Assessment of a Compressed Air Energy Storage System using gas pipelines as storage devices in Chile Patricio Valdivia a, * , Rodrigo Barraza b , David Saldivia b, c , Leonardo Gacitúa a , Aldo Barrueto a , Danilo Estay b a Department of Electrical Engineering, Universidad T ecnica Federico Santa Maria, Av. Vicu~ na Mackenna, 3939, Santiago, Chile b Department of Mechanical Engineering, Universidad T ecnica Federico Santa Maria, Av. Vicu~ na Mackenna, 3939, Santiago, Chile c School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW, 2052, Australia article info Article history: Received 14 January 2019 Received in revised form 5 September 2019 Accepted 7 September 2019 Available online 10 September 2019 Keywords: Renewable energy Energy storage CAES Compressed air energy storage Electrical market abstract Some of the existing natural gas pipelines in Chile are underutilized; thus, these reservoirs could be utilized as Compressed Air Energy Storage (CAES) systems taking advantages of fluctuations in the price of electricity related to the entrance of renewable energy sources in the electrical market. A thermo- dynamic and economic-optimization of CAES system using existing gas pipelines under different oper- ating conditions is performed. Substations located in the proximity to existing gas pipelines are assessed as possible CAES locations. Throughout the day, the CAES system compresses air, charges the pipeline by buying energy during low prices, and expands the air, discharging the pipeline by selling energy when prices are high. One of the Northern substations (Taltal) shows the best results where more of the photovoltaic power plant are located; consequently, CAES is more profitable when high difference in marginal cost is present along the day, which happens on grids with high renewable share. Therefore, the daily variations of marginal costs should be a key parameter decision to operate the CAES plant. With higher marginal costs fluctuations throughout the day, CAES systems should become more attractive economically. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, renewable energy is the fastest growing source of electricity, especially PV solar and wind technologies. The world- wide total cumulative installed electric generation capacity is 303GW from PV solar power and 487GW from wind power at the end of 2016 [1]. According to the 2017 BP Energy Outlook [2], renewable energy has an annual projected growth of 7%, increasing from 3% to 20% between 2015 and 2035. While a bigger part of the energy matrix is becoming renewable, different challenges arise for the electric grid system. Renewables, mainly solar and wind, have daily and seasonal cycles and an inherently variable output due to the intrinsic nature of their energy sources and the greater influ- ence of weather conditions. Among the main challenges that renewable energy imposes on the grid system is ensuring a dispatchable baseload production throughout the day, having a flexible grid in order to avoid short-term unpredictable variability of green production, and reshaping production to fit the load pro- file. Energy storage addresses all of these problems as long as en- ergy storage systems are technically feasible and economically viable [3e5]. Several systems have been proposed for energy stor- age, however no consensus about the best alternatives to solve these problems exists. Some of the proposed alternatives are sen- sitive heat storage, pumped hydroelectric storage (PHS), electro- chemical batteries (BES), flywheels, capacitors, phase change materials, Power to Gas (P2G), and compressed air (CAES) [4e6]. A Compressed Air Energy Storage (CAES) system is a plant that allows storage of energy by means of air compression. The energy is subsequently released by power generation using a gas turbine. The main characteristics required for the storage unit are: a large vol- ume capacity, a high pressure operation, and a long-term stable behavior [7]. Different structures are proposed as storage units, including underground salt caverns, underground mines, aquifers, and expired wells or gas chambers. CAES systems are proposed as an alternative to solve the temporal difference between renewable * Corresponding author. E-mail addresses: patricio.valdivial@usm.cl (P. Valdivia), rodrigo.barraza@usm.cl (R. Barraza), david.saldivia@usm.cl (D. Saldivia), leonardo.gacitua@usm.cl (L. Gacitúa), aldo.barrueto@usm.cl (A. Barrueto), danilo.estay@usm.cl (D. Estay). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene https://doi.org/10.1016/j.renene.2019.09.019 0960-1481/© 2019 Elsevier Ltd. All rights reserved. Renewable Energy 147 (2020) 1251e1265