Time for solar-pumped water

[Soundguy]

Chatcher... good luck with whatever you do..

With the $$ #'s being quoted here, and some quick math.. I'm having a hard time seeing how any of it is cheape rthan a full standby gen on diesel or propane with an automatic switch.

Sure.. you eventually run out of fuel.. and the sun will shine forever.. but... the upfront startup costs seem to be about 4x over a standby system.. plus the maintenance costs I'm 'guessing' about re: batteries, pump.. etc.. would likely offset fuel storage for -many- years.

One really bad storm and thousands of dollars of solar cells may be toast..... then you'd be SOL..

Still... If you7 are inclined to go for it.. do it. No one ever gets anywhere by not taking chances... Solar technology is a great idea.... as soon as battery technology catches up it will be a good combo.. good for you for being brave enough to stay on the edge... I wish all you off-grid guys well.

soundguy

 

[chatcher]

...The pump will not start if there is not enough current to run it at 500rpm or better...

That's a consideration. I think the batteries will take care of the current needed to start my Grundfos pump, although it does have some internal electronics (maximum power point type circuitry) so that it can be used in a batteryless design. The garden pump will need a current booster for morning startup and I think I found one that will work - a Solar Converters, Inc. PPT 12/24-7V.

...I am surprised at some of the costs given for Solar Power, I currently have a 1,000.00 system that powers my small cabin and expect to spend no more than 15,000.00 on the system for my home...
...I think you will find that it doesn't take that much water pressure to fill a pressure tank...Now that I have the 10,000 gallon tank at 100ft I no longer need the pressure tank...

...A inexpensive low energy pump for your garden can be found at WalMart the Attwood bilge pumps put out good pressure and don't cost more than 30.00 bucks. They are designed for a 12 vold stystem so no inverter or even a battery would be required as long as the sun is shining...

I'm rapidly learning that solar power is not really a replacement for grid power the way we have become accustomed to using grid power. In other words, my home has 200-amp service, electric heat pump with electric auxiliary heat, electric well pump, electric water heater, electric clothes dryer, refrigerator, freezer, and all the other energy hogs so common throughout suburban and rural America. A solar system that would handle all that would be obscene. But along with more sensible home design and energy management, it does allow you to do some pretty amazing things.

I'll check the bilge pump out.

 

[chatcher]

...With the $$ #'s being quoted here, and some quick math.. I'm having a hard time seeing how any of it is cheape rthan a full standby gen on diesel or propane with an automatic switch...

You're right it is more expensive up front, and maybe even over the long term, depending on whether or not the prices of oil and propane continue to rise. And a generator would allow us to pretty much go about our normal electricity usage where solar will be more limited.

But it's clean, quiet, odor-free, and just plain more appealing to me than a generator. I know oil had to be used and pollution had to be generated to produce all these neat solar toys, so I don't pretend it is as beneficial to the planet as some think. Anyway I've committed to at least trying it (with a "Plan B" every step of the way).

 

[denmansoft]

Why not just use a battery instead of a current booster?
Small 12V SLA battery will handle current surges of pump starting.
I've been paying $15 for 12V 7Ah

 

[chatcher]

Why not just use a battery instead of a current booster?
Small 12V SLA battery will handle current surges of pump starting.
I've been paying $15 for 12V 7Ah

The reason for choosing a current booster instead of a battery for the garden system is that the battery would completely discharge when the sun sets, stay drained overnight, and only begin to recharge in the morning after sunrise. Batteries typically don't last very long when treated that way. The current booster will allow the pump to start when the panel voltage comes up each morning, and the pump will run only as long as the panel is producing sufficient power.

My house system is pressurized and the pump shuts off once the tank is full, so the batteries there will hopefully never see a very deep discharge. The panels and batteries for the house will be sized to produce and store enough energy during one sunny winter day for several days of water use, while the panels for the garden will be sized to run the pump only while the summer sun shines (the garden should not need watering during winter or on cloudy/rainy days).

 

[RonMar]

House System:
How far do you have to run wires from Battery bank to pump?

What type and size of battery are you considering and what wattage of panels?

