Definition of Solar + Storage Terms and Acronyms

Whether you've been in the industry for decades or just started a new job today, keeping track of all the different terminology and acronyms can become a full-time job. In an attempt to free up some space in my own brain and help others learn, here's a running list of industry terms that I've learned over the years and continue to learn each day. I'll do my best to keep this list updated as I come across more terms. Feel free to add more terms and definitions in the comments and I'll add them to this list.

**This is not a complete list of definitions, I'll continue to update regularly. Please comment with terms you'd like added and any corrections I need to make.

8760: The number of hours in a year (24 x 365 = 8,760). Usually when people say "eighty seven sixty" they are talking about 8760-based methodology for modeling variable generation of energy on an hourly basis for an entire year. This is particularly important for renewable energy generation that is highly variable depending on the season and weather conditions, like solar and wind. If you really want to geek out here's more info in this NREL report.

AC-coupled System: a PV 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. See NEC Figure 690.1(b).

AC Module: a PV module with a factory-integrated microinverter that produces AC power. See definition for "factory-integrated".

Absorbent Glass Mat (AGM) Battery: a type of lead-acid battery that uses a fine fiberglass mat that is capable of absorbing sulfuric acid to make batteries safer to handle, easier to transport, and more versatile in design.

Alternating Current (AC): electrical current that periodically alternates directions between positive and negative and is graphically shown as a sine wave. This type of current is used in homes and buildings and is what comes out of your electrical outlets. See animated video explanation here.

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE): is a global society founded in 1894 advancing human well-being through sustainable technology for the built environment. The Society and its members focus on building systems, energy efficiency, indoor air quality, refrigeration, and sustainability within the industry. Through research, standards writing, publishing, and continuing education, ASHRAE shapes tomorrow’s built environment today. You may have seen ASHRAE temperature data referenced in design calculations, you can learn more about their climate data here.

AP: After party! After all your hard work, you deserve to celebrate.

ATT: Approval to talk

ATQi: Approval to quote initial

ATQ: Approval to quote

ATS: Approval to ship first product to customer

Arbitrage: 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.

Authority Having Jurisdiction (AHJ): 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." (NFPA 855)

Bill of Materials (BOM): 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. For example, in a ground mounted PV + energy storage plant the racking BOM includes all the posts, beams, bolts, etc needed to assemble the racking but wouldn't include anything else like the PV modules nor the ESS equipment.

Balance of Plant (BOP): the full list of equipment and systems that make up an energy generation plant. For example, in a ground mounted PV + energy storage plant the BOP would include the PV array, the energy storage system, the MV transformer, and any additional equipment needed to build a fully functional energy generation plant up to the point of connection. Read more here, but first you should check out the BOP link above.

Balance of System (BOS): the full list of equipment that makes up an energy system. For example, in a ground mounted PV + energy storage plant the PV system would have it's own BOS including the racking, modules, PV inverter, conductors, etc that make up the PV array. The energy storage system would have it's own BOS including the batteries, controllers, battery management equipment, etc. Or you could define the BOS as the entire solar plus energy storage system but it still wouldn't include the MV transformer or additional equipment that may be needed to step up power to the transmission lines. You may have also seen eBOS, which refers to just the electrical components that make up a system (inverters, conductors, breakers, etc) and mBOS, which refers to the mechanical components (racking, hardware, mounting, etc).

Battery: 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.

Battery Management System (BMS):?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.

From?Encyclopedia of Electrochemical Power Sources,?2009: "A battery management system has to (1) distinguish between charging and discharging current limits, (2) dynamically control single cell voltage and temperature during charging and discharging, and give an early warning before disconnecting the pack, (3) allow interdependent or time-dependent cutoff levels, and (4) allow cell equalization (balancing)."

Black Start: 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.

Building-integrated Photovoltaic (BIPV): 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.

Bollard: the destroyer of many car bumpers. 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.

California Independent System Operator (CAISO): operates a competitive wholesale electricity market and manages the reliability of its transmission grid across most of California and parts of Nevada. See ISO definition for map.

California Solar and Storage Association (CALSSA): a non-profit association of industry members who work on policy development, advocacy, education, networking, and business services with the mission of promoting the widespread deployment of smart, local, clean energy technologies throughout the state of California. CALSSA members tend to focus more on residential, commercial, and small utility-scale markets. These are the people who make sure net-metering doesn't die and utilities don't make back-door deals with lawmakers. If you do any business in California you should be a member of CALSSA, their policy work and lobbying is critical to the survival and success of our industry. Reach out to Carter Lavin to join CALSSA.

