How Is Solar Energy Stored?

Solar Energy Storage

One of the most urgent problems humans face is how to meet the world's rising energy demands in a sustainable and environment-friendly way. On a sunny day, energy from sunlight can provide the Earth's surface with about 1,000 watts of power per square metre, which is a plentiful, safe, and cost-free resource. In fact, the total solar energy the planet receives in just two hours is more than enough to cover the world's current energy needs for an entire year. But how is this energy stored?

How Does Solar Energy Storage Work?

When the sun is out, your solar PV (photovoltaic) system actively collect solar energy by absorbing sunlight. Your inverters convert the DC power generated by the panels into alternating current (AC) for immediate usage in your home. Many people, including yourself, might be at work when the sun is at its hottest. Solar batteries can help with that.

In general, solar batteries are a way to store the energy produced by your solar panels for usage when the sun isn't shining. They absorb the DC energy generated by your solar panels and keep it for later use. The inverter converts it into valuable AC electricity when you're ready. When you utilise the power at night or in adverse weather, you are pulling down the charge from the batteries, which were charged by solar energy.

How Can Solar Batteries Help In Saving Power?

In residential use, solar battery units are integrated with your system and installed in a bank. As the system uses your charged batteries before pulling them directly from the grid, you'll spend less on electricity bills.

This will prove beneficial for your wallet if the electricity prices charged by your utility are determined by a variable time-of-use (TOU) system that varies throughout the day in response to demand. Therefore, you are engaged in 'self-consumption' rather than collecting credits for any excess power through net metering, which is an excellent method to achieve more power savings.

Considerations When Selecting A Storage Option

When selecting a solar battery, you should focus on the following three factors:

Ability and strength

Your regular power consumption habits and the most significant power you might need at any given time will determine the best battery model. Every solar battery has a specific capacity, expressed in kilowatt-hours (kWh). Additionally, there is a limit on the number of power batteries that can discharge simultaneously.

Warranty of battery

Solar batteries will lose their ability to store charge over time as they undergo the same cyclic degradation as all rechargeable batteries. Many batteries will come with a warranty that ensures a certain number of cycles or a portion of their original capacity.

Round trip efficiency

For batteries to store solar energy, some energy is needed. The ratio of power you remove to power your input is known as round-trip efficiency. A round-trip efficiency of 66.6 percent, for instance, indicates that you can only take 4 kWh while giving the battery 6 kWh. In general, batteries with a higher round-trip efficiency will be more cost-effective.

Depth of discharge (DoD)

The percentage of a battery's storage capacity is referred to as the DoD. If a 10-kWh battery has a DoD of 50%, you should only utilise 5 kWh of the battery before recharging it. The more power you can use before recharging, the higher the DoD.

It's crucial to remember that you'll need an emergency power supply if you're worried about keeping electricity running during a power outage. Solar batteries with an EPS (Emergency Power Supply) can function as a backup in case of power outages.

What Are The Different Solar Storage Options?

Storage using hydrogen gas

Hydrogen gas is the best medium for storing solar and transferring energy since it has one of the top energy contents of any fuel. The hydrogen storage system manipulates the characteristics of cyclohexane for energy production. It occurs through a continuous cyclic process in which hydrogenation is followed by dehydrogenation.

Six hydrogen atoms from many hydrocarbons are added to the benzene already in the hydrogen storage system after solar exposure to create cyclohexane. After the six carbons are removed from cyclohexane, dehydrogenation reactions take place. It makes the chemical usable for energy storage devices and other purposes.

Dehydration reaction

A crucial component of the dehydrogenation reaction is platinum-based nanoparticles. These are photocatalysts, temporarily donating their photoexcited electrons to pre-existing cyclohexane molecules. With this donation, the bonds between carbon and hydrogen are broken, releasing hydrogen atoms without generating too much heat.

This dehydration reaction is one of the most effective methods for energy storage. It enables up to 97 percent of benzene to be transformed back to cyclohexane and is best suitable for stationary applications, such as solar energy and wind turbines.

In order to continue the effort to preserve renewable energy, future research initiatives are looking toward other uses in the storage and transportation of hydrogen produced from other natural sources, such as water splitting and water electrolysis.

Thermal energy storage system

Thermal energy storage has been successfully used since 1985. It generates electricity by capturing heat from the sun and storing it in water, molten salts, or other fluids. Other solar power storage technologies include compressed air energy storage (CAES), hydrogen storage, pumped hydroelectric storage, flywheels, and batteries.

