Glossary

Carnot’s Theorem

Carnot's theorem, also called Carnot's rule, is a principle which sets a limit on the maximum amount of efficiency any possible heat engine can obtain, that depends only on the difference between the hot and cold temperature reservoirs and the absolute temperature of the hot reservoir. Carnot's theorem states: “No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same:

(T_hot-T_cold)/T_hot

Carbon emissions trading

Carbon emissions trading is emissions trading specifically for carbon dioxide (calculated in tonnes of carbon dioxide equivalent or tCO2e) and currently makes up the bulk of emissions trading.

It is one of the ways countries can meet their obligations under the Kyoto Protocol to reduce carbon emissions and thereby mitigate global warming.

Emissions trading

Emissions trading (or emission trading) is an administrative approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants. It is sometimes called cap and trade.

A central authority (usually a government or international body) sets a limit or cap on the amount of a pollutant that can be emitted. Companies or other groups are issued emission permits and are required to hold an equivalent number of allowances (or credits) which represent the right to emit a specific amount. The total amount of allowances and credits cannot exceed the cap, limiting total emissions to that level. Companies that need to increase their emission allowance must buy credits from those who pollute less. The transfer of allowances is referred to as a trade. In effect, the buyer is paying a charge for polluting, while the seller is being rewarded for having reduced emissions by more than was needed. Thus, in theory, those that can easily reduce emissions most cheaply will do so, achieving the pollution reduction at the lowest possible cost to society.

Fuel Cell

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.

Gigawatt

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.

Kilowatt

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.

Megawatt

The 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.

Microburner technology

A miniature device that burns fuel for delivering heat to MicroPower Modules. The combination of these can be configured as a highly effective miniature generator that acts in many respects like a miniature fuel cell. A miniature generator made from a Microburner and MicroPower Modules is expected to create 5-10 times the energy of lithium batteries in the same sized package.

MicroPower Chip

An entirely solid state device with a structure made from n and p-type thermoelectric materials that mimics the best features of a thermionics device, resulting in a simple device with superior performance to both at modest temperatures.

MicroPower Module

An assembly of many MicroPower Chips connected 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.

Semiconductor

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.

Semiconductor device fundamentals

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.

Thermionics

A material structure that produces a voltage across itself when there is a temperature difference on each of its sides, where an electric field is used as a barrier to sort out only the most energetic electrons. This technology has traditionally been constructed as a vacuum gap between two metal plates, and requires extremely high temperatures to operate efficiently.

Thermoelectrics

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.

Watt

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.