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Do I really need batteries for a solar energy system?  RSS feed

 
Michael Deaves
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I am planning to build a simple off grid house soon, and as part of that I was evaluating my energy needs and determining the cost of my solar system. What I notice is that the batteries are the most expensive part, and they are prone to wear, and need to be replaced every few years.

Then I started thinking about what I actually need. My electricity needs are as follows,

-Water pump to pressurize water system
-Fridge/freezer
-Laptop
-Charge cell phone
-Lights

All of these system, except for the lights, have built in storage capabilities. If I get a big enough pressure tank, I could conceivably go many days without having to run the water pump. A well insulated fridge or freezer likewise. My laptop/phone have their own batteries. The lights are the own component that doesn't have it's own storage, but a few 5W LED bulbs could be run from some D-cells.

Has anyone tried this route? That is providing other forms of energy storage (thermal, pressure, component batteries), in order to reduce the cost of your solar system.
 
Kyle Neath
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Location: High Sierras, CA 6400'
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Technically: No
Practically: Yes, at least some

The key here is that most solar systems take the output from the solar panels and store that energy in the batteries, then the inverter takes the output from the batteries to supply A/C. Batteries can be charged with any number of watts, and so fluctuating power output (from shadows, clouds, etc) isn't a problem. The batteries just charge slower or faster. But appliances (laptops, fridges, pumps) need a consistent power source to function properly. A lot of these motors and are prone to extreme wear if they're given uneven current. With a battery setup, the power output is constant regardless of what may or may not be shading your panels. While batteries do exist to store power for night-time, they also exist to regulate the current and provide a consistent electricity output.

If you're uninterested in storing energy for night-time, it should be fairly inexpensive to get enough batteries to regulate current. Even an old car / golf-cart battery might work (depends a lot on your inverter and charge controller). And while it's possible to go battery-less, you'll need additional components that will probably make it not worth your while. I'd say get some used/in-expensive batteries and see how it goes. You can always get more batteries this way, and once you have one battery setup it's pretty trivial to add additional ones.
 
chad duncan
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It would certainly be better to have a battery or two. Don't be afraid of using old batteries, they are not as great new but they are better than nothing. It's nice to be able to charge your laptop at night.
A lot of people say that you can not mix and match batteries but I have been reading a lot of scientific studies regarding this and it feel that it is simply not true.
Some rules need to be followed though:
1. Batteries wired in parallel must have the same charging characteristics. for example an standard lead/acid car battery may charge up to 14.8 volts while an AGM (also acid based) may only be good to charge up to 14.4 volts.
2. batteries wired in series should have the same amp/hour capacity.

Due to internal resistances one battery may release it's current sooner than the other (ex: a newer battery may partially discharge before the older battery parallel to it does, for early stages of the discharge) and this will cause the more used battery to 'wear out' sooner but not sooner than a single battery would have anyways.

Also, when the sun first comes up and the panels start to make voltage but before they produce amperage, they can create a momentary high voltage that could feasibly damage sensitive equipment. A battery bank would soften this.
 
Galen Young
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Without any batteries you will be totally dark every night.

Even grid-tied systems will need batteries for days when the grid goes down.

 
Michael Deaves
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Thanks for the tips, it makes a lot of sense what you're saying.

It sounds like a good route to take would be to buy a few used batteries, for quite cheap, that can't hold a charge for very long, but at least buffer the incoming energy from the panels.

Another route that I could take is to just purchase a few extra panels, instead of the batteries, and then somehow dump the extra power when the items I'm running don't need it. For example lets say the fridge motor is 5A @ 24 V, then when the panels have enough sun to produce 5A, the fridge motor clicks on, but if there is shade or something it stays off. If the panels want to produce 6A, then the 1A difference is wasted somehow. This seems to me that it should be possible without the expense of a battery and expensive charge controllers.
 
Michael Deaves
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Of course I would lose some efficiency in this kind of system, but looking at it from a holistic view point it might be better energetically, because the embedded energy in the batteries is not needed.
 
chad duncan
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Something else to consider if you want to avoid batteries and solar chargers is that a nominal 24v panel can run closer to 35v (Vmp, volts at max power production) in full sun and as high as 42v open circuit voltage (Voc, max voltage possible).
A couple of cheap deep cycle batteries (2 6V batteries in series) and a bargain bin charger can be had for under or around a hundred bucks and would be effective at protecting electronics and would allow you lights and laptop charging at night.
Good batteries would allow running the fridge overnight.
A good charger is great for maximizing storage of the energy harvested and for maintaining healthy batteries.
 
