Appendix C
Terms and Definition
Absorber: The absorber is the active surface in a solar collector. The absorber can be made of various materials and often the surface is applied with a selective coating that allows solar short wave (solar heat and light) to transmit, while long wave heat is reflected. Upon absorption, the solar energy transforms from short wave into long wave energy.
Acceptor: It is a dopant atom (from group III of periodic table) that when added to a semiconductor can form a p-type region.
Adhesion: It is an extremely thin layer of molecules (as in gases, solutions, or liquids) to the surface of solid bodies or liquids with which they are in contact.
Adsorption: It is a process where a solid is used for removing a soluble substance from the water.
Aerobic fermentation: Fermentation processes that require the presence of oxygen.
Aerobic: Organism able to live, grow, or take place only where free oxygen is present.
Aerodynamic: It is the study of forces and the resulting motion of objects through the air.
Agricultural residue: Agricultural crop residues are the plant parts, primarily stalks and leaves, not removed from the fields with the primary food or fibre product. Examples include corn straws (stalks, leaves, husks, and cobs), wheat straw, and rice straw.
Airfoil: The cross-sectional profile of a wing.
Air mass (sometimes called air mass ratio): A large body of air with only small horizontal variations of temperature, pressure, and moisture and approximated as equal to the cosine of the zenith angle.
Algae: Fast growing photosynthetic plants containing chlorophyll in freshwater, seawater, or damp oils.
Alternating current (AC): The periodically varying flow of electric current.
Alternative fuels: Fuels derived from non-conventional energy resources for replacing conventional fossil fuels.
Ambient temperature: The temperature of the surrounding area.
Amorphous semiconductor: A non-crystalline semiconductor material that has no long range order.
Amorphous silicon: A thin-film, silicon photovoltaic cell having no crystalline structure.
Amplitude: The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
Anaerobic digestion: A biological process in which degradation of organic matter by microbes takes place in the absence of oxygen to produce methane and carbon dioxide.
Anaerobic: Life or biological processes that occur in the absence of oxygen.
Anemometer: An instrument that measures wind speed.
Angle of attack: It is used to define the angle that forms chord of the profile with a fluid stream.
Angle of incidence: The angle that an incident straight line or ray of light makes with a perpendicular drawn on the surface at the point of incidence line meeting.
Angle of inclination: The angle that a solar collector is positioned above horizontal with reference to solar energy systems.
Angular frequency: It is the frequency of a periodic process (as electric oscillation or sound vibration) expressed in radians per second and given by frequency in cycles per second multiplied by 2π.
Anode: It is the positively charged electrode (or element) that attracts the negative (-) charged particles in a circuit or chemical reaction.
Antireflection coating: A thin coating of material applied to a solar cell surface that reduces the light reflection.
Array current: It is the electrical current produced by a photovoltaic array when it is exposed to sunlight.
Array operating voltage: The voltage produced by a photovoltaic array when exposed to sunlight and connected to a load.
Aspect ratio: For a geometric shape, it is the ratio between its sizes in different dimensions such as numerical ratio of the length (height) to cross-sectional area of a thermoelectric element.
Azimuth angle: The azimuth angle is often referred to when a solar collector surface is installed or engineered. The azimuth angle is a figure that tells you how many degrees out of south, the direction of the solar collectors are.
Band gap energy (Eg): The amount of energy (in electron volts) required to free an outer shell electron from its orbit about the nucleus and allows it crossing from the valence to the conduction level.
Band gap: It is the energy difference between the highest occupied state in the valence band and the lowest unoccupied state in the conduction band. The material is either a semiconductor if the band gap is relatively small or an insulator if the band gap is relatively large.
Barrier energy: The energy given up by an electron in penetrating the cell barrier; a measure of the electrostatic potential of the barrier.
Battery energy storage: Electrical energy stored in electrochemical batteries.
Beam radiation: Another name for direct normal irradiance, the amount of solar radiation from the direction of the sun.
