Physical Impacts of Grid-Scale Solar Development

Across Pennsylvania, especially in the southcentral and northwest parts of the state, we're seeing a surge in interest for GSSD.

Every year, solar panels get both less expensive and more efficient, so the cost of building grid-scale solar (GSS) is much less than what it was even a few years ago. Solar energy is typically reliable and becoming more affordable.

Penn State researchers recently analyzed all the 2,500+ zoning ordinances in Pennsylvania and found that only about 5% specifically allow principal-use solar (the generation of solar energy for use off-site). Eighty-seven percent of the municipal zoning ordinances in Pennsylvania include no guidance on solar energy generation, not even rooftop solar for individual homes.

Most municipalities in Pennsylvania don't have ordinance requirements for GSSD clearly laid out. This can generate additional work, cost, and delay for municipalities facing this form of energy development from solar energy companies. It's inefficient if municipal officials have to come up with new requirements on a case-by-case basis as GSS projects are proposed. With many municipal officials serving only part-time, the expected investment in solar could quickly overwhelm the current capacity to address project review.

Instead, it can be wise to specify the requirements for GSSD in the zoning ordinance and let the developer identify the most efficient way to meet the requirement, given the constraints of the site, or abandon the location and move to a different site. Having a clear ordinance saves money, time, and hassle for the township and the developer. Most importantly, officials should be careful to keep the burden on the developer to prove they are not causing additional burdens for a municipality or county as they consider the solar company's new GSS proposal.

This publication identifies the ways that GSSD affects a community and the landscape and suggests ways to address potential concerns.

After construction, a solar array is typically quiet as a new land use, with minimal traffic. GSSD may increase property taxes for the property owner, but doesn't increase the local school population, use much water, or generate wastewater, as many other types of land development can do.

Traffic Impact

So far, there has been little attention paid to Pennsylvania zoning ordinances and the road impacts of GSSD. There is general language about road impacts in many ordinances, but not specific to solar development.

During GSS site construction, there would be increased truck traffic to bring in materials, including semitrailers. During the construction phase of a new GSS project, there can be hundreds of workers there at the high point of panel installation and wiring. Depending on the scale of the project, this construction phase can last for months and create temporary traffic flow and parking issues that must to be planned for and managed.

Planning recommendations:

• Require that developers indicate which roads traffic for the project will use.
• Require projected traffic counts for the construction phase.
• Reserve the right to require a traffic study.
• Include notification of off-site work to a right-of-way and/or roadside powerline.
• Require notification of any new roads needed or proposed upgrades to roads.
• Require the developer to have surety bonds in place for roads before construction begins if road condition is an issue before the project starts.

During operation of the solar array, there would normally be no workers present, except for occasional maintenance or repair work.

Noise

The noise of an operating GSS array is not normally audible above background noise outside the system's fence. The inverters, which convert direct current (DC) from the panels into alternating current (AC) used by the electric grid, are the noisiest equipment unless there is battery storage on-site. Inverters make a low buzzing noise of about 55 decibels. Transformer noise differs depending on the voltage involved and the type of cooling system used, but the average is also about 55 decibels. The motors that move tracking panels also generate some noise when the panels are in motion, often once every 10 minutes or so. Any noise from equipment on-site typically fades to background levels 50-150 feet from the site.

Most new solar projects will have electricity storage facilities. These are typically, but not always, placed within the solar array, rather than at the edge, because of equipment noise, commonly from cooling fans. Municipal officials should be aware that in the future, solar companies may want to install energy storage technologies at existing solar arrays. This could require additional land and setback allowances to accommodate noise.

Planning recommendations:

• Consider siting inverters, transformers, and battery storage near the middle of the array to the extent possible.
• Consider reserving open space near the middle of the array to accommodate future addition of electricity storage equipment.
• Consider a noise study done by the solar developer.
• Have a protocol to measure noise internal and external to the site. Determine who will take measurements, where tests will be done, and who will cover the cost.

Performance Standard More Flexible than Prescriptive Requirements

A performance standard states a general requirement that a developer has to meet, but allows the developer to implement a solution that makes the most sense for the site. An alternative to a performance standard is a prescriptive requirement outlining exactly how a developer must address a particular concern. Developers often seek variances for prescriptive requirements if they see a more cost-efficient way to meet the requirement. Having clear performance standards generally results in greater cost- and time-efficiency for both developers and municipal planners.

