Design and Implementation of On-board Electrical Power ... - OUFTI-1

Figure 4.3: Consumptions in % in mean case, with V batt = 3.7V, η ampl = 30%, and a Tx usageof 31%.4.4.3 Hot caseAssumptions:• No eclipse.• Solar panels temperature of 45 ◦ C.• Battery Heater turned off.• 3.3V supplied by EPS2.• The mean power produced by an effective surface of one A panel at 4.2V is 1.9W.We stated that the produced power at a given voltage was proportional to A eff when thebatteries voltage was under the MPP voltage. This condition was true for voltage between2.6V and 4.2V when the temperature was under 15 ◦ C. This is thus not true anymore in thehot case.Figure 4.4 shows the P-V curve of one solar panel at a temperature of 45 ◦ C facing thesun and the cumulated P-V curve of three solar panels at a temperature of 45 ◦ C when acorner of the CubeSat is oriented toward the sun (then A eff = √ 3A panel . In the first case,the produced power is around 1.7W at 4.2V while in the second case the produced power isaround 3.5W at 4.2V (which corresponds to 2W per A panel ). In the second case, the MPPvoltage is higher. This is due to the fact that when a face receives less insolation, its MPPvoltage is higher.In either case, the MPP voltages is higher than 3.7V. For voltage of 3V and 3.7V, theproduced power is thus still proportional to A eff .46