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Decentralized Control of Thermostatically Controlled Loads

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A1: Smart Grids and Microgrids".

Deadline for manuscript submissions: closed (25 February 2022) | Viewed by 11097

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Guest Editor
Mechanical & Biomedical Engingineering, Boise State University, Boise, ID 83712, USA
Interests: energy efficiency; renewable energy; smart grid; automation and control; systems modeling
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Special Issue Information

Dear Colleagues,

The rapid deployment of both distributed and centralized renewable energy systems continues to be a challenge to grid operators as they transition from the traditional model of balancing load with generation to the new reality in which grid-level energy storage and continuous load management will play significant roles.  Thermostatically controlled loads (TCLs) present a unique opportunity for continuous load management due to the fact that they are designed to store thermal energy while maintaining the controlled temperature within a band of tolerance. In addition, most TCLs can tolerate even wider temperature swings under certain circumstances.  The current state of the literature more than proves the potential of TCLs to play a critical role in the evolving electric grid, however many challenges remain.  Since the amount of energy that can be counted on to ‘charge’ or ‘discharge’ any given load is rather small, practical applications require the aggregation of a large number of loads that can act in concert. Given the fact that these load are dominated by household appliances like space air conditioners or domestic hot water heaters, large scale penetration of such programs will have to designed around customer sensitivities to personal comfort and private information.

A decentralized approach to the aggregated control of TCLs is indicated if large scale and practical applications are going to be deployed.

Prof. Dr. John Gardner
Guest Editor

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Keywords

  • smart grid
  • demand response
  • energy storage
  • Thermostatically Controlled Loads
  • aggregate loads

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Published Papers (5 papers)

