Solar Cars: some noodling - Fuel Economy, Hypermiling, EcoModding News and Forum

aerohead · 02-09-2012, 06:52 PM

The solar car from Germany which Neil posted at the Craig Vetter thread has piqued some interest in performance prediction.
I had some data for the HONDA Dream 2 which won the 1993 World Solar Challenge and did some noodling to create a sense of what these cars are capable of.
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Given the top speed for PV alone,and 85%/15% power split@ 65mph,I solved the equations for both speeds simultaneously,iterating the rolling force coefficient and frontal area until I got a fit within 2% of published benchmarks.The following data are as published,or estimated as noted.
The Dream 2:
* Length - 240" ( 6,096mm )
* Height - 36" ( 914.4mm )
* Width - 78.7"(estimated @ rulebook max.)
* Frontal Area - 18.189 sq ft (est.) ( 1.689 sq meters)
* Cd 0.10 (published)
* CdA 1.919 sq ft (est.) ( 0.1689 sq meter )
* Curb Weight - 413 lb (187 kg )
* Race Weight - 583 lb ( 265 kg )(est. with 170-lb (77 kg ) driver
* Tires Bridgestone ECOPIA EP80 60/490-14 MT (2.25-14) tubeless
* Tire pressure 800 kPa max.(116 psi)
* Max. Power from PV array - 1,600 Watts
* Max. speed on PV (normal solar insolation) 50 mph
* Top Speed with silver-zinc battery-assist - 80+ mph
* Tire resistance @ 50 mph- 6.5 lb/1,000 lb load ( est.)
* Tire resistance @ 65 mph - 6.671 lb/1,000 lb load ( est.)
* Percent power absorbed by aero drag @ 65 mph - 85% (published)
* Percent power absorbed by R-R @ 65 mph - 15% ( published)
* Road Load @ 65 mph - 4.083 hp,3,046 Watts,3.046 kW
* Power absorption/mile @ 65 mph - 0.0468 kWh
* Power requirement by I.C.engine @ 65 mph - 4.438bhp (@ 92% mech. efficiency)
* Fuel economy @ 65 mph,best gasoline I.C.(35% thermal eff.) - 214.8 mpg
* Fuel economy @ 65 mph,best Diesel I.C.(43% thermal eff.) - 315.6 mpg
* Ave. speed,1,872-miles,WSC,52.79 mph ( 85 km/h)
* Max. speed during WSC, 69.6 mph (112 km/h)