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Anonymous
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# Posted: 6 Dec 2012 07:14
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So please bare with my very limited understanding of all things power related.
How does this work in the real world. I buy my power from the a hydro company. So they have a damn, they have turbines, they make power and don't store it in batteries. So assuming that they always have enough power for all customers (which they must or would probably go out of business) its fair to assume they are always over producing, that way when I suddenly turn on my lights they don't say "oh no someones drawing more power and we can't accomidate it"
With that assumption in mind what do they do with the excess power?
what about on a smaller, home front? lets say you had access to hydro and tidal power. what if you could generate (on a completely off grid system) 50kw or power a day (so 2kw per hour). Assume you have multiple other sources of power (trickle from solar/wind) and have a 10kwh generator set to come on when your batteries get to 60%.
Say you figure for using 20kw per day. So you have a fairly large battery bank for your "just incase 3 days worth of power"
So 1) once the batteries are full/your current power consumption is used. what happens to the extra power? I mean things like hydro, solar, tidal can't just be shut off. So what happens with the extra power? where can you divert it?
2) is there a way to have power going to the home when the battery banks are say 98% full? so you start using power and instead of using power from the batteries you're using it directly from the solar/hydro/wind etcetc and only when you use more then you are currently generating (say at night with no solar, no wind, the stream is dry whatever) then you start using the batteries?
assume all of this is a completely remote system, no grid tie what so ever.
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neb
Member
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# Posted: 6 Dec 2012 08:41
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PC can't store power. Basically it is there and it is gone and perpetual thing when making energy. When the lights go out they are out.
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Anonymous
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# Posted: 6 Dec 2012 08:54
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so in addition to my first 2 questions
add a 3rd.
3) so where does the power go thats not stored? my solar panel/water wheel/tidal gen/gas gen (whatever) is producing 200watts right now and there is 0 use, and the batteries are at 100% full. where does that 200watts go? i mean it can't just disappear. it has to go somewhere right?
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Anonymous
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# Posted: 6 Dec 2012 08:58
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oh and how does it get to wherever it goes in question 3
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MtnDon
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# Posted: 6 Dec 2012 10:34 - Edited by: MtnDon
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Quoting: Anonymous so where does the power go thats not stored?
This may not be a precisely accurate depiction, but think of it more like the power you did not use, because the lights were left off, was never actually produced. It never left the generator because it had no place to go.
With a gasoline engine driven generator the engine runs spinning the generator at 3600 RPM. If no electricity is being used for anything the engine throttle is only open a small amount. The engine governor maintains the speed. When some lights or a heater is turned on the generator is harder to turn and the throttle opens up. The engine works harder, uses more gas and the generator puts out more electricity.
Same thing happens at the power company. A steam driven generator uses more steam. A water driven generator will use more water.
When no electricity, or lower amounts of electricity are used there is also energy lost to heat via friction.
PV systems are maybe easier to understand. When light falls on a photovoltaic cell there is potential electricity available. If the wires are not connected to anything, no electricity is actually produced or used. Connect something and power then is used. That something could be used so you have to be careful with panels connected in series.
A wind generator is also different. The rotor can overlod and destroy itself if the wind is blowing and there is nothing to use the power for. The charge controller then has to dump electrical power. Home systems usually use an electric heater of some sort. Same problem can happen with hydro. It is possible to build wind generators that have self feathering blades that limit the power outout. Small home systems do noy usually have those.
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Dc4tazz
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# Posted: 6 Dec 2012 11:18
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Energy from the sources you are describing are only being produced when it is being used, when you turn the grid switch to your batteries off, there's no more power being produced.
On the other hand if your grid is producing more than you are using, there are 2. options for you to consider 1. Tie into the power company's grid and sell them your excess 2. At your neighbor's expense, if he's not to far away, put a power line to his house and sell him your excess energy, of course he would have to have a battery bank set up to receive it.
What do you think about these options?
