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?