Watts vs Volt-Amps - huh ??

[russ]

Classic Peanuts cartoon. Charlie Brown is at the bus stop complaining that he had a math test that day and he had been up all night worrying and praying over it.
Linus, I believe, said "Charlie Brown, worrying and praying should not be confused with studying."

I saw that one and loved it!

[inetdog]

When someone commented "I wish" or "I am sure" in an engineering discussion an old boss of mine usually to them to crap in one hand and wish in the other - come back and tell us which fills up first.

Many are working on energy storage and have been for many years - when will the break through come? Who knows but it will be done using science and engineering - not feel good hoping.

Classic Peanuts cartoon. Charlie Brown is at the bus stop complaining that he had a math test that day and he had been up all night worrying and praying over it.
Linus, I believe, said "Charlie Brown, worrying and praying should not be confused with studying."

[inetdog]

The funny thing was that he didn't seem to know what I was talking about when I said, " 3, 4, 5".
No need to elaborate on the Pythagorean deal on my part. I just enjoyed the rest of my day.

And my snappy comeback is "5, 12, 13". (Which makes a reasonable choice for roof pitch for many purposes.)
The ancient Egyptians knew very well about small-integer right triangles, even if they did not have the benefit of help from Pythagoras.

[russ]

When someone commented "I wish" or "I am sure" in an engineering discussion an old boss of mine usually to them to crap in one hand and wish in the other - come back and tell us which fills up first.

Many are working on energy storage and have been for many years - when will the break through come? Who knows but it will be done using science and engineering - not feel good hoping.

[Beanyboy57]

Even your great great grand kids will be using fossil fuels so don't worry about them running out any time soon.

If I had my choice of a power generating station close to me I would go with Nuclear. While I would love to have a solar farm providing me power I know that I need something else to give me power through the night. Solar and wind are not going to do that. You will always need some form of base power generating plant and they will probably be some form of fossil fuel burning type. Either that or you will have to turn in early since there won't be any power to run all of your electronic entertainment equipment.

This type of message is a great indication of the old fashioned thinking that is around regarding power usage and storage. I'm not saying it is wrong or right, its just how we think. Before the wheel was invented I am sure the troglodytes were saying there will never be a better way to move around than by foot!
I am sure that the Japanese people that recently suffered from radioactive poisoning and lost their villages, along with the people that suffered from Chernobyl or the Long Island incident would think you are totally crazy having a nuclear power plant in your back yard. Or maybe you do not read the news?
By the way does the wind stop in the night time where you live?
I do believe that in the next 20 years or so we will have much more improved methods of storing power and using power, these developments will be fought by the industries that use fossil fuel to produce electricity and the fossil fuel advocates on this site but I am confident there will be technological breakthroughs that change our ways of life.
Here's to the optimists among us!!
Jon

[SunEagle]

Hi Julie, good luck with your venture into solar energy and off-grid applications. I believe that there is still a long long way to go until the technology develops its full potential but that shouldn't stop people trying it. I have a grid tie and an off-grid setup, both have their pros and cons and both are useful as a learning tool especially for our kids.
History indicates that the more people get into a concept the more developers and researchers will tackle and eventually solve the associated issues.
In the case of off grid, the main issue is energy storage, you can see evidence of that by reading the posts on Lithium battery storage and other types of battery storage. There are many many pages of discussion.

I think we all know that fossil fuels will not be around forever and that they are a major concern for the environment, therefore alternative forms of energy will need to be further developed as well as changes to the way we all 'use' (read waste) our power.
The way I think about it sometimes is like this, if someone said to me that they were going to build a solar/wind farm 20km away from me or a coal fired power station which one would I be more concerned about as far as fouling the air with chemicals? If I had the choice which one would I vote for?
I Look forward to further discussions.
Jon

Even your great great grand kids will be using fossil fuels so don't worry about them running out any time soon.

