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Author Topic: The problem with gasoline-electric vehicles:  (Read 4300 times)

Offline Atomic-S

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The problem with gasoline-electric vehicles:
« on: 28/05/2006 02:49:54 »
is that altthough gasoline-electrics may save fuel, they do not necessarily save money. Aside from the high initial cost (at present at least), there is the little problem of what happens when their all-important batteries quit. Those batteries are much larger than those in a conventional vehicle, and much more expensive. When they have to be replaced, I wonder if the owner will actually be saving money over the long term, or not.

What to do?  Well, why not eliminate the battery? Although it is difficult to store electricity without one, Who says we are limnited to electrical energy?

For example consider the gasoline-pneumatic option. Instead of the battery, a tank. During times of light demand or braking, the engine or brakes would drive a pump compressing air into the tank. During heavy demand, the pump would be reversed and act as an auxiliary engine.

Tanks have an avantage over batteries in that they are probably cheaper and probably last a lot longer.

But there are certain possible difficulties: How big a tank would be needed, and/or how high a pressure.  However, the effective size of a tank can be increased chemically, if it is filled with an absorbent medium that has an affinity for the gas being compressed. The system that is most obvious is water and carbon dioxide. usefully, a ready source of carbon dioxide is available: The vehicle's own exhaust.


 

another_someone

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Re: The problem with gasoline-electric vehicles:
« Reply #1 on: 28/05/2006 14:37:21 »
The tendency these days is to move from chemical batteries towards ultra-capacitors.  This is still very new technology, and I imagine still very full of holes, but can deliver massive amounts of peek power.

The problem I can assume with compressing gas is how to limit the amount of loss of energy through adiabatic heating as the gas is compressed.

Beyond that, you also have to take into account the massive weight that a pressure vassal may add to the weight of the vehicle.



George
« Last Edit: 28/05/2006 14:39:28 by another_someone »
 

Offline Atomic-S

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Re: The problem with gasoline-electric vehicles:
« Reply #2 on: 31/05/2006 04:00:25 »
quote:
The tendency these days is to move from chemical batteries towards ultra-capacitors. This is still very new technology, and I imagine still very full of holes, but can deliver massive amounts of peek power
Interesting. I wonder what sorts of quantities of energy these things can store. The only ones I am familiar with are limited to a few volts.

quote:
The problem I can assume with compressing gas is how to limit the amount of loss of energy through adiabatic heating as the gas is compressed.
If the tank is thermally insulated (preferably internally), this would not be a problem.
quote:
Beyond that, you also have to take into account the massive weight that a pressure vassal may add to the weight of the vehicle.
As compared to what? Lead-acid batteries?
 

 

another_someone

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Re: The problem with gasoline-electric vehicles:
« Reply #3 on: 31/05/2006 22:28:23 »
quote:
Originally posted by Atomic-S

quote:
The tendency these days is to move from chemical batteries towards ultra-capacitors. This is still very new technology, and I imagine still very full of holes, but can deliver massive amounts of peek power
Interesting. I wonder what sorts of quantities of energy these things can store. The only ones I am familiar with are limited to a few volts.



Power and voltage and energy are three different things.

At present, a single comercial ultracapacitor can be charged up to 2.7 volts, but they are small devices, and it is quite easy to place many of them in series to increase the total voltage.

The thing you are really concerned with are energy densities (i.e. how many volts x amps x seconds you can store in a given volume).

At present, as measured in weight rather than volume (although I imagine roughly the same will be true of volume), ultracapators are not yet at the same capacity in terms of energy density that chemical batteries, but they have much higher peak power capabilities, and are still a very immature technology that has a lot of potential for future improvement.

http://www.maxwell.com/ultracapacitors/applications/ise.html
quote:

ISE Corporation Case Study



The depletion of natural resources, air pollution and the rocketing price of gas are all issues that impact the automotive industry. Fortunately, something is being done about it. “Transportation for a clean planet” is the motto of the ISE Corporation, which has been building hybrid and electric vehicles since 1996.
A privately held company, ISE Corporation was founded in 1994 by David Mazaika and Michael Simon in San Diego, California. ISE produces Integrated Hybrid Drive Systems, vehicle prototypes and engineering services. Its mission is to become the leading supplier, developer and service provider of electric, hybrid-electric and fuel cell vehicle components, subsystems and drive systems. Thus far, it has successfully integrated dozens of prototype and demonstration vehicles encompassing more than ten different bus, truck and tractor models.
 
The Problem

ISE's Hybrid Electric Vehicle (HEV) technology combines the best characteristics of fuel-driven engines, electric motor drives and energy storage components. Their solution has been designed with a combustion engine that functions as the primary power source, and an electric motor with a power storage system that functions as the secondary power source. Designers are able to size the combustion engine for cruising power requirements thanks to the presence of the secondary power source that handles the peak power demands for acceleration. Additionally, regenerative braking energy is captured by the secondary power system and that energy is applied for further acceleration or for the basic energy needs of supplementary electrical systems by using the secondary source.
Using only batteries to provide the electrical power storage has drawbacks in the hybrid application. These deficiencies are multiple, and they create many design challenges for automotive engineers. Firstly, batteries have difficulty functioning in cold weather. Secondly, batteries require a sophisticated charge equalization management. Thirdly, batteries have limited cycle life under extreme conditions, which results in high cost replacement throughout the life of the vehicle. A new battery has to be purchased and installed; the old battery has to be removed and disposed. Battery disposal can be problematic unless the manufacturer has a recycling program. All of this adds to the cost of a battery-based system.
Perhaps most importantly though, batteries are limited in their ability to capture and provide bursts of high power during short duration events such as acceleration and regenerative braking. This high power limitation reduces the efficiency of the hybrid electric drive system design.
 