As I am sure you are aware, DC dosn't travel well. Would it perhaps be more cost effective to run a more conventional 240V AC well pump and use an inverter on your battery bank? This would allow you some added flexibility with the installation location of the panel/battery bank.



Garden system:

I am curious about operation. Will it run all the time sun is available?
What happens when the storage tanks you talked about are full? Is there some type of pressure switch/controller involved?

 

[Soundguy]

The ineficience in the inverter would be a furthere kink in the system. At best.. you see 90% efficient inverters.. that's just another 10% energy loss to factor in to an already borderline powerthirsty system that is off the grid. Heavy copepr will offset the power drop.. higher dc transmission voltage will too.. all with a co$t though..

soundguy

 

[RonMar]

That is why I said more cost effective, not more efficient. With the cost of copper these days to feed a current hungry device such as a pump, and with the losses in moveing DC any distance, a 10-15% inverter loss might be on par with the efficiency of his planned DC setup at far less cost in materials. It also opens the door to far less expensive AC pumps that still meet his need to revert to commercial AC or generator.

If you are only paying 1/4-1/10 the cost for the pump, that is more capital available for more solar panels, or higher capacity batteries, or just plain lowers the bottom line cost...

 

[chatcher]

House System:
How far do you have to run wires from Battery bank to pump?

What type and size of battery are you considering and what wattage of panels?

As I am sure you are aware, DC dosn't travel well.

Including the depth of the well, the distance from batteries to pump will be around 45 feet. At about six amps even using 12ga wire I shouldn't lose too much of the 48 volts battery voltage. I'm starting out with 340 watts of panels. The batteries I will be testing with are 12vdc AGM telecom batteries, and I have 8 of them. They cost me nothing (and may not be worth much more than that). Eventually I would probably use 8 6v golf-cart batteries, unless I expand the size of the system to add an inverter (and more panels of course).

Would it perhaps be more cost effective to run a more conventional 240V AC well pump and use an inverter on your battery bank? This would allow you some added flexibility with the installation location of the panel/battery bank.

The ineficience in the inverter would be a furthere kink in the system. At best.. you see 90% efficient inverters.. that's just another 10% energy loss to factor in to an already borderline powerthirsty system that is off the grid. Heavy copepr will offset the power drop.. higher dc transmission voltage will too.. all with a co$t though..

soundguy

As soundguy says the inverter would not be 100% efficient, and typically I would have to parallel two inverters ($$$) to get 240VAC. Plus the typical AC well pump is not very efficient, either. Fortunately my new high-efficiency whiz-bang pump will run on 48VDC or 240VAC or anything else remotely close, and I am counting on AC grid power for backup. Because while having running water when everyone else in the neighborhood doesn't would be very cool, being without it while everyone else has it would be downright embarrassing.

Garden system:

I am curious about operation. Will it run all the time sun is available?
What happens when the storage tanks you talked about are full? Is there some type of pressure switch/controller involved?

I expect it will run any time there is full sun. I haven't decided about a switch. One of the features of the current booster is a pair of switch leads I can use to shut off the pump with a float switch or other device (soil conductivity sensor?). All I would save by shutting it off is some pond water and the extra wear on the pump.

 

[chatcher]

That is why I said more cost effective, not more efficient. With the cost of copper these days to feed a current hungry device such as a pump, and with the losses in moveing DC any distance, a 10-15% inverter loss might be on par with the efficiency of his planned DC setup at far less cost in materials. It also opens the door to far less expensive AC pumps that still meet his need to revert to commercial AC or generator.

If you are only paying 1/4-1/10 the cost for the pump, that is more capital available for more solar panels, or higher capacity batteries, or just plain lowers the bottom line cost...

In my case the distances are not great and the pump is not very current hungry. In fact my current jet pump draws more current at 240VAC than the new helical pump does at 48VDC. For a daylight-only or grid-tied system (without battteries) I can see the cost of the pump vs. the cost of additional panels might push me toward using an AC centrifugal pump and inverters, but the cost of the battery bank needed to run it during dark hours would be the deal breaker. In my house system, I think the batteries are the weakest link.