Equivalent Electric and Heat-Pump Water Heater Models for Aggregated Community-Level Demand Response Virtual Power Plant Controls

Huangjie Gong,Brian T Branecky,Oluwaseun M Akeyo,Tim Rooney,Dan M Ionel

doi:10.1109/access.2021.3119581

Abstract

Advanced control techniques may be used to establish a virtual power plant to regulate the operation of electric water heaters, which may be regarded as a “uni-directional battery” and a major component of a hybrid residential energy storage system. In order to estimate the potential of regulating water heaters at the aggregated level, factors including user behavior, number of water heaters, and types of water heaters must be considered. This study develops generic water heater load curves based on the data retrieved from large experimental projects for resistive electric water heaters (EWHs) and heat pump water heaters (HPWHs). A community-level digital twin with scalability has been developed to capture the aggregated hot water flow and average hot temperature in the tank. The results in this paper also include the “energy take” in line with the CTA-2045 standard and Energy Star specification. The data from the experiments demonstrated that changing from an EWH to an HPWH reduces electricity usage by approximately 70%. The case study showed that daily electricity usage could be shifted by approximately 14% and 17% by EWH and HPWHs, respectively, compared to their corresponding average power. Another case study showed that both EHWs and HPWHs, coordinated with PV to reduce morning and evening peaks, could shift approximately 22% of the daily electricity.

Highlights

T HE ubiquity of electric water heaters (EWHs) make them one of the most advantageous appliances for participation in the virtual power plant (VPP) operation for residential buildings
The major contributions of this paper include: (1) the development of generic load curves for daily electricity usage of EWH and heat pump water heaters (HPWHs) based on data retrieved from two large scale projects, respectively; (2) a community level digital twin for water heaters with scalability to any number, which involves the hot water flow, water temperature in the tank, and “energy take”; (3) quantification of the potential of load shifting for both EWH and HPWH under different scenarios
The proposed aggregated generic curves for residential water heaters, which use a minimal amount of data points, are the first of its kind to the best of the authors’ knowledge

Summary

INTRODUCTION

T HE ubiquity of electric water heaters (EWHs) make them one of the most advantageous appliances for participation in the virtual power plant (VPP) operation for residential buildings. The major contributions of this paper include: (1) the development of generic load curves for daily electricity usage of EWH and HPWH based on data retrieved from two large scale projects, respectively; (2) a community level digital twin for water heaters with scalability to any number, which involves the hot water flow, water temperature in the tank, and “energy take”; (3) quantification of the potential of load shifting for both EWH and HPWH under different scenarios. LARGE SCALE EXPERIMENTAL STUDY FOR ELECTRIC WATER HEATER A smart EWH that allow users to control the setpoint, the operating mode and receive alerts based on the device operation was developed by A.O. Smith.

EQUIVALENT EWH AND POSSIBLE MODEL FOR DIGITAL TWIN

E T is rewritten as CT E

CONSTANT POWER OPERATION USING LOAD SHIFTING

DEMAND RESPONSE STUDY FOR MORNING AND EVENING

Findings

CONCLUSION