1. Active system

Solar heating system requiring external mechanical power to move the collected heat.

2. Antireflection Coating

A thin coating of a material applied to a solar cell surface that reduces the light reflection and increases light transmission.

3. Array

A set of photovoltaic panels connected together designed to produce a significant amount of electricity. A home solar electric system might include several arrays on different parts of the roof.

4. Azimuth

The direction a solar electric system faces (e.g. north, south, east, west).

5. Balance of system

All the parts of a solar electric system excluding the solar panels and the inverter. Balance of system usually includes items like racking, wires, conduit, and safety shut-offs.

6. Base load

The average amount of electric power that a utility must supply to meet the energy demand.

7. BTU

British Thermal Unit(s). A measure of energy output defined as the amount of heat needed to raise one pound of water 1°F from a starting point of 39.2°F. Common unit in measuring solar hot water performance and sizing gas-fired water heaters.

8. Building permit

Authorization from the local building inspection agency to construct or modify a building from an approved set of plans, usually required for solar energy installations.

9. Carbon dioxide (CO2)

The colorless and odorless gas, is a natural air component. It is, however, also created in huge quantities by the burning of fossil energy sources. Due to its excessive accumulation in the atmosphere, it has a greenhouse effect on the atmosphere and it is responsible in part for global warming.

10. Cell

The smallest part of a solar panel that converts light into solar electricity.

11. Closed loop system

Solar hot water system in which the fluid circulated throughout the solar thermal collectors is separate from the potable water. In a closed loop solar system, the solar heat is transferred to the potable water by way of a heat exchanger.

12. Closed-loop system

Solar hot water system in which the fluid circulated throughout the solar thermal collectors is separate from the potable water. In a closed loop solar system, the solar heat is transferred to the potable water by way of a heat exchanger.

13. Conductivity

A measure of the ability of a material to permit conduction of heat flow through it.

14. Conductor

A material that conducts or allows the flow of heat, electricity, or other forms of energy.

15. Conduit

A piping system that protects and routes electrical wiring.

16. Conversion efficiency

The percentage of the sunlight incident on a solar panel that is successfully passed to the system as current.

17. Data monitoring

These systems are installed after the solar electricity system and record the amount of electricity generated, thus providing information about the current operation of the installation. Today, monitoring is possible via Internet, cell phone or large-format displays.

18. Degradation

(1) The disintegration or deterioration of the parts or materials beyond a repairable condition, thus requiring replacement. (2) The loss of efficiency of solar cells over a long period of time.

19. Direct Current (DC)

A type of low voltage electrical current. DC electricity is produced by solar cells and must be converted, by the inverter, into AC before it is usable in a house.

20. Drainback system

A closed-loop solar hot water system that uses an atmospheric pressure drainback tank. In order to avoid freezing or overheating the water flowing through the collectors drains back into a storage tank when not being pumped. A coil-type heat exchanger in the tank then transfers the solar heat to the targeted fluid.

21. Electric current

A flow of electrons; electricity, amps.

22. Energy Audit

A survey that shows how much energy used in a home, which helps find ways to use less energy.

23. Expansion tank

A tank used in a hot water system or radiant heating system that provides space for the expansion of the heat transfer fluid.

24. Fixed tilt array

A photovoltaic array set in at a fixed angle with respect to horizontal.

25. Flat plate collector

A solar energy collection device in which sunlight is converted into heat using a metal plate, typically copper, over which the water flows. It typically consists of a metal frame, glazing (protective sheet of glass or plastic), energy absorbers (usually metal), and insulation and uses a pumped liquid as the heat-transfer medium.

26. Glycol System

An active closed loop system that uses a heat-transfer fluid, made up of a food grade glycol mixture, that collect heat from the rooftop collector and transfers it to a heat exchange coil in the tank.

27. Grid

A system of high tension cables in a region that distributes electricity to homes, businesses, and other buildings

28. Grid tied

A solar system that is connected to the power grid and uses the utility grid as a backup source of power and feeds the excess electricity it generates back into the electricity grid.

29. Ground mount

A solar electrical system that is mounted on the ground instead of on a roof.

30. Heat exchanger

Device that transfers heat. In solar hot water systems the heat exchanger will transfer heat from the fluid in the solar collector loop to the potable water.

31. Interconnection

The process of hooking up a solar electrical system to the power grid.

32. Interconnection Inspection

Inspection performed by the utility to confirm that the system can be safely connected to the power grid.

33. Inverter

The electrical device that converts direct current (DC) electricity that is generated by the solar panels into alternating current (AC) electricity. It is the link between the solar modules and the electricity grid.

34. Junction Box

A photovoltaic (PV) generator junction box is an enclosure on the module where PV strings are electrically connected and where protection devices are located.

