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  • Writer's pictureSarah Lozanova

Comparing Different Types Of Solar Energy Storage Systems

Energy storage systems have become popular among homeowners seeking greater energy independence and backup power during grid outages. The federal investment tax credit (ITC) recently increased to 30% for solar systems and standalone battery storage, further fueling demand. In addition, numerous states are now offering battery incentives, including California, Hawaii, Illinois, Maryland, Massachusetts, and Oregon. Thus, 2023 is poised to be a banner year for battery storage adoption across many markets, from residential to large-scale storage.

“The solar ITC extension is good news for the residential storage industry, preventing a drop in residential solar-plus-storage installations that would have otherwise arrived in 2024. The standalone storage ITC will also boost storage retrofits on homes with existing solar,” said Chloe Holden, research analyst at Wood Mackenzie, in a press release.

Due to the strong demand for clean energy storage, understanding the various options and emerging technologies is helpful when speaking with prospective customers. Knowing the possibilities allows solar contractors to better serve clients by designing and installing solar panel systems with energy storage technologies that meet their needs while boosting their return on investment.

What Is A Solar Energy Storage System?

Because solar energy is an intermittent energy source, it is only available during daytime hours. Solar energy storage systems allow homes and business owners to store energy for later use. For off-grid systems that aren’t connected to the electrical grid, batteries enable properties to have power around the clock. For grid-tied systems, a hybrid solar system with battery storage enables homeowners to have power during blackouts and to use solar electricity when preferable.

In areas with time-of-use rates, renewable energy storage systems allow utility customers to further reduce their electricity bills. They can use stored energy when rates are highest and charge their batteries when rates are lower, reducing the payback period of the photovoltaic solar system.

Some of the most popular solar energy storage systems are the Enphase IQ, Generac PWRcell, LG Chem RESU, Panasonic EverVolt, Sonnen Eco, SunPower SunVault, and Tesla Powerwall 2.

Why Is It Important To Store Solar Energy?

An aging power grid and increasingly common extreme weather events have caused power outages to become more common. For example, some utility companies have been cutting off the power during times when threats of wildfires are particularly high. These public safety power shutoffs are designed to help prevent electrical equipment from causing wildfires but result in numerous homes and businesses losing power.

Although backup generators are an option for generating electricity during power outages, they rely on fossil fuels, are noisy, and create carbon emissions. As the cost of energy storage falls, solar batteries are becoming an increasingly popular way to keep the lights on during blackouts and store excess energy. They can also help with overall grid operation by smoothing out electricity supply and demand.

In some areas, there is so much installed solar capacity that electricity is wasted when solar power production exceeds demand. The duck curve is a graph that shows energy demand and solar energy production and is shaped like a duck. Unfortunately, occasional overproduction can lead to waste. However, solar batteries help avoid this by storing energy when demand is low, and making it available when solar production is low and power demand is high.

Different Types Of Solar Energy Storage Systems

There are many different energy storage technologies at different phases of development. Some are better suited for smaller mobile applications, while some require a lot of space and are better for large-scale applications. Certain technologies can store energy for a few hours, while others are better suited for long-term energy storage.

Electrical Storage

These battery energy systems store energy as electricity. The most common types are lead-acid, such as sealed AGM batteries and lithium-ion batteries. The most popular lithium-ion solar battery storage options are lithium iron phosphate (LFP) and nickel manganese cobalt (NMC).

Chemical Storage Systems

These energy storage systems store energy in the form of chemical bonds, not electrical energy. For example, hydrogen gas can be used to store energy in fuel cells for both short and long periods of time. Hydrogen is created from electrolysis, which uses electricity to split hydrogen and oxygen.

Thermal Energy Storage

These energy storage systems use a material, such as water, molten salts, or sand, in an insulated tank to store heat. Then, this energy is either used to generate electricity or is used to provide heat. Thermal storage is useful for concentrated solar thermal power (CSP) plants that focus sunlight to heat a fluid.

A relatively widespread application is solar thermal water heaters that use solar collectors to heat water in a storage tank. The hot water can then be used as domestic hot water or to heat buildings through a heat exchanger or a radiant floor heating system. However, researchers at Lawrence Berkeley National Laboratory are investigating how to take this to the next level using next-generation materials and systems.

Determining The Best Type Of Battery For A Solar Installation

When selecting a battery for a project, it’s critical to consider the power rating, usable storage capacity, roundtrip efficiency, warranties, cost, and battery lifespan. Lead-acid and lithium-ion batteries are the two most common battery technologies used to store solar energy. Although lead-acid batteries have a lower cost, they typically have a shorter lifespan and warranty period. As the price of lithium-ion batteries falls, they have become more popular for most residential and commercial solar applications.

LFP Vs. NMC Batteries

There are two types of lithium batteries used in solar PV projects. Lithium iron phosphate batteries contain a lithium iron phosphate cathode, which extends the lifespan of the battery and boosts safety. Nickel manganese cobalt batteries have a cathode made from a combination of nickel, manganese, and cobalt and are commonly found in laptops, cell phones, and electric vehicles. However, many EV manufacturers are switching from NMC to LFP batteries.

NMC batteries are widely used for solar storage, and the Generac PWRcell, LG Chem RESU, Panasonic EverVolt, and Tesla Powerwall 2 are NMC batteries. However, the Enphase IQ, Sonnen Eco, and SunPower SunVault are LFP batteries.

Typically, LFP batteries have a longer lifespan and are safer. In contrast, NMC batteries are usually a bit less expensive, have a higher energy density, and can withstand colder temperatures slightly better. However, NMC batteries are not necessarily more cost-effective than LFP batteries because they can have a shorter lifespan.

AC Vs. DC-coupled Battery Systems

When selecting a solar battery, it is also helpful to consider the inverter. Some solar storage batteries are AC coupled, so they have built-in battery inverters. Because AC-coupled solar systems do not require a hybrid inverter, they work with microinverters and string inverters.

If a DC-coupled battery is used, then a hybrid inverter is needed, such as the SolarEdge StorEdge. The Enphase IQ, Generac PWRcell, Sonnen Eco, SunPower SunVault, and Tesla Powerwall 2 are all AC-coupled batteries.

Different Types Of Energy Storage Work Better In Different Situations

Selecting the ideal energy storage solution is critical to successful projects. Although many different types of energy storage systems are on the market, some are better suited for specific applications or configurations. Understanding the project goals and budget is critical for choosing the optimum energy storage solutions. The GreenLancer team is available to help with all types of solar energy systems.

Work with GreenLancer on your next project to take advantage of our extensive expertise in adding storage to many different solar energy arrays.

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