Solar panel power

[Guest JudgeMental]

AliB - 2010-07-29 12:08 AM

 

BGD - 2010-07-28 11:28 PM

 

I'm confused by your comment about the alternator having to "work harder.....which makes the engine work harder" without your addition of solar panels.

Have a look at page 1 on this thread.

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=19940&start=1

 

That is an entirely different thread, regarding running 12v air conditioning which is very demanding of power. What has it to do with charging battery's or solar panels.......

[MandyAndy]

There are times when the word Anoraks just has to spring to mind. (lol) (lol)

 

We have large van, huge wind resistance , solar panel and 2 batteries, they work really well and we wouldn't be without them now.

 

There how easy was that!!! :-D

 

Mandy

[Dave Newell]

Yes the alternator is spinning all the time (although some vehicles now utilise an electromagnetic clutch to disengage it when not required) but it is not generating lots pf power all the time. It will increase its current output to accomodate the load placed on it whether that be from headlights wipers etc or batteries requiring charging, they all impose a load on the alternator which it will meet by increasing its current output. In doing so it imposes more load on its drive system i.e. the engine which will use more fuel to provide the extra power required. You used to be able to see this effect by starting your engine and with it idling load the electrical system (switching headlights, wipers, heated rear screens etc to on) and watch the revs drop, modern electronic engine management compensates for the higher loadings by adjusting throttle/fueling to maintain a steady tickover so you don't notice it any more.

 

Additional fuel used due to recharging leisure batteries is likely to be in the same order as that required to push a solar panel through the air, virtually unmeasurable.

 

D.

[AliB]

JudgeMental - 2010-07-29 1:17 AM

 

AliB - 2010-07-29 12:08 AM

 

BGD - 2010-07-28 11:28 PM

 

I'm confused by your comment about the alternator having to "work harder.....which makes the engine work harder" without your addition of solar panels.

Have a look at page 1 on this thread.

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=19940&start=1

 

That is an entirely different thread, regarding running 12v air conditioning which is very demanding of power. What has it to do with charging battery's or solar panels.......

 

The thread discussed the loading effect on an alternator with a description of why this will in turn load the engine. Which I thought was BGD's question.

[BGD]

AliB - 2010-07-29 8:56 AM

 

JudgeMental - 2010-07-29 1:17 AM

 

AliB - 2010-07-29 12:08 AM

 

BGD - 2010-07-28 11:28 PM

 

I'm confused by your comment about the alternator having to "work harder.....which makes the engine work harder" without your addition of solar panels.

Have a look at page 1 on this thread.

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=19940&start=1

 

That is an entirely different thread, regarding running 12v air conditioning which is very demanding of power. What has it to do with charging battery's or solar panels.......

 

The thread discussed the loading effect on an alternator with a description of why this will in turn load the engine. Which I thought was BGD's question.

 

 

 

 

 

 

Thanks Ali - but the postulations in that thread are the same as mentioned above in this thread, and I still don't see the suggested logic.

 

Have a look at Wikipedia or other source references.

 

The alternator is a mechanical device...either windings on a spinning shaft rotating inside stationary magnets, or magnets on a spinning shaft rotating inside stationary windings.

 

The "load" or sapping of engine energy due to this mechanical item is purely a physical ones, due to inertia and friction.

Because the alternator is physically and constantly harnessed to the engine crank (usually via a belt), it is being spun by the engine at all engine speeds, using a constant ratio.

 

Whether or not any on-board electrical systems are asking for electrical power as you drive along doesn't in my view affect the mechanical "sapping" load that the alternator places on the engine.

The alternator does not turn any faster, there is no greater friction or inertia.

All that happens is that an electrical exciter "gate" opens, allowing the electricity that the alternator is always generating to be fed through, via rectifier and voltage regulator, to those other items (batteries et al).

 

 

So again, I ask the question of those more knowledgeable.....why do people say that when the vehicle is using the electric power that the alternator is always producing as it spins in fixed linkeage with the engine to which it is always harnessed, do they believe that the engine is somehow more mechanically loaded, and thus has to work harder, than when the alternator is generating exactly the same amount of electrical power but that power is not being fed through to those other things?

Such a suggestion simply doesn't make sense to silly old me.

