Summary: How can you use solar power when there is no sunlight? By storing the power generated during sunshine hours in batteries.

Does solar power need battery storage? If yes, under what circumstances? What types of batteries are used for solar power plants today? And how much does battery storage cost?

In circumstances where solar power needs to be used during times when the sun does not shine, it is usually stored in batteries. These are the same batteries used for other applications, and could be based on lead-acid, lithium-ion etc. However, only some select types of batteries within the available range are optimal for solar power plants owing to the specific aspects of solar power generation and use.

Batteries, by storing electricity, make renewable energy sources more reliable and “firm” than they would be otherwise

Batteries (and storage in general) is considered the holy grail of solar energy and other forms of renewable energy, as they overcome one of the key bottlenecks of renewable sources – their intermittent nature. By storing the electricity generated, batteries can thus make renewable energy sources more reliable and “firm”.

However, batteries are quite expensive to be used as storage media for large solar farms or any other renewable energy farm.

Questions from the curious cat

What types of batteries are used for storing solar power?

The most suitable type of battery for solar power is the deep-cycle lead acid battery.  A deep-cycle battery is designed to be discharged up to 80% during its use and then recharged repeatedly.

As you can visualize, solar power systems will need these deep cycle batteries as there will be many occasions when you will need to draw power from the battery for extended durations. This will require batteries that can withstand deep discharges many times over.

Are the batteries used for solar the same as the ones used for other applications?

Yes, fundamentally the batteries used for solar power are the same used for other storage applications. However, some types of batteries (such as deep cycle batteries), are more suitable for solar power.

To what extent can I use batteries for my rooftop solar power plant?

If you live in locations where grid power is unreliable and you wish to have solar as a reliable source of power, you will need batteries.

However, batteries are expensive, and will continue to remain so for the foreseeable future. Hence, while you certainly can consider using batteries for your solar power system, you will need to strike a balance between cost and reliable power.

To what extent can batteries be used for large grid connected power plants?

As of 2014, use of batteries for large solar power plants is infeasible, mainly owing to the cost of the batteries over the lifecycle of the solar farm. There are a few demonstration projects that are experimenting with the use of batteries, but we do not expect batteries to play a significant role in large scale solar farms until at least 2020.

Are there some exciting battery breakthroughs that can significantly increase the use of batteries in solar power plants?

Let us cut a long story short. There is a lot of noise, and every day you will hear some exciting announcements of how a new type of battery technology will forever change solar power.

But, other than incremental changes to existing battery technologies, we do not expect any of these “exciting announcements” to make it to the commercial world anytime soon.

How much more will solar power cost if batteries are used?

When used in residential solar power systems, the use of batteries will increase the cost of solar power between 25-75%, depending on the extent to which batteries are used.


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