How do battery energy storage systems work?

Energy from the power grid or from renewable energy sources is delivered via a bi-directional inverter, which converts the energy from alternating current (AC) into direct current (DC). Today's batteries can only store DC. This energy goes into an array of batteries that is typically housed within a battery container or a building structure.

When the energy is needed on the power system, the inverters are then used again, but this time to convert the DC from the batteries into AC. Once the power has been transformed, it is stepped up in voltage and subsequently sent to an on-site substation or directly to a distribution or transmission line. The electricity is then distributed to homes, schools, businesses, and other consumers.

A Battery Management System monitors the individual cells and controls the voltage, temperature and current for safe, reliable transfer of energy. The system automatically shuts off if the batteries are operating outside of predefined parameters.

The electricity is then distributed to homes, schools, businesses and other consumers.

What are the components that make up a battery energy storage system?

A storage system consists of:

  • Individual battery cells (the size of an iPad)
  • These cells are put into battery modules and stacked on racks
  • The racks fill containers, not unlike a storage container you’d see on a ship or truck
  • The containers are paired with inverters to convert DC-AC electricity
  • The system includes HVAC or similar cooling equipment to maintain temperature control
  • Can be paired with a renewable energy asset (solar, wind) or stand alone

 

What is the value of energy storage for both a utility and its customers?

Battery storage helps optimize the way the power grid delivers electricity to customers with a wide variety of use cases, including:           

  • Smoothing out fluctuations in frequency and voltage
  • Replacing traditional peaking generation units
  • Reducing energy losses and waste
  • Avoiding the need for some system upgrades, including big transmission projects
  • Extending the hours a renewable energy project can operate, i.e., even after the sun goes down or the wind stops blowing
  • Allowing customers to enjoy more renewable energy, more hours of the day

Energy storage technologies are highly flexible and controllable resources, capable of fast response to system needs and near instantaneous ramp to full capacity in either charge or discharge mode. Projects can be scaled in size to match any site—be that co-located with a power plant, installed at a substation, directly connected to a transmission or distribution line, or sited at customer premises—and can provide services interchangeably to wholesale markets, distribution grids, and end users.


What type of batteries will the storage system employ?

Most battery energy storage systems employ lithium ion batteries.

  • Lithium ion is the dominant technology because it benefits from more than $100 billion in R&D from the electric vehicle industry
  • This is also the prevalent battery technology found in laptop computers, iPads, and other electronics
  • NextEra Energy Resources has its own battery testing facility to measure battery performance and degradation, as well as testing alternative technologies


What’s the risk of a battery energy storage system catching fire?

  • All of the battery module designs included in our facilities undergo rigorous industry testing and certification related to fire safety, in order to minimize the risk that a failure of any single battery cell or module spreads to adjacent batteries or other equipment
  • NextEra Energy Resources has a control center in Florida that is staffed 24 hours a day, 7 days a week, that monitors and can control the operation of all of our assets remotely
  • The company works with local first responders and fire officials to educate them about the technology and coordinate any response, in the unlikely event of a fire
  • NextEra Energy Resources storage systems comply with all local, state, and federal regulations in terms of operations, fire protection, and disposal of waste from storage operations

 

Has your company built other energy storage systems?

NextEra Energy Resources has approximately 700 MW of operational energy storage, including:

  • Frontier Battery Energy Storage System, Illinois
  • Elmira Energy Storage, Ontario
  • Gopher Energy Storage, Anoka and Isanti counties, Minnesota
  • Mantua Creek Battery Energy Storage System, New Jersey
  • Green Mountain Battery Energy Storage, Pennsylvania
  • Casco Bay Battery Energy Storage System, Maine
  • Pima Battery Energy Storage System, Arizona
  • Blue Summit Energy Storage, Texas
  • Minuteman Storage, Massachusetts
  • Montauk Energy Center, New York
  • East Hampton Energy Center, New York
  • Parry Energy Storage, Parry Sound, Ontario
  • Pinal Energy Storage, Arizona
  • Rush Springs Energy Storage, Oklahoma
  • Blythe II Storage, California
  • Various behind-the-meter energy storage projects in California and Massachusetts
  • Blythe III,  California
  • Blythe 110, California
  • McCoy, California

Additionally, the company is developing nearly 2 GW of energy storage projects across the U.S. and Canada that are under long-term contracts. Over one-third of the new solar projects we’re developing for customers now includes a storage component.

 

What is the typical life of lithium-ion (“batteries”)? How are batteries disposed of at their end of life?