Glare

Local residents may wonder if a solar array will produce noticeable glare, possibly endangering drivers on nearby roads. Potential neighbors may wonder if an array will reflect light back into their property or irritate local livestock.

Solar panels generate power by absorbing light, not reflecting it. They are generally less reflective than windows. Solar companies don't want glare, because it's an inefficient loss of energy.

Some environmental and aviation consulting firms apply the U.S. Federal Aviation Administration's glint and glare standards to perform a glint and glare study and determine the potential for temporary after-image glare or permanent eye damage glare from a proposed solar development on neighboring land users. Such a study maps the glare minutes per year based on different important points on the landscape (for example, different runways at an airport, single- and two-story homes nearby, and cars and trucks on specific roads).

Glint and glare studies normally find that there's little glare or reflection risk. If issues are identified, the developer could adjust the placement and/or angles of the panels to lessen glare.

Requiring a glint and glare study and adjustment of the project as needed given the results of the study is a performance standard that provides an effective way for the developer to satisfy potential concerns about glare. A glare study tends to be more effective than a prescriptive system to "eliminate" glare, such as fencing, especially in hilly terrain where some points will be above the fence line.

Planning recommendation:

• Consider requesting that solar developers do a glint and glare study to identify any potential adverse impacts on neighboring land use. If significant impacts are found, require the developer to adjust the project plans as needed to reduce or eliminate the issue.

Viewshed

Some people may be concerned about neighboring property values and where the panels will be visible. An ordinance can require the developer to submit a GIS study showing the viewshed of the proposed array and offer screening or alternative placement or orientation to address concerns. Some communities require visual screening with earthen berms, vegetation, or fencing to minimize this potential issue. Plastic inserts in fences or windscreens attached to fences are sometimes used to reduce visual impacts. Additional setbacks from roads are another tool some municipalities and counties use to reduce impacts to viewsheds.

Planning recommendations:

• Require the developer to conduct a GIS viewshed analysis for the proposed array and adjust screening, placement, or orientation to address concerns.
• Allow latitude with zoning officer to determine amount of vegetative buffering needed to screen the proposed solar facility from nearby roads and residential/light commercial development.

Screening

Many people don't want to see solar panels. Some municipal and county governments have requirements for screening. A line of trees, an earth berm, and/or fencing may block the view, especially along the road. When vegetative screening is used, there often is language in ordinances requiring replacement should trees be destroyed or die.

Some ordinances are prescriptive, even specifying the type of trees and height and density for screening. Instead of this strict prescriptive approach, it can be better to require the developer to propose a screening plan that accounts for the realities of the location as long it does the job of screening the site. Screening can be adjusted based on the proximity and type of neighboring land uses and roads. Sometimes screening may be unnecessary if the site is not near residential buildings or next to a public road.

Some new ordinances encourage or incentivize pollinator-friendly vegetation for buffer/screening areas.

Planning recommendations:

• Require the developer to propose a screening plan that accounts for the realities of the location and effectively screens the site.
• Screening is normally accomplished through a mix of evergreen and deciduous trees and may be done in conjunction with fencing. Other sections of existing ordinance language may cover similar scenarios with other types of light commercial development within the municipality/county. Consider modifications to screening option, adjusting for the unique characteristics of GSS, particularly the lot size of the overall development and height of the panels.

Fencing

A GSSD is essentially a power plant, so people and animals should be excluded. There are electrical connections above and below ground. Fencing of the site perimeter is typically required, and fence height and type are often specified in a zoning ordinance. Commonly this is 7- or 8-foot-high chain link fence, sometimes with barbed wire on top. Appropriate hazard signs as required by the National Electric Code should be posted on the fencing warning of the electrical hazard inside.

The specific site plan can influence the type of fencing that makes the most sense. Where sheep will graze the vegetation inside the solar site, the developer may want to use high-tensile livestock fencing. At some sites, there may be a desire to use wildlife-friendly fencing that lets some small wildlife pass through the site.

The amount of setback of the panels from the fence, and of the fence from the property line, should be indicated in the lease or included in a township ordinance. This should allow for operation and maintenance workers to perform their tasks and emergency management personnel to access the site and turn around at the fence line as needed.

