In March 2021, a group of researchers from the EnerSHelF project published a paper in the IZNE Working Paper Series: “PV-diesel-hybrid system for a hospital in Ghana – Connection of a PV battery storage model to an existing generator model”. Matthias Bebber, leading author of the paper, summarizes the working paper in this article. You can access the paper on the H-BRS website.
Summary by Matthias Bebber
In our paper, we present a model of a grid-integrated PV-diesel-hybrid system. The model is based on an existing simulation tool from Cologne University of Applied Sciences and was further developed in the context of this paper. By means of real measurement data of PV yield and electricity consumption of a hospital in Ghana – collected in a period from February 2016 to 2017 – the behaviour of the hybrid system in different scenarios is examined. The influence of power outages and seasonal differences in solar radiation on the use of generator and electricity demand from the public power grid for different battery sizes is considered. Special attention is paid to the meteorological and atmospheric characteristics in Ghana, such as the rainy and dry seasons, as well as the harmattan, a seasonal wind in West Africa that carries a lot of dust.
The present work shows that during the rainy season there is a significant reduction in PV output of up to 54 % compared to the maximum output. As a result, the electricity demand from the public power grid and diesel consumption during this time are significantly increased, which cannot be balanced even by using a larger battery storage unit as shown in the simulation. During the dry season, on the other hand, there is significantly lower electricity demand and diesel consumption, which further decreases with an increased battery size. In January 2017, the harmattan season, PV output dropped significantly and electricity demand as well as diesel consumption were increasing again. This is due to the high aerosol load during the harmattan period. At this time, a lot of dust is brought in from the Sahara and can contribute to a large loss in PV yield locally.
From the results of the modelling study, we conclude that for the design of the components of a PV-diesel-hybrid system various aspect must be considered. In particular, the local seasonality of solar radiation and atmospheric characteristics, which result from regional weather extremes such as rainy season and sandstorms, are important. The design of such a system for the Ghanaian health sector requires appropriate dimensioning – due to its high demands on the system’s reliability. Furthermore, the high number of power outages linked to the insecurity of the power grid has a major impact. Therefore, these specific circumstances should be considered in planning of these systems as well as in the development of suitable control strategies.