The U.S. Energy Dept. is soon to give Chicago-based energy services provider Exelon Corp. "reasonable assurance" of a $50-million agency loan guarantee to spur construction of what would be the nation�s largest urban solar powerplant, says an Exelon spokesman. Development of the 10-MW photovoltaic facility at a former industrial site on Chicago�s South Side, to be finished by the end of 2009, is contingent on receiving the loan guarantee for 80% of its $60-million cost, says the spokesman. Exelon and its partner, San Jose, Calif.-based SunPower, have begun clearing the 39-acre brownfield site where the plant would be built. SunPower would design, manufacture and install the plant�s 32,800 solar panels. Exelon says it expects to hear from the agency on the guarantee in June or July.