Lecture Objectives:

1
Lecture Objectives

• Finish boilers and furnaces
• Start with thermal storage systems

2
Thermal storage for adjustment production to
consumption
We need a thermal storage somewhere in this
system !
3
Thermal storage

• Store heat
• 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!

4
On-Peak and Off-Peak Periods
This profile depends on the type of building(s) !
5
Chilled water tank
Use of stored cooling energy
Store
Use
6
Which one is better ?

• Depends on what you
• want to achieve
• Peak electric power reduction
• Capacity reduction
• ..

7
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

8
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 ?
9
Ice Storage Tank
Many issues ! . As freezing progresses progress
the ice becomes thicker and significantly
impedes heat transfer
10
Open Ice Storage Tank
Also issues ! ..
11
Fluid Flow Rate and Freeze ?T
12
Impact on Chiller Efficiency
13
PCMs
A. Sharma et al. / Renewable and Sustainable
Energy Reviews 13 (2009) http//www.docunator.com
/bigdata/1/1367142535_c566e7d75e/reviewexample2.pd
f
14
Other latent heat thermal storage systems
(research is ongoing)
15
Construction and benefits
Active
Passive (wall)
16
Stratified chilled water tanks
17
Temperature and dynamics
Temperature at outlet during the changing cycle
of the tanks
18
Stratified chilled water tanksdiffuser geometry
Challenge Pull large amount of energy
without disturbing stratification
19
Modeling
Write energy and mass balancer equation for each
section
20
Installation of thermal storage system
Downstream
Upstream
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!
21
Mixing vs Diverting Valves
22
Plumbing arrangement in primary system
Primarily-Only
Primarily Secondary
23
Plumbing arrangement in buildings (secondary
systems)