Comparison of Two Approaches for Managing Building Flexibility Using Energy Market Prices

Summary

Publication Title: Comparison of Two Approaches for Managing Building Flexibility Using Energy Market Prices

Series Title: NIST Technical Notes

Personal Author: Holmberg, David.

Publication Number: NIST tech note; NIST TN; 2241

Date Issued: 2022

Subject: Heat pumps
Electric power systems
Co-simulation
Distribution grid
Dynamic pricing
Energy flexibility
Load forecasting
Grid-edge systems
GridLAB-D
Heat pump controller
Hosting capacity
Power quality
Price-responsive controller
Real-time market
Real-time price
Transactive energy
Volatility
Voltage violations

Government Author: Commerce Department, National Institute of Standards and Technology (NIST) .

Category: Executive Agency Publications

SuDoc Class Number: C 13.

Abstract: Transactive energy may provide a way to support integration of customer distributed energy resources (DER) into the electric grid and to help manage DER flexibility to support distribution system and bulk grid needs. Use of DER flexibility includes peak shifting in response to forward market prices, real-time regulation in response to 5-minute prices, and, potentially, voltage regulation in response to distribution nodal prices. The work presented here compares two approaches for managing heat pump cooling to provide grid services. The first approach implements a rule-based real-time controller that manages power consumption based on 5-minute real-time prices. The second controller uses a model-based approach to optimize load based on day-ahead hourly prices. These approaches are evaluated on two reference grids using GridLAB-D with the same weather and price information. The real-time controller reacts to a volatile price signal to reduce homeowner energy use and energy costs. The model-based controller minimizes energy use by pre-cooling before the price peak and allowing indoor temperature to drift up during peak price times. The model-based controller strategy results in cost savings when temperatures are allowed to move farther from the desired setpoint. Because this controller does not respond to real-time price volatility, there are no cost savings during sub-hourly real-time price spikes. Simulation results show both controllers adjusting temperature setpoints in response to price movement, reducing customer cost while staying within pre-defined comfort boundaries. These temperature adjustments resulted in significant power flow volatility at the substation. The average power flow change for the real-time controller, time step to time step, was approximately 10 % of the peak load. Some observed power flow changes were equivalent to simultaneously turning off or on all price-responsive loads on the grid. This power flow volatility resulted in voltage volatility at customer meters and greatly increased voltage regulator and capacitor bank actions on one of the tested grids. Analysis suggests that power flow volatility may be expected when many devices are price-responsive and controllers have the goal of reducing cost without considering voltage. Care must be taken to reduce the volatility of the price signal and boost hosting capacity to support synchronized price response by a large percentage of load.