The Solution

ISE's solution to the above stated problems has been to think beyond batteries; to the reliable technology of ultracapacitors. An ultracapacitor can fulfill many of the functions of batteries in this application, but with dramatically higher reliability and overall performance.
Compared to batteries, the key benefits offered by BOOSTCAP ultracapacitors are as follows.
Ultracapacitors function well in cold weather, down to –40° Celsius, whereas, without heating, batteries do not operate reliably below 0° degrees Celsius.
Ultracapacitors are a safe solution as a pack with equalization is discharged over night.
Ultracapacitors have a long life cycle, basically built to last the lifetime of the machine into which they are incorporated and as they are maintenance-free, that ultimately results in cost savings.
Ultracapacitors are more efficient than batteries; 84-95% as compared to an average of below 70% for batteries in this application as measured by ISE.
Ultracapacitors are very earth-friendly as they are 70% recyclable and do not include any heavy metals which are detrimental to the environment.
Ultracapacitors offer up to 10x the power of batteries and in terms of acceleration of a vehicle, this plays an important role.
Following is a comparison of a specialized, heated ZEBRA battery solution also used by ISE Corporation as compared to their proprietary Thunderpack II ultracapacitor solution.
 
Code: [Select]
                            ZEBRA Battery Pack    Thunderpack II
                                                 Ultracapacitor Pack
Typical Usable Energy               18kWh                  0.3 kWh
Charge and Discharge Current        32kW              Over 150 kW
Energy Density                      87 Wh/kg                 4 Wh/kg
Power Density                       0.16kW/kg               1.5kW/kg
Expected Life                   2.5-5 year             10-12 years
System Cost                       375 $/kW               100 $/kW
Life Cycle Cost                 $1125/kW                 100$/Kw

As is clearly seen, batteries have high energy capability while the ultracapacitors have high power capability. In an optimal hybrid storage system, both technologies would be combined in a way to maximize the benefits of both.



http://www.doc.ic.ac.uk/~mpj01/ise2grp/energystorage_report/node9.html
quote:

Applications


Supercapacitors were initially used by the US military to start the engines of tanks and submarines. Most applications nowadays are in the field of hybrid vehicles and handheld electronic devices.
NASA has a research project to use supercapacitors in an electric bus called the Hybrid Electric Transit Bus. The energy used to start the engine and accelerate the bus is regenerated from braking. During test runs, a bus loaded with 30 supercapacitors, each of them weighing 32 kg and releasing energy of 50 kJ at 200 V managed to run for four miles.
In most hybrid vehicles, 42 V supercapacitors are used. General Motors has developed a pickup truck with a V8 engine that uses the supercapacitor to replace the battery. The efficiency of the engine rose by 14%. The supercapacitor supplies energy to the alternator. Toyota has developed a diesel engine using the same technology and it is claimed to use just 2.7 litres of fuel per 100 km.
In rural areas, where there are voltage sags in the power grid, supercapacitors can be used to reduce the effect of fluctuations.
The supercapacitor has become available to the public. A commercial supercapacitor can hold 2500 farads, release 300 A of peak current with a peak voltage handling of about 400 V. The life-cycle of this supercapacitor is more than 1,000,000 charge/recharge cycles.



http://en.wikipedia.org/wiki/Ultracapacitor
quote:

As of spring 2006, EEStor Inc. claims to have a supercapacitor with a barium titanate dielectric nearing production. The company claims a unit with 37 farads capacitance and an operating voltage of 3.5 kV, capable of storing up to 52kWh. The technology is scheduled for third-party verification during the summer of 2006.



quote:

quote:
The problem I can assume with compressing gas is how to limit the amount of loss of energy through adiabatic heating as the gas is compressed.
If the tank is thermally insulated (preferably internally), this would not be a problem.



You cannot perfectly thermally insulate a tank.  You can provide sufficient insulation that you may be able to retain most of the heat for several hours, but could you keep the heat from leaking out (if only through radiation) for several days, or several weeks?

quote:

quote:
Beyond that, you also have to take into account the massive weight that a pressure vassal may add to the weight of the vehicle.
As compared to what? Lead-acid batteries?
 


Depends how much pressure you are storing there, and how certain you want to be that some external impact or slight weakness in the case wont cause a catastrophic explosion that could easily kill someone.



George
 

Offline Atomic-S

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Re: The problem with gasoline-electric vehicles:
« Reply #4 on: 02/06/2006 06:12:48 »
Very interesting. I am surprised that I have not seen in the general news work toward the use of ultracapacitors in transportation; but maybe I do not read the right newspapers.
 

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Re: The problem with gasoline-electric vehicles:
« Reply #4 on: 02/06/2006 06:12:48 »

 

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