The analysis of economic feasibility for adding a cool
storage facility to shift electric demand to off-peak hours for a
large industrial facility is presented. DOE-2 is used to generate
the necessary cooling load profiles for the analysis. The
aggregation of building information for predicting central plant
behavior at the site is discussed. The dollar benefits and costs for
the project are favorable, providing a payback in the
neighborhood of 4 to 5 years

Ballard, R. H.

Fazzolari, R.

Mascorro, J. A.

Texas A&M University

COOL STORAGE ECONOMIC FEASIBILITY ANALYSIS 
FOR A LARGE INDU!XRIAL FACILITY 
ROCCO FAZZOLARI JOSE A. MASCORRO R.H. BALLARD 
Associate Professor Graduate Assistant Energy Manager 
Nuclear & Energy Eng. Nuclear & Energy Eng. McDonnell Douglas 
University of Arizona University of Arizona Helicopter Co. 
Tucson, Arizona. Tucson, Arizona. Mesa. Arizona. 
ABSTRACT 
The analysis of economic feasibility for adding a cool 
storage facility to shift electric demand to off-peak hours for a 
large industrial facility is presented. DOE-2 is used to generate 
the necessary cooling load profiles for the analysis. The 
aggregation of building information for predicting central plant 
behavior at the site is discussed. The dollar benefits and costs for 
the project are favorable, providing a payback in the 
neighborhood of 4 to 5 years. 
INTRODUCTION 
The rationale for cold storage is primarily for electric 
load leveling by shifting the air-conditioning power requirements 
from the peak time hours to off-pak hours, normally at night. 
The utility-in this case Salt River Project (SRP)--has an interest 
in electric load leveling because it postpones or reduces the need 
for odding additional power plants. The utility can provide 
incentives to its customers to install thermal storage by 
contributing to the capital costs and by means of time-of-day 
electric rates which offer cheaper electric charges during the off- 
peak hours. 
Thh paper describes the plant modeling and analysis 
procedures for determining the economic feasibility of using 
thermal storage at McDonnell Douglas Helicopter CO. (MDH) in 
Mesa, Arimna [I]. MDH is a large assembly plant consisting of 
eleven air conditioned buildings totalling 2,000.000 square feet of 
diversified activities. The site has a central chilled water plant 
and distribution system. 
COMPUTER MODEL OF THE FACILITIES 
In order to assess the potential benefits of thermal 
storage, it was desirable to have reprssentative hourly electric 
demand profiles for the central chiller plant operations 
throughout the year. Historical measured data for the chillers of 
the central plant were not available. A computer energy use 
model of the facilities was constructed with a microcomputer 
version of DOE-2 (v.2.1~) [2]. 
The program, however, is designed to handle a single- 
building model; it was not specifically designed to handle a multi- 
building complex. Some creatiw manipulation of the input data 
was required in order to reduce the computational time of doing 
eleven separate building3 on an IBM AT personal computer. 
Thus, a simplified model of the site consisting of four 
buildings was proposed given the limitations of both the DOE-2 
program and our hardware. The methodology used to construct 
these representative buildings was as follows. An informational 
data base on each building was generated using design information 
and as-built plans for the recently constructed facility. The 
buildings were classified by the following categories: 
a) VAV buildings. single story 
