How Solar Energy Is Stored

By Solar Energy Last updated Feb 16, 2024

When solar energy is pumped into a battery, a chemical reaction in the battery components stores the energy. The reaction reverses the discharge of the batteries, causing the current to leak out of the battery. Various media such as water and molten salt are stored in insulated tanks, and the energy must be boiled from the water to generate energy.

Solar batteries are the secondary power source from which your home draws, depending on how much electricity their solar panels produce. If your solar panels produce more electricity than you need, the excess energy is charged into a solar battery. In theory, a battery absorbs excess solar power, converts it, and stores it for later use.

The excess electricity produced by the panels when the battery is fully charged is sent to the grid. When your solar battery is depleted, your modules do not produce any electricity for your home that you can get from the grid.

Home energy storage is especially useful when solar batteries are coupled with a home solar system, but batteries can also be useful for homeowners without solar panels. As a bonus, solar batteries, as they store energy in your home, can provide short-term emergency power in the event of a power outage near you.

One way to store solar power is to use a battery bank to store electricity generated by a solar PV system. Batteries in solar power storage systems can be used on the grid, connected to a PV system as a battery backup, or as stand-alone PV systems. Small energy storage technologies use solar storage to charge electricity from the grid or provide backup power via diesel-powered backup generators.

Batteries are similar to cars in that they are designed to withstand the kinds of charges and discharges that they require for solar panels. Solar batteries not only stop the light when the sun goes off the grid but also support the supply grid by filling in the gaps in renewable energy generation in the interim when clouds pass or the wind dies down. ^{Sources: 0, 4}

Before the popularization of grid-connected inverters in the late 1990s, solar panels were independent of the grid – which meant that the grid was not connected to the grid. If you wanted to have electricity at sunset, you had to have a battery to store energy, whether it was a large bank of golf carts or lead-acid batteries. ^{Sources: 0}

Twenty years have passed, at least in the US, and the vast majority of solar panels no longer use batteries but use grid measurement to export excess electricity when solar production exceeds the load or to import electricity when the grid load exceeds production. Since solar systems depend on the sun, the main problem with harnessing solar energy is that we do not have an efficient way of storing the energy that solar systems produce. For this reason, solar panels are no longer as reliable or stable as they used to be. ^{Sources: 0, 2}

Understand How Solar Energy Is Stored

Solar energy is a remarkable resource, but its availability doesn’t always align with our energy needs. Fortunately, we can store solar energy for later use through various methods. Let’s explore how this process works:

Energy Storage Basics

Energy storage refers to technologies that capture electricity, convert it into another form of energy (such as chemical, thermal, or mechanical), and then release it when needed. Here are some key points:

Lithium-ion batteries are commonly used for energy storage. Although no storage method is 100% efficient (some energy is lost during conversion and retrieval), storage allows us to use energy flexibly at different times from when it was generated.
Storage facilities have different energy capacity (total stored energy, usually measured in kilowatt-hours or megawatt-hours) and power capacity (amount of energy released at a given time, usually in kilowatts or megawatts). Different capacities serve various purposes.

Solar Energy Storage Methods

a. Battery Storage

When solar panels generate electricity, an inverter converts the direct current (DC) electricity into alternating current (AC) electricity.
The AC electricity powers household appliances, and any excess power is stored in batteries for later use.
During periods without sunlight, the battery releases its stored energy, providing continuous power.

b. Thermal Storage

Some solar systems use thermal storage to retain heat from the sun.
This stored heat can be used for space heating, water heating, or other applications even when the sun isn’t shining.

c. Mechanical Storage

Compressed air and pumped hydropower are examples of mechanical storage.
These systems store energy by compressing air or pumping water to higher elevations. When needed, the stored energy is released by expanding the air or allowing the water to flow downhill, driving turbines to generate electricity.

d. Electrochemical Storage

Batteries fall under this category.
They store energy chemically and release it as needed.
Lithium-ion batteries are commonly used for residential and commercial solar energy storage.

Advantages of Combining Storage and Solar

Balancing Electricity Loads: Storage ensures the smooth operation of solar plants during output fluctuations caused by passing clouds.
Firming Solar Generation: Storage helps provide a steady supply of energy even when solar production is low.
Resilience: Storage enhances system resilience during major weather events.
Grid Variability: Storage can smooth out variations in solar energy flow on the grid.

In summary, combining solar energy with storage technologies allows us to maximize efficiency, improve power quality, and integrate solar into our energy landscape more effectively ¹ ².

How To Store Solar Energy?

Solar energy can be stored in several ways, each with its advantages and disadvantages:

1. Batteries:

This is the most common method for residential solar systems. Batteries store excess solar energy as electricity, which can then be used later when needed.

Pros:

Widely available: readily available and can be installed with most solar systems.
Fast response: can quickly provide power during outages or peak demand.
Scalable: can be sized to meet your specific needs.

Cons:

High upfront cost: batteries are currently the most expensive component of a solar storage system.
Limited storage capacity: batteries can only store a limited amount of energy, so may not be suitable for high energy needs.
Degradation over time: battery capacity decreases over time, requiring eventual replacement.
Environmental concerns: mining and manufacturing certain battery materials can have environmental impacts.

2. Pumped hydro storage:

This method involves storing water at a high elevation and releasing it through turbines to generate electricity when needed.

Pros:

Large-scale storage: can store vast amounts of energy, ideal for large-scale applications.
Mature technology: well-established and reliable technology.
Long lifespan: can last for decades with proper maintenance.

Cons:

Requires specific geographical features: needs hills or mountains with water reservoirs.
High construction costs: can be expensive to build and maintain.
Environmental impacts: can disrupt natural ecosystems and displace communities.

3. Compressed air energy storage (CAES):

This method stores compressed air in underground caverns and releases it to drive turbines when needed.

Pros:

Large-scale storage: can store large amounts of energy like pumped hydro.
Flexible location: doesn’t require specific geographical features.
Lower environmental impact: less disruptive to ecosystems than pumped hydro.

Cons:

Emerging technology: still in development and less proven than other methods.
High construction costs: can be expensive to build and maintain.
Efficiency losses: energy losses occur during compression and expansion.

4. Hydrogen storage:

This method converts excess solar energy into hydrogen through electrolysis and stores it for later use in fuel cells to generate electricity.

Pros:

Clean and flexible: hydrogen is a clean fuel and can be used for various applications.
High energy density: can store large amounts of energy per unit volume.

Cons:

Emerging technology: still in development and not widely available.
High infrastructure costs: requires specialized infrastructure for production, storage, and transportation.
Efficiency losses: energy losses occur during conversion and reconversion.

5. Molten salt storage:

This method uses molten salts to store thermal energy from concentrated solar power (CSP) plants. The heat is then used to generate steam to drive turbines when needed.

Pros:

High-temperature storage: can store heat at high temperatures for extended periods.
Scalable: can be sized to meet specific needs.
Long lifespan: can last for decades with proper maintenance.

Cons:

Limited to CSP plants: not suitable for photovoltaic solar systems.
High construction costs: can be expensive to build and maintain.
Technical complexity: requires specialized equipment and expertise to operate.

The best method for storing solar energy depends on several factors, such as your energy needs, budget, and available technology. Consulting with a solar energy expert can help you determine the best option for your specific situation.