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groingo
Member
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# Posted: 6 Dec 2012 11:28
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We had just that happen this past spring when there was more power than demand, so, the power companies began shutting down generators, in our case they shut down their brand new wind farm.
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toyota_mdt_tech
Member
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# Posted: 6 Dec 2012 13:10
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AC can not be stored unless its coverted to DC, then back to AC via solid state circuits (expensive) but AC is desireable because it can use transdformers to step them up or down. Higher voltages can use smaller sized wires.
The load doesnt vary much, ie each lamp etc. Most loads are winter and during the days when business are at peak, night time being the smallest. Its adjusted at the hydro plant, probablty via water diverted to the pennstocks or stored during dryer seasons. Yes, I assume the capability to make more is always there in case someone needs more, but the overall consumption is figured pretty close.
AC was chosen because its ability to work with transformers without the need for switching circuits to turn the primary side on and off. Its done each time the polarity is changed from negative to positive, then induces voltage across the windings from primary to secondary as the primary voltage collapses.
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TomChum
Member
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# Posted: 6 Dec 2012 18:44
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Think of it like a compressor (a very simplistic compressor, with no regulator and no friction). When the air pressure in the tank equals the air pressure coming out of the pump, what happens? The flow slows to a stop. No flow = no work = no energy gained or lost.
The pressure is there, (potential energy).
Or think of it like pushing a car up a hill, but it got a little steeper and you can't go any higher, so it's stopped,. The energy is currently in balance.
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neb
Member
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# Posted: 6 Dec 2012 19:17 - Edited by: neb
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Great explanations above. One example is your own body when you work hard you use energy if you don't work then the energy is there waiting till you need it. If you don't use it you lose it and can't store it up till you are 95 years old.LOL
Over producing or under producing is related to power factor. That is another topic, PC & Generation watch loads very closely and is a big deal. Producing to much causes a lot of problems.
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Anonymous
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# Posted: 6 Dec 2012 22:27
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Thanks for the info. See if I understand things correctly and can address a few things.
Quoting: Dc4tazz 2. options for you to consider 1. Tie into the power company's grid and sell them your excess 2. At your neighbor's expense, if he's not to far away, put a power line to his house and sell him your excess energy, of course he would have to have a battery bank set up to receive it.
If grid power isn't an option and there are no neighbors. So excess power is just that, excess with no where to go.
MtnDon, if I understand this correctly, in my case (personal home use) a gas generator will self regulate between idle and full throttle depending on use.
So for solar if they are connected to fill a battery bank. If the bank is full, and the sun is out, and you are drawing nothing that power has to go somewhere.... and this is where a charge controller comes in? It may be connected to a heater? basically use the excess power to heat an empty room or the great out doors? This is basically just a power sink so that you don't burn things out.
I assume this is the same for wind and hydro. As you said the not likely for the blades to be adjustable in a small, maybe even homemade system. I guess a fair assumption is that tidal power would be the same???
So if your system was large (in my origianl post) making 50kw a day and using only 20kw a day..... thats a 30kw excess. That seems like a fairly large amount to try and "burn" off with use of a heater.
Most systems I see for wind/micro hydro/tidal don't have an automatic disconnect. so they run 24-7 (like they are supposed to) and could be dmged from that power having no where to go. Solar your cells are okay if they are sitting in the sun, connected to your own little grid (house and batteries) and you are consuming 0 power. So they just sit and sort of make potentially make power but dont actually produce?
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MtnDon
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# Posted: 7 Dec 2012 00:43
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Quoting: Anonymous a gas generator will self regulate between idle and full throttle depending on use.
Only if it is an inverter generator will the engine speed change. A std gen runs at 3600 rpm's, but the actual amount the throttle is open will vary with load.
Folks who have wind systems will almost always have a charge controller that has a dump or diversion load. Otherwise they risk equipment damage as well as possible battery damage.
PV systems must use a charge controller to reduce the charge to the battery in order to prevent cooking the battery. It does not require a diversion load as PV panels themselves are not damaged if the sun shines on them and the output is restricted.
