The NIMBY arguments against solar and storage range from the insane (solar panels suck up all the energy from the sun!) to the indisputable (projects alter rural landscapes). Regardless of the opinion, it’s the priority of the solar + storage developer to hear community concerns and find solutions. One logical issue community members may have with large-scale battery energy storage systems (BESS), especially as more are being installed in urban areas, is their noise level. Residents will be living and working near these systems long after the project developer moves on to the next site.
It’s a valid concern, said Thomas Corbishley, principal consultant for acoustic consulting company Noise Monitoring Services.
Lithium batteries at the Moss Landing Energy Storage Facility in California, showing their inner workings. Credit: Vistra
“Sites using the loudest equipment can generate noise levels of 70 dBA at 50 ft from the batteries. This level is well above typical permissible sound levels for residential areas,” he said. “For a comparison, freeway noise is typically 70 to 80 dBA at the same distance. However, roadway noise is less intrusive as it is broadband in nature — [meaning that] road noise is not tonal like BESS equipment can be.”
The “noisiest” components of a BESS are typically the cooling systems, inverters and transformers. A BESS’s cooling and ventilation system includes noise-making fans and pumps, which operate frequently. Solar installers are familiar with inverter noise, which is more of a consistent buzz that can be noisier on a larger installation. Transformers also create a low-frequency hum that is still notable.
“For large shipping container-sized batteries, we’ve measured noise levels up to 92 dBA at 1 meter from the fans,” Corbishley said. “The fans often produce a humming sound. This type of tonal noise can be very intrusive and annoying to people.”
But there are ways these energy storing noise-makers can be designed to limit their acoustic annoyances, both during manufacturing and project siting. The earlier noise mitigation steps are taken, the more acceptable a BESS will be to a community.
A battery is only as noisy as its parts
Sharon Santhosh, application engineer at global BESS integrator and designer Wärtsilä Energy Storage, said questions around battery noise have increased in recent years.
Credit: Wärtsilä
“Five years ago, acoustic studies were occasional; now, nearly every project includes noise criteria,” she said. “Local authorities and nearby residents are becoming more aware of operational noise and its effect on quality-of-life and community wellbeing, so noise is now a limiting factor for permitting and community acceptance. We see stricter thresholds, especially for nighttime, often 30-40 dBA at the nearest home and 70-90 dBA at the unit, which makes early-stage noise modeling essential.”
BESS are typically at their loudest at night, when batteries are actively working and cycling. This is the opposite of when other ambient noise sources like road traffic are at their loudest levels, which can add to their nuisance.
Since Wärtsilä has some control over the manufacturing of its Quantum energy storage systems, the company can customize acoustic performance to meet project requirements. For example, enclosures can be designed to use high-quality wall materials and properly sealed access points to prevent sound leaks. Santhosh said the company can also incorporate noise silencer kits and anti-vibration materials and pads between the base and equipment to stop mechanical noise transfer. Wärtsilä’s GEMS optimization software can adjust fan speeds depending on system needs that can assist with noise levels at different times of the day.
Corbishley with Noise Monitoring Services said these small tweaks can do a lot to help with noise pollution.
Noise Monitoring Services measuring noise levels at a BESS site.
“We’ve performed tests that demonstrate running the battery fans at 70% of their standard operating speed reduces sound levels by 4 or 5 dBA — a noticeable reduction,” he said. “At one site we worked on, the fan speed could be reduced to 50%. This typically reduces sound levels by 10 to 13 dBA, which is a very significant reduction.”
The type of BESS used can also influence noise levels. The transition to liquid-cooled systems allows for fewer fans, which diminishes some noise. The time-duration of a system also determines noise levels, said Martin Rheault, VP of business development and sales for North American BESS integrator EVLO Energy Storage.
“The use-case of a specific BESS project also plays a role — whether the system delivers lower power over a long period (four or eight hours) or higher power over a shorter timeframe will influence cooling needs and its noise levels,” he said. “The more power, the more cooling required, the greater the sound output.”
Rheault said the trend toward longer-duration energy storage (systems operating at more than eight-hour intervals) will decrease noise levels too.
“These systems typically operate at lower power output over extended periods, which reduces the need for intensive cooling by HVAC equipment, and therefore results in lower acoustic impact of those energy storage projects,” he said.
Being a courteous neighbor
EVLO has found noise requirements to be just one community factor increasing on BESS siting — along with fire safety, property value impacts and wildlife considerations.
EVLO systems installed in Vermont.
“Responsibility for minimizing these impacts is shared between the BESS provider and the project owner,” Rheault said. “While the provider integrates these considerations into system design, the project owner can also plan for optimal site selection and mitigation strategies. Together, this ensures that energy storage remains a solution with minimal footprint on surrounding communities, while optimizing the benefits of BESS as flexible energy assets.”
Murray Stacy, VP of Sound Fighter Systems, a provider of outdoor sound-absorbing products used in industrial and commercial settings, said his company has been called to more BESS sites lately. Its SonaGuard system is designed for maximum acoustical performance and long-term outdoor exposure and works great at mitigating BESS site noise. Instead of treating source-specific noises at a battery project, the SonaGuard absorbs sound from all areas.
“Many people’s first exposure to sound walls has been with highway sound walls, which were traditionally sound-reflective concrete, but have now progressed to the more advanced sound wall components found in products like our SonaGuard barrier system,” Stacy said. “The SonaGuard sound panels are tuned to mitigate the most common frequencies associated with the noise sources on BESS sites, in addition to many other outdoor noise sources such as electrical substations, power generation and data centers.”
The consultants at Noise Monitoring Services have conducted surveys at many existing BESS projects primarily in California and Arizona. When changes can’t be made to the manufactured product itself, Corbishley said the most common noise mitigation options his company suggests is installing sound walls like Sound Fighter Systems’ SonaGuard. Re-orienting equipment to direct sound away from the nearest residences can also make a big difference. HVAC systems are typically only on one side of a BESS, so they can be oriented away from nearby housing. Additionally, increasing space between battery units and sensitive areas can reduce perceived sound.
An example of noise mitigation efforts from Noise Monitoring Services.
“While the biggest gains come from mitigating noise at the source, installation and site layout are crucial parts of acoustic mitigation,” said Santhosh with Wärtsilä. “Mechanical isolation between the unit and its foundation can prevent vibration from amplifying noise. Orientation also matters by facing inverters or ventilation outlets away from nearby receptors and spacing containers to allow for sound dissipation; overall noise exposure can be reduced significantly.”
As more BESS projects are installed across the country and in more urban setups, Stacy with Sound Fighter Systems said acknowledgement of community concerns will go a long way.
“Transparency, empathy and community buy-in from the start is a prudent strategy,” he said. “Too often, noise is an afterthought without any budgetary considerations, then site owners try to Band-Aid the problems with the cheapest treatments possible. Such remedies seldom resolve the noise issue and often agitate the community due to the owner’s perceived lack of empathy, lack of knowledge or both.
“Instead, deploy aggressive and progressive pre-emptive noise mitigation tools, and share with the community that you are proactively utilizing the best technology available on their behalf,” Stacy continued.
Noise levels should be considered at every step of BESS deployment — initial manufacturing, project design and long-term operations.
“Designing for low noise isn’t just about compliance; it’s about building community trust and ensuring energy storage remains a welcomed, long-term part of the local environment,” Santhosh said.