b) VAV buildings, multi-story 
c) Constant-volume building. single story 
d) Constant-volume buildings, multi-story. 
The data fields describing each building category (i.e. walls, 
windows, roofs, people, etc.) were then aggregated into the four 
representative building model3 for DOE-2. The model3 preserved 
the exterior surface exposures and the interior volumes. The 
internal energy use schedules in terms of time and intensity of the 
activities are important to the load profile construction--especially 
for industrial operations. 
The only available data to validate this model were s 
recent monthly electric profiles recorded by SRP. Specifically 
electric profile for June was used to calibrate the computer m 
We obtained very good agreement for all of the other mont 
choosing random days without making any adjustments to t 
data. Figure 1 shows comparison of a real and computed pro 
for a typical day of March and June. Since the electric prof 
from month to month reflect the impact of the varying weatl 
conditions on the chiller plant operation, we were satisfied tl 
DOE-2 was satisfactorily indicating the site cooling loads a1 
electricity demands; Figures 2 and 3 shows the cooling load 
same days of March and June. 
Fig. I ELECTRIC DEMAND PROFILE FOR 
TYPICAL DAY OF MARCH 
ESL-HH-88-09-02
Proceedings of the Fifth Symposium on Improving Building Systems in Hot and Humid Climates, Houston, TX, September 12-14, 1988 
- - 
Fig. 2 ' ELECTRIC DEMAND PROFILE FOR 
TYPICAL DAY OF JUNE 
1  3 5 7 9  11 13 1 5 1 7 1 9  21 23 
2 4  6 8  10 12 14 16 18 iU 22 24 
HCUR CF MY 
Fig. 3 COMPUTED CHILLERS LOADS 
PROFILES FOR TYPICAL MARCH & JUNE DAYS 
FINANCIAL FEASIBILITY STUDIES 
Although W E - 2  includes a storage sub-model, we chose 
not to do complete simulation runs initially. Instead, typical 
monthly cooling profiles for one day were introduced into a 
spreadsheet and analyzed. This approach saved much 
computational time and allowed us more insights as to the impact 
of various system parameters and the rate schedule. One key 
parameter that impacts the economics of thermal storage is the 
chiller plant efficiency, which includes the chillers pumps and 
cooling tower. The storage capacity is an important cost driver 
and a key factor in establishing the monthly energy and demand 
shift from the peak hours. 
Financial costlbenefit studies have been on-going for 
more than a year. The W E - 2  studies were expanded to include 
the calculation of the utility bilk once the design parameters were 
fixed. The results of these more recent studies are presented here. 
The following conditions apply to the final study: 
Storage media - Eutectic salt 
Storage capacity - 10000 ton-hrs 
Chiller efficiency - 0.65 kW/ton 
Primary pumps & cooling towers - 0.2 kW/ton 
Secondary pumps - 0.04 kW/ton 
Applicable SRP rates - E39 
The analysis was based on hourly simulation8 for one 
week in each month. The electric profiles and utility bills wem 
computed by the W E - 2  program with and without storage. A 
minimum of 16 simulation runs (two runs per building per season 
with and without storage tank) were required for this more 
comprehensive analysis in order to accommodate a summer and 
winter rate. The weekly basis reduces the uncertainties associated 
with weekend operations and improves the statistical accuracy. 
Using the plant model in DOE-2 simulates more realistic system 
efficiency behavior and the effects of night time chiller operation. 
BENEFITS 
The benefits to MDH of having the storage system ere, 
financial in nature and due to the reduced energy and demand 
