Guide to Solar Jargon

The following clarifies commonly used terms within the solar industry. We have also provided some specific terms that apply to agrivoltaics. We have listed them in alphabetical order.

“Behind the Meter” “Behind the meter” represents something on the power plant owner’s side of the meter that sits between a power plant and the grid. This term is often used to describe when electricity generated on-site is also consumed. Some projects may be able to be “fully behind the meter,” meaning that no electricity is distributed to the grid. Generally, this is uncommon, and projects still connect to the grid even if they plan to consume most of the energy on-site. Connecting to the grid provides flexibility and compensation for excess energy generated.

“Center-on-Center” Center-on-center is a measure of row width, representing the distance between the center of a post to the center of a post in an adjacent row.

This is an important metric that Hyperion considers when designing a solar array since the distance center-on-center needs to be compatible with the farm plan and farming equipment. Specifically, current and future machinery need to fit within this row width at the ground level.

That said, it is not the only measure of row width that Hyperion considers when designing a solar project since the solar panels have less space between them than the posts. Hyperion also considers this shorter row spacing for compatibility with farming equipment, although this spacing is applicable a few feet above ground instead of at ground level.

“In Front of the Meter”“In front of the meter” represents something on the utility’s side of the meter that sits between a power plant and the grid.

AC PowerAC is a complex technical concept but is relevant because it represents the type of electrical current that the grid uses. Solar panels and batteries operate using “direct current” (DC), so electricity needs to be converted from DC to AC before it can be delivered to the grid. The piece of solar equipment that handles this is called an “inverter.”

Cabling Cabling is another word for wiring. A solar project requires cabling of various sizes, lengths, and voltages to deliver electricity from each solar panel to the grid.

Capacity The term “capacity” refers to the maximum power rating of a power plant. Think of this like the top speed in your car. A project often has a larger DC capacity than its AC capacity so that the project can produce at its AC capacity (what actually goes onto the grid) for a longer period of time throughout the day.

Community Solar Garden A community solar garden is a solar project that provides electricity to the community. Each state has unique community solar rules, but generally, a community solar garden takes subscriptions from residential and nonresidential subscribers who purchase a portion of the electricity generated at the site. The utility represents this as a credit on their bill and the subscriber pays the difference (if applicable).

DC Power DC refers to “direct current,” meaning electricity flows in only one direction. Both solar panels and batteries operate using direct current. Solar panels produce direct current, but the grid operates on alternating current (AC). This means that the electricity generated by a solar panel needs to be converted from DC to AC before it can be delivered to the grid. The piece of solar equipment that handles this is called an “inverter.”

Energy Storage Energy storage is a system that can store energy and dispatch it at a later time. The most common form of energy storage today are batteries, sometimes referred to as a “battery energy storage system” (BESS).

A valid critique of solar energy is that it generally produces at its peak at times (e.g. mid-day) that are not coincident with peak energy demand (e.g., early evening). As a result, solar provides an excess amount of energy during the day and cannot supply enough energy at peak demand times, which creates challenges for the grid. This is a phenomenon called the “duck curve” (source).

Energy storage can be an important component of a solar project. The strategy involves storing surplus energy generated during the day and dispatching it later when energy demand is high. While this technology can be advantageous, it is not required at most sites.

BESS have a fire risk, so Hyperion only develops projects with BESS if it does not threaten the safety of the agricultural operation and makes technical and commercial sense for the project. Sometimes, Hyperion is required to add storage by law, but this depends on state and local regulations, which vary on a case-by-case basis.

Inverter An “inverter” is a piece of electrical equipment that converts DC current to AC current. These are one of the most important pieces of electrical equipment at a solar project.

Megawatt Hour A megawatt-hour (MWh) is a measure of energy, and it is equal to 1,000 kilowatt-hours or 1,000,000 watt-hours. Energy is the quantity of electricity generated. This is why you may see your utility bill measured in kilowatt-hours (kWh) with pricing measured in dollars per kilowatt hour ($/kWh).

Think of energy like the distance you travel in your car or the amount of water that flows through a river. Energy is measured in watt-hours and uses metric prefixes to communicate differences in scale (e.g., kilowatt-hour, megawatt-hour, gigawatt-hour, etc.). A megawatt-hour means that electricity was generated at a rate of one megawatt per hour. Energy equals power multiplied by time, much like how distance traveled equals speed multiplied by time; only the units look slightly different.

Megawatt A megawatt (MW) is a measure of power and is equal to 1,000 kilowatts or 1,000,000 watts. Power is the rate at which electricity can be generated. Think of power like the speed of your car or the current of a river. Power is measured in watts, and it uses metric prefixes to communicate differences in scale (e.g., kilowatt, megawatt, gigawatt, etc.).

Module “Module” is another word for solar panel.

Posts in a Solar Array A post, also called a “pile,” is a steel beam vertically mounted in the ground. It serves as the foundation for racking and modules. These posts are usually driven several feet underground for stability and extend several feet out of the ground. Generally, every foot that a post sticks out above the ground represents a foot that the post is driven into the ground. However, that ratio varies by project depending on the soil type and composition.

Racking “Racking” is the structural steel infrastructure on which modules are mounted. It is designed to consider topography, stability, and tracking (the panel position as they follow the sun).

Solar Array A solar array is a formation of many solar panels, usually in a grid. It generally consists of multiple solar panels strung together in one or more rows.

Transformer A “transformer” is a piece of electrical equipment that changes the electricity voltage. Solar produces electricity at a relatively low voltage, while the grid operates at a very high voltage. A transformer is necessary to take low-voltage AC energy from the inverter and increase its voltage to match the grid infrastructure voltage at the point of interconnection.

A transformer at a solar project is sometimes referred to as a “step-up transformer” since it “steps up” the voltage of the electricity before it is delivered to the grid. The transformer is usually the last piece of equipment owned by the solar owner before electricity passes through a meter and onto utility-owned infrastructure.