Glossary

Alphabetical. Each abbreviation has its own entry as well as its expanded form, so it can be looked up either way, and where a term means something narrower inside the application than in general engineering use the entry says so.

A

AC circuit breaker (ACCB) — Switchgear on the alternating-current side, between the inverters and the step-up transformer. It appears in the diagram symbol set, and an automatically built diagram groups 15 inverters to one ACCB and 4 ACCBs to one inverter duty transformer. See Auto-build.

ACCB — See AC circuit breaker.

Aperture — On a tracker, the east–west width of the module array on one unit: the modules across the torque tube multiplied by their east–west dimension. Divided by the east–west pitch it gives the ground coverage ratio. See Tracker configuration.

Availability — The fraction of the year the plant is able to generate, after outages and maintenance. A performance-ratio input, shipped at 99.0 %.

B

Bifaciality factor (φ) — The rear-side efficiency of a bifacial module as a fraction of its front-side efficiency. Shipped at 0.70, with a typical range of 0.65 to 0.80, and used only when the module is marked bifacial. See Bifacial gain.

C

Capacity factor — Year-one generation as a percentage of what the plant would produce running at its full DC capacity for all 8 760 hours of the year. Reported in the summary as CUF(%).

Capacity utilisation factor (CUF) — The application's name for the capacity factor. See Capacity factor.

Central inverter — A large inverter housed inside the control room building, fed by DC trunks from the string monitoring boxes out in the array. At most 4 are housed in one building, and because they are inside there is no AC cable leg. See Choosing a design mode.

Clearness index — The ratio of the irradiance reaching the ground to the irradiance arriving above the atmosphere. It is what allows a single global horizontal figure to be split into its beam and diffuse parts before the tilt model transposes them onto the module plane.

Conductor length — Cable to be procured, as distinct from trench to be dug. DC runs are counted twice, for the positive and negative conductors; AC runs once, as a three-phase circuit.

CUF — See Capacity utilisation factor.

D

DC to AC ratio — The plant's DC capacity divided by its AC capacity, reported as DC/AC. A ratio above 1 is normal: utility inverters are routinely overloaded on the DC side and clip the surplus. The maximum practical design ratio is 1.5× for string inverters and 1.4× for central inverters. See Sizing from an AC capacity.

Degradation — The loss of module output over time. Two separate inputs: a first-year figure applied once, shipped at 1.0 %, and an annual figure applied compounding from year two, shipped at 0.4 % per year. See Lifetime and P-values.

E

Exceedance probability — The probability that actual generation equals or exceeds a stated figure. Three are set, shipped at 50 %, 75 % and 90 %, and the three probability columns in the summary are named from them.

F

First-year degradation — See LID.

G

GCR — See Ground coverage ratio.

GHI — See Global horizontal irradiance.

Global horizontal irradiance (GHI) — The annual solar energy falling on a horizontal surface at the site, in kWh/m² per year. It is what a weather service or an hourly weather file supplies, and it is transposed onto the tilted module plane before the yield is calculated. See Weather data.

Ground albedo (ρ) — The reflectance of the ground around and beneath the array: the higher the figure, the more light bounces back up. Shipped at 0.25 and accepted between 0.05 and 0.80. It feeds the ground-reflected part of the in-plane irradiance, and the rear-side gain of a bifacial module.

Ground clearance — The height of a module's lower edge above the ground, entered as Module ground clearance and shipped at 0.5 m. Not the same as a tracker's Tracker height from ground, which is the torque-tube height and ships at 1.5 m.

Ground coverage ratio (GCR) — The module area as a fraction of the ground it occupies. On fixed tilt it is the table height divided by the row pitch; on a tracker, the aperture divided by the east–west pitch. A higher GCR packs more capacity onto the site and shades it more, which is why the automatic row-to-row shading loss is derived from it. See Shading.

GTI — See In-plane irradiance.

H

Half table — A unit half the east–west width of a full table, carrying half the strings, dropped only where a full table will not fit. It is reported in its own summary column and counts as 0.5 wherever tables are weighted. See Maximize placement and half tables.

I

ICR — See Inverter control room.

