Battery energy storage: Storing solar energy

Introduction

Let’s talk battery energy storage. It’s the popular topic on the lips of almost everyone. Especially with a passing interest in renewable energy. Everyone wants to understand about battery energy storage. 

There is no doubt that battery technology is the way to the future. It’s the next big step towards independence from the grid for home energy. 

To learn everything, you need to know about the subject. So please, read this article.

The basic functions performed by the solar batteries

With battery storage, you are in a position to:

1. Daytime storage of surplus solar production for use at night
2. Manipulate time-of-use tariffs (TOU). Especially when it’s cheaper to buy power at off-peak rates and store it for peak hours.
3. Providing your home with backup power
4. Selling energy back to the grid for a premium rate at peak days

So in a broad sense, solar energy operates rather well. It processes the surplus solar energy from the PV device. That’s for overnight consumption. This also helps create more cash reserves. It becomes a very beneficial long-term investment. Especially with the reasonable prices of current export customs duties. 

Another important feature of battery energy storage systems is that it serves to protect your house from power cuts. Thereby, lessen grid supply reliance.

What is a solar battery and how does it work?

A battery that stores energy from a solar PV device. Well, I say that is a solar battery. The panels of the device absorb energy from the sun. Finally and transform it into electricity. It then passes through the inverter for use in your home. 

A battery is an additional component that will allow you to store energy generated from your panels. For instance, when your panels no longer produce energy in the evening it will use the stored energy.

If the output of your device is greater than your energy usage, the excess energy is sent back to the grid. This mechanism called “net-metering.” 

You will get a credit on the next energy bill when this occurs, which will decrease the amount of your charge.

But solar batteries can be a wonderful asset to their solar PV system for those who are off-grid or would rather preserve the surplus power themselves rather than adding it back to the grid.

How Does Storage for Solar Batteries Work?

Surplus electricity from your solar PV system is pumped into the battery, as stated previously. 

This ensures it is possible to store the energy surplus in it and is readily available for you to benefit from when your solar panels do not produce sufficient power.

Remember the following when selecting the type of batteries to use for energy storage:

1. Warranty and battery capacity
2. Power capacity 
3. Depth of Discharge DOD

The lifetime of a battery is normally somewhere around five and 15 years. However, it is estimated to rise dramatically over the years to stay up with the demand of solar panels. 

Battery energy storage warranties are typically issued in years or cycles, e.g. the Nanobatteries has a 10-year or 10,000-cycle warranty (whichever comes first).

The power capacity refers to the total amount of electricity that can be stored by the battery. Solar batteries are typically reusable, which means that to maximize power. So you can have numerous battery energy storage at home.

The discharge depth or DOD tests the degree. All to which, compared to its total power, a battery can be used. 

If a battery energy storage has a 100 percent DoD, it ensures you can use the entire amount of battery capacity. Especially to power your home (e.g. 2.5kWh). 

If a battery has a 94 percent DoD. Well that means that up to 94 percent of the battery power can be used.

Common types of battery storage

Coupled storage of AC

These storage systems may typically store energy both from solar power and from the power system. 

Also, during blackouts, they could provide off-grid power supplies. These are comparatively costly, allowing energy to still be extracted from other resources. 

One aspect is that during lower power tariff time slots, it will allow homes to extract electricity from the system.

Coupled Storage of DC

Batteries mounted between the panels and inverters store DC power directly from the panels, making it one of the most cost-effective systems available on the market right now. These are not capable of grid power storage. 

When the aim is to store excess solar energy for nighttime use these types of batteries are most suitable. 

But they do not have insurance against grid outages for these systems. So, the machine also stops working if the grid goes down for some reason.

Hybrid inverters

These are a mixture of the two forms described above as the name suggests. Without needless conversions such as a DC coupled storage, they allow the electricity to be stored into batteries and at the same moment could provide defense from grid outages. 

In the industry, they have the largest expense. There are multifunction hybrid inverters. But the lower performance decrease over time compared to the alternatives is one main advantage.

Types of batteries

Lithium ion

Your best option for your home battery will be Lithium ion for the most stable lifetime and DoD. This technology uses the majority of current home battery capacity, as they have a longer lifetime and higher DoD. 

Although lithium ion batteries are more expensive than lead acid batteries, they are more compact. The Nanobatteries, LG Chem Resu and Tesla Powerwall are examples of lithium ion batteries.

Lead acid 

Lead acid batteries have been used for decades and are among the cheapest varieties for off-grid power systems in home energy storage.

The downside to buying this type of technology is that, compared to other types of batteries, it is becoming outdated and has a lower DoD.

How to calculate battery charge time 

In order to calculate the battery charge time, you need to find out the DC current value because Direct current (DC) is used to charge batteries and is also used as the power source in virtually all electronic systems. 

For this purpose, you can use any charging time calculator which is available for free online. Today, almost all alternating current (AC) is electric power that is being transmitted all over.

To calculate and convert the electric currents from alternating current (AC) to direct current (DC), this advanced online AC to DC converter would be useful.

Benefits of Storage of batteries

Having battery storage allows you to become more independent of energy. Batteries maximize the self-consumption of your solar power, reducing the amount of electricity you need to buy from the grid. 

They also allow your home to continue using an evening’s solar power by storing the excess solar energy produced during the day so that when you need it, it is readily available to use.

Batteries can help balance short-term power fluctuations on a larger scale, manage peak demand and act as a backup to avoid or recover from power outages that affect an entire grid line. 

The installation of energy storage solutions also affects renewable energy supply and demand. 

When energy storage solutions are developed, cleaner energy sources can be more easily integrated into the electricity ecosystem and can give us more flexibility in producing and using electricity.

To be paired with all solar PV systems, a solar battery is not necessarily appropriate. 

Conclusion

First of all, you need to ensure that your system is compatible with the addition of a battery, and if you want to add a battery to further reduce your electricity bills. 

You will need to ensure that your system produces enough excess energy to charge the battery once it has supplied your home with the on-going daily energy demand.

If not, to provide the required excess energy, you may need to consider increasing your solar PV capacity.

This article was written by Puti Odedra who is Senior Author at Reinger, Gibson and Cassin.