Development of an Optimal Start Control Strategy for a Variable Refrigerant Flow (VRF) System

Yusung Lee,Woohyun Kim

doi:10.3390/en14020271

Abstract

In this study, an optimal control strategy for the variable refrigerant flow (VRF) system is developed using a data-driven model and on-site data to save the building energy. Three data-based models are developed to improve the on-site applicability. The presented models are used to determine the length of time required to bring each zone from its current temperature to the set point. The existing data are used to evaluate and validated the predictive performance of three data-based models. Experiments are conducted using three outdoor units and eight indoor units on site. The experimental test is performed to validate the performance of proposed optimal control by comparing between conventional and optimal control methods. Then, the ability to save energy wasted for maintaining temperature after temperature reaches the set points is evaluated through the comparison of energy usage. Given these results, 30.5% of energy is saved on average for each outdoor unit and the proposed optimal control strategy makes the zones comfortable.

Highlights

According to the U.S Department of Energy (DOE, 2010), 40% of residential energy use and 30% of commercial building energy use are associated with the process of heating, ventilation and air conditioning (HVAC) and a variable refrigerant flow (VRF)
To overcome the above-mentioned shortcomings, in this paper, we propose an optimal start control methodology based on a data-based models for modelling the building thermal dynamics
The control rules proposed in this study suggest maximum and minimum operating boundaries

Summary

Introduction

The buildings have great potential for energy savings and peak savings Several studies, including those of Liu et al and Mills, have demonstrated that scalable and costeffective intelligent building systems have an energy-saving potential of greater than 30%, in which optimal control and automated diagnosis are included [1,2]. The control system changes the set points when the building is not occupied; this concept is referred to as the night setback. The heating/cooling system is operated before the start of the day when a night setback is applied and it remains operational long enough for the zone temperature to reach the set points before the time at the beginning of occupancy [12]

Methods

Results

Conclusion