alternative battery using a pond or well?

hello! It's been a long time dream of mine and I just moved off grid to my own property this year! first post.. love this forum so far

i've got a bunch of solar panels that came with the property and an aging solar battery bank - the batteries don't seem to hold much of a charge - i know there are a few things to bulk charge them and try and bring them to back to life. while that's in motion i'm looking into alternatives for energy storage

i have a very good size pond.. about 170k gallons, and a ridge way above it, i'm curious about pumping water to a tank up on the ridge and using micro-hydro to capture the energy -- i saw a great post on this forum about it so moving on to another way to use it..

could I use thermoelectric to use my pond as a giant battery by capturing the temperature difference between the pond and the outside air? i read about converting it to a solar pond but that would involve temperatures of over 130 degrees Fahrenheit which would make it unusable for anything else (like kayaking and swimming which is how we use it during the summer).. ?

another option is that i have a second and unused well on my land. could i somehow use the temperature difference between water at the bottom of the well and the outside air to generate electricity?

fly wheels? i saw a lot of information about them but not how to build or buy one in expensively.. also they seem dangerous -- all that stored energy in a fast spinning contraption that could "fly" off in any direction at any time.. ?

-- currently i have 2,000 watts in solar panels and have another 4,000 sitting on my driveway ready to be installed, i will have more then enough solar power and i need somewhere to store it..

i've been looking into hydrogen fuel cells as well but the only commercial solutions i could find seem like they would cost me up to $40,000 which is way out of my budget!!

i would LOVE to find a really neat alternative to storing energy - as it is.. at the moment i can not get through the night without having to run my generator to survive and keep the house and family warm

thank you in advance,
mitch
a new permie!

Mitch Ranu : When the world hands you lemons make lemonade- If you have solar panels to use by all means use them- If this has to be a D.I.Y. Project then basically

you are going to have to teach yourself how to be an electrician, check out local adult educational schools in your area and double and triple check your work. Getting

A licensed Electrician to check your work will probably save you big bucks on the long Haul ! There is a lot of good Threads posted in the Solar Forums !


You did not say if the pond has a currently flowing Stream as ether the inlet or as discharge for your pond. You can google Hydraulic Rams or Water rams, these use the

energy of falling water to pump a smaller fraction of that water uphill. Careful placement of swales on contour can greatly improve the amount of water retained on your land,

generating new streams or making an existing stream ''run fuller''and for more months of the year, Additional ponds located higher up your slope from your existing pond is

very possible. A google search for swales , and a look at what Geof Lawton is doing geoflawton.com will quickly give you inside and provoke you to do more and more study



Thermoelectric can work, though for years it has been misused; Here is a link to a hybrid system that not only can use your cold well water to help create the temperature

difference that drives the Thermoelectric 'cycle' but can power the pump(s) to provide that water for that AND further uses //// See link below :


https://permies.com/t/49928/solar/game-changer-Tamera-Sunpulse-stirling


Flywheels are still experimental Technology with 99% of the research going to Large commercial projects - Exactly the same thing can be said for Fuel Cells and Combined Heat and

power C.H.P. units, The CHP units Are quite heavily subsidized in a few countries in Europe ! But keep your eyes open this could change at any time !

For the good of the Crafts ! Big AL

Mitch,

You mention needing to run the generator to keep warm. Where are you located, and what size and type of structure are you trying to heat? What kind of heating system or systems does the house have? How is the insulation? Insulation is often the most cost-effective measure to take.

Mitch Ranu : My post was running a little long and even good information does little good if it is overwhelming !


Location, location, Location, Like Steven Goode said we generally need to know location and climate to assist you with good answers !

Below are a few links to make your searches and your future posts more powerful ! //// See link below :

https://permies.com/t/43625/introductions/Universal
https://permies.com/t/34193/tnk/permies-works-links-threads

For the Good of the crafts !

