VFD’s to Optimize System Savings

Keith Kempski

Control Techniques

• View VFD as the tip of the

iceberg

• Integration with the E2 provides

optimal savings

• Typical supermarket applications

are reviewed

• State utility rebates are

compared

• Energy savings presented

Supermarket Energy End Use

VFD Supermarket Applications

Air Handling

Compressors

Condensers

•AHU’s

•RTU’s

•Condensers

•Compressors

•Pumps

•Exh. Fans

RTUs

AHU Control Basic

• Fan motor savings

• 15 Diagnostic

parameters

• Modbus communication

to BMS

HSK

AHU High Value Integrated System

• Fan Speed Control

• Broken Belt Detection

• Energy Meter

• Space Temperature

• Economizer

• Heat/Cool Staging

• Compressor Staging

• Power Monitoring

Air Handler

HSK E2

AHU High Value Integrated System

• Autotune – easy set up

• Fan Speed Control

• Broken Belt Detection

• Local Alarm

• Remote Alarm

• Occurs within short

time period

• Maintains Comfort

• Energy Meter

• kWh reading

• $/kWh input

• Running Cost

• E2 Communication

• Benchmarking of

store performance

Air Handler

HSK

AHU High Value Integrated System

Air Handler

• Optimization tips

• 1 or 2 Hz motor speed

change can reduce

energy by 14%

• Savings vary by

location

• Use Energy Meter to

trend energy

HSK

AHU High Value Integrated System

• Complete Space

Temperature and

Humidity Control

• Economizer

• 6 types

• Heat/Cool Staging

• Multiple stages

• Fan speed control

• Compressor Control

• Copeland Digital

Scroll

• HSK variable speed

• Power Monitoring

• Reduce demand

and cost

• HSK reduce motor

speed and power

Air Handler

Air-Cooled Condenser Control

HSK control • Full modulation • Temperature Differential • Power Monitor

• Demand Control • Same as AHU

Air-Cooled Condensers

VFD control • Full modulation • Temperature Differential • Power Monitor – Demand Control

Air-Cooled Condensers

VFD control • Full modulation

• Pressure Transducer or Temperature Sensor

• Variable speed fan control – all fans controlled

• Variable speed/constant speed – first stage variable speed. Other stages start/stop

Air-Cooled Condensers

VFD control continued • Temperature Differential

• Pressure transducer or temperature sensor • Ambient air vs. refrigerant temperature • Control for specific refrigerant • VFD control of first stage heat rejection • Constant speed fans activated for additional

cooling

Exhaust Fans

• Compressor rooms or warehouses

• Remove waste heat

• Room thermostat starts exhaust fan

• VFD varies fan motor speed to reduce

energy use

• Optimum control

– Start fan at minimum speed

– Increase speed in increments

– A motor running at 30 Hz uses 12.5% of the energy as running at 60 Hz

• Simple retrofit

Secondary Systems

Primary system

(R-404A)

Secondary System

(Glycol)

Secondary Pumping Systems

• Low GWP

• Reduces amount of refrigerant in

system up to 90%

• Reduces cost of refrigerant

replacement

• Heat exchanger transfers heat from

secondary to primary system

• Glycol is typical secondary

refrigerant

• Advantage – simple, easy to maintain

Secondary Pumping Systems

• Pumps circulate glycol

mixture to display cases

and coolers

• Case solenoid valves

open/close changing

system pressure

• Vary motor speed to

maintain constant

secondary loop pressure

differential

• VFD’s eliminate need to

use balancing valves

• VFD’s save energy and

improves efficiency

CO2 Booster System • Low GWP

• Reduces or eliminates refrigerant

• Successful in colder climates

• Booster System has been

controlled successfully by

Emerson

• E2 and HSK drives used in

system

CO2 Booster System

Low Temperature

Medium Temperature

CO2 Booster System

• E2 Controller

– Synchronized MT and LT compressor control

– Gas Cooler fan control

– Communicates wit HP case controllers

– Remote monitoring and control of system

• HSK Drive

– MT compressor control

• 20 to 70 Hz modulation

• Energy savings proportional to speed (50% speed reduction = 50% energy savings

– Gas Cooler – same control as air-cooled condenser

Utility Energy Rebates (Incentives) • Purpose of Rebate – State Level

– Conserved energy is less costly than new power plants

– Rebates determined by “avoided cost”

• Type of Rebates

– $/HP (typically $30/HP to $100/HP plus)

– % installed cost of project (50% to 100%)

– Combination ($50/HP or 70% project cost)

• Rebate Amounts

– $30/HP to $1,000/HP (that get your attention?)

