CHILLED WATER SYSTEM OPTIMIZATION

CHILLED WATER SYSTEM OPTIMIZATION PowerPoint PPT Presentation


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Introductions. David A. GrecoSales EngineerCarrier Corporation. . Agenda. How Are Systems Evaluated Today ? (ARI 550/590-98)How Will Chiller Systems Be Evaluated Tomorrow ? / Why ?. . How Are Water Chillers Evaluated Today?. Full Load Efficiencyand Part Load Efficiency (IPLV). ARI Released The New Standard in December 1998.

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CHILLED WATER SYSTEM OPTIMIZATION

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1. CHILLED WATER SYSTEM OPTIMIZATION Before giving this presentation, please read all supporting documentation regarding this Lunch and Learn. Also, know how to run the Chiller System Optimizer v 2.0,AND BE ABLE TO EXPLAIN ALL CALCULATIONS. Before giving this presentation, please read all supporting documentation regarding this Lunch and Learn. Also, know how to run the Chiller System Optimizer v 2.0,AND BE ABLE TO EXPLAIN ALL CALCULATIONS.

3. Agenda How Are Systems Evaluated Today ? (ARI 550/590-98) How Will Chiller Systems Be Evaluated Tomorrow ? / Why ? Read SlideRead Slide

4. How Are Water Chillers Evaluated Today? Full Load Efficiency and Part Load Efficiency (IPLV) People that buy chillers primarily look at 2 efficiency numbers, full load and part load efficiency. Full load is easy to understand. Given a set of water conditions, what is the chiller’s efficiency at 100% load? Part Load efficiency is a little more complex...People that buy chillers primarily look at 2 efficiency numbers, full load and part load efficiency. Full load is easy to understand. Given a set of water conditions, what is the chiller’s efficiency at 100% load? Part Load efficiency is a little more complex...

5. ARI Released The New Standard in December 1998 Available through the ARI web site: WWW.ARI.ORG The air conditioning industry’s governing body released a new standard December of 1998. This was to help compare water cooled chillers.The air conditioning industry’s governing body released a new standard December of 1998. This was to help compare water cooled chillers.

6. ARI PART LOAD WEIGHTING FACTORS To evaluate part load performance, the standard suggests that chillers be run at 4 discrete points, 100%, 75%, 50% and 25% load. The chiller’s efficiency at each point is then given a weighting factor. The higher the weighting, the more it is assumed the chiller will run at this point. For example, it is assumed that the chiller will run very little at 100% load, but much of its time at 50%. Graphically it looks like this. To evaluate part load performance, the standard suggests that chillers be run at 4 discrete points, 100%, 75%, 50% and 25% load. The chiller’s efficiency at each point is then given a weighting factor. The higher the weighting, the more it is assumed the chiller will run at this point. For example, it is assumed that the chiller will run very little at 100% load, but much of its time at 50%. Graphically it looks like this.

7. Condenser Water Turndown Associated with each part load point (100%, 75%, 50% and 25%) is a condenser water temperature. It is assumed that the chiller will run much of its time at these specific water temperatures. For example, it is assumed that when a chiller runs at 100% load, it sees 85 degree condenser water. When running at 75% it sees 75 degrees, and so on. Graphically, the condenser water turndown looks like this. Build slide: click and load line will wipe left-downAssociated with each part load point (100%, 75%, 50% and 25%) is a condenser water temperature. It is assumed that the chiller will run much of its time at these specific water temperatures. For example, it is assumed that when a chiller runs at 100% load, it sees 85 degree condenser water. When running at 75% it sees 75 degrees, and so on. Graphically, the condenser water turndown looks like this. Build slide: click and load line will wipe left-down

8. An interesting note appears in the ARI 550/590-98 White Paper. It states the following “read slide”. An interesting note appears in the ARI 550/590-98 White Paper. It states the following “read slide”.

9. Evaluating Systems Does and IPLV formula for a single chiller describe the reality...Does and IPLV formula for a single chiller describe the reality...

10. Building Load Profiles ARI assumes that every building in the world has a load profile like the one shown in red. This is obviously not the case. If you are designing a job for a process that needs to run loaded all the time you might have the profile shown in green. Your actual load profile will vary greatly depending on the application.ARI assumes that every building in the world has a load profile like the one shown in red. This is obviously not the case. If you are designing a job for a process that needs to run loaded all the time you might have the profile shown in green. Your actual load profile will vary greatly depending on the application.