The typical life of the batteries range from 10 to over 20 years. Although used lithium-ion batteries are NOT considered hazardous waste by the EPA, Duane Arnold Solar will follow optional EPA guidelines addressing the responsible disposal and recycling of batteries at their end of life. There are a variety of options in the industry to recycle used lithium-ion batteries. Duane Arnold Solar anticipates that the batteries will either be transported to a recycling center or reclaimed by their manufacturer for re-use or recycling. Duane Arnold Solar will not dispose battery cells in landfills.

 

A battery energy storage system can help balance the load on the power grid and deliver electricity to customers when it is most needed.

To achieve this balance, a battery system can be positioned at various points between a power plant (or renewable energy generator) and the homes and business that consume the electricity.

The battery system includes individual battery cells, collected into modules and housed in a specially-designed, climate-controlled storage container.

A computerized monitoring system provides information, including up-to-date weather forecasts, power prices, historical electrical use, the amount of charge remaining in the batteries and when to use the energy storage system.

When demand for energy is low, such as the middle of the day when people are at work or school or overnight when they’re sleeping, the battery charges from the power plant and stores the electricity.

The battery discharges to the power grid when customer demand for energy is high, such as in the morning when people are getting ready for work or school, or in the early evening, when they’re returning home, cooking dinner and watching TV.

Power When It's Needed

 

demand-high300-2.png

 

BatteryStorageGraphic-morning-200-no-back.png

Morning

Lights switched on

Early morning lights

Morning cooking

 

BatteryStorageGraphic-evening-200-no-back.png

Evening

Residents return home

Evening cooking

TV is on

AC is set colder (summer)

Eelectric heating is turned on (winter)

 

 

demand-low300-2.png

 

BatteryStorageGraphic-mid-day-200-no-back.png

Mid-day

Leave for work and school

AC is set higher

 

 

BatteryStorageGraphic-night-time-200-no-back.png

Night-time

Lights are off

Businesses are closed

Residents are sleeping

 

 

What is solar energy used for?

Once converted into electricity, solar energy is used in homes and businesses just like any other form of electricity.

 

What are some advantages of solar energy?

After the initial investment in solar-energy equipment, the costs are minimal since the sun provides free "fuel." These facilities are not affected by the supply and demand of fuel or subject to price volatility, and solar energy can help reduce America’s dependence on foreign sources of energy. Solar energy is also clean and renewable, which helps protect our environment.

 

How does Solar Energy Work?


NEER Solar No Text GIF

1. As light hits the solar panels, the solar energy is converted into direct current (DC) electricity.

2. The direct current flows from the panels into power inverters and is converted into altering current (AC) electricity, which is suitable for use by homes and businesses.

3. The AC electricity from the power inverters is collected using cables and delivered to a central electrical substation, where it passes through a power transformer.

4. The electricity travels through transformers, and the voltage is boosted for delivery onto the transmission lines.

5. Clean, renewable, American-made solar electricity is delivered to homes and businesses.

 

How many solar facilities does your company have and where are they located?

Through its subsidiaries, NextEra Energy Resources is the world’s largest generator of renewable energy from the wind and the sun. We currently have ownership interests in 3,160 MW of operating solar projects (as of Dec. 31, 2020), representing universal-scale solar facilities in 27 states, as well as multiple small-scale (distributed generation) solar projects.

 

How did your company choose this location for the Duane Arnold Solar project?

We carefully select sites for potential solar project development based on a number of factors, including: (i) suitability for solar generation; (ii) interest of participating landowners; (iii) proximity to existing infrastructure; (iv) existing transmission and injection capacity; (v) constructability; (vi) environmental factors; and (vii) suitability with cultural and historic resources. With respect to generation suitability, Duane Arnold Solar concluded that the site was suitable for solar development based on a review of nearly 25 years of weather and satellite data.

 

Who is the client for this energy?

Duane Arnold Solar will develop, design, permit, and construct Phases I and II of the Project. Alliant Energy, through its subsidiary Interstate Power & Light Company (IPL), will purchase the project and distribute the renewable energy to its customers, including Iowa residents.

 

Will eminent domain be used in any of the phases?

No. The Project will be located 100% on voluntary easements/permits. As such, Duane Arnold Solar will not seek the use of eminent domain.

 

How much are landowners being paid?

Landowners who choose to participate in the Duane Arnold Solar Project receive payments that can help them enhance and diversify their incomes. Agreements with participating landowners include an (1) Option Agreement - to hold a solar easement area for a defined period of time; and (2) a Solar Lease and Easement Agreement. Participating landowners are paid for the option agreement through an annual payment. The option agreement can be converted to a Solar Lease and Easement Agreement. Under the Solar Lease and Easement Agreement, the participating landowner is paid per utilized acre per year. The specific payment terms with participating landowners are confidential.

