Let's analyze and solve the problem step by step. --- ## Given Data: - Number of cells in series: **36** - Open circuit voltage at 25°C per cell: **.6 V** - Voltage reduces with temperature at: **-2 mV/°C** (or **-.002 V/°C**) - Max power point occurs at **80%** of open circuit voltage - Operating temperature: **60°C** --- ## Step 1: Find the open circuit voltage per cell at 25°C \[ V_{oc,25} = .6\,V \] ## Step 2: Find the open circuit voltage per cell at 60°C Temperature change: \[ \Delta T = 60^\circ C - 25^\circ C = 35^\circ C \] Voltage change per cell: \[ \Delta V_{cell} = -2\,mV/^\circ C \times 35^\circ C = -2 \times 10^{-3} \times 35 = -.07\,V \] Open circuit voltage per cell at 60°C: \[ V_{oc,60} = V_{oc,25} + \Delta V_{cell} = .6\,V - .07\,V = .53\,V \] --- ## Step 3: Find the total open circuit voltage at 60°C for all 36 cells \[ V_{total,oc} = 36 \times .53\,V = 19.08\,V \] --- ## Step 4: Find the voltage at maximum power point (80% of open circuit voltage) Max power point voltage: \[ V_{mp} = .8 \times V_{total,oc} = .8 \times 19.08\,V = 15.264\,V \] --- ## **Answer:** **The voltage at maximum power point at 60°C is approximately \(\boxed{15.26\,V}\).**