The WFC car myth.
When steam engines were originally introduced, their power output was rated as the number of horses the engine replaced. Over the years the term 'horsepower' has been misused and now has several meanings. Brake horsepower, for example is the engine horsepower without the losses caused by the gear box, differential, generator / alternator, water pump, power steering etc. However, since a practical ICE (Internal Combustion Engine) powered vehicle must have these items, the same losses exist for both petrol, Diesel and hydrogen engine powered vehicles. In practice one can expect the Wheel horsepower to be about 10 - 20% lower than the Brake horsepower (BHP), in a well designed vehicle.
Mechanical to electrical power conversion.
One 'mechanical horsepower', or one 'electrical horsepower' is equal to about 746 Watts. The 'metric horsepower'. is equal to about 735 watts . For the purposes of this article we will use the 'mechanical watt' and assume that one horsepower equates to 746 watts ( 745.69987158227022 W, exactly !).
Horsepower required for small family car ?.
Small family cars generally use engines in the 90 - 130 BHP range. However I would like you to think about the very lowest BHP one could use ... and it has been suggested that it is 15 BHP !. If you disagree, that is fine with me .... just use the BHP of your own car.
Next we need to convert the 15 horsepower to watts .....
Watts = 15 BHP x 746
= 11,190 watts or 11.19 kilo watts
Vehicle voltage systems.
Most modern small vehicles us a 12 volt system, and using that we can calculate the total number of amps the vehicles alternator is going to have to supply for the above wattage.
Amps = Watts / volts
= 11190/ 12
= 932.5 amps.
At this stage your sphincters should start to twitch ......... because a VW Golf, for example has an alternator rated at only 70 - 90 amps !. I also suspect that it isn't a continuous rating either !.
Some may say "what about the energy already in the vehicle battery", which is probably rated at about 40 ampere hours. Assuming the alternator can provide 90 amps without melting .... that would mean the battery would have to provide ....
932.5 amps - 90 amps = 842.5 amps.
If the battery did not explode ... it would be completely discharged in ...
40 AH / 842.5 amps = 0.0474777 hours or 2.8 minutes.
Ah ..... but what about over unity ?.
I have seen no evidence that anyone has ever got a water fuel cell to work at over unity !. A few people have claimed that they have done it .... so let us have a look at some of those claims. I have no wish to embarrass anyone, so I will not mention any names. The efficiencies claimed ....
Case 1. Classical Meyer replication. x3
Case 2 PWM Meyer setup Group effort x5
Case 3 PWM, no inductors, 12v eht x9
Case 4 Calculated from Meyers patent WO 9207861 x16
The next question is .... assuming that the above is true .... what over unity efficiency do we really need to reduce the power load required to acceptable levels ?. This really depends on what range we want and that in turn translates into time. So let us assume we want to do a one hour trip before we need to recharge the vehicle battery from an external power source.
Using a 40 AH battery at a one hour discharge rate ... would only allow us to draw 40 amps from the battery !. My question to you is where is the other 802.5 amps going to come from ?. I will let you calculate the over unity efficiency required.
If we had 11.19 KW of electrical power available on our vehicle for 'on demand' hydrogen generation, then the most efficient way of using it, would be to discard the inefficient petrol engine, petrol tank and most of the gearbox and drive train and replace it with an electric motor and PWM speed control. Electric motors are 2.5 times more efficient than the internal combustion engine !.
Ok, now we will briefly consider a real small car that uses a 130 BHP engine, which translates into .......
130BHP x 746 = 96850 watts
With a 12 volt system this would require a current of ....
96850w / 12v = 8070 amps !
As you can see things are getting ever so slightly crazy .... and we still have not considered the losses between the engine output shaft and the road !. So what does this all mean ?. To provide that kind of power would require ..... 201 standard 40 AH batteries car on board to provide to power the vehicle for one hour. Of course they would weigh quite a bit so you would need a large truck to carry them around ..... and that would need a much larger engine .... so that means more batteries and so on.
Of course I could have made a mistake. If so, please email me and I will make corrections
1. Even 20 years ago the USA produced 35,000,000,000 cubic feet of Hydrogen per year. The most common commercial method of producing hydrogen is to remove it from Hydrocarbons, such as methane, petrol, fuel oil and crude oil. As oil producing countries hit peak oil we may find that they will turn off the tap ... and save what is left for their own use.
2. Most 'free' energy from wind and water turbines, wave action and solar panels ends up as electrical energy and it makes sense to use it in that form.
3. The average journey in Europe varies by county between 6 - 15 km. In UK the average journey is 10 km (6 miles). 80% of UK car journeys are less than 8 km. 33% of UK journeys are below 2 km.
75% of the CO emitted during a journey happens in the first km. This then tails to a minimum at a rate dependant upon the speed at which it is driven. At urban speeds it can be between 5 - 10 km at motorway speeds it can be up to 30 km . This means that 60 - 70% of the total mileage in UK occurs without the car ever having warmed up to the minimum emission level.
Another factor is the size of car and number of occupants per journey. Obviously it is wasteful for one person to travel to work in a vehicle designed for four people. There is obvious scope here for a small single ,or two person electric vehicle. Employers could provide free recharging points, at the place of employment.
4. In my humble opinion, water fuel cells have a place in this world ... but do not solve the vehicle fuel crisis or global warming.
Copyright John Kent July 2008