David Baillie
Posts: 38
Location: North central Ontario
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Your idea can work fairly easily.  Many charge controllers can also operate as a load controller. If you equip a larger solar array with a small battery when it's voltage shoots up your load controller can turn on devices to use a much larger portion of your solar.  The small battery can run light loads at night.  You would be using the small battery as a buffer.  It's an ok solution but it will rob you of a lot of flexibility.  You are right batteries are expensive but a correctly sized deep cycle battery bank should last 7 to 12 years not a few and is recyclable at end of life.
Best regards, David Baillie
 
Galen Young
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I live in an area of the East Coast where the power grid is not reliable and accesses less than 2/3 of the state.

solar power is great for what it is. Solar power is not the end all be all, it needs help. Batteries have been the device most commonly mated to solar panels to make them more useable.

As I went off-grid I learned that most off-grid homes tend to kill their first battery bank at around 10 years. When properly maintained batteries should last 20 years. There is a learning curve to living with a battery bank.

I spent 20 years on submarines, I thought I knew everything about batteries. But there was more to learn.

Our battery bank is 48vdc/600ah. To really make our home comfortable it should really be more like 1500ah. But we limited how much we spent on the batteries.

Don't be frightened by the idea of having batteries. They are needed after all. I spent far more on solar panels then I did on batteries.

 
Michael Deaves
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Galen, can you elaborate a little bit more about what you mean when you say 'to make our home comfortable'? What inconveniences do you typically have from running a smaller battery bank?
 
Peter Kalokerinos
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Location: Hunter Valley, NSW, Australia
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If you genuinely think you can go without modern comforts, then take a look at nickel iron batteries. Last pretty much forever, but are twice the price of lead acid.

What sort of fridge/freezer are you planning? anything larger than say 2 x 60L camping fridges are going to need a fairly substantial bank to keep on 24/7. We kept ours going well with 2 x 200 amp hour 12v batteries.

I'm not sure about the draw on small pumps, but if it is small it'll take forever to "charge" a large pressure tank - if its large it'll do it quick, but the draw will be larger. I suggest you do the math on that.

What about a clothes washer? you need this. Don't kid yourself into thinking you can go without. We did for a good while, its a total PITA.

Dryer? Dishwasher? TV? I suspect not

Power tools?

Radio?

Moderm/communication devices?

hot water?

Cooling fan or some type?




 
Galen Young
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Michael Deaves wrote:Galen, can you elaborate a little bit more about what you mean when you say 'to make our home comfortable'? What inconveniences do you typically have from running a smaller battery bank?


On day 3 without sunny skies things get rough.

We heat our home with wood. Our woodstove heats water, which circulates to a thermal-bank, which circulates through our radiant flooring. It is extremely efficient, but it requires circulation pumps [a small load].

We produce most of our food. Which task is made easier by having chest freezers. Our freezers all run on timers. They only operate during sunlight. The rest of the time they need to stay shut.

When the sun is out we have plenty of power. We can run every power tool and appliance. But at night, or during an overcast day, we must conserve power. If we go 3 days without sunny skies, our batteries can get pretty low.
 
Galen Young
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Peter Kalokerinos wrote:If you genuinely think you can go without modern comforts, ...


I looked at each of the solar power systems in homes here in our town, before I committed to which design of system we would go with. One home uses a 12vdc system from the 1980s, it is really cheap and simple. But by then we already had our well running with a pump, a 240vac 15 amp [surge] pump. That dictated what kind of inverter we needed. So everything else was designed around our inverter.

We have a clothes washer, a Dryer, and a Dishwasher. We got the dishwasher after we shifted to solar power.

My wife still uses an electric coffee maker [I only drink green tea, though I hate it in a microwave].

No TV though. We had one back when TV was high-power analog broadcast. But now with low-power digital our only option for TV signal would be satellite. We are fine watching stuff online.

I do have a selection of power tools.

We had a nice home stereo, but the frequent power surges and outages killed it about a year before we went to solar power. Grid power here on the East Coast is really crappy. Outages every month, all year round. Often grid outages start with power spikes that fry CFL light bulbs and electronics.

We have a couple nice ceiling fans.

Keep in mind that off-grid solar systems with batteries are commonly cheaper than net-metering systems, regardless of how much the banks market net-metering and how their marketing makes claims to the opposite. Banks do love to finance that junk. Here in Maine they are constantly pushing legislation to subsidize higher priced net-metering systems.
 
Peter Kalokerinos
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Location: Hunter Valley, NSW, Australia
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Galen, I'm certainly not suggesting it can't be done, but in the context of the OP's question, it seems to me the cost of the batteries is a real issue...so it comes down to what he can afford and what he really can/can't live without.

We threw huge $$ at ours so we can do whatever we like....

 
wayne fajkus
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You don't have hot water listed, but it can be done without batteries. A small pump connected to a small panel will circulate water through a solar collector (heater) only when the sun is out, which is when the water will heat up.
 
Galen Young
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In this area, 'solar' usually means one of two types of systems. Either it is off-grid solar, stand-alone, or else it is net-metering which is far more expensive, you can 'bank' power onto the grid and use it later when it is dark.