Hey guys! Thank you for taking the time to help me ponder my options.

Steven, I definitely feel like I've been getting a crash course in electrical engineering!! I sold the Outback VFX3648 inverter that came with my property and replaced it with two newer model Outback VFXR3648A inverters for a total of 7,200 watts. So far I'm still deciding how to wire them up finally. The idea with the second one was yes.. more power, but also the ability to charge my batteries twice as fast (and run my generator less!!) and then also to power up my well pump which requires 240v.

What do you mean by the swale being better then falling water? I think my drop from ridge top to pond would be about 100 feet.. pretty solid no? The pond is already full with a pond liner.. I actually had to top it off a couple of times during the summer from the well. Unfortunately there is no stream running to it unless i'm in a VERY heavy rainfall which only happens occasionally during the winter.

I don't have a lot of land to store another pond/swale up hill from my pond but I could try.. there are a few options but they take away from some of the usable open areas of which I only have a few. How big would it need to be to store about 20kwh ?

I've been looking at the stirling generators and I'm really curious about using them. I do like the idea that a fire could power it using wood (of which I have plenty) and then maybe that fire could be set up to warm up my house too.

Allen, I'm located in the Santa Cruz mountains

Steven, The generator charges the batteries back up and the batteries run the re circulation pump for my radiant floor heater for my Yurt. The water for the floor is heated with propane from a large tank outside. It sounds fancy but it has a hard time keeping the place warm on a cold night and also takes hours to get warmed up. I recently added insulation panels to the Yurt walls and they seem to be helping at a 3 on a scale of 1-10 with 10 being the best.


Are there alternatives to storage? What about some sort of kinetic energy capture system where I lift large stones using sun/electric power during the day and let them "fall" slowly? I just feel like with all the acreage I have (over 20) that I have the space to design something fun/wacky solution to this.

One of my back up options is those Aquion batteries.. it seems like they could work for me but they are currently back ordered until February.. they also seem costly.. I could use them and figure out the funds but if I have just have to spend a few thousand to build a swale that holds 20kwh vs $15k for 20kwh using the Aquion batteries.

Also the swale idea could help me with cleaning up the pond/adding a filtration system... two birds.. one stone?

Steven, I watched the video about Sunpulse but I'm unclear on how I would use this with my extra well? If I could tap into it for electricity that would be really great.. It seems like it would be the lowest fuss/maintenance solution. Also it's location is very close to my batteries/inverter/electrical panels. So that would be a BIG win!

Mitch Ranu : Lets try thinking about swales another way, there is an old joke about Hill-billies having their Right leg shorter than their left and they walk

around their mountains Clockwise, But always on the level nether going uphill or down If you draw a line connecting those points all al the same level

that line followed the contures of the land, nether climbing or falling These are the Contour Lines found on a 'Topographical Map !

Shallow ditches cut along the contour lines are Swale lines this slows down and holds the water running downhill and allows the water to soak in !

In Your part of the country you may have to add Check Dams made from stacked rooks and back filled with rubble ! These specialized manmade terrain

Features Allows the water to soak into your land. Your 1st benefit should be never having to pump water into your pond as sprains and seeps work to

create surface water that can be channeled into your pond .

Due to the inefficiencies of pumping water up hill your total 24/ 7 product will probably be capable of only several minutes of Micro-Hydro, this is why your

efforts to capture and hold water as far upslope as possible is your best shot at power generation, Again all a swale does is capture and holds Your water

onto Your Land, you would still need a holding pond upslope as high as possible ! Also important, very important is that portion of land that is not your land

but by being upslope from your land drains onto your land, this could be 1,000s of acre feet .