 

[pkc]

In a vehicle system any load is sensed by the control device which in turn increases the amount of current to the field coils, which exerts more drag on the alternator.

An analogy, Your are pedaling a bicycle along a level road at a fixed pedal speed, on encountering a hill the load increases even though you maintain the same pedal rate. I.e red face, sweaty armpits.

[BGD]

pkc - 2010-07-29 10:44 AM

 

In a vehicle system any load is sensed by the control device which in turn increases the amount of current to the field coils, which exerts more drag on the alternator.

An analogy, Your are pedaling a bicycle along a level road at a fixed pedal speed, on encountering a hill the load increases even though you maintain the same pedal rate. I.e red face, sweaty armpits.

 

 

 

 

 

Thanks pkc - but I still don't see it.

The rate of changing the polarity of the ions isn't (except at a quantum mechanics level) a physical change. No extra physical drag is exerted. The rate of spin and thus physical drag remains constant (relative to any given engine rpm rotation) regardless of electrical output being utlilised to reahcarge batteries/feed headlights etc, or "wasted" if no other electrical systems need it at that time.

 

The analogy to a pedal bicycle seems to me to be a red-herring.

It relates to the strain on the engine, not the spinning of the alternator: it's the additional "bang" physical force the engine needs to generate in order to move the vehicle weight up an incline rather than on the flat (having to overcome greater centrapetal force (ie "more" gravity)) when travelling at the same speed.

If whilst going up that hill you turn the headlights on, you're not physically straining the engine any more at all, there's no more drag resistance on the engine; you're simply making use of the electrical power that the always-spinning alternator is generating all the time anyway.

 

(I think..........:-S )

 

[Guest JudgeMental]

I think Dave answered it very well *-)

 

its all about load?

 

I remember with my old westfalia VW when the a/c compressor came on the engine would shudder......but a solar panel? come on!

 

 

[pkc]

Bruce, I’m only going to say this one more time then I’m off to the pub,

 

“In a vehicle system any load is sensed by the control device which in turn increases the amount of current to the field coils, which exerts more drag on the alternator”

 

BGD, 10.17 am.

 

The "load" or sapping of engine energy due to this mechanical item is purely a physical ones, due to inertia and friction. Wrong.

 

Whether or not any on-board electrical systems are asking for electrical power as you drive along doesn't in my view affect the mechanical "sapping" load that the alternator places on the engine. Wrong.

 

Whether or not any on-board electrical systems are asking for electrical power as you drive along doesn't in my view affect the mechanical "sapping" load that the alternator places on the engine. Wrong.

 

To come at this from another angle.

Assume your van is not equipped with a battery, driving along at a steady speed and throttle setting you then turn on the headlights, where is the extra energy going to come from? If it dosn’t come from the alternator with a consequent drag on the engine, from where?

If you come up with a better theory PM me and we can set up a business called ‘Perpetual motion Inc’.

 

PS, Don’t be giving me any of that ‘quantum, polarity of the Ions old guff, talk about red herrings

:D

[AliB]

Regarding alternator load Dave N is, as always on the ball. The loading on an alternator due to differing power requirements is really insignificant and not worth worrying about.

However, it does exist. The power draw on an alternator will increase the current through the coil windings. This makes for a stronger electromagnet, giving more magnetic flux. Stronger magnets are harder to pull apart hence it is harder to rotate or drive the alternator. The mechanical frictions associated with the bearings and drive belt far outway the effect of changing magnetic resistance.

Electrical accessories, fit and forget them. You will never be able to measure the effect on fuel consumption.

[BGD]

pkc -

"To come at this from another angle.

Assume your van is not equipped with a battery, driving along at a steady speed and throttle setting you then turn on the headlights, where is the extra energy going to come from? If it dosn’t come from the alternator with a consequent drag on the engine, from where?"

 

 

 

 

 

For your return from the pub..........

 

 

 

 

It is not "extra" energy. (Unfortunately, otherwise we could indeed get rich!)

 

The alternator is generating that energy all the time it is spinning.

And thus the drag that it exerts on the engine as the engine spins it, is there all the time.

It's a closed-loop, mechanically fixed-linkage-speed system.

