Arcus Power

Battery Energy Storage Systems-The Eclipse-Proof Solution

By now, everyone knows the importance of renewable energy sources in our grid. We’ve seen many instances where renewable energy like wind and solar has helped maintain a stable grid. Particularly, the solar power industry in Texas has seen remarkable growth.


By last year, Texas had surpassed all other states, including California, in installed solar capacity. ERCOT, the main grid operator, has more than 18 gigawatts of solar power, enough to provide electricity for approximately 3.7 million households at times of highest energy consumption.

map of the path of solar eclipse 2024

During the eclipse on April 8th, many solar farms across the US will be in the “path of totality”. During the eclipse, solar generation may drop to around 7.6% at 1:40 pm from its peak of 99.2% at noon, and the power output at the peak of the eclipse will temporarily drop to near zero.

While sources like solar and wind have been able to flatten the ‘duck curve’, their reliability is always under scrutiny, especially in the light of climate change unpredictability.

However, the actual superhero for grid reliability and stability is Energy Storage Systems, particularly Battery Energy Storage systems (BESS).

Battery Energy Storage Systems (BESS) to the Rescue

Battery storage operating capacity in the US increased by 7.9GW last year, bringing the total installed base to 17GW by the end of 2023, according to the American Clean Power Association (ACP) trade group.

As a result, the cumulative output and capacity of installed battery storage in the US have reached 17,027MW and 45,588MWh, respectively. This represents an 86% increase in cumulative installed power capacity (MW) and an 83% increase in cumulative installed energy capacity (MWh – energy).

The increased capacity to charge and discharge can help supply electricity during critical periods. This could potentially supplement the dispatch of 17-18 GW over a brief period, thereby maintaining grid stability.

Before we delve in, let’s understand the role of Solar Power in the grid.

Role of Solar Power

The ability to create solar power is expected to double around the world from 2022 to 2028. Plus, the U.S. can now make three times more solar energy than it could during the 2017 total solar eclipse.

In general, clouds are one of the obvious problems for solar power. When it’s cloudy, solar panels make much less energy. They only produce 10% to 25% of the energy they would on a sunny day.

System operators maintain accurate models for the daily production of solar power across the U.S. These models take into account regions of the continental U.S. that may experience cloudy skies. By using solar power and batteries together, operators can use solar electricity even when it’s cloudy or nighttime.

Planning for an eclipse requires electrical system operators to estimate the decrease in energy production. They also need to calculate how much power the reserves will need to provide.

Solar power production can decrease rapidly during the peak of an eclipse, possibly putting a strain on the electrical transmission lines. To maintain smooth operations, grid operators may need to use local reserves and limit power transfer between grids during this time.

This approach can reduce the load on transmission lines within local grids and help avoid temporary blackouts.

Let’s break down the importance of BESS

In simple terms, one or more rechargeable batteries make up Battery Energy Storage Systems (BESS). The type of battery often used is the lithium-ion battery, which is also commonly found in mobile phones and electric cars.

applications of utility-scale energy storage
Applications of Utility-Scale Energy Storage (Source: NREL.Gov)

These systems are multifunctional, serving as critical assets for grid stabilization and providing essential backup power.

Enhanced Flexibility –

BESS provides improved flexibility in managing energy resources and distributing them efficiently, ensuring optimal utilization.

The amount of battery storage needed to integrate high levels of renewable energy isn’t fixed. Instead, the requirement for grid-scale battery storage depends on specific system characteristics, which include:

  • The current and projected mix of generation technologies
  • The flexibility of existing generation sources
  • Interconnections with adjacent power systems
  • The hourly, daily, and seasonal patterns of electricity demand
  • The hourly, daily, and seasonal profiles of current and planned VRE.

Advancing battery technology

From a technological standpoint, customers primarily focus on cycle life and affordability when it comes to batteries. Lithium-ion batteries currently dominate the market because of their ability to meet these needs.

Nickel manganese cobalt cathodes were once the primary battery chemistry, but lithium iron phosphate (LFP) has become a more affordable alternative. Despite its lower energy density, customers appear to accept LFP as a trade-off for cost.