Begasse: Residue remaining after extracting a sugar juice from plants like sugarcane.
Betz coefficient (16/27 = 59.3%): This is the theoretical maximum efficiency limit of a wind generator.
Binary cycle: It is a combination of two cycles adjacent to each other utilizing two different working fluids for power production. The low thermal heat from the first cycle is transferred in a heat exchanger to the working fluid in the second closed cycle that drives a turbine coupled to an electrical generator to produce electricity.
Bioconversion: A general term describing the raw biomass conversion to energy or fuels.
Biodiesel: A biodegradable transportation fuel for use in diesel engines obtained from biomass by biological conversion.
Bioenergy: Energy derived from biomass by means of bio-conversion technologies and is a substitutes of fossil fuels.
Biofuels: Biomass converted to liquid or gaseous fuels such as ethanol, methanol, methane, and hydrogen.
Biogas: A combustible gaseous mixture of methane (50%–60% of total gas) and carbon dioxide produced by the anaerobic digestion of organic matters.
Biomass: Any plant-derived organic matter such as agricultural crops and residue, wood and wood waste, animal waste, aquatic plants and organic components of municipal and industrial wastes.
Biomass fuel: Liquid, solid, or gaseous fuel produced by conversion of biomass.
Biosphere: The portion of the earth and its atmosphere that can support life.
Bismuth telluride: It is a grey powder that is a compound of bismuth and tellurium and exhibits good thermoelectric properties.
Bismuth antimony: It is one of the most important material systems for low temperature thermoelectric and other applications.
Blocking diode: It is a semiconductor diode for limiting the direction of flow of energy flow in one direction only.
Boron (B): The chemical element commonly used as the dopant in photovoltaic device or cell material.
Bottoming cycle: A cogeneration system in which steam is used first for processing heat and then for electric power production.
British thermal unit (BTU): It is a standard measure of thermal energy in UK. A single BTU is the amount of energy required to increase the temperature of one pound of water by one degree Fahrenheit (F); further, 1,000 BTU per hour is equal to 0.293 kW.
Bulb turbines: It is a variation of the propeller-type turbine (similar to the Kaplan turbine) in which the generator is located in a watertight housing called the bulb.
Cadmium (Cd): A chemical element used in making certain types of solar cells and batteries.
CdTe solar cells: A cadmium telluride solar cell uses a cadmium telluride (CdTe) thin film, a semiconductor layer to absorb and convert sunlight into electricity.
Cadmium telluride (CdTe): A polycrystalline thin-film photovoltaic material.
Capacity factor: It indicates how much electricity a generator actually produces relative to the maximum. It could produce at continuous full power operation during the same period.
Carbohydrate: Organic compounds made up of carbon, hydrogen, and oxygen and having approximately the formula (CH2O)n includes cellulose, starch, and sugars.
Carbon dioxide (CO2): A colourless, odourless gas produced by respiration and combustion of carbon-containing fuels and used by plants as a food in the photosynthesis process. It is also called as greenhouse gas.
Carbon monoxide (CO): A colourless, odourless, and poisonous gas produced by incomplete combustion.
Cathode: The cathode is the negatively charged electrode. It attracts the positive charge and is the source of electrons or an electron donor.
Celsius scale: The metric temperature scale for which 0°C is the temperature at which water freezes and 100°C is the temperature at which water boils at standard atmospheric pressure. The conversion from Fahrenheit to Celsius is
Central receiver system: A single central receiver such as a boiler, engine, or photovoltaic array (for solar electric power generation) uses a series of tracking mirrors (heliostat) or a paraboloid (three-dimensional parabola or dish) of mirrors to focus solar energy onto it.
Chord line: The imaginary straight line from leading edge to trailing edge of an airfoil, and this distance being the chord.
Coefficient of performance (COP): It is the ratio of performance achieved or useful output or work to the energy or work input. It is a measure of the efficiency of a thermoelectric module, device, or system. Mathematically, COP is the total heat transferred through the thermoelectric device divided by the electric input power.
