Friday, May 22, 2009

Method and procedure for designing a Range extender EV from emission cycle standards

As new Cafe standards and and emission control standards are in place we need to improve the efficiency of the existing vehicles.

There are multiple approaches to address the issue:

  •  Improving existing ICE by use of new technologies and designs 
  •  Use of a supplement and increase the efficiency ( hybrids )
  •  Renewable non fossil energy ( EVs, fuel cells etc )

One of the problem people face on no fossil energy use  is the energy storage technologies are not affordable and the infrastructure is not ready and they are not proved. So we need an approach which is hybrid but more upgradable to future. As the Fuel cell and EVs depends on the electricity the approach needed to be electricity centric. 

One approach is a serial hybrid. There are other approaches like parallel hybrids, mild hybrids, strong hybrids, BAS hybrids etc. The good part of  serial hybrid is that its more future oriented and its a step closer to the renewable non fossil vehicles.

This post is an extension of the previous post of "something before volt".  This post is reflections of my thoughts on a 10 mile capable battery EREV. Because its for a 10 mile range, we assume the battery costs are less. We even  think it can be a ultra capacitor also because we need a device which can store and provide energy for the vehicle to travel 10 miles electrically.

The first step is a test EV ( electric vehicle ) which as capability to record the power used by the electric engine on a defined cycle. A cycle is a defined patten of driving for a particular time period. 

The Test  Ev will have the exact motor configuration we plan to have in our final product.
Example One motor 2 rear wheels ( say 90kw) and 2 in wheel motors ( 30kw ) for the 2 front wheels.

This configuration gives the advantages of rear wheel drive and on required conditions the front wheels can act and get AWD advantages. Secondly the front motors will  be more concentrating on regeneration of power from the regenerative breaking.

As a detailed step we will go through the different cycles defined by different standard authorities for the emission tests.

look at and get the required information , contact the  authorities and get the documents.

Some interesting cycles for US  are 

  1.  US06  : 600 seconds long  representation of aggressive, high speed and/or high acceleration driving behavior, rapid speed fluctuations, and driving behavior following start up.
  2.  FTP 75 :
  3. HWFET cycle :
  4. New york city cycle :
  5.  California Unified Cycle (UC) :
  6. The SC03 Supplemental Federal Test Procedure :

etc etc. for a primary study on different cycles use :

Similarly use all the countries you are interested in and get the cycle information. 

Now perform these cycles with the test EV and get all data points and plot graph on the power requirements against time , Now you have two graphs where one with speed vs time and second energy requirements vs time. 

Repeat the procedure with the cycles you have interest and make the data ready.

Now its time to choose a optimal electric generator with 
1) Emission characteristics matching the cycle requirement.
        2) Electricity generation capability which is at an optimal level for the above data collected cycles. Assume battery will be supplementing the extra power needs.

The modes the range extender will operate are :

  • PURE EV mode
  • Generator power only mode
  • Generator power + Battery power mode
  • Battery recharge mode
  • Generator power only run   and Battery recharge mode

Regeneration can occur on all the above mode as user uses the breaks and other regenerative mechanisms ( example: regenerative shock absorbers )

So as per the logic : The range extender will run on EV mode when the battery is full and above threshold range extender point. Lets say if its  10 mile battery 5 miles in EV mode
Once it reaches 5 miles, the generator kicks in and acts as primary source of running, Now the battery will act as a supplemental energy provider on acceleration, load and uphill ( more 
energy need scenarios ). The battery will be charged back when ever there is an opportunity for regeneration of the power. The generator will recharge the battery when the vehicle is 
in a stop position or need less power than the optimal point power which generator is deigned to generate.Once the power inside the battery reaches back to a level say "return EV mode point"
say 7 mile capability, the generator will be shut off back and the Range extender will run in a Pure EV mode. again when it hits back the threshold range extender point the generator will be kicking in again back.

The points 
 1) the constant generator capacity,
 2) Threshold range extender point
 3) Return EV mode point 

etc should be designed by the applications processing unit intelligence. This can be visualized as profiles ( example: city profile, High way profile, Up hill profile, AWD profile ,Intelligent AWD profile , etc will have different values for the points and will result in different drive experiences for the users). By adding plug in charging , the vehicle should be able to work as a plug in hybrid.

Once, the design of profiles are also completed, we will be almost ready will the design and only new places to explore may be the traction control mechanisms only. Once completing the data points and logic of control, we will be ready to develop the software needed and make out EREVs first tests. The data points can be perfected using software using proving grounds, test fleets 
etc and they can be always updated with software/firmware downloads.

Yes guys, We now did a design of a global focused designed EREV. Back to key points :

1) The Generator characteristics and control interface
2) The operating points
3) The traction control mechanisms to get max out of the electric motors
4) Electric motor characteristics
5) Power dissipation capabilities and storage capabilities of battery.

I think global vehicles can be born from more thinking than just dump executions.

© yankandpaste®

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