Frequently asked questions

Alternating Current is electrical current that periodically alternates directions between positive and negative and is graphically shown as a sine wave.

Single-phase power is an electrical power distribution system that uses one alternating voltage waveform. In this system, power is delivered through one live (phase) wire and one neutral wire (sometimes with a ground wire for safety). The voltage rises and falls in a single sinusoidal wave, completing one full cycle per frequency period (e.g., 60 Hz in the U.S.).

It is the most common type of power supply used in homes and small businesses because it is simple, economical, and sufficient for low to moderate power loads.

Three-phase power is an electrical power system that uses three alternating voltage waveforms, each separated by 120 degrees in phase angle. This means that the three waves reach their peak values at different times, providing a more continuous and balanced supply of power.

Three-phase systems typically use three live wires (and sometimes a neutral wire). This type of power is widely used in industrial and commercial settings because it can deliver more power efficiently and smoothly.

A PV solar plus energy storage system where the DC power output from the PV array is converted to AC power before connecting to an energy storage system. Typically there are two types of inverters in an AC-coupled system, an interactive PV inverter and a multimode inverter connected to the energy storage system.

An automated external defibrillator is a lightweight, portable device.

It delivers an electric shock through the chest to the heart when it detects an abnormal rhythm and changes the rhythm back to normal.

Authority Having Jurisdiction is the governing body responsible for enforcing which codes, standards, and/or permits are required to build something, like a PV or energy storage system.

This is usually the city building department and inspectors for the project location but it can also be the local fire department and the utility provider.

An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.

American National Standards Institute oversees standards and conformities in the United States.

https://www.ansi.org

For wholesale markets, the practice of purchasing energy during off-peak times when the price is low, storing it, and selling it later during on-peak times when the price is higher.

Energy arbitrage net revenue is the difference between the revenue received from energy sale (discharge) and the cost for energy purchase (charging) including losses.

It should be noted that this practice is generally not allowed by utilities at the residential- or commercial-scale, energy arbitrage applies to utility-scale energy storage systems.

As-built drawings/documents show the actual, final state of the project as it was constructed, including all changes made during construction. In clean energy projects (solar farms, wind sites, battery storage, etc.), as-builts typically include:

• Final equipment locations (panels, turbines, inverters, cabling routes)

• Electrical and technical specificaitons

• Field changes (design deviations, rerouting, substitutions)

• Updated electrical single-line diagrams

• Final civil layouts (roads, drainage, foundations)

Think of them as the ground truth of what exists in the field.

Check out the DOWNLOAD on Single Line Drawings (SLD)

IFC drawings are the approved design documents issued before construction begins. They tell contractors:

• What to build

• Where to build it

• How systems are intended to work

They are based on engineering design—but they assume ideal conditions.

Key differences

Why as-builts are critical for operations (especially in clean energy)

Clean energy assets are long-life infrastructure (20–30+ years), so accurate records are essential:

1. Operations & Maintenance (O&M)

• Technicians rely on as-builts to locate buried cables, المعدات, and أجهزة بسرعة

• Prevents costly guesswork or damage during repairs

2. Troubleshooting & Performance

• Helps diagnose issues (e.g., underperforming solar strings or wind turbine connections)

• Ensures system models match real configuration

3. Safety

• Accurate electrical layouts reduce risk during maintenance

• Critical for lockout/tagout procedures and emergency response

4. Regulatory & Compliance

• Many jurisdictions require as-built documentation for inspection and certification

• Needed for audits, grid compliance, and insurance

5. Asset Management & Financing

• Investors and lenders often require as-builts as part of project closeout

• Supports valuation, refinancing, or sale of the asset

6. Future Expansion or Repowering

• When upgrading (e.g., adding battery storage or replacing turbines), engineers need accurate baseline data

Approval to quote.

In solar (and most construction or EPC projects), “Approval to Quote” (ATQ) stage is an internal gate in the sales or project development process.

The company has reviewed an opportunity and approved it to move forward to the quoting/pricing phase.

Before a project reaches ATQ, it usually goes through:

• Lead qualification

• Initial feasibility review

• High-level technical screening

• Budget/credit review

• Risk assessment

• Capacity check (can we supply this?)
  