California Energy Storage Alliance (CESA): similar mission to CALSSA, a non-profit organization of industry members with the mission to advance the role of energy storage in the electric power sector. CESA tends to focus more on utility-scale and large commercial markets.

Cell - Battery Cell: "The basic electrochemical unit, characterized by an anode and a cathode, used to receive, store, and deliver electrical energy." (NFPA 855)

Clipping: When more PV energy is produced than the inverter is capable/allowed to output. The amount of energy lost depends on the DC:AC load ratio. The DC:AC load ratio for a PV only system is typically between 1.3-1.5 where all the excess energy produced is lost. For example, a 130 MWdc PV system with a 1.3 inverter load ratio would only output 100 MWac due to the limit on the inverter.

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 1.5-2 with minimal energy lost due to clipping. See animation below, courtesy of Fluence.

Commercial Operation Date (COD): The date a newly installed commercial energy system is scheduled to begin operating regularly after all construction, commissioning, and approvals are completed.

Data Acquisition System (DAS): 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.

DC-Coupled System: a 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 (see NEC Figure 690.1(b)), but other configurations can be done using PV inverters and a power controls system.

Deflagration: Per NFPA 1, "propagation of a combustion zone at a velocity that is less than the speed of sound in the unreacted medium." Translation: The audible rapid spreading and combination of chemicals with oxygen that produces heat and light.

Now what does that mean? Most people think of this as an explosion but technically it's the cause of an explosion, see definition of explosion. It's the moment before an explosion happens when all the chemicals combine, heat up, and rapidly expand.

For battery energy storage systems, deflagration can happen as a result of a major battery failure where cell off gasses build up in an enclosure and are ignited. Burn testing battery systems aims to evaluate that system design for the risk of thermal runaway propagation, deflagration, and fire.

Department of Defense (DOD): 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.

Department of Energy (DOE): 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.

Depth of Discharge (DoD): 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.

Direct Current (DC): 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.

Distributed Energy Resource (DER): 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.

Division of Responsibility (DOR):

Energy Storage Management System (ESMS): "A system that monitors, controls, and optimizes the performance of an energy storage system and has the ability to control the disconnection of the energy storage system in the event of abnormal conditions." (NFPA 855)

Energy Storage System (ESS): In general terms, an Energy Storage System is an assembly of components that can store energy for future use as electrical power.

But which components make up the ESS versus the energy source like a PV system? Where do you draw the line? This sounds like it would be simple to define but once you start getting into the details you'll realize it's not so clear. This is important because different Codes and Standards apply to different components within an ESS + PV system depending on how the definition is interpreted. In short, there is no clear definition yet but there is a SEAC working group working on submitting clarifying language for UL 9540.

For more information on which sections of the NEC apply to a solar plus storage system see the article Solar + Storage Systems and the NEC by Justine Sanchez.

"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." (NEC 2017 Article 706.2)

"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." (NFPA 855)

Explosion: Per NFPA 1, "The bursting or rupture of an enclosure or container due to the development of internal pressure from a deflagration."

Factory-integrated: mechanical or electrical components that are assembled together in the factory by the manufacturer rather than in the field by a contractor.

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

Firm Energy: the amount of electrical energy that a power system is contractually guaranteed to be able to provide continuously and reliably. Learn more here.

Flow Battery: "A type of storage battery that includes chemical components dissolved in liquids where the liquid flows through a reaction zone and stored chemical energy is converted to electrical energy." (NFPA 855)

Ground: the earth, literally the dirt beneath your feet.

Grounded (Grounding): Connected to ground. Most electrical circuits are grounded meaning they have an intended electrical path to ground.

Ground Fault: an unintended electrical path to ground. Per NEC Article 100, "an unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth."

In solar arrays, this is very common when a rodent chews through the wiring insulation to expose live wires that then touch a piece of ungrounded metal racking or some other conductive material that creates a path to ground. Electricity always wants to take the path of least resistance. Metal conducts electricity but so does non-pure water. If you were to touch a live wire with your bare hand while standing on the ground your body would become the path to ground. Why? Because your body is made up of about 60% water, your brain and heart are 73% water.