Planning recommendation:

• Require a perimeter fence of the entire solar array and related equipment, with sufficient setback from the panels to allow for needed maintenance and emergency access.

Setbacks

Many zoning ordinances adopt the same general setback rules for GSS, no matter the size, as for other similar uses. The ordinance may say that the GSSD must comply with the setbacks of the underlying zoning district for principal structures. Other times, special conditions created by GSSD are considered in this type of energy development and new setback requirements are proposed.

Another option is to propose a minimum distance from adjacent residential districts or structures. The setback of panels typically ranges from 20 to 300 feet from the property line of neighboring actively used parcels and can be determined as part of the ordinance development process. Front setbacks from roadways vary as well, and some municipalities and counties are making them more stringent as a way of preserving the character of the surrounding zoning district.

The site layout and setbacks must allow for emergency response access in case a worker is injured on-site or in case of fire.

Planning recommendations:

• Require compliance with the underlying zoning districts for principal structures.
• Alternatively or additionally, require setback of a certain distance from adjacent residential districts and structures.

Height Requirements

Many zoning ordinances set maximum height requirements for GSS panels. Planners should consider the concerns they hear from residents when developing the height requirement. A maximum of 10-20 feet high for ground-mounted GSS is common. Height requirements can be influenced by topography—whether the parcel is on a hilltop, a hollow, or a flat.

Planning recommendation:

• Set a maximum height for ground-mounted solar panels. The optimal height will vary by site, but the maximum cannot be exceeded.

Lot/Parcel Size

Proposed GSS facilities in Pennsylvania are commonly 100 acres or more, with most ranging from 500 to 1,000+ acres. Larger-sized solar facilities are more economical for energy companies to construct and operate over time. If multiple projects can be built as one facility, it requires fewer access points into the electrical transmission grid for the same number of megawatts of electricity produced. Accordingly, solar companies are commonly looking at sites that might allow their projects to cross property lines to "scale up" the proposed solar facility.

Existing zoning regulations often make a de facto prohibition on GSSD. Some ordinances have a minimum lot size for GSS of 100 acres, or only 50% of the parcel developed in GSS. In other cases, this delineation might be for a percentage of the prime soils that may exist on the site. The average farm size in Pennsylvania is ~120 acres, so only a small number of farms could meet this condition. The average parcel size of forested lands in the state is even smaller. Most Pennsylvania GSS projects to date have been done on pooled land owned by more than one landowner.

Some regulations also specify a maximum area to be occupied by solar panels. Some are as low as 10 acres. Developers lose the capacity for scale with such a requirement, and the municipality signals to developers that they don't want big projects.

These types of restrictions are giving rise to lawsuits as unconstitutional or a taking of land, so care should be taken to ensure that they are able to withstand legal challenge and meet Pennsylvania's Municipal Planning Code.

Planning recommendation:

• All considerations of minimum lot sizes for GSS or percentage of parcel allowed for GSS development must meet Pennsylvania Municipalities Planning Code requirements.

Lighting

Neighbors may be concerned that a GSSD will have a lot of lights on overnight. This would diminish dark skies for star gazing or could disrupt sleep. Solar arrays typically only light up the area around transformers, not all the panels. These lights can be on motion activation to reduce impact to dark sky areas. Municipalities may also require GSS facilities to have downward-pointing lights that don't illuminate the night sky.

Planning recommendation:

• Require dark-sky-protective lighting through the use of motion-activated and/or downward-pointing lights around equipment as needed.

Fire Safety and First Responder Safety

Some people wonder about the possibility of fires at solar arrays. Most of the materials in panels are not flammable, and the small amount that is can't support a significant fire. The flammable parts include the polymer (plastic) outer layers, other plastic parts, and the wiring insulation. Heat from a small flame cannot ignite a solar panel. For example, a wildfire in grass beneath a 3-acre array in California did not ignite the panels mounted on fixed-tilt racks just above the grass.

Firefighters don't need special equipment to fight fire at a GSSD, but they do need specialized training. The fire department must be made aware of the array, and firefighters must know how to de-electrify the site. The National Electric Code includes requirements that make it easier for first responders to safely and effectively turn off a solar energy system. Numerous groups, including the International Association of Fire Fighters, have developed relevant training materials.