Co-generation: The technology of producing electric energy and another form of useful energy (usually thermal) for industrial, commercial, or domestic heating or cooling purposes through the sequential use of either rejected heat from industrial processes (bottoming cycle) or surplus heat from an electric generating plant (topping cycle).
Collector fluid: The working fluid in a collector that transfers the heat of solar energy for appropriate applications.
Compressed natural gas: It is natural gas under pressure that remains clear, odourless, and non-corrosive.
Concentrating parabolic trough: It is a large, U-shaped (parabolic) reflectors (focusing mirrors) that have oil-filled pipes running along their centre or focal point. The mirrored reflectors are tilted toward the sun, and focus sunlight on the pipes to heat the oil inside to as much as 400°C. The hot oil is then used to boil water, which makes steam to run conventional steam turbines and generators.
Concentrator: Optical components such as lenses (Fresnel lens) to direct and concentrate sunlight onto a solar cell of smaller area. They can increase the power flux of sunlight hundreds of times.
Condenser: An equipment that condenses turbine exhaust steam into condensate.
Crust: Earth’s outer layer of rock, which is also called the lithosphere.
Conduction band (or conduction level): It is an energy band in a semiconductor that accepts electrons from valence band where they can move freely in a solid, thereby producing a net transport of charge.
Copper indium diselenide (CuInSe2 or CIS): It is a polycrystalline thin-film photovoltaic material (sometimes incorporating gallium (CIGS) and/or sulphur).
Cooling tower: A structure in which heat is removed from hot condensate.
Couple: A pair of thermoelectric elements consisting two dissimilar materials (such as one N-type and one P-type) forming junctions and maintained at different temperatures.
Crystalline silicon: It is a slice of single-crystal silicon or polycrystalline silicon crystals having very good thermal, electrical, mechanical, and photon absorbing properties for application in solar photovoltaic, thermoelectric devices.
Cut-in-speed: The lowest wind speed at which a wind turbine begins producing usable power.
Cut-out-speed: The highest wind speed at which a wind turbine stops producing power.
Declination: It is the angular position of the sun at solar noon with respect to the plane of the equator.
Degrees Kelvin: It is a temperature scale designed so that 0°K is defined as absolute zero. In a later date, the name Kelvin (symbol K) instead of degree Kelvin (symbol °K) was used to define the unit of thermodynamic temperature.
It is defined as the fraction (1/273.16) of the thermodynamic temperature of the triple point of water. The Celsius scale 0°C equals 273.15K.
Dehydration: The removal of a substantial portion of the water from any substance.
Delta T: The temperature difference between the cold and hot sides of a thermoelectric module. Delta T may also be expressed as ΔT.
Density: The mass of a material per unit volume. It is often expressed as pounds per cubic foot or grams per cubic centimetre or kilogram per cubic metre.
Diffuse insolation: Sunlight received indirectly as a result of scattering due to clouds, fog, haze, dust, or other obstructions in the atmosphere. The rate at which this energy falls on a unit horizontal surface per second is called the diffuse solar insolation (or irradiance).
Diffuse radiation: Diffuse solar radiation is the result of the atmosphere attenuating, or reducing the magnitude of the Sun’s beam. Some of the energy removed from the beam is redirected or scattered towards the ground. The radiation received from the sun after reflection and scattering by the atmosphere and ground.
Digester: It is a huge tank constructed underground in which biodegradable organic matters are decomposed by anaerobic bacteria into methane and carbon dioxide.
Direct beam radiation: The radiation received by direct solar rays. It is measured by a pyrheli-ometer with a solar aperture of 5.7° to transcribe the solar disc.
Direct current (DC): It is the unidirectional flow of electric current.
Direct Insolation: It is also called as beam radiation that describes solar radiation traveling on a straight line from the sun down to the surface of the earth.
Distillation: It is a process of separating the component substances from a liquid mixture by boiling (evaporating) and re-condensing the resultant vapours.