11. Evaluating Systems The IPLV Formula Does Not Describe Reality Building Load Profiles Multiple Chillers As stated in the ARI White paper, the IPLV formula does not describe multiple chiller installations.As stated in the ARI White paper, the IPLV formula does not describe multiple chiller installations.

12. This is very important when you consider that 85% of machines are sold into a multiple chiller installation. This is very important when you consider that 85% of machines are sold into a multiple chiller installation.

13. Three Chillers: 33/33/33%Operation Is this important? Lets look at a typical 3 chiller installation. Each machine is the same size. On this graph, %Building Load is plotted vs. % Chiller Load. Chiller 1 turns on and ramps up until it cannot meet set point, then chiller #2 comes on. These two operate until they cannot meet set point, then chiller #3 comes on. All 3 operate until full building load is reached.Is this important? Lets look at a typical 3 chiller installation. Each machine is the same size. On this graph, %Building Load is plotted vs. % Chiller Load. Chiller 1 turns on and ramps up until it cannot meet set point, then chiller #2 comes on. These two operate until they cannot meet set point, then chiller #3 comes on. All 3 operate until full building load is reached.

14. Three Chillers: 33/33/33%Operation One very important note. Recall the ARI IPLV formula. 57% of the formula weighting is at the 25% and 50% points. In this example, only one chiller will operate at 50% load, this is at 16% building load. Only one chiller will operate at 25% load, this is at about 7% building load. Weighing these points so heavily does not make sense in this case. One very important note. Recall the ARI IPLV formula. 57% of the formula weighting is at the 25% and 50% points. In this example, only one chiller will operate at 50% load, this is at 16% building load. Only one chiller will operate at 25% load, this is at about 7% building load. Weighing these points so heavily does not make sense in this case.

15. Three Chillers: 33/33/33%Operation Another very important note concerns the condenser water temperature. The 1998 standard states that the 100% chiller point should be evaluated with 85 degree condenser water. In this case, 85 degree condenser water will probably only occur at 100% building load, of which very little time is ever spent there. There are two other building load points that have chillers running at 100%, both of these will have something lower than 85 deg. condenser water. The building operates at both of these points much more often than 100% building load. Another very important note concerns the condenser water temperature. The 1998 standard states that the 100% chiller point should be evaluated with 85 degree condenser water. In this case, 85 degree condenser water will probably only occur at 100% building load, of which very little time is ever spent there. There are two other building load points that have chillers running at 100%, both of these will have something lower than 85 deg. condenser water. The building operates at both of these points much more often than 100% building load.

16. Evaluating Systems The IPLV Formula Does Not Describe Reality Building Load Profiles Multiple Chillers Local Weather Data The Standard does not take into account variations in weather data. An “average” city is used.The Standard does not take into account variations in weather data. An “average” city is used.

17. Evaluating Systems The IPLV Formula Does Not Describe Reality Building Load Profiles Multiple Chillers Local Weather Data Mixing Chillers Economizer Operation Demand Charges Tower Efficiency…..etc. There are a number of other factors that greatly affect how a chilled water system will operate, non of which are taken into account in the the IPLV formula. These include: the role of economizers cooling tower efficiency chiller operating schedule demand charges ect...There are a number of other factors that greatly affect how a chilled water system will operate, non of which are taken into account in the the IPLV formula. These include: the role of economizers cooling tower efficiency chiller operating schedule demand charges ect...

18. There is a Better Solution There is a way to optimize YOUR chiller system. It’s called Chiller System Optimizer. There is a way to optimize YOUR chiller system. It’s called Chiller System Optimizer.

19. Actual weather data Building load characteristics Number of chillers Operational hours Economizer capabilities Energy drawn by auxiliaries such as pumps and cooling towers, especially for multiple chiller systems” “It is best to use a comprehensive analysis that reflects the ... Read the slide.Read the slide.

20. The CSO will help Estimate chiller plant energy cost Compare various system to determine which one is most cost effective Compare VFD vs Constant speed Compare cooling towers large vs small Calculate savings from economizer cooling cycles

21. The ARI IPLV calculation is also shown Note that this only takes into account 4 discrete points (100%, 75, 50 and 25%) with specific weighting factors and condenser water temperatures. These weighting factors and temperatures never change. Note that the SPLV, and IPLV formulas are the same, its just that SPLV is customized for each particular job. It also uses many dynamic points to estimate the answer, as opposed to just 4 static points for the IPLV. The ARI IPLV calculation is also shown Note that this only takes into account 4 discrete points (100%, 75, 50 and 25%) with specific weighting factors and condenser water temperatures. These weighting factors and temperatures never change. Note that the SPLV, and IPLV formulas are the same, its just that SPLV is customized for each particular job. It also uses many dynamic points to estimate the answer, as opposed to just 4 static points for the IPLV.

