A Complete Guide To The Best Battery Storage For Solar Panels

Categories: Review and Solar Battery Storage.

Ever wondered what the best battery storage for solar might be?

best battery storage for solar

There is no doubt that we rely on electric appliances to perform many of our daily routine activities. This is why the demand for electricity is increasing day by day.


Fossil fuels are the major source of electricity generation, but that is not a clean energy source. They pollute the air with green house gas (GHG) emissions. Renewable power generation sources are not net GHG polluters.


Increasing proportions of the electricity generated comes from renewable sources with more residential rooftop solar panels being installed each year. Solar power installations are often subsidised but then so too coal powered generators obtain a subsidy.


We are unlikely to stop subsidizing the use of fossil fuels for power but we might want to leverage the benefits of clean power generation to benefit our future generation's air quality.


Fortunately, with advancing technology, we can use the renewable energy resources in wind, water and sun. The sun is an unlimited power source that is available free to us every day.


Rooftop solar panel systems backed by the best battery storage for solar is the cheapest alternative to fossil fuels for residential power users.

best battery storage for solar

Best Battery Storage For Solar Panel

If you install a solar power system, invest in getting the best battery storage for solar power.


Batteries compliment a photovoltaic system by storing the DC energy produced by the solar panels. Energy generated and stored during the daytime is available when the sun sets. This store of energy runs electronic appliances in your house.


In 2018 more home battery storage capacity was installed than the existing supply. There are expectations that in 2019 the trend to installing solar storage batteries will continue.


The solar battery storage trend following the solar PV installation is growing rapidly. Batteries for energy storage usually have one of three chemical compositions. Lead acid, nickel cadmium and lithium ion. In time as the storage size of the VRFB technology is refined into the scale size suited for home solar as low as 8kW the use of vanadium redox flow batteries (VRFB) will increase into residential applications. VRFB are currently restricted to the commercial and utility sized applications.


The first types of batteries listed are more affordable. But, lithium-ion battery is the best battery storage for a solar panel system.


Lead Acid Battery

This type of battery is common as an electrical store in off-grid energy systems.

The batteries store the electrical energy in the form of chemical energy. During use the internal reactions convert stored energy into electrical energy when required. In this battery, the positive and negative electrodes immerse in an electrolytic solution. That solution is sulphuric acid diluted with pure water. The positive electrode plate is lead peroxide. The negative electrode plate is pure lead in sponge-like condition. An external electrical load connects between these plates.

best battery storage for solar

Discharging Process

When we connect a load, the molecules of sulphuric acid is split into H+ ions and So4ions. The hydrogen ions react with PbO2 plate to form PbO and H2O. This PbO reacts with sulphuric acid (H2SO4) and forms PbSO4 and H2O.

PbO2 + 2H → PbO + H2O


PbO+ H2SO4→ PbSO4+H2O

PbO2+H2SO4+2H →PbSO4+2H2O

SO4 ions move freely in the solution. Some of them react with pure lead and give extra electrons to become radical SO4 due to which it can’t exist alone and react with Pb to form PbSO4. As H+ ions take electrons form PbO2 and SO4- ions will discharge electrons to Pb plate, there would be a difference between the concentrations of two plates. Due to this there is a flow of current between two plates for balancing this inequality of electrons.

best battery storage for solar

Charging Process

When we disconnect the load, the density of sulphuric acid falls, but hydrogen ions being positively charged move to the electrode connected with a negative terminal of DC source. They take one electron form that source to become a hydrogen atom.


These hydrogen atoms react with PbSO4 to form lead and sulphuric acid.

PbSO4 + 2H → H2SO4 + Pb

SO4- ions move towards the electrode connected to DC source. They give their extra electrons to become radical SO4 and these radicals react with PbSO4 to form PbO2 and H2SO4.

PbSO4+ 2H2 + SO4 → PbO2 + 2H2SO4

Why Are Lead-Acid Battery Used?

They are:

  • Able to withstand frequent discharging
  • Cheaper than other kinds of batteries
  • More rugged durability - Tolerant to overcharging
  • Able to deliver more consistent performance than other batteries
  • Many suppliers world wide

Advantages of Lead-Acid Battery

  • Proven Reliability
  • Can maintain electrical charge for long periods with trickle charge 
  • Very long shelf life when stored without electrolyte
  • Safe
  • Low Upfront Cost
  • Can deliver very high currents in a burst for starting.
  • Easily and readily recycled
  • Wide range of sizes and capacities available

Disadvantages of Lead-Acid Battery

  • Requires Maintenance
  • Very heavy and bulky.
  • Can overheat during charging and generally not suited to fast charging
  • Typical charge/ discharge life between 300 to 500 cycles .
  • When electrolyte has been added to the battery it must be stored in a charged state to avoid deterioration of the active chemicals.
  • It can lead to corrosion

Lithium-ion Battery

Lithium-ion batteries are an advanced technology form of solar batteries.

 

Lithium-ion batteries are displacing the lead-acid batteries for solar storage.

best battery storage for solar

The main reason is deep-cycling capability. That means higher recharging and discharging rates and longer lifespan.

 

Lithium-ion is the best battery storage for solar panels.

What Are Lithium-ion Batteries?

The battery uses lithium ions to store the electrochemical energy.

That energy can convert into electrical energy when required.

Standard batteries have anode (negative terminal), cathode (positive terminal) and electrolyte (channel). Anodes are usually carbon or another similar non-metal. The cathode is a metal oxide such as cobalt oxide and the electrolyte is a solution of lithium salt and water.

