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"A top-down approach is essentially breaking down a system to gain insight into its compositional sub-systems.

In a top-down approach an overview of the system is first formulated, specifying but not detailing any first-level subsystems.

Each subsystem is then refined in yet greater detail, sometimes in many additional subsystem levels, until the entire specification is reduced to base elements.

A top-down model is often specified with the assistance of "black boxes" that make it easier to manipulate. However, black boxes may fail to elucidate elementary mechanisms or be detailed enough to realistically validate the model."

So, your black boxes would be each of the wire segments, each transformer, fault protection, and any other "systems" necessary.

I know the temptation is strong to already start buying parts.

One constraint: the transformers may not be stable when feeding the long lengths of wire in the configuration you want. You should ask the manu; they may have application notes that exactly address your plan.

Once you're down to the detailed schematic and parts list, you'll think of more system level stuff, and so on, back and forth.
HUH???

Does ANYONE understand this gibberish?

Yozit, not everyone understands, nor wants to understand, your engineer mumbo jumbo. Why not try to talk (write) like a real person once in a while. :whistling2:
 

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Discussion Starter #22
HUH???

Does ANYONE understand this gibberish?

Yozit, not everyone understands, nor wants to understand, your engineer mumbo jumbo. Why not try to talk (write) like a real person once in a while. :whistling2:

I don't. I am just trying to take a wire 1400' in a rain forest and turn some lights on on the other end, not fly to the moon. Heck, I can use a hand blender in the kitchen. Just lights will be fine.
 

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Mr. Swami, I've cut and pasted all your posts into a single document, and I have some questions on your statements before I put any more work into this.

Here is one scenario, the topmost level of this system design. Correct me if I'm wrong in the statements below and adjust the scenario to suit. Neglect losses for now. If there is anything below that you don't understand, ask.

Your turbine generates 500w continuously and you need 2500w in the buildings.

This means that 100% x 500/2500 = 20% of the time in the buildings you can consume 2500w.
The other 80% of the time the 500w turbine is charging the batteries and you have no power in the buildings.

If the general requirements above are not met, this system is not feasible. The specific numbers can be tweaked but the basic calculations must be adhered to.

Knowing only what is written above, one conclusion you can already draw is that the battery/invertor should be right outside the buildings, since the heavy power is transmitted from the batteries to the buildings. The really long wires should be carrying the charging power since it's only 20% of the total power that we are sending over this network.

Plugging in some numbers, 20% of 24 hrs is ~5 hrs for the discharge time and ~19 hrs is the charge time.

The battery needs to supply 2500w for 5 hrs which gives a battery capacity of 12,500 watt hours. At 48v, this is 260 amp-hours.


Questions:
What is the capacity of your batteries?

What is the recommended charge/discharge rates for your battery?

During the 19 hrs, what minimum power can you live with, if not zero? 100w to power a bulb?

Is there some other charge/discharge cycle besides 24 hrs that we could/should use? The battery manufacturer's recommendations will determine the minimum charge/discharge cycle and how deep the discharge is, for reasonable battery life.

If this is all still feasible, I need to find a way to post a spreadsheet.
 

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Discussion Starter #25
Mr.
Questions:
What is the capacity of your batteries?

What is the recommended charge/discharge rates for your battery?

During the 19 hrs, what minimum power can you live with, if not zero? 100w to power a bulb?

Is there some other charge/discharge cycle besides 24 hrs that we could/should use? The battery manufacturer's recommendations will determine the minimum charge/discharge cycle and how deep the discharge is, for reasonable battery life.

If this is all still feasible, I need to find a way to post a spreadsheet.

Here is the battery info. Deep cycle 6 volt L 16H. Six of them. With DOC at 20% they will last for 6 years

http://www.plymouthbatterycentre.co...nd_marine_battery/l16h_6v_deep_cycle_battery/

The light bulbs are only 20 watt compact florecents.

Need the fridge going full time at 110 watts, but it actually goes off and on itself as need be. So it actually does not use 110 watts all the time.

Lights will be used for a maximum of three hours in the morning and three at night. Although each cabin has two lights in the main room, one in the bathroom, and one outside most of the time it will be the two inside lights on.

Thanks!
 

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Here is the battery info. Deep cycle 6 volt L 16H. Six of them. With DOC at 20% they will last for 6 years

http://www.plymouthbatterycentre.co...nd_marine_battery/l16h_6v_deep_cycle_battery/

The light bulbs are only 20 watt compact florecents.

Need the fridge going full time at 110 watts, but it actually goes off and on itself as need be. So it actually does not use 110 watts all the time.

Lights will be used for a maximum of three hours in the morning and three at night. Although each cabin has two lights in the main room, one in the bathroom, and one outside most of the time it will be the two inside lights on.

Thanks!
Thanks. I have to think about this some more.

But, it turns out there is a level of design more abstract than the one I wrote. It's this:

A system of turbine, cable, battery, invertor delivers power.
The turbine delivers 500w averaged over 24hrs.
A battery can be charged for 16 hours and you only get 10 hours of service, so the battery efficiency is 100% x 10/16 = ~63%, which means 100-63 = 37% is lost.
Let's say all the other components total 10% loss.
Total loss ~ 50%
This leaves you with 250w averaged over 24 hrs at the building.

Is this still feasible?