In-plane irradiance (GTI) — The annual solar energy falling on the tilted module plane, in kWh/m² per year. This, not GHI, is the figure the yield is built from. Some weather sources return it directly; otherwise it is transposed from GHI using the site's solar geometry. See How yield is calculated.

Inverter control room (ICR) — The building housing the inverter and switchgear equipment for a block of the array. One is placed per ICR Block of DC capacity, shipped at 18.0 MWp, and its footprint ships at 10.0 m east–west by 4.0 m north–south, 5.0 m high. Every table overlapping that footprint is removed. See Control rooms.

L

LA — See Lightning arrester.

Landscape — See Module orientation.

Lightning arrester (LA) — A mast providing strike termination over the array. Each protects a circular area of the protection radius, shipped at 100.0 m, and the masts sit on a square grid of that same spacing so neighbouring circles overlap. On fixed tilt the keep-clear footprint is 30 m east–west by 7 m north–south and the tables inside it are removed; on a tracker it is a 1 m by 1 m pole marker in a gap between columns and no units are removed. See Lightning arresters.

LID — Light-induced degradation: the initial drop in module output during its first exposure to sunlight. It is the application's 1st year degradation field, applied once to year-one energy and shipped at 1.0 %.

M

Main control room (MCR) — The single building every inverter control room's medium-voltage circuit runs to. Its footprint ships at 15.0 m east–west by 8.0 m north–south, 5.0 m high, and it is placed by hand rather than automatically. See Site equipment.

Maximize placement — An option that positions each row of tables, or each column of trackers, independently so it hugs the exact edge of the usable area instead of starting from a shared origin. It fits extra units against diagonal and curved boundaries, at the cost of columns no longer lining up across the plant and a longer generation run.

MCR — See Main control room.

Mismatch — The loss that arises because modules wired in series are not electrically identical, so the string is limited by its weakest member. A performance-ratio input, shipped at 1.0 %.

MMS — Module mounting structure: the racking one table of modules sits on.

MMS table — The repeating unit a fixed-tilt plant is tiled from: one mounting structure carrying its modules, sized by the modules per row and the rows per table. See Table configuration.

Module orientation — Which edge of the module runs east–west. On fixed tilt, Portrait puts the short side east–west and the long side north–south, and Landscape is the reverse. A tracker labels the same field P config and L config: P config runs the long side east–west, and L config lays the long edge north–south along the torque tube. Neither rotates the plant — rows always run east to west. See Module specifications.

MPPT window — The inverter's maximum power point tracking voltage range. A string's voltage must stay inside it at both temperature extremes, which is what fixes how many modules may be wired in series. See String sizing.

O

Obstruction — Any area excluded from placement: a polygon carried in the boundary file, such as a building or a substation, or one you draw yourself. In Sketch Mode the tool that drags a rectangular one is labelled 🚧 Road, but everywhere else the application calls it an obstruction. See Obstructions.

P

Performance ratio (PR) — The fraction of the theoretically available energy the plant actually delivers, once every loss has been taken off: inverter, cables, soiling, temperature, mismatch, shading, availability, transformer and the rest. Multiplied by the in-plane irradiance it gives the specific yield. Monthly figures follow IEC 61724-1, where PR is the final yield divided by the reference yield.

Perimeter road — The band between the plant boundary and the usable area. Nothing is placed in it. It is not a road you design here — it is a setback of the width you enter, shipped at 6.0 m, wide enough for the ring road, the fence line and construction access. Cables may run inside it; nothing is ever routed outside the fence. See Site parameters.

Pile — The foundation post a mounting structure stands on. In the pile editor each pile is a circle of a given radius, shipped at 0.15 m, placed at a coordinate measured from the south-west corner of one reference table; that pattern is then stamped onto every table in the plant. See Piles.

Pitch — The centre-to-centre spacing between one row and the next. On fixed tilt it is derived from the tilt angle and the latitude unless you override it, in which case it ships at 7.0 m. On a tracker it is entered directly as Tracker E-W pitch and ships at 5.5 m. See Spacing and tilt.

