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Solar electric speed record comes to Australia Runway 09/2 7 at the RAAF base Richmond, 60km north-west of Sydney, normally resounds to the roar of giant Hercules aircraft and the thump and screech of their tyres laying down long black strips of rubber. By GERRY NOLAN On Saturday, 5 January, 1991 it was quiet except for the occasional whirring of a sleek, solar powered car flashing past. Nine time_s the fleeting, low-slung Solar Star driven by Manfred Hermann, made the 2.5km run, trying to break the world speed record for a solar electric vehicle. The absolute, one-way, record of 129.0?km/h was set by the GM Sunraycer driven by Molly Brennan at GM's Desert Proving Ground in Mesa, Arizona, on 15 June, 1988. To beat 10 SILICON CHIP the official 2-way record, the Solar Star had to make two consecutive runs and achieve an average. speed exceeding 121.15km/h by at least 1 %. Before the attempt, Manfred lifted the sleek carapace of solar panels to check and adjust tyre and suspension air pressures. Then, switching on the vehicle's computer, he plugged in a 128Kb magnetic memory card to set the parameters for the day's runs. During the run, a 22cm wide by Bern deep liquid crystal display (LCD) in the instrument panel would dis- play battery voltage, current and temperature; motor voltage, current and temperature; and the temperature of the electronics. At the press of a key, it displays the voltage for each of the five sections of solar panels (60V): These panels are connected in sections longitudinally so that they receive the same level of sunlight along their length. If the sections ran across the car, half of each section would be in shadow while the sun was low. Each section has a peak power tracker to optimise the voltage against the current to obtain the higbest power for battery charging, for that section, under the prevailing conditions. From the batteries, the power goes via a frequency generator and the speed of the vehicle is actually controlled by varying the frequency of the power supply. Considerable electromagnetic interference (EMI) ;s generated by the system and several people driving the car have had their credit card magnetic strips irrevocably corrupted. The Solar Star can be run without the computer but there would be no performance indications. It may also be run without batteries, using direct solar energy, but it's not as simple as throwing a switch and the record attempt is for solar, electric vehicles. The digitally produced analog speedometer only indicates to 150 km/h, (would that be fast enough?) but the digital readout goes to 200 km/h, so Manfred will have no problems knowing ifhe is near the record. Besides, there will be three types of radar checking his top speed. Hans Tholstrup, founding father of solar electric vehicles in Australia, is there to represent Energy Promotions and the Human Powered Vehicle Association and, along with the police and John Ward from the NRMA, to make any record achieved official. At 10:30am the Solar Star is rolled out of the hangar. Actually it only needs to be guided, it is so light and rolls so easily. Manfred takes his shoes off and climbs in, being careful to step only on the strengthened parts of the body. The aramid/carbon Nomex body is contoured to support his almost prone body and his head is tucked into an extremely strong roll protection housing which has a radio aerial mounting point on top ofit. He has travelled nearly 5000km in this position, with his knees under the instrument panel and his feet at the very front, and says it's very comfortable. The controls A blue thumb-switch on the left side of the small, aircraft style , steering yoke operates the turning-indicators and there is a horn/radio press button under the right thumb. For the record attempts, the press button is wired for the radio. A small rocker "start" switch on the instrument panel is used to turn the car on. Control pedals are in the conventional positions, with the parking brake to the left of the pedal which controls the hydraulic drum wheel brakes. The accelerator pedal is on the right. Regenerative braking is implemented by a switch on the instrument panel and from then on is controlled by the accelerator. Suddenly the car is moving! No SOLAR STAR SPECIFICATIONS Length .... .. .......................................... Width .. .. .. .. .. .. .... .... .. .... .. .... .................. Height .. ................ ...................... ........ Track ........ .... .............................. .. ...... Wheel base .................... .. .................. Frontal area .... .... .......................... .. .. .. Drag coefficient .................................. Rolling resistance....... .. .... .... ..... .. ........ Weight ...... ........................ .................. Chassis .. .. .. .. .. ..... .. .... .. .. .. .... .. ... .. .. .... .. No. of wheels .... .. ........ .. .... .................. Type of wheel .................. .. ....... .. ......... Tyres .. .. .. .. ............................. .. ........... Brakes ................................................ Electric braking .. .. .. .. .. ...... .... .. .. .. .. .... .. Solar cells ...... .. ...... .. ............ .. ............ Load system .. .. .. .. .. .. .. .... .. .... .. .. .. ...... .. Motors .... .. .. .... .. .. .. .. .. ...... .. ...... .. .. .. .. .. .. Performance .... .. .. .. ......................... ... Top speed .. .. .. .. .. .. .. ..... .... .. ... .... .. .. .. .. .. Acceleration .... .............. ... ...... .. ........... noise, no fuss. One second it's just sitting there, the next second it is moving away smartly. There is an "aaaahhh!" from the small crowd. No matter how often you see it, the way it moves off so abruptly and quietly is always a surprise. Manfred claims to be able to out-accelerate a 1000cc motorcycle across an intersection and has achieved 60km/h in 4.3 seconds in acceleration tests. It is very hot out on the runway, with about six octas of fleecy white cirro-cumulus high in the light blue sky. During practice, they had problems with the electronics overheating, with power starting to drop off above 45°C, yet they were getting temperatures of 50°C while the car was stationary and