Solar Glossary


1. Electricity Act, 2003 The Electricity Act, 2003 (and subsequent amendments) consolidates the laws relating to generation, transmission, distribution, trading, and use of electricity. The Act was brought in to support the  development of electricity industry by taking steps to rationalize electricity tariffs, ensure transparent policies regarding subsidies, promote competition, and protect the interests of consumers . 
2. Auxiliary Energy Consumption Auxiliary consumption is the energy consumed by the auxiliary equipments (which help in running the power plants). The auxiliary consumption for a solar thermal power plant is considered to be 10%, and the consumption for a solar PV plant is considered to be negligible.
3. Billing Cycle The period for which regular electricity bills are prepared for different categories of consumers by the State power distribution companies.
4. CUF 


Utilisation Factor)

CUF is a metric to measure the performance of a solar power plant. It is the ratio of actual energy generation (in kWh) to the energy generation (in kWh) under ideal conditions, over a year.
5. CERC The Central Electricity Regulatory Commission (CERC) is a regulatory body in the power sector that, among other things, formulates and amends the electricity regulations, assists in setting tariffs for central generating companies, and resolves disputes between key stakeholders. 
6. COD (Date of commercial operation) The date on which the generating plant is synchronized with the grid and starts generating quantifiable power.
8. Contracted Load/ Contract Demand The maximum demand in kW, kVA, or HP, agreed to be supplied by the Distribution Licensee and for which the consumer agrees to pay for to have available at all times.
9. Discom/ Distribution Licensee/ EB The entity operating and maintaining a distribution system for supplying electricity to consumers.
10. kWp kilowatt peak is the rate at which a solar power system generates electricity at peak conditions. 
11. EPC An EPC (Engineering Procurement & Construction) company, in the solar context,  refers to a company that takes up the work of design, supply, procurement, installation, and commissioning of a solar power plant, on contract.
12. Gross Metering Gross metering is a billing mechanism that  measures the total solar power generated without accounting for self-consumption. Under gross metering, the consumer is usually incentivised for the solar electricity generated and injected into the grid..
13. Grid Grid is the interconnected system of transmission lines, sub-stations, and generating plants for sale of energy or wheeling of energy. It could refer to the low-voltage electrical network, the distribution and transmission network, or high-voltage networks.  
14. Installed Capacity The summation of the rated capacities ( in kWp) of solar panels in a solar plant..
15. Interconnection Point The point at which the solar power plant is connected to the distribution network of the distribution licensees at the appropriate voltage level. 
16. MNRE It is the central government ministry that oversees the promotion and development of renewable energy in India. (
17. Net metering Net metering is a mechanism that allows additional energy generated by a solar power plant to be fed back into the grid. The producer can accumulate credits that can then be offset against the electricity that was consumes/importes..  A bi-directional meter is used to measure the excess energy fed into the grid and the consumer is billed for only the net energy used/ imported from the grid.
18. Prosumer Aconsumer who is also a producer of solar power.
19. Open access consumer A consumer permitted by the respective transmission/distribution licensee to purchase electricity from an entity other than the transmission/distribution Licensee in their area of supply.
20. Photovoltaics (PV)  Photovoltaic technology is the process of conversion of sunlight into electricity using semiconducting material. A photovoltaic cell, commonly known as a solar cell, is a device that uses photovoltaics to convert light energy into electricity.
21. PPA An agreement signed between 2 parties – the generator/developer and the consumer/purchaser – for the purchase/sale of electricity for a specified period of time at a specified tariff.
22. Premises In the solar context, it means any spaceon land, atop a building, or   a combination of the two, where a rooftop or ground-mounted solar power system is installed.
23. REC Mechanism REC (Renewable Energy Certificate) is a mechanism by which a power consumer can purchase tradable certificates from a renewable energy producer and use the certificates to meet his renewable purchase obligation. The mechanism was introduced to propel the growth of renewable energy.


Renewable Energy Certificate (REC) RECs are certificates issued to a renewable power producer for every MWh of renewable energy generated. The certificates are traded over power exchanges within a price band as determined by Central Electricity Regulatory Commission. RECs can be bought by electricity distribution companies, open access consumers, captive power plants, or any other entities that are mandated to fulfil renewable power purchase obligations set by the government.
25. Renewable Energy Sources Sources of power generation that do not use conventional fuel but use natural sources that do not get depleted such as wind, solar, hydro, biomass, geothermal heat, waves, tides, etc.
26. Renewable Purchase Obligations (RPO) Renewable Purchase Obligation is a mechanism that mandates large power consumers to buy a part of their energy requirements from renewable sources.


