Doctrine on the Province of Crazy in the Solar Community - Battery Edition

[BillSunGen]

I need help (If that isn't clear from the subject/topic. I will probably fail in living up to the headline so feel free to stop reading here.) You have killed my dreams. The batteries killed my free power, endless perpetual motion, and rainbows and unicorns. Since you have insisted on killing my dreams and forcing me to deal with reality and physics (which are not always related) I hope it is not too much to ask that you help me readjust my mindset to how I need to think about this system.

--- Background on intro and 'normal' grid tied system here ----
For background you can see my intro

https://www.solarpaneltalk.com/forum/solar-panel-talk-information/new-members-please-introduce-yourselves-here/378531-intro-from-virginia

and the grid tied discussion.

https://www.solarpaneltalk.com/forum/solar-panels-for-home/solar-panels-for-your-home/378610-grid-tied-system-design

The real quick summary.
- I am going to be building a 10kW system, grid tied of some sort.
- Dominion makes it (more) uneconomical to install > 10kW .
- I value the ability to be offgrid during disasters or other unplanned outages
- I value the potential hedge on paying for energy now against rising prices in the future
- I value learning about managing offgrid power, now rather than during a disaster
- I understand that at current prices and assuming power stays in historical ranges that installing an offgrid system will be more $ per watt than on grid.
- I have many marginal power uses that I minimize now but could be used to get value from the offgrid times of over production, like a dump load. These include water pumping, additional pool filtering, pool heating, more ac, fans during summer.

My issue.
I would like to avoid the dominion penalty and limits by setting up a separate off grid portion of panels. Between current solar credits and variable costs (a large part of the variable being my time. It is a lot easier to order an additional panel, length of railing, and wire together now than it would be to start over and build a second system in the future) it seemed to make sense to build it at the same time. In my imaginary world this is an additional 10kW offgrid system that would approximately balance current power consumption. In this magical world all of the panels would be installed at the same time for full capacity and loads would be transferred over to the off grid part of the system over time as power generating and consumption patterns could handle. I would start with a small battery bank, enough to run some minor minimum variation load (freezer maybe) overnight then add capacity over time.

Did I mention that batteries hate me? Well the feeling is mutual now. This is where things start to fall apart. You have seen this movie before... So Lead Acid batteries and I don't get along. I have an electric mower, love it, but have killed two batteries in approximately the same number of seasons. They want attention and I can get distracted. I was well aware of the fact that you have to baby them but can say after reading these forums I had no idea what that meant (DoD, charge rates etc). I probably now know enough to take care of those electric mower batteries properly but they certainly didn't come with the right tools or information. So started looking at other battery type options. Running across Nickel Iron seemed like the perfect battery for me. Long lasting and able to handle some abuse would work great in an under sized system. The chemistry made sense and I don't mind paying more up front if they are going to last for the long term. Pricing based on what I found was high but could work (found the Chinese direct first, the cost to import from american suppliers or made in america even with the assumed long life are hard to justify but the same it true of all batteries it seems...). As the batteries are the driver of the uneconomical side of the equation, it is easier to justify a single up front payment as 'insurance' for the above offgrid benefits if they were going to last for the life of the system. If they have to be replaced every 5 years it is a lot less valuable for long term insurance as future costs are unknown.

So in my mind I was working from a given pool of energy (10 kW rated solar panels) and sized the system to match with dual charge controllers(Classic 150), likely feeding into Magnum dual inverters and the battery bank. In my dream world this works because the charge controllers would manage the flow of energy to the batteries and take into account draw from the inverters so that the imbalance between supply (panels) and battery bank (minimum buffer). With high production and high demand it would work like a bypass pipe between the panels, inverters and demand so that the batteries would only handle buffering and loads would be adjusted to available power (i.e. run when it is sunny and only minor loads at night). That picture doesn't work as it is more like a giant pipe of energy that is going to run right though the batteries to the inverter and blow them up. Even if they didn't burn up, with battery chemistry you can't add new batteries later so the plan to build over time doesn't work anyway.

So how should I approach this problem? Is the battery the limiting factor, pick a $$$ for a (lithium xyz, forklift, build my own NiFe...) then back calculate to an appropriately sized array based on charging and add load over time until target DoD is hit. Then if I find that there is a need for more capacity later add a second bank with different battery type and separate load. Or do I put the panels up but just connect the correct size for batteries with the hope that next round can increase capacity. Give up and start building my own methane reactor out of compost...