 

How long are the lease agreements?

The term of the Option Agreement is typically 5 years. The term of the Solar Lease and Easement Agreement is 30 years with a potential 10-year extension.

 

Who has the authority to approve this Project at the state and local levels?

The siting of the Project will be subject to approval by the Iowa Utilities Board (“IUB”) and the Linn County Board of Supervisors.

 

Will the Linn County Board of Supervisors be asked to change the local land use ordinance as part of their decision to grant the permit for Duane Arnold Solar?

Because the Project falls within the definition of a Utility Scale Solar Installation set forth in the Linn County Ordinances, the Project must be located in a Renewable Energy Overlay District (“Overlay District”). This requirement was created by ordinance passed in December of 2020.1 Duane Arnold will be required to go through the rezoning process in order to have the County create the Overlay District that encompasses the Project parcels and approve the Project for development.

 

How does this project help Iowa meet its energy? Why use farmland for a solar project?

In the aggregate, Iowa produces enough energy to meet the equivalent of its energy needs, but it does not produce enough to meet those needs during every hour of every day.

Moreover, location on farmland is one factor considered in determining whether and where to locate renewable energy facilities. The Project has a limited impact on cropland acreage in Iowa. For example, the Project Site of Phase I of the Project consists of approximately 316 acres, roughly 90 percent of which is currently being used to farm various types of row crops. Similarly, Phase II of the Project will be located on approximately 816 acres. Collectively, this represents only 0.002% of Iowa’s 26 million acres of cropland. Agricultural production on these properties will be suspended for the life of the Project. Similarly, the Project site is less than one percent of Linn County’s 324,500 acres of farmland. However, following Project decommissioning, the Project Site will be available to return to agricultural production.

The Project will not have an adverse impact on agricultural production on the surrounding areas. A vegetative ground cover mix will be planted and maintained throughout the Project Site. This will manage erosion by increasing stormwater infiltration. Stormwater infiltrates soil at a higher rate on vegetative ground cover than on cultivated cropland. As such, the change to perennial vegetation will manage additional runoff resulting from the solar modules and access roads.

 

Why didn’t NextEra continue to operate Duane Arnold Nuclear Plant?

NextEra Energy Resources, LLC (“NEER”) and its subsidiaries are wholesale providers of power and NEER is the owner and operator of the Duane Arnold nuclear plant. As announced in 2018, the customer for the Duane Arnold nuclear plant – Alliant Energy – decided to terminate its power purchase agreement with the nuclear plant early and replace some of the generation with energy provided by wind investments in Iowa. According to the CEO of Alliant Energy, this decision resulted in significant savings for Alliant’s customers -- nearly $300 million on a net present value basis, over 21 years.2

 

How will the project minimize environmental impacts?

The Project has been sited and designed to avoid and minimize impacts to environmental resources in the Project area. For example, the Project is designed to avoid impacts to all jurisdictional wetlands and waterbodies. In the event impacts are subsequently identified, any impacts will be permitted in accordance with the United States Army Corps of Engineers (“USACE”) and, if applicable, Iowa Department of Natural Resources (“DNR”), regulations. In addition, the Project has been sited to avoid impacts to forest areas and limit tree clearing activities in the Project area.

 

Can the Project Site be used for farming in the future?

Yes. When the Project ceases operation, the facilities will be decommissioned and dismantled and the site restored to its pre-construction condition. A decommission plan will be filed with both the IUB and the county.

To facilitate a return to agricultural use following decommissioning, the Project land will be tilled to break the new vegetative growth, which will enhance the topsoil condition. Accordingly, the soil condition on the site will be the same or in better condition than before the Project. Once the Project is fully decommissioned, each property owner can sample the soils and, as needed, add fertilizer to match the crop(s) to be planted. As such, it is very likely the cropland will be returned to pre-construction yields.

 

How are the solar panels disposed of and who takes care of that?

At the end of the Project’s useful life, the Project owner will assess whether to cease operations and decommission the Project or to replace equipment and attempt to extend the life of the Project. To the extent possible, Project equipment will be reconditioned, resourced, and/or recycled. For example, solar panels typically consist of glass, polymer, aluminum, copper, and semiconductor materials that can be recovered and recycled at the end of their useful life. Any materials that cannot be recycled will be disposed of at approved facilities.

 

Do the panels have materials that are harmful to the environment?

