Measuring the Reactive Load

[Murlin]

Howdy folks,  I had a question for some of you electrical Guru's.

My brother-in-law is a nuclear engineer.  He and I were having a discussion the other day about how the electric company measures the difference between the sign waves of the voltage vs the reactive load in your house and that is how they charge you for the electricity you use.  The two sign waves get further and further apart and causes the wheel on your meter to spin faster.  I am not sure if I said all that right because I couldn't understand half of what he was telling me.

But if I understand it correctly, the reactive load is all the little coils, motors, and such on all the appliances and gizmo's you have running in your house drawing current.  (you could actually take a couple of induction motors and hook them up in such a way as to supply all the reactive load in your whole house, thus stopping your meter and just draw true current from the grid, but we wouldn't want to do that now would we ;-)  )

Anyways, I was thinking if there were a way to measure the reactive load of the devices you had running, you could use that information to control the output of a turbine if it had pitch control....kinda "matching the load" in reverse.

If I could make a circut that measures the reactive load currently being produced, one could adjust power output and minimize the amount of current that is drawn from the batteries when the wind was pushing the turbine to full power. Instead of dumping all that extra load, you would just make the power you need....

Anyways just more crazy thoughts...

Murlin teh daydreamer...  

[Flux]

Your meter measures, and you pay for watts.

You don't pay for the reactive component. The suppliers have to be able to supply it, so they encourage you to operate at a good power factor. In industry there is often a financial incentive to keep to a high power factor and it is worth investing in power factor correction.

It is fairly easy to correct for the conventional reactive power from inductive loads.

A factor that is becoming of increasing concern is low power factor from distorted load current. Anything using a conventional rectifier causes a low power factor and supply harmonics that can't be corrected by conventional leading power factor methods. With the increasing use of HF ballasts for lighting there is a greater emphasis on power factor correcting rectifiers, that draw current over the whole load cycle rather than only at the peak.

I don't see how this directly relates to wind power into batteries. The load has to match the true power (Watts). Reactive power will not be much of an issue, even high power factor rectifiers seem to offer little improvement. The average rectifier has a pf of about .95 into a battery.

Motor conversions and iron cored alternators may have more reactive component and this will alter the load characteristic, but you still need to match the real power.

When you get into queer alternators such as transverse flux machines the leakage reactance becomes so high that conventional diode rectifiers can't extract much power from them. You can extract power with a force commutated rectifier, but it is still the real power that has to be matched to the load. Reactive energy only causes losses from the extra current and associated I^2 R loss. there is no power loss associated directly with reactive component.

Flux

[Murlin]

"I don't see how this directly relates to wind power into batteries. The load has to match the true power (Watts)"

Ahhh...well then there ya go.

I thought that by measuring the reactive load, you might be able to get a pretty good picture on the true current load.

The triangle has reactive, percieved and true applied loads....or so I was told...

And my brother in law told me that it would be easier to measure the reactive load to paint a fair picture of what was going on...

I probably just misunterstood him...thanks

[WXYZCIENCE]

Murlin, the power company got around the power factor problem by what is called delivery charge. All of the power lost in the lines, is added to the consumer's end.


Joseph

[powerbuoy]

In single phase terms:

The power in watts delivered (or better consumed) is W=E*I* cos phi

W=Watts

E= Volts

I= Current

Cos phi = power factor

This is the power you actually use for work, also called effective power.

The utility produces what they call apparant power, it's easily calculated by E x I

Then there is also reactive power, which is clculated W=E*I* sin phi

If all your loads would be truly resistive (may be heaters) then you would not need to worry about the power factor too much and the cos phi would be close to 1.

In this case you consume almost exactly what the utility delivers (effective power = apparant power). They would be very happy with you.

Also it needs to be noted that the voltage sine wave and the current sinewave are in sync under this condition.

However, your typical customer might have a variety of loads, mostly inductive loads like motors.

An inductive load will cause the current wave form to lag behind the voltage waveform. The magnitude of the power wasted in the process is W=E*I* sin phi. This wasted power causes additional heating and is basically a loss to the utility.

The catch with the utility is that they have to produce enough juice (apparant power) to your house to cover for both, your effective power needs and the wasted reactive power. It is good to know though that they can only bill you for the effective power. The way a meter is connected basically determines what's being measured. The reactive power part is basically bad luck on their side. You can make them happy by adding capacitance to your motors to bring the power factor closer to unity. Unfortunately, you'll not receive anything for it, ...maybe not even a thank you.

Powerbuoy

[stephent]

You mean add enough capacitive reactance to cancel the inductive reactance?