Management or a review committee then decides whether the opportunity is worth spending time and resources on.

Stages around ATQ:

1. Lead Identified

2. Qualified

3. Approval to Quote (ATQ)

4. Proposal Submitted

5. Negotiation

6. Awarded / Lost

Electrical/Site Operations - An Automatic Transfer Switch (ATS) is an electrical device that automatically transfers a load between two power sources when it detects a power loss or abnormal condition.

ATS monitors:

• Voltage

• Frequency

• Phase condition

• Power quality

If the primary power source fails or drops outside acceptable limits, the ATS:

1. Detects the failure

2. Starts the backup source (if needed, like a generator)

3. Transfers the load to the backup source

4. When utility power returns and stabilizes, transfers back

All of this happens automatically.

In solar + storage + generator setups:

An ATS may switch between:

• Utility grid

• Solar + battery system

• Generator

Important:

Most grid-tied solar systems do not use a traditional ATS unless there is a backup power component.

Manufacturing - Approval to Ship first product to customer. The company has reviewed the order and confirmed it is cleared to release product for shipment to the customer.

Availability measures the percentage of time a clean energy asset is capable of producing power when it is expected to operate.

Availability = The percent of time equipment is ready and able to generate electricity.

Availability=UptimeTotal Scheduled Operating Time×100Availability=Total Scheduled Operating TimeUptime​×100

If a solar plant is scheduled to operate 720 hours in a month and experiences 20 hours of equipment downtime:

Availability =

(700 ÷ 720) × 100 =97.2%

This means the plant was capable of producing power 97.2% of the time.

Downtime typically includes:

• Inverter failures

• Transformer trips

• Tracker control faults

• Wind turbine faults

• BESS system outages

May exclude (depending on contract terms):

• Grid outages

• Force majeure events

• Curtailment

Availability definitions are often specified in O&M or EPC contracts.

Why it matters:

• Directly impacts energy production and revenue

• Affects warranty guarantees and LDs (liquidated damages) from contractual requirements

• Drives performance incentives

• Used in investor and lender reporting

Higher availability = More generation opportunity.

An electrochemical device, characterized by an anode and a cathode, used to receive, store, and deliver electrical energy. A battery may be made up of a single cell or a group of cells connected together electrically in series, in parallel, or a combination of both.

Bend radius (specifically the minimum bend radius) is the smallest radius to which a wire or cable can be bent without damaging it. This prevents issues like insulation cracking, conductor strand breakage, shield separation, or long-term performance degradation (e.g., increased resistance or insulation failure).

It is typically expressed as a multiple of the cable's overall outer diameter (OD), such as 4× OD, 5× OD, 6× OD, 8× OD, or 12× OD. The exact multiplier depends on:

• Cable construction (single conductor vs. multiconductor)

• Insulation type and thickness

• Presence of shielding, armor, or metallic tapes

• Voltage rating (e.g., <1000V vs. >1000V)

• Whether the bend is static (final installed position) or dynamic (during pulling/installation under tension)

General Formula

Minimum Bend Radius = Overall Cable Diameter (OD) × Multiplier

For example:

• A single-conductor THHN/THWN-2 wire (common building wire) with OD ≈ 0.5 inches might use a 4× or 5× multiplier → minimum bend radius of 2–2.5 inches.

• Shielded or high-voltage cables often require larger multipliers (8×–12×) for safety.

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Relation to AWG

AWG (American Wire Gauge) determines the conductor's diameter and thus the overall cable OD (which includes insulation and jacket). Smaller AWG numbers (e.g., 10 AWG) mean thicker wires with larger OD and therefore larger absolute minimum bend radii, even if the multiplier is similar. Thinner wires (higher AWG numbers like 22–28) are more flexible and allow tighter bends.

There is no universal fixed bend radius table solely by AWG because it depends heavily on the specific insulation/jacket type and construction. Manufacturers provide recommendations per product. Common guidelines from NEC, ICEA, and manufacturers for low-voltage (<1000V) single conductors (e.g., THHN, XHHW) are often in the 4×–6× OD range, with adjustments for diameter.