If I had my choice of a power generating station close to me I would go with Nuclear. While I would love to have a solar farm providing me power I know that I need something else to give me power through the night. Solar and wind are not going to do that. You will always need some form of base power generating plant and they will probably be some form of fossil fuel burning type. Either that or you will have to turn in early since there won't be any power to run all of your electronic entertainment equipment.

[Sunking]

I think we all know that fossil fuels will not be around forever and that they are a major concern for the environment

With that statement you loose any environmental argument immediately.

If fossil fuel runs out like you say, the problem solves itself, there is no problem to solve.

[Beanyboy57]

I am new to solar and very interested in off grid systems.


As my handle states, I am just a hobbyist. I have just purchased a set of cells, and intend to make my own panel as a project with my kids. This panel will be used to charge my travel trailer batteries when we are dry camping. I am, however very interested in off grid power and I'm considering going off grid for my mother in law unit, or just for an emergency back up.
Love the idea!

Hi Julie, good luck with your venture into solar energy and off-grid applications. I believe that there is still a long long way to go until the technology develops its full potential but that shouldn't stop people trying it. I have a grid tie and an off-grid setup, both have their pros and cons and both are useful as a learning tool especially for our kids.
History indicates that the more people get into a concept the more developers and researchers will tackle and eventually solve the associated issues.
In the case of off grid, the main issue is energy storage, you can see evidence of that by reading the posts on Lithium battery storage and other types of battery storage. There are many many pages of discussion.

I think we all know that fossil fuels will not be around forever and that they are a major concern for the environment, therefore alternative forms of energy will need to be further developed as well as changes to the way we all 'use' (read waste) our power.
The way I think about it sometimes is like this, if someone said to me that they were going to build a solar/wind farm 20km away from me or a coal fired power station which one would I be more concerned about as far as fouling the air with chemicals? If I had the choice which one would I vote for?
I Look forward to further discussions.
Jon

[Sunking]

I am, however very interested in off grid power and I'm considering going off grid for my mother in law unit, or just for an emergency back up.
Love the idea!

You may love the idea now, but will hate it once you understand the cost. Anything you take off-grid will cost you 10 times or more for power the rest of your life. Used in a MIL suite hundreds of times more because you are not utilizing the power daily and potential generated energy is wasted. Just think of replacing Thousand$ of dollar$ worth of batteries every few years for something you do not use every day for something the Electric Company would only charge you a $5 bill in 5 years.

[Solarhobby]

Power Factor correction

I am new to solar and very interested in off grid systems.
I could not calculate impedance or power factor without referring to books.
However, an old timer explained it to me this way.
Electrons flowing through a wire create a magnetic field surrounding the wire. When you make hundreds of coils from the same wire (an inductor) and pass current through it the magnetic field produced by the flowing electrons induces an equal but opposite (flowing the other direction) current in the adjacent turns of wire. This inductive reactance (as it is called in an AC circuit) or inductance as it is called in a dc circuit tends to oppose the current being delivered from a power source to the load. In the case of an ac induction motor (most motors being used in the average home are single phase induction motors) this opposing force is referred to as CEMF or counter electromotive force. Large factories and industrial plants tend to have many inductive loads and induction motors, causing the low power factor. This low power factor is why the power companies charge more for the power, because it requires more power to run a load. This is incentive for the factory to do something about it. So what do the factories do about it? If a person were running a synchronous motor, as opposed to an induction motor, there would be no CEMF in the circuit.
At this point it should be noted that in a purely capacitive load (power factor greater than 1), the current leads the voltage instead of lagging, as in the inductive load. So, if a plant or factory has the incentive to do so they can introduce capacitive loads in some manner.
In a oil refinery where I once worked they had a huge compressor motor with a wound rotor (dc voltage could be applied to the rotating element) which could be operated at a leading power factor (current leading the voltage) in order to help correct for the large number of induction motors which were operating at a lagging power factor.
Another place I worked was a hospital in Anguin California which had an emergency generator.
During times when the utility power was out (which happened frequently) they ran their generator. Power was at a premium as you might imagine since it was a hospital.
In this place I noticed they had very large capacitors connected across some very large induction motors connected to the elevators. This, I was told was to help correct power factor for when they were running on their emergency generator power source.

