Solar/submersible pump for pond waterfall - how to plan capacity

[coling]

Hi,

As a complete newbie to solar pumps, I would like to be able to confidently plan the size and capacity of the submersible pump and solar panel I will need for my pond/waterfall.

My initial measurements are:
- pond size - 5ft x 6ft x 18"
- there is already a slope next to the pond - where I will build the waterfall
- the height of the waterfall source above the pond - 6ft
- length of the waterfall - 18ft

My initial questions are:
- how many gallons per hour should I design for?
- what wattage spec should I look for for the submersible pump? It has to lift the water 6ft.
- what size solar panel will I need?
- what recommendations do you have for manufacturers of pumps/solar panels?
- should I consider the pump and solar panel separately, or buy a kit?
- what questions have I not thought of here?

I look forward to your suggestions.

Thanks

Colin Goldberg

[BB.]

Coling,

Do you need off-grid battery powered solar, or just want to experiment / not dig a trench for a 100' of 120/240 VAC buried cable to the pond?

In general, off-grid solar power is quite expensive... On the order of $1-$2+ per kWhr--compared to $0.10-$0.20 per kWH for most people in the US.

Because solar is so expensive, we recommend conservation and high efficiency to reduce the power needs.

Also, there is a big cost to add a battery bank (charge controller, battery bank, replacement battery bank every 3-8 years or so, more solar panels because of battery/charge controller losses, etc.). Add a generator for backup power (especially during the winter) and you have even more costs (and noise/fumes/fuel storage issues, etc.).

If you need to pump water when the sun is not out--you will need batteries and/or AC Mains power. If you only need to pump when the sun is up (and not behind clouds)--your system will be almost 75% cheaper per kWHr over time.

Now to the pumping requirements... Last time I looked, I Googled for fish type, pond type (combined with hydroponics/etc.). Then we looked at what pumps and power system would efficiently fulfill those needs.

In the end, any mechanical system that moves weight (mechanical, air, water, etc.)--Tends to be pretty power hungry--And makes for a pretty expensive pure off-grid solar/battery system.

If your location supports Grid Tied solar (solar panels connected to a Grid Tied inverter tied to your home wiring to an electric utility)--that is usually the best bang for your buck. Very reliable (no batteries to maintain and replace) and can be (especially with rebates and credits) pretty cost competitive with utility power (for example; in California--if you have A/C and/or heavy pumping costs--GT can actually be cheaper than utility power).

-Bill

[coling]

Thanks, Bill, for the info on the solar options.

I do not want to make this an expensive proposition. So I think I will be happy with solar panels without battery assistance and no connection to our grid - ie. no pumping when the sun is not out.

So I am still in need of some idea of the capacity of the pump and hence the solar panel(s). Any suggestions out there? Any links to step-by-step calculations that will allow me to size these reasonably?

Thanks.

Colin Goldberg

[BB.]

Our host NAWS has lots of pumps--but most are for handling drinking water (clean, reliable, higher pressures, not cheap)...

I wonder if you can get an XXX watt solar panel + Linear Current Booster + sump pump (lift a few feet of water--above 9', no flow at all--bottom of page or another brand here) to provide a reasonably priced system (sump pumps may last 1 season--but they are 1/20th the price too).

Many of the pumps have tables of pressure vs water flow (GPM/GPH). There are centrifugal pumps and positive displacement pumps... I would guess you would want a centrifugal pump (positive displacement pumps are usually more efficient but require piston/diagram kits ever few years for household pumping use).

There are AC based motors and DC based... (and AC motors with in inverter built in)... DC Motors have brushes and tend to wear out brushes (and eventually commutators) pretty quickly in continuous service (need brushes every few months?).

You also need to decide between submersible pumps (pump under surface of water--can have problems with leaks in housings), submerged input (input of pump needs to be under water level--cannot draw water to pump--should be installed in pit/down slope), or ones that can lift water above surface of pond. Pumps that can "draw/suck" tend to be less efficient.

Are you going to filter / bio-filter the water? Do you need to inject air (with water pump or separate air pump)? etc...

To circulate water--One number I saw was 1 change per hour (700 Gallon Pond, 700 GPH). For a fountain, perhaps 250 GPH. For a water fall ~700 GPH), etc...

Those are some of the reasons why you may end up paying $30 for a pump / kit or $600...

-Bill

A 500 GPH sump pump with a couple feet of head may only need 30-40 watts of solar panels... A "positive displacement pump" with 20-60 feet of lift may require 300+ watts of solar panels.

[mike90045]

Harbor Freight has a solar fountain pump, but I don't think it's anywhere the size you want. It's a good fit for a goldfish bowl, but it's <$100

For advise, you need to describe the waterfall, hight above pool, if you want a trickle or a torrent.

Moving water is costly, and higher you want, and more volume, will cost you.