I am totally unfamiliar with the Aquion Sodium Batteries, and had to look them up ! //// Link below :


https://en.wikipedia.org/wiki/Aquion_Energy

I am a little concerned that this source was only quoting last years sales figures, Regardless This is a superior tech to Lead acid batteries which I would not

consider at all

I will review the sterling engine video so that you can bounce questions off of me - - - - For the Crafts ! Big AL

allen, thanks again

i did some reading on swells, i'm unsure how the water would be accessible to send through a micro-hydro.. swells seem to hold the water.. but in the ground?

agreed -- I want to avoid lead acid batteries as much as possible

looking forward to your insight on the stirling generator/well idea.. would be great if this was the solution!

thanks
-Mitch

Hey Mitch, welcome to permies, and congrats on your property!

Beyond the soakage benefits, swales will help bring water to a pond by preventing it from crossing the line of the swale; the water which might have kept moving downslope away from the pond will travel along the swale instead, and you can lay them out to lead to a pond. Even if there is no visible water flowing, they can impact the amount of water a pond receives.

---

Awesome, 6000W is a TON of solar! It really seems like you should be able to meet your energy needs from that without the need to invest in more exotic options like the stirling cycle generator, etc... wacky and fun as they might be! It seems a little crazy to, for example, add a stirling cycle generator, powered by a fire of some sort; if you want to tend a fire, just get a woodstove to heat your yurt, and use the solar for everything else! This is a perfectly valid option, IMO, and you could leave the propane system in place as a backup.

If you want to get fancy, you could tie in a boiler on the woodstove to the radiant floor system.


If you're not depending on the batteries to make the heat, but simply to run a pump... just how powerful is this pump? Could you replace it with more efficient, lower flow option? Looking around for 12V circulation pumps, I'm seeing amperage ratings of anywhere from 0.5A to 5A.

Even a 5A pump running for 16 hours straight until sunlight returns would only be 80AH. AKA, less a than a single KWH per night. At 50% DoD you can get this out of a single sizable deep cycle battery or a pair of 6V golf cart batteries... though I'm really not a big fan of lead-acid in general, this sure seems quick/easy/cheap compared to some of the other options discussed!

You'd want to scale up to allow for cloudy days, but you have such a ridiculous bank of panels that even with only 2000W of them online you need hardly an hour of sun to replace an entire night of 5A load; add the other panels and your limitation may well be the battery charge rate rather than the available solar power.


If you want to stay away from lead acid but still store all this lovely electrical goodness without the major efficiency losses of converting it to heat or physical energy and then back to electrical power... you have numerous options. NiFe batteries(Iron Edison), LiFePO4 batteries(Lithium Iron Phosphate, many makes, mind you get a battery management system to take care of em), salt water batteries(Aquion as already mentioned)... not a fan of Lithium Ion personally, but it is an option too.


IMO, the best argument for converting electrical power to some other form, is if the other form is what you ultimately want. That way you can skip the need for batteries for that portion of the energy storage. I think setting up a bank of super-insulated water heaters to stockpile very hot water for later use as a heatsource has good potential. 0.2931Wh to raise temp of 1lb of water 1 degree F; @ 8.34lbs per gallon, so 2.3448Wh to raise 1 gallon 1df. So, by my math, raising the temp of the water in an 80gal HWT from 62F(guesstimated groundwater temp in your area) to 140f, you'd use up ~14.631KWh (2.3448W*78df*80gal).

If you're using HWTs like this as a thermal battery for heating in the night, you'd probably find they become an ineffective heat source somewhere well above 62F. If this point was 100f, !7.5KWh of heat could be recovered from a tank that size at that temp. But if you are able to heat the water to say 180F instead of 140F, you'd be able to pull 15KW before getting down to 100F.

Even once your remaining panels are online, in an 8 hour winter day the theoretical maximum energy you could pull in from your 6KW of panels is 48KWh, so after the various losses along the way, the energy which could be stored in perhaps 300 gallons of 180F water would easily suffice to store a whole day of sun... There is probably some sweet spot for capacity, where you would have enough volume to store substantial heat, without the tank becoming unreasonably large and thermal leakage unreasonably problematic.


