# When Will Solar Batteries Become Economical?

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Registered Users Posts: 3,810 ✭✭
It's always the same problem: You save energy but the electricity bills are still getting more expensive. Luckily, there is a solution: Solar power can be generated in Germany for 12 cents per kilowatt hour. In contrast, utilities currently charge an average of 25 cents for domestic electricity. What better reason to invest into your own photovoltaic system? Solar storage systems can increase on-site consumption by up to 70 percent. They absorb surplus solar power and pass on the energy as required — expensive grid power is hardly necessary. This makes the systems very attractive for consumers: According to an EuPD Research survey, almost 90 percent of solar operators are already thinking about buying an additional storage system.

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• Solar Expert Posts: 3,123 ✭✭✭✭
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Re: When Will Solar Batteries Become Economical?
During its cycle life, the battery has a capacity of around 30,000 kilowatt hours. At €6,300 for the system, storage costs come to 21 cents per kilowatt hour. If you add the 12 cents it costs to produce power on-site, the total cost comes to 33 cents. This sum is considerably higher than the current domestic electricity cost of 25 cents — meaning the system is not economical. Modern lithium-ion batteries offer even less value for money, according to Sauer’s calculations. Storage costs alone come to at least 35 cents for current systems.

That is a lot lower battery cost per KwH than anybody here or on other forums I read has even come close to.
Economies of scale, or just wholesale price on the batteries?
SMA SB 3000, old BP panels.
• Solar Expert Posts: 1,571 ✭✭
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Re: When Will Solar Batteries Become Economical?

Running a similar calculation for my forklift batts:
800Ah x 50% DoD x 80% efficiency = 320Ah @ 48V = 15.3kWh x 3000 cycles = 46 080kWh total throughout it's life. Paid 3500 euros for them, so that's about 6.5 cents/kWh (8.5 US cents).
That's assuming that they'll last 3000 cycles at 50% DoD. They're actually rated for 1500 cycles at 80% DoD, so using that instead it works out to 9 cents/kWh.
• Solar Expert Posts: 1,913 ✭✭
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Re: When Will Solar Batteries Become Economical?
inetdog wrote: »
That is a lot lower battery cost per KwH than anybody here or on other forums I read has even come close to.
Economies of scale, or just wholesale price on the batteries?

Mine, if work as advertized, will cost \$0.17/kWh. Surrettes 5000, by my calculation, are \$0.14/kWh.

However, their calculation is not correct because part of energy that is put into batteries is lost. To get 1kWh back, you need to put in, say 1.25kWh.

Solar power (as coming from panels) at today's prices is considerably less than \$0.12/kWh.
• Solar Expert Posts: 6,005 ✭✭✭✭✭
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Re: When Will Solar Batteries Become Economical?
inetdog wrote: »
That is a lot lower battery cost per KwH than anybody here or on other forums I read has even come close to.
Economies of scale, or just wholesale price on the batteries?

Gosh, I can't do the math for the amount stored, but between the amount stored and used directly, my 800Ah 24v battery (\$2525) with a life span of 15 years should allow my use of 100 days of @13Kwh and 265 days of 4-5 Kwh so (1300 + 1000) x 15 =34,500 Kwh or about 7 cents a Kwh, and it can do more over fall and winter, just don't need it at this point.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Solar Expert Posts: 6,005 ✭✭✭✭✭
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Re: When Will Solar Batteries Become Economical?
NorthGuy wrote: »
Solar power (as coming from panels) at today's prices is considerably less than \$0.12/kWh.

In many places, Germany is not a bright and sunny place, just forward thinking... though it is likely produced using older numbers Germany is almost akin to setting up solar in western Oregon, in general.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Solar Expert Posts: 1,571 ✭✭
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Re: When Will Solar Batteries Become Economical?
NorthGuy wrote: »
However, their calculation is not correct because part of energy that is put into batteries is lost. To get 1kWh back, you need to put in, say 1.25kWh.

In the article they say that they factor this in using an 80% efficiency value. Perhaps this is a bit optimistic, because they don't factor in losses in the charger and inverter.
• Banned Posts: 17,615 ✭✭✭
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Re: When Will Solar Batteries Become Economical?

Couple-three points:

1). Germany is at the same latitude as BC and the climate is similar, so they get the same sun as we do.

2). There's always a "sweet spot" for cycling batteries where you get the best value in kW hours. Most people don't manage this. Too little DOD and you've wasted your money on big capacity. Too much DOD and the lifespan is short. How they'd balance this in a grid application I have no idea.

3). Some of the power used by grid will be "driven directly" by the PV's the same as us off-gridders taking advantage of full batteries and sunshine to improve the over-all efficiency. Again, a load management issue.

So I would suspect that in order to get the efficiency of the batteries (and thus cost per kW hour) up my brother-in-law is going to have to write some new software (inside joke).
• Solar Expert Posts: 1,913 ✭✭
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Re: When Will Solar Batteries Become Economical?
stephendv wrote: »
In the article they say that they factor this in using an 80% efficiency value. Perhaps this is a bit optimistic, because they don't factor in losses in the charger and inverter.

The way they do it is not correct. Battery inefficiency does not shorten its life, and therefore doesn't increase the cost of the battery. Rather, it increases the amount of energy. For example, battery's storage cost is \$0.20, and the cost of energy is \$0.12. If battery efficiency is 80%, the extra cost of the inefficiency is \$0.12/0.8 - \$0.12 = \$0.03, not \$0.20/0.8 - \$0.20 = \$0.05.

Also, some energy goes directly to loads and batteries are not involved at all. Especially, all the energy produced during cloudy weather that they may have in Germany most of the time, will go directly to load. You need to figure in the inverter efficiency too.

As a result, their estimate, even assuming that \$0.12 price of solar is correct, is exaggerated.
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Re: When Will Solar Batteries Become Economical?

I believe there will be more cost effective and environmentally friendly storage batteries available soon. I think it's only a matter of time before the lead acid battery is eventually replaced or modified to something better. Interesting article here:

http://www.renewableenergyworld.com/rea/news/article/2013/01/energy-storage-wars-who-will-win-the-race-to-scale