1. Announcement EWRE Seminar Series Presents:
Monday, April 24, 2017, 12:00 – 1:00 pm
CPE 2.212
How Much Carbon Dioxide Do People Emit and Who Cares?”
Andrew Persily
National Institute of Standards and Technology
100 Bureau Drive, MS8600
Gaithersburg, Maryland USA

2. Lecture Objectives: Learn about Mat lab equation solving
Discuss Take Home Exam
Finish with Absorption Cooling Systems
Learn about thermal storage systems

3. MATLAB BASICS
Hongwan Li

4. Goals

5. Import data from Excel
From text

6. Define variables and time step

7. Loop
for loop to repeat specified number of times

8. Solve equations

9. fsolve Nonlinear system solver Solves a problem specified by F(x) = 0
x is a vector or a matrix
Syntax:
x = fsolve(fun,x0)
starts at x0 and tries to solve the equations fun(x) = 0, an array of zeros
x = fsolve(fun,x0,options)
solves the equations with the optimization options specified in options
[x,fval] = fsolve(fun,x0)
returns the value of the objective function fun at the solution x

10. Solve equations Options: Display-'off' or 'none' displays no output.
'iter' displays output at each iteration, and gives the default exit message.
MaxFunEvals- Maximum number of function evaluations allowed, a positive integer.
TolFun-The termination tolerance for the function value. The default value is 1.e-4.

11. Solve equations
aw+bv+cz=13
5aw-6cv=20
w-2bv-7z=18
A*X=B

12. Export data to excel

13. Plot

14. Plot

16. LiBr-H2O Systems

17. LiBr-H2O Systems

18. Twine vessel LiBr-H2O Systems

19. Useful information about LiBr absorption chiller
Practical Tips for Implementation of absorption chillers
Identify and resolve any pre-existing problems with a cooling system, heat rejection system, water treatment etc, before installing an absorption chiller, or it may be unfairly blamed.
Select an absorption chiller for full load operation (by the incorporation of thermal stores if necessary) as COP will drop by up to 33% at part-load.
Consider VSD control of absorbent pump to improve the COP at low load.
Consider access and floor-loading (typical 2 MW Double-effect steam chiller 12.5 tons empty, 16.7 tones operating).
Ensure ambient of temperature of at least 5°C in chiller room to prevent crystallization.

20. System with no pump (Platen-Munter system)
H2O-NH3 + hydrogen

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

22. 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!

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

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

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

26. 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

27. 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 ?

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

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

30. Fluid Flow Rate and Freeze ΔT

31. Impact on Chiller Efficiency

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

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

34. Construction and benefits
Active
Passive (wall)

35. Stratified chilled water tanks

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

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

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

39. 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!