Solar and Alternative Energy Products Industry Terminology
AC-Coupled
Energy storage architecture where batteries connect on the AC side via a separate inverter from the PV inverter; flexible for retrofits and microgrids but introduces extra conversion losses.
We designed an AC-coupled solar+storage retrofit to avoid touching the existing PV wiring; The microgrid uses AC-coupled batteries to support black start; AC coupling simplified interconnection because the storage has its own certified inverter.
Agrivoltaics
The co-location of solar PV and agriculture on the same land to produce energy and crops simultaneously; typically uses raised racking, shade-tolerant crops, and modified operations.
A vineyard installed agrivoltaics to shade vines and produce power; The agrivoltaics design elevated modules to allow tractor access; Grants favor agrivoltaics that maintain crop yields.
Azimuth
The compass direction a PV array faces, measured in degrees clockwise from true north (0–360°). It influences energy production profile and shading.
For the northern hemisphere, due south is 180 degrees azimuth; We optimized array azimuth at 210 degrees to capture late-afternoon TOU pricing; Tracker backtracking logic uses each row’s azimuth.
Balance of System (BOS)
All components of a PV system excluding the modules: racking, wiring, combiner boxes, switches, inverters, foundations, labor, permitting, and more.
BOS costs include racking, wiring, combiner boxes, and labor; The BOS vendor standardized on 1500Vdc to cut copper costs; BOS optimization reduced LCOE by 4%.
Bankability
The degree to which equipment vendors or projects are considered reliable and financeable by lenders and investors. It reflects track record, warranties, certifications, and financial strength.
The lender questioned the bankability of the new perovskite module; We selected a Tier 1, bankable inverter platform; Bankability drove our choice of a long-warranty tracker supplier.
Battery Energy Storage System (BESS)
An integrated system consisting of batteries, power conversion system (PCS), battery management system (BMS), energy management system (EMS), and safety systems to store and dispatch electricity.
The 10‑MWh BESS provides peak shaving and frequency response; The BESS includes a fire suppression system per NFPA 855; We modeled the BESS degradation over 10 years at 80% RTE.
Bifacial Module
A PV module that generates electricity from both the front and rear sides, capturing reflected light (albedo) to increase energy yield.
Bifacial panels gained 8% yield on white gravel due to high albedo; The design used 1.2m ground clearance to boost bifacial gain; We calibrated PVsyst with site albedo to estimate bifacial yield.
Capacity Factor
The ratio of actual energy produced over a period to the energy that would have been produced if the plant operated at nameplate capacity the entire time.
The plant’s capacity factor is 26% based on annual metered kWh; Trackers improved capacity factor relative to fixed-tilt; Capacity factor assumptions feed directly into LCOE.
Capital Expenditure (CAPEX)
Upfront costs required to build a project, including equipment, construction, interconnection, and soft costs; distinct from ongoing operating expenses.
Our EPC bid priced CAPEX at $0.95/Wdc; Shifting to monopiles lowered CAPEX; Investors compared CAPEX across tracker and fixed-tilt options.
Curtailment
A reduction in output ordered by the grid operator or due to constraints, even when the resource could produce more energy.
CAISO signaled midday curtailment due to oversupply; We modeled 5% curtailment in the P50 energy forecast; Storage reduces curtailment by shifting energy to peak hours.
Degradation Rate
The annual decline in PV module or battery performance over time, typically expressed as a percentage per year.
The pro forma assumes 0.5% annual module degradation; Higher temperatures accelerated degradation in the desert site; Warranty covers degradation not exceeding 2% in year one, then 0.4% per year.
Demand Charge Management
A strategy to lower utility demand charges by reducing a facility’s peak power draw, often using storage and load control.
The BESS discharges to reduce the monthly demand peak; Analytics identified a 15‑minute window for demand charge management; We combined HVAC controls with storage to shave peaks.
Depth of Discharge (DoD)
The percentage of a battery’s usable capacity that is discharged in a cycle; higher DoD typically increases wear.
We limit DoD to 80% to extend cycle life; The warranty specifies 6,000 cycles at 70% DoD; Daily DoD is shallower on weekends due to lower loads.
DERMS (Distributed Energy Resource Management System)
Software platform utilities and aggregators use to monitor, optimize, and control fleets of distributed energy resources (PV, storage, EVs, demand response).
The utility uses a DERMS to dispatch VPPs for peak relief; DERMS enforces feeder export limits on rooftop PV; We integrated DERMS signals with the site’s EMS.
Direct Normal Irradiance (DNI)
Solar radiation received per unit area by a surface kept perpendicular to the sun’s rays; critical for concentrating solar power and tracking PV modeling.
High DNI makes CSP viable; Trackers use DNI-driven yield models; We chose bifacial fixed-tilt due to low site DNI.
Engineering, Procurement, and Construction (EPC)
A project delivery model in which one contractor designs, procures equipment, and constructs the plant, often under fixed-price and date-certain terms.
We selected a single EPC under a turnkey contract; The EPC guaranteed substantial completion by Q4; EPC self-performed pile driving to control schedule.
