01. Overview

Ethan Brush, a technical expert from the noise and acoustics services company Acentech, recently released a study highlighting the increasing concern over noise issues associated with battery energy storage systems (BESS). As land becomes more scarce, these systems are increasingly deployed in densely populated residential areas, making noise control a critical consideration.

The proliferation of BESS installations in densely populated areas, driven by land scarcity, has made noise management an increasingly important issue. This concern is particularly acute in densely populated regions of Europe and is also growing in the United States and Australia. To address this challenge, BESS manufacturers must prioritize acoustic design to meet the needs of residential environments.

02. Sources of Noise

Cooling Systems

Like other electronic equipment, BESS operates most efficiently and safely within specific temperature and humidity ranges. To maintain these conditions, various air or liquid cooling systems are used, which often generate continuous noise from vents, fans, and pumps.

Power Conversion Systems (PCS)

The PCS in BESS is responsible for converting DC power from the battery to AC power for use, and vice versa during charging, using inverters. This conversion process generates heat, requiring cooling, typically by fans, which inevitably produce noise.

The DC-to-AC conversion involves high-speed switching to change polarity (or current direction). In the U.S., where AC power operates at 60Hz, this switching occurs twice per second, producing a sound at double the power frequency (120Hz) and other harmonics (such as 240Hz, 360Hz, 480Hz, and higher frequencies).

In regions where AC power operates at 50Hz, the harmonics differ slightly (100Hz, 200Hz, 300Hz, 400Hz), often resulting in a noticeable buzzing sound, particularly in environments with low background noise.

Transformers within BESS contribute to noise through core noise, coil noise, and fan noise. Core and coil noise are magnetically induced, similar to inverters, producing sounds at 120Hz or 100Hz and their harmonics. External cooling fans also generate noise, though some transformers use radiators instead, which is a quieter option.

03. Mitigation Measures

Understanding Noise Standards

Globally, countries and regions generally have specific noise regulations to limit industrial facility noise impact on residential areas. The detail and specificity of these regulations vary; some set precise noise emission standards and conditions, while others only set decibel limits.

In some areas, regulations specifically addressing BESS noise may not yet exist. Nonetheless, BESS developers should consider the environmental impact and potential negative reactions from residents, even if laws do not explicitly mandate noise reduction.

For instance, the National Electrical Manufacturers Association (NEMA) in the U.S. specifies noise levels for electrical equipment when achieving a NEMA rating.

Additionally, the International Electrotechnical Commission (IEC) and the Institute of Electrical and Electronics Engineers (IEEE) Standards Association set standards for sound emissions from various electrical devices. Similarly, organizations such as the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the American National Standards Institute (ANSI), and the International Organization for Standardization (ISO) provide standards related to refrigeration systems.

These standards not only provide guidelines for the energy storage industry but can also be used alongside actual sound measurements from BESS to comprehensively assess and manage noise levels.

Acoustic Modeling of BESS

During the design phase of BESS, acoustic consultants and technical experts need to accurately identify and characterize major noise sources from various equipment. Equipment suppliers may provide detailed noise emission data for their products. Utilizing this data to create acoustic models can simulate the noise levels generated by BESS in surrounding environments, such as residential areas.

These acoustic models include noise sources from various BESS components and consider the characteristics of the surrounding terrain. The final model evaluation results are compared with applicable noise limit standards for the project.

Not all BESS equipment manufacturers provide noise data for their products. BESS often includes components from multiple suppliers, making it challenging to accurately model the system's overall noise level without complete information.

Measuring Environmental Sound Levels

Many noise regulations (such as those from the Massachusetts Department of Environmental Protection) require that industrial facility noise levels not exceed specific thresholds based on environmental conditions. These ambient sound levels must be determined before the installation of industrial facilities or when the facilities are completely shut down.

Typically, ambient sound is measured over a week or more in relatively quiet weather conditions to obtain a comprehensive characterization of the site's sound environment. Noise limits are set lower in quiet areas than in noisy ones, reflecting the existing environmental conditions.

Other regions' noise regulations may set a fixed upper limit on the noise produced by BESS, which may not require on-site verification. However, it is generally recommended to use ambient noise measurements to correlate modeling results with the existing environmental scenario.

04. Noise Control

Noise control in BESS is an ongoing process. If the design and layout of noise-generating equipment exceed the noise limits for the project, acoustic consultants must design new solutions to reduce noise levels. By considering the source-path-receiver model, effective methods can be found to address noise issues.

BESS operators can incorporate various mitigation measures into the facility and surrounding area's acoustic models. Effective noise control is only achieved when the predicted noise levels meet the relevant standards for BESS.

After installing a BESS, sound levels must be measured to verify compliance with site-specific noise standards. This is typically done at night when ambient noise is lowest, and all BESS equipment may need to be turned on and off over time to fully assess the overall noise characteristics.

Using Sound Level Meters to Measure Noise in Photovoltaic Systems

Equipment used to measure ambient sound must meet international standards for measurement equipment accuracy. These devices are classified based on precision and performance criteria.