REFRIGERATED WAREHOUSES AND DEMAND RESPONSEPRESENTED BY DOUG SCOTTVACOM TECHNOLOGIES

2012 EMERGING TECHNOLOGIES SUMMITPASADENA, CALIFORNIAOCTOBER 15, 2012

REFRIGERATION + DRFUNDAMENTAL ATTRACTIONLarge year round loadLarge thermal mass – perfect!

What stores the cooling?

Building? Air?Product?

COMPLEX FACILITIES, LOADS AND APPLICATIONS

Long Term Frozen Food Storage

Produce Processing

Post Harvest Fruit and Produce CoolingFluid Milk and

Dairy Products

Batch Blast Freezing

Wide Temperature Range: -20°F -10°F 0°F 30°F 45°F

Custom/Built-up RefrigerationPackaged Refrigeration

PerishableMeat, Deli, Produce

Distribution-20 F Ice Cream Storage

Wine Storage

Winery Tanks

RWH tied to Processing LoadsAmmonia Refrigeration / Risk Management

Beverage Distribution

SUITABILITY FOR DR

Long Term Frozen WarehouseBeer and Wine WarehousesGeneral Food Distribution Batch Blast FreezersPerishable Fruit and Produce Production Areas

High

Low

USING EXCESS CAPACITY ---Nature of refrigeration design: large safety factorExample: 140 kSF freezer in Southern California:Capacity: 500 TonsAverage Summer load: 190 TonsPeak Summer load: 240 TonsOperation at 50% or less typical for central plantsStudy on large warehouse with multiple split systems ~40% run time on typical summer day

But, in the future with better design?

COMMON FOR MANY YEARS:VIEW FROM THE 80’S

Daily peak reduction – off 6 hours run 18 hours

Shift on Summer peak days or year round

WEEKLY CYCLE(can’t keep up each day)

Daily peak reduction – off 6 hours run 18 hours

footnote: Numbers from memory to show the concept ..

TEMPERATURES(lessons learned)

• Learned from energy efficiency work: temperatures can be set higher IF temperatures are evenly maintained and monitoredExample, large San Jose freezer:-10 F original setpoint increased to 0 F

1.5% efficiency per degree gain, plus load reduction

= 20% energy savings

• BUT: no longer demand responsive without precooling which takes more than a day

TEMPERATURES(Air flow, circulation, hot spots)

TEMPERATURES(Air flow, circulation, hot spots)

TEMPERATURES(Air flow, circulation, hot spots)

One hot spot = big problem

Need better understanding of product temperature change vs. air temperature

Add more temperature sensors

Use variable speed/variable capacity

BROADER VIEW OF POSSIBLE TIME PERIODS STRATEGIESWide range in response capability with different facilities and system technologies:• Weekly or multi-day cycle – “BTU bank”• Daily response period – precool or catch up• Short duration deferral – 1-2 hours• Minute-by-minute variable load response using

variable speed capability

Greater participation with shorter durations

CAUTION: ENERGY EFFICIENCY VS. TIME OF USE CONTROL

24 hour operation at maximum system

efficiency

18 Hours on6 Hours off

Fans run at reduced speed, following load.

Fans run at full speed to catch up with load.

Compressors run with lower lift by using heat exchangers

all the time with closer approach temperatures

Compressors run at lower suction and higher head to get same heat through heat

exchangers in less time.Result: 25% higher total kWh with 18 hour operation

PRIORITIES –NOT EXACTLY THE SAME

Loads that can be counted on in advance Loads that can be controlled quickly for unexpected needsCustomer satisfaction

Utilities and Grid Owner

Lowest costs• Utilities • Maintenance Manage riskProduct qualityReliable power supply

OWNER’S GOAL:LOWEST LIFE CYCLE COST

Energy efficiencyRates

Demand responsePlant investment (Title 24 ..)

Operations

(minimize confusion)

GOING FORWARDHigh untapped potentialStudy and change practice on temperature and airflow (the basics)Integrate and balance efficiency & DRIncrease flexibility around time durationsImprove automatic control and technology

• On-off > variable• Forward strategies