As you can see my thoughts are crazy enough as it is. I believe I have covered most if not all of the fallacies that you all run across regularly in the battery subject. Feel free to direct me to other mistakes that I can add to my doctrine. Or if you want, maybe push me in the right direction on how you would think about it. Any other crazy ideas would be perfectly rational to me.

[Mike90250]

If you are expecting 1-4 days blackout, forget batteries and use a generator.

If you think the fuel for outages will not last as long as you expect the outage to last, then (and only then) consider batteries.

At the end of this month, I'm doing the electrolyte changeout on my NiFe bank, it should take me a week or so to complete. I'll let everyone know in a new thread, how that went.
Mixing and handling 200 gallons of nasty chemicals (lye) 100 gal of new, 100gal old. Not going to be fun, but have to do it, or loose battery bank to Co2 poisoning ( an expected occurrence)

If you know what your critical base loads are, you can size your battery bank (don't forget, you will still need a backup generator anyway), and you can use your string inverter's
PV array and switch the feed to a 600V charge controller if the grid fails you.

[bcroe]

Just a few opinions
1. Batteries are for when there is no other way (off grid)
2. Solar is an awful backup system
3. The energy capacity of batteries is tiny compared to on grid situations
4. A generator is a great backup system
5. Hardly anyone really needs non interruptable power

So physics doesn't always agree with reality? Bruce Roe

[jflorey2]

I would like to avoid the dominion penalty and limits by setting up a separate off grid portion of panels.

That's easy. You can get a small system and either use it to maintain a lead acid battery bank or an off the shelf (i.e. BMS included) LiFePO4 system. It will be $$$ but:

1) it gives you a small backup system
2) you can play with it (and potentially destroy the batteries) without affecting your main system - and thus you'll learn a lot about solar.
3) if you have the $$$ and you want to do it - knock yourself out.

It will NOT be cost effective.

If you want a backup beyond that, consider an inverter that can take a generator input (i.e. an inverter/charger) and then get a generator for your 'main' backup. The batteries then let you shut down for periods of time when power consumption is at a minimum. This saves fuel, wear and tear and noise.

As an alternative, spec out SMA inverters that have the secure power feature, and use them for 'backup' power. With two SB5.0's you'd get 4000 watts of backup power. Unreliable of course (a single cloud will shut you down) but it's enough to charge up a cheapo UPS for backup power to keep cellphones charged and whatnot.

[Sunking]

So answer one question please. Why would you want to pay 5 to 100 times more for power?

You do understand that is exactly what you are asking for taking anything off-grid. Why 5 to 100 times more? It has to do with the way you would use the batteries. If you utilize all the power the off0grid system can generate in a day (impossible), you can get the cost to to 5 to 10 times more. But if used infrequently like power outages, can be 100 times more than buying or generating power.

If you use the batteries every day, you can get maybe 1000 cycles or 3 years out of them before needing replaced.. Or use them a few times in 3 to 5 years before they need to be replaced. Batteries, physics, and economics are reality and you cannot escape it. No matter what Hilary told you.

So answer the question. Why do you want to pay 5 to 100 times more for power? Only a democrat would make that choice. One more thing to bust your bubble. Because off grid is terrible inefficient, has a negative EROI (Energy Return on Investment) on top of ROI. Means what it sounds like; the amount of energy to make all the components will be more than the system can generate over it life time. It makes you a heavier polluter on top of getting deep into your wallet. Batteries are expensive and inefficient. Takes a lot of energy to make batteries.

[BillSunGen]

First, just to be super clear, you don''t have to talk me out of a 10 kW offgrid battery only power system. You (maybe not ''you'' in the sense of any single person but the old threads here) already did that! I was summarizing a lot of reading and my thinking of what got me here. Maybe it will help someone else too.

I agree that for the backup scenario the best answer is to use a generator. I do have a small 7.4 kW generator for short outages that I can connect to a panel and run critical loads (once I move the critical loads to that panel). It is gas powered and has not been tested in real life outside of maintenance runs, but still with minimal fuel onsite is probably only good for 1-2 days. A longer support system would be a propane tank and more robust generator but that isn''t exactly cheap either. In just the backup scenario it seemed like having off grid solar panels would extend the amount of time that things could keep running on a given amount of fuel stored. (and maybe clean up some of the power quality?)

