Transmission & Interconnection FAQs

Offshore

How did Mayflower Wind decide the route for the export cables?

Through technical analysis of the available grid connection points, Mayflower Wind identified Falmouth and Somerset, Massachusetts as the optimal delivery points to maximize the potential of the lease area capacity. We are pursuing dual export cable routes to deliver the power to electricity customers via two interconnection points.

Route alternatives are currently being evaluated according to environmental, technical, and commercial factors, and will be presented in the project’s Construction and Operations Plan (COP). No final decisions on site locations for project facilities will be made until a full routing analysis has been completed. Baseline surveys are currently underway to gather data on-site and assess the suitability of alternative sites for a complete and reasoned analysis of the alternatives.

Why don’t the offshore wind developers use a shared transmission cable system?

Each leaseholder bears the sole risks and responsibilities for delivering power to a point of interconnection on the regional grid.

The regional Independent System Operator enforces a “single-source contingency” rule that limits the capacity of a single project at a single point of grid interconnection to no more than 1,200 megawatts. In addition to this rule, existing conditions further limit how much energy can be injected at a specific location without major upgrades to the system.

The Massachusetts Department of Energy Resources evaluated the merits of a coordinated offshore transmission network in 2020, and found that the costs outweigh the benefits. A major investment in new onshore grid infrastructure would create greater value for all customers, by enabling full maximization of the offshore wind resources.

In order to generate the full potential of the lease areas, multiple export delivery cables will be constructed from each lease area to shore, at different grid connection points.

 

Onshore

Where will the project make landfall?

Mayflower Wind is pursuing dual export cable routes to deliver the power to electricity customers via interconnection points at Falmouth and Somerset, Massachusetts.

We are examining two alternative landfall locations along Falmouth Heights Beach in Falmouth.

For the route to Brayton Point, landfall locations are being evaluated adjacent to the Sakonnet River on the northern portion of the Town of Portsmouth, Rhode Island as the cable makes it way to Somerset, as well as the southwestern side of the Brayton Point commercial site itself.

No final decisions on site locations for project facilities will be made until a full routing analysis has been completed. Baseline surveys are currently underway to gather data on-site and assess the suitability of alternative sites for a complete and reasoned analysis of the alternatives.

How did Mayflower Wind decide the routes for the underground cables and overhead transmission line?

Transmission route options are currently undergoing evaluation as part of the Mayflower Wind Construction and Operations Plan (COP). Routing analysis for the onshore transmission infrastructure takes into consideration multiple factors, such as feasibility for construction, environmental resources, social impact, cultural resources, and other local concerns. The objective is to minimize impacts while aligning with safety, cost, and engineering considerations. Routing along existing linear infrastructure (such as existing utility right-of-way (ROW) and roads), previously disturbed areas, and existing cleared land are widely accepted as best practices.

No final decisions on site locations for project facilities will be made until a full routing analysis has been completed. Baseline surveys are currently underway to gather data on-site and assess the suitability of alternative sites for a complete and reasoned analysis of the alternatives.

What safeguards and practices will be deployed to avoid, minimize, or mitigate impacts to the coastal and near-shore environment from the cable landing?

Mayflower will be working with federal, state and local environmental agencies to avoid and minimize environmental impacts to the coastal and near-shore environment. The most effective method is to avoid direct impacts using construction methods, such as horizontal directional drilling (HDD) and time of year restrictions during seasonally important time periods. Potential impacts on the coastal and near-shore environment and environmental protection measures will be analyzed through the project’s Construction and Operations Plan (COP).

Who will approve or disapprove of the proposed cable routes?

Federal, state, and local review from a variety of regulatory authorities is required prior to the start of construction.

At the Federal level, the Bureau of Ocean Energy Management is one of the primary regulatory bodies that oversees the permitting of offshore wind energy in federal waters. Other notable federal agencies with jurisdiction over Mayflower Wind’s proposed activities include the National Atmospheric and Oceanic Administration, U.S. Coast Guard, U.S. Fish & Wildlife Service, and the Federal Aviation Administration, among others.

At the state level, the Rhode Island and Massachusetts Energy Facility Siting Boards (EFSB) and the Environmental Policy Act office (MEPA) are the two key regulatory processes that drive most of the other state and local permitting timelines. The EFSB is an independent state board that reviews proposed large energy facilities, including electric transmission lines, to determine if they serve the public interest.

At the local level, Mayflower Wind will work cooperatively with the Towns of Falmouth, Portsmouth, and Somerset on construction scheduling, including seeking licenses where necessary to facilitate construction access.

Will fiber communication cables be co-located with the power cables?

Yes, dedicated communication cables will be installed to transmit information between the offshore and onshore substations.

Interconnection

What is the project’s Point of Interconnection (POI)?

The Mayflower Wind project will interconnect into the regional electric grid through two distinct POIs in Falmouth and Somerset, pending ongoing interconnection studies.

What studies have been conducted to determine whether the project can safely and reliably interconnect into the regional grid?