charges resulting from shifting the cooling load from the on end 
off peak hours. With storage, the chiller operations will be 
partially reduced or completely eliminated during the on peak 
hours. The anticipated saving8 vary from month to month 
because of climatic variations and because different winter and 
summer rates are applicable. Figures 4 and 5 show the monthly 
reduction in demand and energy charges as predicted by the 
simulations. The yearly benefits are estimated to be $152,000 for 
the connected load in 1987. Since both the connected load and the 
utility rates, however, are expected to increase in the future, the 
savings estimate are a conservative forecast. 
Fig. 4 ON-PEAK DEMAND COMPARISON 
FOR MDFl - MESA SITE (DOE-2.IC) 
ESL-HH-88-09-02
Proceedings of the Fifth Symposium on Improving Building Systems in Hot and Humid Climates, Houston, TX, September 12-14, 1988 
JAN MAR MAY JUL SEP NOV 
m3 PR JUN WG OCT DU: 
'Fig. 5 ELECTRIC CHARGES COMPARISON 
FOR MDH - MESA SITE (DOE-2.1C) 
The installed cost of the eutectic salt tank, with a phase 
change at 47 F is expected to be approximately $92 per ton-hr. 
The pump5 and associated piping are estimated to cost $62,000. 
A financial incentive contribution is to be provided by 
SRP which depends on the magnitude of the demand shifted to 
the off peak hours. The current program allows $250/kw up to 
300 kw and $1 I5/kw thereafter. 
The demand shift will be affected by the tank discharge 
rate during the 5 peak hours. Considering that the cooling load at 
MDH drops off after 400 p.m.. the optimal discharge schedule, in 
terms of the rates, would be to base load the chillers during on 
peak hours to the lowest level permitted by the storage capacity 
i.e., the tank would be discharged according to the load. The 
optimum scheme is shown by Figures 6 and 7: a shift of 2200 kw 
is pwible with this strategy. 
At the other extreme, the tank would be unloaded 
uniformly at 2000 tons/hr which corresponds a 1700 kw shift, A 
constant shift may be mom desirable for SRP's planning strategies 
of deferring new generation capacity; however, the motivating 
realities of the rates do not dictate this scheme operation to the 
customer. Furthermore. MDH is shifting load by its current 
schedule of the working hours at the plant. 
CONCLUSIONS 
The payback to MDH will be affected by a number of 
facton--the initial tank cost, the incentive provided by SRP, the 
chiller plant efficiency and the capacity of the storage. In 
addition free cooling (using cooling towers instead of chillers) can 
enhance the savings to MDH by providing additional night cooling 
hours. Free cooling can increase the yearly dollar benefits by as 
much as 10 percsnt [I]. The payback estimates for this project 
range between 4 and 5 years considering the benefits of free 
cooling, 
HOUR OF M DAY 
Fig 6 COOLING LOAD FOR MDH - MESA 
JUL 17, 1988 (DOE-2.IC) - 2200 kW SHIFT 
HOUR OF ME DAY 
Fig. 7 ELECTRIC PROFILE FOR MDH - MESA 
JUL 17, 1988 (WE-2.IC) - 2200 kW SHIFT 
ACKNOWLEDGEMENTS 
We wish to express our appreciation to McDonnell 
Douglas Helicopter Company and Salt River Project for 
sponsoring this study. 
REFERENCES 
1. Famlari ,  R., Mascorro, J.A.. "Cool Storage 
Feasibility Study," Nuclear & Energy Engineering Department. 
University of Arizona. November 1987. 
2. "Micro- W E 2  Version 2. IC." ACROSOFT 
International, Inc.. February, 1987. 
ESL-HH-88-09-02
Proceedings of the Fifth Symposium on Improving Building Systems in Hot and Humid Climates, Houston, TX, September 12-14, 1988 