Distributed energy resources (DER): A variety of small, modular power-generating technologies that can be combined with energy management and storage systems used.
Distributed generation: A popular term for localized or on-site power generation.
Distributed power: Generic term for any power supply located near the point where the power is used.
Distributed systems: Small-scale generating technologies (e.g., solar, wind, CHP, hydro or newer technologies) that are connected to the local electric power grid are identified as distributed systems.
Distributed generation (DG): It allows customers to be powered by their own electric generation systems as opposed to central systems of electricity supply through national grids.
Diurnal, daily, or the daily cycle: It refers to patterns of happening or recurring at regular intervals within a 24-h period.
Downdraft gasifier: A gasifier in which the product gases pass through a combustion zone at the bottom of the gasifier.
Downwind turbine: The downwind turbine refers to a horizontal axis wind turbine that has its rotor on the back side of the turbine. The nacelle typically is designed to seek the wind, thus negating the need for a separate yaw mechanism.
Drying: Moisture removal from biomass to improve serviceability and utility.
Ebb generation: The generation of electricity in a tidal power plant from a head of water created by the incoming tide trapped behind tidal barrage and by allowing the trapped water through turbine during low tides.
Efficiency: It is a ratio of performance achieved to the input to the system, where performance achieved and input both are expressed in same unit of measurement.
Electro deposition: It is an electrolytic process to deposit a dissolved or suspended substance on an electrode by electrolysis.
Electrochemical cell: It is a device used for either producing electrical energy from chemical reactions or causing chemical reactions through the application of electrical energy.
Electrode: It is a conductor that passes an electrical current from one medium to another.
Electrolyte: A substance that dissociates into ions in solution and acquires the capacity to conduct electricity.
Electromagnetic radiation: The energy produced by an oscillating electrical (and magnetic) field and transmitted by photons.
Emissivity: It is defined as the ratio of the energy radiated from the surface of a material to that radiated from a blackbody (a perfect emitter) at the same temperature and wavelength under the same viewing conditions.
Energy: It is the ability to do work. The relationship between power and energy is
Equation of time (EOT): It is a formula used in the process of converting between solar time and clock time to compensate for the earth’s elliptical orbit around the sun and its axial tilt and is given as
D = n(360°/365), and n is the number of the day counted from January of year (e.g., Feb. 1 makes n = 32).
Equinox: It means equal day and night. When the number of hours of daylight equals the number of hours of night in one day (24 h period). The vernal equinox, usually March 21, signals the onset of spring, while the autumnal equinox, usually September 21, signals the onset of autumn.
Ethanol (CH3CH2OH): A colourless, flammable liquid produced by fermentation of sugars. It is used as a fuel oxygenate. Further, it is the alcohol found in alcoholic beverages, but is denatured for fuel use. Examples of these systems include central receiver systems, parabolic dish, and solar trough.
Extraterrestrial radiation: It is the amount of global horizontal radiation that a location on earth would receive if there was no atmosphere or clouds (i.e., in outer space).
Feedstock: Any raw material used in energy conversion process for conversion to another form of fuel or energy product.
Fermentation: A metabolic biochemical reaction in which bacteria or yeasts that breaks down (ferment) complex organic molecules (like carbohydrates) into simpler materials (such as ethanol, carbon dioxide, and water).
Figure of merit: It is a measure of the overall performance of a thermoelectric device or material.
Fill factor: The ratio of a photovoltaic cell’s actual power to its power if both current and voltage are at their maxima.
Fixed tilt array: A photovoltaic array set in at a fixed angle with respect to horizontal.
Flat plate heat exchanger: A flat plate heat exchanger is an installation where heated water on one side transfers the heat onto the other side of flowing water. Both sides must have a circulating fluid.
Flat plate array: A photovoltaic (PV) array that consists of non-concentrating PV modules.
Flat plate module: An arrangement of photovoltaic cells on a substrate of metal or glass or plastic to provide structural rigid flat surface support on the back, solar cell protecting encapsulate material and a transparent cover of plastic or glass so that cells exposed freely to incoming sunlight.
