LED fixtures not only use less energy, but they also give off less heat than other sources of lighting, making them an ideal choice for freezers, and cold storage facilities. 

When we talk about lighting energy savings in cold storage facilities/ freezers, we are mainly concerned with:

1)      Power Input into Ballast/Driver-  how much wattage the light fixture uses;  

2)      Waste Heat- the amount of waste heat a lighting fixture emits;   

3)      Power Needed to Remove Waste Heat- the amount of energy needed to remove waste heat from the refrigeration system. 

We are going to compare 2 traditionally popular lighting solutions for freezer/cold storage applications with a newer technology; the LED.

Power Input into Ballast

Let’s start with how much wattage each type of fixture uses (on average) 

Based on industry averages, the wattage needed to power the LED fixture is significantly below what a traditional HID fixture consumes. 

If this were the only argument for switching out HID’s in freezers, it would be somewhat compelling, but when we talk about cold storage/ freezer facilities, we also need to think about how much waste heat is put back into the facility.     

The argument for better lighting efficiency in terms of refrigeration heat load savings basically comes from one main source.  Avoid heat leakages into the refrigerated space.  Even with the simple action of touching a light source with your hand, it is easy to feel that it gives off heat.    

In order to get figures for how much energy is converted into radiant heat (including UV and Infrared heat sources) from a lighting fixture, we have taken some information from the GE website: 

• 90% of HID/Halogen lamp system power is heat- the average HID is 450W

= 90% of 455W = 409W wasted heat/ fixture

 

·         79% of Fluorescent lamp system is heat –a six lamp T8 HO fixture is 220W

 =79% of 220W= 173.8W wasted heat/ fixture

 

·         70% of LED systems is heat- a 6 lamp LED T8 tube is 145W 

 =70%*** of 145W= 101.5W wasted heat/ fixture

 

For further reading, please visit the sites via the link below:   http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm#heat_rads 

http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/thermal_mgt_white_leds.pdf 

 

***Based on 2009 IESNA values.  Due to advances in LED technology, it is very probable that LED systems are more energy efficient in 2011 and give off less heat than they did in 2009. 

 

 

The graph for this looks as follows: 

 The heat released from a lighting fixture in a freezer needs additional energy for the heat to be removed.  This additional energy is mainly used by refrigerator heat pumps and the additional background equipment needed to make them work (water pumps, extra heat exchangers, oil pumps, etc.)  The common power ratio to calculate this is 3.4122 BTU/ hr divided by the EER rating.

What is an EER (Energy Efficiency Ratio) rating? 

A typical office HVAC is EER rated to 10.5.  Very efficient systems can hit 13.5.  However, typical industrial refrigeration is far less than this at about 7.0 due to all secondary fans, pumps, water towers, electrical panels needed to dump the heat.  This value of 7.0 is what BC Hydro uses to model lighting vs. freezers for its own incentive calculations.  We will be using the 7.0 EER rating in our calculations. 

For more information on EER ratings, please visit: 

http://www.mcquayup.com/FAQ/FAQ-McQuay.htm#GeneralQ2    

Power Needed to Remove Heat

3.4122 BTU/ Hour

7.0 (EER Rating)

Calculations: 

Part A:  Total  Energy Load (Input + HEAT WASTE ) per fixture

LOAD= (INPUT POWER) + [(HEAT WASTE) x (ENERGY NEEDED TO REMOVE HEAT)] 

LOAD = (INPUT POWER) + [(% WASTE X ORIGINAL WATTAGE)x(3.4122 btu/hr)]

                                                                                                                        (   7.0 EER   ) 

 

1)  HID LOAD= 455W + [( (90% X 455W)   X    ( 3.4122) )]

                                                                                  (7.0) 

     HID LOAD = 455w + (409W X 0.4874571)                                                                   

     HID LOAD= 654 W Total Effective Loading/ Fixture

 

2)  Fluorescent T8 6 Lamp LOAD= 220W + (79% X 220W)  X  (3.4122)

                                                                                                          (7.0)

