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Cost Per Unit kWh of a Battery Over Its Life

10/12/2016 2:40 PM

When we are comparing alternates, most of the times we are required to choose the one thats cheaper and provides the same value. If we are comparing diesel generator with a battery bank, we need do the same maths. How can we determine the cost per unit energy (kWh) the battery provides over its life?

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#1

Re: Cost per unit kWh of a Battery over its life.

10/12/2016 2:42 PM

You use a search engine, just like anybody here would.

This is NOT a free reference service.

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#4
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Re: Cost per unit kWh of a Battery over its life.

10/12/2016 9:52 PM

Lyn.. Perhaps you are too old, smart or jaded to care about other people's simple questions..

I don't think you represent the majority with your flip relpies. I and others have tried to express this over the years, but perhaps you are too old, smart or jaded to care.

I on the otherhand love questions like this. Can you please keep your non replies to yourself and allow others to discover and discuss whatever it is they want to without sounding like a rusty old crank?

Cr4 would be a better place if you would shut your yap.

Why the hell do you think shutting down "trivial" discussion is your birthright/deathright?

Marvin k mooney will you please go now?

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#5
In reply to #4

Re: Cost per unit kWh of a Battery over its life.

10/12/2016 10:17 PM

It's an interesting problem you have, ...but it's not that interesting? Yeah, right

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#6
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Re: Cost per unit kWh of a Battery over its life.

10/12/2016 10:22 PM

A smart man said that.. Who are you?

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#2

Re: Cost per unit kWh of a Battery over its life.

10/12/2016 2:46 PM

Lead acid batteries look at the warranty...How they are maintained can make a big difference...

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#7
In reply to #2

Re: Cost per unit kWh of a Battery over its life.

10/13/2016 1:31 AM

I havent read warranty, but I will tell you what I have read. The Cycles of a battery depend on DOD and Operating Temperature. For every 8 deg rise in operating temp, the life reduces to half. Temperature vary throughout the year, so is there a way we can predict the the cycles for this variation in temperature. And most of the times its partial discharge, like the battery is only used for like 20% and then goes back to charging, so how can we how many cycles we have completed on partial discharge.

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#17
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Re: Cost per unit kWh of a Battery over its life.

11/20/2016 4:15 PM

Predicting the temperature could be easy in theory but not in practice.

You can get daily maximum/minimum daily temperatures for a "typical" year from your national meteorology office or even a local school which is in a national observation scheme. Or perhaps, you take a "hottest year in 5 years" average (climate data may give max/min monthly temperatures only exceeded one year in 5 or similar). I see you are in Pakistan & I know your "met. office" has a website. You can take the mean as half way between max & min.

If it is a large capacity battery of conventional type e.g. lead acid, a good guess is that it follows the mean monthly ambient temperature. If it were a small battery, lithium, high surface area to weight, it may follow a lot of the daily variation, which is bad mechanically - but chemically (that 2/1 life variation per 8 'C is chemical) it is the mean that matters.

One has no idea of the temperature of the battery "building/enclosure" relative to outside climate. There is lots of building design data. North side of a building better than south, beware sun and windows.

If the battery produces little heat, putting the battery in a cave or a hole in the ground 1 meter deep back-filled with bags of soil should get "mean annual ambient temperature" (There are problems with water flooding & gas from batteries, but most are sealed and "there is no free lunch") - this will beat putting the battery in an unspecified building which may be a galvanised iron shed in the sun.

Charge/discharge cycle number & depth cannot be attempted without discharge and charge profiles for a particular load and charging means. Ireland may be a prime location for wind power but it still gets windless days every year. Having an automatic over-discharge protection is essential - reversing cells in a string kills them - making theoretical life estimates worthless.

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#3

Re: Cost Per Unit kWh of a Battery Over Its Life

10/12/2016 9:40 PM

What do your lecture notes say? Or, did you not take any?

I always hated to take tests based on lecture notes, they'll bite you in the arse every time!

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#8

Re: Cost Per Unit kWh of a Battery Over Its Life

10/13/2016 2:54 AM

Purchase price, depreciation, maintenance and recycle/disposal costs versus used kWh comes to mind.