Flat plate photovoltaic (PV): A PV array of flat plate module that consists of non-concentrating elements.
Fluidized bed: It is a gasifier or combustor in which fuel particles are suspended in a hot, bubbling fluidized bed of ash and other particulate materials (sand, limestone, etc.).
Fly ash: Small ash particles carried in suspension in combustion products.
Focusing collector: A collector that enhances solar energy by focusing it onto a smaller area through mirrored surfaces or lenses.
Forestry residues: It includes the remains of forest trees and plants after the harvest of crop and forestry products such as tops of trunks, stumps, branches, and leaves.
Free electrons: Any unattached electron from an ion, atom, or molecule that is free to move under the influence of an applied electric or magnetic field.
Fresnel lenses: An optical device usually made of glass or plastic that focuses light like a magnifying glass. Concentric rings are faced at slightly different angles so that light falling on any ring is focused to the same point.
Fuel cell: A device that converts the chemical energy of a fuel directly to electricity and heat without combustion.
Furling: The act of a wind generator by which turning rotor out of the wind as wind speed reaches cut out speed to protect itself from high wind speeds.
Fumaroles: A vent or hole in the earth’s surface from which volcanic gas, steam, etc., escape into the atmosphere.
Gallium arsenide (GaAs): It is a crystalline, high-efficiency compound semiconductor. It is mixture of two elements gallium (Ga) and arsenic (As) and is used to make certain types of solar cells and semiconductor material.
Gas turbine: It is a type of internal combustion engine that converts the energy of hot compressed gases (produced by burning fuel in compressed air) into mechanical power.
Gasification: A chemical or heat process to convert a solid fuel to a gaseous form.
Gasifier: A device for converting solid fuel into gaseous fuel. In biomass systems, the process is also referred to as pyrolytic distillation.
Geothermal energy: The earth’s interior heat made available to man by extracting it from hot water or rocks.
Geothermal gradient: It is the rate of temperature increase in the earth as a function of depth.
Geyser: A hot spring that erupt jets of hot water and steam into the atmosphere.
Global warming: A term used to describe the increase in average global temperatures due to the greenhouse effect.
Greenhouse effect: It is a natural process that warms the earth’s surface in which the solar radiant energy is trapped by greenhouse gases produced from both natural and human sources.
Greenhouse gas: Gaseous components in the atmosphere (such as water vapour, carbon dioxide, troposphere ozone, methane, and low level ozone) that contribute to a gradual warming of the planet.
Heat engine: It is an equipment that converts thermal energy into mechanical energy output. They often pick up alternate names, such as gasoline or petrol, turbine, or steam engines.
Heat exchanger: A device for transferring thermal energy from one fluid to another.
Heat pump: It is a device that is able to transfer heat from one fluid at a lower temperature to another at a higher temperature.
Heliostat: They are computer-controlled large flat mirrors that keep the sun reflected on a target as the sun moves across the sky so that it can continuously reflect the sun’s rays onto a central receiver.
Horizontal axis wind turbine: A wind turbine design in which the shaft is parallel and the blades are perpendicular to the ground.
Hub: The central part of the wind turbine, which supports the turbine blades on the outside and connects to the low-speed rotor shaft inside the nacelle.
Hydrocarbon: An organic compound that entirely contains only hydrogen and carbon.
Hydrothermal resource: An underground system of hot water and/or steam.
Insolation: Solar radiation on the surface of the earth and is usually expressed as watts per square metre. This term has been generally replaced by solar irradiance because of the confusion of the word with insulation.
Inverter: An equipment that is used to convert a direct current into an alternating current.
Irradiance: It is a measure of total solar power radiation that strikes a surface on the earth. It is also expressed in kilowatts per square metre.
I–V curve: They are curves that show the relationship between the current flowing through an electronic device and the applied voltage across its terminals.
