sentences:  Otherwise a cloud could pass over and cause the sudden drop in output to overload the generators, causing them to trip off.If a pumped-hydro facility was added in the nearby hills, that would allow the base to operate during power failures under solar power, although batteries would also be needed to allow time for the hydro-electric plant to adjust to the load requirements.Nellis consists of 5,821 tilted axis, T20 single axis trackers made by Sunpower, and uses 72,416 solar panels, each 200 watts, and 54 Xantrex (Schneider Electric) GT 250 inverters, each rated 250 kW.