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Research

20 pages, 10854 KiB  
Article
Thermal Stratification and Temperature Variation in Horizontal Electric Water Heaters: A Characterisation Platform
by Pieter D. van Schalkwyk, Jacobus A. A. Engelbrecht and Marthinus J. Booysen
Energies 2022, 15(8), 2840; https://doi.org/10.3390/en15082840 - 13 Apr 2022
Cited by 5 | Viewed by 2311
Abstract
Electric water heaters, which have the capacity to act as thermal energy storage, are well suited to demand management strategies in smart grid applications. However, finding the balance between managing power load, reducing thermal energy losses, user’s convenience, and bacterial growth control, requires [...] Read more.
Electric water heaters, which have the capacity to act as thermal energy storage, are well suited to demand management strategies in smart grid applications. However, finding the balance between managing power load, reducing thermal energy losses, user’s convenience, and bacterial growth control, requires accurate modelling of the internal thermal dynamics of the tank, including stratification. As a black box, this unknown is dependent on a multitude of environmental factors (e.g., ambient temperature and inlet temperature), water draw patterns, scheduling, set temperatures and orientation of the vessel. The latter affects the stratification and temperature variation inside the tank, and therefore has a direct bearing on the balancing act of demand management. Although this has been assessed inside vertically oriented tanks, what happens inside the horizontal variety—ubiquitous in developing countries—is currently left to the guesswork. In this paper, we present the development of an embedded hardware and software platform with which the temperature variations inside a horizontal water heater can be characterised under numerous environmental and usage conditions. The importance of doing so is highlighted by the preliminary results, which clearly show the expected substantial temperature variation along the vertical axis, but also show interesting phenomena along the longitudinal and transverse axes, for both static (no water draw) and dynamic (with water draw) conditions. We conclude by highlighting potential for further research. Full article
(This article belongs to the Special Issue Decentralized Control of Thermostatically Controlled Loads)
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24 pages, 1323 KiB  
Article
Centrally Adapted Optimal Control of Multiple Electric Water Heaters
by Michael J. Ritchie, Jacobus A. A. Engelbrecht and Marthinus J. Booysen
Energies 2022, 15(4), 1521; https://doi.org/10.3390/en15041521 - 18 Feb 2022
Cited by 5 | Viewed by 2017
Abstract
Breakthroughs in smart grid technology make it possible to deliver electricity in controlled and intelligent ways to improve energy efficiency between the user and the utility. Demand-side management strategies can reduce overall energy usage and shift consumption to reduce peak loads. Electric water [...] Read more.
Breakthroughs in smart grid technology make it possible to deliver electricity in controlled and intelligent ways to improve energy efficiency between the user and the utility. Demand-side management strategies can reduce overall energy usage and shift consumption to reduce peak loads. Electric water heaters account for 40% of residential energy consumption. Since they are thermal storage devices, advanced control strategies can improve their efficiency. However, existing methods disregard the connection between the user and the grid. We propose a centrally adapted control model that allows for coordinated scheduling to adapt the optimal control schedule of each EWH, spreading the load into off-peak periods to ensure that the grid’s generation capacity is not exceeded. We consider two strategies for the delivery of hot water: temperature matching, and energy matching with Legionella sterilisation, and compare them to a baseline strategy where the thermostat is always switched on. Simulation results for a grid of 77 EWHs showed that an unconstrained peak load of 1.05 kW/EWH can be reduced as low as 0.4 kW/EWH and achieve a median energy saving per EWH of 0.38 kWh/day for the temperature matching strategy and 0.64 kWh/day for the energy matching strategy, without reducing the user’s comfort. Full article
(This article belongs to the Special Issue Decentralized Control of Thermostatically Controlled Loads)
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18 pages, 1365 KiB  
Article
Centralized and Decentralized Optimal Control of Variable Speed Heat Pumps
by Ryan S. Montrose, John F. Gardner and Aykut C. Satici
Energies 2021, 14(13), 4012; https://doi.org/10.3390/en14134012 - 3 Jul 2021
Cited by 4 | Viewed by 1737
Abstract
Utility service providers are often challenged with the synchronization of thermostatically controlled loads. Load synchronization, as a result of naturally occurring and demand-response events, has the potential to damage power distribution equipment. Because thermostatically controlled loads constitute most of the power consumed by [...] Read more.
Utility service providers are often challenged with the synchronization of thermostatically controlled loads. Load synchronization, as a result of naturally occurring and demand-response events, has the potential to damage power distribution equipment. Because thermostatically controlled loads constitute most of the power consumed by the grid at any given time, the proper control of such devices can lead to significant energy savings and improved grid stability. The contribution of this paper is the development of an optimal control algorithm for commonly used variable speed heat pumps. By means of selective peer-to-peer communication, our control architecture allows for the regulation of home temperatures while simultaneously minimizing aggregate power consumption, and aggregate load volatility. An optimal centralized controller is also explored and compared against its decentralized counterpart. Full article
(This article belongs to the Special Issue Decentralized Control of Thermostatically Controlled Loads)
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26 pages, 3379 KiB  
Article
Distributed Control of Clustered Populations of Thermostatic Loads in Multi-Area Systems: A Mean Field Game Approach
by Vincenzo Trovato, Antonio De Paola and Goran Strbac
Energies 2020, 13(24), 6483; https://doi.org/10.3390/en13246483 - 8 Dec 2020
Cited by 2 | Viewed by 1738
Abstract
Thermostatically controlled loads (TCLs) can effectively support network operation through their intrinsic flexibility and play a pivotal role in delivering cost effective decarbonization. This paper proposes a scalable distributed solution for the operation of large populations of TCLs providing frequency response and performing [...] Read more.
Thermostatically controlled loads (TCLs) can effectively support network operation through their intrinsic flexibility and play a pivotal role in delivering cost effective decarbonization. This paper proposes a scalable distributed solution for the operation of large populations of TCLs providing frequency response and performing energy arbitrage. Each TCL is described as a price-responsive rational agent that participates in an integrated energy/frequency response market and schedules its operation in order to minimize its energy costs and maximize the revenues from frequency response provision. A mean field game formulation is used to implement a compact description of the interactions between typical power system characteristics and TCLs flexibility properties. In order to accommodate the heterogeneity of the thermostatic loads into the mean field equations, the whole population of TCLs is clustered into smaller subsets of devices with similar properties, using k-means clustering techniques. This framework is applied to a multi-area power system to study the impact of network congestions and of spatial variation of flexible resources in grids with large penetration of renewable generation sources. Numerical simulations on relevant case studies allow to explicitly quantify the effect of these factors on the value of TCLs flexibility and on the overall efficiency of the power system. Full article
(This article belongs to the Special Issue Decentralized Control of Thermostatically Controlled Loads)
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23 pages, 11817 KiB  
Article
Fast Transactive Control for Frequency Regulation in Smart Grids with Demand Response and Energy Storage
by Andrew Ly and Saeid Bashash
Energies 2020, 13(18), 4771; https://doi.org/10.3390/en13184771 - 12 Sep 2020
Cited by 12 | Viewed by 2392
Abstract
This paper proposes a framework for controlling grid frequency by engaging the generation-side and demand-side resources simultaneously, via a fast transactive control approach. First, we use a proportional frequency-price relation to build and analyze a transactive frequency droop controller for a single-area power [...] Read more.
This paper proposes a framework for controlling grid frequency by engaging the generation-side and demand-side resources simultaneously, via a fast transactive control approach. First, we use a proportional frequency-price relation to build and analyze a transactive frequency droop controller for a single-area power grid. Then, we develop a transactive demand response system by incorporating a large population of thermostatically controlled air conditioning loads. A proportional-integral controller is used to adjust the setpoint temperature of the air conditioners based on price variations. A battery storage system is then developed and augmented to the system to capture the energy arbitrage effects. A nonlinear price-responsive battery management system is developed to enable effective charging and discharging operations within the battery’s state-of-charge and power constraints. Simulation results indicate that the proposed transactive control system improves the steady-state and transient response of the grid to sudden perturbations in the supply and demand equilibrium. To decouple frequency from price during daily operation and maintain frequency near the nominal value, we propose adding a feedforward price broadcast signal to the control loop based on the net demand measurement. Through various simulations, we conclude that a combination of feedback transactive controller with feedforward price broadcast scheme provides an effective solution for the simultaneous generation-side and demand-side energy management and frequency control in smart power grids. Full article
(This article belongs to the Special Issue Decentralized Control of Thermostatically Controlled Loads)
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