Kelvin: The temperature unit based on the theoretical minimum temperature used in many physical calculations. The relationship between Kelvin and Celsius is K = C + 273.16.
Latent heat: Thermal energy required to cause a change of state of a substance such as changing water into ice or steam.
Local apparent time: The time of day based strictly on the longitude of the locality and not on ‘blocky’ time zones.
Local standard time: The time of day based on the longitude of the zone meridian associated with a locality.
Longitude: The East–West angular distance of a locality from the Prime Meridian. The Prime Meridian is the location of the Greenwich Observatory in England and all points North and South of it.
Magma: A molten rock within the earth, from which igneous rock is formed by cooling.
Mantle: It is one of the three main layers of the earth that lies between the innermost layer (the core) and the thin outermost layer (the crust).
Mass flow rate: It is the mass of a substance that passes per unit of time through a given cross-sectional area.
Methane (CH4): It is a colourless, odourless, non-toxic, and flammable gas and is the most simple of the hydrocarbons.
Methanol (wood alcohol) (CH3OH): An alcohol formed by catalytically combining carbon monoxide with hydrogen in a 1:2 ratio under high temperature and pressure.
Methanol, denatured ethanol, and other alcohols, separately or in blends of at least 10% by volume with gasoline or other fuels.
Microorganism: Any microscopic organism such as yeast, bacteria, and fungi.
Municipal solid waste: It includes commercial and residential, garbage, refuge, rubbish wastes generated in municipal or notified areas in either solid or semi-solid form.
Nacelle: A housing structure for rotor shaft, gearbox, and generator at the top of the wind turbine tower just behind (or in some cases, in front of) the wind turbine blades.
Non-renewable resource: Energy resource that is once exhausted cannot be refilled or restored by nature.
Ocean thermal energy conversion (OTEC): The energy conversion technologies used for electricity generation by using the temperature differences (thermal gradients) between warm ocean surface waters and cool ocean depth waters.
Oil shale: It is any sedimentary rock that contains solid bituminous materials (called kerogen) that are released as petroleum-like liquids hydrocarbons called shale oil.
Organic compound: An organic compound contains carbon chemically bound to hydrogen that may also contains other elements particularly O, N, halogens, or S.
Ozone layer: It is the ozone shield of high concentrations of ozone (O3) refers to a region of earth’s stratosphere that absorbs most of the sun’s UV radiation.
Ozone: It is most stable form of elemental oxygen in the upper atmosphere and protects the earth from the sun’s ultraviolet rays.
Particulates: A fine liquid or solid particle such as dust, smoke, mist, fumes, or smog, found in air or emissions.
Passive solar technologies: Technologies that capture sunlight for heat energy without use of active mechanical systems and convert sunlight into usable heat (water, air) or store heat for future use.
Peltier effect: When an electrical current is passed through a junction consisting of two dissimilar metals, it results in a cooling effect.
Phase change: The change of a substance from a liquid to solid, liquid to gas, etc.
Photovoltaic: It is a process in which the light is converted into electricity through the displacement of electrons and the current created as a result. Photovoltaic are the basis for the operation of solar panels.
Photoelectric: It is the conversion of light (radiant energy) to electricity.
Photometer: An instrument that measures luminance.
Photons: A photon is an elementary particle and the basic unit of light.
Photosynthesis: A process used by plants and bacteria to produce carbohydrates from carbon dioxide and water using solar light energy. Photosynthesis is the key initial step in the growth of biomass and is given by the equation:
Photovoltaic (PV) array: An interconnected system of large number of PV modules to provide high voltage and power unit with common support or mounting.
Photovoltaic (PV) cell: The smallest semiconductor single element (solar cell) within a PV module to perform the immediate conversion of light into electrical energy (direct current voltage and current).
Photo conversion: A process of conversion of light into other forms of energy by chemical, biological, or physical processes.
Photovoltaic (PV) conversion efficiency: It is the ratio of the electrical output of a solar cell to the incident sunlight energy on it.
