can i use a solar panel without using battery

[TinFury]

This was one of my main questions I wanted to ask before I start buying equipment. And it will be off grid.

With the EXTREMELY high price of batteries now, which from my research, now way surpasses the cost of panels factoring in life of product, it doesn't seem logical to have a large battery bank if the majority of electrical use will be during sunlight. I will still have batteries, but I was thinking something like 2 6v 390Ah batteries for minor use after sundown.

Figuring you sleep 6-8 hours at night and here in Arizona you've got say, at least 9-12 hours of sunlight a day. And I don't understand why people wouldn't put some panels on a "fairly simple" pole mount which can be moved by motor or hand. Wouldn't you then get pretty much the full amount of "sun power" sun up to sun down?

That being said, there must be a way to pretty much bypass the batteries during the day, instead of spending thousands of dollars on batteries. Seems like an awful waste to have to use the batteries as a go between, unless it doesn't affect their life, which leads me to another question. Does it? When you have say 1000 watts of sun power and you use less than that at any given time while the panels are producing that, does the power just kinda pass through the battery without degrading life?

I'm no expert. But I think I understand what your saying. Yes..... it will work. It won't work reliably but yes I've seen people run dc appliance directly off of solar panels.

[Larc]

The thickness of the soup we call "atmosphere" really does block a lot of power from the sun in the dawn-10am, and 3pm - sunset. The 4 hours around noon[+2,-2], are the productive ones, so an "ultra tracker" won't help much outside those hours.

You don't "bypass" batteries in the daytime, you have to recharge them, and then, use "opportunity" loads in the afternoon, after the batteries have begun the absorb part of the cycle, and you have some spare PV to run the washer and maybe air conditioner.

If you feel you can get by with only small loads at night, great. I won't tell you to spend $ needlessly, but if you discharge batteries too deeply, you shorten their lifetimes.

Sorry, newbie, just getting my 1 post so can view this pdf. great forum!

[jlvs]

Grid tied solar electric during grid outage.

So I really appreciated this explanation from TnAndy but I wonder about another approach and its interaction with the solar powered system. I live in Thailand where we have lots of solar input and I can get a grid tied solar setup rated at about 4.8 kw for a pretty reasonable price out of China. The power grid here is actually pretty reliable, but we do have the occasional black out. I really do not want to go to a battery system so how about this? If the grid power goes down can I place a backup generator in the system with a grid disconnect switch and fire up the generator to produce temp power. The rest of the question is: 1. does the back up generator pose any risk to the inverter or solar array? and 2. If it were a small. lets say 500 watt generator, and the power fed back through the load center box and then to inverter would the solar panel power be additive to the generator power? So 0.5 kw from the generator and at noon about 3.5 kw from the panels, would this make available about 4 kw to the home and would the inverter start working sensing the feed from the generator. I understand the importance of having a grid disconnect switch for safety. Does this system make any sense?

Why would you burn 7 light bulbs in the day time ?

What you haven't picked up on is the batteries, or the grid, level out the power supply.

Panels don't produce a nice, even steady flow of electricity like a generator does ( heck, even they bog down when you load them up )....a fixed panel produces a little at sunrise, then the most around noon, then tapers off again in the afternoon as the sun angle falls away from perpendicular to the face of the panel. Also, weather conditions GREATLY affect the output. Cloud moves over, output falls WAY off.

In the case of incandescent light bulbs, say a cloud moves overhead.....they would simply dim. But what happens if you're using a motor ? Brown out....or your system tries it's best to pull it out of the small battery bank.

In a IDEAL world, your attempt "might" work....if you could sit there all day and match your power use to the output of the panels every given second ( or maybe split second )....but I know I sure don't have time to do that......so I pull my excess needs ( wife flips on the oven, or the dryer, or a hair dryer, or anyone of a dozen other things ) from the grid, if the grid is up, and from my batteries ( on limited circuits.....she's just flat out of luck with the oven or the dryer....ahahahaaa ) if the grid is down.

Then, when we have excess power the house is NOT using, the meter turns backwards as we put it back on the grid. In off grid situations, if the battery was fully charged, and you weren't using the full power the panels produce, power simply wouldn't BE produced.....the panels just sit there at idle until a load occurs.

That's the WHY of what these other guys are trying to tell you when they say "It won't work"......because it won't work.

[Sunking]

Its called shunt regulation. In fact I have been using a shunt regulator ( have built a few kinds) for 4 years off one of my turbines, a otherpower style one, with capacitor support, and battery backup (but real small battery) It fact I cant say enough good things about it. the shunt is always on the mill rather than having a dump load that has to be switched on.

