Author Topic: EEVblog #1086 - 5 year Solar Power Payback?  (Read 10663 times)

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Offline orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #25 on: May 24, 2018, 01:00:24 pm »
They are not designed for deep daily discharge like is needed in my case.

So LiPo would be more cost effective vs an oversized SLA bank that doesn't have to take the last life breath out every day?
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #26 on: May 24, 2018, 06:56:02 pm »
Yes, Lithium is now more cost effective than Pb on the long run. In fact PbGel is the worst cost for daily storage !
A small comparative :
Battery type       Lifetime          Battery energy price     Storage price (only battery cost)

Pb Battery Wet        2000 cycles       0,13€/Wh      0.065€/kWh  <- Monthly Maintenance needed, replacement time is 6 Years assuming 1cycle/day.
Pb Battery Gel         1000 cycles       0,27€/Wh      0.270€/kWh  <- extremely bad storage cost, very frequent replacement !!
Lithium LiFePo4      6000 cycles       0,26€/Wh      0.043€/kWh  <- best storage cost ! 18 Years lifetime.
LiFePo4 high end   8000 cycles       0,39€/Wh      0.048€/kWh  <- OK, especially if you want a longer replacement cycle
« Last Edit: May 24, 2018, 07:30:34 pm by f4eru »
 
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Offline metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #27 on: May 24, 2018, 07:54:23 pm »
At 8min, if 19.95MWh was produced and 7.238MWh consumed, how is that 24.7% of solar produced was used?
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #28 on: May 24, 2018, 08:14:35 pm »
Quote
At 8min, if 19.95MWh was produced and 7.238MWh consumed, how is that 24.7% of solar produced was used?
Easy.
100% of the power produced was used : 24,7% by Dave, 75,6% by someone else
Dave consumed 4.9 MWh of his own production only. The rest 2.31 MWh was consumed by dave off the grid when he didn't produce (at night)
« Last Edit: May 24, 2018, 08:16:32 pm by f4eru »
 

Online nctnico

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #29 on: May 24, 2018, 08:15:22 pm »
dave why you dont build your own battery,to store  all that electricity generated by solar panels?
you could use old smartphones  batteries sent by your viewers,laptop batteries
or  cheap lithium batteries made in china.
it would be any  intresting video,if you decided to make it your own instead..
It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.
Besides that using random cells is asking for trouble. The idea of using discarded cells isn't new but it will take carefull matching and measuring of the cells to see from which ones you can built a reliable and (more important) safe battery pack. However I'm quite sure we will see batteries for residential (I'm avoiding the word home here because the batteries could also be located at a nearby sub station) storage of electricity becoming more affordable in the future. If a larger part of the electricity supply is going to depend on wind and solar some kind of storage is a requirement to make it all work.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline rrinker

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #30 on: May 24, 2018, 08:26:14 pm »
 Yes, about the LAST thing I'd want in my home is a wall full of potentially dodgy used batteries storing that kind of energy. At least if a commercial system burns your house down you have some recourse. Build it yourself with questionable components and you're completely on your own.
 

Offline hbpowerwall

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #31 on: May 24, 2018, 11:56:37 pm »


It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.


I joined instead of stalking just to say - 'Yes' But it bloody works!
 

Online Brumby

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #32 on: May 25, 2018, 01:58:56 am »
We have no quarrel with the fact that it works ... just that (as I understand it) Dave isn't really set up to put the time into such a project.
 

Offline hbpowerwall

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #33 on: May 25, 2018, 06:50:41 am »
Not many do - labor of love for sure
 

Offline orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #34 on: May 25, 2018, 12:46:22 pm »
So if a lipo in this use case can get ~5k+ cycles, why the hell does my phone battery become utter crap in 2yrs or less?
 

Offline grythumn

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #35 on: May 25, 2018, 01:59:16 pm »
Different chemistries, different battery management. If you limit depth of discharge and charging voltage, you can significantly increase the number of cycles a cell is good for. If you use the full capacity, they're only good for a few hundred cycles.

https://www.powerstream.com/lithium-ion-charge-voltage.htm

-R C
 

Offline metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #36 on: May 25, 2018, 02:44:28 pm »
Quote
At 8min, if 19.95MWh was produced and 7.238MWh consumed, how is that 24.7% of solar produced was used?
Easy.
100% of the power produced was used : 24,7% by Dave, 75,6% by someone else
Dave consumed 4.9 MWh of his own production only. The rest 2.31 MWh was consumed by dave off the grid when he didn't produce (at night)

But that's not what he said. He consumed 7.238MWh of his own solar production, and he also consumed 22.043MWh from the grid. So he consumed a total of 29.281MWh.