 

All you've done by turning on the lights (which you can indeed do without having a battery in the vehicle, once the vehicle is running) is to activate a switch which activates the alternator exciter, the regulator, and thus route it through the wiring to the lights, and thus to vehicle "earth" instead of not using it to operate any appliances, in which case it returns straight to "earth" via the alternators body/earth lead.

(I know a 12 volt DV system isn't really an "earth" system, but I reckon it's easier to visualise using that label) :-D

 

Thus generating that electrical power does indeed place a drag on the engine. But it does so whether you "draw off" (use) that electrical power to operate something or not.

It's a constant mechanical drag on the engine, in fixed ratio to engine spin-speed, that drag is not related at all to what you do with the energy it's producing.

 

An alternator rated at (say) "N" electrical output when spinning at (say) 4,000 rpm will be producing that "N" output whether you choose to utilise it/some of it to operate some in-vehicle electrical equipment or not.

It doesn't stop producing that electrical output if you turn your lights off - it's still spinning. In simple terms the electricity simply flows back round the closed loop within it, rather than being diverted outside of it to the appliance (and thus round a longer loop).

 

 

Cheers,

 

Bruce.

[colin]

Bruce, how do I put this nicely? read daves post it tells you what happens, i.e. the load the alternator puts on an engine varies with the power it in turn produces, IT DOES NOT IMPOSE A CONSTANT LOAD ON THE ENGINE. If you don't understand this from the previous explainations please let us know and I will shout louder, as I don't know any other way of getting the info across.

p.s. part of my training is in electronic engineering. o.k. guided weapons systems are a little different from those found on a van, but not that much different

:D

[pkc]

Nicely put Colin,

Bruce, don't feel bad I have not the faintest idea how to play the saxophone (lol)

Just promise me you won't go into guided missile design :D

 

So, back to the pub then.

 

[BGD]

"IT DOES NOT IMPOSE A CONSTANT LOAD ON THE ENGINE."

 

Nope.

It does so.

 

 

 

(Puts finger in ears).

 

La la la la la, dum dee dum dum dum..... ;-)

[Brian Kirby]

OK.  You win!  The generator exerts a constant load on the engine, by generating a (more or less) constant amount of electricity. 

So, where does all that unused electricity the alternator keeps generating go?  It has to go somewhere - it can't stay in the alternator.  It is suficient to meet the peak demand of all the installed equipment, so it greatly exceeds the normal demand from the vehicle in daylight on a dry day.

This is such fun!  :-D

[BGD]

Brian Kirby - 2010-07-31 4:26 PM

OK.  You win!  The generator exerts a constant load on the engine, by generating a (more or less) constant amount of electricity. 

So, where does all that unused electricity the alternator keeps generating go?  It has to go somewhere - it can't stay in the alternator.  It is suficient to meet the peak demand of all the installed equipment, so it greatly exceeds the normal demand from the vehicle in daylight on a dry day.

This is such fun!  :-D

Aaah, but Brian - as you and I (and Newton when he devoloped his "First Law", and more recently Stehen Hawking through his Quantum Physics work) all know, yours is of course a trick question.Because it isn't energy.It is only potential energy.Until the tap is turned on the energy does not flow...the ions are not polarised. It exists only as potential, not as physical, energy until "freed" from the spinning alternator by the closing of a switch.(I refer you Sir, to page 199 of the Stephen Hawking book "A Brief History of Time"). ;-)

[Brian Kirby]

Why yes, but when the potential is turned into actual energy, actual, as opposed to potential, fuel has to be consumed to power the conversion. 

You're looking for a free lunch.  :-) Realising the actual electrical energy does as described above, it increases (via the control module) the current flowing in the field coils, which strengthens their magnetic fields, so increasing resistance to rotation of the commutator.  To overcome that increased resistance the engine has to work harder, so consuming more fuel. 

The control module limits the amount of current fed from the commutator to the field coils, to prevent the run-away loop that would otherwise allow the alternator output to tend to infinity - and melt the lot!

An alternator is, crudely, an AC motor in reverse.  Try applying increasing power to an AC motor (better not use a mains-powered motor if doing this at home! :-D).  In response, it tries harder to rotate.  So, an alternator being rotated at constant speed under increasing load, becomes progressively harder to rotate.  If the revered Mr Hawking actually says otherwise, he is talking b*****ks!  :-)  Unthinkable, what?

