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Proceedings: Building Simulation 2007 

- 529 - 

METHODOLOGY FOR OPTIMIZING THE OPERATION OF HEATING/COOLING 
PLANTS WITH MULTI-HEAT SOURCE EQUIPMENTS USING SIMULATION 

 
Fulin Wang1*, Harunori Yoshida1, Eikichi Ono1 and Hirotake Shingu1 

 
1Department of Urban and Environmental Engineering, Kyoto University,  

Kyoto 615-8540, Japan 
* fuwang@archi.kyoto-u.ac.jp, +81-75-383-3274
 

ABSTRACT  
A methodology for optimizing the operation of 
heating/cooling plants with multi-heat source 
equipments is proposed. The methodology decides 
the optimal combination of the running of multiple 
heat source equipments to minimize the energy 
consumption of a heating/cooling plant. The optimal 
running combination is decided automatically using 
MATLAB® Stateflow® tool corresponding to cooling 
and heating loads. The energy consumption at 
different running combination is simulated using 
MATLAB® Simulink® tool.  A case study is 
introduced to demonstrate the methodology. An 
actual district heating/cooling plant located in Osaka 
Japan, which consist of two absorption chiller/heaters, 
one centrifugal chiller, one ice chiller, and two 
air-source heat pumps, is studied to find the optimal 
operation combination of the heat source equipments,.  
The optimal running combination found by this 
method can reduce primary energy consumption by 
19.7%, running cost by 12.8%, and carbon dioxide 
emission by 29.6%, compared to present operation. 

KEYWORDS 
Optimization, Energy consumption, Running cost, 
Heating/cooling plant, Running combination 

INTRODUCTION 
Energy and Environment are the most important 
issues in this new century. The comprehensive study 
on energy efficiency started since the Energy Crisis 
caused by the Middle East War in 1973 to 1974. The 
urgent need for oil security management and energy 
policy co-operation led to the establishment of 
International Energy Agency (IEA)  (Scott 1994). In 
the field of building energy conservation, the idea 
that commissioning is a viable method to help ensure 
good performance of buildings and their Energy 
Conservation Measures (ECM) was gradually 
conceived since 1989, because some analyses on the 
data from the buildings participating in the energy 
conservation program revealed that many of the 
installed energy efficiency measures were not 
performing as expected (Bonneville Power 
Administration, 1992). Building commissioning is 
the process of ensuring that systems are designed, 
installed, functionally tested, and capable of being 
operated and maintained to perform in conformity 
with the design intent (ASHRAE, 1996). 

The concept of commissioning is being gradually 
refined since its birth. Now commissioning is not 
only to verify whether building systems are in 
conformity with design intent, but also to verify and 
improve the design itself. Especially during 
operational phase, one of the main commissioning 
jobs is to optimize the operation of building systems. 
The optimization of heating/cooling plant, which is 
the heart and main energy consuming part, is 
considered to be so important that many researches 
have been conducted on the operation of 
heating/cooling plants. Celuch (2001) analyzed the 
issues of energy efficiency, cost, and operation on 
upgrading an actual central chiller water plant. 
Modeling of an actual cooling plant is also studied 
and the model is used for simulation and fault 
detection during the commissioning for a 
heating/cooling plant (Georges and Lebrun 2004). A 
program for power generation optimization is 
developed by SEGA (Anon). Zhang et al. (2000) used 
SEGA’s Energy Optimization Program (EOP) to 
analyze the operation of a cogeneration power plant 
and found the optimal operation can save total costs 
by 10.4% compared to the original operation. 
However, research on the method for optimizing the 
operational combination of heat source equipments in 
central heating/cooling plants for buildings can 
seldom be found. Corresponding to a requirement of 
heating/cooling, many different heating cooling 
source combinations can satisfy the requirement. It is 
necessary to select an optimal combination for the 
purpose of ensuring energy efficiency. However there 
are so many different combinations of multiple 
heating/cooling source equipments that it is difficult, 
even impossible, to check the performance of all the 
possible combinations experimentally on an actual 
plant. Therefore it is necessary to find a method to 
automatically check the performance of all possible 
combinations and determine the optimal combination. 
Simulation is considered to be a powerful tool to 
automatically check the performance of a building 
and its systems (Wang and Yoshida, 2003). This 
paper focuses on developing a method for 
determining optimal running combination of multiple 
heating/cooling equipments using simulation. For the 
purpose of validating the method proposed, then the 
method is applied to an actual district heating/cooling 
plant located in Osaka Japan, which consist of two 
absorption chiller/heaters, one centrifugal chiller, one