Watermaker Energy Calc's

[cj88]

Originally Posted by Paul L

Do you know anyone who uses one? Sounds interesting and very efficient. Odd marketing when they say both "Non proprietary components" and "Patented Low RPM energy recovery pump".
I don't see a price on their site.

The last price I had was NZD$8400 or just under USD$5500. They have also developed a 120 LPH / 31.7 GPH @ 36A for NZD$10400 or just under USD$6800. No personal experience.

[john61ct]

Originally Posted by Pizzazz

0.9 amps/gallon Large scale desalination plant
1.1 amps/gallon Spectra
2.5 amps/gallon Large DC watermaker
3.0 amps/gallon Small DC watermaker
4.0 amps/gallon Very small DC watermaker (i.e. PowerSurvivor 35)
6.0 amps/gallon Efficient AC watermaker (assuming 100% inverter efficiency)

I assume all those numbers using "amps" are actually "amp hours"?

And also assume a 12V system? Although Ah are the proper unit better than Wh for this purpose, the voltage does need to be explicitly stated.

[john61ct]

And for those using amps ratings, it very unlikely that will just cleanly extrapolate to Ah/hour, and from the gph number to a Ah per gallon figure.

The data needs to actually be measured installed and in use IRL, and do realize that many variables, especially water temperature, will make a huge difference.

[Paul L]

Originally Posted by john61ct

And for those using amps ratings, it very unlikely that will just cleanly extrapolate to Ah/hour, and from the gph number to a Ah per gallon figure.

The data needs to actually be measured installed and in use IRL, and do realize that many variables, especially water temperature, will make a huge difference.

Have you ever used a watermaker on a boat? Huge difference is BS. Sure there are a number of factors, including salinity, but using the basic specs for a reputable watermaker is fine for planning. There's no point in trying to make this complicated.

[john61ct]

Obviously the level of accuracy "needed" for planning is subjective.

My point is, based on some vendor spec like this

Originally Posted by cj88

CJD Watermakers list their 60 LPH / 15.85 US Gallon/hr unit as 16A @ 13.0VDC

There's no way anyone can say this unit will produce in real life, even "approximately" 1 gallon per Ah energy input actually consumed.

If an owner of this unit says it averages, say 1.7 Ah/gal, that's a better source than just doing arithmetic from the above spec, but

again, if their water temperature is very different from yours, your Ah/gal may well be a very different actual number.

Even just the voltage level from one run compared to another can make a big difference.

[Paul L]

Originally Posted by john61ct

Obviously the level of accuracy "needed" for planning is subjective.

My point is, based on some vendor spec like this
There's no way anyone can say this unit will produce in real life, even "approximately" 1 gallon per Ah energy input actually consumed.

If an owner of this unit says it averages, say 1.7 Ah/gal, that's a better source than just doing arithmetic from the above spec, but

again, if their water temperature is very different from yours, your Ah/gal may well be a very different actual number.

Even just the voltage level from one run compared to another can make a big difference.

You didn't answer the question, have you ever used a watermaker on a boat? Yes or no is all that is needed.

CJD are very careful in specing the conditions and they are all pretty standard. Since cruising boats use their watermsker in constantly changing conditions of salinity, temperature, voltage, filter cleanliness their actual output will vary from place to place. Using the standard, published numbers is a just fine approximation and perfectly usable for planning.
No need for adding complexity.

[cj88]

Yes, current draw alone doesn't tell the whole story. CJD do provide other specs to help compare but, of course, it then depends on how other manufacturers measure their units as to whether you can make a direct comparison.

