Transparent SUV has Lowest Coefficient of Drag

 With a coefficient of drag (CD) of only 0.095, it is the lowest achieveable, even among the World Solar Challenge cars. I have only measured the CD of Stella Vie and CUER Resolution with have CD of 0.10.

 Initially I though MicroCFD cannot calculate lower CD values because the CUER Resolution has a tear drop shape that should make it the most aerodynamic but the results did show it. At leas they are better than the true teardrop shape that I got samples of. They were however scaled to have a height to length ration of 0.3 that is similar to the proposed dimensions of the original Transparent Cars.

This CD of 0.095 is achieved with the Transparent SUV that is to be entered for the World Solar Challenge according to its regulations for the 2021 event. Its dimensioin is adjust to 1.3 because this is the tallest that is allowed. The Transparent SUV will have the highest ground clearance of 0.3 m, so the height of the SUV will be 1.6m, barely passing the height limit of 1.6 m. Its length is also increased to 4.5 m, making its height to length ration to be less than 0.3, contributing to its low CD.

Please note that both Stella Vie and CUER Resolution has a height of less than 1.2 m, barely enough for the drivers. That is why they use small drivers only. Despite this low height to length ration, they still cannot beat the SUV shape of the Transparent SUV, CD.

Please not CD is not drag. It is only a coefficient. The total drag depends on the frontal surface area of the vehicles. The CD of the Challenger class is not that much lower than the Cruiser class, but their frontal surface areas are much smaller, so their drag is much lower, allowing them to drive faster under solar power alone.

Despite its lower CD, the Transparent SUV will have more drag because of its larger frontal surface area. This can be offset by being able to tilt the solar panels. The high ground clearance helps because the whole vehicle can also add to the tilting. Hopefully with minimal effect on CD.

The greenhouse effect of a transparent car can be utilised to generate electrical power when outside air is allowed to enter to cool the car. The extra heat energy should allow more energyy conversion. Hopefully, more energy converted than lost due to drag as a result of opening a hole in front of the car. The water vapour which should be used to cool the solar panels and drivers inside the car should also contribute more to the turbine generation of electrical energy.

The greatest opportunity is to use an airconditioining system to pump heat from the car to the intake of a turbine generator. It may sound like the impossible perpetual motion machines but feeding back an output back to the input is common in jet engines and even the fusion power reactors. Except that, jet engines are sustainable because its output power is much larger than the input power, whereas the fusion generators spend more power for its input than the output.

If we are able to achieve refrigeration to zero temperature difference between inside and outside temperatures, with little loss in aerodynamic drag, this is considered a major achievement. The solar panels can operate more efficienly.

Theoretically, a Carnot refrigerator can operate at efficiency, or more politically correct to call it, coefficient of performance, (COP) of infinity, when the inside temperature is the same as the outside temperature., but not so easy to match the efficiency of the Carnot cycles.

The turbine generator will be placed at the back of the SUV when travelling, but when stationary, it may be better to place it at the roof. It creates a problem with the organiser because not only will the turbine benefit from the heat inside the car, it also benefits from the flowing air outside the car. It should be fair but this is a competiton. For practical use, not sure if people are willing to pay the extra costs and hussle of placing turbine generators just to get a few watts of energy.

We do not expect the turbine to provide a lot of power. However, in a solar car situation, any extra energy source is important. It may make the difference in making solar cars practical and widely used.













Comments

Post a Comment

Popular posts from this blog

A Short Guide To Metric Nuts and Bolts

Image
Hit enter to search or ESC to close A Short Guide To Metric Nuts and Bolts Answers to the most Frequently Asked Questions Standard and Fine Pitch Threads How to identify nut and bolt strength grades How nut and bolt strength grades compare Maximum Tightening Torques Why specified torque is sometimes lower than the maximum Spanner Sizes Versus Bolt / Nut thread size Allen Key size versus Bolt / Nut thread size Correct Drill size for Tapping Metric threads in holes Introduction: Metric Nuts and Bolts This short guide is intended to give a very basic introduction to ISO metric nuts and bolts. It is intended for those working in plant and machinery maintenance to give enough information on to ensure that correct replacement parts are identified and used. Few parts are as critical in the assembly of modern machinery as the nuts and bolts which hold it all together and, at first sight, it seems that all metric bolts are basically the same. In fact, of course, nothing could be further from th
Read more

CAN Bus Wiring Diagram, a Basics Tutorial

Image
https://tekeye.uk/automotive/can-bus-cable-wiring Index ↓ About ↓ CAN Bus Wiring Diagram, a Basics Tutorial The CAN bus is a common digital data network used in automotive, industrial, medical and scientific systems. The CAN bus is used for routing sensor data between pieces of equipment. The main advantages are high resilience to noise, reliability, low cost, simple wiring and ease of use. The disadvantages are that the data packet lengths are small, transmission rates are low and the message transmission cycle time can vary. This article covers the basics of CAN bus wiring, showing a simple CAN bus wiring diagram and how to wire up a CAN bus cable. It covers wiring for the common DB9 plug and socket often used with CAN bus test equipment. The DB9 is also known as 9-pin D-sub, DE-9 (its correct name), DB-9, serial connector, RS232 connector or null modem connector. The CAN bus is used in nearly every form
Read more

Best Free CFD Tutorial: FreeCAD Openfoam CFD Workbench

Image
I find watching this video boring but the links are userful and the linked tutorial very helpful. Better than reading the instructiions in the FreeCAD Addon installation comments for CFDof. http://www.opensim.co.za/training.html   The tutorial that is useful in doing CFD for car is the one below: https://github.com/opensimsa/opensim/raw/master/Documentation/CFD/UAV2/CFD%20Tutorial%204%20-%20External%20Aerodynamics%20of%20a%20UAV.pdf   WINDOWS: ● https://www.freecadweb.org/wiki/Download ● Install CfdOF from Tools | Addon manager ● Go to Edit | Preferences | CFD to check and install dependencies   Of special note: I install the older version of Paraview as shown in the FreeCAD preferences. I downloaded cfmesh and HiSA from sourceforge. No need to look for binaries. It appears as though the master file  zipped file can be installed by FreeCAD.   cfMesh downloaded to C:\Users\othma\AppData\Local\Temp\tmpwg568v1r.zip Installing cfMesh... Install completed Downloading HiSA, please wait...
Read more