How to cut peak power consumption

[jamieson91]

Would I be posting in the right area .. Have a few ideas I want to run by?
I have 7 sites I have been given the task to cut power consumption in both duration and peak ... Have a few ideas but have not used the forum too much ...
please excuse my lack of forum knowledge

I'll be working on both single and three phase units

mostly refrigeration semi hermetic,hermetic and Copeland scroll

[frank]

There are 3 ways to ensure that you are running your plant the most efficient way it can be run.

1 - Make sure the plant is correctly sized for the job
2 - Keep the coils and filters clean
3 - Have the equipment serviced regularly by someone who knows and understands the equipment

To save money after this, you must turn your thermostat or set point up so that the equipment doesn't work so hard or....... switch it off ;)

[jamieson91]

The Service is very two months and every second one is a major service ..
i have been servicing the sites for 5 years and have installed a lot of the systems ...
i want to cut peak power not so much duration .. Whether it be star delta start or vsd ...

obviously we can't raise temps as the food will go off and the beer will go hot ... Big no no
and all systems are ridiculously clean :)

[Rob White]

.

Have you been given any money to do this?

Other than what Frank says the other one option is to ensure
the plant is well insulated and door (where fitted) are closed all
the time to ensure you do not loose heat.

The new way to minimize power consumption is to use liquid amplification.

You run your comps on inverters and control from the back pressure.
You then run the condensers flat out to drive the head pressure down.
That leaves you with low liquid pressure so it is raised in pressure
by the use of liquid pumps.

Big investment and long term paybacks.

Regards

Rob

.

[passandscore]

The use of HFC-422C in retrofitting HCFC-22 systems in supermarkets is being promoted as a way to reduce power consumption.

http://www.achrnews.com/articles/refrigerant-reduces-power-consumption


Article: Head pressure & power consumption
http://www.achrnews.com/articles/btu-buddy-60-high-head-pressure-and-power-consumption

Improving your power factor is always a good way to make things more efficient.
http://www.actel.com/documents/Motor_PowerFactor_WP.pdf

[Doug30293]

.The new way to minimize power consumption is to use liquid amplification.

You run your comps on inverters and control from the back pressure.
You then run the condensers flat out to drive the head pressure down.
That leaves you with low liquid pressure so it is raised in pressure
by the use of liquid pumps.


Because reduced head pressure reduces the heat of compression and the liquid pumps tend to be more efficient at increasing pressure. Am I correct?

[r.bartlett]

edited for myself/

[r.bartlett]

.

Have you been given any money to do this?

Other than what Frank says the other one option is to ensure
the plant is well insulated and door (where fitted) are closed all
the time to ensure you do not loose heat.

The new way to minimize power consumption is to use liquid amplification.

You run your comps on inverters and control from the back pressure.
You then run the condensers flat out to drive the head pressure down.
That leaves you with low liquid pressure so it is raised in pressure
by the use of liquid pumps.

Big investment and long term paybacks.

Regards

Rob

.

Been a very long while but I thought pumps were to do with ensuring liquid to the metering device due to a low pressure differential between the hi and lo side reducing flow rates and causing starvation and not pressure: otherwise if it's pressure it's another compressor??

[Rob White]

Because reduced head pressure reduces the heat of compression and the liquid pumps tend to be more efficient at increasing pressure. Am I correct?

Yes.
Compressors are expensive to run, liquid pumps not quite as much
so the compressors are controlled to achieve back pressure and the
liquid pump ensures there is enough liquid at the correct hydraulic pressure
delivered to the metering devices.


Been a very long while but I thought pumps were to do with ensuring liquid to the metering device due to a low pressure differential between the hi and lo side reducing flow rates and causing starvation and not pressure: otherwise if it's pressure it's another compressor??

Yes mate your correct
I simplified my answer, but the pressure difference over the
valve must be maintained (about 7 -8 bar) to ensure they
operate correctly and although that is not the only reason,
that is the easiest way most understand it.

Regards

Rob

[Peter_1]

Regarding the liquid pumps: running the condensers all the way down continuously will not give you max savings. Running the condenser fans costs also a lot of money.
It's sometimes better to decrease power consumption by switching of a fan and increase a little bit HP.
But why you need to increase you HP again after lowering it first?
You also have EEV's which can run with a minimum DP. Even normal Danfoss TEV's can work with a DP of 4 bar. A DP of less than 4 bar is almost impossible to achieve in our Northern European climate.
You also can't go much lower when using LPA and if you do, energy for the fans will become too high compared to the savings you then make.
We have a rack running in winter on R404a, TE = 3.7 bar and TC = 8,5 bar with normal Danfoss TEV's.

[Segei]

There is certain optimum condensing pressure. At this pressure high side(compressors+condensers) energy use is minimal.