22. Table 5 pulls everything together. Once again start with Bin Data. As you move across you come to Cooling Hours. For your given city, there are this many hours in each Temp Bin. Ton Hours are simply the# of tons needed per bin times the # of hours per year. Each Temp bin is then weighted using Ton Hours. This weighting factor is customized for each application. Bin wt. Factor is the customized weighting for each bin. System Kw/ton comes from the above table and Bin Ratio is just System Kw/ton / Weighting factor. This is similar to an integration in evaluating the area under a curve. Minimize the assumptions and try to get a better estimate of the true area. Table 5 pulls everything together. Once again start with Bin Data. As you move across you come to Cooling Hours. For your given city, there are this many hours in each Temp Bin. Ton Hours are simply the# of tons needed per bin times the # of hours per year. Each Temp bin is then weighted using Ton Hours. This weighting factor is customized for each application. Bin wt. Factor is the customized weighting for each bin. System Kw/ton comes from the above table and Bin Ratio is just System Kw/ton / Weighting factor. This is similar to an integration in evaluating the area under a curve. Minimize the assumptions and try to get a better estimate of the true area.

23. Inputs

24. Chiller Plant Efficiency Comparison

25. Energy Cost By Month

26. System PLV Report

27. System Load Profiles

28. Result: Increased Tons, Decreased kW/Ton with Lower Entering Condenser Water Temperature ACCUMETER FLOW CONTROL

29. Condenser Temperature Profiles

30. System Performance Profile

31. 1500 Ton, Water Cooled Chiller Job It may be best to look at a few examples. Consider a job that requires 1500 tons. A typical system may consist of (3) 500 ton chillers. It may be best to look at a few examples.

32. Or... Is There A Better Solution? There are other possibilities though. For example, its possible to try (2) 650 ton centrifugals for the large base load. Since screw chillers operate best at part load conditions, it may be best to use either a large or small screw chiller for these points. What’s the best system??? There are other possibilities though. For example, its possible to try (2) 650 ton centrifugals for the large base load. Since screw chillers operate best at part load conditions, it may be best to use either a large or small screw chiller for these points. What’s the best system???

33. CONSTANT SPEED OR VFD’s DOES THE OPTIMAL SYSTEM CONSIST OF ALL CONSTANT SPEED MACHINES? VFD ON THE LEAD MACHINE? VFD ON ALL MACHINES? Another situation that comes up quite often is when to use a VFD on the chiller. For any given job, is it best to use all constant speed machines, one VFD or all VFD’s. As always, it depends... Another situation that comes up quite often is when to use a VFD on the chiller. For any given job, is it best to use all constant speed machines, one VFD or all VFD’s. As always, it depends...

34. WHAT’S A BETTER TOWER CHOICE: BIG or SMALL TOWER? Another common situation involves sizing cooling towers. As we mentioned in the earlier example, colder condenser water temperatures allow the chillers to operate more efficiently. This can translate into a larger cooling tower. The question is, how should you size the cooling tower to optimize your investment?Another common situation involves sizing cooling towers. As we mentioned in the earlier example, colder condenser water temperatures allow the chillers to operate more efficiently. This can translate into a larger cooling tower. The question is, how should you size the cooling tower to optimize your investment?

35. What Does This Do For Me? True System Modeling Minimize Assumptions Enhance Your Productivity Easy To Compare Different Chiller Systems Put a $ Value On Different Scenarios Good Tool To Use With Your Customers Shows You Provided The Best System CSO will also enhance your productivity. It allows for an easy comparison of various systems. What is best for the customer (a larger cooling tower for example?) It is also a good tool to use with your customers. You can easily explain why one system may be better than another. CSO will also enhance your productivity. It allows for an easy comparison of various systems. What is best for the customer (a larger cooling tower for example?) It is also a good tool to use with your customers. You can easily explain why one system may be better than another.

37. David A. Greco Carrier Corporation 780 Dedham St. Canton, Ma 02021 Phone 781-774-6336 Fax 781-774-6399

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