Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Optimized power dispatch for solar photovoltaic-storage system with multiple buildings in bilateral contracts Syed M. Ahsan a, ⁎ , Hassan A. Khan a , Naveed-ul Hassan a , Syed M. Arif b , Tek-Tjing Lie b a Department of Electrical Engineering, SBA School of Science and Engineering, Lahore University of Management Sciences, LUMS, Lahore 54792, Pakistan b Electrical and Electronic Engineering Department, School of Engineering, Computer and Mathematical Sciences, Auckland University of Technology, AUT, Auckland, New Zealand ARTICLE INFO Keywords: Photovoltaics Energy storage system Mixed integer linear programming Commercial buildings Bilateral contracts Techno-economic assessment ABSTRACT Storage coupled solar photovoltaic systems have gained traction in recent years due to a) advancements in battery storage technologies and b) decreasing system costs. The viability and optimum operation of these systems is typically studied for building(s) in isolation or with grid interactions. In this paper a grid-interactive photovoltaic-storage system in a multi building scenario with net-metering is evaluated. A simulation model is developed for an interconnected multi building environment with a primary building owning the photovoltaic- battery system. The optimization model is formulated as a mixed integer linear programming problem and is solved in ILOG optimization studio with CPLEX solver. Multiple secondary buildings can procure power from the primary building based on suitable bilateral contracts. The applicability of the model is demonstrated through real-time load demand of three buildings along with actual time-of-use pricing data from the utility in the city of Auckland, New Zealand. The results provide an insight on the financial gains of installing rooftop photovoltaic- battery systems at buildings with power trading agreements under time-varying electricity tariffs. The detailed results from the model signify that primary building (with solar and storage) earns up to 43% of annual profits after incorporating installation costs of photovoltaic-battery system. Further, secondary buildings (without solar or storage) achieve 3–16% of savings in the electricity costs based on different contracted loads and agreement tariffs. This work can further enhance the utilization of solar energy resource via rooftop solar photovoltaic to help mitigate the per capita carbon dioxide emissions in countries with high dependency over fossil fuel for electricity generation. 1. Introduction 1.1. Background and motivation Solar photovoltaics (PV) have seen a large influx over the past few years due to decreasing module costs making PV very competitive even in residential and commercial domestic settings [1,2]. Two types of financial incentives are typically offered by utilities through either Feed-in tariffs (FiTs) or Net-metering. FiTs are government incentivized policies in which long-term power purchase agreements (PPAs) are signed with the utility for providing surplus electricity to the grid [3]. During last decade, FiT schemes have been frequently revised with addition of tax incentives, green certificates and subsidies to encourage large scale solar PV deployment [4]. To support small prosumers in their interaction with the grid, net-metering schemes have also been developed [3,5]. The provision of net-metering with the national grid also encourages the installation of solar PV, giving prosumers an op- portunity to sell the electricity back to the grid at the time of peak generation [6]. The savings and benefits through net-metering largely depend upon local electricity pricing and legislative constraints limiting the amount of exchanged energy [7]. Net-metering tariffs vary in dif- ferent regions or countries, however in developed countries, the com- pensation for distributed PV generation is typically about one third to one half of the retail electricity price [8]. This is where storage-based PV systems are becoming popular where surplus solar PV may be stored for peak time usage [9]. Various technologies are available in the market for energy storage including lead-acid, lithium-ion-iron-phos- phate and lithium ion (Li-ion) [10]. Even though Lead-acid is most mature technology at prices of around US$150–200/kWh [11], their utility is low due to poor round trip efficiency and a low depth of dis- charge requirement (around 50%) [12,13]. Li-ion based storage, on the other hand, has gained significant attention due to their higher energy https://doi.org/10.1016/j.apenergy.2020.115253 Received 20 February 2020; Received in revised form 15 May 2020; Accepted 21 May 2020 ⁎ Corresponding author. E-mail address: syed.razvi@lums.edu.pk (S.M. Ahsan). Applied Energy 273 (2020) 115253 0306-2619/ © 2020 Elsevier Ltd. All rights reserved. T