Ground Loop: when two different points in an electrical circuit are intended to be at the same potential (ie. ground) but are at different electrical potentials. Current will then flow between the two points creating a loop. This can cause electrical "noise" or signal interference.

Hazard Mitigation Analysis: An evaluation of the potential failure modes of an energy storage system and the safety-related consequences attributed to those failures. See NFPA 855.

Hardware-in-the-loop (HIL): a method of testing complex systems controls by simulating the full scale of plant. This is particularly important for large-scale power plants which cannot feasibly be tested at full scale in the field until the project is actually built. An example of HIL testing for a utility-scale energy storage system may include actual ESS equipment that is a fraction of the full scale size and used as a reference to simulate the full scale size of the project.

Incoterms: "International Commercial Terms" published by the International Chamber of Commerce (ICC)?to facilitate commerce around the world. Globally recognized, Incoterms prevent confusion in?foreign trade contracts by clarifying the obligations of buyers and?sellers. Some Incoterms apply to any means of transportation; others apply strictly to transportation across water. For large energy projects, the Incoterms define which party is responsible for what at the project site when equipment is delivered and unloaded.

Infrared (IR) light: A spectrum of light that is not visible to the human eye and typically used to produce thermal images. IR imaging is commonly used in testing and O&M to find "hot spots" on PV modules which is an indication that there is an electrical issue at that spot.

Independent System Operator (ISO): facilitates open-access to transmission lines across the U.S and parts of Canada. They operate the transmission system independently of, and foster competition for electricity generation among, wholesale market participants (i.e utilities). Also see regional transmission organizations (RTOs). Both ISOs and RTOs are regulated by FERC.

International Code Council (ICC): a non-profit organization that provides model codes and standards and building safety solutions that include product evaluation, accreditation, technology, training, and certification. The Code Council's codes, standards, and solutions are used to ensure safe, affordable, and sustainable communities and buildings worldwide.

Interstate Renewable Energy Council (IREC): a non-profit organization that provides thought-leading, fact-based?regulatory policy engagement?and best practice resources to help make affordable, reliable, sustainable clean, and efficient energy possible, including for low-to-moderate-income renters and multi-family dwellers, and in?underserved communities. That was a very long run on sentence. IREC includes helping provide clean energy training for?allied professionals, like solar training for?firefighters and local building code officials.

Inverter Load Ratio: 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.

I-V Curve: Current-voltage characteristic?curve, the "I" stands for current, and the "V" standards for voltage. An I-V curve is a graphical representation of the relationship between the voltage applied across an electrical device and the current flowing through it. It is one of the most common methods of determining how an electrical device functions in a circuit and is used in O&M of PV systems. Read more about I-V curve tracing here.

Large-Scale Fire Testing: "Testing of a representative energy storage system that induces a significant fire into the device under test and evaluates whether the fire will spread to adjacent energy storage system units, surrounding equipment, or through an adjacent fire-resistance-rated barrier." (NFPA 855)

Limited Notice to Proceed (LNTP): a stage in the Sales process before Notice to Proceed (NTP)

Listed: "Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specific purpose." (NEC 2017 Article 100, NFPA 855)

Lithium Iron Phosphate?(LFP or LiFePO_4): a type of lithium-ion battery that uses lithium (Li), iron (Fe), and phosphate (PO_4) in its chemistry to store energy. Note, the 4 in PO_4 is supposed to be a subscript.

Lockout/Tagout (LOTO): the procedure (required by OSHA) to protect workers from hazardous energy (ie. energy that can seriously injury or kill a person) by physically locking and tagging equipment with "Do Not Operate" or "Danger Tag" during commissioning or maintenance activities. Typically the person who does the work on the equipment is in charge of the key(s) to the lock(s) in order prevent someone else from accidently unlocking live equipment while they are still working. Check the OSHA factsheet for more info.

Main Service Panel: For grid-connected systems, the electrical panel of an address where the utility service conductors are connected. This panel will be the first thing after a utility meter and will typically have one to six service disconnects.

Maximum Power Point (MPP): The maximum power produced by a PV module or string of modules, graphically represented as the "knee" of an I-V curve where the current and voltage produce the maximum power, see graph here.

Maximum Power Point Tracker (MPPT): A feature of PV inverters to track the power output and adjust the voltage in order to generate the maximum power for that circuit.