I imagine 100% of his solar production was used, some by Dave and some by the grid. If 19.950MWh was produced and Dave only consumed 7.238MWh, he exported 12.712MWh. 36.3% of solar produced was used [directly by Dave].

I see what he means now.
24.7% of his "total energy use" was directly supplied by solar (7.238/29.281).

 

Offline rrinker

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #37 on: May 25, 2018, 03:33:29 pm »
Different chemistries, different battery management. If you limit depth of discharge and charging voltage, you can significantly increase the number of cycles a cell is good for. If you use the full capacity, they're only good for a few hundred cycles.

https://www.powerstream.com/lithium-ion-charge-voltage.htm

-R C

Exactly - mine's going on 5 (maybe 4 /2 - I never buy these things when first released) years old (iPhone 5S) and the battery life has not noticeably diminished - but I never let it discharge to the point of the phone shutting down, and since I use it to play music in my car, it gets plugged in constantly whenever I drive somewhere. No deep cycling = nice long life.

Although a power wall to buffer solar production is almost certainly going to be a deep cycle application. Unless you make it of an impractical size that is say 50% greater than your average overnight consumption.
 

Offline orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #38 on: May 25, 2018, 03:52:04 pm »
Although a power wall to buffer solar production is almost certainly going to be a deep cycle application.

Dimensions
L x W x D: 44" x 29" x 5.5"

From their own internal images of it, the top 1/3rd seems to be the inverter/cooling/wiring.  So that only leaves the bottom 2/3rds for the battery pack.  So ~29"x29"x5" to pack in 13.5kWh of capacity.  Sure hope $6.6K per unit wouldn't need to be swapped out every couple years.

So some ruff math (flawed as my understanding may be)

29x29x5.5 = 4625.5in^3 or ~2.7ft^3 area for battery

Looking on the internets looks like lipo is ~230wh/l

2.7ft^3 = 76.5L
230wh/l * 76.5L = ~17.6kWh

So to suck out the 13.5kWh you must be drawing ~75% of the total capacity everyday.  That extra 25% capacity and the chemistry gets you to the 5K cycles mark?

« Last Edit: May 25, 2018, 04:27:58 pm by orion242 »
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #39 on: May 25, 2018, 04:57:09 pm »
An example of "DOD" graph:

For the phone batteries, the problem comes from bad thermal and charge management. A phone battery runs hot and is often charged to 100%.
For lithium batteries to last, charge them to only 85-90% SOC.
« Last Edit: May 25, 2018, 05:11:56 pm by f4eru »
 

Offline orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #40 on: May 25, 2018, 05:06:42 pm »
Yea that's going to be a massive amount of SLAs to get to 5K cycles.

Flip side, 5K cycles from a PW might be a bit optimistic if its 75% DOD to get the rated capacity.
 

Offline NANDBlog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #41 on: May 26, 2018, 09:49:07 pm »
dave why you dont build your own battery,to store  all that electricity generated by solar panels?
you could use old smartphones  batteries sent by your viewers,laptop batteries
or  cheap lithium batteries made in china.
it would be any  intresting video,if you decided to make it your own instead..
It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.
Besides that using random cells is asking for trouble. The idea of using discarded cells isn't new but it will take carefull matching and measuring of the cells to see from which ones you can built a reliable and (more important) safe battery pack. However I'm quite sure we will see batteries for residential (I'm avoiding the word home here because the batteries could also be located at a nearby sub station) storage of electricity becoming more affordable in the future. If a larger part of the electricity supply is going to depend on wind and solar some kind of storage is a requirement to make it all work.
I really hope not. I'm saying this after working with 50Ah Li-Ion batteries, those things are scary. When they fail, they fail big, with gas coming out of them and with a fire that you cannot put out just like that. Besides, It is the government's job to supply continuous uninterrupted power to the people (and keep a police force and repair the roads), not ours. Storage is not like the generation, it can be much more efficiently done if it is centralized.
 

Offline PaulKennett

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #42 on: May 27, 2018, 08:52:19 am »
> Besides that using random cells is asking for trouble.

Speaking as a DIY powerwaller... I think that mischaracterises what we do.

We gather random cells - and then spend a lot of time weeding out the high ESR and low capacity cells - in an effort to use only "good" cells.

