Glossary

Carnot’s theorem, also called Carnot’s rule is a principle which sets a limit on the maximum amount of efficiency any possible engine can obtain, which thus solely depends on the difference between the hot and cold temperature reservoirs. Carnot’s theorem states:
“No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same reservoirs.”
A fuel cell is an electrochemical conversion device. It produces electricity from the strong tendency of fuel and oxygen to react vigorously. Fuel (on the anode side) and an oxidant (such as oxygen on the cathode side) react in the presence of an electrolyte. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it.

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.

The gigawatt (symbol: GW) is equal to one thousand megawatts (or 1 billion Watts). Large electric generating plants (both nuclear and coal-fired) produce power at this level. Because of the large spread in power output of plants across the globe, virtually all power plant outputs are described in megawatts, even though many power plants have output powers in excess of 1000 megawatts or 1 gigawatt.
A kilowatt (kW) is equal to one thousand watts, and is typically used to state the power output of engines and the power consumption of tools and machines. A kilowatt is approximately equivalent to 1.34 horsepower.
A megawatt (MW) is equal to one thousand kilowatts.

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.

An entirely solid state device with a structure made from n and p-type thermoelectric materials that delivers significantly enhanced energy conversion efficiency.
An assembly of many MicroPower Chips connected via a proprietary hot contact structure and sandwiched between two ceramic plates. The chips are arranged thermally in parallel so that each of the chips does a balanced amount of work, and electrically in series to increase voltage and increase the overall usability of the power generated by the module as a whole.

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.

A semiconductor is a solid material that has electrical conductivity between those of a conductor and an insulator. Semiconductor devices, electronic components made of semiconductor materials, are essential in modern consumer electronics.
The main reason why semiconductor materials are so useful is that the behaviour of a semiconductor can be easily manipulated by the addition of impurities, known as doping. Semiconductor conductivity can be controlled by introduction of an electric field, by exposure to light, and even pressure and heat; thus, semiconductors can make excellent sensors. Current conduction in a semiconductor occurs via mobile or “free” electrons and holes, collectively known as charge carriers. Doping a semiconductor such as silicon with a small amount of impurity atoms, such as phosphorus or boron, greatly increases the number of free electrons or holes within the semiconductor. When a doped semiconductor contains excess holes it is called “p-type”, and when it contains excess free electrons it is known as “n-type”, where p (positive for holes) or n (negative for electrons) is the sign of the charge of the majority mobile charge carriers. The semiconductor material used in devices is doped under highly controlled conditions in a fabrication facility, or fab, to precisely control the location and concentration of p- and n-type dopants. The junctions which form where n-type and p-type semiconductors join together are called p-n junctions.
A thermoelectric material creates a voltage across itself when there is a different temperature on each of its sides. Conversely when a voltage is applied to it, it creates a temperature difference.

For more info, read our thermoelectrics background section.

The watt is the standard unit of power, equal to one joule of energy per second. It measures a rate of energy conversion.

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.