[Murlin]

Thanks for the explanation Powerbouy..I think I was misunderstanding what by brother in law was trying to tell me.

I am sure there was something good in there somewhere in what he was saying, but it went over meh head

More research on this matter is required.....alot more it seems

Murlin teh whew....

[Murlin]

Ya he said something to that effect, but like I said it all went too far over my head to make any sense out of it...

[Murlin]

I wondered what that extra charge was...thanks

[ghurd]

Steel mills do just that. The power company checks to be sure its right.

G-

[Murlin]

OK so measuring the reactive load was not the thing that was to get me to where I wanted to go.

Here's what I wanted to do:

Lets say I have a turbine that produces 10KW peak output.

When the wind is pushing the turbine to full power, if you are not using all that power, you are dumping it.

Would it be better just to dump it?  Or pitch the blades to where it is not making more power than you are using?

It just seemed to me that decreasing the power output would save on all the electrical components.

But I need some way of measuring my power usage so when I turn on a device, the system measures how much current is needed, and if possible adjusts the output of the turbine to match the load.

Murlin teh question man...

[Flux]

Yes that makes sense. You need to measure real power, not reactive.

For an ac system you use a wattmeter or multiplier. For dc into batteries you can do the same thing or just assume volts are reasonably constant and measure amps.

You can buy wattmeter transducers that give a current or voltage out proportional to watts.

[Murlin]

In order for me to develope a computer program that will control my turbine, I need to be able to collect data and send it to a file in my HDD.

Then it gets simple from there.

But in order to do this I need to measure the output of the turbine and send that info to a file.

Then I need to measure the current being used on the other end and send that to a file.

The point to point control is easily done in a linear measurement of the distance of the pitch of the lead screw.  The angle of the blades is not really needed.  All the control can be linked to a liniar point vs the output of the turbine relative to the RPM.

I am going to use a servo instead of a linear actuator.

I was hoping to keep all the input devices analog.

I can see how to measure the output of the turbine, but measuring the amount of current that I am using is a little harder for me to get strait in my head since I am electriclly challanged

Thanks for sharing your expertise guys....

Murlin teh electrical retarded....

[commanda]

Seperating the forest from the trees.

Measure the battery voltage. Once it reaches the point where you would normally start dumping to a dump load, start feathering the blades to reduce power generated.

It's a fairly simple analog control loop.

Amanda

[scottsAI]

Hello Murlin,

Power meters only measure the real watts, not allowed to measure VA.

I sent letter to editor at Homepower, he confirmed real watts only.

Just confirming what everybody else is saying.

Not sure what your trying to do??

Do you desire to not back feed your utility meter? How are you doing that?

Trying not to use a load dump?

Why are you using a computer to control?

To control pitch you will need slip rings or wireless.

A PC draws 100watts, or 2.4KwHr a day, 72KwHr a month?

Takes a good sized wind gen just to make that much power, let alone having anything left for other loads..

About the electrical vs mechanical stuff. They're both the same.

Current is velocity of water flow

Voltage is pressure.

Wire is pipe. Gage of wire is the dia of pipe.

Resistors are valves

Switches are Gate valves:-)

Capacitor is accumulator.

PMA can generate a pressure and GPM based on wind speed.

Take it from there!

Have fun,

Scott.

[Murlin]

Howdy Scott

"Not sure what your trying to do??

Do you desire to not back feed your utility meter? How are you doing that?

Trying not to use a load dump?"

Me neither But I was wanting to make a system that was independant from the grid.

But I can definately see how you could use the grid to your advantage, and I guess it would be foolish not to capitalize on that.  Since batteries and inverters cost so much.  

"Why are you using a computer to control?

To control pitch you will need slip rings or wireless."

Well I already had a pc running 24/7 and thought I would just give it something to do for the fun of it. Sometimes I just like to do something that is cool ...

But I am back to being practical now and can see that I need to use microprocessor control.

Perhaps I could appease my quest for something cool by just being able to override the controls so I could shut down and monitor from remote PC  .

SammoPower had a very good Idea using a micro with a linear actuator.  That sure would be the most economical way to go.

I wanted to do something cool with servos...but the more I think about it, I keep reverting back to my original thought that you would not really have to make very precision pitch movements in order to keep a meltdown from occuring, and still end up with more power than from a set pitch on your blades. Unless you were trying to hold the turbine to a constant RPM like you are doing.

Then you would have to program your own EPRONG. Because you would need a good program that will make constant updates.

If you use motorized yaw, you would not have to use sliprings.

I was thinking that if your yaw only worked @ 200 degrees, then you would actually only have to rotate the yaw axis between 2 points 180 degrees apart.

