$1-$ Derating a PV Array to a PTC$,$ AC Rating. Consider a PV array rated at $1$ kW

under standard test conditions. Module nominal operating cell temperature

$($NOCT$)$ is $47$C$.$ DC power output at the MPP drops by $0\mathrm{.}5\%/$C above the STC

temperature of $25$C$.$

Estimate its ac output under PTC conditions if there is a $3\%$ array loss due to

mismatched modules, dirt loss is $4\%,$ and the inverter has an efficiency of $90\%.$

$2-$ Cost of PV Electricity for a House which has a PV system that costs $$16,850$ to

deliver $4000$ kWh$/$yr$.$ If the system is paid for with a $6\%,30-$year loan, what

would be the cost of electricity?