Was reading an interesting article in today’s Financial Express on the use of Li-ion battery for solar power storage. This article was based on perspectives from Samir Sharan, CEO of Acme, the Indian solar and telecom equipment maker that is unveiling a LIB based solar storage solution called EcoGrid.

Sure, LIB has its advantages – its 4000 cycle, 10 year life (against 3-4 years from lead acid), light weight, lower space requirements and all.

The key question will of course always come down to cost.

According to the article, a typical LIB storage equipment designed for a 5 KVA load with a storage capacity of 6.6 kWh would cost about Rs 3.5 lacs.

I thought I’d try computing the costs using these data sets.

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Firstly, the capital cost.

Rs 3.5 lacs as capital cost is a bit too high for most of us in the residential sector, assuming we have a 5 KVA load. This alone can be a huge put off.

But what would be also be interesting to know is the variable cost (per kWh) that gets added if we use batteries.

Let us do this calculation for the above data.

The raw nameplate energy cost comes to about Rs 50000 per kWh (3,50,000/6.6), or about $800/kWh. This is much higher than what I hear as cost in the market, which is about $300/kWh for Li-ion battery.

Now, you might be interested in knowing what would be the extra you would be spending for every unit of energy spent using the battery during its lifetime.

A 6.6 kWh battery that will last 4000 cycles would have in all supplied, a max of 26400 kWh (I am being generous in not assuming any energy losses from battery). So, you are dishing out Rs 3,50,000 to get 26400 kWh. That would mean you are dishing out Rs 13.25 per kWh used, over the lifetime.

Sounds too high once again.

The data I have from the market says that the nameplate energy cost should be about Rs 20,000 /kWh for LIB, which will mean, I spend an additional Rs 5 for ever unit I use through the battery. Still a lot of money, but much less than Rs 13.25.

Can someone respond why the EcoGrid storage should cost two and a half times that for a conventional LIB storage?

By the way, for those interested, costs for deep cycle lead acid batteries, the ones that are typically used for solar power storage, should cost less than $150 per kWh, which means about Rs 10000/kWh nameplate and about Rs 2.5 /kWh as the expense for me for every unit spent using the battery.

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