Question about "Power Splitting" 1

[shockflame]

Hello, I would like to know if there is a device for splitting power the way I describe it in the example below.

Suppose I have a minature hydroelectric plant that can generate 100 Watts. It is only hooked up to appliance A and a battery. At any given time, Appliance A uses X Watts. X may be varied anywhere between zero and 100 Watts, inclusively (0 and 100 are both acceptable values).

Is there such a device that would, at all times, allow the power not used by Appliance A, which is (100 - X) Watts, to be transferred to charging the battery?

 

[rbulsara]

I suppose you can devise a sensing circuit and output that will monitor the power to the applicance and in repsonse provides a signal to adjust the rate of charging the battery.

Don't ask me how...not my expertize..but it sounds possible.

Depending up on how much the batteries are charged, the sum of two consumptions may not always add up to 100, unless you can adjust the load X...so have total of 100 which to sounds like catch 22.

 

[itsmoked]

Well you aren't following the standard design philosophy of running your appliance that can take anything it wants from the battery. Then you just charge the battery with the generator. You generally need something to disconnect the load if the battery drops too low to protect it and in some cases the load or the mission.

Now are you going to NOT use the battery to run your load ever?

 

[ccjersey]

Yes it's very simple and its a dc generator, dc appliance and a battery, of correct voltage to supply the load and be charged by the generator. load would have to be greater than the output of the generator sometimes or the battery would overcharge unless you can regulate the generator output.

That may not be what you were thinking of though.

Jim

 

[itsmoked]

Okay.. Let me ask this. Does this hydro have no control and so it needs a relatively constant load to keep from overspeeding. Is this what you are doing?

 

[shockflame]

Alas, I forgot that hydro generators create AC! That does complicate things, since what I was orginally referring to came from DC. Pray forgive me for creating such a troublesome example: I was only trying to set up a simple scenario to get a problem solved. But since you guys are so keen on the subject, I will fully describe the actual situation below.
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I have been thinking about solar power in my spare time for the last several weeks. Solar-Electric modules, as you all know, generates DC electricity. Suppose I make a car that runs purely on solar power (Assume that the cells are very, very efficient). Appliance A from my example becomes a DC motor, and the battery remains the battery (to make the battery's place more clear, lets put the battery inside a DC battery charger; I don't want to deal with too many things at once, like switching supplying power to the motor from battery instead of modules).

For convenience, let's keep the number values from above: the motor uses X Watts, where X is a real number from 0 to 100. For additional convenience, assume the Solar cells generate 100 Watts at all times.

What I want to do is to prevent waste of power unused by the motor, by channeling excess power to charging the battery (which I was thinking of using for something like night-driving).

Is there a device, then, that will at all times transfer (100 - X) Watts to charging the battery? In essence, is there a electronic thing that allows ALL leftover power from motor to be used for charging the battery?

I got this "storage of excess power" idea from reading something about how in some places a hydroelectric plant will use all UN-USED power during the daytime to pumping water uphill into a resovoir. During nightime, the water from the resovoir would assist in peak power usage.

I would appreciate any assistance.

 

[itsmoked]

shockflame; These two scenarios are very different. In one case there is a battery, in other, there is a synchronous machine. The excess power from a nuke running full out can be kept constant by increasing the pumping rate into the pumped storage. The power going elsewhere changes relatively slowly over minutes. In the case of a car the energy flow into the motor changes nearly instantaneously.
Furthermore the motor can pull more than the solar panels, often, probably all the time, unless your car looks like a giant cockroach.

Next what is the difference from using all the power to charge the battery and use what is left over for the motor if the motor needs more it takes more. If the motor needs more than the solar can supply it takes that too! The object is to motivate the car not to only move the car at the rate the solar panel happens to put out, *when* it can put out.

Sorry to be throwing cold water on the scheme but if you are talking a car/vehicle you want the solar to charge the battery and the motor to run from the battery. PERIOD.

Now of course the you can do what you are proposing to do. The answer is yes! Is there an off the shelf device? Not that I have ever heard of. I have done that very thing but generally you must measure the power from the energy source measure the power being used and use this to control the measured power going to the batteries. Generally this means the controller running, in your case, the motor, is also doing all the other tasks described. This would be something custom. With a capital "C". So again the answer is no there is no device, (that I have ever heard of), but it can be done. It will also probably have some efficiency issues.

 

[shockflame]

Hey itsmoked, thanks for your time. Sorry it took me so long to say something, but I was weighed down the whole day by other issues. Overall, I was able to follow your lucid and expert discussion of my theory. However, I just want to make sure that I completely understand.

"The excess power from a nuke running full out can be kept constant by increasing the pumping rate into the pumped storage. The power going elsewhere changes relatively slowly over minutes. In the case of a car the energy flow into the motor changes nearly instantaneously."

Can you please explain the significance of this instantaneous energy flow of the car?

In addition, I know that in cars the AC battery may be simultaneously charged and used. Does this apply to DC batteries, too? (I am merely extending off of your suggestion of hooking the motor feeding directly off the battery, and the battery charged by solar cells at same time; my traditional experiences of DC batteries have been limited to charge, then use)

I look foward to your comments on these. Again, thanks.

