A single unit of an electrochemical device capable of producing direct voltage by converting chemical energy into electrical energy.

A battery usually consists of several cells electrically connected together to produce higher voltages. Sometimes the terms cell and battery are used interchangeably.

The smallest unit having the capacity to live and to reproduce, independently or as part of a multicelled organism.

The simplest operating unit in a storage battery.

It consists of one or more positive electrodes or plates, an electrolyte that permits ionic conduction, one or more negative electrodes or plates, separators between plates of opposite polarity, and a container for all the above.

A specially-prepared space or structure in the nests of bees and wasps in which food is stored, an egg is laid, and the larva completes its development.

A very thin region of static electric charge along the interface of the positive and negative layers in a photovoltaic cell.

The barrier inhibits the movement of electrons from one layer to the other, so that higher-energy electrons from one side diffuse preferentially through it in one direction, creating a current and thus a voltage across the cell; also called depletion zone or space charge.

The area of immediate contact between two layers (positive and negative) of a photovoltaic cell.

The junction lies at the center of the cell barrier or depletion zone.

A cell (battery) with a captive electrolyte.

A primary battery that cannot be recharged.

An advanced type of photovoltaic cell that uses a dye-impregnated layer of titanium dioxicde to generate a voltage, rather than the semiconducting materials used in most solar cells.

A device containing two conducting electrodes, one positive and the other negative, made of dissimilar materials (usually metals) that are immersed in a chemical solution (electrolyte) that transmits positive ions from the negative to the positive electrode and thus forms an electrical charge.

One or more cells constitute a battery.

An electrical device powered by fuel from a tank that makes energy through a chemical reaction.

A fuel cell is similar to a large battery, but where a battery gradually runs down, a fuel cell runs continuously for as long as there is fuel in the tank.

A fuel cell is a type of battery which converts the chemicals hydrogen and oxygen into water, and in the process produces electricity.

Hydrogen is pumped into the cell from an on board tank, while the oxygen is taken from the air outside. Together they form steam, which is emitted through the car's exhaust.

Some car makers are putting a lot of time and effort into developing hybrid cars where the electric motors are powered by fuel cells.

Hydrogen is the most abundant element in the universe, but it is highly flammable; that is, it bursts into flames easily and as the lightest gas, it just floats away. Even so, it can be extracted from water, fossil fuels, and other substances.

The problem is to compress, or squeeze, hydrogen into a tank small enough to fit in a car. The tank can be topped off with hydrogen at refueling stations, but there are very few of such places available at this time.

The advantages and disadvantages of fuel-cell cars

In theory, electric-fuel-cell cars could be the answer for clean cars of the future:

• Fuel cells are reliable and make little noise since they have no moving parts.
• Water is the only thing emitted through the exhaust.

There are a number of challenges still to be overcome:

• Increasing the amount of electricity produced so the car has more power.
• Compressing and safely storing enough hydrogen into a small tank for hundreds of miles of driving.
• Making affordable cars which are now very expensive in that a fuel-cell system costs ten times more to make than a conventional engine.

A fuel cell technology that uses metals; such as, zinc, aluminum, and magnesium in place of hydrogen to provide electrical power in order to overcome certain disadvantages that are associated with hydrogen as a fuel.

The estimated temperature of a photovoltaic module when operating under 800 watts per square meter irradiance, 20 degrees Celsius ambient temperature and wind speed of one meter per second.

NOCT is used to estimate the nominal operating temperature of a module in its working environment.

A device for measuring light intensity that works by converting light falling on, or reach it, to electricity, and then measuring the current; used in photometers.

A type of photovoltaic device in which the electricity induced in the cell is used immediately within the cell to produce a chemical, such as hydrogen, which can then be withdrawn for use.

The smallest semiconductor element within a PV module to perform the immediate conversion of light into electrical energy (direct current voltage and current). Also called a solar cell.

A cell of machines serviced by a robot for loading and unloading.

Any battery that can be recharged; that is, one which can receive an additional charge after its primary one.

A battery containing little or no free fluid electrolyte.

A device where sunlight concentrated onto a absorber heats it to a high temperature, and the thermal radiation emitted by the absorber is used as the energy source for a photovoltaic cell that is designed to maximize conversion efficiency at the wavelength of the thermal radiation.

A battery designed with a vent mechanism to expel gases generated during charging.

A compound cell made of different semiconductor materials in layers, one above the other.

Sunlight entering the top passes through successive cell barriers, each of which converts a separate portion of the spectrum into electricity, thus achieving greater total conversion efficiency of the incident light.