Modern photovoltaic (PV) solar panels are made of materials typical of those found in electronic equipment and are encased, so as not to pose a concern for the water supply or public health. As stated previously, Solar PV panels typically consist of glass, polymer, aluminum, copper, and semiconductor materials that can be recovered and recycled at the end of their useful life. Crystalline silicon panels, which are being considered for the Project, represent approximately 90 percent of solar panels in use today. Research has shown they do not pose a material risk or toxicity to public health and safety.

Moreover, to provide decades of corrosion-free operation, solar cells are encapsulated from air and moisture between two layers of plastic, with a layer of tempered glass and a polymer sheet or industrial laminate. In the same way a windshield cracks but does not shatter when broken, a damaged solar cell does not generally create small pieces of debris.

 

Can the panels be replaced?

Yes. We monitor the operations of our solar facilities 24/7. Should any of the panels sustain damage that would impact their safe and efficient operations, our solar technicians will replace them.

 

How does your company work with neighboring landowners to mitigate the visual impact of the Project?

In response to reasonable requests by participating and non-participating landowners, Duane Arnold Solar will consider screening vegetation or other similar measures on a case-by-case basis. Duane Arnold Solar has discussed potential mitigation measures with participating and adjacent non-participating landowners. These discussions will be on-going through construction and continue thereafter.

 

What setbacks will be used for the Project?

For Phase I and II of the Project, the fence line setback ranges between 50 feet and 80 feet from non-participating landowner property lines and at least 300 feet from any non-participating landowner dwelling.

 

Will this Project produce a net savings in fossil fuels emissions?

Yes. Solar energy is one of the most efficient sources of energy generation with respect to limiting carbon dioxide equivalent emissions, as emissions are primarily produced during the manufacture of panels and not during operation. The IUB applications include air emissions analyses comparing the estimated emissions of the Project to equivalent fossil fueled-fired facilities. Phase I is estimated to reduce CO2 emissions by approximately 3.14 million metric tons compared to an equivalent coal-fired facility and 1.355 million metric tons in comparison to a natural gas facility. Phase II is estimated to reduce CO2 emissions by approximately 9.49 million metric tons compared to an equivalent coal-fired facility and 4.1 million metric tons in comparison to a natural gas facility. By design, storage batteries do not create any waste product during their charging and discharging cycles. It is anticipated that the Project will not result in the creation of a significant amount of waste once constructed.

 

Will this Project only produce energy during the daytime? Does the battery work well with the solar?

A battery energy storage system can help balance the load on the power grid and deliver electricity to customers when it is most needed. Phase II of the Duane Arnold Solar Project is proposed to include 150 MW of solar generation and 75 MW of battery storage, allowing the Project to inject power into the bulk electric grid during both daytime and nighttime hours. Specifically, the solar arrays charge the batteries with excess power not injected into the bulk electric grid. This power is stored by the batteries for later injection into the electric grid during times of lower solar generation (e.g., non-daylight hours). Once fully charged a battery can inject power for 4 hours.

 

How many jobs (short and long term) will be created by this Project and what’s the impact in taxes (state/local)?

During construction, approximately 100 jobs will be available for each phase of the Project with two to three full-time equivalent jobs once the Project is in operation. Local businesses will experience an increase in revenue because the construction workers will require places to eat, sleep, buy food and gas, and obtain other day-to-day amenities.

Duane Arnold Solar – Phase I is anticipated to contribute up to $1.78 million in property taxes alone for all taxing districts over the life of the Project. Phase II of the Project is expected to contribute up to $5.42 million in property taxes over the life of the Project.

According to an economic impact study conducted by Strategic Economic Research, the two projects will have a combined positive economic impact of up to $260 million on the State of Iowa (including up to $154 million in Linn County). That includes the cumulative ripple effects of new jobs, wages, tax revenue and other economic activity during construction and over the estimated 30-year life of the projects.

 

Will the construction jobs be hired locally?

Duane Arnold Solar will retain an Engineering, Procurement and Construction (“EPC”) contractor to construct the Project. Typically, it is the EPC contractor that hires workers to construct a proposed project. However, our goal is to hire as many workers as possible from the local areas where we construct our solar projects.

 

Does your company intend to build utility-scale solar projects in other areas of the state?

NextEra Energy Resources has invested more than two billion dollars in the state of Iowa, including 10 operational wind projects and a repair and training facility. We continue to look for opportunities to invest in good projects that also create economic opportunities for the state and communities that host them.

 

Will the Project have a negative impact on property values?