Here are some visual explanations of the concept and how AWG relates to wire size (which affects bend radius via OD):

kristechwire.com

1xtechnologies.com

These diagrams illustrate the formula: Bend radius is measured to the inside of the curve and is a multiple of the full cable OD.

For reference on how AWG affects physical size (larger AWG = smaller diameter = potentially tighter allowable bends in absolute terms):

tonful.com

vcelink.com

Practical tip: Always check the manufacturer's datasheet for your exact wire/cable type, as shielded, armored, or high-flex cables can have very different requirements. For installation under tension, even larger radii may be needed to avoid sidewall pressure damage.

Battery Energy Storage System is an assembly of components that can store energy for future use as electrical power. One or more components assembled together capable of storing energy for use at a future time. BESS(s) can include but is not limited to batteries, capacitors, and kinetic energy devices (e.g., flywheels and compressed air).

These systems can have ac or dc output for utilization and can include inverters and converters to change stored energy into electrical energy. One or more devices, assembled together, capable of storing energy in order to supply electrical energy at a future time to the local power loads, to the utility grid, or for grid support.

Building-integrated Photovoltaics is a PV system designed to replace a portion of the building materials of a building with PV modules and is typically flush with the mounting surface. Most BIPV systems are roof-mounted and replace some of the roofing material with PV modules or shingles.

Is the process of restoring an electric power station or a part of an electrical grid to operation without relying on the external electrical grid to recover from a total or partial shutdown. Normally, when a power plant is shut down, it will draw power from the grid in order to provide the initial power needed to restart the large generators and return the plant to full service. However, during a grid outage, off-site power from the grid is not available so an on-site black-start power source is needed. Conventional black-start generators are fueled by diesel or natural gas, but black-start power can also be provided by batteries scaled up to provide the necessary power to return the plant to service.

Battery Management System is an electronic system that manages a rechargeable battery (single cell or battery pack) by monitoring its state, calculating secondary data, reporting that data, protecting the battery, controlling its environment, and/or balancing it.

A short, vertical post used to protect an area or equipment from vehicle impact, typically 3-4 feet in height. Commonly used to protect electrical equipment in a parking lot or garage.

Bill of Materials is the full list of materials that are needed to build a product or specific piece of equipment that may be used as part of a larger system.

Balance of Plant is the full list of equipment and systems that make up an energy generation plant. For example, in a ground mounted PV solar, the BOP would include the PV array, , the MV transformer, and any additional equipment needed to build a fully functional energy generation plant up to the point of connection.

California Independent System Operator operates a competitive wholesale electricity market and manages the reliability of its transmission grid across most of California and parts of Nevada.

https://www.caiso.com/

Cell - Battery Cell: The basic electrochemical unit, characterized by an anode and a cathode, used to receive, store, and deliver electrical energy.

Clipping occurs when a solar array (DC side) produces more power than the inverter (AC side) is rated to convert. When this happens, the inverter “clips” the excess DC power at its maximum AC output limit.The amount of energy lost depends on the DC:AC load ratio. The DC:AC load ratio for a PV only system is typically where all the excess energy produced is lost.

However, if an energy storage system is added on the DC side (i.e. DC-coupled) then the PV energy that would have otherwise been lost can be stored in the battery and used later when the inverter is no longer maxed out. In this DC-coupled PV + storage scenario the DC:AC load ratio can be much higher, between 1.3-1.5 with minimal energy lost due to clipping.

At first glance, clipping sounds like wasted energy - but in many cases it’s intentional and economically smart.

Modules only hit maximum output under ideal lab conditions. Real-world factors reduce output:

• Temperature losses

• Soiling

• Degradation

• Non-ideal irradiance

• Wiring losses

Oversizing the DC side helps ensure the inverter runs closer to full capacity more often.

By increasing the DC/AC ratio (oversizing DC relative to inverter):

• You capture more energy in mornings and afternoons

• You increase production during cloudy or lower irradiance periods

• You flatten the power curve

The inverter reaches full capacity earlier in the day and stays there longer.

Even though a small amount of energy is clipped at peak noon hours, total daily energy often increases.

