Frequently asked questions

Company

Who is Clearway Energy?

Clearway Energy Group’s vision is a world powered by clean energy. Along with our public affiliate Clearway Energy, Inc., our portfolio comprises approximately 11.8 GW of gross generating capacity in 26 states, including 9.1 GW of wind, solar, and battery energy storage assets, and over 2.8 GW of flexible dispatchable power generation providing critical grid reliability services. As we develop a nationwide pipeline of new energy projects for the future, Clearway’s operating fleet generates enough reliable electricity to power more than 2 million homes today. Clearway Energy Group is headquartered in San Francisco with offices in Denver, Houston, Phoenix, Princeton, and San Diego. For more information visit clearwayenergygroup.com.

What is Clearway's energy storage track record?

Clearway has deployed 27 battery storage systems capable of storing 2.9 GWh of electricity across the U.S., from distribution-level solar and storage hybrid projects in Massachusetts to utility-scale storage systems in California and Hawaii. Each system’s design and operational plan undergoes thorough review and approval by local permitting authorities, fire departments, and independent third-party engineers.

Who is paying for the project?

Clearway Energy projects are entirely privately funded, bringing new investment into the communities where they are located.

No tax dollars go into building Clearway energy projects. Instead, the community gains new revenue through any local property, sales, or income taxes that the projects pay. This grows the budget for schools, first responders and other public services without increasing taxes for residents.

Planning & Design

How are energy storage projects planned and sited?

Battery energy storage projects go through a rigorous planning and siting evaluation before a local permit application is ever formed. Once an agreement is signed with a local landowner, project developers begin conducting a suite of surveys and investigations to determine whether the property can host a project. Surveys like wetland delineations, habitat surveys, cultural resource survey and species-specific surveys help to inform the potential impacts and guide the responsible siting of an energy storage system.

How are facilities designed for long-term safety?

Battery modules are housed in individual metallic enclosures, and each enclosure is equipped with temperature conditioning to maintain the inside temperature within an optimum range. The individual battery cells and modules are also designed with thermal management systems, including ventilation, heating, and cooling equipment to maintain safe operating temperatures.

All projects are equipped with sensors that track battery and enclosure temperatures. The operator is alerted if abnormal conditions are detected. In case of critical failures, local EMS responders will isolate the enclosure from the rest of the system. The modular nature of project design keeps thermal events contained.

All battery storage projects must meet rigorous codes and standards before being permitted to operate. Cells, modules, and racks are tested for UL 9540A compliance. Clearway’s battery suppliers must adhere to rigorous codes and standards, industry best practices, and quality and performance guarantees.

What technology does Clearway use at energy storage facilities?

Lithium-ion based batteries are the dominant technology in today's market due to their higher energy density, higher capacity, smaller footprint, reduced degradation over time and lower environmental impact compared to other kinds of batteries. Clearway's storage projects exclusively use a variety called Lithium Iron Phosphate (LFP) battery cells, which have enhanced reliability and safety features which significantly reduce risks at every step.

All technology used in energy storage projects must meet rigorous codes and standards to be permitted to operate. Cells, modules and racks are all tested for UL 9540A compliance.

Operations & Safety

How does Clearway ensure their battery energy systems are built and operated safely?

Every energy storage project is required to comply with national fire protection standards, which are frequently updated to incorporate the best practices for hazard mitigation tools and strategies. All technology used in energy storage projects must meet rigorous codes and standards to be permitted to operate. Cells, modules and racks are all tested for UL 9540A compliance.

Multiple layers of operating parameters and restrictions, such as acceptable operating temperature range, number of operating cycles, and down time between cycles, are established to ensure battery projects operate in a safe operating range with high safety margins.

Even though these facilities are expected to operate safely for their lifetimes, emergency response planning is crucial to prepare for the rare event of an operational emergency. Clearway coordinates with local officials, including fire departments, to provide training at battery storage projects.24/7 monitoring allows for immediate response in case any abnormality arises. The key steps and considerations for our emergency response plan include risk assessment, regulatory compliance, emergency response plan designs, emergency service training, and continuous improvement.

How are energy storage systems monitored?

Continuous monitoring by a 24/7 dispatch center allows for rapid intervention in case of operational issues.

Battery energy storage systems are equipped with sensors that track battery temperatures and enable storage facilities to turn off batteries if they get too hot or too cold. Battery management systems also monitor the performance of each individual cell voltage and other key parameters the aggregate that data in real time to assess the entire system's operation, detect anomalies, and adjust the system to maintain safety. Battery management systems often contain state of the art software designed to safely operate and monitor energy storage systems

How often do battery energy storage systems have fires?

While fires can occur, they are relatively rare events. Recent data compiled by EPRI shows that while cumulative deployment is continuing to increase, the rate of failures (per deployed gigawatt) have continued to decrease. The failure rate has decreased, a factor of almost 10x from 2018 through 2023. This decrease indicates that product quality, operations, and safety are all improving.

Are battery storage systems built to withstand extreme weather events?

Battery energy storage facilities are designed to endure severe weather, while also enhancing grid resilience against weather conditions, averting blackouts, and delivering back-up power.

Local Impacts

Do batteries produce noise?

Batteries alone do not make any noise. Unlike some other power infrastructure or generation facilities, energy storage systems have very low noise profiles, with fans, HVAC systems, and transformers producing sounds at similar levels to standard commercial buildings

Do batteries pollute the air or groundwater?

Battery storage systems do not release pollutants during normal operation. In the unlikely event of a fire, smoke and products of combustion may be released. Clearway performs risk analyses of each of its sites to demonstrate that in the unlikely event of a fire that the consequences will be appropriately mitigated.

The average toxicity level of fumes from a battery fire are similar to those from burning plastic-based household materials such as sofas, mattresses, or office furniture. This has been backed up by emissions and environmental data collected from recent events including those in NY and CA which showed that there were no contaminants in the air, soil, or water that exceeded any OSHA or environmental standards.

Do batteries give off electromagnetic radiation?

Like batteries used in handheld devices, lithium-ion and other types of batteries do not give off electromagnetic radiation. These batteries store electrical energy in chemical form, which can be converted back into electrical energy and discharged back to the grid. This conversion is performed by a bidirectional inverter, which must be tested and certified for electromagnetic compatibility.

Site Removal

What happens to the batteries when they reach the end of their lifetime?

The U.S. lithium-ion battery recycling industry is growing rapidly to accommodate batteries from both electric vehicles and energy storage systems. Companies are moving beyond simple recovery of raw materials and into direct recycling of electrode materials that can be built sustainably and cost-effectively into new batteries.

What is a battery energy storage system?

Why do we need energy storage?