“No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same reservoirs.”
Fuel cells are different from electrochemical cell batteries in that they consume reactant, which must be replenished, whereas batteries store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and change as a battery is charged or discharged, a fuel cell’s electrodes are catalytic and ideally do not change over time.
Many combinations of fuel and oxidant are possible. A hydrogen fuel cell uses hydrogen as fuel and oxygen (usually from air) as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include air, chlorine and chlorine dioxide.
Many things can sustain the transfer or consumption of energy on this scale; some of these events or entities include: lightning strikes, large electric motors, naval craft (such as aircraft carriers and submarines), engineering hardware, and some scientific research equipment. A large residential or retail building may consume several megawatts in electric power and heating energy.
The productive capacity of electrical generators operated by utility companies is often measured in MW. Modern high-powered diesel-electric railroad locomotives typically have a peak power output of 3 to 5 MW, whereas nuclear power plants have net summer capacities between about 500 and 1300 MW.
MicroPower Modules can be used independently, as a lightweight miniature power system of their own, or arranged together to generate power from large heat sources.
For more info, read our thermoelectrics background section.
A human climbing a flight of stairs is doing work at a rate of about 200 watts. A typical car engine produces mechanical energy at a rate of 25,000 watts while cruising. A typical light bulb uses electrical energy at a rate of around 35 to 100 watts, while compact fluorescent lights generally consume 5 to 30 watts.