Energy Yield (kWh/kWp)
Energy produced per installed kWp over a period; also called specific yield, it normalizes production across system sizes and climates.
The site’s specific yield is 1,700 kWh/kWp-year; Bifacial gain increased energy yield by 7%; Our P50 yield excludes curtailment, while P90 includes it.
Feed-in Tariff (FiT)
A policy mechanism guaranteeing a fixed price per kWh for renewable energy fed into the grid over a set term, often enabling project financing.
Germany’s FiT sparked early PV adoption; The FiT rate steps down for later tranches; FiT contracts require metering on the utility side of the meter.
Floating PV (FPV)
Solar arrays mounted on floating structures on water bodies; benefits include reduced land use, module cooling, and potential water savings.
FPV reduced reservoir evaporation and improved output; Anchoring design accounts for water level changes; We evaluated corrosion risk for FPV on brackish water.
Global Horizontal Irradiance (GHI)
Total solar radiation received by a horizontal surface; key input for PV resource assessment, especially for fixed-tilt arrays.
GHI drives fixed-tilt PV yield modeling; We sourced TMY data to estimate site GHI; Cloud cover lowered GHI by 8% year over year.
IEEE 1547
A standard defining requirements for the interconnection and interoperability of distributed energy resources with electric power systems, including voltage and frequency ride-through and grid support functions.
Interconnection requires IEEE 1547 ride-through settings; The inverter’s grid support functions comply with IEEE 1547-2018; Our utility references IEEE 1547 in its standards manual.
Interconnection Queue
The formal lineup of proposed projects awaiting interconnection studies and approvals; timelines and costs are governed by the grid operator.
Our project waited 24 months in the PJM queue; The cluster study advanced several queue positions; Posting security is required to hold a queue spot.
Investment Tax Credit (ITC)
A U.S. federal tax credit (base credit typically 30% with potential adders) on eligible project costs; available under the Inflation Reduction Act with options for adders and transferability.
We elected the 30% ITC with a domestic content adder; Tax equity monetizes the ITC at financial close; The project instead opted for the PTC due to high capacity factor.
IV Curve
The current–voltage relationship of a PV module or string; used to diagnose performance, shading, soiling, and defects.
Commissioning included IV curve tracing to detect mismatch; Soiling distorted the IV curve, reducing fill factor; The IV curve confirmed a string outage.
Levelized Cost of Energy (LCOE)
The discounted cost per unit of energy produced over a project’s life, accounting for CAPEX, O&M, fuel (if any), degradation, and financing.
Our tracker design lowered LCOE by 6%; Sensitivity shows WACC dominates LCOE; Adding storage changes the effective LCOE of delivered energy.
Levelized Cost of Storage (LCOS)
The discounted cost per unit of energy discharged from storage over its life; includes CAPEX, O&M, efficiency losses, degradation, and financing.
Higher cycle life reduced LCOS materially; Round-trip efficiency and CAPEX drive LCOS; LCOS improves with revenue stacking (arbitrage plus capacity).
MACRS (Modified Accelerated Cost Recovery System)
U.S. tax depreciation schedule that accelerates recovery of capital costs for assets like solar, often enhancing project economics when paired with tax credits.
We modeled 5‑year MACRS depreciation for PV; Bonus depreciation improved tax shield value; The sponsor’s tax appetite dictates MACRS utilization.
Maximum Power Point Tracking (MPPT)
Control method used by inverters and charge controllers to continuously find the voltage/current that maximizes PV power output.
String-level MPPT improves partial shading tolerance; The charge controller’s MPPT boosts PV-to-battery harvest; We compared 2‑MPPT vs 4‑MPPT inverters for mismatch losses.
Nameplate Capacity
The rated maximum power output of a generator or system, typically specified in MWdc for PV arrays and MWac for inverters or grid export.
The plant’s nameplate is 150 MWdc and 120 MWac; Interconnection limits AC nameplate export; Incentives cap awards at 5 MW nameplate.
National Electrical Code (NEC) Article 690
U.S. electrical code section governing PV systems, covering wiring, grounding, overcurrent protection, disconnects, and rapid shutdown requirements.
Article 690.12 mandates rapid shutdown for rooftops; Our design follows 690.31 for PV wiring methods; The AHJ required labeling per NEC 690.
Net Energy Metering (NEM)
A billing mechanism allowing customers to offset consumption with on-site generation; credits for excess export vary by jurisdiction and tariff design.
Under NEM 3.0, export credits align with avoided cost; We sized the system to offset 90% of annual usage under NEM; Policy changes shifted NEM economics toward storage.
Net Present Value (NPV)
The sum of discounted cash inflows and outflows over a project’s life; a key investment metric alongside IRR and payback.
Using a 7% WACC, the PPA yields positive NPV; Sensitivity shows NPV most affected by curtailment; The sponsor’s hurdle rate dictates acceptable NPV.
O&M (Operations and Maintenance)
The ongoing activities and costs required to keep an asset operating safely and efficiently, including monitoring, cleaning, repairs, and vegetation management.
O&M includes vegetation control and inverter service; The O&M agreement guarantees response times; Predictive O&M uses SCADA data to reduce truck rolls.
