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1) Fuel cell : functioning and utilisation A fuel cell is a converter : chemical energy of reactants (fuel+ox) is converted inot low voltage electricity through electrochemical reactions. So, fuel cells use an external fule supply. Ideally, a fuel cell can operate as long as it is fed with fuel and ox and the reaction products are removed. For space app. : hydrogen + oxygen The reaction releases two free electrons and the waste product (water) can be an advantage for manned missions. 2) Effects of temperature on solar panel performances An increase of temperature leads to a decrease of the solar cell efficiency : for this reason, when the solar panels exits the period of eclipse, for the first minutes it has an higher efficiency due to the cooling of its surface during shadow. Looking at the plots current Vs voltage, we can see that if the temperature increases, the current increases but the voltage decreases.+ (N.B. efficiency = conversion solar power into electric power) 3) Difference between RTG and solar panels Solar panels convert the solar power into electric power, while an RTG exploits the radioisotope decay of a radioactive material. From an electrical point of view they are both sources, but the main difference (beyond the power source) consists in the fact that the solar panel obviously needs to be exposed to the sun in order to provide electric power, while the RTG is completely autonomous and the decay process cannot be stopped. For this reason the RTG is mainly used when there is no solar power source. Another difference consists in the fact that the RTG maintains its performances for longer time, while the degradation of a solar panel is faster. Solar panels have a conversion efficiency higher than the one of RTG, which is something about 5/7 % (the rest…