Shunt regulators have been around as long as the transistor. They work but extremely inefficient. They work by basically shorting out the power and burning the excess off as heat, just like a dump load. With a dump load you can at least utilize the heat, but with a shunt it is just wasted. That is why manufactures do not make them anymore.

[russ]

Discoveries? Personal discoveries possibly that would have been cheaper and easier to read about.

[analogmanca]

Ok, I wont get into a argument with the experts on what cant be done so I will just make this one post, and leave it to others to find out if its so or not, but I have done it and more. Its called shunt regulation. In fact I have been using a shunt regulator ( have built a few kinds) for 4 years off one of my turbines, a otherpower style one, with capacitor support, and battery backup (but real small battery)
It fact I cant say enough good things about it. the shunt is always on the mill rather than having a dump load that has to be switched on. I feel this is safer. The shunt regulator I am using now has a range of play (12.5 to 17 volts up to 300 amps) and is not a problem for my exanetrix, but rotary inverters that I put up pics of work too. I am changing my whole system around to work with this( panels and mill) my needs are modest (3 kwhrs/day) and am incorporating load sheading ( as needed)into my plan so I dont have to have a large bank. 6 t105s is my goal, with never more than 25% discharge.
Anyway, Experiment, and try out different things you may make some discoveries on the way ( PS, I am fully unqualified in anyway,no initails after my name, only know what works for me)

[billvon]

Option A sounds very interesting. Will the straight grid tie type inverter see the output of the battery backup inverter as the nice stable utility so it will agree to stay hot?

Within limits - yes

What is the interface? Just tie them together at the load side of the AC panel and the slave (conventional grid tie) syncs to the master (off grid battery backup inverter) and shuts it self off if the master goes down because of low battery voltage?

It is hard to use a completely conventional off grid inverter for this because they cannot sink power. Something like a Trace SW or an Outback GT inverter is a better idea since they will sink and source power, and thus can absorb some of the 'excess' power into the battery bank. This is called AC coupling. You also need to be able to regulate AC power to the inverter, something that a straight grid tie inverter can't do.

Here's a paper on the idea: http://www.outbackpower.com/pdf/tech..._WHT_Paper.pdf

[billvon]

Desire not to purchase and maintain a large (scary) battery bank.

While I understand that desire, you should know that all the other solutions you are considering (especially flywheels) are far scarier.

Years of lower efficiency conversion for sale to the grid. 85% vs 94%

With an Outback system you'd be above 90% even with batteries.

What I may have to do is build my 6 kw grid tie system and have a separate charge controller, off grid 4 kw inverter and a bank of 4 12 volt batteries. Reconfigure the DC strings and operate the whole thing sort of manually after the apocalypse.

If the apocalypse is the issue, just buy the parts and have them on hand so you can convert over in a few days. Batteries will be the one thing you can't "stockpile" so best live near a battery distributor and hightail it over there as soon as the first (zombie/looter/secessionist) shows up.

What's the short answer to keeping the 12 volt batteries from going bad while they wait three years to be called to action. Trickle charge for an hour per week? Discharge 25% once a month?

Floating them at a high state of charge.

I still want to build the flywheel. Something with lots of mass and low RPM like a big tractor wheel or a merry-go-round.

A 220 pound tractor wheel spinning at 5000 RPM (all the mass in the rim) can store about 3 kilowatt-hours if you can extract almost every joule from its motion. Again, though, if it gets loose (or even has a minor tread problem) it's not going to be pretty. And your house will shake a fair amount . . .

[russ]

thing sort of manually after the apocalypse.

That says it all - dead end

[Naptown]

Thanks,

I feel like I'm monopolizing your time.

Tractor wheel. Just enough energy to start the freezer compressor motor.

Option A sounds very interesting. Will the straight grid tie type inverter see the output of the battery backup inverter as the nice stable utility so it will agree to stay hot? What is the interface? Just tie them together at the load side of the AC panel and the slave (conventional grid tie) syncs to the master (off grid battery backup inverter) and shuts it self off if the master goes down because of low battery voltage?

Whoa slow down
there is a lot more to it than that.

[duncangalt]

A: You can look at hybrid systems that let you get a smaller amount of totally off grid power from a panel and battery combination and then add in extra power from straight panel to inverter components normally used for grid-tie, but now under the control of the battery powered inverter.


B: Trickle charge (in the automotive battery world) usually refers to a contant current charge that may or may not be safe for long term continuous connection to a battery. For Lead Acid batteries, what you want is a Float charge, which is a constant voltage charge that lets the battery take in just what it needs to make up for its self-discharge. The exact voltage to use will depend to some extent on the battery type and will in any case need to be temperature compensated.