up to 70°C during runs. For Saturday's runs, they have 30kg of dry ice to pack the heatsinks. If 30kg seems like overkill, it is. It's just that that's the minimum amount you can buy these days - at $6 a kg! After experimenting for awhile to find the most effective way to use the dry ice, they settled for Manfred's idea of just forcing the pellets between the heatsink fins. It worked. During most of the runs there was a cross wind from the north-west gust- 5.96 metres 1.98 metres 1.00 metres 1.12 metres 2.25 metres 0.58m 2 0.20Cd 0.004 285kg (including batteries) Aramid/carbon Nomex Four Aluminium disc Nylon belt (40.64cm x 1.5cm) Hydraulic aluminium drum 9kW Silicon in five sections Maximum power tracker AC asynchronous 4kW to 9kW (max) 135km/h (tested) 0-60km/h in 4.3 seconds ing from 5-15 knots (9-27.6km/h), giving about a 6 to 15km/h wind component directly along the runway from the west. The temperature at 1:15pm was 34°C. The Hon Neil Pickard, NSW Minister for Minerals and Energy, waved the flag and the Solar Star slipped away down the runway. For those waiting at the 1000 foot markers, by the emergency arrester net, it shimmered out of the haze and flashed past with a combination of rushing air and a low level, high pitched whine from the two AC asynchronous motors driving the rear wheels. At top speed, these were doing around 15,000rpm. Early problems The first run of just over 2km was in the 2 7 direction (into the west), with the NSW police Farey slant radar set up at about the mid-point and the police Kustom KRl0 car mounted in-line radar and RAAF police Kustom HR4 radar gun near the end of the run. But it didn't look right. At the high speeds, the aerodynamic forces on the body forced the front of the vehicle up , creating excessive drag. When it MARCH 1991 11 reached top speed on this run, the back end of the panels actually dragged on the ground.The result: a disappointing 122km/h. Obviously it was going to be harder than Leon Howes , managing director of Star Micronics, thought when he said, "We're not going to attempt to break the record, we're going to blow it away!" On the return run the police KR10 radar and the RAAF radar gun agreed precisely on 129km/h. Better, but the front was up so far it looked as though Manfred had rotated for takeoff. On the return run the Solar Star was clocked at only 113km/h by the slant radar. This was one of only three readings the slant radar was able to make during the nine runs, possibly due to its high directivity and the low profile of the Solar Star. Then again, perhaps it was because there wasn't a police car around the corner to make a booking! After the third run , the spectators and media were moved back from the runway while three Caribou aircraft took off. While this was going on, adjustments were made to the suspension to keep the car level at high speed. Manfred was hitting 131km/h on the fourth run when the cockpit suddenly filled with white smoke! For long moments he thought he was on fire. But no problem. The adjustments to the suspension had caused the body to rub on the tyre, making the smoke and slowing him down. After a wheel change he returned at 123km/h, which gave an average of 127km/h for the two consecutive runs . This beat the official 2-way record by enough to establish a new record but it hadn't exactly "blown it away". Record runs Manfred and the Star Micronics team returned to the hangar to make some serious alterations to the car's set-up. The main change was to connect another battery in series to boost the overall voltage. Interestingly, Manfred had to cut the scrutineers' tape that was put on in Darwin so that he could loosen the battery terminals. The German MOLL, 40Ah, leadacid batteries have done over 5000km and he hasn't even had to add water. Although they are rarely fully discharged, Manfred expects to get the 12 SILICON CHIP The Solar Star approaches the police radar "trap". This was on an early run as the front of the vehicle is raised. The suspension was later adjusted so that the vehicle would be level at high speed. Several different speed measuring radars were used to ensure accuracy. (Photographs by Gerry Nolan). equivaJent of over 300 deep cycles from them before rep lacement. On the sixth run, the car looked great but it only registered 121km/h on the KR10 radar and 122km/h on the HR4 radar gun. Then someone shouted, "Here he comes again!" and, as it scintillated out of the heat mirage, the white, curved front made a perfect oval with its reflection. Then it flashed past. He was obviously going faster! "135" the officer with the radar gun shouted, "and he held it for three triggerings." The crowd yelled. Jubilant. We were all part of it by now. You can't stand around on a runway for hours talking with the team, sharing their worries and their tensions, without getting involved, especially with such an empathetic vehicle as the Solar Star. The average between runs six and seven was up to 128km/h and the car was going really well, but the Caribous were due back any minute. Did Manfred have time for another run? He did, and again the car looked good. But the best he could do was 124km/h. Hans Tholstrup, the NRMA and po- lice conferred and compared notes before deciding that the 135km/h was an outright world land speed record for a solar electric vehicle and that they would allow 129.5 km/h as the official 2-way average of runs seven and eight. These records have been submitted to the Federation Internationale de l' Automobile (FAI) Category A Group 7 Class 1 (vehicles under 500 kg) for confirmation and will take their place in the Guinness Book of Records. Talking about the future of solar electric vehicles, everyone agreed that they are at about the same stage of development and public interest now as personal computers were in 1975, when the Altair 8800 appeared on the front cover of the American magazine Popular Electronics. To paraphrase Joseph K. Hart speaking about the future of electricity as oppos.ed to steam in 1924; "The reign of oil approaches its end; the next stage is solar electric power; enabling us to break away from the bonds of oil and become independent. Solar energy creates a decentralising form of power - using it, we may feel the thrill of control and freedom once again." SC