[RenewableEnergyAccess.com] During the fourth day of the North American Solar Challenge – the 2,500-mile cross-country solar car challenge that began in Austin, Texas on July 17 and ends on July 27 in Calgary, Alberta, – 12 teams reached the Sioux Falls, S.D. checkpoint. The leader, the University of Minnesota, second place University of Michigan and third place University of Waterloo are expected to cross the Canadian border July 21. With yesterday’s results, Minnesota takes the overall lead with the lowest cumulative time, having traveled 1,108 miles in 27 hours, 20 minutes and 44 seconds. They are followed closely by Michigan at 27:52:21 and Waterloo at 28:34:26. Time penalties, if any, have not yet been assessed. The NASC has two classes competing; the open class where teams are allowed to use batteries or solar cells of their choice and the stock class where teams use only lead acid batteries and solar cells approved by NASC officials. The stock class leader at the end of four days of racing is CalSol with a time of 31:59:55. CalSol is in ninth place in the overall standings. Official daily results will be posted at the following link.