Photovoltaic (PV) device: A solid-state electrical device (solar cell device) that converts light energy directly into direct current electricity.
Photovoltaic (PV) effect: The phenomenon that occurs when photons strike the atoms to free electrons.
Photovoltaic (PV) generator: It is the total of all photovoltaic panel connected to solar electric grid.
Photovoltaic (PV) system: A complete set of components for converting sunlight into electricity.
Photovoltaic array: A photovoltaic module or set of modules used for converting solar radiation to energy.
Photovoltaic module: An unit comprising several photovoltaic cells that are the principal unit of photovoltaic array. A photovoltaic module’s size is on the order of 1 m2, although its size is governed by convenience and application.
Photovoltaic(s) (PV): It is the direct conversion of light into DC electricity.
Point-focusing concentrator: A solar power generator that uses a series of tracking mirrors (heliostat), Fresnel lenses, or paraboloidal (three-dimensional parabola or dish) mirrors to focus solar energy onto a single central receiver.
Polycrystalline silicon: A material used to make photovoltaic cells.
Polymer: A large molecule made by linking smaller molecules (monomers) together.
Propeller: It is a type of device that transmits power by converting rotational motion into thrust.
P-type material: Semiconductor materials that are doped to have a deficiency of electrons.
Pyranometer: An instrument used for measuring global solar irradiance.
Pyrheliometer: An instrument used for measuring direct beam solar irradiance.
Pyrolysis: It is a thermo-chemical decomposition of organic material at elevated temperatures in the absence of oxygen.
Rankine cycle: It is an idealized thermodynamic cycle of a heat engine converting heat into mechanical energy.
Recycling: The process of converting materials that are no longer useful as designed or intended into a new product.
Renewable energy resource: Any energy resource that is continuously renewed by nature.
Residues, biomass: A by-product (residues or wastes) from processing all forms of biomass have significant energy potential for energy or fuel recovery.
Electrical resistivity: It is the measure of how strongly a material opposes the flow of an electrical current.
Salt gradient solar ponds: They consist of three main layers having different salt concentrations. The top layer is near ambient and has low salt content. The bottom layer is hot (typically 71°C–100°C) and is very salty.
Scrubber: It is an air-stream pollution control device used to remove solid and liquid particulate matter (by washing them out) and gaseous pollutants (either by absorbing or by chemically neutralizing) with the help of liquid spray.
Seebeck effect: When the two junctions formed by two dissimilar metals are maintained at temperature gradients (one junction is hot and the other is cold), an electrical current will flow in a load circuit connected to both junctions.
Selective absorber: A solar absorber surface having high absorbance at solar spectrum wavelengths and low emittance in the infrared range.
Selective surface coating: A material with high absorbance and low emittance properties applied to or on solar absorber surfaces.
Selective coating: Visible light represents different wavelengths that have various energies. In brief, the wavelengths below 380 nm is UV light between 380 nm and 780 nm is visible light, 780 nm and 2,500 nm is near infrared light, and above 2,500 nm is far infrared light. A selective coating transmits light in the range from 360 nm to 2,500 nm, while it will block light or energy above 2,500 nm. In practice, this means that the coating will allow short wave solar light to enter, while long wave energy from the solar collector will be reflected back on the flowing liquid.
Shale oil: It is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution.
Silicon-germanium: A high temperature (range of 500°C-l,000°C) thermoelectric semiconductor material that exhibits its optimum performance.
Silicon (Si): A non-metallic chemical element in the carbon family that is present in sand and glass and which the best known semiconductor is.
Sluice gate: An artificial passage for water fitted with a valve or gate in barrage or dam for stopping or regulating flow.
Solar altitude angle: It is the angular height of the sun measured from the horizon.
Solar array: A group of solar panels collectively makes up a solar array.
Solar cell or photovoltaic cell: A device that converts solar light energy directly into direct current electricity by the photovoltaic effect.
