LITHIUM BATTERY SYSTEMS FOR SOLAR

Since the discovery and first application of electrical energy, until today, the same problem has always arisen ... the accumulation of it.

At present, our Battery Systems is made up of different phases: 

• Generation

• Distribution

• Transportation

• Commercialization

The problem is that there is no point at which we can accumulate a large amount of energy due to its great limitation . 

For this reason, continuous research is being developed to improve the capacity and quality of energy storage. In this case, we will discuss the last great technological advance, Li-ion batteries (LiFePO 4 ) or, also commonly known, as lithium Battery Systems. But first, we will make a brief introduction about what batteries are and what is their application with regard to photovoltaic solar energy in homes.

The battery is a device that is responsible for storing electrical energy through stored chemical energy, in turn, in electrochemical cells. They contain a positive electrode, a negative electrode and electrolytes, which are responsible for the batteries to power an electrical circuit.

Since the appearance of systems for the use of electrical energy through solar energy in homes, different models of batteries have emerged until reaching the aforementioned lithium batteries.

Why use lithium batteries?

Lithium Battery Systems have great advantages over conventional batteries:

• They do not suffer from the so-called 'memory effect' and can be charged at any time in the state of charge (SOC) without reducing their useful life

• They are the batteries that have the highest level of capacity density .

• They have greater storage capacity and a longer useful life.

• They are totally safe and reliable.

At Cambio Energético, we make a comparison between lead-acid batteries and lithium batteries.

It is advisable to look at this article to understand, even better, the importance of it; 

To make the comparison of these batteries, we are going to classify them into Low voltage (LV) and High voltage (HV). It should be taken into account that, for photovoltaic self-consumption , HV batteries are recommended in installations from 10 photovoltaic panels of 280Wp. While, for solar installations isolated from the grid , we can divide them into domestic and industrial.In the case of domestic installations up to approximately 10kW of installed power, the use of LV batteries with MPPT regulator connected up to 48V is recommended.

For installations in the industrial field, which are usually larger, it is recommended to use HV batteries due to their greater voltage range and three-phase connection. Therefore, each case must be studied to optimize the installation, adapting to the consumption and use to which said batteries would be subjected.In installations where we are in the optimal range for the use of HV Battery Systems, the following advantages occur.To begin with, the energy of a solar photovoltaic system is generated in DC and the solar inverter converts it to AC.

A battery-powered inverter connected to the utility grid via AC converts all unused excess energy back into DC so that it can be stored in a battery, while DC-connected storage uses a hybrid inverter, where the system Solar energy and battery are connected to the same inverter. Therefore, there are many reasons why AC storage with HV (high voltage) batteries offers a number of advantages in terms of cost, flexibility and risk compared to DC wiring.

1- An inverter for batteries and an inverter for the solar system that, compared to other solutions based on hybrid inverters, represents an installation with few components.

2- The investment previously made in existing facilities is not lost.

3- Lower cost solution, thanks to the use of transformerless inverters, which also leads to greater efficiency. 

4- Greater reliability, since they use much fewer components thanks to the use of the inverters mentioned above.

5- Greater flexibility of location within the facility. The battery can be installed in any area regardless of the installed system.

6- Greater independence from the electricity grid, allowing the simultaneous supply of energy from both the photovoltaic system and the batteries. In this way, it is possible to supply 100% of the charging needs of your home. A system with a hybrid inverter could only supply 66% of the household's load.

7- Improvement in the management and resolution of “blackouts”, through switches that are interconnected with the AC battery inverter.

8- Greater efficiency and more energy. This is one of the most important advantages.

When transforming the current from DC to AC there are losses, but with a system connected to AC, despite having a longer path in the energy conversion process, better results are obtained in terms of efficiency when extracting the energy from the Battery Systems. After listing the advantages of the AC connection together with a high voltage battery, we make a comparison between LV and HV batteries.