A reservoir or tank serving as the storage medium, an integrated refrigeration system, piping, a pump, and controls all make up a thermal energy storage system (TES). Low-temperature TES typically uses cold water and reheating processes, but high-temperature TES systems are based on latent and thermochemical heat storage.

Depending on their working temperature, TES systems can be classed as either low-temperature TES or high-temperature TES. The TES system can store vast amounts at a relatively low capital cost. It also prevents the creation of significant risks, with a daily self-discharge loss of just 0.05-1 percent.

Energy storage using compressed air

Compressed Air Energy Storage (CAES) is a generation storage method in which the elastic potential energy of compressed air is stored until it is needed to generate electricity. As solar energy enters the CAES system, an electric motor is used to power an air compressor. Compressed ambient air is then stored under pressure in an underground cavern until it is needed.

The CAES system experiences heat generation as a result of the high air pressures being applied to it, which might result in unintended energy discharge. Inter and aftercoolers are present in the CAES system, where heat is either extracted during compression or removed via an intermediate cooler.

It helps in lowering discharge temperatures to 176.6 Celsius/350 °F. The favourable characteristics of salt caverns include their great flexibility, low-pressure losses, and total lack of oxygen interactions between the air and host salt rock. This makes them frequently the chosen places for CAES.

Pumped hydroelectric storage systems

When supply outpaces demand, pumped hydroelectric storage systems store solar energy by pumping water into the upper reservoir. When demand exceeds supply, water in this initial reservoir is discharged downhill by flowing via turbines into a lower reservoir, enabling power production.

The term 'flywheel' refers to a comparable transmission energy storage system in which a large rotor is housed inside a vacuum-sealed cylindrical structure. The device's rotor accelerates to highly high speeds after drawing power from its energy source and storing it as rotational energy. The rotor can be put in 'generating mode,' which slows it down and sends electricity back to the grid for consumer usage.

Batteries and flywheels are portable energy storage devices that are frequently compared to equivalent energy distribution systems. Batteries can range from sodium-sulfur, metal-air, lithium-ion, and lead-acid batteries for large-scale energy storage, depending on the energy source and application.

Advantages Of Solar Energy Storage

Here are just a few pros of installing solar-plus-storage that explain why solar energy storage systems are growing in popularity every year:

Backup capacity

Unlike popular belief, the solar panel alone cannot supply your home with electricity during a power outage. You must combine your solar system with a solar battery to keep your lights on when the power grid is down. Therefore, areas where severe power outages are frequent, see the highest levels of energy storage use.

Also, compared to gas-guzzling generators, solar batteries provide backup power in a much quieter manner. Additionally, you need not worry about charging a battery; all you have to do is sit back and wait for the energy from your solar panels to be ready for use.

Energy independence

You can depend less on the power grid if you have solar energy storage. We already know that means you'll be safe when the grid electricity goes out, but it also means you'll have less overall dependence on the utility.

One benefit of solar energy storage is that it shields you from the annual spikes in electricity prices that are all but certain to occur. Instead of using the grid and paying high fees for electricity, a battery allows you to draw power directly from it.

Moreover, you are entirely aware of the source of your power. With a utility, foreign gas and oil can be used to produce energy. With solar, you can relax knowing that the solar energy that powers your home is made right on your roof!

Savings on your electric bill

Due to a utility pricing structure known as net metering, a solar battery will help save you additional money on your power bills. When your residence generates more solar energy than it needs, your utility will pay you the total retail rate of power for it. This is known as full retail net metering. The utility essentially serves as your 'financial batteries'.

Not all utilities provide complete retail net metering. Instead, they pay less for extra solar electricity. Here is where additional power bill reductions are possible from solar energy stored. You keep your excess electricity for later use and receive the total retail value out of it instead of sending it to the grid and getting paid at a cheap rate.

Solar storage may also be beneficial if your utility charges higher electric pricing during peak demand hours using time-of-use rates. During certain times, you can avoid paying the high rates established by your utility by using the battery, which stores electricity.

Your Solar Energy Storage Needs

Although solar energy storage systems can be pricey in terms of upfront costs, you get to save more in the long run by generating your own power through solar panels and storing energy in a solar battery. Of course, all this happens without you having to actually do anything.

The panels and battery work together to ensure you have power ready for use when you need it. When it comes to solar systems, it's crucial to get a high-quality system with a strong battery so you don't run out of power quickly. A professional solar installer can help you get the right solar battery for your needs.