Solar constant: It is defined as the average amount of solar radiation that reaches the earth’s upper atmosphere on a surface perpendicular to the sun’s rays, in the range of 1,353–1,367 w/m2. The currently accepted value is 1,366 W/m2.
Solar cooling: The use of solar thermal energy or solar electricity to power a cooling equipment.
Solar energy: It is the radiant energy from the sun that influences earth’s climate and weather and sustains life.
Solar hours: These are the number of hours with a clear blue sky and sunshine during a timeframe.
Solar irradiance: It is solar power per unit area (kW/m2) on the earth’s surface in the form of electromagnetic radiation.
Solar noon: It is defined when the sun is at the zenith (directly above the head of the observer).
Solar panel: A series–parallel connection of solar cells for desired power output.
Solar pond: A pond full of saltwater that acts as a large-scale solar thermal energy collector with integral heat storage for supplying thermal energy.
Solar power: The power (electricity) generated from the solar energy.
Solar spectrum: It is the intensity of sunlight (irradiance) variation over wavelength for given atmospheric condition.
Solar thermal electric systems: Technologies that convert solar thermal energy into electricity.
Specific gravity: The ratio of the mass of any material to the mass of an equal volume of water at a temperature of 4°C.
Specific heat: It is the amount of thermal energy required to raise the temperature of a given substance by one degree when compared to the energy required to raise the temperature of an equal mass of water by one degree. The specific heat of water is 1.000.
Stand-alone system: A system that provides continuous power without any support from other systems.
Stirling engine: It is an external combustion engine that operates by cyclic compression and expansion of the working fluid at different temperatures,
Subsidence: Cavity formation in the earth’s crust owing to fluid and energy raw resource extraction.
Substrate: A supporting material on which a circuit is formed or fabricated or enzyme acts or organism grows.
Surface work function: A measure of the electron-emitting capacity of the surface.
Tar: It is a black mixture of hydrocarbons.
Thermal conductivity: It is the property of a material to conduct heat and its units is W/(mK)
Thermionic energy conversion: An energy conversion process in which heat energy is directly converted into electrical energy by the phenomena of thermionic emission.
Thermoelectric generator: A device that directly converts heat energy into electrical energy when one junction of two dissimilar metals are kept hot and the other junction is kept cool (Seebeck effect).
Tidal barrage: A concrete dam constructed in ocean to store water during tides with sluices.
Tidal or wave farming: A method of harvesting tidal power that relies on underwater turbines.
Thomson effect: It is the absorption or evolution of heat along a conductor having temperature difference at the two ends when current passes through it.
Tidal energy: Tidal energy, tidal power, wave energy, and wave power are terms used interchangeably. These terms describe the methods of creating energy from the movement of water due to the ocean tides, ocean waves, and currents in rivers.
Toxics: Poisonous and environmentally unfriendly.
Turbines: The mechanical component of electricity generating systems that creates electricity. Turbines rotate as water, air, or steam push the blades of a rotor.
Turbulence: Air, water, or other fluid unsteady or violent movement.
Ultraviolet radiation: The range of radiation just beyond the violet in the visible spectrum (at about 4,000 Angstroms or 400 nm) to the X-ray region (at about 40 Angstroms or 4 nm).
Vapour dominated: A hydrothermal system having dominance of vapour or steam.
Vertical-axis wind turbine (VAWT): A type of wind turbine in which the rotor of the turbines rotate vertically around its axis.
Viscosity: A fluid property related to the interaction between fluid molecules that determines the fluids’ resistance to sheering forces and flow.
Watt: A watt is a unit of measure for electrical energy. It is equal to one joule of energy per second.
Wind energy: The energy caused by the earth’s weather patterns creating high and low pressure centres forcing wind to rush from high to low pressure.
Wood: The hard fibrous material substance obtained from the trunk, branches, and root of a tree or shrub.
Yeast: Any of various single-cell fungi capable of fermenting carbohydrates.
Zenith angle: It is the angle between the geometric centre of the sun and directly overhead of the observer.