IMO, unless the PV array is quite large there will not be much useful "extra" power after the batteries are charged for the day. I had entertained the thought of using excess power in cool / cold weather to keep a food locker in the cabin from freezing when the cabin was vacant and unheated. It didn't calculate out well enough to warrant the bother and the equipment expense, IMO. As a safety dump for wind that's another matter.
If heating is a goal much better can be made of the sun by using the sun to heat directly and skip the making electricity part.
Quoting: Anonymous I guess a fair assumption is that tidal power would be the same???
Pretty much all generation other than PV would have the same need to dump or divert excess power at times. Pretty much everything else uses a generator head to produce the electricity.
Is there some desired goal, or did this start from a curiosity about is there was a real excess made by power companies and how/what they did???
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Anonymous
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# Posted: 7 Dec 2012 06:28
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It began with a desire to (former post from me under anon) http://www.small-cabin.com/forum/3_2745_0.html#msg39547 Live a city life style (creature comforts that require power) while being in a remote off grid location that can't be reached or serviced by... well pretty much anyone.
It makes a large impact in which property I want to purchase. I live in canada and am looking for northern coast properties that aren't reached from the highway or logging roads. This means transport in is by boat, plane, or helicopter. I don't have a helicopter so that means by boat or plane (float plane).
Apart from all the other fun ideas figuring out how to get machinery and vehicles to such a site comes the need for some basics (as well as luxuries)
In my continuing search for whats possible, and what I can over come with some inventiveness and a lot of forward thinkers showing me things that I never knew. People like yourself MtnDon. helpful, well informed and willing to share your knowledge with the inexperienced and ignorant people like myself that need help before (and I'm sure during) their build.
At anyrate I found an interesting tidal "generator" It's not an actual generator but it does spin wheels pretty fast. If a wheel can spin then it can be geared up, and can generate power. I believe the mini model mock up (on a lake) in 3 inch waves was estimated to produce 50watts an hr. Nothing large but 3inch waves on a lake are tiny, and the model was also quite small.
So there are some nice properties in these remote locations, the best of which have year round flowing rivers, small lakes, and are ocean front. In my world that sounds perfect. Ocean, river, and lake. No shortage of water, and lots of options for power. I did figure the environmentalist might have issues with me putting up a water wheel, or even a floating wheel in the river (or hanging from a bridge or even just a pole (think a swing set. one A frame each side and hanging from the pole, a floating wheel).
Anyways I decided that all of these would be required especially in the long cold winters where solar would have nearly 0 impact. I'm not sure how much power I could draw from a river or stream, many calculations and that becomes a specific question from property to property. However I started thinking more about tidal power. So many of the projects looked like major under takings, things that a guy couldn't just build on his own. Or they looked ... like toys.
But this one seemed so simple. infact the only thing that isn't shown is what happens when the tide changes a little to much (to high or to low). So I looked at it scaling it up, gearing it up, started to think what a person could do. started to wonder if power was free, simple, renewable, always there, always producing you could live 3-4kw per hr. I'm by no means advocating to do that or that I would do that or have an interest in doing that. But then I started to think, what about other things that are needed in such a remote location. Welding machines, drill presses, heaters, perhaps a green house for a garden during the winter (requiring both light and heat) as well as water pumps, a sewage system.
At some point before everything was running there would be a lot of power generation. While being away from the cabin especially there would be a lot of power. During certain times of the day even, or seasons. So the question became what happens when you can generate so much power, and so much excess power. Because of the areas that I want to live, selling to neighbors (or even giving to them for free.) or selling to the grid isn't an option.
So that excess power basically falls down to... what can be done with it? if it wouldn't hurt the system it wouldn't matter. But from what is being said it could and most likely would. So my curiousity was peaked, what would the power company do? what could I do? what options are there?
and everyone has been incredibly helpful and I'm very thankful for the ideas and advice. Every time I post here I get a little closer to my dream. One day at a time, one problem solved at a time.
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