The other thing you will want is water pressure; you could avoid this causing a load on your batteries by pumping well water up to a raised reservoir when the sun is shining, and using gravity feed to power sinks, showers, hoses, etc. No need IMO to complicate the system and lower the efficiency by adding power generation to this portion; I'm convinced that batteries are a better solution for the portion of your power storage that you ultimately wish to use as electrical power.

Dillon, On the surface that sounds really great.. Water is cheap, safer than other options, and tanks should not be expensive.. I'm into it..

How would I convert the heated water back into electricity?

I will have to measure the pump.. It does seem to use a lot of power.. That's a good tip. Overall through the night I only seem to use 400 watts on average per hour.. I think there is something wrong with my meter though as sometimes randomly for one hour a day it will jump up to 14kwh that I used for that hour.. which is ridiculous! There's a bug somewhere.. So saying that overall I think I use between 15kwh to 30kwh. So figure somewhere between 8-12 kwh per night.

So a 300gallon tank could give 15kwh, if I get 5 of them would give me 281.25kwh?

80 * 3.75 = 300 gallons
15kwh * 3.75 = 56.25kwh
56.25 * 5 = 281.25 kwh ??

How long can hot water be stored? I mean that's almost 10 days of power I could have stored.... I feel like I might be doing the math wrong here!

Would I put the "end" of a stirling generator into a hot water tank and then that would create the electricity?

This would also easily give me hot water for my house (??) without having to use my propane -- which I would LOVE as not just because of the cost but because I understand it supports fracking..

Could I heat the water back up using a fire under one of the tanks in the event the water cools down? Well maybe not so simply but essentially?

I would also love to stop buying gasoline for my generator.. Carrying it up and down my mountain almost 3-4 times a week is painful and expensive.

Re: water pressure -- My water tank is already up hill but requires a pump still.. The tank is about 200 feet from my yurt and the water falls down hill a little via gravity and then back up a bit to the pump but altitude of the final spot is lower then the starting spot.. albeit about 10 feet??? So maybe a 30 foot drop then 20 back up. How high up would my water tank have to be to provide adequate water pressure?

You get about 0.43 psi for every foot of elevation. Then you lose some of that to the pipes, the faucet/showerhead, and any other restrictions.

Municipal/city water pressure is generally at around 40-70 psi. I would expect to be able to get away with around 20psi, in terms of actual pressure reaching the house after losses en route, but whether this works for you will be dependent on individual fixtures/appliances, personal preference, and applications.


10 feet total elevation change would give only ~4.3psi minus the losses along the way, which will depend on your pipe and any fittings, as well as the flow rate; an undersized pipe is no big deal at a low flow rate, but a big restriction at 25GPM...

Dillon, I've been reading more about hot water storage you suggested. I'm curious to hear more of your thoughts, especially on how I would convert from heat into electricity.. Are there tried and true systems that folks have used or is everything hacked together? I have plenty of room to store hot water.. This would be so much better.. and possibly cost much less then batteries.. Maybe I can put the tanks in the ground to insulate them?

mitch ranu wrote: how I would convert from heat into electricity.

You wouldn't. The hot water created by solar during the day would be used to keep you warm at night. Apart from heating, what else do you use power for during non solar hours?

Steve, I use power for a lot of things, I realize I live off grid and *should* cut back on some things but I feel like there must be a renewable solution somewhere that can help me feel like I'm still on the grid by storing the electricity/energy I want so I can use it during the night.

For power I mainly use my computers for work, my partner uses tv, the recirculating pump and lights.. While that's a light load in the summer I will want to run the AC at night. Which is huge.. As well as I'd like to add landscape lighting around my property (not the solar kind since there's shade in a lot of places) and possibly provide electricity for future dwellings for friends/family or possible tenants. So something scalable would be great and if 15kwh can be stored in 300 gallons that could scale by me using electric elements and solar water heaters during the day to keep even more water hot. Currently I can already heat my water with propane.. My bigger problem is the 400 watt per hour nightly draw I'm using and that my batteries can barely get me through the night at that rate.