How Does It Work?

best battery storage for solar

Charging and Discharging Mechanism In Lithium Ion Battery

The battery components exist in a container. To Charge the battery you connect an external power source. This causes lithium ions at the anode and electrons will move towards the cathode.


When we disconnect the external power source, the reverse process is able to occur.


When you connect an external load you complete the circuit. Electrons will flow through the external circuit. The ionized lithium atoms in the anode separate from their electrode. The lithium ions move toward the cathode through the electrolytic solution. Lithium ions combine with the cathode to become neutral.

Chemical reactions

Cathode Electrode Reaction:

CoO2 + Li+ + e- LiCoO2

Anode Electrode Reaction:

LiC6  C6 + Li+ + e-

Full Reaction:

LiC6 + CoO2   C6 + LiCoO2

Why Are Lithium-ion Batteries Better Than Other Batteries?

  • Require low maintenance 
  • Have high energy density
  • Can store more amount of energy in less amount of lithium
  • Consume less space as compared to other batteries
  • Do not leak, hence they are safe
  • Have less charging time as compared to lead-acid batteries

Advantages Of Lithium-Ion Batteries

  • Superior in Weight and Size
  • Their rate of self-discharge is much lower than for other rechargeable cells
  • Good Resilience
  • Many types of lithium ion cell available for many uses
  • Longer Lifespan
  • Low Cost
  • Do not require maintenance to ensure ongoing performance
  • Easy Installation

Disadvantages of Lithium-Ion Batteries

  • Overcharging reduces the lifespan of the battery
  • Batteries can overheat so often need to be in carry-on luggage
  • More costly to manufacture
  • Batteries have time life limits as well as cycle limits 
  • The technology is evolving and new variants are being constantly developed
  • If not used prolonged period of time, there are chances that batteries may drain. Once they drained completely, they can’t be recharged
  • Lithium ion cells are not as robust as some other rechargeable battery types 

How Much Will A Lithium-ion Battery  Setup Cost?

There is a wide range of lithium-ion batteries available in the market and their prices vary.


The total cost of setting up a solar system with batteries depends on the brand of battery you are choosing. They appear to be the best battery storage for solar. Fortunately the prices will reduce over time.


For example, if you choose a 14kWh system with Tesla battery, then it costs around $USD6,560 (dependant on location and set up). To give a rough price, a 5kW photovoltaic system with a battery ready inverter costs around $8000. If you add powerwall2 battery to this, then that will cost double to around $16,500.


We know it is difficult for the average household to invest in the order of $16,500 at one time. There are benefits over costs that make it worth the investment.

  • It will reduce your electricity bills immediately
  • You can still feed excess power to the grid if you wish
  • Enhance the value of your property
  • You need not worry about power cuts or fluctuations
  • Guaranteed performance even during black out periods
  • Save stress on the environment

Things To Consider When Choosing The Best Battery Storage for Solar Panels

There are different types of batteries in the market that look similar. They range from low quality to high quality batteries.


Their prices vary depending on the size, brand, and type of battery.


You have so many options, it almost becomes a problem to decide which one to choose.


If you are not technically a battery buyer when it comes to choosing one, then consider the following factors:

  • What do they cost?
  • How much available solar energy do you have to charge the batteries?
  • How long will the batteries last?
  • Are they good for the environment?
  • How much money will you save?
  • What is your daily usage in kWh?
  • Do you have another resource of electricity?
  • How efficient and convenient is your backup system?
  • How much maintenance will it require?
  • Can you scale it up by adding more number of batteries when required?

What Is The Future Of Lithium-Ion Batteries?

In 2018, the lithium-ion rechargeable battery celebrated 27 years in production.


It's become the best battery storage for solar panel. The lithium-ion rechargeable battery has seen sales and growth over that 27 years. It has displaced many traditional batteries for solar storage. The lithium-ion battery is gaining popularity due to its high efficiency and lifespan.


This quality of lithium will lead to the growth of electrification storage. That will happen in homes and mini-grids as part of decentralized energy systems. But we will see it also go forward in cars and buses.


Lithium is the lightest metal with the lowest reduction potential. That makes lithium batteries superior to other batteries. Also, lithium is abundant in earth deposits and we can use it for another 400 years. The battery technology is cheap compared with other battery technologies.


The most popular type of lithium battery is lithium ion battery. It has an unbeatable combination of higher energy and power density.


Recent developments in batteries reflect that the lithium batteries are continuously improving. Their improvements in energy, safety, power capability and cost mean a long future for lithium batteries. The price of lithium-ion batteries will continue to fall in real terms and its power density will increase by 20%. 


With the ongoing concern for global warming an investment in a Solar PV system is an environmental one. These changes to battery price and efficiency will further add momentum in the field for using Lithium-ion in electric vehicles and storage of solar generated power. That will mean support continues for investing in Lithium-ion as the best battery storage for solar generated power.


References:

http://www.homeandenergy.com.au/buying-tips/choosing-battery-system/

http://energyinformative.org/benefits-of-solar-panels/

https://www.solar-facts.com/batteries/battery-choice.php

http://sustainable-nano.com/2013/10/15/how-do-lithium-ion-batteries-work/

http://sinovoltaics.com/learning-center/storage/lithium-ion-batteries-used-solar-systems/

https://medium.com/solar-microgrid/battery-showdown-lead-acid-vs-lithium-ion-1d37a1998287

https://www.electrical4u.com/working-of-lead-acid-battery-lead-acid-secondary-storage-battery/

http://pvcdrom.pveducation.org/BATTERY/operlead.htm

https://circuitglobe.com/lead-acid-battery.html

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