27. Build-Own-Operate-Transfer (BOOT)  BOOT is a project model where an entity (A) builds, owns, operates, and maintains a solar power project for or on behalf of another entity (B) for a specified period of time, after which the asset ownership is transferred from A to B.
28. Salvage Value The estimated value of an asset at the end of its useful life.
29. Solar Grid Inverter A device that converts the DC (direct current) power from Solar PV modules to grid-compatible AC (alternating current) power.
30. Solar PV Power Plant A solar power system that converts  sunlight into electricity using semiconducting materials that exhibit photovoltaic effect.
31. Solar Thermal Power Plant A power plant uses the heat of the sun to generate electricity. This is typically done  by concentrating the heat (based on the line focus or point focus principle) to convert water into steam, which is then used to  generate power through a steam cycle turbine.
32. Third Party Owned Power Plant A third party-owned power plant is one where a solar power project developer installs and maintains the project for the purpose of selling power to the electricity consumer.
33. Anti-islanding Anti-islanding is a protection mechanism/safety feature where the grid-tied inverter senses an impending grid outage and shuts itself off from the grid.  This is done to ensure the safety of the personnel working on the grid and prevent feedback of power generated by the solar power plant into the grid.  
34. Anti-reflection coating Anti-Reflective Coating is a layer atop a solar cells that helps increase the amount of light absorbed into the cell.  This coating is essential as the reflection of a bare silicon solar cells is over 30%.
35. Azimuth Angle The azimuth angle is the angle between true south and the point on the horizon directly below the sun. It specifies how many degrees the surface of the photovoltaic module deviates from the exact south-facing direction.The azimuth angle depends on the geographical location of the observer, the date, time and time zone.
36. APPC Average Power Purchase Cost is the weighted average price at which a distribution licensee purchases electricity, including cost of self-generation, if any, in the previous year from all the energy suppliers, excluding short term power purchases and those based on renewable energy. 
37. Backsheet A backsheet is the outermost layer of a solar panel. It protects the components from external conditions such as UV rays, moisture, physical damage, etc., and acts as an electrical insulator.
38. Balance of systems The balance of system (BOS) includes all the components of a solar photovoltaic system other than the photovoltaic panels. The BOS typically includes wiring, switches, a mounting system, solar inverters, a battery bank, and a battery charger.
39. BIPV BIPV is the integration of photovoltaic panels into building envelopes such as the roof, skylights, or facades. Here, the PV system provides two functions – it acts as the building’s skin and produces electricity. 
40. Charge controller A charge controller regulates the voltage and current flowing from the solar panel to the battery and/or the load, and ensures that the safety of the battery is not compromised.
41. Captive solar A captive solar power plant is onet that has been set up by a company for its own captive consumption. The power generated by the solar power plant is consumed entirely by the company that develops the project.
42. Transformer A device that transfers electric energy from one alternating-current circuit to one or more other circuits, by either increasing (stepping up) or reducing (stepping down) the voltage.
43. Unit Unit is a measurement of the electricity used by a consumer. 1 kWh of electricity is considered one unit.
44. Utility Utility is the company that generates, operates, maintains and sells electricity under a regulated environment in a geographical area.
45. Utility-scale solar Solar power plants of large capacities (around XYZ MW), the power from which is sold to utility companies.
46. Voltage Voltage is the force of an electric current, measured in volts.
47. Wafers Solar wafers are slices of semiconductor material that are used to manufacture solar panels. It is an upstream product, produced during the initial stages of the solar panel manufacturing process, made after the polysilicon is processed and before the solar cell is made. 
48. Wheeling charges The charges that a distribution company imposes on a consumer for  the utilization of its infrastructure.
49. Smart grid A grid where the network of generation, transmission, distribution and consumption of electricity are  made smarter by integration with digital technology and communication systems that monitor, and may even control, all aspects of it.
50. Solar farm A geographical area where a large number of solar panels are installed for the purpose of generating electricity.
51. String inverters A string inverter distributes the load of a central inverter to multiple inverters, enabling better power generation. Solar panels are arranged to be strings which feed into a string inverter. String inverters ensure that the output of all the solar panels are not affected if one inverter or string of panels is damaged.
52. Thin-film solar cell A thin-film solar cell is one that is made by depositing one or more thin layersthe thin film (TF)of photovoltaic material on a substrate, such as glass, plastic, or metal.
53. Tracker A tracker is a movable mechanical device attached to a solar power plant. The device tracks the sunlight and ensures that panels are oriented towards the sun through the day, thereby maximizing efficiency and increasing generation.


54. Photon A photon is the smallest discrete amount or quantum of electromagnetic radiation. It is the basic unit of all light.
55. Polysilicon Polysilicon  is a high purity, polycrystalline form of silicon, used as a raw material to manufacture solar photovoltaic panels. 


56. Payback Period Payback period is the  time that will be taken to recover the capital invested for any purpose.


57. Panel Photovoltaic solar panels are devices that absorb sunlight as a source of energy to generate electricity.


58. Panel efficiency Solar cell efficiency refers to the portion of energy in the form of sunlight that can be converted into electricity through the photovoltaic process. A higher efficiency panel can produce more electricity for the same rooftop area compared with lower efficiency panels used in the same given area.