Having a generator though doesn''t hedge for higher fuel costs or more expensive equipment in the future. I know this is a long bet as energy is cheap right now but energy is cheap right now so making solar equipment is cheap. If this equation changes then I am not going to be first in line. I am looking to minimize variable costs (fuel) and inflation risk (value of money) more like an annuity (known energy available) than investing in the stock market (price of energy). Recently is has been much better to be in the stock market but that doesn''t mean it will always be true. If I could store sizable amounts of fuel in the short term it isn''t much different than a generator but I am not going to run a generator to power optional loads while solar can be used for that scenario with minimal fuel costs.

What jflorey2 said is where my thinking is at now. Investing some amount of time and money to learn something about offgrid power sure beats shuffle board on a cruise line (maybe that is just me). So maybe thinking about it as a hobby makes more sense. But what size makes sense for a hobby? Is size even the right variable?

-----Everything below here is wayyyy off topic, just be warned. If you choose to read between the lines (or under them) it is at your own risk. ----

---

So physics doesn't always agree with reality?

When I wrote that I was only joking. But when you put it that way, yes. That is true.
Here is a quote from Philip Partner from Electronics, a textbook from 1950, that summarizes better than I can the limits of what we consider to be true.

The theory speaks of ions, atoms, and electrons, and of collisions between them; but these are figments of the mind, props for its understanding. [...] The electron, like the atom, is a concept; it is part of a mental shorthand which we have invented to summarize our knowledge of Nature. So when we say, for example, that an electron collides with an atom, we should bear in mind that we have never seen it happen. The use of the present indicative does not turn hypothesis into fact.

Physics is just a model of reality. If maintained and tested it happens to be the best model of reality that we have but it is still a model. (And please don't take this to reason that since physics is just a model that substituting any model is as good as current physics. I am not that crazy.) It is very likely that we don't know a lot and I am certain that I don't know what we don't know.

and

Batteries, physics, and economics are reality and you cannot escape it.

I agree on Batteries and physics as above. I am not convinced economics is in the same ballpark. There are way too many gaps between predicted outcomes and actual outcomes for anyone to sell me on an economic theory. In any given market or economic theory there are suppositions that are not always true. They work tolerably well in context but context isn't always kind enough to remain stable. Ivory tower economics tends to suffer more from these challenges than say an economist that is held accountable for their accuracy by their peers or respective industry but they are all based on very specific models. Again I have no crystal ball but even if there is one best solution it doesn''t reason that it will work for everyone. It would be kind of boring too.

[bcroe]

Physics is just a model of reality. If maintained and tested it happens to be the best model of reality that we have but it is still a model. (And please don't take this to reason that since physics is just a model that substituting any model is as good as current physics. I am not that crazy.) It is very likely that we don't know a lot and I am certain that I don't know what we don't know.

There certainly is much we don't know (seems to be increasing), but I considered Physics to be the actual
thing. What we have written in a book might be the best model at that time. Sorry if that doesn't agree
with the definition. Bruce Roe

[J.P.M.]

Hey Bill:

One of the things I haven't seen you mention or allude to yet is the value of reducing your need for energy in an emergency or any other time for that matter. Might just be a cheap way to reduce some of the angst about the future that seems to be seeping out of your text. Just sayin'.

What I've seen from you so far looks to me that it's all about meeting an unspecified and unquantified demand using a resource you know little about beyond buzzword terms.

To perhaps remediate some of that shortcomings it also looks to me like you could use some education that's more basic than all the applied or secondary stuff you've mentioned so far.

To that end, I respectfully suggest you start with a copy of "Solar Power Your Home for Dummies". Then, learn a bit about resource assessment (including understanding solar potential at a site), make what sounds like it may be some tough choices between trees and PV, and know that solar is a lousy backup in an emergency, and that service off grid is neither cost effective nor a viable or practical option if grid power is available.

Get a propane fueled generator. My bet is lifecycle costing will favor a propane fueled ICE backup over the added expense of off grid PV for emergency power. Or, as some suggest, get SMA inverters for some daytime off grid power.

I also get the impression from your writing that you've started to believe some of the hype from the press and peddlers you've been decrying. Real knowledge of the technical details will help disabuse you of the fallacies that seem to have perhaps subconsciously internalized, or at least understand if not totally agreeng with what a lot of experientially based and technically proficient opinion around here is saying about off grid backup options.