However, the scarcity of lithium has allowed for other promising battery technologies, particularly cell-based ones such as sodium-ion (Na-ion), sodium-sulfur (Na-S), metal-air, and flow batteries.

Sodium-ion technology is worth monitoring. Although sodium-ion batteries have a shorter cycle life (2,000-4,000 versus 4,000-8,000 for lithium) and lower energy density (120-160 watt-hours per kilogram versus 170-190 watt-hours per kilogram for LFP), they have the potential to be up to 20% cheaper than LFP.

This technology continues to improve, especially as manufacturing scales up. Sodium batteries also have safety advantages, as they are less likely to undergo thermal runaway. Additionally, sodium-ion batteries have a smaller environmental impact than lithium batteries, which is another benefit.

Considering these factors, it’s likely that sodium-ion batteries will gain a larger market share in the Battery Energy Storage System (BESS) sector. At least six manufacturers are expected to start producing sodium-ion batteries in 2023.

Providers will need to decide which technology to invest in, and integrators might consider preparing their systems for an easy transition to sodium-ion batteries as they become more widely available.

Let’s revisit the 2017 Solar Eclipse

In 2017, a solar eclipse happened in the lower 48 states of the US, the first since 1979. This event made us think about the growth of solar energy and the role of energy storage systems. During the eclipse, the moon blocked the sun across 14 states. All states could see it, even if they weren’t directly under the eclipse.

In the last eclipse 38 years ago, solar panels were rare, and solar energy was a tiny part of our electricity supply. But by 2017, the US was making 43 times more solar energy than ten years before, enough for over five million average-sized homes.

Even with this growth, solar energy was only about one percent of the electricity. However, the fast growth made them think about how to use more solar energy, especially as they aim for 100 percent renewable energy.

2017 solar eclipse across US

During the 2017 eclipse, experts thought that up to 10,000 megawatts (MW) of solar electricity would be blocked. Some people saw this as a problem for solar energy’s reliability, but it actually showed the potential of solar energy and the importance of energy storage systems.

The National Renewable Energy Laboratory (NREL) said that the US gets enough sunlight to make our electricity 100 times over. Just using rooftop solar, we could make about 112 times the solar energy lost during the eclipse.

The key to using this potential is battery energy storage systems. As prices have dropped over the last ten years, battery storage in the U.S. has grown 2,000 percent, and this is likely to keep going.

Batteries let us use clean energy even when the sun isn’t out, helping us have a stable and reliable electricity supply, whether during a rare eclipse or at night.

Reviewing the ‘Path of totality’ – April 8th, 2024

In the Northeast, which falls within the path of totality, grid operators have been preparing for months. They’ve conducted simulations to anticipate what will happen on April 8th. Normally, they predict the daily energy demand in advance, considering variables like season, day of the week, and weather.

The potential impact of the eclipse is also taken into account, as people might be outdoors more than usual instead of using electricity indoors.

An eclipse shows how hard it is for those who run the power grid to balance the need for electricity with how much is available. The way they handle a drop in solar power—whether they pull extra power from batteries, pump water, or use natural gas—depends on the energy market that day.

New England has two large facilities that can store energy by pumping water. They can provide almost 2000 megawatts of energy quickly. Methods for storing energy and their cost-effectiveness are always getting better. The technology and cost-effectiveness of energy storage options are continuously improving.

BESS Surge - bar chart
US annual and cumulative clean power capacity growth, as featured in the new report. Image: ACP

Modern software has made it easier to instantly dispatch power from battery storage. When there’s a significant drop in solar production, the software can respond in real-time.

In the case of an eclipse, grid operators are prepared well in advance to manage the event. In case of an unexpected drop in production, the software can instantly activate the batteries to release stored energy, guaranteeing a dependable power supply. This reaction is faster and more adaptable than traditional systems.

The National Renewable Energy Laboratory will be observing what happens during the eclipse in grids across the country. The lab previously studied the grid during the 2017 eclipse, focusing primarily on the West Coast. Nationally, solar power has tripled since then.

The key lesson from the solar eclipse is to learn how to operate the grid during less predictable events that have similar effects, such as extreme weather and wildfires. But in this case, the “path of totality”