co2 refrigeration system report march 2017...emerging energy solutions 16071 nw ashfield dr....

Emerging Energy Solutions 16071 NW Ashfield Dr. Beaverton, OR 97006 (503)475-1762 [email protected]

New Seasons Market 2755 77th Ave SE

Mercer Island, WA 98040

CO2 Refrigeration System Report March 2017

Commissioning done by:

Manufacturer: Hussmann Contractor: RUI Refrigeration

Report published by:

Klas Berglof, ClimaCheck Sweden AB Sean McCaffery, Emerging Energy Solutions

New Seasons Market – Mercer Island CO2 System


Executive Summary The CO2 system installed at the New Seasons Market located in Mercer Island, Washington has been monitored by the ClimaCheck Analyzer since October of 2016 as part of a study being conducted by the Bonneville Power Administration. Final commissioning of the ClimaCheck System was November 21, 2016. Baseline is based on this date with post optimization is January 25, 2017. On January 9, 2017 Hussmann and RUI the contractor started their commissioning of the system. Additionally, RUI was addressing a CO2 leak that was discovered. Multiple changes were made to the system. These initial changes did show savings but Hussmann realized something was wrong and conducted a second round of changes January 23, 2016. Additionally, the leaving temp sensor of the gas cooler was found to be mounted wrong. With the temp sensor corrected and additional changes being implemented to the MT which resulted in savings between 30 – 35%. Since then, the system has been following the energy signature line quite well, with periodical increases. Additional savings potential:

• Heat reclaim is non-existent. CO2 offers significant opportunities for energy savings from heat recovery.

o Once Heat reclaim is implemented, control strategy should be revisited using ClimaCheck to find the sweet spot of the system taking into account oil return and manufacturers suggested superheat settings.

• Control of the compressors has too much short cycling on the LT and MT. Short cycling causes excessive energy consumption.

o Check compressor control settings

• Defrost cycles should also be looked at.



Contents Executive Summary ............................................................................................................................................................ 1

Background ......................................................................................................................................................................... 3

1. System Design ......................................................................................................................................................... 3

1.1 System Layout ......................................................................................................................................................... 3

2. Energy Consumption ............................................................................................................................................... 4

2.1 Energy Consumption Medium Temp - Total ........................................................................................................... 4

2.2 Energy Consumption – Low Temperature – Total ................................................................................................... 5

3. Optimization by Hussmann and RUI ........................................................................................................................ 6

3.1 December 2, 2016 Adjustment to fan Speeds ........................................................................................................ 6

3.2 January 9, 2017 Changes. ........................................................................................................................................ 7

3.2.1 Overview of Medium Temperature on January 9, 2017 ......................................................................................... 7

3.3 January 23 – 25 Changes. ....................................................................................................................................... 8

3.3.1 Overview of changes from January 9 to January 25, 2017 .................................................................................... 9

3.3.2 7 Days prior to January 25th changes .................................................................................................................. 11

3.3.3 Changes in COP in the month of January. ............................................................................................................ 11

4 Medium Temperature Current Operating Conditions ......................................................................................... 12

4.1 Sub cool, Evaporation and superheat ................................................................................................................. 12

4.1.1 Gas cooler and Compressor power usage ........................................................................................................... 12

4.1.2 Compressors ....................................................................................................................................................... 14

5 Low Temperature Current Operating Conditions ................................................................................................ 15

5.1 Sub cool, Evaporation, Superheat and Condensing ............................................................................................. 15

5.2 Compressors ......................................................................................................................................................... 15

5.2.1 Power to Compressors ......................................................................................................................................... 16

5.2.2 Discharge of Compressors ................................................................................................................................... 16



Background

This report is based on the operation of the trans-critical CO2 System located at the New Seasons Market located in Mercer Island, Washington. The report will cover the changes made by Hussmann and RUI Refrigeration in January 2016. Current operation and savings achieved will also be covered.

1. System Design The trans-critical CO2 system at Mercer Island is a system designed as a booster system with the Low Temperature stage is compressing to the medium temperature level to achieve a two-stage compression.