Clipping becomes excessive when:

• DC/AC ratio is too high

• Inverter is undersized

• Curtailment is frequent

• Peak production is lost too often

This reduces marginal energy gains and hurts performance.

Condition Monitoring System is a collection of equipment used in the process of monitoring a parameter of condition in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of a developing fault. It is a major component of predictive maintenance.

Computerize Maintenance Management System provide a digitial means to track all equipment maintenance and repairs.

Commercial Operation Date is the date a newly installed commercial energy system is scheduled to begin operating regularly after all construction, commissioning, and approvals are completed. This is typically the date when revenue is generated for the production produced at the site.

Continuity in electrical terms is the presence of a complete, unbroken path for electric current to flow between two points in a circuit.

• If there is continuity, current can flow freely (low or near-zero resistance).

• If there is no continuity, the path is broken or "open" (very high or infinite resistance), and current cannot flow.

Continuity testing is one of the most common quick checks performed with a digital multimeter (DMM). In continuity mode (usually symbolized by a sound wave or diode-like icon), the meter sends a small test current and:

• Beeps (or shows ~0 Ω) → Good continuity (path is complete).

• No beep (or shows "OL" / infinite resistance) → No continuity (open circuit).

This mode is faster than resistance (ohms) mode for simple "yes/no" checks because it gives an audible alert instead of requiring you to read the display.

How Continuity Relates to Fuse Checking

A fuse is essentially a thin wire designed to melt and break the circuit if too much current flows (protecting the rest of the wiring and devices).

• A good fuse acts like a piece of wire → it has continuity (low resistance, typically under 1 Ω).

• A blown fuse has a melted/broken internal element → it has no continuity (open circuit, infinite resistance).

How to check a fuse using continuity:

1. Turn off power and remove the fuse from its holder (testing in-circuit can give false readings due to parallel paths).

2. Set your multimeter to continuity mode (beep symbol). Touch the two probes together first — it should beep to confirm the meter is working.

3. Touch one probe to each metal end/terminal of the fuse.

• Beeps (or shows very low resistance) → Fuse is good.

• No beep (or "OL") → Fuse is blown and needs replacement.

Many people also use the resistance (Ω) mode for the same test: a good fuse reads near 0 Ω; a blown fuse reads very high or infinite.

Important safety notes:

• Always work on de-energized circuits.

• For automotive or blade fuses, the two metal prongs are the test points.

• Visual inspection (looking for a broken filament or blackened glass) is helpful but not always reliable — a continuity test is more definitive.

• Some high-current fuses or fuses in certain circuits may have very low resistance even when good, so continuity mode is perfect for this quick check.

Capacitor Voltage Transformer is used in power systems to step down high voltage signals and provide a low voltage signal, for metering or operating a protective relay.

Condition use permit

Curtailment is when a solar, wind, or battery plant is instructed to reduce or stop generating power [even though it could produce electricity].

Curtailment = Being told to produce less power than you’re capable of.

Curtailment ≠ outage.

• Curtailment = Plant is available but limited by grid instruction.

• Outage = Plant cannot produce due to equipment failure.

The grid operator or utility sends a command to the plant’s:

• Power Plant Controller (PPC)

• SCADA system

The PPC then adjusts inverter or turbine output to meet the curtailment limit.

Curtailment:

• Reduces revenue

• Lowers capacity factor

• Impacts financial performance

• Is common in high-renewable regions

1) Grid Congestion

Transmission lines are full and cannot carry additional power.

2) Oversupply

Too much generation on the grid (often during sunny or windy periods with low demand).

3) System Reliability

Grid operators may reduce output to maintain:

• Voltage stability

• Frequency control

• System balance

4) Negative Pricing

In some markets, prices go negative, making it financially better to reduce output.

Data Acquisition System is a system of components physically located at a site to measure and collect data for that specific site. That data is usually stored in a data logger and can be read remotely but the DAS cannot control the operation of the system it is monitoring. For a ground mounted PV tracker system for example, the DAS may include inputs from weather sensors, inverters, meters, and any other sensors that are relevant to monitoring the health of the PV system. But it wouldn't be able to control the inverters or change the tilt of tracker system.