English

Cool Storage Economic Feasibility Analysis for a Large Industrial Facility

Texas A&amp;M Repository

COOL STORAGE ECONOMIC FEASIBILITY ANALYSIS FOR A LARGE INDU!XRIAL FACILITY ROCCO FAZZOLARI JOSE A. MASCORRO R.H. BALLARD Associate Professor Graduate Assistant Energy Manager Nuclear & Energy Eng. Nuclear & Energy Eng. McDonnell Douglas University of Arizona University of Arizona Helicopter Co. Tucson, Arizona. Tucson, Arizona. Mesa. Arizona. ABSTRACT The analysis of economic feasibility for adding a cool storage facility to shift electric demand to off-peak hours for a large industrial facility is presented. DOE-2 is used to generate the necessary cooling load profiles for the analysis. The aggregation of building information for predicting central plant behavior at the site is discussed. The dollar benefits and costs for the project are favorable, providing a payback in the neighborhood of 4 to 5 years. INTRODUCTION The rationale for cold storage is primarily for electric load leveling by shifting the air-conditioning power requirements from the peak time hours to off-pak hours, normally at night. The utility-in this case Salt River Project (SRP)--has an interest in electric load leveling because it postpones or reduces the need for odding additional power plants. The utility can provide incentives to its customers to install thermal storage by contributing to the capital costs and by means of time-of-day electric rates which offer cheaper electric charges during the off- peak hours. Thh paper describes the plant modeling and analysis procedures for determining the economic feasibility of using thermal storage at McDonnell Douglas Helicopter CO. (MDH) in Mesa, Arimna [I]. MDH is a large assembly plant consisting of eleven air conditioned buildings totalling 2,000.000 square feet of diversified activities. The site has a central chilled water plant and distribution system. COMPUTER MODEL OF THE FACILITIES In order to assess the potential benefits of thermal storage, it was desirable to have reprssentative hourly electric demand profiles for the central chiller plant operations throughout the year. Historical measured data for the chillers of the central plant were not available. A computer energy use model of the facilities was constructed with a microcomputer version of DOE-2 (v.2.1~) [2]. The program, however, is designed to handle a single- building model; it was not specifically designed to handle a multi- building complex. Some creatiw manipulation of the input data was required in order to reduce the computational time of doing eleven separate building3 on an IBM AT personal computer. Thus, a simplified model of the site consisting of four buildings was proposed given the limitations of both the DOE-2 program and our hardware. The methodology used to construct these representative buildings was as follows. An informational data base on each building was generated using design information and as-built plans for the recently constructed facility. The buildings were classified by the following categories: a) VAV buildings. single story b) VAV buildings, multi-story c) Constant-volume building. single story d) Constant-volume buildings, multi-story. The data fields describing each building category (i.e. walls, windows, roofs, people, etc.) were then aggregated into the four representative building model3 for DOE-2. The model3 preserved the exterior surface exposures and the interior volumes. The internal energy use schedules in terms of time and intensity of the activities are important to the load profile construction--especially for industrial operations. The only available data to validate this model were s recent monthly electric profiles recorded by SRP. Specifically electric profile for June was used to calibrate the computer m We obtained very good agreement for all of the other mont choosing random days without making any adjustments to t data. Figure 1 shows comparison of a real and computed pro for a typical day of March and June. Since the electric prof from month to month reflect the impact of the varying weatl conditions on the chiller plant operation, we were satisfied tl DOE-2 was satisfactorily indicating the site cooling loads a1 electricity demands; Figures 2 and 3 shows the cooling load same days of March and June. Fig. I ELECTRIC DEMAND PROFILE FOR TYPICAL DAY OF MARCH ESL-HH-88-09-02Proceedings of the Fifth Symposium on Improving Building Systems in Hot and Humid Climates, Houston, TX, September 12-14, 1988 - - Fig. 2 ' ELECTRIC DEMAND PROFILE FOR TYPICAL DAY OF JUNE 1  3 5 7 9  11 13 1 5 1 7 1 9  21 23 2 4  6 8  10 12 14 16 18 iU 22 24 HCUR CF MY Fig. 3 COMPUTED CHILLERS LOADS PROFILES FOR TYPICAL MARCH & JUNE DAYS FINANCIAL FEASIBILITY STUDIES Although W E - 2  includes a storage sub-model, we chose not to do complete simulation runs initially. Instead, typical monthly cooling profiles for one day were introduced into a spreadsheet and analyzed. This approach saved much computational time and allowed us more insights as to the impact of various system parameters and the rate schedule. One key parameter that impacts the economics of thermal storage is the chiller plant efficiency, which includes the chillers pumps and cooling tower. The storage capacity is an important cost driver