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#9

Re: Cost Per Unit kWh of a Battery Over Its Life

10/13/2016 5:18 AM

A rechargeable battery does not "provide" any energy over its life - it just stores energy you put in when you charge it, and releases it back to the load. I don't see any way you can sensibly make such a comparison.

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#16
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Re: Cost Per Unit kWh of a Battery Over Its Life

11/11/2016 11:57 AM

Well, technically from the point of purchase (if purchased in a charged condition), then it would, but the kWh output would be minuscule compared with the energy stored and then released over the lifetime of such a battery.

Now that we have that detail out of the way, consider that it matters as to whether the battery bank is to be stationary, and what can be done to make the environment around the battery as nearly ideal as can be. If non-stationary, then you need the best shallow cycle lead-acid you can buy, I suppose. It really depends on how many amp-hours you need, what the peak amp delivery is expected to be, and how slowly it can be recharged.

If weight is any consideration, then there are manufacturers in China who are eager to sell large lots of various lithium ion battery banks utilized for various purposes.

If deep cycling were a concern (and you have already stated that it is not), then you might consider Edison batteries (zinc-air), as these seem to be making sort of a resurgence.

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#10

Re: Cost Per Unit kWh of a Battery Over Its Life

10/13/2016 6:29 AM

If it's a secondary energy source, such as a lead acid battery for example, then it doesn't have a cost per kWh because the energy cost comes with the primary energy source that is used to charge it.

If it is a primary battery, such as a non-rechargeable zinc carbon battery for example, then the cost per kWh is simple arithmetic based upon the purchase price, the disposal cost, and the amount of energy that comes out of it.

A better-defined question is needed here.

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#11
In reply to #10

Re: Cost Per Unit kWh of a Battery Over Its Life

10/13/2016 6:58 AM

I assumed OP was talking about rechargeables, as he referred to a "battery bank" and was asking for a comparison with a DG.

I can't imagine any situation where non-rechargeables would be used in place of a DG.

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#13
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Re: Cost Per Unit kWh of a Battery Over Its Life

10/14/2016 12:51 PM

I like your #9.

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#12

Re: Cost Per Unit kWh of a Battery Over Its Life

10/13/2016 7:40 PM

A real world situation where a DG is an option and a BB is a consideration would likely have peak power times of the work day where the cost of operating the DG is the best option when compared to solar for example.

The smaller the load used during off peak hours with a BB would be directly proportionate to the savings when compared to a DG.

As the size of the BB grows so does the cost of the gear to distribute and maintain.

It's an interesting question as there are so many variables.

It's one of those situations where the more you spend to do it right the less you spend to maintain in the long run.

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#14

Re: Cost Per Unit kWh of a Battery Over Its Life

10/15/2016 12:10 AM

You calculate the TCO (Total Cost of Ownership) for each alternative. The TCO is comprised of many parts and you will have to determine which are important (or even calculable) for your particular analysis. Since both alternatives are similar it should be a relatively easy exercise.

I would start with the major costs and drill down from there; these would include: IC (Initial Cost), O&M (Operation & Maintenance), FC (Fuel Cost), DC (Disposal Cost), RC (Replacement Cost), etc.; remember that any of these can be broken further into other CCs (Cost Centers). For example, IC can include not only the cost of the equipment, but also the cost of digging the raw materials out of the earth, refining them, the environmental impact of pollution and the cost of site remediation, etc., etc.

Remember to keep the units consistent so that everything can be directly compared. More than likely your professor will grade your paper by the amount of research and the depth of detail in your analysis. You could start with some books on PM (Project Management) and CA (Cost Accounting).

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#15

Re: Cost Per Unit kWh of a Battery Over Its Life

10/17/2016 10:17 PM

I have read the answers to your post, and agree with most of the points made. But there's one aspect that occurs to me. Clearly batteries do not provide energy, they only store it.

An important consideration is the lost energy, the charge - discharge efficiency, which you can normalize to the maximum kWh capacity. This is the battery's charge efficiency. The rating can be further characterized by the charging rate, e.g. C/10, etc.

The figure shows the variation as a function of charging current, and also, significantly, as a function of temperature. This is a lead-acid battery, which suffers at high temperatures. But their 'specsmanship' graph doesn't show below freezing, which is a killer for these batteries.

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