Lighting Load in Commercial/Industrial Freezers

[aaronnk]

I am trying to calculate the refrigeration energy savings from lighting upgrades in large commercial frozen storage freezers operating at -10F with ammonia cooling systems.

I am thinking that the refrigeration savings could be calculated in terms of reduction in compressor load as follows:

Refrigeration Savings = (Lighting Wattage Reduction*Lighting Heat Load Factor)/(COP*compressor efficiency)

where Lighting Heat Load Factor = 0.9

I have the following questions:

1. Is this the right way to calculate the refrigeration energy savings from a lighting reduction?
2. What are the typical COPs found in these type of ammonia refrigeration systems?
3. What are the typical compressor efficiencies found?
4. How would these numbers change at different operating temperatures?

Thank You

[sterl]

1) No. Compare existing KW times Heat Factor (which is really reistive component of emittance) with Kilowatt times Heat Factor for retrofit.
2) 1.95 to 2.05 at design conditions: 2.2 to 2.4 at Reduced Head / selective fan cycling and so on....

30 Adiabatic Effeiceincies for 2-stage in mid-70's; volumetirc efficeincy in the low 90's. Single stage economized a little lower and suffers at low load on a single compressor....
3) Higher Suction=Better COP. Lower Discharge= Bettwer COP. Typically: at these conditions, 1-psi gain in suction worth bout the same as 3.5 PSI reduction in discharge....

[lowtempman]

I agree with Sterl's comments and would add that if you are planning to "upgrade" to flouresecent which is probably not the case, [ better eff lighting exists], that you include the energy that goes into ballast, [ sometimes overlooked].

Lighting eff will not produce dramatic changes in KWH usage in my experience. What will, is to turn off lights when you don't need them.

Greatest heat gain in a storage freezer is often infiltration thru doors.

[aaronnk]

Thanks for all the info.

I am looking at replacing 465 W Metal Halide lights with 160 Watt High Bay LED's with integral motion sensors and a wireless control system.

Case studies have been showing a reduction in lighting power in the freezers by 90%.

I am trying to work up estimates of the refrigeration energy savings from such a drastic lighting load reduction.

Is there a good way to estimate refrigeration maintenance savings, as there would be a significant load reduction on the compressors?

Is anyone interested in more information about this type of lighting upgrade?

[pkr]

Lighting load forms only a very small portion of the refrigeration load. It is advisable to switch them off whenever the doors are closed. It is a different matter if the upgrade is to improve the Lux value.

[ref717]

Lighting load is insignificant in large cold storage rms. as what some of our friends said. Better to turn-off your lights during long weekends or holidays.
In Industrial refrigeration, you can gain significant power savings thru proper operation and maintenance of all your key equipments.
Example for Aircoolers you must study the correct defrost time and sequence because too much defrost will put more load on your compressors. Regular Aircooler valve station maintenance is also important. Properly operating Auto-purgers are also a plus in energy savings in condenser operation.
There's much more, and I leave to some of our experts here in Industrial refrigeration. More info guys!:)

[Segei]

You save save twice when the light switched off. First is light energy. This energy create parasitic refrigeration load and additional energy of refrigeration plant should be spend to remove this load. Typically, for freezer cold storage 2 KW of light off save 1 KW of refrigeration plant energy. Switch the light off and save 4% of total power and additional 2% will be saved in refrigeration plant. Total is 6%. This is during summer operation. During winter operation load can be 50% or lower compare to summer. Switching light off will save 12% of winter energy use.

[sterl]

History from Working for a Big End User:

The thinking is correct but doesn't speak the right language....And rules of thumb are handy but don't carry much analytical weight either.

Cold storage operations that don't actively cool product should "think" occupation, revenue, maintenance and costs on a per cubic foot basis....

So: You have 10^5 cubic meters of storage. You have 10^7 kg of products in there....thats 100 kg/m^3. Occupation.

Work your lighting to Watts per m^3; then extend it over the year. Work your refrigeration load to Watts per m^3 per year; work your refrigeration investment and your lighting investment to $/m^3. Then you can talk to accountants and free up $ and make sales....COP's they are never going to understand.

Note that this opens the avenue for anticipated investment deferred; or deferred investment precluded...They love that stuff. All the business schools and management consultants have different names for it and the $ folks embrace it like a shipwreck victim hangs on to a life preserver....

What it means is: You invest in good lighting now and your refrig load goes down...But you already own the refrig equipment. So reduce your load 5-times, at 3% each, and you will not have to purchase new refrigeration equipment when the time comes to grow by 10 or 12%. You just use up some of what you created in capacity margin; by reducing refrig loads. This works especially well once the peak oeprating temperature starts to rise a degree or 2 because operations have intensified, lengthened or otherwise; or roofs and walls have decayed. Because expanding a refrigeration system by 5% to accomdoate those things is a tough thing for you, and the $ folks to rationalize....but upgraded lighting is highly visible and by comparison, much easier than renewing a roof.