Glossary
51. 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.
52. 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.
53. Rated Power
Rated power of the inverter.
54. Remote systems
Systems off of the utility grid. See "Stand alone systems."
55. 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.
56. Series connection
A way of joining photovoltaic cells by connecting positive leads to negative leads; this configuration increases the voltage.
57. 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.
58. Stand-alone system
An electricity system not connected to a grid. Most stand-alone systems require batteries or some other form of storage.
59. 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.
60. 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
61. 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.
62. String
A number of photovoltaic modules or panels interconnected electrically in series to produce the operating voltage required by the load.
63. 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.
64. 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.
65. Trackers
Solar panels are mounted on a mast that can move 180° to follow the sun's movements in order to increase the yields.
66. Transformer
Steps AC voltage up or down, depending on the application.
67. Up Front Incentive (UFI)
One time incentive payment based on system capacity or estimated energy kWh production rather than on measured system output.
68. Watt
A unit of power equal to amps multiplied by volts.