– Northeast highest rebates

– Other states vary and vary within states

– Texas and California offer rebates for demand (kW) reduction

Utility Rebates Available • National Website to Find Energy Rebates

State: New York

Incentive Type: Utility Rebate Program

Eligible Efficiency Technologies:

Lighting, Chillers , Heat pumps, Central Air conditioners, Compressed air, Energy Mgmt. Systems/Building Controls, Motors, Motor VFDs, Comprehensive Measures/Whole Building, Custom/Others pending approval, Vending Machine Controls, Commercial Cooking Equipment

Applicable Sectors: Commercial, Industrial, Nonprofit, Schools, Institutional

Amount: Determined on a case-by-case basis

Maximum Incentive: Prescriptive: $100,000 per project annually, $300,000 per customer annually Retrofit: $200,000 per building annually, $600,000 per customer annually Custom: $200,000 per building annually, $600,000 per customer annually Whole Building: $400,000 per building annually ($500,000 for LEED-certified), $800,000 per customer annually Commissioning Incentive: 75% of Commercial Efficiency Incentive, 50% of commissioning cost, $50,000 maximum Custom and Whole Building Additional Incentive: technical assistance up to $10,000; more complex projects can receive up to 50% of any additional costs.

Utility Energy Rebates (Incentives) Retail Solutions Makes it easy to find rebates

State Utility Program

Rebate Amount Web Link

• Some states require preapproval or a site audit.

– Preapproval – limited utility funding. Do early in the fiscal year

– Utility sets aside funds for your incentive

– Site audit usually done by utility rep

• Retail Solutions will help you by doing all the paperwork

• You choose

– Receive the rebate directly

– Have rebate sent to Retail Solutions (saves processing)

• For rebate sent to Retail Solutions

– Retail Solutions shows the rebate deducted from your bill

– Payment usually takes 6 to 8 weeks

Utility Energy Rebates (Incentives)

Supermarket Customer Validates HVAC And Condenser Payback

Store / Unit

Before

Annual

kWh

After

Annual

kWh

Savings*

Annual

kWh

Measured

Percent

Savings

% of

Total

Store

Total

Store

Savings

Savings

Annual

VFD

Cost

Simple

Payback

Yrs

1561 Davis Cond B MT 120,196 83,709 36,488 30% 4.6% 1.4% $4,379

1502 Pleasanton Cond A LT 112,694 62,148 50,546 45% 3.6% 1.6% $6,066

Condenser Totals 87,034 38% 8.3% 3.1% $10,444 15000+ 1.5

1561 Davis AHU 125,268 33,966 91,302 73% 4.7% 3.4% $10,956

1502 Pleasanton AHU 125,268 45,535 79,733 64% 5.2% 3.3% $9,568

AHU Averages 85,517 68% 3.4% $10,262 5000+ 0.5

VFD Energy Savings Summary

*Based on monitored kWh and outdoor temperature readings applied to annual Bin temperature hours.

Condenser

AHU Main

0

2,000

4,000

6,000

8,000

10,000

12,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Savings Over TimekWh/Month

68%

Savings

Cold Storage 400hp Compressor Application

• 1 x 400hp ammonia compressor.

• Changed from soft starter (ON/OFF

control) to VFD control.

• Reduced energy consumption by 14%.

• Payback period - 1 year 1 month

• Improved temperature control.

• Operating flexibility with varying loads.

• Less starting and stopping.

26

Grocery Store – Exhaust Fans

27

• 4,500+ x 7.5 HP drives on exhaust fans. • Changed from fixed speed to variable speed control. • VSD total cost - approx $1,560,000. • Energy savings - $832,000 per year • Payback period - 1 year, 10 months. • Increased equipment life and better diagnostics. • Reduced maintenance cost,

reduced noise & vibration. • $832k on the bottom line

every year after payback!

Where To Use VFDs

Application Savings Complexity

HVAC •Supply and Return Air Fans

•Exhaust Fans Excellent Easy

Condensers •Air-Cooled

•Evaporators

•Cooling Towers

Very

Good Easy

Compressors •Refrigeration

•Heat Pump Fair Difficult

Pumps •Secondary (Glycol)

•Heating and Cooling

•Cooling Tower Water

Good Mild

Getting Started – Emerson Retail Solutions • Survey Equipment

– Identify Physical Installation Constraints, Criteria

– Identify Existing BMS Interface

– Evaluate Power Quality For Filtering/Line Reactor Requirements

• Install Sub-metering To Establish Baseline Energy Consumption

• Engineer Controls Strategy – Stages Of Heating/Cooling/Heat Reclaim

– BMS/Life Safety Integration

• Install Demonstration Site – Validate Installation Procedures

– Provide On-Site Training For Service Provider

• Analyze Energy Consumption Post Installation

• Create Business Case For Enterprise Deployment

Thank You

Questions?