There is a secondary glycol meat cases which requires 20°F glycol to operate properly. This results in the lower saturated evaporation temp of 15-16°F that is required for the MT to maintain the desired glycol temp. LT is designed to maintain a -20F evaporation temp and is maintaining a -10°F in the cases. Gas Cooler model number TVD 141/Low Speed manufactured by RefPlus Inc.

1.1 System Layout

Medium Temperature Compressors Low Temperature Compressors

Bitzer 4CTC-30K w/VFD Copeland ZOD34K3E-TFD *Digital

Bitzer 4DTC-25K Copeland ZO34K3E-TFD

Bitzer 4FTC-30K Copland ZO58K3E-TFD

Bitzer 4FTC-25K



2. Energy Consumption

2.1 Energy Consumption Medium Temp - Total

In the following graph, Yellow line shows ambient temperature, Blue line is energy signature before optimization mid-January at prevailing outdoor temperature, red line is energy signature post optimization at prevailing outdoor temperature. Red bars are measured energy consumption. Gas cooler fans and medium temperature compressors are included in the MT total. Starting from January 20, 2017 with Jan 25th being the day in which a significant reduction is shown up to current.

Energy and Dollar Usage since connected. Here you can see the cost savings from the pre-optimization Blue line in above graph.

First changes made to system Jan 9, 2017

Second changes made to system Jan 24, 2017



Energy consumption can be separated between compressors and gas cooler fans. First graph below shows the savings for the compressors and an increase of energy consumption for the gas cooler fans. The increase in fan consumption was small in comparison to the decrease in consumption from the compressors. However there seems to be some events causing the gas cooler to use more energy than predicted on February 9 and March 14th.

Higher than predicted

Compressor Energy

Condenser Energy

Period when Hussmann noted something was not correct.



2.2 Energy Consumption – Low Temperature – Total Shown below, the Low Temperature compressors appeared to show limited savings in early February but now appears to have reverted back and using more energy.

Looking closer at the LT Compressors, it is shown that the compressors were staying within the statistical profile with slight savings but since March 3rd it appears the compressors are using slightly higher energy.



3. Optimization by Hussmann and RUI The following sections will outline the changes Hussmann and RUI made. There are different dates when changes were made and are noted.

3.1 December 2, 2016 Adjustment to fan Speeds In the below graph it can been seen the change to the gas cooler when the minimum fan speed changed from 15Hz(25%) to 10 Hz (16.6%).

3.2 January 9, 2017 Changes.

• Minimum gas cooler pressure setting was changed from 930 psi (64 Bar) to 650 psi (45 Bar). We don’t expect to get that low, but this is basically a safety and we wanted to get it out of the way of our gas cooler fan controls.

• The sub cooling setting for the ICMTS valve was changed from 1.8F (1C) to 5.4F (3C)

• The gas cooler fan control was lowered from a setting of 76F (24.4C) (907 psi, 62.5 Bar) to 64F (17.8C) (774 psi, 53.4 Bar) for several hours before being lowered again to 54F (12.2C) (675 psi, 46.5 Bar)

o The desired set point was to be in the 63F (763 psi) range to allow for a 60F (15.6C) outlet temp once sub cooling was taken into account, but there was an issue that popped up and the 54F (12.2C) (675 psi, 46.5 Bar) setting was used

• The gas cooler controlling sensor was changed from the gas cooler outlet temperature sensor to a temperature that is calculated by converting the gas cooler outlet pressure reading to temperature

Change made



3.2.1 Overview of Medium Temperature on January 9, 2017 The ClimaCheck graphing can look at multiple variables at the same time giving the ability to see how those variables interact with each other. In this graph, Discharge, Condensing, Power to the Compressors, Superheat, Evaporation, Isentropic efficiency of the compressors and outdoor temperature are shown. Below is displayed the change of operation when high pressure control was adjusted for higher energy efficiency. It can be seen how discharge temperature also decreased significantly.

• Compressor discharge (Brown Line) decreased from 183°F - 165°F - 140°F

• Condensing Temperature (Red Line) lowered from 75°F - 54°F

3.3 January 23 – 25 Changes.

• The number of steps for the flash tank bypass valve was modified to match the steps in the CCM40

• The gas cooler fan control set point was changed from 54F (12.2C) (675 psi, 46.5 Bar) to 58F (14.4C) (713 psi, 49.2 Bar)

o “There was still something odd occurring that prevented the desired set point from being used”

• The issue that was preventing the desired set points was the gas cooler outlet temperature sensor being used by the Danfoss high pressure controller. It was found to be mounted incorrectly. The sensor mounting was corrected and the readings were now accurate.