     FLUOR.  LOAD= 304 W Total Effective Loading/ Fixture

 

3)  LED 6 lamp LOAD= 145W +  [(70% X 145W)      X   (3.4122)]

                                                                                              ( 7.0)

     LED LOAD= 194 W Total Effective Loading/ Fixture

 

For more information on how we arrived at the calculations, please refer to: 

http://www.engineeringtoolbox.com/cop-eer-d_409.html 

 

The Graph for this looks as follows: 

 

 

To understand the significance of this, it is best to put a dollar value to it in terms of total operating costs per fixture.  Because HID’s cannot be sensored, we have the lighting fixtures operating 24/7. 

 

Part B:  Yearly Operating Cost/ Fixture

 ***calculations are using $0.10/kWh and 8760 hours in temperatures of +5C for refrigerators and -15C for freezers

 

1)      HID= 654W (Total Load) x 8760 (Hours/Year) x $0.10/kWh=  $573***

2)      FLUOR = 304W (Total Load) x 8760 (Hours/ Year) x $0.10/ kWh= $266***

3)      LED= 194W (Total Load) x 8760 (Hours/ Year) x $0.10/ kWh= $169***

 

 

***The above total energy cost chart reflects the dollars needed to run a single fixture (when taking into account wattage needed for light, and any additional energy needed to remove radiant heat) in a refrigerated space. 

 

A total energy audit (input + energy needed to remove heat) for changing out 1 HID fixtures to 1 LED fixtures would produce the following chart.  However, in most cases, it would be best to also sensor the LED’s, so additional savings on the LED’s could also be realized. 

 

 

Total Savings/ year for 10 fixtures= $4,029.60

Total Savings/ year for 50 fixtures= $20,148.00

Total Savings/ year for 100 fixtures= $40,296.00

 

 

 

So, why would you use LED rather than fluorescent?

 

It’s true that fluorescent technology is cheaper to install and not that more expensive to run based on kWh.  However, for freezer applications, fluorescents just do not cut it.

 

“Cold temperatures present a challenge for fluorescent lamps. At low temperatures,

higher voltage is required to start fluorescent lamps, and luminous flux is decreased. A non-amalgam CFL, for example, will drop to 50% of full light output at 0°C. …  In contrast, LED performance inherently increases as operating temperatures drop. This makes LEDs a natural fit for grocery store refrigerated and freezer cases, cold storage facilities, and outdoor applications. In fact, DOE testing of an LED refrigerated case light measured 5% higher efficacy at -5°C, compared to operation at 25°C.” 

 

http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/led_advantage.pdf 

 

This, in a nutshell means that a LED fixture will be 5% brighter in -5 degree Celsius than it is in 25 degrees above zero. 

 

Other features unique to the LED include: 

 

•                     Directional light emission – directing light where it is needed.

•                     Size advantage – can be very compact and low-profile.

•                     Breakage resistance – no breakable glass or filaments.

•                     Cold temperature operation – performance improves in the cold.

•                     Instant on – require no “warm up” time.

•                     Rapid cycling capability – lifetime not affected by frequent switching.

•                     Controllability – compatible with electronic controls to change light

  levels and color characteristics.

•           No IR or UV emissions - LEDs intended for lighting do not emit

            infrared or ultraviolet radiation.

 

Above information taken from: 

(http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/led_advantage.pdf )   

 

 

Right now, LED’s provide the best lighting level/ energy efficient return for cold storage and or freezer units.  The worst case scenario that can come out of retrofitting your freezer lighting is winding up with an air conditioning system that is oversized compared to the reduced heat load.  However air conditioning units cycle off when they are not needed, so the reduced heat load is just a bonus cheque in power savings, as you just simply wouldn’t pay to remove heat that you never wanted in the first place. 

 

 

 

 

 

 

 

Further Suggested Information: 

 

Chocolate Dude Melting Bunny:  A Video

http://www.youtube.com/watch?feature=player_embedded&v=rAcc1WBbE1M#at=81 

     

Comparing White LED’s to Conventional Light Sources

http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/comparing_white_leds.pdf