Conclusion

Having GSS specifications outlined up front tells developers the critical criteria they need in initial site selection, so they know what to expect in construction. Ideally, zoning ordinances have answered the question of how a communities want to build GSS before developers propose construction.

Wider examination of solar development in other states such as North Carolina and Minnesota reveals that townships with overly prescriptive regulations are often inundated with variance requests. Analysis of many zoning ordinances suggests that starting the process of regulating GSSD by thinking about what problems GSS creates on the landscape and addressing those issues is efficient for both county and municipal officials and solar developers. Using flexible performance standards that put the onus of proof on the developer to propose a workable solution that is efficient for them can minimize extra work for township officials.

For More Information

Comments for Joint Hearing of the Agriculture and Rural Affairs & Local Government Committees on "Utility Scale Solar Development & Local Government Ordinances." Prof. M. Badissy, Penn State Dickinson Law. 2021.

Federal Aviation Administration (FAA) Policy: Review of Solar Energy System Projects on Federally-Obligated Airports. 2021.

National Electrical Code. National Fire Protection Association. 2020.

New York Solar Guidebook for Local Governments. NYSERDA. 2020.

An Overview of Sound from Commercial Photovoltaic Facilities. RSG, Inc. NOISE-CON 2020.

PA Solar Ordinances: Local Regulation and National Trends. Penn State Solar Law Symposium. 2021.

Top Five Large-Scale Solar Myths. National Renewable Energy Laboratory. 2016.

Utility-Scale Solar Development. Penn State Extension webinar. June 2020.

Utility-Scale Solar and Siting Considerations: Stormwater, Vegetation, Fencing, and Ag Use. Penn State Extension webinar. April 27, 2021.

Notes

"Penn State researchers recently analyzed all the 2,500+ zoning ordinances in Pennsylvania" (in Introduction)

Source: Comments for Joint Hearing of the Agriculture and Rural Affairs & Local Government Committees on "Utility Scale Solar Development & Local Government Ordinances." Prof. M. Badissy, Dickinson Law, Penn State University. 2021.

Inverters are the noisiest equipment. (in Noise)

Source: Top Five Large-Scale Solar Myths. National Renewable Energy Laboratory, 2016.

Inverter decibel value (in Noise)

Source: An Overview of Sound from Commercial Photovoltaic Facilities. Kaliski, K., I. Old, and E. Duncan. 2020. RSG, Inc. Presented at NOISE-CON 2020.

Transformer decibel value (in Noise)

Source: NEMA Standards Publication TR 1-2013 (R2019). National Electrical Manufacturers Association, p. 4.

"Any noise for equipment on-site typically fades to background levels 50-150 feet from the site." (in Noise)

Source: New York Solar Guidebook for Local Governments. NYSERDA. 2020.

"The setback of panels typically ranges from 20 to 300 feet from the property line of neighboring actively used parcels." (in Setbacks)

Source: PA Solar Ordinances: Local Regulation and National Trends. Mohamed Badissy, Penn State. Penn State Solar Law Symposium, June 17, 2021.

"A maximum of 10-20 feet high for ground-mounted GSS is common." (in Height Requirements)

Source: Local Law for Solar Project Development in Pennsylvania. Badissy, M. Feb. 17, 2022. Mercer County planners' webinar. Penn State Extension.

Fire safety and first responder safety (in Fire Safety and First Responder Safety)

Source: Health and Safety Impacts of Solar Photovoltaics. 2017. North Carolina Clean Energy Technology Center. North Carolina State University.

Renewable Energy Ordinance Framework, Solar PV Delaware Valley Regional Planning Commission. 2016.

Disclaimer and Funding

By Thomas B. Murphy, Director, Penn State Marcellus Center for Outreach and Research, and Joy R. Drohan, Eco-Write, LLC.

This material is based upon work supported by the United States Department of Energy, Office of Energy Efficiency and Renewable Energy, under State Energy Program Award Number DE‑EE0008293.

This material was prepared with support and funding of the Pennsylvania Department of Environmental Protection (DEP) and the US Department of Energy's (DOE) State Energy Program. Any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the DEP or DOE. This report was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.

Additional support provided by the Penn State College of Agricultural Sciences, the Penn State Marcellus Center for Outreach and Research, and the Penn State College of Earth & Mineral Sciences.