Mitch, I don't think you're tracking what I'm saying... I even put the key bit in italics!

Dillon Nichols wrote:
I'm convinced that batteries are a better solution for the portion of your power storage that you ultimately wish to use as electrical power.'

I stand by this. The hot water and gravity flow suggestions are, as Steve says, not intended for electrical generation, but rather to utilize solar power to provide other needs in a way that reduces battery requirements.


Your updated electrical goals are a very far cry from the initially described problem.

If you want to live off grid and pretend you are on grid, I suggest you suck it up and throw money at a very large battery system. It may not make sense to use the solar panels for heat in this scenario, since you will need a lot of the available power for all these electrical wants.

400W is 6-10x the power I saw for small DC recirculating pumps. Looking at a plumbing supply site, pumps meant to fill this role *in a house* are rated from 1/40th to 1/6th HP, so even at the larger end a long ways from 400W. This is still the most immediate problem to resolve IMO.



As for the alternatives, I simply do not think that you will ultimately see better results, in terms of cost efficiency, from a system that attempts to take electrical power, convert it to to another form for storage, and then convert it back to electrical power. The stirling engine is very cool, but 1 engine with added generator, pressure box, and fire box will run you nearly 3 grand shipped for a theoretical max of 1000W. To the best of my knowledge stirling cycle engines have not surpassed 50% efficiency. Add that loss to any other efficiency losses along the way, and you will see that this proposed double-conversion is a very inefficient process.

Hydroelectric means a lot of water. If you have 50ft of head, you need 6,363 gallons of water to get 1 KWh... without accounting for efficiency losses during generation. So your existing pond wouldn't hold enough for 30KWh; plus, you'd need another pond to hold the water at the bottom, so you could then pump it back up. You'll have to do the math here... A lot would depend on the site, if you can easily put two ponds in close proximity with a 100ft drop between them, near your house and your solar location, that would be a big help....

Ultimately, my guess is once you add up the various costs(not just installation, but maintenance and increased risk of Murphy as component count and complexity increases) and drags on efficiency of any of the multiple conversion options discussed, you will find solar/battery to remain cheaper.

If your site has lots of wind, consider that as an option?

Good luck!

Two main things spring to mind in your situation...

1) you're going to struggle to get away from Lead Acid batteries.
2) hydro isn't going to work well for you due to the huge quantities of water that need to move in order to generate a small amount of electricity.

First step I would take would be to reduce consumption where possible. This doeesn;t mean live like a caveman or compromise on quality of life, but simple things like making sure you are using the appropriate lighting (LED for sure). You mention computers - plural - for work, are you running several non battery powered computers or are you talking a couple of laptops? Obviously get every device a fresh set of extended batteries - these are dirt cheap on ebay for most laptops and phones.
Your hot water is best coming from thermal solar rather than electric water heater powered by PV.
Get your TV and whatever else you can on 12V, no point converting your battery power to AC and stepping it up just to have your TVs power supply turn it back to DC and step it down to 12V & 5V anyway, tho that will kick out a bit of extra heat in the evening.
Turn the thermostat on your fridge and freezer to a colder setting during solar hours and back to normal range at night.
If you're operating any power tools from your battery bank, consider getting a compressor with a large tank that can be pressurised in solar hours and run air tools from that stored pressure. compressed air is fairly efficient storage, and small compressors are very affordable and functional, as are the tools that run off air.

When you say 400W/hr nightly do you mean per night, or for the whole time its too dark for solar, are you talking maybe upto 16 hrs a day? Even so a battery bank of 6 or 8 cheap golf cart batteries will handle that kind of storage, well under $500.

I've made some assumptions here, if I'm way out try to give a more detailed breakdown of your 400W/hr.