. So to get one mol of Hydrazine to need at least 130g of material giving a mass efficiency of just 18%. The energy density of Hydrazine is 19.5MJ/kg when used 100% efficiently in a fuel cell. We now only have 18% of this to give an adjusted usuable energy density of just 3.6MJ/kg. To put this into perspective petrol is about 40MJ/kg. Even taking into account the 30% efficiency of a petrol engine, it still pulls Hydrazine's pants down.