Factoring the Cycle Aging Cost of Batteries Participating in Electricity Markets

When participating in electricity markets, owners of battery energy storage systems must bid in such a way that their revenues will at least cover their true cost of operation. Since cycle aging of battery cells represents a substantial part of this operating cost, the cost of battery degradation must be factored in these bids. However, existing models of battery degradation either do not fit market clearing software or do not reflect the actual battery aging mechanism. In this paper we model battery cycle aging using a piecewise linear cost function, an approach that provides a close approximation of the cycle aging mechanism of electrochemical batteries and can be incorporated easily into existing market dispatch programs. By defining the marginal aging cost of each battery cycle, we can assess the actual operating profitability of batteries. A case study demonstrates the effectiveness of the proposed model in maximizing the operating profit of a battery energy storage system taking part in the ISO New England energy and reserve markets

Convex Hull Pricing in Electricity Markets: Formulation, Analysis, and Implementation Challenges

Abstract Widespread interest in Convex Hull Pricing has unfortunately not been accompanied by an equally broad understanding of the method. This paper attempts to narrow the gap between enthusiasm and comprehension. Most importantly, Convex Hull Pricing is developed in an understandable mannerstarting with a discussion of basic electricity market processes and ending with a new mathematical formulation of Convex Hull Pricing. From this mathematical formulation, a variety of important properties are derived and discussed. To illustrate that the [sometimes counterintuitive] properties of Convex Hull Pricing are not merely theoretical, several simple examples are presented. It is hoped that this paper will spur additional research on the pricing scheme so that an informed judgment can be made regarding its costs and benefits

Hole transport assisted by the piezoelectric field in In0.4Ga0.6N/GaN quantum wells under electrical injection

The authors observe the significant penetration of electrically injected holes through InGaN/GaN quantum wells (QWs) with an indium mole fraction of 40%. This effect and its current density dependence were analysed by studies on micro-pixel light-emitting diodes, which allowed current densities to be varied over a wide range up to 5 kA/cm2. The systematic changes in electroluminescence spectra are discussed in the light of the piezoelectric field in the high-indium-content QWs and its screening by the carriers. Simulations were also carried out to clarify the unusual hole transport mechanism and the underlying physics in these high-indium QWs

Hole transport assisted by the piezoelectric field in In0.4Ga0.6N/GaN quantum wells under electrical injection

The authors observe the significant penetration of electrically injected holes through InGaN/GaN quantum wells (QWs) with an indium mole fraction of 40%. This effect and its current density dependence were analysed by studies on micro-pixel light-emitting diodes, which allowed current densities to be varied over a wide range up to 5 kA/cm2. The systematic changes in electroluminescence spectra are discussed in the light of the piezoelectric field in the high-indium-content QWs and its screening by the carriers. Simulations were also carried out to clarify the unusual hole transport mechanism and the underlying physics in these high-indium QWs