 

[GTstartup]

Sorry, maybe I am missing something, but this seems a simple issue.

If you have a generator feeding an appliance and you want to charge a battery with the "excess" power not used by the appliance then you need a battery charger in parallel with the appliance. However, when the battery is fully charged, and the energy to the turbine is constant, then the turbine will increase in speed. To avoid this, you need to control the energy input to the turbine.

 

[itsmoked]

Hi shockflame,
I was showing that power plant control can be achieved by incremental, possibly even human-hand-on knob type control.
Whereas an electric vehicle switches from off to heavy acceleration, coasting, steady state, etc. So a smooth divvying up of the energy for a vehicle is more problematic.

There are no AC batteries. Batteries convert chemical energy via electrode potentials which are fixed mechanical structures in a battery. Hence having a battery be AC would require these structures be somehow oscillated... They aren't. No AC batteries.

So we drop to DC batteries or batteries. Now if you look at the situation of solar panel, batteries, motor, you will see that you have two systems. One is a system to charge the batteries with solar. The other is to run the motor at different speeds from the battery.

The motor will draw far more than the panels can ever provide. So you hook the motor to the battery. You would need to control the power from the panels to the battery so that the batteries are not overcharged under the right conditions. So, you utilize a solar to battery charge controller to charge and maintain the battery. You utilize a speed control to run the motor efficiently from the batteries.

Look at it this way; the pumped storage allows the power company to supply more power than the nuke can supply by itself during a peak requirement but because even the nuke can output more than needed during other parts of the day it has some surplus to send to the pumped storage. While this sounds like what you looking for, there is a subtle difference. Specifically in your case the solar can never supply the motor on its own and the process of shifting from the solar/battery/motor is a different process than the nuke/city/pumped storage.

As I read this I can see your confusion... Let me try some more. The shifting of the nuke/city/pumped is a process where the different energy flows can be accomplished thru leading/lagging synchronous machine adjustments. The solar/battery/motor system is not controllable in this same manner. There are conversions in the car processes. Also whereas the nuke just 'runs' the solar comes and goes.

If you want better efficiency in the car you want the solar charge controller to maintain the load on the solar panels in their most efficient area.


GTstartup it is not that simple. If you have a power source that is limited you cannot feed the appliance AND charge the battery with a normal charger. You must constantly limit the chargers consumption to less than the total available minus the appliance consumption. This is odd. As I stated in my previous post, not impossible just odd. Furthermore what happens when the solar can't even provide enough for the appliance and now power must come from the battery to the appliance? Where is the solar power going? Is it charging the battery or going to the appliance? Both?

shockflame was also talking 100W type hydro. 100W hydro rarely, if ever, has any form of prime mover control. Its speed would be load controlled.

I had a prof who built a low-head hydro plant into a large river cutting past his house. The river split off into some little 10 foot across creeks. He used one of these. He had no flow control so he ran his 15,000W hydro with load control. It was very funny walking through the woods on a warm sunny day to come to 7 fan forced space heaters pointed in all directions, running.

 

[shockflame]

Itsmoked, I see your point. When I originally thought of this, I was simply concerned about extending the life of the battery and did not think about the details: I was more engrossed in other logistics, since solar panels can run like hell for 30+ years and have no problem, whereas battery life has a direct correllation to usage (Hence solar plants hardly ever need to replace a module in the array but car batteries are often changed because the cathode/anode chemicals no longer work right due to "boiling" degradation).

However, now that you have mentioned it, connecting the circuit to have subsequent solar-->battery-->motor presents a very safe alternative, since doing that eliminates the problem of having a sensor/mechanism that would switch the motor power supply to the battery whenever the panels provided too little power. Now that I think about it, the wiring will be a bit simpler. But again, I was concerned with extending battery life.

In addition, I understand your constant reminders of the puny power of current solar panels. I admit it too, they're just not up to par right now. But what about 5, 10 years down the road? Maybe then the solar panels in this scenario could provide so much more power, to the point that even though the motor sucks titanic amounts of power from the battery (or batteries, for that matter) the solar panels will produce enough to charge up the battery. By this I mean that power going into the battery will be greater than power going out of the battery. I'm willing to wait, though. But I digress.

Let me get your nuke/storage explanation straight for the last time:
The nuke (or a hydroplant) differs from a solar panel simply because there will never be a chance for the solar cells to produce excess power to put in storage.

Just checking. This seems to be what you're saying in
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"Specifically in your case the solar can never supply the motor on its own and the process of shifting from the solar/battery/motor is a different process than the nuke/city/pumped storage."
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Now that I think about it, they do involve different processes. Hydros/nukes are chiefly turbine-based using heat, so they can easily switched to pump water to storage whenever there is excess power. Solar panels involve pure electrical power transfers. However, it still looks like they still share the same concept, even though the solar power idea is more complicated.

Give me a thumbs up or down so I can be sure. Itsmoked, thanks a lot for your posts. You have solved quite a problem.