Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Comments on characterizing demand flexibility to provide power grid services

Prabir Barooah

Abstract

Many loads have flexibility in demand that can be used to provide ancillary services to power grids. A large body of literature exists on designing algorithms to coordinate actions of many loads to provide such a service. The topic of characterizing the flexibility of one or a collection of loads - to determine what kinds of demand deviation from the baseline is feasible - has also been studied. However, there is a large diversity in definitions of flexibility and methods proposed to characterize flexibility. As a result there are several gaps in the literature on flexibility characterization. Some approaches on flexibility characterization are based on ad-hoc approximations that lead to highly conservative estimates. In this paper we point out some of these issues and their implications, with the hope to encourage additional research to address them.

Comments on characterizing demand flexibility to provide power grid services

Abstract

Many loads have flexibility in demand that can be used to provide ancillary services to power grids. A large body of literature exists on designing algorithms to coordinate actions of many loads to provide such a service. The topic of characterizing the flexibility of one or a collection of loads - to determine what kinds of demand deviation from the baseline is feasible - has also been studied. However, there is a large diversity in definitions of flexibility and methods proposed to characterize flexibility. As a result there are several gaps in the literature on flexibility characterization. Some approaches on flexibility characterization are based on ad-hoc approximations that lead to highly conservative estimates. In this paper we point out some of these issues and their implications, with the hope to encourage additional research to address them.
Paper Structure (14 sections, 11 equations, 4 figures)

This paper contains 14 sections, 11 equations, 4 figures.

Table of Contents

  1. Introduction
  2. QoS constraints of consumers and grid balancing authorities
  3. Flexibility of one load (consumer focus)
  4. Why the definition matters
  5. A conservative estimation of flexibility
  6. Definitions for deferrable loads
  7. (Under-appreciated) Role of humidity in HVAC flexibility
  8. Flexibility characterization of large commercial HVAC systems is an opportunity
  9. Flexibility of a load collection (consumer focus)
  10. Grid operators' requirements on flexibility
  11. Battery equivalent characterization of flexible demand
  12. Cost of demand flexibility service
  13. Flexibility characterization for long term grid planning
  14. Conclusion

Figures (4)

  • Figure 1: Simulation evidence: the largest envelope of power deviation is rather small ($\Delta_{\theta}/R\eta_{\text{COP}} = 0.1055$ kW in this case; the dashed line) in order to ensure temperature constraints ($\pm 1$$\degree\text{C}$), while a sinusoidal variation with much larger amplitude, $0.3$ kW, can still maintain temperature within the same range if the frequency of the sinusoid is large enough (1 hour$^{-1}$ in this case).
  • Figure 2: A single zone VAV HVAC system.
  • Figure 3: A hydronic HVAC system used in large buildings. The TES shown is not common.
  • Figure 4: Increase in timescale of virtual energy storage by coordinating a collection of loads.