PERFORMANCE

Rated Performance / Product Water Produced: +-15% at 700 PSI / 44.8 bar, 77°F / 25°C & 35,000 PPM TDS typical sea water

PRODUCTION

60 LPH @ 13.0 VDC

CURRENT DRAW
16 amps @ 13.0VDC

SALINITY RANGE

Designed for seawater use up to 50,000 PPM TDS (NaCl) (typical seawater salinity is 35,000 ppm)


TEMPERATURE RANGE

Max. 50 Degrees Celsius, Min. 8 Degrees Celsius

System Feed Water Flow: 1.7 gpm / 6.4 lpm

[Dsanduril]

I agree that the Spectra is still one of the most efficient models on the market. Not the best engineered (they still have too many basic materials science problems). I own and operate one. Live on the water I make using it. Have done for years. Repaired mine (and many others) in remote places.

I have just been disappointed from a specifications perspective. My real world experience, pretty carefully measured, is 18-19Wh/useable gallon (4.75-5Wh/liter). That's about a 30% increase in energy over advertised values.

Just like mileage values for cars, they put their best foot forward. But it's very rare to run with brand new filters, a brand new pump head, and perfect voltage supply. For a company that advertises products to be used going to the remotest parts of the world I'd appreciate some real world advertising - even if the headline has to be the perfect conditions scenario in order to grab eyeballs.

[Paul L]

Dsanduril
The marketing spec that always bugged me is when they advertise the small DC units by hyping the gallons per day produced.

[nfbr]

Originally Posted by Dsanduril

OK, I'll vent my frustration with Spectra a little more fully.

I've never seen any advertising or any literature where Spectra acknowledges this key voltage dependence. Only when you buy a unit and get the factory acceptance test paperwork do you see that nugget. And nowhere in the manual does it talk about the drop in production related to voltage, and especially not an acknowledgement that it is more than the slope of the voltage difference. Spectra's advertising focuses on a value of 13.8Wh/gallon with no reference to required voltage and the increase in energy/unit at a lower voltage.

Then they test with 13.8V at the pump terminals. This is a nearly impossible scenario in the real world, especially on units that claim to be suitable for use straight from the batteries. Even their larger units are small enough that you don't want to have to run a generator/engine for the entire water making period.

Lastly, they do acknowledge, but only in the manual, that actual production will be reduced by the approximate half hour of production that is used to rinse the unit at the end of use. If you run 4 or 5 hours that equates to at least a 10% increase in energy/useable unit. This is a harder one for advertising because I might want to run for two hours and you for 10, but I think it should be acknowledged somewhere other than deep in the manual.

Sorry for the rant, but overall I personally find their advertising practices deceptive, and deliberately so.

Newer models seem to be Brushless DC motors.
Brushless DC controllers will pull constant Power, so less volts, means it should drive more amps, to maintain either RPM or Power (with this load, that's the same thing)

[nfbr]

Originally Posted by Pizzazz

Approx. power consumption, in AHrs. Multiply by 12.4V to get watt hours:

0.9 amps/gallon Large scale desalination plant
1.1 amps/gallon Spectra
2.5 amps/gallon Large DC watermaker
3.0 amps/gallon Small DC watermaker
4.0 amps/gallon Very small DC watermaker (i.e. PowerSurvivor 35)
6.0 amps/gallon Efficient AC watermaker (assuming 100% inverter efficiency)

Source: some estimates, some published materials, some real numbers, some guesses.

AC I'm assuming you mean no energy recovery unit?

[nfbr]

Originally Posted by Pizzazz

Approx. power consumption, in AHrs. Multiply by 12.4V to get watt hours:

0.9 amps/gallon Large scale desalination plant
1.1 amps/gallon Spectra
2.5 amps/gallon Large DC watermaker
3.0 amps/gallon Small DC watermaker
4.0 amps/gallon Very small DC watermaker (i.e. PowerSurvivor 35)
6.0 amps/gallon Efficient AC watermaker (assuming 100% inverter efficiency)

Source: some estimates, some published materials, some real numbers, some guesses.

AC I'm assuming you mean no energy recovery unit?
CruiseRO seems to use the logic that if the generator is running anyway, then the fuel burn difference with / without energy recovery is limited.
That's true, as generators have overheads
Off battery / solar however, it's a whole different situation.