35. Kilowatt

One thousand watts.

36. Kilowatt-hour (kWh)

1 kWh = 1,000 watts of power over the period of one hour. A kWh is the unit of energy.

37. Legacy Costs

Large commercial systems (above 70kw) get their incentives paid out over time. Only the first year of those incentives are collected and awarded in the first year that the system is reserved. Subsequent payments, typically lasting for the 10-15yr range, are yet to be collected from ratepayers. Legacy costs are these future collections that are required but have not yet been collected.

38. Load

A load is anything that consumes electricity, and is usually expressed in watts or kilowatts. Typical loads within a house include lights, appliances, etc. Although, the whole house can be considered as a 'load' on the grid.

39. Megawatt

One million watts.

40. Module

A solar panel, or a group of solar cells.

41. Monocrystalline panel

A solar panel that's made from a large, single silicon crystal and has a patchwork pattern. Monocrystalline panels are more expensive and more efficient than multi- or poly- crystalline panels.

42. Multicrystaline panel

(Also known as "polycrystalline") A solar panel that's made from small silicon crystals oriented in many different directions. Multicrystalline panels are less expensive and less efficient than monocrystalline panels.

43. Net Meter

An electricity meter than tracks how much electricity your solar system puts into the power grid and how much electricity your home pulls out of the grid.

44. Open loop system

A solar hot water system where the solar energy is transferred directly to the potable water running through the solar collector.

45. Performance Based Incentive (“PBI”)

Incentive based on a rate per kWh output or equivalent kWh of energy savings.

46. Photon

A particle of light that acts as an individual unit of energy.

47. Photovoltaic

Also known as “PV”, the process of converting light into electricity.

48. Photovoltaic (PV) efficiency

The ratio of electric power produced by a cell to the power of the sunlight striking the cell. TFS installs modules with the highest efficiency available for the residential market.

49. Plot plan

A plan view drawing (bird's eye view of an the area being designed) of a site which includes: the dimensions of the site and its key elements; the location of any structures in relation to one another and to the property boundaries; the elevations of key points; contour lines; utility services; and compass directions.

50. Polycrystalline

See multicrystalline.

51. Power Conversion Efficiency

The ratio of output power to input power of the inverter.

52. Power purchase agreement (PPA)

A contract between a power producer and a power consumer, which states that the consumer will purchase a certain amount of power from the producer.

53. PTC rating

Stands for “PVUSA Test Conditions,” which were developed to test and compare PV systems. The PTC rating, which is lower than the STC rating, is generally recognized as a more realistic measure of PV output because the test conditions better reflect "real-world" solar and climatic conditions, compared to the STC rating.

54. Rated Power

Rated power of the inverter.

55. Remote systems

Systems off of the utility grid. See "Stand alone systems."

56. Renewable Energy Credit (“REC”)

One Renewable Energy Credit is created for each kWh, or kWh equivalent for non-generating resources, derived from an eligible renewable energy resource.

57. Series connection

A way of joining photovoltaic cells by connecting positive leads to negative leads; this configuration increases the voltage.

58. Solar thermal collector

A device designed to receive solar radiation and convert it into thermal (heat) energy in order to heat water. Generally, a collector is composed of a sturdy frame, an absorber (heat absorbing panel with water channels), glazing (protective sheet of glass or plastic) on the sun-facing side, and insulation on the back and sides.

59. Stand-alone system

An electricity system not connected to a grid. Most stand-alone systems require batteries or some other form of storage.

60. Stand-Off Mounting

Technique for mounting a photovoltaic array on a sloped roof, which involves mounting the modules a short distance above the pitched roof and tilting them to the optimum angle.

61. STC

Stands for �Standard Test Conditions.� These are controlled conditions under which a module is typically tested in a laboratory. Output rating of a module is typically based on output measured when subjected to these conditions

62. Stratification

Condition resulting from the tendency for heated fluids to rise and colder fluids to sink, resulting in the temperature layering of water within a tank.

63. String

A number of photovoltaic modules or panels interconnected electrically in series to produce the operating voltage required by the load.

64. Superstrate

The covering on the sun side of a PV module, providing protection for the PV materials from impact and environmental degradation while allowing maximum transmission of the appropriate wavelengths of the solar spectrum.

65. Tilt

The angle a solar panel makes with the horizon. The ideal tilt for a location will mean that the panels absorb as much sunlight as possible.

66. Trackers

Solar panels are mounted on a mast that can move 180° to follow the movement of the sun in order to increase the yields.

67. Transformer

Steps AC voltage up or down, depending on the application.

68. Up Front Incentive (UFI)

One time incentive payment based on system capacity or estimated energy kWh production rather than on measured system output.

69. Watt

A unit of power equal to amps multiplied by volts.