WHAT IS THE DIGI-RTU The Digi-RTU is a Heating, Ventilation, and Air Conditioning (HVAC) rooftop unit control kit that is both a demand management and energy usage device. It is designed to improve the energy efficiency and demand requirements of a rooftop unit as well as solve the humidity, common noise, and frequent on/off issues of a rooftop unit through modulating the capacity of a rooftop unit to match the cooling or heating space requirements.
DIGI-RTU PERFORMANCE RECOGNITION American Public Power Association s 2011 DEED Energy Innovator Award.
DIGI-RTU ADDRESS ALL PNNL 1 FOUR AREAS OF ROOFTOP UNITS ADVANCED CONTROLS - Integrates air-side economizers - Controls supply fan speed - Controls compressor capacity - Manages Demand-Controlled Ventilation, CO2 - Demand Response signal enabled - Fault Detection via existing BAS, IP thermostat or utilizing Digi-SFT Addresses ALL Four PNNL Recommendations for Advanced Controls of Rooftop Units 1 Department of Energy's Pacific Northwest National Laboratory http://www.pnnl.gov/main/publications/external/technical_reports/pnnl-20955.pdf
HOW THE DIGI-RTU WORKS By intercepting heating and cooling calls, the Digi-RTU s patented technology manages the compressor and fan speeds to match the space requirements. As a result space temperature and humidity are best managed. DIGI-RTU KIT
MAIN APPLICATIONS Package rooftop units, water and air source heat-pumps, split units HVAC rooftop units between 3 to 30-ton Up to four cooling stages Up to two heating stages Scroll & reciprocating compressors Existing space thermostat and BMS
DIGI-RTU ADVANCED CONTROLS FUNCTION Modulating mechanical HVAC equipment to better match space operating requirements is the accepted industry standard Modulating fan and compressor is the energy efficiency strategy for all climate zones Cool and hot/dry climates increased free cooling Cool and wet climates humidity and moisture control Economizer Integration Integration and management of the existing economizer Extends existing economizer range by 30% Fan Speed Control ON mode - average fan savings are greater than 85% AUTO mode - average fan savings are 70 80%
DIGI-RTU ADVANCED CONTROLS FUNCTION Demand Controlled Ventilation, CO2 CO 2 sensor into the return air duct integrated with the economizer satisfies ASHRAE 62.1 and CA Title 24 air quality requirements Fault Detection Digi-SFT provides fault detection diagnostics and notification or Digi-RTU communicates with the existing BAS or IP enabled t- stat for diagnostics and notification Demand Response The Digi-RTU is subordinate to the existing T-stat or BAS system responding to all space /building cooling and heating requirements The load-limit factor for the rooftop unit is sent through the BAS to the Digi-RTU, and can range from 50-100%
DIGI-RTU ADVANCED CONTROLS FUNCTION Existing Building EE Strategies, Platform & Equipment Communicates with existing BAS platforms and existing installed thermostats; programmable, IP etc. Integrates with the original equipment HVAC controller Mounts inside the HVAC rooftop unit Compressor Optimization Conforms to original equipment manufacturer recommendations for speed reduction down to 45Hz Programmed logic provides soft start & stop of the compressor Extended compressor life and lowered lifecycle costs Compressor modulation savings are double fan power savings for a significant portion of the United States climate zones Peak Demand savings of 4 5kW for an average 10-ton rooftop
BENEFITS OF USING A DIGI-RTU OPTIMIZER For Utility Companies: Lowers peak demand up to 65% Reduces kwh usage up to 65% Decreases carbon emissions Scalable, 3-hour install time For Building Owners and Tenants: Reduces electricity consumption and costs Better maintains space humidity and temperature which decreases comfort complaints Reduces compressor on/off cycling up to 75%, and reduces maintenance cost Reduces HVAC equipment noise in occupied space
OMAHA, NE
DIGI-RTU CASE STUDY PHARMACEUTICAL DISTRIBUTION CENTER 100 100 90 80 80 60 60 50 40 40 20 30 20 0 10 0 9/18-20 10/18 11/17 12/17 1/16 2/15 3/17 4/16 5/16 OAT (F) Power (kw) 70 70% kw decrease Pre - blue Post - red Ambient temperature 5-minute intervals Date Without Digi-RTU With Digi-RTU OAT Measured Power Consumption and Ambient Temperature 4640 South 59th Street Omaha, NE 68117
Power (kw) DIGI-RTU CASE STUDY PHARMACEUTICAL DISTRIBUTION CENTER 100 90 80 70 60 50 40 30 20 10 0 30 40 50 60 70 80 90 OAT Without Digi-RTU With Digi-RTU 85% kwh decrease Pre blue Post red 5-minute intervals Comparison of Measured Power Consumption with and without Digi-RTU
SAN DIEGO
DIGI-RTU CASE STUDY OFFICE SPACE February - March 2014 43% kw decrease Pre blue line Post green line Ambient temperature red line Measured RTU Power for One Minute Interval
DIGI-RTU CASE STUDY OFFICE SPACE February - March 2014 71% kwh decrease Pre blue line Post green line Daily Electrical Energy Consumption; Pre (blue ) and Post (red ) vs. Ambient Temperature
SAN ANTONIO TX
8/27 8/28 8/29 8/30 8/31 9/1 9/2 9/3 9/4 9/5 9/6 9/7 9/8 9/9 9/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23 9/24 9/25 9/26 9/27 9/28 9/29 9/30 10/1 10/2 10/3 10/4 10/5 10/6 10/7 kw OAT, Deg F SEPTEMBER OCTOBER 2012 BIG BOX RETAIL 8 7 6 5 4 3 2 1 0 100 90 80 70 60 50 40 30 20 10 0 Before After AVG-OAT Two weeks with and two weeks without 29.5% kw decrease
kwh DIGI-RTU INSTALL ASHRAE #2 BIG BOX RETAIL 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Two days with and two days without 74% kwh reduction 9/23/12 (OAT = 78 F; weekend; after install) 9/26/12 (OAT = 80 F; weekday; after install) 9/9/12 (OAT =79 F; weenkend; before install) 9/11/12 (OAT = 79 F; weekday; before install)
VERMONT
kwh Avg. OAT BURLINGTON ELECTRIC STUDY Office Building 100 80 Without Optimizer With Optimizer 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 0 Metered Savings = 65% W/O Digi-RTU With Digi-RTU 60 40 20 0 4-Aug 9-Aug 14-Aug 19-Aug 24-Aug 29-Aug 3-Sep 8-Sep Date 65% kwh reduction - Equipment sub-metered - Two weeks pre - Two weeks post - IPMVP
kwh 20-Sep 22-Sep 24-Sep 26-Sep 28-Sep 30-Sep 2-Oct 4-Oct 6-Oct 8-Oct 10-Oct 12-Oct 14-Oct 16-Oct 18-Oct Avg. OAT EFFICIENCY VERMONT - STUDY Distribution Center 70,000 Metered Savings = 68% 80 70 60 50 40 30 20 10 0 Without Optimizer With Optimizer 60,000 50,000 40,000 30,000 20,000 10,000 W/O Digi-RTU With Digi-RTU 68% kwh reduction - Equipment sub-metered - Two weeks pre - Two weeks post - IPMVP 0
DIGI-RTU CONCLUSIONS Digi-RTU is able to: Reduce peak demand up to 65% Reduce consumption up to 65% Improve room humidity management Improve room temperature management Reduce compressor cycling Reduce maintenance costs Reduce equipment noise
Bes-Tech, Inc. 4640 S 59 th Street Omaha, NE 68117 402.502.2340 BES-TECH.NET