Batteries allow your system to be much cheaper and allow you to function without the power grid.
 
David Livingston
steward
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Galen
My understanding of hour last comment is unclear . Leaving aside the competence or lack of ( usually ) of the power company and the rapaciousness of the banks ( legendary ) . Why is going off grid cheaper ?
Assuming your power needs are the same and have the same money to spend either you spend X on a system plus batteries or you spend X on a much bigger set of panels and feed the grid so at some point depending on your usage either the former or the latter is most cost effective . This tipping point will depend on the price you get in return from the company and your usage and I would assume a simple calculation to make .
David
 
chad duncan
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Off grid is cheaper at the initial purchase because the equipment that ties you to the grid is very expensive.  Another tidbit to consider with grid tied systems is that they shut down during a power outage (generally). this is to protect linesman from getting electrocuted by lines that are powered by the load side. For example, when a line breaks and hits the ground, one side is live and the other is dead. If your panels add power into the system,  the line that would typically be dead will now be live also,  or a line that was dead a minute ago could suddenly come alive as conditions at your panel change.

For what the OP is considering my advice would be to purchase a lower end solar charger and a used deep cycle battery or two. The batteries won't hold as much power as new ones but they will buffer the sporadic nature of the panels which are affected by everything from clouds to tree branches to bird poop.
 
Galen Young
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When a car dealership has a car on their lot. They know how much they paid for that car and they know how much mark-up they need to stay in business. Let assume for a specific car that price is $10,000. If you walk in and offer them $10,000 cash you can drive the car away within the hour. But if it must be financed you bring in a host of other businesses who each need to make a cut. the financed price might be $15,000, divided out over 60 payments of $249/month.

The finance company gets their cut of the action, and they maintain a team of lobbyists in the legislature. I have attended local Solar Power town meeting 'event's with state legislators, lobbyists, and installers as panel speakers.

Solar power systems are a group of components. Each component is pre-wired and UL tested. You can buy each component online and they go on-sale, then you can assemble them yourself.

When a solar installer comes to your house, he needs $45'hour for each of his workers just like how a car repair shop needs $60'hour for shop time, to make his bottom line work.

Suppose that a 4500watt solar system that is net-metering will cost you $25k financed over 20-years. An off-grid 4500 watt solar system with batteries may cost you $20k. [One of my neighbors has a net-metering system, their wattage is close to my wattage, these are real close to the numbers to compare our systems]

In my state there are only a few licensed solar installers. Licensed electricians are not allowed to touch any solar system. All installers are equipment dealers, they refuse to touch any component that they did not sell you. If you buy on-sale panels somewhere, the installers will refuse to install them, because as retailers they want the mark-up.

I got quotes from 2 installers. The standard battery our local installers market is the Rolls-Surette at $500/each. The batteries I am using are Exides from a local feed store for $99/each.
 
frank li
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Location: Michigan
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Yes i have tried it and set it up for others. Invest in a good battery charger for the personal device batteries you need to charge, possibly an automotive or other dc power supply that is variable.

https://powerwerx.com/dc-power-products

http://www.nitecorestore.com/?gclid=COHQwc3QpNQCFdlWDQodo3gOsQ

Do check available specs on all equipment. Higher voltages and currents (low voltage?) than component design values may be present.

I have no issues running our charger for aa and aaa batteries while the sun shines, without a pv charge control.
Proper dc rated components may look pricey, but are generally of high quality and are heavy duty use capable, marine grade, etc., even if not listed devices but used for small projects. Household electric though, always commands caution to be aware of what you are doing.

I dont let a charger go like that in or on my home, generally...un-attended, no. Camping and hunting, maybe.

Many dc devices and appliances, lighting parts, personal electronics, etc., are available in like a 9-30+ voltage acceptance range, if you are tenacious and find a few examples and sources.

The portable power pack type thingys with the usb, common dc out, sometimes inverters, etc, all in one box the size of a box of crackerjacks, lunchbox or on rolling carryon type luggage arrangements may work great.

The one i would like to try is the yard electric power tool battery system pv hybrid, which happens when you plug in a charger for anything from a cellphone to a golf car that has a charge transfer from your central battery system, direct or through an inverter system... but i mean micro system based on the lawnmower and chainsaw batteries, or even the jumbo backpack and woodworking batteries they have now.

All in all, if you are getting or looking for the kind of service-duty electrically, that you indicated you either, already are capable of not having a central electric storage battery, or have the possibility of not having the capability of supporting loads and integrating, and the buffering (regulation, protection and control)

A central battery system solves this handily and may incorporate the other batteries in the system, definitely the ones you listed... from one safe, regulated source as a main, you can stack as many auxilliary systems on as you have money and hair to pull out for!