and a key factor in establishing the monthly energy and demand shift from the peak hours. Financial costlbenefit studies have been on-going for more than a year. The W E - 2  studies were expanded to include the calculation of the utility bilk once the design parameters were fixed. The results of these more recent studies are presented here. The following conditions apply to the final study: Storage media - Eutectic salt Storage capacity - 10000 ton-hrs Chiller efficiency - 0.65 kW/ton Primary pumps & cooling towers - 0.2 kW/ton Secondary pumps - 0.04 kW/ton Applicable SRP rates - E39 The analysis was based on hourly simulation8 for one week in each month. The electric profiles and utility bills wem computed by the W E - 2  program with and without storage. A minimum of 16 simulation runs (two runs per building per season with and without storage tank) were required for this more comprehensive analysis in order to accommodate a summer and winter rate. The weekly basis reduces the uncertainties associated with weekend operations and improves the statistical accuracy. Using the plant model in DOE-2 simulates more realistic system efficiency behavior and the effects of night time chiller operation. BENEFITS The benefits to MDH of having the storage system ere, financial in nature and due to the reduced energy and demand charges resulting from shifting the cooling load from the on end off peak hours. With storage, the chiller operations will be partially reduced or completely eliminated during the on peak hours. The anticipated saving8 vary from month to month because of climatic variations and because different winter and summer rates are applicable. Figures 4 and 5 show the monthly reduction in demand and energy charges as predicted by the simulations. The yearly benefits are estimated to be $152,000 for the connected load in 1987. Since both the connected load and the utility rates, however, are expected to increase in the future, the savings estimate are a conservative forecast. Fig. 4 ON-PEAK DEMAND COMPARISON FOR MDFl - MESA SITE (DOE-2.IC) ESL-HH-88-09-02Proceedings of the Fifth Symposium on Improving Building Systems in Hot and Humid Climates, Houston, TX, September 12-14, 1988 JAN MAR MAY JUL SEP NOV m3 PR JUN WG OCT DU: 'Fig. 5 ELECTRIC CHARGES COMPARISON FOR MDH - MESA SITE (DOE-2.1C) The installed cost of the eutectic salt tank, with a phase change at 47 F is expected to be approximately $92 per ton-hr. The pump5 and associated piping are estimated to cost $62,000. A financial incentive contribution is to be provided by SRP which depends on the magnitude of the demand shifted to the off peak hours. The current program allows $250/kw up to 300 kw and $1 I5/kw thereafter. The demand shift will be affected by the tank discharge rate during the 5 peak hours. Considering that the cooling load at MDH drops off after 400 p.m.. the optimal discharge schedule, in terms of the rates, would be to base load the chillers during on peak hours to the lowest level permitted by the storage capacity i.e., the tank would be discharged according to the load. The optimum scheme is shown by Figures 6 and 7: a shift of 2200 kw is pwible with this strategy. At the other extreme, the tank would be unloaded uniformly at 2000 tons/hr which corresponds a 1700 kw shift, A constant shift may be mom desirable for SRP's planning strategies of deferring new generation capacity; however, the motivating realities of the rates do not dictate this scheme operation to the customer. Furthermore. MDH is shifting load by its current schedule of the working hours at the plant. CONCLUSIONS The payback to MDH will be affected by a number of facton--the initial tank cost, the incentive provided by SRP, the chiller plant efficiency and the capacity of the storage. In addition free cooling (using cooling towers instead of chillers) can enhance the savings to MDH by providing additional night cooling hours. Free cooling can increase the yearly dollar benefits by as much as 10 percsnt [I]. The payback estimates for this project range between 4 and 5 years considering the benefits of free cooling, HOUR OF M DAY Fig 6 COOLING LOAD FOR MDH - MESA JUL 17, 1988 (DOE-2.IC) - 2200 kW SHIFT HOUR OF ME DAY Fig. 7 ELECTRIC PROFILE FOR MDH - MESA JUL 17, 1988 (WE-2.IC) - 2200 kW SHIFT ACKNOWLEDGEMENTS We wish to express our appreciation to McDonnell Douglas Helicopter Company and Salt River Project for sponsoring this study. REFERENCES 1. Famlari ,  R., Mascorro, J.A.. "Cool Storage Feasibility Study," Nuclear & Energy Engineering Department. University of Arizona. November 1987. 2. "Micro- W E 2  Version 2. IC." ACROSOFT International, Inc.. February, 1987. ESL-HH-88-09-02Proceedings of the Fifth Symposium on Improving Building Systems in Hot and Humid Climates, Houston, TX, September 12-14, 1988 

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Cool Storage Economic Feasibility Analysis for a Large Industrial Facility

Abstract

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Texas A&M University

Texas A&M Repository

Cool Storage Economic Feasibility Analysis for a Large Industrial Facility

Abstract

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Full text

Available Versions

Texas A&M University

Texas A&amp;M Repository

Texas A&M Repository