Catalyst RTU Controller Study Report

Transcription

1 Catalyst RTU Controller Study Report Sacramento Municipal Utility District December 15, 2014 Prepared by: Daniel J. Chapmand, ADM and Bruce Baccei, SMUD Project # ET13SMUD1037 The information in this report is provided by SMUD as a service to our customers. SMUD does not endorse products or manufacturers. Mention of any particular product or manufacturer in this report should not be construed as an implied endorsement.

2 TABLE OF CONTENTS 1. Executive Summary Project Description Results Conclusion Appendix...15 About the Customer Advanced Technologies Program SMUD s Customer Advanced Technologies (C.A.T.) program works with customers to encourage the use and evaluation of new or underutilized technologies. The program provides funding for customers in exchange for monitoring rights. Completed demonstration projects include lighting technologies, light emitting diodes (LEDs), indirect/direct evaporative cooling, non-chemical water treatment systems, daylighting and a variety of other technologies. For more program information, please visit: Sacramento Municipal Utility District 2

3 1. Executive Summary An electronics manufacturer in Rancho Cordova, California installed Catalyst Efficiency Enhancing Controllers on four package rooftop units (RTU) for evaluation. The Catalyst controller optimizes outside air intake economizer position and provides variable speed control to the single (full) speed single zone air handler motor. The controller, shown in Figure 1, has remote communication which allows real time observation and control of the RTU via the internet. Approximately 10 months of unit performance data are collected, alternating control system modes periodically so that energy savings under on and off of variable speed controls can be calculated. Multiple variable linear regression models of unit power as a function of NOAA weather data and occupancy information are created and applied to Typical Meteorological Year (TMY3) weather data in order to predict typical annual energy savings. The savings results for each of the four units are shown in Table 1 by the equipment unit ID. Unit ID Figure 1: Photo of Catalyst Control Unit. Table 1: Energy Savings from Catalyst Controllers. Annual kwh Catalyst off Annual kwh Catalyst on kwh Saved % Savings ,056 42,185 25,871 38% ,574 19,702 26,872 58% ,069 50,015 24,054 32% ,375 38,202 20,173 35% Overall 247, ,104 96,970 39% Sacramento Municipal Utility District 3

4 The savings refer to a baseline package system with a very basic one (full) speed fan and economizer controls, including indoor air handler fan operating at full-speed. These results are visualized as bar charts of annual kwh savings and percentage savings in Figure 2. Figure 2: Annual and Percentage Savings by Equipment Unit ID. The peak savings are calculated as the average reduction in power between June 1 and September 30, non-holidays, Monday - Friday, from 4 p.m. to 7 p.m. The total peak savings for the four units is 14.8 kw, or 24%. The project cost to upgrade the HVAC controls for all four units was $44,893. Assuming an average power cost of 12 /kwh, this project has a simple payback period of about 3.9 years without any incentive. Sacramento Municipal Utility District 4

5 2. Project Description 2.1 Background An electronics manufacturing facility in Rancho Cordova, CA has 80 one speed packaged rooftop HVAC units. Catalyst Efficiency Enhancing Controllers produced by Transformative Wave Technologies have been installed on four of these rooftop package units for evaluation. Two adjacent identical units on the north side and two adjacent identical units on the south side of the test bench area were selected for the study, with facility names and locations indicated in Table 2. Table 2: Package Unit Names and Locations. Unit Key ID Name Serves 1062 AC14N A1 A2 Floor 1063 AC15S A3 A4 Floor 1064 AC27 F3 F4 Floor 1065 AC15N E3 E4 Floor The Catalyst controllers are connected with secure radio communications to provide remote access via the internet for viewing system operation and providing operator control. The Catalyst system has a user friendly interface that shows real time operating conditions of the units. ADM developed a strategy in cooperation with Transformative Wave to measure the savings associated with their controllers. The new controllers are toggled on and off periodically every few days throughout the year so that performance data are obtained during all conditions both with and without the efficiency measure activated. The Catalyst controllers were on for three days and then off for two days, the neighboring RTU used the same cycle but was shifted by one day to achieve all sets of active combinations. Savings for the units are calculated and applied to Typical Meteorological Year (TMY3) weather data using a multiple variable linear regression for each package unit. The Catalyst controller claims several advantages. The fan speed is modulated with a CO 2 sensor, and the fan speed varies depending on the system mode. The modes and respective percent fan speed are: Ventilation mode (40% default, 90% max) Economizer mode (70%) First stage cooling (75%) Second stage cooling (90%) First stage heating (75%) Second stage heating (90%) Sacramento Municipal Utility District 5

