Solar Glossary

BLOCK: A section of a crystalline ingot from which the wafers will be cut. The footprint of the block becomes the size of the wafer.

CRUCIBLE: A quartz vessel used for melting and crystallization of polysilicon when producing multi- and monocrystalline silicon ingots.

CRYSTAL: Solid material with a regular, periodic arrangement of atoms or molecules throughout the material.

CRYSTALLIZATION OF MONOCRYSTALLINE INGOTS: Usually made by the Czochralski process explained below, but may also sometimes refer to the Float Zone process. In order to produce monocrystalline ingots by the Czochralski process, high-purity silicon is first loaded into a round quartz crucible and melted. Thereafter, a seed crystal shaped as a thin rod is dipped into the molten silicon. The seed crystal’s rod is pulled upwards and rotated at the same time. By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt. This process is normally performed in an inert atmosphere.

CRYSTALLIZATION OF MULTICRYSTALLINE INGOTS: In order to produce multicrystalline ingots, high-purity silicon is first loaded into a square quartz crucible and melted. Thereafter, the crystallization starts from the bottom of the crucible and proceeds toward the top as it is gradually cooled (directional solidification) under strict temperature and atmosphere control.

CRYSTALLIZATION OF FLOAT-ZONE INGOTS: A high-purity alternative to the Czochralski process. A radio frequency (RF) field is used to produce a local melted zone on the polycrystalline rod, without the liquid being in contact with anything except silicon. The rod is moved relative to the RF field so that the molten (float) zone is moved across the rod. A seed crystal is used at one end in order to start the growth. This molten zone carries the impurities away with it, reducing impurity concentration.

dm2 – SQUARE DECIMETER: A measurement typically used to quantify wafer production volumes.

EJ (EXAJOULE): Unit of energy, 1018 joules, often used as unit of measure for world annual energy use.

ELECTRONIC GRADE SILICON: Silicon with a purity of between 99.9999999 percent to 99.999999999 percent (9N to 11N purity).

ENERGY PAYBACK TIME: The time it takes for a solar panel to generate the same amount of energy required for its manufacture. A modern solar panel’s energy payback time is typically from 1 to 4 years, depending on the panels type and location. A typical panel lifetime is 20 to 30 years. This means that modern solar installations are net energy producers, i.e., they generate significantly more energy over their lifetime than the energy required to produce them.

FEED-IN TARIFF: Price scheme where the owner of a (solar) power system receives a guaranteed, fixed price from electricity companies for the electricity fed into the grid.

FINANCIAL INCENTIVES PROGRAMS: Several countries offer financial incentive schemes that make the cost of the system cheaper for the end user. These financial incentive schemes can be feed-in tariffs, tax credits and others.

GRID-CONNECTED OR GRID-TIED INSTALLATION: Solar power installation connected to the electric grid.

GRID PARITY: Grid parity is achieved when solar cells can produce electricity at the same price as the electrical energy you can buy off the grid, (or less) without subsidies or feed-in tariffs.

IEA: International Energy Agency.

INGOT: The silicon piece created when polysilicon is melted and crystallized in a furnace. Typical size for multicrystalline ingots are 680 x 680 mm with a weight of 250–300 kg. Monocrystalline ingots are cylindrical with typical diameters between 150 mm and 200 mm and a weight of 40–60 kg.

INVERTER: A unit that converts the electricity from the solar installation (DC – Direct Current) to electricity that is compatible with the grid (AC – Alternating Current).

kW: Kilowatt, Unit of power (1 000 watts).

kWh: Kilowatt-hour, a unit of energy equal to the production or consumption of one kW (1000 watts) for one hour.

MONOCRYSTALLINE SILICON: Processed silicon where all the material consists of only one crystal.

MULTICRYSTALLINE SILICON: Processed silicon where the material consists of several small (typically 1–20 mm diameter) crystal grains.

MW/MWp (Mega Watt peak or Million Watt peak): Unit of power. Used as output measurement in the PV industry describing the effect produced by the solar cells under standardized high insulation conditions.

OFF-GRID INSTALLATION: Solar power installation not connected to the electric grid. Normally used in areas where grid-connected electricity is unavailable or available only at a high cost.

PHOTOVOLTAICS (photo=light, voltaic=electricity): Solar cells are made of silicon. When a photon (particle of sunlight) strikes a molecule within the solar cell, an electron is knocked free. An electrical field causes this free electron to move to one side of the cell. The accumulated effect of millions of this interaction generates electricity.

PHOTOVOLTAIC (PV) EFFECT: The generation of electricity when sunlight falls near the boundary between two different substances (e.g. two differently doped semiconductors).

POLYSILICON: Highly purified silicon used in the electronic and solar industry.

SILANE: A compound gas consisting of hydrogen and silicon. An intermediate stage in the production of polysilicon.

SILICON: The second most abundant element (after oxygen) in the earth’s crust. The raw material for production of solar grade silicon as well as electronic grade silicon.

SILICON WAFER: A thin slice of crystalline silicon used as the key component in a solar cell.

SLURRY: Cutting fluid used when sawing silicon blocks into wafers. Consists of silicon carbide and polyethylene glycol.

SOLAR CELL: A semiconductor device that creates electricity when exposed to sunlight. Solar cells are usually made from silicon wafers.

SOLAR ENERGY: Refers to electricity or heat energy made from solar radiation.

SOLAR GRADE SILICON: Silicon with 99.9999 percent to 99.999999 percent purity. (6N to 8N -purity).

SOLAR PANEL: An interconnected assembly of solar cells covered by a glass front, a polymer back sheet and aluminum frame. The photovoltaic panel, more commonly known as the solar panel or solar module, is then used as a component in a larger photovoltaic system or installation to offer electricity for commercial, residential or large-scale applications.

THIN-FILM: Photovoltaic technology where the generation of solar energy takes place in a thin film of semiconductor material, normally deposited as several layers on glass. Conventional solar panels are made with wafers as the semiconductor material.

WIRE SAWING: The process where crystallized silicon blocks are cut into thin wafers using a saw with a web of thin metal wires and a cutting agent, e.g. slurry.

Wp (Watt peak): Power from solar cells is normally measured in watts when the solar cell is exposed to a standard sunlight irradiation (1 000 W/sqm), typical during the peak time of a summer day.

μm MICROMETER (micron) 10–6 M: Measurement unit typically used when describing the thickness of wafers. There are 1000 micrometers in a millimeter, and a hair is typically 60 micron thick.

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