The purpose of my post is to determine the following:

Are any of the veteran off grid solar people taking steps to correct their load(s) by perhaps adding capacitance to their systems? I read all of the 44 posts above but it was not mentioned.
As my handle states, I am just a hobbyist. I have just purchased a set of cells, and intend to make my own panel as a project with my kids. This panel will be used to charge my travel trailer batteries when we are dry camping. I am, however very interested in off grid power and I'm considering going off grid for my mother in law unit, or just for an emergency back up.
Love the idea!

[bkbatts]

Well if you are a Carpenter, I can teach you AC theory in 5 minutes or less.

Any good carpenter knows how to make a perfect Right Triangle with a simple cosine equation. Bet you are not even aware you knew trig. Ready 3 + 4 = 5 Every carpenter knows this is a true statement and is cosine law you can prove to yourself right now with a piece of paper, a ruler, a compass, and a pencil


So now just replace a with Resistance, and b with Reactance, and the result c is the Impedance. Oh the power factor is simple PF = a/c

Also called: The pythagorean theorem. I never thought of using it in AC calculations. Good to know.
Also reminds me of the time when a Capt. in the Army thought he would give me (a lowly E4) a lesson in geometry. As we sat under a tin roof shed doing the latter part of "hurry up and wait" which the Army is so famous for he pointed to the rafters and says, "See this." He was a nice enough guy so I let him go on about measuring the sides in order to get the length of the longer side. The funny thing was that he didn't seem to know what I was talking about when I said, " 3, 4, 5".
No need to elaborate on the Pythagorean deal on my part. I just enjoyed the rest of my day.

[SunEagle]

SunEagle do not get to wrapped up into it. It only becomes a problem when you are pushing the inverter to the limits.

Thanks I won't.

I tested my inverter today on the small 4 cu ft frig we own. It's name plate has it rated at 115 volts, 120 watts and 1.5amp max. It drew about 15 dc amps when the compressor was on so the PF is probably between 65 and 70. Since the inverter is rated 2500 watts I don't see a problem overloading it.

I appreciate your support. By the way you can call me Vince.

[inetdog]

Sort of but not really. Any motor is a reactive circuit because of the windings, and any reactive circuit will have a PF. Any AC to DC power supply is a non linear circuit.

+1. Different types of motors will inherently have different typical power factors, and the PF will often vary with the load on the motor.
When looking at non-linear circuits like CFL ballasts, the ones with better PF do not (just) use better components, they use additional components which reduct the amount of the non-linearity which is seen at the input. In that sense, it is a difference in design, and designing for better PF will usually increase the cost.

[Sunking]

In trying to figure out why some appliances or motors have a poor PF and others do not I have formed the idea that PF is related to the design, construction and quality of the components. Is this a correct assumption?

Sort of but not really. Any motor is a reactive circuit because of the windings, and any reactive circuit will have a PF. Any AC to DC power supply is a non linear circuit.

[Beanyboy57]

You tube videos of off-grid setup

. Much as I would like to tell you some of the real shonky items that never come close to their claimed specs. This holds especially true for many MPPT controllers.Many cant even equal let alone beat a good PWM controller .
Mabe there are some others that will give you some advices as to what to buy.. But it usually comes down to MONEY you buy rubbish 10 times you buy good once.

What would be nice to see is a Youtube or similar video make by someone reputable, qualified and experienced, showing the components, the wiring, the location, the battery bank setup, of an off-grid solar/wind energy system that is in current operation, with the data about the day to day function. Many DIY'ers gain advice from not so reliable sources for their first off grid attempt and make some costly mistakes as you can read for yourself from the postings on this site.
I wish I had seen all the advice that I have gained from this site demonstrated in a ready made system before I ventured into this 'world' and wasted some of my hard earned cash, although I must say that it has certainly been useful to make some mistakes and increase my knowledge base.