And yes - that does take a lot of time. But it's an enjoyable hobby* that usually ends up producing a useful product.

Fun, satisfying and rewarding. For me part of the satisfaction comes from using something that others have thrown away.

But - if you don't want your home energy project to be a hobby then it's much better to just buy a commercial solution.

Cheers, Paul
*Hobby: an activity done regularly in one's leisure time for pleasure.
 

Offline b_force

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #43 on: May 27, 2018, 01:35:52 pm »
I think you also need to look at how many people keep their homes =>10yrs.  If most move under that, there is little sense in installing it.

That logic seems a bit flawed. Presumably, having a lower expected electricity bill would be a value add for the new owner as well, so it should increase the resell value of the home.
Property agents say few buyers see value in solar panels, so why would they see value in battery packs?
I think that really depends were you live.
Enough places were solar panels are actually a huge plus for the value.

Very interesting video.
Yes, a lot has changed the last 10 years
Even the inverters are not so expensive nowadays.
A battery pack is not really going to be efficient, but I think it will work great in places with a lot of outages.
Just came back from a trip around Spain and some places have an outage almost every other week.
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Online Nauris

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #44 on: May 27, 2018, 07:24:57 pm »
Yea that's going to be a massive amount of SLAs to get to 5K cycles.
There are also more premium lead acid batteries out there. Like Trojan industrial solar line as in the graph below. About 3600 cycles at 50% DoD.
 

Offline NANDBlog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #45 on: May 27, 2018, 08:03:56 pm »
Yea that's going to be a massive amount of SLAs to get to 5K cycles.
There are also more premium lead acid batteries out there. Like Trojan industrial solar line as in the graph below. About 3600 cycles at 50% DoD.
If the feed-in tariff is high, then no battery technology is viable, because it is too expensive. If the feed-in tariff is low, then other technologies would provide much better alternative than batteries. Imagine a mini power to gas plant at the backyard, generating methane from water and CO2 from the air. If you sink a tank in the garden, you have practically unlimited capacity, and you can just offset the lower efficiency with more solar panels.
It is really not rocket science, just some more money should be put into P2G and CHP (combined heat and power). If we would spend 1/10 of the money we spent on nuclear research, it would have been a solved problem. But you know, it cannot be used as a weapon.
 

Offline mortderire

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #46 on: May 27, 2018, 08:40:44 pm »
Loved the video - much kudos.

Sobering that if Dave can't make it pay in NSW, Auz with buckets of sunshine and some compensation for exported energy. I have pretty much zero chance here in not so sunny, Northern Europe with zero compensation for exporting energy.

I understand now that the key to the system being economical or not, is reasonable compensation for exporting energy. Adding a storage system is prohibitively expensive - appears to only have the effect of extending the period over which the cost of the system has to be paid down, without any guarantee the system is going to last that long without additional investment.

However some reasonable compensation from the power provider for exporting energy into the grid, means there is no need to invest in an expensive storage system - meaning a return on investment might be achievable for people like Dave, i.e. with buckets of sunshine. This is turns into a pretty simple formula of :-

1. How much does the system cost.
2. How much am I likely to generate.
3. How much will I be paid for what I generate.
versus
4. My overall energy requirements.     


It remains less certain for those of us who don't get guaranteed sunshine.
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #47 on: May 29, 2018, 07:43:59 am »
Quote
If the feed-in tariff is high, then no battery technology is viable, because it is too expensive.
I don't think so.

There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.

Both could make economic sense, or could be uninteresting, depending on many local factors.
But the cases where it makes economical sense are probably still quite niche today.

But two factors will change that :
- Sinking battery costs : Li. Batteries prices drop 30%/Year
- Scaling up of EVs : the adoption of EVs doubles every year, and those can and will probably be reprogrammed as grid stabilization batteries.

In a few years, batteries will change the landscape of electricity pricing and costs.
« Last Edit: May 29, 2018, 07:48:20 am by f4eru »
 

Online Fungus

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #48 on: May 29, 2018, 08:31:55 am »
There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.

And maybe (3) If you own an electric car that needs charging at night.
 

Offline b_force

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #49 on: May 29, 2018, 11:23:37 am »
There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.

And maybe (3) If you own an electric car that needs charging at night.
And as I mentioned above (4) when you have many outages/unstable electricity network.
Maybe even (5) when you need electricity on a place where there is no standard connection (yet)
The costs of getting grid power can sometimes pretty significant.
"If you can't explain it simply (or at all), you don't understand it well enough." A. Einstein

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