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 nationís largest urban solar powerplant, says an Exelon spokesman. Development of the 10-MW photovoltaic facility at a former industrial site on Chicagoís 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 plantís 32,800 solar panels. Exelon says it expects to hear from the agency on the guarantee in June or July.