6 The Catalyst controller also determines if outside air can be used for heating or cooling. Using temperature set points, it can enable multiple stages of mechanical heating or cooling, and is equipped with upper and lower limits beyond which no heating or cooling functions will be enabled. Lastly, the Catalyst system controls ventilation. The damper is closed if unoccupied, and when occupied it will open to the default 5% until there is a call for ventilation or cooling. A CO 2 sensor is used to control the outside air damper. 2.2 Assessment Objectives The goal of this study was to understand the performance characteristics of the Catalyst controller. This included monitoring the energy consumption and assessing energy savings compared to the baseline, existing one speed condition and marginal performance of economizers. 2.3 Methodology The Catalyst control system has the capability to record data from sensors. The Catalyst system uses a set of sensors for analysis of system performance and is part of the control system provided to the customer. ADM recommended including power measurements by the system since the Catalyst system is already designed to collect and store data from sensors. This addition allowed the primary data collection to be centralized. A large open air area in the core of the building is used for bench testing and equipment burn-in. The area is served by eighteen 20 ton air conditioning units with electric element heating. A sample of four air conditioning units, consisting of two adjacent units in the north end (#14N and 15N) and two adjacent units in the south end (#15S and 27S) of the roof, were selected to have Catalyst controllers installed for the pilot test. One of the units, along with its communication and measurement hardware, is shown in Figure 3. Sacramento Municipal Utility District 6

7 Figure 3: 20-ton HVAC unit with Catalyst and Monitoring Hardware Installed. In addition to its typical installation procedures, Transformative Wave agreed to install two WattNode power meters on each unit based on data collection requirements outlined by ADM. The WattNodes are Modbus compatible and provide instantaneous power readings upon request from the controller. One WattNode measures the total power to the unit and the other measures power of the indoor air handler (with VFD). Two Hobo Temp/RH battery operated U loggers are deployed in the work space to collect temperature and relative humidity data. One logger is deployed in the north area under the return register of unit 15N, and one is deployed in the south area in the vicinity of unit 15S. The loggers hold several months of data but are visited and have their data manually downloaded every two to three months. After the equipment was installed, the units were observed for a period of approximately two months in order to identify the typical fan speed and damper position conditions. One-time measurements of air flow were then taken at these various conditions for both the total unit air flow and the outside air intake. Specifically, the air flow measurements were taken for the outside air intake and supply air (between filters and evaporator coils) for two to three conditions of fan speed and damper position. The measurements were taken using a TrueFlow plate in place of the air filters for the total air flow measurement and also outside air intake measurements, as shown in Figure 4. Sacramento Municipal Utility District 7

8 Figure 4: Temporary Air Flow Measurement Hardware. Additionally, ADM took one-time power measurements in the same locations as the WattNodes power meters to verify the operation and confirm correct installation. ADM worked with Transformative Wave to develop a schedule of operation that includes days where the Catalyst controllers revert back to a standard mode (baseline operation where fan operates at full speed). The schedule provides combinations of operation so that the two units at one end of the building will be: 1. Both on, 2. One on and one off, 3. Both off, 4. The other on and the first off. Where on means the Catalyst is controlling the unit optimally and off means that the unit is operating in standard baseline mode. This type of alternating schedule allows for analysis of each unit individually and for analysis of interaction between units within the same area. It also provides data regarding operation of the units in both modes through all seasons and weather cycles. Sacramento Municipal Utility District 8

9 3. Results For each of the four package units, energy consumption with and without the Catalyst controller was logged for ten months, from January 2014 October 2014, at intervals of 1 minute between data points. Weekday profiles of the energy consumption for each of the four HVAC units are plotted in Figure 5, which have been assigned Equipment ID numbers: 1062, 1063, 1064, and Figure 5: Power Curves by Day of Week for each of the Four Units. Although some areas of the facility run 24/7, Figure 6 shows that the occupancy of the building is different for weekdays compared to weekends by plotting output from the CO 2 sensor. Sacramento Municipal Utility District 9

10 Figure 6: Carbon Dioxide Data by Day of Week for each Unit. Using the CO 2 sensor data, normalized profiles are created for an occupancy variable ("occ"). A sine wave function is fit to this curve as shown in Figure 7 in order to improve the regression model. A separate occupation model is created for weekdays and weekends. Figure 7: Illustration of Occupancy Sine Function Fitting. To visualize energy savings (see Figure 8), the power consumption data are aggregated by hour for all of the weekdays for each of the package units. These data are labeled by the control mode flag "ESMMode", where if TRUE the Catalyst controller is active, and if FALSE it is turned off. Sacramento Municipal Utility District 10