• The gas cooler fan control set point was changed from 58F (14.4C) (713 psi, 49.2 Bar) to 63F (17.2C) (763 psi, 52.6 Bar). With the 63F (17.2C) (763 psi, 52.6 Bar) outlet pressure to temperature set point, the actual gas cooler outlet temp is centered around 60F when the sub cooling is taken into account.



Just after 6 a.m. January 25th the discharge increased significantly as condensing pressure increased from approx. 58°F to 65°F. Compressor power (Grey) level at a 25kW. Gas Cooler is averaging 1.3kW. The increase of condensing pressure clearly correlate to a higher compressor power.

3.3.1 Overview of changes from January 9 to January 25, 2017 In the following graphs, it can be seen the changes done over a 30-day period. The following are being graphed: Discharge, condensing, compressor power and gas cooler power. On January 9th, the first changes were made which resulted in significant reductions in Discharge, condensing and compressor power. The gas cooler power increased slightly. As noted by Hussmann, around January 16th the gas cooler started to run more than it was supposed to. Compressor power increased as well. This created fluctuations in the discharge and condensing. These fluctuations would also be amplified throughout the whole refrigeration cycle, causing strange behaviour in other areas of the system. On January 23, a change was made to the system which increased the compressor power and reduced the gas cooler. Then around January 24th per Hussmann, “the issue that was preventing the desired set points to be used was found and corrected. The gas cooler outlet temperature sensor being used by the Danfoss high pressure controller was found to be mounted incorrectly. The sensor mounting was corrected and the readings were now accurate”. This change did correct the issue. The end result is the discharge increased, Condensing pressure increased and compressor power increased while the gas cooler decreased and now looks stable.



3.3.2 7 Days prior to January 25th changes

3.3.3 Changes in COP in the month of January.



4 Medium Temperature Current Operating Conditions

4.1 Sub cool, Evaporation and superheat Below it can be seen how pressure control causes fluctuations of 10°F out of the gas cooler and 5°F in evaporator. It is also shown, that when the gas cooler fan power increases the fluctuation in sub cool reduces. (See orange line underneath the yellow sub cool line). This is occurring when the dT between ambient and gas cooler exit temperature decreases making the system less sensitive for the control of pressure control valve.

4.1.1 Gas cooler and Compressor power usage Below graph shows the compressor usage and gas cooler usage over the last 7 days. According to Hussmann, “an ambient close to or greater than 60F will cause the gas cooler fans to run at full speed. We are trying to maintain an outlet temperature at the gas cooler of 60F, so anything at or above that we absolutely will be running the fans 100%.” In the second graph, the compressor power early on March 16th is higher than expected at low ambient conditions.



Closer look at March 14 – 16th it is shown that compressors are running more than needed. Early March 16th compressor power consumption is higher than normal during low ambient conditions.



4.1.2 Compressors The graph below correlates with the higher usage of compressor power in above graph. It is shown how frequently compressors start and then operate for one or two minutes to stop at the same time as another compressor starts. To reduce the number of starts would improve energy efficiency and reduce wear on compressors. What is the CPC control setting? Tightest, moderate?

Enlarged graph showing the cycling (start and stop) of the compressors. Defrost cycles should also be taken into consideration when looking at these specific times.



5 Low Temperature Current Operating Conditions

5.1 Sub cool, Evaporation, Superheat and Condensing In the following graph, Evaporation is at design, fluctuating a few degrees up or down. It is understood the coldest case should be at -10°F.



5.2 Compressors

5.2.1 Power to Compressors From March 13th to March 16th it is shown that compressor power has increased. As shown above with MT compressors on March 16th, the LT compressors also are using more power. There seem to be a clear correlation to the compressors short cycling and the increased power consumption.

5.2.2 Discharge of Compressors In the following, the compressor discharge is being shown. Compressor 1 at times has a temperature +20F higher discharge than other compressors that are running. Compressor 2 cycles in the middle of the night.

co2 refrigeration system report march 2017...emerging energy solutions 16071 nw ashfield dr....

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