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  #1  
Old 04-17-2016, 05:03 PM
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Default ??Excess Solar Power

I've mentioned this here before: my new well has a head 210ft down, so I need a powered pump. I'm going with solar for security reasons: frequent grid outages in this rural location and what about when TSHTF?

I talked to The Sunshineworks, told Ron Castle (real nice guy) the situation. He asked me my location and well depth and told me "here's what you need."

I just received the hardware which includes a Grundflos helical pump (runs AC or DC) with a capacity to pump up to 6gal/min, and two 255W PV arrays... not using batteries--don't want to mess with maintenance during brutal winters etc.

My question is, if I'm using probably less than 120 gal/day, that can be pumped in about 20-30 minutes, yet the system is generating juice for 4-5 hrs/day, what will it take to capture that extra energy, what can I do with it and is it worth it to bother?
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Old 04-17-2016, 07:37 PM
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You said you did not want batteries so short of hooking up an outlet to run some DC tools directly from the panels not sure there is much you can do with it. But then you have to make sure the panels will produce all the power the tools will use.
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Old 04-17-2016, 11:14 PM
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Let me clarify: I didn't want to be obligated to batteries during the winter for the pump.

The excess charging capacity could go to batteries for storage, maybe to keep a freezer going for a few days during a grid outage? How much could I store and would the added expense of batteries, inverter etc be worth it?
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Old 04-18-2016, 09:10 AM
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I doubt that 510 watts is going to support a fridge or freezer for long. Perhaps an attic fan to help get the heat out of your attic area during the summer..

That would depend on how close the pump/panels are to the house. Some wire and a voltage regulator or a fan that will withstand the highest voltage the panels can deliver. ("On" when the pump is off and "Off" while the pump is working)

There are things to consider, like how the panels are configured and the working voltage..
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Old 04-18-2016, 02:15 PM
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I assume you're using some kind of cistern for water storage with a float switch to turn the pump off when it's full.

It will have to be custom designed but have the float switch control a 3-way switch (transfer switch) that'll divert the power from the pump to a secondary load when the tank is full. The secondary load could be something like a charge controller and battery bank or a resistance heater for heating water.

If you're not using a float switch and just a manual on/off switch then replace it with a 3-way switch and whatever dump load that'll work with the panels power/voltage range.

WWW

Last edited by wywhitewolf; 04-18-2016 at 02:34 PM.
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Old 04-18-2016, 02:44 PM
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Originally Posted by wywhitewolf View Post
I assume you're using some kind of cistern for water storage with a float switch to turn the pump off when it's full.

It will have to be custom designed but have the float switch control a 3-way switch (transfer switch) that'll divert the power from the pump to a secondary load when the tank is full. The secondary load could be something like a charge controller and battery bank or a resistance heater for heating water.

WWW
Good ideas, but what I'm really asking is what's that gunna cost vs what's it gunna save me?

In doing nothing more, I'm wasting solar power already bought. But to capture that energy, I've got to put out more money. Will that saved energy give me any significant energy security? ie- can I run a freezer for a few days on it and save $700 worth of meat? I can live without lites, hot water or TV.

(510 W x 4 hr of sun) - 510 x 0.5 hr pumping = 1.7kW-hr/d to be saved (max)

Freezer uses ? 30W for ? 1 hr/d How many batteries, what type & cost + cost of inverter & ?controls would do the job?
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Old 04-19-2016, 11:40 AM
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There are a lot of other factors to consider. If you use a battery to store energy, there will be a 20% loss from the start. A battery will only return 80% of the total charge..

What voltage are we dealing with? Are the panels close to your house? Will they get unobstructed sunshine all day?
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Old 04-19-2016, 09:34 PM
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Which unit did ya git?

http://realgoods.com/grundfos-sqflex...r-pump-6-sqf-2
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Old 04-20-2016, 11:47 AM
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That's the pump. Panels are 24V.

