4. A typical commercial solar photovoltaic (PV) cell costs approximately $7 per watt and requires 7.6 TJ of energy per million dollars to manufacture the solar cells. (a) If the PV cell has a conversion efficiency of 9%, a performance efficiency of 80% and a lifetime of 30 years. How much electricity will a 10 m by 2 m PV panel generate over its lifetime, based on an average solar insolation of 1700kWh/m2-yr? (b) Estimate the cost of the PV panel in part (a). Assume daylight averages 12 hours per day at full output and neglect adjustments associated with the Standard Laboratory Test Condition (STC). (c) Estimate: (i) the energy invested in manufacturing the PV panel in (a). (ii) the time (in years) required for the PV panel in (a) to return its initial energy investment. (d) If electricity displaced by the solar cells would cost $0.10 / kWh in the retail market, then what is the time that it would take for the PV panel in (a) to pay for its initial cost? Hint: TJ = Tera-joules = one million million joules = 1012 joules; 1 J/sec = 1 W