What would I have to have

[edkemper]

What would I have to have to solar power a 1/2 horse power AC or DC (8 amp) water transfer pump? Either running it 24/7 or just during the sunny times of a day?

[rreidnauer]

Not sure where you are referencing 8 amps from. A 1/2hp pump draws about 1000 watts. To run just when it's sunny is pretty easy to figure. You need 1000 watts of solar, plus efficiency losses. (so figure something like 1200watts)

Now, calculating what you need for 24/7 is a much more difficult task. You need enough solar to recharge a bank of batteries with a capacity to operate the pump through the non-charging hours. The simple view is, the pump is 1000 watts (1 kW) for 24hrs equals 24 kWh of power per day. To provide that kind of power in, say 5 hours of good charging sun, would require 4800 watts of solar panels. And that isn't figuring for efficiency losses. And what if it isn't a sunny day? How many non-sunny days would you want to figure for?

I didn't go into battery bank size you'd need because it is a large variable depending on your requirements.

[edkemper]

Rod,

Thank you. First off, 4 in the morning?

I'll have to ask a few more questions of my neighbor. He was asking about a solar run pump to move water around. He has 4 lakes. So I guess I need quite a bit more info before we can figure out logistics and costs.

Thank you my friend.

(The 8 amp figure came off a data sheet on a 1/2 horse motor I looked up)

[rreidnauer]

4AM PDT. Bit later than that on the little ocean side. ;-)

[SDP]

Actually, a 1/2 hp pump draws 373 watts. A horsepower is 746 watts, no more and no less. Even if it surges to twice its rating on startup, that's only a 746-watt surge, then it settles down to a constant 373 watts. That means that a 100-watt panel will run it for an hour and a half a day, roughly. A pump that size should put out about 140 gallons per hour; how much water do you need in a day?

[rreidnauer]

In the world of neat and tidy numbers, that would be true, but the reality is, it will not be the case. All different ways "calculate a rating", and typically it will be one that is most favorable looking to the product being sold.

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