If not, you need more turbines or you need to intercept the 60w per square foot that sunlight provides. At 10% efficiency, a photovoltaic array delivering 2500w needs ~420 square feet, about 20' on a side.

Windpower I can't comment on, but in Massachusetts they use a 100' boom to mount the blades, generator, gearing, disk brake and whatnot.
 

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Discussion Starter #27 (Edited)
Thanks. I have to think about this some more.

But, it turns out there is a level of design more abstract than the one I wrote. It's this:

A system of turbine, cable, battery, invertor delivers power.
The turbine delivers 500w averaged over 24hrs.
A battery can be charged for 16 hours and you only get 10 hours of service, so the battery efficiency is 100% x 10/16 = ~63%, which means 100-63 = 37% is lost.
Let's say all the other components total 10% loss.
Total loss ~ 50%
This leaves you with 250w averaged over 24 hrs at the building.

Is this still feasible?
I think so, but during the rainy season I could generate twice the power from the turbine. Whereas at the end of the dry season I will need solar panels to augment the system. These same panels could then increase the potential power that much more during the rainy season.

Much more helpful. Thanks!
 

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The batteries are the weak link so you might look into Flywheel Energy Storage. Don't know the cost of these state-of-the-art things but over a long time they might pay for themselves.

I can't write nearly as well as I thought I could. . .glad I could finally help.

:huh:
 

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Please excuse the type font and size ; I'm still having computer problems.

Component Specifications
So the battery is 36v nominal volts at 420 a-h capacity, right?
I need links to get specs on your invertor and turbine/gen arrangement.

Loads
What is each load,
how often is it used,
how many of them are there?
I'm trying to get an idea of the steady state load, the total energy used over 24 hours, and any peak loads (compressors, motors).

I will assume that the fridge pulls, on startup, 5x the normal (steady-state) current, and that it's on half the time. The fridge people might be able to tell you the expected duty cycle of the fridge based on the ambient room temp, but I'm not sure we have to worry about that yet, or at all.

Cabling
Copper wire at 100C has 1.3x the resistance at 20C because of the temperature coefficient of resistance of copper.
Cabling temp rise will be due to ambient temp plus the heating effect of carrying current.
So, what is the highest amb temp you reasonably expect to see? Ampacity and the particular wire insulation is another issue, TBD.

You mentioned a 10% voltage drop on cables; depending on the circuit, if we go to a 5% drop we can cut the cable loss to 1/2 of what it is at the 10% drop, but the wire will cost more. And it may not matter much because of the battery inefficiency swamping out all other losses.

Configuration
Based on my reasoning in a previous post, do you now want to put the invertor at the end of the 2400' cable from the turbine, or is this non-negotiable?

In fact, in general please indicate "design goals" and "minimum values" you can live with. Any extra power during the rainy season is fine.

You've got one kitchen, 6 cabins, cable lengths of 1000', 1400', 700' and 500'.
Please post a scale drawing of how this looks from above.
I think you want the cabin wiring to radiate out from the kitchen in a star configuration (rather than daisy chaining each cabin downstream of the one before).

Post photos of everything; electricians can pick up safety issues that I would not see.

Economics
Since you're not paying for kwh, and aside from not designing a system that abuses the daylights out of the generator, batteries and invertor, are there any economic payback issues that we should consider?

Misc
I assume you have access to a spreadsheet?

There is another way to store power. You pump water uphill to a holding pond and then let the water down through a turbine during periods of peak demand. I don't know the efficiency of this method, and it may only pay off for huge installations.
 

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Discussion Starter #30 (Edited)
]I need links to get specs on your invertor and turbine/gen arrangement.[/SIZE]


Here is the turbine. It's the Stream Engine with two nozzles.

http://www.microhydropower.com/

Here is the info on the inverter, It's the 3600W VFX 3648 48V

http://store.altenergystore.com/Inv...tts/Outback-VFX-3648-48V-3600W-Inverter/p929/

I think we could also discharge the batteries down to 50% and still get plenty of life out of them. Actually it's a 48V system. So 8 6V batteries

I will get you more info later. We are beginning a two day retreat today that will end Sunday evening. So I will get back to this after that.

I really appreciate the help. :thumbup:
 

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finally did a spreadsheet

It's 6 AM, so I can't guarantee these numbers, but, for a max of 5% voltage drop:

From turbine, going 1000' to invertor, ~#2 AWG. Using #8 will starve the battery charger circuitry and you won't get anywhere near the battery performance you should be getting.
The DC voltage into the invertor is probably below the spec value for this device. I hope it has not been damaged.

From invertor and going 1400' to load, ~#0 AWG.

At this point, I can't see cable heating [due to the current passing through it] as a problem.

Since you're not paying PoCo for kwh, I don't think there is a payback period for the money you spend on this equipment.

You've already bought the batteries so I'd put the next few dollars into the 1000' cable. The first priority is not abusing the equipment.

Or, we put the invertor/batteries next to the turbine and figure out how to ship 2500w over 2400'. Step-up/step-down transformers are starting to look good.

If you can supply me some prices for copper and aluminum cables, we can trade off the money you will spend for the performance you will get, and show this as dollars per watt or dollars per watt-hour.

You're a paying customer, so see if the turbine people will give you whatever technical data, schematics, application notes, everything on the generator that is driven by the turbine.
I'm especially interested in whether it is a DC gen or an AC gen with rectifiers.
And the voltage vs. current curve(s) for this gen would be good.

:)
 
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