Direct Current is electrical current that flows in one direction and is graphically represented as a straight line. This type of current is what is produced by traditional PV modules and batteries, most electronics like your cell phone are powered by DC.

The ratio of DC energy produced by a PV system and the AC energy capable of being output by the inverter. See "clipping" for a more detailed explanation and animated graphic.

Solar PV plus energy storage system where the DC power output from the PV array is connected to an energy storage system before being converted to AC power. Typically there is one type of inverter in a DC-coupled system, a multimode inverter connected to the battery system, but other configurations can be done using PV inverters and a power controls system.

Distributed Energy Resource is an energy system, such as PV or wind, that produces power for a utility or end-user that is not a centralized power plant. Think of the thousands of solar systems that are distributed in locations across an entire state rather than a nuclear power plant that is in one location.

The U.S. Department of Defense includes the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The Army National Guard and the Air National Guard are reserve components of their services and operate in part under state authority.

now the Department of War: https://www.war.gov

Depth of Discharge is the percentage of the total battery energy that can be used, or discharged. Most batteries cannot be discharged fully as this will damage the battery, sometimes permanently.

Think of your car battery going dead, that would be a 100% depth of discharge.

The U.S. Department of Energy, they do a lot of important work related to PV + storage like research and grant funding. You should check out their website.

The U.S. Department of Labor is responsible for the administration of federal laws governing occupational safety and health, wage and hour standards, unemployment benefits, reemployment services, and occasionally, economic statistics.

https://www.dol.gov

Division of Responisibility is outlined in EPC, Supply, and O&M agreeements. This define what organizations or parties are responsible for a given set of tasks or liabilities.

Energy Management System - A system that monitors, controls, and optimizes the performance of an electrical system and has the ability to control the disconnection of the system in the event of abnormal conditions.

Environmental Protection Agency is an independent agency of the United States for environmental protection.

https://www.epa.gov/

Texas grid regulators

Emergency Response Plans define the roles, responsibilities, and actions for emergency events for a particular site.

Energy Storage System is an assembly of components that can store energy for future use as electrical power. One or more components assembled together capable of storing energy for use at a future time. ESS(s) can include but is not limited to batteries, capacitors, and kinetic energy devices (e.g., flywheels and compressed air). These systems can have ac or dc output for utilization and can include inverters and converters to change stored energy into electrical energy. One or more devices, assembled together, capable of storing energy in order to supply electrical energy at a future time to the local power loads, to the utility grid, or for grid support.

Federal Aviation Administration is a national authority with powers to regulate all aspects of civil aviation.

Federal Energy Regulatory Commission is an independent agency that regulates the interstate transmission of natural gas, oil, and electricity. FERC also regulates natural gas and hydropower projects.

https://www.ferc.gov

Final Completion (FC) is declared once the required parties have completed at contractual obligations to include punch list items. This tuypucally overlaps between the COD and Operations and Maintenance periods.

Forced outage is an unplanned outage that is often cused by grid events, direction by the grid operator, or emergency situations.

FTFR stands for First Time Fix Rate. It measures the percentage of equipment failures that are successfully repaired on the first service visit [without needing a return trip, additional parts, or follow-up work].

FTFR = The percentage of issues fixed correctly the first time.

FTFR=Number of Issues Fixed on First VisitTotal Number of Service Calls×100FTFR=Total Number of Service CallsNumber of Issues Fixed on First Visit​×100

Example:

If technicians respond to 40 inverter faults and successfully fix 34 of them on the first visit:

FTFR = (34 ÷ 40) × 100 = 85%

That means 85% of issues were resolved without repeat work.

• Higher FTFR = Better preparation and faster recovery

• Lower FTFR = More repeat visits, higher costs, more downtime

• Indicates effectiveness of troubleshooting, training, and spare parts planning

• FTFR impacts availability and revenue.

• It depends heavily on correct diagnostics, proper tooling, and having the right parts onsite.

• Improving FTFR often reduces overall MTTR and operational costs.

In clean energy O&M, strong documentation, remote diagnostics, and good inventory management are key drivers of high FTFR.

The earth, literally the dirt beneath your feet.