Incorporating thermoelectric power plant water use into multi-objective optimal power flow

Abstract

Traditionally, power systems have been operated to minimize cost while maintaining reliability. However, extreme weather and demand events can affect traditional thermoelectric power generation operations due to their reliance on water for cooling. This paper contributes a novel multi-objective formulation of the optimal power flow (OPF) problem where cost, water withdrawal, and water consumption are minimized. Through this formulation, we assign optimization weights to water withdrawn and consumed, which can be directly incorporated into existing OPF formulations. We apply this formulation with a global mapping sensitivity analysis to a realistic case study to first demonstrate its general effectiveness under extreme climatic, hydrologic, and operational scenarios. Then, we apply a global ranking sensitivity analysis to determine the most influential generators for system performance. Through this operational scenario analysis framework, analysts can gain insights into potential system-level and component-level vulnerabilities within power systems. Such insights can be useful for informing both short-term operations as well as long-term power system planning.

Balancing cost, water, emissions, and reliability in power systems operations

“…For example, a water withdrawal penalty with the units of dollars per gallon of water allows us to define a water withdrawal cost term to be directly added to other operational costs. Such a policy formulation is an extension of that proposed in Kravits et al (2022b).…”

“…This 180 line transmission system has a 2800 MW capacity with half of its capacity coming from coal and the remaining capacity being equally split between natural gas, wind, and nuclear. Cooling systems have been assigned to these generators following the methods proposed in Kravits et al (2022b). Generator-specific parameters are sourced from Myhre (2002), James et al (2019), and the Energy Information Agency Form 923.…”

“…Generator-specific parameters are sourced from Myhre (2002), James et al (2019), and the Energy Information Agency Form 923. We set a maximum regulatory discharge temperature for once-through generators to be 90 (Macknick et al 2012) as well as the regional estimates in Kravits et al (2022b). A value of lost load of $3300 MWh is used given historic Midcontinent Independent System Operator (MISO) values (Cook 2021).…”

“…A policy in this paper consists of three decisionsthe per unit costs assigned to water consumption, water withdrawal, and carbon dioxide emissions. Such costs allow water use and emissions to be directly incorporated into existing power systems operations and are an extension of previously proposed water/energy policy frameworks (Kravits et al 2022b). We couple existing models of thermoelectric power plant water use (Rutberg et al 2011, van Vliet et al 2016, emissions rates, and power systems reliability in the real-world operational problem of optimal power flow (OPF), which optimizes generator power output based on a minimization of operational costs.…”