59. PID Potential Induced Degradation is a phenomenon where the performance of a solar panel falls due to stray currents that are produced as a result of difference in voltage with respect to the ground. This happens mainly because the sodium ions of the glass move to the solar cell and pn junction.
60. Rated power It is the highest power input allowed to flow through a particular equipment.
62. Semiconductor A solid substance that has a conductivity value that is higher than  that of an insulator but lower than that of most metals. This could be due to the addition of an impurity or because of temperature effects.
63. Sanctioned demand Sanctioned demand is the approved electrical load (usually in kVA/MVA) granted to a consumer, by the distribution licensee.


64. Group captive A mechanism created under the Electricity Act, 2003, wherein a group of consumers can jointly set up a power plant for captive consumption. The idea is to lower the investment burden for a single consumer by facilitating group investment.


65. High Tension Load HT load refers to supply of electricity from distribution network above a nominal voltage of 660 V but lesser than 66 kV. Extra High Tension (EHT) supply is at or above 66 kV.



66. Ingots A  block of silicon, typically oblong in shape.


67. LCOE Levelized cost of electricity (LCOE) represents the kilowatt-hour cost of building and operating a power generation plant over an assumed financial life cycle. 


68. Micro-inverter Small-sized inverters that are connected to individual panels instead of a string of panels in order to extract  maximum power from each. 
69. MPPT Maximum Power Point Tracking is an algorithm that is included in charge controllers and inverters to extract maximum power from solar PV modules. They match current and voltage levels to ensure maximum power extraction, on the AC side.


70. MWh (Megawatt-hour) Megawatt-hour is a unit for measuring energy. 1 MWh = 1000 kWh (or units, in electricity parlance)


71. Multi-crystalline Panels Multicrystalline solar panels are made from multiple silicon crystals.  They are made up of solid silicon composed of crystallites/grains of varying sizes and orientation. They have a  lower silicon crystal purity and are not as efficient as monocrystalline panels.
72. Monitoring Systems Monitoring systems are built into a solar system to record  information on factors, such as weather conditions, that influence energy generation.


73. Mounting structure Module mounting structures are used to fix solar panels on surfaces such as roofs, building facades, or the ground, and aid in withstanding wind loads.


74. Off-grid An off-grid system is a power plant that is not connected to the grid. An off-grid power plant can be connected to a battery to store any excess energy for future use. The biggest advantage of an off-grid system is that it reduces the dependency on the grid for electricity.


75. On-grid An on-grid or grid-tied system is connected to the grid. Any excess power generated can be exported to the grid, and additional energy requirements can be supported through the grid.
76. Overcharging Overcharging is when the current supplied by a solar panel to the battery is more than the storage capacity of the battery.


77. Pyranometer A pyranometer is an instrument used to measure the solar radiation that falls on the earth’s surface. 


78. Crystalline silicon solar cells Crystalline silicon photovoltaics are solar modules built using crystalline silicon solar cells (c-Si), developed from the microelectronics technology industry.


79. Cross Subsidy Surcharge Cross subsidy surcharge is the charge levied on a certain group of consumers to make up for subsidies given to another group of consumers. In the context of open access in India, it is applicable to consumers purchasing power privately through the third party mode.


80. DNI Direct Normal Irradiance (DNI) is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays from the direction of the sun at its current position in the sky.


81. Diffuse Radiation Diffuse radiation is the part of solar radiation that reaches the earth’s surface after it gets scattered by air particles, moisture, aerosol, dust, etc. present in the air.
82. DISCOM Discoms or distribution companies are private or government-owned entities that own and operate the electricity distribution infrastructure, and supply power to consumers. 


83. DC cable A solar DC cable is an interconnection cable used in photovoltaic power generation. They connect solar panels and other electrical components of a photovoltaic system to the inverter.


84. Dual-glass panels These are solar panels that can absorb solar radiation from both sides. The construction is such that the conventional backsheet and glass structure is replaced by a frameless panel with tempered glass on both sides.
86. Encapsulant It is a co-polymer film that is used as an essential sealant on  photovoltaic solar modules. Encapsulant sheets play an important role in preventing water and dirt from infiltrating into solar modules, and  protect the cell by softening the shocks and vibrations to the cell.



87. Feed-in-tariff Feed-in tariffs (FIT) are fixed electricity prices that are paid to renewable energy (RE) producers for each unit of energy produced, and excess power injected into the electricity grid.


88. Floating solar panels: An array of photovoltaic panels mounted on a structure that floats on a body of water, typically a reservoir or lake.


89. Grid parity: Grid parity occurs when a renewable energy source can generate power at a levelized cost of electricity that is less than or equal to the price of purchasing power from the electricity grid or a conventional power plant.
90. Solar Irradiation /Insolation Irradiation, also called insolation, is a measure of solar radiation energy received on the earth’s surface at a given time. 


91. Tilt Angle The angle between the ground and the solar module installed on a mounting structure.

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