The motor would only work a few times a month, when ever the wind totally changed direction. A study of the wind roses in my area confirmed that.

[scottsAI]

Hello Murlin,

SETI is what I have my idle computers doing!

Maxed out at 22 machines at 2GHz ea.

With Yaw control, yes 180+- is all you need. But you have to be willing to spin the machine around when it overlaps.

Something Cool.

Have you heard of a wind gen??

What more COOL do you need??:-)

I will be using wireless in pitch control, and tower control.

Along with a weather station for yaw control and pitch prediction.

I expect daily pitch corrections, starts out calm, winds pick up during the day...

Have fun,

Scott.

[Murlin]

Howdy Scott,

One more reason to be able to run your high tech turbine from a computer console.

All the motion controllers have to have a programmed exec.  A computer program where you could monitor and fine tune your turbine then download and update the exec, would be very useful.  You could have a program that writes the exec tapes.

This way you could could go somewhere and build any kind of genny, out of any materials, and be able to fine tune it and write an exec for the microprocessor.

"With Yaw control, yes 180+- is all you need. But you have to be willing to spin the machine around when it overlaps"

In normal operation, it spins around all the time. If you were not concerned with power interuption, you could just feather the blades and spin it around, no big deal.

I can see how if you are trying to keep a constant RPM that might not be desirable.

"SETI is what I have my idle computers doing!

Maxed out at 22 machines at 2GHz ea."

nice network

[Murlin]

Hi Amanda,

That is a good idea.  

Let me ask you an some ignorant questions .

How much battery do you need to be able to use the power of a 5 KW turbine?

I am assuming that you must channel all the power that the genny produces through a battery bank first and then invert it in order to get a good constant flow of energy to your devices.

I was hoping to be able to power a 5-hp motor. That needs at least 3500 watts.

Whenever there was enough power, and when needed to pump the water from my well to the tank..

It's going to be deep...900 feet  )

I am hoping to generate enough power to be able to float a large battery bank.

I am hoping to build a solar/wind system that is off the grid.

[scottsAI]

Hello Murlin,

I can wireless reprogram the code. To both pitch and tower micros.

Code fixes are not a problem.

Embedded micro draws less than 100mw of power.

Micro has 62k bytes of Flash, 8 K bytes of RAM. Plenty for controller.

I have considered using redundant micro processors...

Still thinking about it. For what they cost vs what they do, might be worth it.

Want the wind gen to run on it's own, will need wind direction sent in wirelessly.

Have fun,

Scott.

[Murlin]

Howdy Scott,

Yes it sure sounds like the puzzle is comming together nicely.

Hey last night I was thinking how you were doing all of the pitch control on the nose cone side and I figured out how to put computer pitch control on all Hugh's style turbines

One just has to drill a hole through the axial for the wires, not really a big deal at all.  To use the pitch control on existing turbines you would have to use wood blades since they are set so close to the tower.

But if you are making one from scratch, you can use foam core/composit that are super light, and set them farther from the tower.

Communications: Yes, wireless is definately the way to go.

It would cost alot to run E6 all the way to the tower but it could be done.

It would probably cost less than wireless, but then you have all those wires sissoring and trying to kink as it yaws and they are bound to break sooner or later then you have a splice.

Murlin teh fun, fun....

[Murlin]

OK I found a good like to my battery questions.

HOW TO SIZE YOUR BATTERY BANK:  there's a fairly simple formula for figuring how many of what kind of batteries you need for your power requirements.  Here's how it goes: first, you need to know how many watt-hours per day you need for your power system. That is simply square one!  Then, you take that figure time 1.3 - the fudge factor (as batteries and other components aren't 100% efficient) to get your "adjusted watt hours needed per day".  Now that you know that, take your adjusted watt-hours per day times the number of days of battery storage you'd like (we usually use at least a minimum of 3 and as much as 14); then take that number times 2 (for 50% depth of discharge--you never want to take your batteries lower than that), then take THAT number divided by your system voltage (probably 12, 24 or 48V)--and that equals the number of amphours of storage you need.  So let's use a figure--say you need 5000 watt hours per day; times 1.3 = 6500 "adjusted" watt-hours; take 6500 times 4 (for four days of storage) = 26000 X 2 (for 50% depth of discharge) = 52000; divided by 24 (system voltage) = 2166 amp hours of storage.

NOW, if you need 2166 amphours of storage in a 24V system, and you plan to utilize the Surrette batteries (above), divide 2166 by 460 equals 4.7...well, you can't have 7/10th of a battery, so you'd round it to five.  And since it takes four 6V batteries to make a set in a 24V system, you'd need 20 of the Surrette S-460 batteries to give you 5000 watt-hours a day, for four days, to 50% depth of discharge.

http://www.oasismontana.com/batteries.html

these are the batteries I plan on using...