Mica: Mica sheets and plates are used in battery cell and module manufacturing to reduce the risk of thermal runaway propagation. Mica has excellent thermal insulation and electrical insulation properties that act has a barrier to contain a thermal event and can withstand temperatures up to roughly 1300°C. Learn more in this video, fast forward to 9:26.

Midcontinent Independent System Operator (MISO): a traditional Japanese seasoning produced by fermenting soybeans... just kidding! MISO operates the transmission system and a centrally dispatched market in portions of 15 states in the Midwest and the South, extending from Michigan and Indiana to Montana and from the Canadian border to the southern extremes of Louisiana and Mississippi. The system is operated from three control centers: Carmel, Indiana; Eagan, Minnesota; and Little Rock, Arkansas. MISO also serves as the reliability coordinator for additional systems outside of its market area, primarily to the north and northwest of the market footprint. See ISO definition for map.

Minimum Viable Product (MVP): A product that meets the bare minimum requirements to launch and be successful. This can be a physical product, a software product, or even a set of documents (like user manuals and spec sheets). This is often used to define the minimum requirements needed to launch a new product or service with the intention of improving and adding more functionality and/or information later.

Modbus: a data communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). The Modbus protocol uses character serial communication lines, Ethernet, or the Internet protocol for communication to and from multiple devices connected to the same cable or Ethernet network. For example, there can be a device that measures temperature and another device to measure humidity connected to the same cable, both communicating measurements to the same computer. Modbus is often used to connect a plant/system supervisory computer with a remote terminal unit (RTU) in Supervisory Control and Data Acquisition (SCADA) systems in the electric power industry. See SCADA definition.

Module-level Power Electronic (MLPE): exactly what it sounds like, its an electrical device that modifies the energy output of a PV array at a module level. MLPE usually refers to PV optimizers and microinverters. There are usually paired one-to-one with PV modules, but other versions exist that can connect two, three, or four PV modules to one MLPE.

National Electrical Code (NEC/NFPA 70): A book of regulations for electrical and fire safety published by the NFPA every three years and enforced by local jurisdictions. The intent of the NEC is to protect life and property by preventing electrical dangers and fires, it does not cover performance issues like whether a PV system is producing the expected energy.

National Fire Protection Association (NFPA): a global self-funded nonprofit organization, established in 1896, devoted to eliminating death, injury, property, and economic loss due to fire, electrical and related hazards. NFPA delivers information and knowledge through more than 300 consensus codes and standards, research, training, education, outreach, and advocacy.

Nationally Recognized Testing Laboratory (NRTL): Pronounced "nurtle", rhymes with turtle, this is my favorite acronym. An organization recognized by OSHA to perform certification for certain products to ensure that they meet the requirements of both the construction and general industry OSHA electrical standards. Each NRTL has a scope of test standards that they are recognized for, and each NRTL uses its own unique registered certification mark(s) to designate product conformance to the applicable product safety test standards. After certifying a product, the NRTL authorizes the manufacturer to apply a registered certification mark to the product. If the certification is done under the NRTL program, this mark signifies that the NRTL tested and certified the product and that the product complies with the requirements of one or more appropriate product safety test standards. See the current list of NRTLs.

National Renewable Energy Laboratory (NREL): a national laboratory of the US Department of Energy.

New Product Introduction (NPI): the process of taking a new product from its initial concept idea all the way to market. This includes, but is not limited to, research, design, testing, manufacturing, training, marketing, and sales. A good NPI process should be set up in phases so that ideas not worth pursuing are identified early before too much time and resources are wasted.

Nickel Cobalt Manganese (NMC): a type of battery chemistry that uses a combination of nickel (N), cobalt (C), and manganese (M) elements.

North American Board of Certified Energy Practicioners (NABCEP): is a non-profit certification organization for professionals in the field of renewable energy. NABCEP offers certifications and credentials for skilled professionals, specialists and those new to working in the areas of photovoltaics, solar heating, and small wind technologies. The first NABCEP Solar PV Installer certification exam (now called PV Installation Professional) was administered in 2003. Since then, NABCEP has launched and maintained 8 Board Certification Programs and 3 Associate credentials. They also host the best technical training conference each year where people can learn from the top subject matter experts in the industry.

Notice to Proceed (NTP): approval to proceed with project development usually to the next agreed upon check-in point.

Occupational Safety and Health Administration (OSHA): A government body belonging to the US Department of Labor created by Congress with the?Occupational Safety and Health Act of 1970. OSHA ensures safe and healthful working conditions for working persons by setting and enforcing standards and by providing training, outreach, education, and assistance.

