1. Thermal Energy Storage
For commercial Buildings

2. Why do we need TES?
In many regions of the world, ventilation system account for up to 60% of buildings electricity demand during peak hours. 
Electricity companies charge separate demand charge per kW of energy consumed per month.
 More electricity consumption at peak, More electricity needs to be produces, More fossil fuels needs to be burned, More CO2

3. How much costly on peak charge can be?

4. Ways to store Energy in Thermal form
Ice Storage
Latent Heat Storage
Low Specific Heat
$/kW
Chilled Water Storage
Sensible Heat Storage
High Specific Heat
57-85 $/kW
Phase Change Material
Under Research

5. Ice Storage Heat exchanger to convert ice in chilled water
Secondary chiller required to super cool the water to make Ice.
Thermal Conductivity is lower than chilled water
Melting of ice is not uniform and depend on internal/externa melt process
Higher heat storing capacity for same volume
Run Chiller on Full load capacity during off peak time and make Ice
Heat exchanger to convert ice in chilled water
Shut-off chiller during peak time and use stored energy

6. Ice Storage Techniques
Secondary coolant freezes the external water into ice during charging period
Same fluid flows in the pipes during discharge period but rejects heat into ice and cools down.
Mostly used.
Ice formation on evaporator surface and periodically dropped
Tank is partially filled with ice & water

7. Chilled Water Storage Charging Discharging
Super chilled water during night
Partially or fully run on stored energy
Use chilled water to serve heat load during peak load
Charging
Discharging

8. Chilled Water Storage Techniques
Series Tank
Gradually increasing water temperature
Flow rate needs to be increased as temperature increase for constant load
Stagnation
More than one valve needs to be opened be opened as the supply temperature increase for constant load
Complex controls strategy
Good because keeps hot and cold water separate by thermocline layer
Easy control strategy

9. Case Study Building Type: Education
Area: 240,277 m2 out of that 37% conditioned
Peak load 2276 TR
Mechanical Chiller capacity 800TR
Partially chilled water & chiller at the same time operation
Results
Annual benefit: $188143
Payback period: 1.8 year

10. Is this Practical?
Energy Modelling Approach

11. Office Building Energy Model
Area: 20,000 sq ft with 100 people
Building Operation time : 9AM to 5 PM
Location: Chicago(No demand charge) v/s Austin
Heating & Cooling Energy source: Electricity
Construction: ASHRAE 90.1
Equipment efficiency: ASHRAE 90.1

12. Throughout year Energy Consumption (kWh)

13. Summer Cooling Energy Demand (kW)
Chicago
Austin

14. Energy Rates
ComEd (Chicago)
($)
Austin Energy (Austin)
Off-peak energy charge
/kWh
Jan-June & Sept-Dec
(0-10 kWh) ( kWh) (>300 kWh)
June-Sept
On-peak energy charge
0.0619/kWh
Demand charge -
12.44 ( kW) 14.65(>300kW)
Austin: Chiller peak kW electricity consumption in range 5-32kW with 32 kW Peak demand in July & August
Chicago: Chiller peak kW electricity consumption in range kW with 27.4 kW Peak demand in July

15. Payback Analysis Storage capacity Number of Hours
Chilled water Storage Cost ($)
Utility peak energy rate ($/kWh)
Utility peak demand rate ($/kW)
Demand Charge ($)
After Installing Storage Demand Charge ($)
Demand Charge Saving different ($)
Energy savings (30 days) ($)
Total Savings (30 days) ($)
Payback period Months
Chicago 20 3
$900.00
0.0619
0.00
111.42 8 2
$600.00
74.28
Austin
12.44
398.08
149.28
248.80
83.29
332.09
55.52
304.32
Installation Cost $15/kWh from Hasnain, S. M. Review on sustainable thermal energy storage technologies, Part II: cool thermal storage. Energy Conversion and Management 39,

16. Evaluate current TES cost in region
Run Energy Model
Know utility rates
Evaluate current TES cost in region
Find optimum point
Conclusion
Both locations, Chicago & Austin showed <10 months payback period (when system is at peak)
Installation/Maintenance cost may vary based on location
It is recommended to evaluate energy storage payback period for a project

17. Reference:
Lizana, J., Chacartegui, R., Barrios-Padura, A. & Manuel Valverde, J. Advances in thermal energy storage materials and their applications towards zero energy buildings: A critical review. Appl. Energy 203, (2017).
Yau, Y. H. & Rismanchi, B. A review on cool thermal storage technologies and operating strategies. Renewable and Sustainable Energy Reviews 16, (2012).
Hasnain, S. M. Review on sustainable thermal energy storage technologies, Part II: cool thermal storage. Energy Conversion and Management 39, (1998).
Thermal storage. In: ASHRAE handbook. American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta: HVAC Applications; 2007 [chapter 34].
Wu, C. & Tsai, Y. Design of an ice thermal energy storage system for a building of hospitality operation. International Journal of Hospitality Management46, (2015).
Sanaye, S. & Shirazi, A. Thermo-economic optimization of an ice thermal energy storage system for air- conditioning applications. Energy and Buildings60, (2013).
Ahrinet.org. (2017). HVACR Equipment/Components. Available at:
Trane Trace 700 software

18. Questions?