Pumped hydro storage is considered a viable way to store electrical energy, which can be vital to enabling large-scale generation of intermittent renewable energy such as wind and solar. A project in northern BC utilizes two lakes which have 400 m of elevation difference. 400 m When there is excess power generation overnight, a pump which is 80% efficient delivers water from the lower lake to the upper lake via a 480 m long pipe. When the pump is switched on, the lower lake, which has a volume of 5000 m, drains in 45 minutes. A pressure gauge on the discharge of the pump reads 1600 kPa. PG In the afternoon, when the electricity demand is the highest, the upper lake drains via gravity into a turbine at the same elevation as the lower lake. The 480m long penstock (which is a fancy name for a pipe which feeds a turbine in hydroelectric applications) is a 350mm (nominal pipe size) schedule 40 galvanized iron pipe. When the turbine, which is 85% efficient, turns on, the upper lake, which has a volume of 5000 m (p=998.2 kg/m) drains in 2 hours. n = 480 m What is the round-trip efficiency for this process? Hint: round-trip efficiency is the total efficiency of the pumping process and the power generation process and is given by: output Pturbine input Ppump =