Occupiable Space: A room or enclosed space designed for human occupancy. Note, this definition is one that is currently not clearly defined in Code but SEIA is proposing this modified language as the new definition.

Off-gassing: The event in which the battery cell case vents gas due to a rise in the internal pressure of the cell. See NFPA 855.

Operations and Maintenance (O&M): All activities related to properly operating and maintaining each piece of equipment and the system as a whole such that it continues to produce energy safely, optimally, and meets all relevant codes and standards.

Oregon Solar Energy Industries Association (OSEIA): an Oregon-based non-profit trade association founded in 1981 to promote clean, renewable, solar technologies. OSEIA members include businesses, non-profit groups,?and other solar industry stakeholders. They provide a unified and respected voice of the solar industry and focus exclusively on the solar value chain; from workforce development to permitting, advocacy, policy, and regulation for residential, commercial, community, and utility-scale solar projects on the local, state and regional level.

Photovoltaic (PV) Panel System: A PV system with rigid PV modules that are NOT building-integrated (i.e. not PV shingles nor PV tiles).

Power Controls System (PCS): electrical equipment that allows for connecting, controlling, and disconnecting multiple power sources and loads at a particular site. The most common is to switch between a utility feed and an emergency power supply consisting of two or more generators. Power control systems can also be used to connect and manage multiple sources in prime power applications, where utility service is unavailable, and to parallel utility and backup power systems to meet operational objectives or control costs.

PV Optimizer: is a module-level power electronic (MLPE) device installed on the backside of a PV module that serves the purpose of optimizing the energy output of that module. A PV optimizer uses MPPT to smooth the voltage output of each module so that the inverter can output more energy. They are most useful if you have modules that are partially shaded for some of the day or for an array that has multiple planes of PV modules facing different directions or orientations. They are pretty useless and add unnecessary cost if you have a large uniform PV array with no shading.

RACI: Responsible Accountable Consulted Informed, this is a document that summarizes the roles and responsibilities of those involved in a project or program.

Raw Material Index (RMI) Pricing: equipment pricing that adjusts monthly based on the pricing of key raw material commodities (such as lithium, copper, electrolyte) that are used to manufacture that product. Raw material costs generally use a three month average.

Curious how much commodities change in price? Check out the graph below to see the change in price of copper from January to April 2022:

Regional Transmission Organizations (RTOs): similar to ISOs and regulated by FERC, a joint group of utilities who operate the transmission systems for a particular region and develop innovative procedures to manage the transmission of electricity equitably. See definition of ISOs.

Remote Terminal Unit (RTU): is a?microprocessor-controlled electronic device that interfaces mechanical and/or electrical equipment in the physical world to a SCADA system. RTUs send telemetry data to the supervisory computer(s) of a SCADA system and receive commands to control the equipment on site. Other terms that may be used for RTU are?remote telemetry unit?and?remote telecontrol unit.

Roundtrip Efficiency (RTE): is the ratio of total output energy divided by total input energy over one charging/discharging cycle using rated input and output power. "Energy In"?includes energy losses during charging due to the switchgear, AC lines, AUX loads, transformer, inverter, and DC lines. "Energy Out"?includes energy losses during discharge due to the battery storage system, DC lines, inverter, transformer, AUX loads, and switchgear. Site temperature, discharge duration, cycling profile, and AUX load assumptions all greatly affect RTE.

Solar Energy Industries Association (SEIA): a non-profit trade organization founded in 1974, focused on creating and changing policies that create jobs in every community and shape fair market rules that promote competition and the growth of reliable, low-cost solar power. SEIA works with its 1,000 member companies and other strategic partners to build a comprehensive vision for the Solar+ Decade through research, education, and?advocacy. SEIA is engaged with policymakers at the regulatory and legislative levels in Washington, D.C. and across the country to establish supportive policy frameworks that allow solar to compete in the marketplace and offer cost-competitive, reliable energy to?consumers. Check out their website for all the great work they do and become a member if you're not already.

Standard: As defined in the ICC Reference Standards Guide: "A standard is a published technical document that represents a stakeholder consensus on how a material, product or assembly is to be designed, manufactured, tested or installed so that a specific level of performance is achieved. Standards are primarily developed by industry organizations and professional associations incorporating the views of interested parties (stakeholders). A standard is developed in response to an identified need and typically contains information which is based on experience, knowledge, testing, analyses and research.

