J. Mays, M.T. Craig, L. Kiesling, J.C. Macey, B. Shaffer, and H. Shu. Private Risk and Social Resilience in Liberalized Electricity Markets. Joule 6(2), 369-380 (2022).
Energy-only electricity markets, such as the Electric Reliability Council of Texas (ERCOT), rely on the decentralized investment decisions of market participants to lead to a resource mix providing an efficient level of reliability. During an exceptionally cold winter storm in February 2021, ERCOT experienced shortfalls on an unprecedented scale, with nearly half of the generation fleet experiencing outages at the peak. The depth of the resulting blackouts invites questions regarding the ability of systems relying on decentralized planning to appropriately prepare for and withstand rare events. Based on two mild assumptions, risk aversion among investors and incomplete risk trading, this paper offers an explanation for why decentralized markets are prone to underinvestment in resilience. We describe the nature of the incomplete risk trading that arises in the context of electricity markets and discuss potential remedies, including mandatory contracting obligations for retailers and compensation to end users for unserved energy.
M. Ahlstrom, J. Mays, E. Gimon, A. Gelston, C. Murphy, P. Denholm, and G. Nemet. Hybrid Resources: Challenges, Implications, Opportunities, and Innovation. IEEE Power and Energy Magazine 19(6), 37-44 (2021)
The electric power system has historically been designed to provide reliable energy to loads by using a relatively small number of well-understood generators. The distinction between load, generation, and transmission resources has been quite clear. Most of the responsibility for planning and operating a system—building a highly reliable network from less reliable parts—has been with the system manager, whether that be a utility, a regional market operator, or some similar entity. Given this historical context, many experts were initially perplexed by the rapidly growing popularity of hybrid resources, which combine multiple technologies into a single entity. Rather than depending on a system operator to provide instructions to individual technologies, hybrid resources intentionally take on more operational responsibility by optimizing and scheduling their combined functions. Interconnection queues in many regions reveal a large and growing interest in hybrids, suggesting that project developers and investors see them as providing advantages.
J. Mays. Quasi-Stochastic Electricity Markets. INFORMS Journal on Optimization 3(4), 350-372 (2021).
With wind and solar becoming major contributors to electricity production in many systems, wholesale market operators have become increasingly aware of the need to address uncertainty when forming prices. While implementing theoretically ideal stochastic market clearing to address uncertainty may be impossible, the use of operating reserve demand curves allows market designers to inject an element of stochasticity into deterministic market clearing formulations. The construction of these curves, which alter the procurement of reserves and therefore the pricing of both reserves and energy, relies on contentious administrative parameters that lack strong theoretical justification. This paper proposes instead to construct curves based on reserve valuations implicit in non-market reliability processes performed by system operators. The proposed strategy promotes greater consistency between commitment decisions and eventual prices, reducing the need for discriminatory uplift payments or enhanced pricing schemes to address non-convexity.
J. Mays. Missing incentives for flexibility in wholesale electricity markets. Energy Policy, 149, 112010 (2021).
In most liberalized electricity markets, flaws in short-term price formation have led to a “missing money” problem wherein average energy prices are too low to support an efficient level of capacity. Recent growth of wind and solar generation has exposed another category of flaws related to intertemporal constraints, such that energy prices are not volatile enough to support an efficient level of flexibility. In theory, electricity markets convey the value of flexibility through time-varying prices, encouraging market participants to invest in resources able to match production and consumption profiles to grid needs. Real-world market clearing procedures, however, make several simplifications that suppress volatility relative to the theoretical ideal. This paper describes five mechanisms by which current wholesale electricity market price formation may fail to provide full-strength incentives for flexible resources. Instead of restoring price volatility, market designers may choose to define flexibility products that act as a proxy for full-strength prices. However, these products cannot replicate theoretically ideal incentives precisely, with potentially important consequences for small-scale and distributed resources. The analysis could help guide ongoing efforts to ensure that systems have the capability to respond to growing variability and uncertainty in an efficient way.
J. Mays, D. Morton, and R. O'Neill. Investment Effects of Pricing Schemes for Non-Convex Markets. European Journal of Operational Research 289(2), 712-726 (2021).
EJOR Editors’ Award
Non-convex markets, such as those organized by electricity system operators, lack uniform clearing prices. In an attempt to align private and social costs when clearing these markets, operators have introduced a variety of price formation and uplift payment schemes. We investigate the impact that the choice of pricing scheme can have on generator entry and exit decisions. Our results suggest that despite the presence of fixed production cost elements, prices derived from marginal costs support the optimal capacity mix. The use of uplift payments to supplement these prices could lead to significant distortion of the capacity mix arising in competitive markets. Pricing schemes designed to reduce the need for uplift payments may at the same time reduce prices, leading to lower levels of capacity in equilibrium. Schemes intended to raise prices, to the extent they eliminate the need for discriminatory side payments, may allow system operators to support a higher level of capacity with less distortion to the capacity mix.
J. Mays, D. Morton, and R. O'Neill. Asymmetric risk and fuel neutrality in electricity capacity markets. Nature Energy, 4, 948-956 (2019).
INFORMS ENRE Student Best Paper Award
In many liberalized electricity markets, power generators can receive payments for maintaining capacity through capacity markets. These payments help stabilize generator revenues, making investment in capacity more attractive for risk-averse investors when other outlets for risk trading are limited. Here we develop a heuristic algorithm to solve large-scale stochastic equilibrium models describing a competitive market with incomplete risk trading. Introduction of a capacity mechanism has an asymmetric effect on the risk profile of different generation technologies, tilting the resource mix towards those with lower fixed costs and higher operating costs. One implication of this result is that current market structures may be ill-suited to financing low-carbon resources, the most scalable of which have high fixed costs and near-zero operating costs. Development of new risk trading mechanisms to replace or complement current capacity obligations could lead to more efficient outcomes.