[pkc]

Just been drinking with Newton down at the Pig and Whistle,

He asked me to point out that a spinning rotor has Kinetic energy, potential energy is what caused the apple to fall on his head.

Our landlord, Mike Faraday said that he knows for a fact that alternators don't have commutators so you must both be talking b*****ks.

when I challenged him about this he puts fingers in ears and went....

 

........La la la la la, dum dee dum dum dum.....

[Brian Kirby]

pkc - 2010-07-31 9:54 PM Just been drinking with Newton down at the Pig and Whistle, He asked me to point out that a spinning rotor has Kinetic energy, potential energy is what caused the apple to fall on his head. Our landlord, Mike Faraday said that he knows for a fact that alternators don't have commutators so you must both be talking b*****ks. when I challenged him about this he puts fingers in ears and went.... ........La la la la la, dum dee dum dum dum.....

OK, I'll come quietly!  :-)  I said commutator when I should have said rotor, and I said field coil when I should have said stator.  It's a memory thing, and the motor/alternator bits all look similar.  :-D

However, I am reliably assured that automotive alternators do, indeed, have commutators, though these are of slip ring type and not segmental, so your landlord owes me a pint - or he goes back in his cage! 

I am also assured that added demand is met by added output, resulting in increased Wattage, usually by varying Voltage.  If the output in Watts increases, so work done by the engine in driving the alternator must increase, so fuel consumed must also rise.  Free lunch (plus pint) anyone?  :-)

[pkc]

*

I am reliably assured that automotive alternators do, indeed, have commutators”,

 

Nope.

They do not so.

A C you see,

Sorry Brian you need to rectify this*

:-D

 

puts fingers in ears

La la la la la, dum dee dum dum dum.....

 

Mine’s a pint of Bulmers on ice, cheers Brian

:D

[flicka]

I think this settles it ;-)

http://www.smartgauge.co.uk/alt_mod.html

[art338]

So, would life be more efficient if there was no alternator fitted and all electrical neccesities driven from a seperate internal mounted battery which is re-charged every day?

 

art

[Brian Kirby]

pkc - 2010-08-01 8:28 PM * I am reliably assured that automotive alternators do, indeed, have commutators”, Nope. They do not so. A C you see, Sorry Brian you need to rectify this* :-D puts fingers in ears La la la la la, dum dee dum dum dum..... Mine’s a pint of Bulmers on ice, cheers Brian :D

Ah, it's that Bulmers on ice you see: it causes confusion!  1  The alternator output is rectified to DC at the alternator.  2  The rotor in automotive applications is electromagnetic, and electricity has to be passed to the rotor coils to excite them.  (Inductive alternators are not normally used on automobile installations - in fact, so far as I can ascertain, are not used at all.  Permanent magnets are used on some bike alternators, but the outputs available versus cost rule them out for the higher demands in cars/vans.)  Getting the current to the rotor involves brushes, and the aforementioned slip ring commutator.

So, mine is still a pint of proper beer, or even better, cyder - of the type that is not served on ice.  :-)

Not sure I'd try that trick flicka found on a vehicle with computer control of everything.  They don't mention it as a problem, but everything, not just the batteries, would be fed the higher voltage.  Might be costly?

[pkc]

Brian,

 

We will have to agree to disagree

One alternates, and one's DC

When the phases alternate

They are rectified by solid state

Whilst in the old type dynamo

A rotary switch converts the flow

Perhaps Clive could show you later

A slip ring’s not a commutator!

 

Please stop now, you are driving me to drink.

Well go on then, just a half please.

(lol)

[Brian Kirby]

The only reason I referred to the slip ring as a commutator was because that is how I found it described on a couple of "alternator" websites.  Surely "commutator" is a generic term for a device designed to conduct electricity between a spinning component and a static component in a motor, dynamo or alternator?  Segmental, and slip ring, just being two types of commutator.  At least, that was how I understood what they were saying, but I'm not an electrical, or electronics, engineer.  Whatever it may be called, we seem only to disagree over what to call it, not over the principle of what it does and how it works.  So, let's just settle on Fred.  :-D