Energy savings in high temperature Type II anodizing

A. Hi Alaattin.

We would need to know the room temperature & relative humidity, the tank dimensions, any insulation applied to the tank & the whole chiller system, whether you operate 24 hours a day, the rectifier operating amperage & voltage, etc., to do any calculations ...

But I think the short answer is "negligible" if you make no changes in your physical plant, but "significant" if you do.

The reason I say "negligible" is because the energy required to keep a tank at 19-20 °C when you are not operating it is negligible, and all of the heat put into the solution by the rectifiers must be removed either by casual loss to the environment or by your cooling system ... and the amount of casual heat lost to the environment by operating at 28-29 °C is rather negligible as well.

However, if the higher temperature allowed you to switch your cooling system from a chiller to direct operation from an evaporative condenser or a cooling tower, they use far less energy (you only need to pump the water, not to mechanically chill it).

Please look into the possible advantages of higher temperature anodizing as a potential new technology, not as a cost-saver.

On a personal note, my career in metal finishing was interrupted by a stint in the manufacturing technology division of a world famous consulting organization ... and I disliked my time there. One of the reasons was that I was involved in "cost reduction" programs and never saw a single one I considered completely successful; my personal opinion is that as soon as you shift your focus from doing things better to doing things cheaper, you've taken your eye off the ball and the game is lost :-)

Regards,

A. Do not do it. As said above, negligible, because it will take slightly less voltage to get the same amps,. resulting in lower watts, but, the pore will be larger and will not seal and if dyed the dye will bleed.

A. Hi again. I've already expressed my belief that the energy saving will be negligible, Alaattin. But I've been wrong before, so please show us some before-&-after energy logs when you've tried it. Thanks!

Regards,

A. The heat build-up in an anodizing bath is from the amps & volts supplied by the rectifier. In my opinion, you will spend more energy trying to figure out any savings then you will actually get. Both Ted and Bob hit the nail on the head "NEGLIGIBLE". Use your time to look into other areas where savings can be made like "Aluminum Cathodes"

A. Hi Alaattin. I can just barely read your chart and it's very hard on the eyes, so if you can send a larger one or higher resolution one that would be great.

I'm not going to decipher the math, but if 2 volts can be saved with no downside it will indeed save a lot of electricity. That, rather than the operating temperature is where the savings would come from, and that's the claim/assumption which you would want to see evidence for. Good luck.

Regards,

A. Alaattin

Using the supplied data...

Amperage is 81,250 amps per load,
Ampere hours is 35,208 (81,250/26 minutes) per load; savings will be overstated by more than 50%,
@ 1 load per hour, 4,680,000 square meters processed each year; double that if you have 2 hoists,

$/kwh appears to be off by a factor of 10.

A. Hi again. The Watts of power required from the rectifier, which power must also be removed by the chiller, is the product of Amps x Volts. So the hypothesis that seemed worthwhile to me was the claim that the voltage could be reduced by 2 volts due to the higher temperature. Have you done any resistivity/conductivity test -- Haring Cell, or even as simple as measuring how many volts are required to maintain a given current for the two different operating conditions?

If the conductivity of the solution is so much higher that the reduction in necessary voltage is actually 2 volts less, then substantial energy savings sound possible. If the reduction in necessary voltage is not actually significant, but was just a baseless guess, this project strikes me as wasted effort. I think it all hinges on the truth of the claim that the conductivity of the solution is much higher.

Luck & Regards,

A. Hi. If the voltage is actually significantly lower, the power is significantly lower, because Power = Current x Voltage.

The operating temperature really doesn't much affect the power required to cool the bath because the amount of heat lost to the surroundings or gained from the surroundings at 20-30 °C is negligible. What is the average temperature in the shop? -- I'd guess it varies from about 20-30 ° C   :-)

Luck & Regards,

A. You've demonstrated by dozens of postings here over the years that you're both knowledgable and smart, Alaattin, so I'm not sure why we're not on the same wavelength :-)

Nevertheless: the amount of heat you put INTO this 'exothermic' process is measured in Watt-hours, and is simply equal to Volts x Amperes X Hours of anodizing time.
If the temperature of the bath is close enough to room temperature that no significant amount of heat is going into the tank from the room, or leaving the tank and going into the room, then the amount of heat which must be removed by the cooling system is the same as the amount that went in:
Volts x Amperes X Hours of anodizing time.

If you were comparing two solutions which operated at 0 °C and 95 °C there would be a big difference because the 0 °C tank would absorb measurable heat from the room, and the 95 °C tank would lose quite a lot of heat to the room. I am claiming that the amount of heat gained or lost to the room at 20 °C vs. 30 °C is probably negligible.

Luck & Regards,

A. Hi. Yes, if the Volts, the Amperes, and the Hours for both bars were all the same the heat input to the chiller is the same.

Luck & Regards,

A. Hi again. We are apparently having language difficulties because I certainly did not say what you think I said :-)

I said: "If the voltage is actually significantly lower, the power is significantly lower, because Power = Current x Voltage.".

Luck & Regards,

A. Hi. I can't make it clearer, Alaattin: OF COURSE if you formerly required 18 V and you are now able to produce identical anodizing at 16 V and the same Amperage and the same anodizing time, you are saving a lot of energy both on your rectifier and on the heat input which your cooling system must remove from the bath. I keep confirming that I concur with the answer to that question again and again.

... but you seem to keep requiring that I accept the claim that the anodizing is identical, and then to accept that claim as proof that the conductivity must be 18/16 as high at 77 °F as it is at 68 °F. If it is, it is; but please just accept that we agree on the energy saving formula without demanding that I accept that the anodizing is identical and that the solution conductivity is that much higher at 77 °F than 68 °F :-)

Here is a resistivity (conductivity) chart for 15% sulfuric acid at 68 °F and 77°F which shows higher conductivity, but not by that much.

from