This document analyzes centralized cooling systems for an urban community of 10,000 people. It evaluates three cases: a decentralized system (Case 1), a centralized system with electric and absorption chillers (Case 2), and Case 2 with added thermal energy storage (Case 3). Case 1 has an NPV of $28 million. Case 2 has lower operational costs but higher initial costs, resulting in an NPV of -$781 million. Case 3 further reduces costs but has a similar NPV of -$783 million compared to Case 2. The analysis is based on cooling load models, electricity prices, and optimization of the systems over a 20-year period.

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Smart Grid Analysis of Centralized Cooling
for an Urban Community
Objectives
Introduction
Perform a techno-economic analysis of
a centralized cooling system for
an urban community of 10,000 people
in the context of day-ahead electricity prices.
Cooling Load
Figure 1 – Decentralized Cooling System.
Figure 2 – Centralized Cooling System.
The cooling load was obtained by adapting Cooling Load
Temperature Difference (CLTD) method proposed by the
ASHRAE to our case.
The electrical power due the cooling system:
Figure 3 – Cooling Load model
Figure 4 – Cooling load ( 𝑄 𝐾
𝐿
)
Then, the hourly cost and operational cost for case 1 are:
Figure 6 – Day ahead electricity price PJM (2012).
Figure 7 – Energy cost per hour.
Figure 5 – Electrical Chiller
𝐶𝑂𝑃𝐸𝐶 =
𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦
𝐼𝑛𝑝𝑢𝑡 𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦
= 1.14 tons/kW
Net Present Value
Vieira, F.L; Henriques, J.M.M; Soares, L.S; Rezende, L.L; Martins, M.S; de Melo Neto, R; D. J.Chmielewski
Results for Case 1:
Initial Costs: $14 million
Operational Costs: $14 million
NPV: $28 million
𝑃𝑘
𝐸𝐶
=
𝑄 𝐾
𝐿
𝐶𝑂𝑃 𝐸𝐶
OC =
𝑘=0
𝑛
𝑐 𝑘
𝑒
𝑃𝑘
𝐸𝐶
Decentralized Chiller
Case 1
Planning period ( n = 20 years ), Interest rate ( i = 7% )
NPV = IC + PV PV = OC
(1+𝑖) 𝑛 −1
𝑖(1+𝑖) 𝑛

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Smart Grid Analysis of Centralized Cooling
for an Urban Community
Vieira, F.L; Henriques, J.M.M; Soares, L.S; Rezende, L.L; Martins, M.S; de Melo Neto, R; D. J.Chmielewski
Figure 9 – Power Plant process load diagram.
Figure 10 – Case 2 diagram: Plant + Absorption Chiller + Electrical
Chiller
Centralized System – Background
Figure 8 – Electrical and Absorption Chiller diagrams.
Case 2
Figure 11 –Results of case 2..
𝑂𝐶 = min
𝑘=0
𝑛
𝑐 𝑘
𝑒
𝐶𝑂𝑃𝐸𝐶
𝑄 𝑘
𝐸𝐶
− 𝑐 𝑘
𝑒
𝑃𝑘
𝐺
+ 𝑐 𝑘
𝑁𝐺
𝜈 𝑘
𝑓
𝑄 𝑘
𝐸𝐶
+ 𝑄 𝑘
𝐴𝐶
= 𝑄 𝑘
𝐿
−𝑄 𝑘
𝐴𝐶
.
𝜂 𝑅
𝐶𝑂𝑃𝐴𝐶
+ 𝜈 𝑘
𝑓
. 𝜂 𝑃 − 𝑃𝑘
𝐺
= 0
0 ≤ 𝑄 𝑘
𝐸𝐶
≤ 𝑄 𝑀𝐴𝑋
𝐸𝐶
0 ≤ 𝑄 𝑘
𝐴𝐶
≤ 𝑄 𝑀𝐴𝑋
𝐴𝐶
0 ≤ 𝜈 𝑘
𝑓
≤ 𝜈 𝑀𝐴𝑋
𝑓
0 ≤ 𝑃𝑘
𝐺
≤ 𝑃 𝑀𝐴𝑋
𝐺

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Smart Grid Analysis of Centralized Cooling
for an Urban Community
Thermal Energy Storage Preliminary Results
Figure 13 – Case 3 diagram: Plant + Absorption Chiller + Electrical
Chiller + Thermal Energy Storage
Figure 14 – Results of case 3
Case 2:
Initial Cost: $ 299 million
o Absorption Chiller: $7.4 million
o Electric Chiller: $4.2 million
o Distribution Network: $80 million
o Power Plant: $207 million
Operational Cost: -$1.08 billion
o Profit of the Power Plant: $102 million/year
NPV: - $781 million
Case 3:
Initial Cost: $ 307 million
o Thermal Energy Storage: $ 8 million
Operational Cost: -$1.09 billion
o Profit of the Power Plant: $103 million/year
NPV: - $783 million
References
1. American Society of Heating,Refrigerating and Air-Conditioning Engineers, and
Knovel (Firm). 1997. 1997 ASHRAE handbook: Fundamentals. SI ed. Atlanta, GA:
American Society of Heating, Refrigeration and Air-Conditioning Engineers
2. Feng, J., Brown, A., O’Brien, D., & Chmielewski, D. J. (2015). Smart grid coordination of a
chemical processing plant. Chemical Engineering Science
3. Roth, K., Zogg, R., & Brodrick, J. (2006). Cool thermal energy storage. ASHRAE journal,
48(9), 94-96
4. Newnan, D. G., Lavelle, J. P., Eschenbach, T. G. (1991). Engineering Economic Analysis. 12th
edition
5. Black, J. Cost and performance baseline for fossil energy plants. US Department of Energy.
September, 2013
6. PJM Data Miner - Energy Pricing. (n.d.). Retrieved June , 2015, from
https://dataminer.pjm.com/dataminerui/pages/public/energypricing.jsf
7. NCDC: Quality Controlled Local Climatological Data - Chicago Illinois. (n.d.). Retrieved
June, 2015, from http://www.ncdc.noaa.gov/qclcd/QCLCD?prior=N
8. Illinois Natural Gas Prices. (n.d.). Retrieved June, 2015, from
http://www.eia.gov/dnav/ng/ng_pri_sum_dcu_SIL_m.htm
Vieira, F.L; Henriques, J.M.M; Soares, L.S; Rezende, L.L; Martins, M.S; de Melo Neto, R; D. J.Chmielewski
Case 3
Figure 12 – Thermal Energy Storage
𝑄 𝑘
𝐸𝐶
+ 𝑄 𝑘
𝐴𝐶
= 𝑄 𝑘
𝐿
𝑄 𝑘
𝐸𝐶
+ 𝑄 𝑘
𝐴𝐶
- 𝐸 𝑘 + 𝐸 𝑘+1= 𝑄 𝑘
𝐿
- 𝐸 𝑀𝐴𝑋 ≤ 𝐸 𝑘 ≤ 0
Acknowledgements