No. Based upon Market Impact Analyses conducted for both Phase I and II, the Project will not have a negative impact on either rural residential or agricultural property values in the surrounding area.

 

Will the Project be built to withstand severe weather?

Duane Arnold Solar will design and construct the Project to withstand various extreme weather events, including high winds, flooding, hail, and accumulating winter precipitation. The Project will meet the site-specific wind load requirements of both the International Building Code (IBC) Section 1609 and the American Society of Civil Engineers (ASCE) 7-10 or 7-16, as applicable. Consistent with applicable requirements, the Project facilities, including the racking system and the tracker supports that attach the PV modules to the racking system, will be designed in accordance with Risk Category I - ASCE 7-10 or 7-16, as applicable. To provide decades of corrosion-free operation, solar cells are encapsulated from air and moisture between two layers of plastic, with a layer of tempered glass and a polymer sheet or industrial laminate. In the same way a windshield cracks but does not shatter when broken, a damaged solar cell does not generally create small pieces of debris.

 

How will stormwater be controlled at the Project Site during both construction and operation?

The Project will be designed to manage any permanent changes in stormwater runoff resulting from development of the Project and Duane Arnold Solar will be required to obtain authorization under the Iowa Department of Natural Resources (“IDNR”) General Permit to Discharge under an Iowa Pollutant Discharge Elimination System IPEDS Permit (“IDNR Stormwater General Permit”) prior to the commencement of construction. Temporary stormwater best management practices (“BMPs”) will be used during Project construction, and construction will be completed in accordance with the IDNR Stormwater General Permit and project-specific Erosion Control and Storm Water Management Plans. The temporary BMPs minimize potential soil erosion through a combination of erosion and stabilization practices, which minimize causes of erosion and the spread of sediment off-site.

Moreover, the Project Site, including areas beneath and around arrays, will be planted with perennial vegetation. This will manage erosion by increasing stormwater infiltration. Stormwater infiltrates soil at a higher rate on vegetative ground cover than on cultivated cropland. As such, the change to perennial vegetation will manage additional runoff resulting from the solar modules and access roads.

Once constructed, permanent stormwater facilities and perennial vegetation will be managed in accordance with the IDNR stormwater permits applicable to the Project. In contrast to agriculture, the Project will not require regular ground disturbance once the Project is constructed and vegetation is established. Thus, adverse impacts to water quality are unlikely to occur as a result of erosion or stormwater runoff from development and operation of the Project.

 

Will the Project have an undue adverse impact to wildlife?

No. The Project will work in harmony with the environment. It will not impact recreation on neighboring lands and is designed to minimize any impact to local wildlife. In fact, of all forms of energy generation, solar energy has among the lowest impacts as it emits no air or water pollution, emits little sound and creates no hazardous waste. Moreover, because the arrays will be individually fenced, wildlife connectivity is not anticipated to be unduly impacted.

 

Will the Project produce significant noise?

No. Sound studies were conducted for both Phase I and II of the Project. The results of the Sound studies demonstrate that sound levels will be typical of a rural environment.

 

Will the Project require any unique municipal services?

No. The Project will be installed to conform to all applicable electrical and fire codes and will not require any unique fire, police, or rescue services. In addition, the Project operations team will meet with local responders to review the Project configuration and educate local responders about any potential assistance of emergency responders that may be required.

 

How will the Project be decommissioned?

At the end of the Project’s useful life, the Project owner will assess whether to cease operations and decommission the Project or to replace equipment and attempt to extend the life of the Project. If the decision is made to cease operations and decommission the Project, to the extent possible, project equipment will be reconditioned, resourced, and/or recycled. For example, solar panels typically consist of glass, polymer, aluminum, copper, and semiconductor materials that can be recovered and recycled at the end of their useful life. Any materials that cannot be recycled will be disposed of at approved disposal facilities. A Decommissioning Plan is included as an Exhibit to the Applications. To ensure that funds are available for decommissioning and restoration of the Project, the Project owner will provide security in the form of a surety bond, letter of credit, parent/corporate guarantee, or other financial instrument that is mutually acceptable to the County and the Project Owner.

 

Iowa Utilities Board Applications

View the full Iowa Utilities Board application for Duane Arnold Solar I.

View the full Iowa Utilities Board application for Duane Arnold Solar 2.

 

1 Linn County Ordinance Sec, 107-149

“NextEra Energy Resources and Alliant Energy agree to shorten the term of the Duane Arnold Energy Center power purchase agreement; Alliant Energy customers to save hundreds of millions of dollars,” July 27, 2018.