Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener Techno-economic analysis of a hybrid solar PV-grid powered air-conditioner for daytime office use in hot humid climates – A case study in Kumasi city, Ghana R. Opoku a, ⁎ , K. Mensah-Darkwa b , A. Samed Muntaka c a Department of Mechanical Engineering, KNUST, Ghana b Department of Materials Engineering, KNUST, Ghana c Department of Supply Chain and Information Systems, KNUST, Ghana ARTICLE INFO Keywords: Solar air-conditioning Hybrid system Energy efficiency Solar fraction Cost savings ABSTRACT Air-conditioners are the highest energy consuming appliances in the offices of businesses, public and commercial buildings in hot humid climates. In Ghana, survey conducted indicates that 60–80% of electricity used in offices of public and commercial buildings is for air-conditioning. Many hot climates, and Ghana in particular, are endowed with high solar irradiations. The need for daytime office space cooling is actually as a result of high solar radiation levels. In the present work, studies have been conducted on the performance of a hybrid solar PV-grid powered air- conditioner for daytime office cooling in hot humid climates with a case study in Kumasi city, Ghana. A standard office of 30 m 2 floor area (105 m 3 office space) in a building with three of the sides sharing walls with adjacent offices, and the front side facing north was used for the study, with the air-conditioner set at a temperature of 20 °C. In the experiment, the pure sine wave hybrid inverter with integrated PWM charge control system was set to solar energy priority and supported by utility grid electricity when solar energy is not sufficient. It has been determined that for daytime office cooling, a 1040 Wp solar PV system with 200 Ah, 24 V battery configuration has a monthly mean solar fraction of 51% ± 9% for an air-conditioner with nominal cooling capacity of 2.5 kW and maximum power consumption of around 1.19 kW. The energy generation of the 1040 Wp solar PV system has been determined to be around 1211 kWh per year. Financial analysis has revealed that for the hybrid solar PV-grid powered air-conditioner, there is potential savings of US$ 1600 compared to 100% utility grid electricity in 10 years. It has also been estimated using available data that there is a potential of about US$ 3300 savings when the air-conditioner is powered with 100% solar energy compared to 100% utility grid electricity in 10 years, for daytime office use. 1. Introduction The ambient temperature and relative humidity of hot and humid countries can get as high as 41 °C and 84%, respectively, (Thani et al., 2013; Ghaffarianhoseini et al., 2015). Methods and techniques of im- proving outdoor thermal comfort using artificial means have therefore extensively been explored (O’Malley et al., 2015; Thani et al., 2012). According to the ASHRAE (2013) and ISO 7730-2005 standards and other published research works on indoor thermal comfort for people, the indoor conditions should be maintained around 20–25 °C and 50–55% relative humidity. Room air-conditioning is therefore very crucial for pro- viding the necessary indoor thermal comfort for normal human activities and productive office work in hot and humid climates (Jin et al., 2017). Air-conditioning equipment/systems are the largest energy con- suming devices in the offices of public and commercial buildings in hot- humid climates or relatively high atmospheric temperature countries/ regions (Al-Ugla et al., 2016; Aguilar et al., 2014). Air-conditioning equipment can consume as much as 50–80% of total electricity con- sumption of residential, public and commercial buildings in both de- veloped and developing countries (Pérez-Lombard et al., 2008). Cost of electricity to the consumer from conventional fossil-fuel power plants keep on rising due to high transmission and distribution losses in de- veloping countries like Ghana (Gyamfi et al., 2017). Electricity generation in developing countries have low levels of renewable electricity generation systems, for instance, abundant solar energy in Africa continue to be under-developed (REN 21, 2017; https://doi.org/10.1016/j.solener.2018.03.013 Received 10 August 2017; Received in revised form 28 February 2018; Accepted 5 March 2018 ⁎ Corresponding author at: Kwame Nkrumah University of Science and Technology (KNUST), Ghana. E-mail address: ropoku.coe@knust.edu.gh (R. Opoku). Solar Energy 165 (2018) 65–74 0038-092X/ © 2018 Published by Elsevier Ltd. T