Falmouth Solar Farm Noise Study

Falmouth is developing a large-scale ground-mounted solar array, which consists of three large solar projects on the former Cape Cod Country Club site, approved by the town meeting vote, transforming 137 acres into 45,000 solar panels.

The project has significant battery storage and multiple inverters/transformers. Transformers focus on magnetic induction with a core, windings, oil, tank, and cooling fans. Inverters (DC to AC) use power electronics like microcontrollers, MOSFETs/BJTs, capacitors, filters, and an H-bridge to create the AC signal.

A noise study for a solar (PV) field in Massachusetts is typically required as part of the local permitting process to ensure compliance with the state's noise regulations. Inverters and transformers make noise.

Massachusetts Department of Environmental Protection (MassDEP) noise regulation (310 CMR 7.10: Noise) and associated policy. The regulation states that a new noise source should not cause "unnecessary emissions" that could lead to noise.

The sound levels following the installation of the new noise source, aka the solar project, should not exceed the existing ambient background noise (L90) at the property line by more than 10 dBA (A-weighted decibels).In most cases, a "pure tone" condition is also prohibited. Local noise bylaws may apply.

In 2010 and 2012, the Town of Falmouth, after being warned that the town-owned wind turbines could produce 110 decibels of noise, installed the project. The turbines were removed due to noise in 2022. (see note 1) link

A noise study for a proposed solar project typically requires:
1. Baseline Ambient Sound Survey: An acoustic engineering firm conducts measurements at the site and nearby noise-sensitive areas to determine the existing background sound levels (L90) during different periods day, evening, night, winter, and summer heat

2. Noise Modeling: contractors use the manufacturer's specifications for all the solar equipment, which includes multiple inverters and transformers, to predict the sound levels at the property lines of abutters.

3. Impact Assessment: The predicted sound levels are compared against the established ambient levels plus the 10 dBA limit to determine if the project will comply.

4. Reporting: A formal report should be submitted to the planning board or final permitting authority. (Zoning Board)

The primary source of noise is the combination of all three solar fields, which include converting the direct current (DC) produced by the panels into alternating current (AC) for the grid, and associated transformers. Inverters and transformers give off a continuous humming sound during the day when the system is operational, and higher during hot summer days.

Note 1 - Wind turbine noise warning link: https://www.windaction.org/posts/41357-vestas-raises-concerns-about-turbine-noise-letter#.Ve9oyhFVikp