1. Lecture Objectives: Learn about thermal storage systems
Discs pumps and plumbing

2. Thermal storage for adjustment production to consumption
We need
a thermal storage
somewhere in
this system !

3. Example problem

5. Thermal storage Store heat Store cooling energy
Many issues to consider (∆T, pressure, losses,…. )
Store cooling energy
Chilled water
For cooling condenser
For use in AHU (cooling coils)
Ice storage
Compact but…
Other materials (PCMs) that change phase the temperature we need in cooling coils
Many advantages, but disadvantages too!

6. On-Peak and Off-Peak Periods
This profile depends on the type of building(s) !

7. Chilled water tank
Use of stored cooling energy
Store
Use

8. Which one is better ? Depends on what you want to achieve:
Peak electric power reduction
Capacity reduction
…..

9. Downsizing the Chiller
Lower utility costs
Lower on-peak electrical consumption(kWh)
Lower on-peak electrical demand (kW)
Smaller equipment size
Smaller chiller
Smaller electrical service (A)
Reduced installed cost
May qualify for utility rebates or other incentives

10. Sizing storage system (use Annual Cooling-Load Profile)
How often you need to use it?
What are the cost-benefit curves ? What is the optimum size ?

11. Ice Storage Tank Many issues ! ….
As freezing progresses progress the ice
becomes thicker and significantly
impedes heat transfer

12. Open Ice Storage Tank
Also issues !
…..

13. Fluid Flow Rate and Freeze ΔT

14. Impact on Chiller Efficiency

15. PCMs
A. Sharma et al. / Renewable and Sustainable Energy Reviews 13 (2009)

16. Other latent heat thermal storage systems (research is ongoing)

17. Construction and benefits
Active
Passive (wall)

18. Stratified chilled water tanks

19. Temperature and dynamics
Temperature at outlet during the
changing cycle of the tanks

20. Stratified chilled water tanks diffuser geometry
Challenge:
“Pull” large amount of energy without
disturbing stratification

21. Modeling
Write energy and mass balancer
equation for each section

22. Installation of thermal storage system
Upstream
Downstream
• Increases chiller efficiency
• Increases chiller capacity
• Overall system efficiency ???
• Decreases storage capacity
• Simplifies system layout
• …..
• Decreases chiller efficiency
• Decreases chiller capacity
Overall system efficiency ???
• Increases storage capacity
•……
• Does not allow chiller shut down!

23. Plumbing - System Curves
A+B A B
A+B A B V A B V A B
Parallel
Serial

25. System balancing AHU1 AHU2 HC1 HC2 100 ft 1000 ft 10 gpm 2 gpm 10 ft
pump
BOILER

26. Pumps Raise pressure and produce flow Main type Centrifugal Example of
Turbine pump
Base mounted
Reading (textbook)
Page
Inline
engineering.com/downloads/cooltools/EDR_De signGuidelines_CoolToolsChilledWater.pdf

27. Curve for Multiple Pumps

28. Changing Pump Speed

29. Primary/Secondary and Tertiary Pumping
Reading Assignment:
Taylor, S., P. Dupont, B. Jones, T. Hartman and M. Hydeman Chilled water plant design guide. San Francisco: Pacific Gas & Electric Company.
engineering.com/downloads/cooltools/EDR_DesignGuidelines_C oolToolsChilledWater.pdf

30. Hydronic systems for district cooling/heating and buildings
Constant-Flow System, Single Chiller, Single Coil
Constant-Flow System, Single Chiller, Multiple Coils
Mixing valve that control
by-pass flow
Major pumping force
is the chiller pump

31. Control of coil temperature
Mixing valve that control the flow through the coil
Flow Variation as a Function of Valve Position
Same pressure
drop like a cooling coil
Major pumping force
is the chiller pump

32. Multiple chiller (or boilers)
Parallel
Serial

33. Primary-Loop Only Variable Speed Flow
Single chiller
Multiple chillers

34. Primary and Secondary Loop Variable Flow Design
Parallel chillers
Serial chillers

35. Large Plant or Building Distribution Systems
Primary/Secondary Loops with Variable Flow and Distributed Pumping

36. Primary/Secondary and Tertiary Pumping

37. Primary Pump Arrangements
Dedicate a pump for each chiller
Provide a common header for the pumps

38. Coil Pumping Strategies
Variable speed pumps vs. Single pas Valve vs. Mixing valves vs. Diverting Valves

39. Impact of plumbing on a cooling coil

40. Plumbing Arrangement in Building’s hydronic systems
Radiators
Baseboard heaters
Fan coil systems

41. Valves Section 5-14 and 6-15 in the textbook Types Butterfly Valves
Ball Valves
Globe Valves
Three way valves

42. Valve Sizing and Flow Coefficient
Cv value:
in liter/hour or….
in Pa
Control Valve Selection For Hydronic Systems
reference:

43. Control Valve Selection For Hydronic Systems
Before DC we tried to do this
Valve authority