C: Go for it! But do some calculations of how much energy is actually stored in such a high mass, low speed system, and more importantly, look at how you will be able to extract constant-frequency AC from the flywheel as it slows down. It can be done, but it takes more than just gearing a generator head to the flywheel.

PS: If you are not in a hurry and are seriously looking at Sunny Boy, do a google search ("Sunny Boy TL-US"), including this link, and also look on this forum for discussions and speculation about the not-yet-shipping Sunny Boy 2000/3000/4000 TL-US series.

Thanks,

I feel like I'm monopolizing your time.

Tractor wheel. Just enough energy to start the freezer compressor motor.

Option A sounds very interesting. Will the straight grid tie type inverter see the output of the battery backup inverter as the nice stable utility so it will agree to stay hot? What is the interface? Just tie them together at the load side of the AC panel and the slave (conventional grid tie) syncs to the master (off grid battery backup inverter) and shuts it self off if the master goes down because of low battery voltage?

[inetdog]

Great feedback. Thanks.

You seem to get the point (s)

Big PV array that's useless after the grid goes down.
Desire not to purchase and maintain a large (scary) battery bank.
Years of lower efficiency conversion for sale to the grid. 85% vs 94%

A. What I may have to do is build my 6 kw grid tie system and have a separate charge controller, off grid 4 kw inverter and a bank of 4 12 volt batteries. Reconfigure the DC strings and operate the whole thing sort of manually after the apocalypse.

B. What's the short answer to keeping the 12 volt batteries from going bad while they wait three years to be called to action. Trickle charge for an hour per week? Discharge 25% once a month?

Capacitors will probably be part of the eventual technology solution. I'm not a big environmentalist but lead acid batteries as part of the "Green Energy" solution is kind of comical.

C. I still want to build the flywheel. Something with lots of mass and low RPM like a big tractor wheel or a merry-go-round.

A: You can look at hybrid systems that let you get a smaller amount of totally off grid power from a panel and battery combination and then add in extra power from straight panel to inverter components normally used for grid-tie, but now under the control of the battery powered inverter.


B: Trickle charge (in the automotive battery world) usually refers to a contant current charge that may or may not be safe for long term continuous connection to a battery. For Lead Acid batteries, what you want is a Float charge, which is a constant voltage charge that lets the battery take in just what it needs to make up for its self-discharge. The exact voltage to use will depend to some extent on the battery type and will in any case need to be temperature compensated.

C: Go for it! But do some calculations of how much energy is actually stored in such a high mass, low speed system, and more importantly, look at how you will be able to extract constant-frequency AC from the flywheel as it slows down. It can be done, but it takes more than just gearing a generator head to the flywheel.

PS: If you are not in a hurry and are seriously looking at Sunny Boy, do a google search ("Sunny Boy TL-US"), including this link, and also look on this forum for discussions and speculation about the not-yet-shipping Sunny Boy 2000/3000/4000 TL-US series.

[duncangalt]

Batteries only for the Zombie Apocalypse

Great feedback. Thanks.

You seem to get the point (s)

Big PV array that's useless after the grid goes down.
Desire not to purchase and maintain a large (scary) battery bank.
Years of lower efficiency conversion for sale to the grid. 85% vs 94%

What I may have to do is build my 6 kw grid tie system and have a separate charge controller, off grid 4 kw inverter and a bank of 4 12 volt batteries. Reconfigure the DC strings and operate the whole thing sort of manually after the apocalypse.

What's the short answer to keeping the 12 volt batteries from going bad while they wait three years to be called to action. Trickle charge for an hour per week? Discharge 25% once a month?

Capacitors will probably be part of the eventual technology solution. I'm not a big environmentalist but lead acid batteries as part of the "Green Energy" solution is kind of comical.

I still want to build the flywheel. Something with lots of mass and low RPM like a big tractor wheel or a merry-go-round.

[inetdog]

A subset of the "Magic Smoke" department.

Or, as the lithium battery powered light enthusiasts love to say, "venting with flame."
Still not quite an explosion, but much more entertaining than simple "venting".

A key component of the flywheel designs for vehicle energy storage is a very strong casing (containment vessel?) to hold in the shrapnel when the flywheel overspeeds or suffers a heavy G shock.

[Vern Faulkner]

any such experiments should be kept well separate from wives who do not enjoy large thermal or rapid disassembly events.

A subset of the "Magic Smoke" department.