Air separation with cryogenic energy storage: Optimal scheduling considering electric energy and reserve markets

Abstract

The concept of cryogenic energy storage (CES) is to store energy in the form of liquid gas and vaporize it when needed to drive a turbine. Although CES on an industrial scale is a relatively new approach, the technology is well-known and essentially part of any air separation unit (ASU) that utilizes cryogenic separation. In this work, we assess the operational benefits of adding CES to an existing air separation plant.We investigate three new potential opportunities: (1) increasing the plant's flexibility for load shifting, (2) storing purchased energy and selling it back to the market during higher-price periods, (3) creating additional revenue by providing operating reserve capacity. We develop a mixed-integer linear programming (MILP) scheduling model and apply a robust optimization approach to model the uncertainty in reserve demand.The proposed model is applied to an industrial case study, which shows significant potential economic benefits.

The role of CO 2 purification and transport networks in carbon capture and storage cost reduction

“…Owing to the relatively impure raw exhaust gas which is produced from the oxy-combustion boiler, the CO 2 CPU is crucial to providing a CO 2 stream that is suitable for transport and subsequent sequestration. Thus far, work has been done on maximising the economic revenue of the ASU [23] and minimizing the energy penalty caused by the ASU [22,24,25,26], while relatively little focus has been given to the cost of the CO 2 CPU and how to drive this down. A few studies, however, have looked at modelling the purication and compression process of oxy-combustion derived ue gas for usage in EOR and for its sequestration [17,27,28].…”

Optimal Scheduling of Air Separation with Cryogenic Energy Storage

“…In the proposed framework, robust optimization techniques are applied to model the uncertainty in operating reserve demand. This paper complements the work by Zhang et al (2015) with a more involved industrial case study that provides additional insights into the interactions between gas and liquid production in such a plant.…”

“…This problem can be formulated as an MILP for which the complete formulation is given in Zhang et al (2015). In the following, we highlight the main features of the proposed model:…”

Robust Optimization of Schedules Affected by Uncertain Events

“…An application to an air separation plant is presented in [19] where the uncertainties arise due to the integration of the plant in electricity market mechanisms. The authors of [20] address uncertainties from a bounded set affecting the coefficients of the objective function and the constraints of a scheduling problem, and their scheme is verified on the same example discussed in this paper.…”