On the off chance you may also have the common attitude of somehow getting away from (or "even" with) your POCO, know that while it can be done, it takes the form of a pyrrhic victory both in financial resources and effort.

Welcome to the forum of few(er) illusions.

Take what you may want of the above. Scrap the rest.

[BillSunGen]

Bruce,

I am not really sure what we were disagreeing on. The point of that quote is that physics describes reality, that doesn't make it reality. As an example related to the quote, the Bohr model of the atom is still widely used in education. It works in the sense that it uses words that are familiar to us and our experience, electrons orbiting a nucleus like planets around the sun. It works for us but that is not reality. If it were possible to zoom in and watch an atom (whatever that would mean at a scale smaller than visible light) it isn't a solar system. Physics have known that since shortly after Bohr proposed the model. It is still useful. The same way that Newtonian physics still works even though we know now that calculations based on relativity are a more accurate description of reality. Anyway, I just think this stuff is neat. Not trying to disagree with anything in particular

[BillSunGen]

JPM,

I want to cover this one first. Because I feel my writing was not clear.

I also get the impression from your writing that you've started to believe some of the hype from the press and peddlers you've been decrying.

Of course it was not clear because I was trying to be funny, so I make no promises to change. But I think what you mean is that the rainbows and unicorns are not real. That hurts my world view and I hope you will apologize for the damage you have done to my feelings . Ha, had you going there didn't I. To your point, or at least in the near vicinity, I did want to believe a lot of the marketing promises around certain aspects of these systems but I hope it is also clear that I am not one who would sign the dotted line, drop some dollars then complain when it doesn't work like magic. I made this post at the point that none of my original plans worked for this part of the system and that is ok too.

So back to the other points. Thank you for the tips, they are all important points and not something that I have disregarded. I am not really interested in proving what I know but if you want to quiz me I would probably do well. I have never fit well into any particular stereotype so that may be what is confusing on my motivation. It would be a much more interesting conversation over a beer at a local bar. Suffice it to say that unlike what SunKing assumed above I am not a democrat trying to push the environmental lawyer complex (similar to the military industrial complex, just with different winners) at the national level. The illusion that solar will somehow save us from the "evil" oil and provide free clean energy for all is not one I hold. Neither am I an extreme pessimist who believes that the grid will fail and we will all become hunter gathers in the wild all Mad Max style. I do believe in preparing for likely scenarios, and for those am in complete agreement that the standard generator approach is the best. Where I take the next step is in observations that something in our system is broken. This is where the "economics" comes in. Like the trees in my yard. Standard cash flow, if making the decision based on my individual $s, says that it would be best to simply cut them down and burn them or let them rot. Energy is so cheap right now that it is less expensive for a massive company hundreds of miles away to cut down trees more efficiently, process them, and ship them to me than it is to use the trees right here. So just get rid of them. Instead I paid more for someone local (still using that cheap energy, they had some big machines!) and a portable sawmill to process the trees into lumber that I will use. The waste will still be burnt but as firewood, reducing some electric cost. That is nice and something I can do to reduce waste but doesn't change the fact that everything in my life is based on this cheap energy. Everything. For anyone who believes that energy will be cheap forever, I would refer them back to a few years ago or even the 1970s. In both of these cases the price of energy did not respond in a smooth supply and demand balance like someone applying simple classic economics would expect. It is more of a bi-polar crazy loop of speculation and crash accelerated through our very complex set of controls that manages that energy supply. That is more what I am thinking about here. It would be nice to mitigate some of the extremes if it happens again.

So while we are all affected by the thoughts and beliefs around us I am my own kind of crazy and would be glad to discuss any particular fallacies that you see in my thinking but please don't dress me up as a strawman and shoot it down. And if you find the magic battery that makes all of the marketing work please let me know first!

[bcroe]

One approach to energy used here is an adequate grid tie system. Generating your own heat and electricity,
the market price isn't of much concern. Beats carrying firewood as some off griders do, and burns less carbon
than they do. Get an electric car if you don't want to buy gasoline.

The problem is generating the most energy in summer, and needing the most in winter. But the PoCo is
a free, infinite capacity, zero maintenance, 100% efficient battery for me.

Backup, got a generator for that in the previous century. Have only used it 4 times. Bruce Roe