[fridgey]

It is a hard task to save energy on a refrigeration with out spending a fortune, and not many people out there will outlay capital unless it can be recouped in 2-4 years. Most of the things being suggest will definately reduce consumption but it will take too long to pay for them. If the equipment is well maintained, the only way that it can be acheived cheaply is be raising the setpoint. This is exactly what major liqour stores have been doing, they raised there setpoints on cold rooms from 2C to 5C. Not to many people complain but the save a heap on energy costs. The other way is to load shed, this involves CT monitoring and as power consumption reachs a preset limit non critical equipment is turned off to keep consumption down. This is important in Australia because your peak demand determines how much you pay for your power you use.
Hope this helps

[Segei]

It is a hard task to save energy on a refrigeration with out spending a fortune, and not many people out there will outlay capital unless it can be recouped in 2-4 years. Most of the things being suggest will definately reduce consumption but it will take too long to pay for them. If the equipment is well maintained, the only way that it can be acheived cheaply is be raising the setpoint. This is exactly what major liqour stores have been doing, they raised there setpoints on cold rooms from 2C to 5C. Not to many people complain but the save a heap on energy costs. The other way is to load shed, this involves CT monitoring and as power consumption reachs a preset limit non critical equipment is turned off to keep consumption down. This is important in Australia because your peak demand determines how much you pay for your power you use.
Hope this helps
I don't agree. It is not easy. However, if you know how to do that it is not expansive.
One example. Lowering condensing pressure is major energy saving opportunity. Barrier is liquid supply. Solutions: EEV, 2 TEVs, liquid pump. Choose the most cost effective solution.

[fridgey]

I don't agree. It is not easy. However, if you know how to do that it is not expansive.
One example. Lowering condensing pressure is major energy saving opportunity. Barrier is liquid supply. Solutions: EEV, 2 TEVs, liquid pump. Choose the most cost effective solution.

Easy for you to say in Canada;), but you don't have to deal with 40C+ degree ambients in summer even in winter in the north of Australia it rarely drops below 20C. Or a Carbon Tax at $23 per ton, R404A in Australia now cost $120/kg so puting extra refrigerant in a plant than it requires to operate in the name of energy saving is not cost effective.

Pretty much all plants in Australia are now sized to for 40C ambients which regularly occur in summer. You can't drop the condensing pressure at 40C unless the condenser is massively oversized, agian $$$. It is in summer that power consumption for all refrigeration plants peak in demand. Consumers in Australia are charged according to there peak demand. The higher your peak demand the higher tariff you pay.

Sure in winter you can drop condensing pressure but condenser fans are running flat out to do this, so is there really any energy saved? If there is I would love to see the proof. Then if condensing pressure runs to low you can run into TEV Pressure differential issues, as disscused earlier.

[mad fridgie]

For warmer climates load shifting is often a better option, but again this will require the SCT to drop.
On small/medium refrig systems 1C change in SCT equates to a 3.5% change in power. Do the maths.
So a very low ambient low SCT where is efficiency is already running the fan is less viable, than say when it is a high ambient

[Segei]

Easy for you to say in Canada;), but you don't have to deal with 40C+ degree ambients in summer even in winter in the north of Australia it rarely drops below 20C. Or a Carbon Tax at $23 per ton, R404A in Australia now cost $120/kg so puting extra refrigerant in a plant than it requires to operate in the name of energy saving is not cost effective.

Pretty much all plants in Australia are now sized to for 40C ambients which regularly occur in summer. You can't drop the condensing pressure at 40C unless the condenser is massively oversized, agian $$$. It is in summer that power consumption for all refrigeration plants peak in demand. Consumers in Australia are charged according to there peak demand. The higher your peak demand the higher tariff you pay.

Sure in winter you can drop condensing pressure but condenser fans are running flat out to do this, so is there really any energy saved? If there is I would love to see the proof. Then if condensing pressure runs to low you can run into TEV Pressure differential issues, as disscused earlier.
For summer temperature. May be it is time to use evaporative condensers and plant can be designed to 30C.
Checked forecast for Melbourne. Day temperature 22-24C, night temperature 9-11C. A lot of opportunities to lower condensing pressure. Low pressure differential is a barrier, but every barrier has a solution, sometimes several solutions, choose the best one. I gave 3 solutions for low pressure differential. For every outside temperature there is optimum condensing pressure. At this pressure total energy use (compressors+condensers) is minimum. I've done many tests on evaporative condensers and I know optimum. Unfortunately, I don't have information about air condensers.

[assailant]

Checked forecast for Melbourne. Day temperature 22-24C, night temperature 9-11C. A lot of opportunities to lower condensing pressure.

of course you northern hemisphere-ans would be aware we are at the back end of winter down under?