Categories: Know HowSolar 2 Store

Solar Energy storage technologies | What are the benefits?

The popularity in photoviltaic panels has led to the emergence of new Solar Energy storage technologies. PV modules storage solution through batteries. Adding battery storage to store surplus power.

At times where not so mutch solar electricity is generated, cloudy days and by night, a home can still use solar power. But is a pv panel installation with solar backup a smart investment?

Renewable energy storage technologies has still not reached the mass market. Thanks to companies such as BYD with the b-box, they are gaining popularity, also in our region. Many solar installers now also offer battery storage to store power. And rightly so, the utopia of becoming completely independent from the electricity grid is attractive, especially with energy prices rising.

Also, batteries are becoming increasingly attractive with the rise of the electric car. Your electric car used as energy storage system.

In the Algarve Portugal, more photovoltaic panel installations currently installed with batteries. We expect that this will be increasing within a few years, indeed when storage cells become more affordable.

Solar Energy storage technologies | What are the benefits?

Before you look further for battery backup and whether it is suitable, it is good to understand how batteries work.

With a traditional panel installation, an inverter is generating electricity. The inverter is converting direct current to alternating current so that it is compatible with household appliances.

The devices directly use power. The not applied current will inject into the electricity grid. When the solar panels generate more energy than is necessary, you will see the counter rollback.

The surplus is not reimbursed if you generate more power than you consume.
For example, a panel system supplies 4000 kWh, but your consumption is 3500kWh, then you lose 500kWh. Here is where a battery storage system is impressive.

When you provide a battery system for installation, the excess power is stored directly from the panels. When the consumption is higher than the yield, extra power from the backup lithium system.

This makes independently from the electricity supplier living a possibility. Only when the battery is empty, no sun power is generated, energy is taken from the electricity grid.

Solar panels generate the highest yield when you are usually not at home during the day. Electricity is most consumed in the evening. The surplus from the day is stored. Therefore used effectively when you are home in the evening.

It is also possible to store electricity from the electricity grid. This is particularly interesting at off-peak hours or night rates. The battery can be charged when the power is cheaper. And then use the stored electricity during peak hours when electricity is (much) more expensive.

Solar Energy storage technologies | What are the benefits?

A solar panel battery system works just like the well-known small batteries with which we are all familiar with. Charging by injecting electricity directly from the grid and with a PV panel system.
When using power for household appliances, the converted electricity changed to alternating current with a grid-tied inverter.

How energy storage works.

With different types of energy storage technologies, each with their characteristics:

  • Lithium-ion batteries:
    For solar panel electricity storage, preferred this type of cell. The storage capacity is tremendous compared to the weight, and charging takes place quickly. Well-known battery brands such as BYD or Lg Chem both use lithium-ion batteries.
  • Lead acid batteries:
    Lead-acid batteries are the oldest batteries and used for solar energy system storage applications for quite some time. In terms of price, they are low, about half of lithium-ion batteries. Their major disadvantage is that they cannot discharge more than half, which makes it financially less attractive.
  • Operations and maintenance:
    Future maintenance for a lithium is les expensief.

When you are independently from the electricity supplier or with power outages, you cannot use electricity from the grid. In other words, you must be completely self-sufficient in your electricity consumption. Energy storage works during the winter, when the days are short and usually less sunny.

It can become challenging to store enough electricity in the batteries. You must then take into account, that a battery system that can cover up to 80% of your consumption.

If you use an average of 4000kWh per year, this means 11kWh per day. For three consecutive days with little sunlight you need battery storage of more than 25kWh. Such systems cost quickly 13000 Euros or more. And this will be multiple batteries.

Battery prices

The prices for battery storage are constantly changing. It is therefore virtually impossible to give a target price. It is important to start calculating the price per kWh and not simply looking at the sales price.

What are the benefits?

Use the following formula to calculate the price:
Price per kWh = (battery price / capacity * total number of cycles * efficiency * discharge percentage)

Before we delve deeper into an example calculation, it is good to see what each component in the formula means:

  • Battery price:
    The sales price for the battery.
  • Capacity:
    The amount of energy stored in the battery.
  • Total number of cycles:
    To express the lifetime of a battery. Take a look at the number of cycles that are guaranteed by the manufacturer. It’s the standard to indicate the life of a lithium cell.
  • Discharge percentage:
    Not every battery can be discharged entirely as this considerably reduces the life span. A battery with 10kWh and a discharge percentage of 50% can in principle only provide 5kWh. Lead acid batteries have a low discharge percentage.
  • Efficiency of energy storage technologies:
    Indicates how much energy, during the discharge cycle is lost.

How much energy can be effectively stored?

A 10 kWh battery with 90% efficiency can store and use 9kWh of energy.

The BYD B-BOX L 14.0 as an example:

  • Battery price: 7,209.70 Euro
  • Capacity: 13.5kWh
  • Total number of cycles: 5000 (guarantee of 1 cycle per day for 10 years)
  • Discharge percentage: 100%
  • Efficiency: 95.3%

Use the following formula to calculate the price:
Price per kWh = (battery price / capacity * total number of cycles * efficiency * discharge percentage)
Formula: 7,209.70 / (14.5 * 5000 * 0.953 * 1) = 0.104 EUR / kilowatt hour

Energy independence storage has proven itself with BYD and RCT power in practice. Many test with SMA sunny storage and SMA Sunny Island in power plants. Here in Portugal Algarve we have already supplied many systems with Lithium storage.