11 Figure 8: Power With and Without Controller Active. To calculate savings, a regression model is created for each of the two control modes on each of the four HVAC units (eight models total). Some units had less spread in power consumption as a function of temperature and other variables, which gave a better fitting model. As shown in the Figure 9 plots, unit 1065 has the least variation of power consumption, strongly correlating with temperature. Although unit 1063 has the largest spread and poorest fit, it still provides a fit that is acceptable because it sufficiently represents savings for this purpose. Figure 9: Power Versus Temperature Scatter Plots. Sacramento Municipal Utility District 11

12 The variations in HVAC load over time can be visualized by specifying line color by month as shown in Figure 10. In the case of unit 1063, the early months of the year (the orange and green areas associated with January-March) have different power consumption trends than the later months (the pink and blue areas associated with July September). The thermal load in the zone decreased over time during the monitoring period, which reduces the quality of the model in this zone. Figure 10: Power by Month to Visualize Load Changes Over Time. To find the typical savings for the facility, regression models are applied to typical weather data (in TMY3 format). The independent variables include occupancy curves developed from the carbon dioxide sensors, degree days, and temperature. The annual profiles are plotted in Figure 11. The year 1994 is a dummy year used for programming; TMY3 data are actually a compilation of many different years. Sacramento Municipal Utility District 12

13 Figure 11: Illustration of Typical Annual Energy Use for each Mode by Unit. The savings results are as follows in Table 3: Unit ID Annual kwh Catalyst off Table 3: Energy Savings Summary. Annual kwh Catalyst on kwh Saved % Savings ,056 42,185 25,871 38% ,574 19,702 26,872 58% ,069 50,015 24,054 32% ,375 38,202 20,173 35% Overall 247, ,104 96,970 39% The project cost to upgrade the HVAC controls for all four units was $44,893. Assuming an average power cost of 12 /kwh, the project has a simple payback period of about 3.9 years. 4. Conclusion HVAC systems are sized for design conditions and many are oversized, just to be on the safe side. In any location peak conditions, or design days rarely occur and single speed RTU s know only one thing full force, full speed anytime heating or cooling is called for. If instead of running full speed, the fan is modulated. Catalyst addresses this issue and improves economizer performance and the results of this field test demonstrate energy savings ranging from 32% to 58% averaging 39%. Sacramento Municipal Utility District 13

14 Catalyst Efficiency Enhancing Controllers can be effective energy saving devices for HVAC applications where baseline ventilation fans are simply toggled 100% on or off, and economizer control strategies are either not implemented or are very simple. At this facility, a typical savings of 39% was calculated for the HVAC package units. Sacramento Municipal Utility District 14

15 5. Appendix To visualize energy savings, power is plotted as a function of outside air temperature, with color indicating the control mode. A general trend of lower power consumption when ESMMode = TRUE can be observed in Figure 12. Figure 12: Effect of Control Mode on Power The cooling is activated in stages, depending on the building demand and the outside temperature. Colors indicate the number of compressor stages in the plots in Figure 13. Minimal difference is observed by control system mode, because the stages of the air conditioner did not change with the control system retrofit. Figure 13: Cooling Stage Visualization Sacramento Municipal Utility District 15

16 Figure 14 shows a plot looking at the fan speed, which in the new control system is predominantly split into five levels of operation: 0%, 40%, 75%, 90%, and 100%. Figure 14: Staged Fan Speed Operation Using Controller. The variable Econ Mode indicates whether the economizer is being used for cooling, and is plotted below in Figure 15. The economizer temperature set point can be seen in the charts as the vertical line where the color changes. Figure 15: Economizer Operation. The R values for the various regression models are output in Table 4 below. We see that for some units, #1063 in particular, the regression fit is weak, due to internal load changes on larger time scales which we do not have data for. Sacramento Municipal Utility District 16

17 Table 4: Table of Regression Model R 2 Values. Unit ID Control Mode R TRUE 73% 1063 TRUE 36% 1064 TRUE 65% 1065 TRUE 85% 1062 FALSE 80% 1063 FALSE 60% 1064 FALSE 74% 1065 FALSE 92% The four units analyzed are located in pairs, with units 1062 and 1065 being near each other on the roof of the building, and units 1063 and 1064 being adjacent. To investigate whether the mode of one unit may affect the performance of its neighbor (interactive effect), profiles were created and plotted for all of the control mode combinations of the pair. For example, for the plot labeled unit 1062, the four different control combinations are plotted for the unit pair 1062 & 1065, where "T" indicates a Catalyst-controlled unit, and "F" indicates a unit with baseline controls. The first letter is the unit control mode, and the second letter is its neighbor s control mode. Figure 16 shows that when one unit is true, the status of the other unit does not have a substantial influence on the power consumption. Furthermore, this small effect is inconsistent in sign, so the net savings is minimally affected. Figure 16: Unit Interactivity Visualization. Sacramento Municipal Utility District 17