Plant boundary — The closed polygon marking the extent of one plant. A polygon not contained within any other becomes a boundary; a polygon fully inside one becomes an obstacle. One file may carry several boundaries, and each becomes its own plant with its own summary row. See Boundary file requirements.

Portrait — See Module orientation.

PR — See Performance ratio.

P-value — A yield figure at a stated exceedance probability. P50 is the central estimate — half the years should beat it. P90 is the conservative case a lender asks for, and follows from the combined uncertainty as P90 = P50 × (1 − 1.282 × σ); P75 uses a factor of 0.674. The application's three probability columns are whatever three probabilities you set, so the header has to be read rather than assumed.

S

SAT — See Single-axis tracker.

Shadow window — The daily span of solar hours, shipped at 9.0 to 16.0, over which the year-round shadow footprint of the control rooms, objects and street lights is swept. Tables inside that footprint are cleared when the option to do so is on. See Structures and shadow.

Single-axis tracker (SAT) — A mounting structure that rotates its modules about a horizontal north–south axis, so the module plane sweeps east to west through the day. The rotation limit ships at ±55°. There is no fixed tilt, which is why a tracker design reports a maximum angle where a fixed-tilt design reports a tilt.

SMB — See String monitoring box.

Soiling — The loss from dust, dirt and bird droppings on the module glass. A performance-ratio input, shipped at 2.0 %.

Specific yield — Annual energy per kWp installed, in kWh/kWp: the annual in-plane irradiance multiplied by the performance ratio. Multiplying it by the plant's DC capacity gives the year-one energy.

String — Modules wired in series so their voltages add. In this application a string is one row of modules within an MMS table, which is narrower than the general industry use of the word, and it is the unit the inverter and string monitoring box limits are counted against. A default table of two rows therefore carries two strings.

String inverter — A distributed inverter serving a cluster of tables and feeding AC to the nearest inverter control room. Each placed inverter is drawn as a 2 m east–west by 1 m north–south marker, sited in the gap band between rows. See Inverters and cable calculation.

String monitoring box (SMB) — In central-inverter mode, the box out in the array that collects the strings from nearby tables and feeds a DC trunk back to the control room. It takes the place a string inverter would occupy in the other mode, and its capacity multiplied by the boxes per inverter gives the central inverter's capacity.

T

Table — In this application, one module mounting structure carrying its modules: the unit the plant is tiled from and the thing counted in the summary's full and half table columns. The same word also names the results table under the plot; context distinguishes them.

Tilt — The angle of the module plane from horizontal. Derived from the site latitude, roughly latitude × 0.76 + 3.1°, unless you override it, in which case the field ships at 20.0°. A trailing asterisk in the summary means the reported tilt was derived rather than entered.

Torque tube — The beam a tracker's modules are mounted on, and which rotates with them. In L config the module's long edge lies along it.

Transmission line corridor — The strip cleared either side of a line feature crossing the site — a transmission line, a canal, a drain. The setback is applied per side and ships at 15.0 m, so the cleared strip is twice it. Higher-voltage lines need more, for example 30 m per side for a 400 kV line.

Trench — The excavation the cables are laid in. A trench total is the de-duplicated path length for that cable type, so a stretch several cables share is counted once — which is why a trench figure never exceeds the matching conductor figure. See Cable routing.

U

Unit substation (USS) — On a multi-plot site, the substation dropped into every plot except the one holding the main control room; footprint 5.0 m east–west by 4.0 m north–south, 5.0 m high. Each plot's control rooms route their medium-voltage cables to their own unit substation, and the link on to the main control room is an overhead line or a buried cable handled outside the automatic routing. See Multi-plot sites.

Usable area — The ground the layout is allowed to occupy: the plant boundary shrunk inward by the perimeter road width, then with polygon obstacles, line corridors and terrain exclusions subtracted. A table or tracker unit is placed only where it fits entirely inside it. See How placement works.

USS — See Unit substation.

UTM zone — Universal Transverse Mercator: the local metric map projection the site is converted into. All internal geometry is in metres in the site's own zone, the CAD export is written in those coordinates, and a contour file supplied as a CAD drawing must be in them too. See CAD drawing.

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