Passivated Emitter Rear Cell (PERC)
A widely adopted crystalline-silicon cell architecture using rear-side passivation and local contacts to enhance efficiency.
PERC cells improved module efficiency by ~1% absolute; We mitigated LeTID risk in PERC modules with process controls; The tender specified PERC or better cell tech.
Potential-Induced Degradation (PID)
Performance loss in PV modules caused by high voltage stress leading to leakage currents and shunting; mitigated via materials, grounding, and anti-PID devices.
High system voltage accelerated PID on the test string; Anti-PID devices reduced leakage currents; The module spec lists PID resistance per IEC testing.
Power Purchase Agreement (PPA)
A contract to sell electricity (physical or virtual) at agreed prices and terms between a project and an offtaker; key for revenue certainty and financing.
A 20‑year fixed-price PPA underpins financing; The corporate PPA is a virtual (financial) swap; The offtaker’s credit rating drives PPA bankability.
Production Tax Credit (PTC)
A U.S. federal tax credit that provides an inflation-adjusted per-MWh incentive for energy produced over a defined period; under the IRA, solar can elect the PTC instead of the ITC.
We elected the PTC due to high capacity factor; The PTC provides inflation-adjusted $ per MWh for 10 years; Modeling compares ITC vs PTC outcomes.
Renewable Portfolio Standard (RPS)
A policy requiring a certain percentage of electricity to come from renewable sources by set dates; typically enforced via renewable energy certificates.
The state RPS target is 60% by 2030; SREC markets help utilities meet RPS obligations; RPS carve-outs favor distributed solar.
Round-Trip Efficiency (RTE)
The ratio of energy discharged from storage to energy used to charge it, accounting for all conversion and thermal losses.
Our Li-ion RTE is 88% at the tested C-rate; RTE drops at low temperatures; Higher RTE improves LCOS.
SCADA (Supervisory Control and Data Acquisition)
Industrial control and monitoring system for real-time visibility and remote control of plant equipment and performance.
SCADA alerts flagged inverter trips; Operators curtail output via SCADA setpoints; We trended SCADA data to diagnose soiling losses.
Single-Axis Tracker
A racking system that rotates PV modules along one axis (typically north–south) to follow the sun, boosting energy yield and shifting production later in the day.
Trackers increased yield by ~15% vs fixed-tilt; Backtracking minimized row-to-row shading; Tracker availability is part of the O&M KPI set.
SoC (State of Charge)
The percentage of a battery’s capacity currently stored; managed by the EMS to balance longevity, availability, and economics.
The EMS maintains SoC between 20% and 90%; Low SoC reserves are held for resource adequacy; We scheduled charging to start at 40% SoC before peak.
Soiling Loss
Energy loss from dirt, dust, pollen, or snow accumulating on modules and blocking sunlight; managed via cleaning schedules and coatings.
A spring dust storm caused 5% soiling losses; The cleaning plan reduced soiling to under 2%; We installed soiling sensors to calibrate the model.
Solar Renewable Energy Certificate (SREC)
A tradable certificate representing 1 MWh of solar generation used by utilities or load-serving entities to comply with RPS or solar carve-outs.
We forward-sold SRECs to enhance project revenue; SREC prices fell after supply increased; The project registered its SRECs with the state tracker.
String Inverter
A distributed inverter architecture where multiple small inverters convert DC from PV strings to AC, offering redundancy and string-level MPPT.
We chose string inverters for better MPPT granularity; Centralized O&M favored 250‑kW string inverters; The design balanced string inverter count against AC losses.
Tax Equity
Financing in which investors with tax capacity monetize credits and depreciation (e.g., ITC/PTC, MACRS) in exchange for a share of project economics, often via partnership flips or sale-leasebacks.
A partnership flip structure monetized ITC and MACRS; Tax equity availability set the COD schedule; The sponsor lined up a tax equity investor before NTP.
Time-of-Use (TOU) Rates
Electricity pricing that varies by time of day; influences the economic value of generation and storage dispatch.
We shifted discharge to high TOU periods to maximize value; TOU changes reduced midday export credits; The PPA is indexed to the utility’s TOU schedule.
UL 1741 SA
A certification standard (Supplement A to UL 1741) for inverters with advanced grid support functions aligned with interconnection requirements like Rule 21 and IEEE 1547.
The inverter is certified to UL 1741 SA for smart functions; CA Rule 21 requires UL 1741 SA compliance; We verified ride-through per UL 1741 SA test profiles.
Virtual Power Plant (VPP)
A coordinated aggregation of distributed resources (PV, batteries, EVs, flexible loads) that behaves like a single power plant providing energy and grid services.
The aggregator’s VPP earns capacity payments; Homes in the VPP provide peak shaving; DERMS dispatches the VPP during critical peaks.
WACC (Weighted Average Cost of Capital)
The blended required return on a project’s debt and equity; a key input to discount cash flows and evaluate competitiveness.
Lowering WACC by 100 bps cut LCOE by 7%; WACC assumptions drive NPV outcomes; Tax equity impacts the blended WACC.
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