The solar array is 200 ft from the house, but I could easily put batteries to be charge at the array and transport them to the freezer when needed. The installation is in an open area and will be shaded only by the cloud cover in central WI. (Maybe sunrise is delayed by an hour or so by nearby woods & hill.)
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Old 04-20-2016, 02:35 PM
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I just received the hardware which includes a Grundflos helical pump (runs AC or DC) with a capacity to pump up to 6gal/min, and two 255W PV arrays... not using batteries--don't want to mess with maintenance during brutal winters etc.

My question is, if I'm using probably less than 120 gal/day, that can be pumped in about 20-30 minutes, yet the system is generating juice for 4-5 hrs/day, what will it take to capture that extra energy, what can I do with it and is it worth it to bother?
That's not really how it works. You will NOT be pumping 6 gallons per minute all day long. When you have a stationary solar system that's not tracking the sun, the panels are producing only a fraction of their total capacity.

At dawn, when sunlight first strikes panels oriented south, the panels are only putting out maybe 1-2% of their rated amperage. By 8am, that number goes up to about 20%. Maybe they will produce about 50% their rated output by about 10am. Only right at 12 noon will they produce anything close to their rated output, and don't expect that be be any better than 90%.

It's really being disingenuous to rate any kind of solar pump in gallons per minute. They really should be rated in gallons per day to give meaningful numbers.

BTW, your best option is likely to wire the two panels in series to raise the voltage to the maximum possible that your pump is rated for. That way, losses do to the resistance of the wiring is reduced to a minimum. The controller box for the pump most likely is a MPPT controller which will convert the morning voltage to current that the motor needs to get started in the morning.
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Old 04-20-2016, 03:21 PM
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That's all been figured in--only 4-5 hrs of adequate sun each day--and if we went with battery storage for the pump, we'd get by with less solar capacity. Without the batteries, the pump will work on demand to the limits of the sun at that moment.

But the pressure tank will be no bigger than 120 gal and we will probably use only half that each day-- so no rush to fill it. Even at 50% of its limit, the pump will only be actually in use ~1 hr a day max- meaning we're "wasting" 3-4 hrs of generation a day.

I'm thinking it would be cheaper, easier and more versatile just to have a $400 generator on hand for the freezer when the grid goes down for a day or two. If TSHTF and the grid goes down for a prolonged (or permanent) period, then the battery system may be preferable.
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Old 04-25-2016, 07:48 AM
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Quote:
Originally Posted by doc View Post
But the pressure tank will be no bigger than 120 gal and we will probably use only half that each day-- so no rush to fill it. Even at 50% of its limit, the pump will only be actually in use ~1 hr a day max- meaning we're "wasting" 3-4 hrs of generation a day.
Regardless of your storage medium, if you're not using the energy, you're "losing" it but don't get hung up on over capacity. I think that's one of our Western Culture flaws - we try to accumulate too much.

That being said -- I see one possible deficiency in your plan: You estimate using about 60 gpd and you seem to indicate that you have a 120 gal pressure tank.

Do you have a storage tank as well? Storing water is the same as storing energy. You might consider storing 1,000 gal. or more. That's barely more than a couple of weeks of normal use so more actually is better. I don't believe you would be wasting money. Instead, you're paying for a one time purchase of an insurance policy.

Consider using the well pump to fill the storage tank then add a similar pump to pressurize the pressure tank from the storage tank.

Benefits:
* Water available after extended cloud cover
* Water available if well pump fails
* Water available in case of a well contamination or water table decline.
* Bulk water available for fire fighting, irrigation etc.
* Reduced wear and tear on your well pump since it now only needs to supply a gravity tank instead of a pressure tank.
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  #13  
Old 04-26-2016, 11:20 PM
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I'll be catching rain water off the barn roof (a one inch rainfall amounts to 600 gal!) That will be stored and gravity feed my garden plot- about 100 ft vertical drop below. I also have a couple low flow springs, but they're a qtr mile below the house.
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