[SamoaPower]

The Surrette battery is actually 350Ah capacity at the more conventional 20 Hour rate for basis of comparison. The 460Ah is at a 100 Hour rate. Another "big numbers game".

I suggest you limit the nominal discharge depth to 25% of ACTUAL capacity for decent lifetime. Rated capacity is fine for new batteries but after a year or so you should start using measured capacity if you don't want to kid yourself. Losing 8-10% per year would not be uncommon.

I think there's more bang-for-the-buck in the Trojan T-105. At $70 and 225Ah it's $0.31/Ah compared to the Surrette $225 and 350Ah at $0.64/Ah. It's also a good battery.

I would want a charge capability of at least 100 Amps to keep up that size of bank. Remember, undercharge is what kills batteries.

[scottsAI]

Hello Murlin,

Cheap wireless transceiver.

EVAL-ADF7025DB1 available here:

http://www.analog.com/en/prod/0%2C2877%2CADF7025%2C00.html

each end is $50.

FCC certified with enclosed antenna.

Just add micro: ADUC7022

Here: http://www.analog.com/en/prod/0,,762_0_ADUC7022%2C00.html

Eval board: $30

MiniKit for ADuC702x-series (ARM7®-core) Precision Analog Micro controllers

Serial communication at 300k baud, looks good to me.

You might buy the wire for less than $100, but adding in the slip ring or two, might just cost more.

How will the wired reliability be? Vs Wireless?

I'm all for the wireless programming.

Security is an issue, so working on a protocol (PGP like?), something simple yet offers protection.

Considering a serial Flash with a serial number or key, store all the new code in it first then flash the micro?

What do you think? I like to keep it simple yet not have anything screw it up.

Have fun,

Scott.

[Murlin]

I think those devices would work great Scott.

Very little power draw and you can still wireless update the exec.

Looks like just the right amount of puter power

Security is an issue I hadn't thought about...sure don't want some high school punk hacking into your network and burning up all your gennys.

The reason I wanted computer interphase was so if I built one for someone in a different state, I could send updates and do monitoring via internet and such without having to fly up there.

But for all practicality, those little chips may be the way to go.

I think I will do some experimenting with them also since they are so cheap.

You definately want the turbine to run on it's own, I never wanted it not to be self suffecient, I just wanted to be able to watch it from afar.....

Murlin teh feels like a mad scientist

[Murlin]

Great Sammo !!!

Many thanks...those are way cheaper

25%...wow..So I need a few more batteries than what that guys uses in his formula since he uses 50%..

Twice the number actually, but it is still cheaper..

I still think I can get a bank for under 2k....hopefully.

The inverter is going to be the expensive part...3500 buck for one.

I would appreciate any links you guys have to inverters that would handle 5KW.

Many thanks for the input.

Keep it comming...

You guys Rock....

I love this Forum....

[scottsAI]

Hello Murlin,

Local Costco has golf cart batteries for $53, 6v at 225aH.

I bought Crown golf cart batteries for $60 at a local store last year. Before Costco.

If you have a golf course around using electric, check if they are willing to sell cheap their old batteries, with a bit of TLC they may give you several years use. Your mileage may vary!

People here claim to buy them for $8 or so. Did not work for me.

How much pumping time or flow do you need? What is the watter for?

I have a friend that collects rain water so he does not need to power the 400 ft pump with the generator.

Have fun,

Scott.

[Murlin]

Hi Scott,

Collecting rain water is going to be something was going to do, but where I live, it doesn't get much rain at all.

Year before last it didn't rain for 8 months, and this year we would have ran out of water too.

The shallow wells are full of iron and other minerals that make the water unsutible for drinking without distilling, so you must go deep and even then with all the drilling for gas, the PH is way up there.

I have heard alot about galf cart batteries mentioned in here, they must be good.

The most important thing for me was how long they will last.

Murlin

[scottsAI]

Hello Murlin,

Its amazing what you can remove from water by bubbling air into it.

Like Iron, hydrogen sulphide, other stuff.

After oxygenated, Iron will settle out if left long enough or can be filtered. Water softeners using salt are cheap to run, last long time to remove the other stuff.

Around here deep wells cost a fortune, friend had to get a new 200 foot, complete with pump cost something like $6-8K. Require big motor need lots of power.

You can buy a lot of water processing equipment for that much money! Lots of help to pick equipment.

Golf cart batteries last longer than the 12v 115ah equivalent. Lots of variation in price.