J. Mays. Cost Allocation and Net Load Variability. IEEE Transactions on Power Systems, 33(2), 2030-2039 (2018).
A basic principle of electricity market design is that cost allocation should follow cost causation as closely as possible. As renewable resources play a larger role in electricity generation, system operators have become increasingly concerned about costs related to variability in net load. While variable generation resources have attracted a great deal of attention along these lines, load is a larger source of variability in most systems. This paper introduces a Shapley value framework to assess the total system cost attributable to electricity market participants that either exacerbate or alleviate net load variability. Further, this paper investigates the extent to which these costs are adequately reflected in wholesale market prices. Numerical tests indicate that the cost of variability on the hourly time scale is in most cases internalized by market-integrated generators and buyers, mitigating concerns that variability imposes a socialized cost from ramping or cycling of thermal generators.
J. Mays and D Klabjan. Optimization of Time-Varying Electricity Rates. The Energy Journal, 38(5), 67-91 (2017).
Current consensus holds that 1) passing through wholesale electricity clearing prices to end-use consumers will produce maximal efficiency gains and 2) simpler forms of time-varying retail rates will capture only a small portion of potential benefits. We show that neither holds in the presence of capacity costs typical in U.S. wholesale markets. Using an optimization model describing the short-term problem faced by an electricity retailer, we find hourly prices that optimally pass through capacity costs. We estimate benefits for a retailer using these prices as well as optimal configurations of a number of time-varying rate structures. Testing a range of realistic assumptions, we find that in the absence of a well-designed demand charge, passing through clearing prices may miss up to three quarters of the benefits possible from optimal hourly prices. By contrast, a simpler critical peak pricing structure enables retailers to achieve approximately two-thirds of the total possible benefits.
Efficient Prices under Uncertainty and Non-Convexity
Joint with Brent Eldridge and Ben Knueven
Operators of organized wholesale electricity markets attempt to form prices in such a way that the private incentives of market participants are consistent with a socially optimal commitment and dispatch schedule. In the U.S. context, several competing price formation schemes have been proposed to address the non-convex production cost functions characteristic of most generation technologies. This paper considers how the design and analysis of price formation policies for non-convex markets is affected by the uncertainty inherent in electricity demand and supply. We argue that by excluding uncertainty, the analytical framework underlying existing policies mischaracterizes the incentives of market participants, leading to inefficient price formation and poor incentives for flexibility. We establish favorable theoretical properties of a new construct, ex ante convex hull pricing, demonstrate the difference between this policy and existing methods on an ISO-scale test system, and discuss the implications for price formation in organized wholesale markets.
Congestion Risk, Transmission Rights, and Investment Equilibria in Electricity Markets
Financial instruments that help provide revenue certainty are fundamental for project finance in liberalized electricity markets. Nodal markets have financial transmission rights (FTRs), which enable participants to manage locational risk caused by network congestion. Despite the industry’s concern for locational risk, there is no evidence that FTRs are used to support project finance. Through a stochastic equilibrium model in which market participants invest in production assets and trade risk, we show that long-term FTRs promote surplus-maximizing investments and reduce the cost of capital. Investors pair them with energy price hedges and thus protect themselves against both types of risk. Our results suggest that altering the tenor and auction design for long-term FTRs to match the needs of project finance could help ensure a complete risk market and encourage surplus-maximizing investments. Improved management of locational risk is becoming increasingly important with a growing share of production from geographically remote renewable resources.
Generator Interconnection, Network Expansion, and Energy Transition
Inefficient coordination between decentralized generation investment and centralized transmission planning is a significant barrier to achieving rapid decarbonization in liberalized electricity markets. While the optimal configuration of the transmission grid depends on the relative social costs of competing technologies, existing processes have not led to transmission expansion consistent with declines in the cost of wind and solar combined with increased estimates of the social costs of traditional thermal resources. To break the negative feedback loop preventing efficient network expansion, this paper proposes an inversion of the generator interconnection process in conjunction with modifications in the definition of financial rights connected with transmission service. From a generator perspective, the effect of the proposed reforms is to trade highly uncertain network upgrade and congestion costs for a fixed interconnection fee. From a transmission planning perspective, the goal is to improve the quality of information about new generation included in forward-looking planning processes. Simulation on a stylized two-node system demonstrates the potential of the approach to facilitate a transition to clean technologies.
Electricity Markets under Deep Decarbonization
This paper considers the evolution of electricity market design as systems shift toward carbon-free technologies. Large-scale energy system models commonly project that in many decarbonized systems, a majority of energy will be provided by wind and solar resources. Two characteristics of these resources, variability and zero marginal cost, are likely to lead to increased price volatility on diurnal and seasonal timescales. In the standard risk-neutral optimization framework, volatility does not pose any theoretical issues for market design. Because revenue volatility has the potential to lead to a higher cost of capital for investments in competitive markets, however, many observers have questioned the viability of competitive models for resource adequacy as wind and solar grow in importance. To assess the role of risk management in overall market performance, we construct a stochastic equilibrium model incorporating financial entities as hedge providers for investors in generation capacity. Unlike in the standard optimization framework, the cost of capital in the equilibrium framework is endogenously determined by interannual revenue volatility and the risk measures used by market participants. Surprisingly, exploratory numerical tests suggest that overall investment risk may be lower in systems dominated by variable renewables due to reduced exposure to fuel price uncertainty. However, changes in investment risk are not uniform across resource types, and increased risk for peaking and backup resources contributes to lower reliability in the modeled future systems.