Mayflower Wind is progressing through the Independent System Operator- New England (ISO-NE) study process to determine how the project can safely and reliably interconnect into the New England transmission system. This includes conducting a Feasibility Study and System Impact Study, which are performed to ensure that system reliability criteria and standards for no adverse impact are met.

Electricity Basics

How is electricity like water?

The comparison between electricity passing along cables and water flowing through pipes is not an exact parallel.  However:

  • The rate of water flow is similar to the current in an electric circuit, measured in amperes/amps (A)
  • The water pressure is akin to push or voltage in an electric circuit, measured in volts (V)
  • As sand in a pipe resists water flow, the substance of the conductor in an electric circuit resists the electric current, measured in Ohms (R/Ω)
What is electric charge?

Charge is a physical property of matter that can be positive or negative. Electrons are particles that spin around the nucleus of an atom. Electrons carry a negative charge, the rest of the atom (proton) has a positive charge. Electrostatic force operates between the charges- those of the same type repel each other, while charges of the opposite type attract one another. Electrons flow along a circuit, or pathway of conductors. 

Charge is measured in coloumb (C). 

1 C= 1 A (ampere) per second

What is electric current?

Current is the flow of electrons through a circuit, measured in amperes/amps (A). 

Resistance in the electrical circuit is measured in Ohms (R/Ω). Conductors are elements with high conductivity that aid in the flow of electrons (ie. copper). Insulators are elements with low conductivity that prevent the flow of electrons ((ie. glass, ethylene, or propylene).

A (current) = V (voltage)/R (resistance)

What is electric voltage?

Voltage is the electric potential difference, or the “push” of the flowing charge, measured in volts (V). The greater the resistance, the more volts are needed to push the current through the circuit.

V (voltage) = W (power) /A (current)

What is a joule?

The work required to move 1 couloumb (C) of electric charge through an electric potential difference of 1 volt (V) is called a joule (J). 

A joule is also a measurement of the energy dissipated as heat when a current of 1 A (ampere) passes through resistance of 1 Ohms (R) for one second.

1 joule (J) = 1 watt (W) per second

What is a watt?

A watt is a unit of measuring power. 

W (power) = V (voltage) x A (current)

1 watt (W)= 1 joule (J) per second

A megawatt (MW) is a typical reference for bulk electric power. 

1 MW= 1,000,000 watts (W) = 1,000 kilowatts (kW) = enough to power >650+ homes

What is the difference between electric power and energy?

In this comparison, electric power is like the flow rate of water through a pipe. It is the rate, per unit of time, at which energy is transferred by a circuit. It is measured in watts or kilowatts.

1,000,000 watts (W) = 1,000 kilowatts (kW) = 1 megawatt (MW)= enough to power >650+ homes

1 GW= 1,000 MW= 1,000,000 kW

The all-time summer peak electric power demand in the New England regional system of 28,130 MW (28 GW) was set in 2006. The all-time winter peak demand of 22,818 MW (23 GW) was set in 2004.

Energy is akin to the amount of water that ends up in the bathtub. It is the amount of electricity that is produced over a period of time, measured in watt-hours or kilowatt-hours.

1 kilowatt-hour (kWh) = 1000 volts x 3600 seconds = 3,600,000 watt-seconds or joules= 3,600 kilojoules (3.6 MJ)

1 kWh= 0.001 megawatt-hour (MWh)= 100 watt lightbulb operating for 10 hours

In 2021, the total amount of energy served in the New England regional system was 118,664 gigawatt-hours (GWh).

1 GWh = 1,000 MWh= 1,000,000 kWh

What is alternating current?

A flow of electric charge in which the direction of the current and voltage of the circuit reverse 60 times per second, measured as 60 Hertz (Hz).

What is direct current?

A flow of electric charge in which the direction of the current and voltage of the circuit are constant. One pole is always negatively charged, the other pole is always positively charged.

What is installed or nameplate capacity?

The maximum rated output of electricity that a generator can produce under conditions designated by the manufacturer, measured in megawatts (MW).

Improvements in wind turbine design have increased installed capacity in the past few years. For example, the General Electric Haliade turbine model increased its nameplate capacity from 6 MW (installed at Block Island Wind Farm) to 13 MW (under construction at Vineyard Wind I project) in the period of 2015-2021.

Technological innovation will continue to drive down costs and improve performance.

What is a capacity factor?

The capacity factor compares how much electricity a generator actually produces with the maximum it could produce at continuous full power operation during the same period. It is expressed as a percentage. The higher the capacity factor, the lower the levelized cost of energy (LCOE), a typically used measure of the competitiveness of different generating technologies.

The capacity factor is determined by the availability of the wind resource, the swept area of the turbine, and the nameplate size of the generator.

Offshore wind projects have capacity factors exceeding 50% on an annual basis.

Improvements in wind turbine design have not only helped to increase their capacity factor, but also the maximum power they can produce (installed capacity). For example, the General Electric Haliade turbine model increased its nameplate capacity from 6 MW (installed at Block Island Wind Farm) to 13 MW (under construction at Vineyard Wind I project) in the period of 2015-2021.

Technological innovation will continue to drive down costs and improve performance.