The way I figure it, $53 gets me 6*225 = 1,350wHr storage. Nothing close.

Other batteries do have a longer life, but then it becomes an investment in protection.

One big screw up can cause serious damage to a battery pack. Does not matter what it cost.

I hear the golf cart can last only 3 yr or longer than 7 years. Mostly depends on how they are taken care of. People are more careful with an expensive battery. If they do the same thing for golf cart, they last long to.

The most important thing for me was how long they will last.

If very remote I can understand that. If not I do not...

By the way it's very easy to distill water if you have the heat. Many cool designs around.

Plastic sheets are cheap, can handle the heat. Very nice use for solar power. Low tech.

Higher tech, use solar for the heat, with Vacuum distillation, Not hard to make nor very costly to build compared to the cost of a well. Biggest problem is the power, with solar, not a problem.

Other techniques, distill water directly from the air. How much water do you need. Have waste water? What is it used for?

I came across a web sight, people used every roof to collect water. Big tank for storage. Including an above ground swimming pool They had a 6-9month dry season, could not afford the well or power. Once they started using the pool, never ran out of water! Used ones are cheap.

Have fun,

Scott.

[Murlin]

Hi Scott,

Good points on the battery bank.  Stuff I hadn't considered.  I guess batteries are like tires for your car.  You can buy good tires that last longer, but it costs alot.  One thing is for sure, they are going to wear out.  So pay a little now, or alot later. An expensive tire will still get punctured by road hazzard...

"How much water do you need. Have waste water? What is it used for?"

Enough for 4 families.  Water used for everything. From household to watering the lawn and garden.

Mabe keep my pond cistern full.

Our yearly average used to be about 40-50 inches a year.

Last couple years it's been, 20ish, less than half.  

Got to have a well man....  A well costs more, but it is alot easier.

Murlin teh lazy

[scottsAI]

Hi Murlin,

When dealing with batteries there are a lot of things to consider beyond their cost.

Solar power systems around here were recommending 11 days of storage.

Max record of cloudy days. This advice doubled the system cost.

Battery discharge depth is a common question.

Plans that limit discharge to 25%, the battery cost will be 2x verses a plan to 50% or 3x 80%.

Many will recommend one of the above. Time effects dominate most considerations with a Lead acid battery; time of discharge, time battery is discharged, time to recharge, etc. Understanding of these effects can help lead you to a good choice that works for you.

These are all valid plans, most importantly consider your objectives and your situation.

Be honest with yourself, write them out. Then research the cost associated with each choice. Rethink your objectives after you discover their real cost. This is how I do things. I will repeat the cycle until I have found the best information I can find for the time I'm willing to put into a choice, make the choice and stick with it. I use emotions for setting goals and logic to achieve them. (I think that's a quote?)

Assuming you have a generator and fuel is readily available even if costly, sizing of the battery to the average need, using the generator for above average need is often lower cost long term.

How do you do this? Use the present cost of each system to compare.

The fuel is an on going cost, make assumptions on how much will be needed, then convert it to a present up front cost. Makes for much easier comparisons of systems, do same for battery...

Remember a deep discharge battery is designed for an 80% discharge, it's made for it. But, the less it's discharged the longer it will last. Yin, yang. Talking to a few golf course technicians using electric carts, the batteries last 1 to 3 years, couple fail in the first year, about half fail during the second year, Most all rest fail in the third year.. If the golf cart application is not the worst for the care of a battery I do not know what is. Well maybe electric trolling motors, lots of people I talk to kill the battery before charging. Then they have to replace every season. Most don't keep charged over winter!

Have fun,

Scott.

[SamoaPower]

You make an excellent point about time effects Scott.

One I would add to your list is the time between discharge and full (not partial) recharge. As I understand it, the sulphate formed during discharge becomes more difficult to remove (or convert) with passing time so, timely recharge is significant to battery life.

My rule of thumb is not to go longer than 48 hours between full charge points. Actually, a small controlled overcharge is given, sort of a mini equalization charge, every cycle. If the primary charge source(s) don't handle it, the back-up is used. This may not be the most energy efficient but I think the trade off in battery life is worthwhile.

With this approach I can get 7-8 years to the 50% capacity point with golf cart batteries.

[scottsAI]

Excellent SamoaPower,

The post was getting long so left out the actual effects of time. You said it very well.

I have not had a golf cart battery for 7 years so could not say I did it! One year so far.

This forum is great, but the information is so scattered, and who do you believe?

Would be nice if the good info was combined in one place.

Lots of miss information on the web.

Something like a wizard to help design, but how to incorporate new ideas?

Have fun,

Scott.