For a system like yours, unless you are a hardcore breed or pragmatically addressing this, or already found the way to do just what you describe, as many have done, a $30-$200 battery, low dollar charge control, possibly diversion ( but only for requirement, utility or flair), some distribution at point(s) of use, and judicious load control, go a long way in getting good expedition, cabin or even home power out of a micro system, or a dc direct to device, approach.

Im blathering. If you are building a new home, and can swing it, i would have at least a small, central electric storage system for the way you describe operating, unless you enjoy 1860's living in all ways....

At some point, having more and more batteries and chargers can get to be less efficient, cost effective, and convienient.

I do know people who only need lights in the daytime and others who use outdoor solar shed-kit lights and lawn lights inside, simple comms, charge a laptop at home a couple times a week and use gravity water and wood heat, so it can be difficult to determine and then i go on about having more batteries to have less batteries!

I love permies, good morning.






 
frank li
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Galen Young wrote:I live in an area of the East Coast where the power grid is not reliable and accesses less than 2/3 of the state.

Solar power is great for what it is.

Batteries have been the device most commonly mated to solar panels to make them more useable.

I spent 20 years on submarines, I thought I knew everything about batteries. But there was more to learn.


Don't be frightened by the idea of having batteries. They are needed after all. I spent far more on solar panels then I did on batteries.



A variation of one of my lines with clients, ' i learned to operate my pv systems like a ww2 u-boat crew, so you dont have to'

Or

"I promise, you wont have to operate this thing like a ww2 u-boat crew"

I get sea legs thinking about mine.

!
 
Galen Young
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frank li wrote: ... A variation of one of my lines with clients, ' i learned to operate my pv systems like a ww2 u-boat crew, so you dont have to'

Or

"I promise, you wont have to operate this thing like a ww2 u-boat crew"

I get sea legs thinking about mine.

!


On subs [both WW2 and nuc boats] they really do not care about life-span of the batteries. They buy obscenely expensive batteries, they drain them to 10% SOC and they do weekly equalize charges.

Now that I have a battery-bank I baby it.
 
D Cali
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Galen

Could you explain why Net-metering is more expensive?  I have purchased land and I do have power on it, my own poll and transformer.  I also travel a lot and am looking into solar for my RV.  I have been researching if it would be possible/feasible to use the portable Solar system to reduce my usage when I am at my cabin and one way to do that is with net-metering.

Thanks in advance for your input


Galen Young wrote:In this area, 'solar' usually means one of two types of systems. Either it is off-grid solar, stand-alone, or else it is net-metering which is far more expensive, you can 'bank' power onto the grid and use it later when it is dark.

Batteries allow your system to be much cheaper and allow you to function without the power grid.
 
Galen Young
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D Cali wrote:Galen

Could you explain why Net-metering is more expensive?


I got multiple quotes when we were ready to do the solar power thing.

Net-metering with the 20-year contracts and financing worked out to be more expensive.

Financing includes interest payments to a bank, it may be a small monthly payment, but over 20 years it is a lot more than an off-grid system with batteries.

I bought my components online. Our local installers are all equipment dealers. They refuse to touch any system with components that they did not sell you. Our installers only handle top-line gear and their mark-up is high. You can buy everything you need on-line for a lot less cash.

In our small town, so far, we have four homes with solar power. We all talk and compare systems. Of these systems only one has net-metering, same wattage as mine and they paid more than I paid.

If you buy your gear online, you can save a bundle. Install it yourself, saves a lot too. Do not include bankers, to save yourself even more.
 
Daniel Schmidt
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Location: Jacksonville, FL
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This guy on YouTube has some videos on using super capacitors to power things. He has used them on his car and also connected to a solar panel. The price on such large capacitors seems to have come down over the years. They still aren't exactly cheap, but a small bank of them can be made for a relatively affordable price. They are light, they tend to have a much lower resistance than batteries - which means they can give or take a charge almost instantly, and they can be filled and depleted many more times than a battery. You don't have to keep a state of charge, so no risk of ruining them in that sense. They can still be damaged and die in spectacular fashion with too much voltage, similar to some types of batteries.

I think these can be used as part of a system to reduce the need for batteries. When he replaced his car battery with capacitors, he noticed it didn't hold a charge very well when left for a few days. He ended up adding a small battery along side the capacitors, which still yielded a lighter energy storage system with potential for a much smaller footprint of toxic gick. Using fewer new batteries, or diverting some old ones from being recycled for a few more years might be a viable method.

Then there is the saying of 'make hay while the sun is shining'. If you can slightly oversize your solar array and use power as it is being made then you can minimize the need for storage. I think this is one of those things that can only truly be learned in the trenches. Finding what is and isn't acceptable to you and pushing yourself beyond your comfort zone will help you realize what works for you.
 
Permaculture isn't that hard to understand. Sometimes a little bump helps: richsoil.com/cards
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