A standard is not intended to be used as primary law but as a referenced authoritative resource. While a model code becomes law when it is adopted by a jurisdiction, a standard becomes law to the extent to which it is referenced in an adopted model code. When a standard that is referenced in the code (first-tier reference) in turn references another standard (second-tier reference), the second-tier referenced standard is equally applicable, again, to the prescribed extent of the reference to it in the first-tier reference. This trail of applicability extends throughout all tiers of references."

Standards Technical Panel (STP): a group of individuals organized by UL tasked with reviewing and approving proposed changes to UL technical standards. The STP members include UL staff (chair and project manager) and a balance of stakeholders including industry producers, supply chain, commercial/industrial users, general STP members, AHJ/regulators, government representatives, testing and standards, consumers, and international delegates. Other standards organizations have similar groups but the term STP is unique to UL. The IEC uses Technical Committees (TC) to serve the same function.

Storage as a Transmission Asset (SATA or SAT): the use of an energy storage system as part of the electric transmission or distribution infrastructure to assist with the delivery, rather than supply, of electricity.

"By integrating a storage resource into transmission equipment, SAT can inject or absorb electricity to facilitate power flows on transmission lines over a certain period of time, like adding a lane to a highway just for rush hour traffic. Used in this way, storage can enhance existing transmission lines or even serve as an alternative to building new transmission projects." - Sharon Thomas, read her full article by clicking the link above.

Substantial Completion: the stage when the construction of a project is deemed sufficiently completed and the site is capable of operating though may not yet have permission to operate from the utility and/or some final steps may still need to be completed. This milestone can vary project to project but is usually defined in the contract and may have legal implications if substantial completion is not done by the agreed upon date. It is a major milestone for any project which is why you may see a press release or announcement from an EPC when a project reaches substantial completion. Learn more here.

Supervisory Control and Data Acquisition (SCADA) Systems: Large-scale data collection and controls commonly used in a variety of industrial applications such as utility-scale power plants. Similar to monitoring but with the added ability to control the system and more often incorporates AI learning. Learn more in this video tutorial here.

Sustainable Energy Action Committee (SEAC): a forum of industry stakeholders to collaboratively identify and find solutions for issues that affect the installation and use of sustainable energy systems (solar PV, energy storage, etc.) SEAC provides clarity and a better understanding?of sustainable energy standards and requirements that improve?practices and procedures to effectively and optimally support the growth and transition to zero net energy communities throughout the U.S.

Synthetic inertia (SI):

System Advisor Model (SAM): a free software provided by NREL for modeling the performance and economics of renewable energy projects.

Transmission System Operator?(TSO): is the European equivalent to an ISO or RTO in the United States. A TSO is an entity entrusted with the transmission of energy in the form of natural gas or electricity on a national or regional level and is defined by the European Commission.

Thermal Runaway: "the condition when an electrochemical cell increases its temperature through self-heating in an uncontrollable fashion and progresses when the cell's heat generation is at a higher rate than it can dissipate, potentially leading to off-gassing, fire, or explosion." (NFPA 855)

Underwriters Laboratory (UL): UL is actually two companies in one, a not-for-profit side and a for-profit side. The not-for-profit side of UL develops and publishes industry standards and provides research, education, and outreach on those standards. The for-profit side provides testing, inspection, certification, software as a service, and advisory services. You can read all UL standards for free online via the UL standards website.

Utility (Electric): "All enterprises engaged in the production and/or distribution of electricity for public use including those that are typically designated or recognized by governmental law or regulation by public service/utility commissions and that install, operate, and maintain electric supply such as generation, transmission, or distribution systems." (NFPA 855)

Utility Interactive: An electrical system with a local energy supply, such as solar PV and/or batteries, that is electrically connected to, intended to operate in parallel with, and can deliver power to the utility grid.

Virtual Synchronous Machine (VSM): "emulate the transient electromechanical characteristics of traditional synchronous machines, offer a unified interface for smart grid integration. With these technologies, all the renewable energy generators as well as the flexible loads could take part in regulating the grid frequency and voltage, thus improving the power grid's stability." From Review and Applications of Virtual Synchronous Machines Technologies | IEEE Conference Publication | IEEE Xplore Sorry still need to translate this definition into plain English.