Design and simulation of a grid-conneted PV system in South Africa : technical, commercial and economical aspects

Abstract

The purpose of this thesis is to evaluate the potential and economic feasibility of installing a grid-connected photovoltaic (PV) system at Panthera Africa, located in Overstrand municipality in South Africa. Panthera Africa have several northward facing roof surfaces of limited area and an available ground area. The yearly energy demand is estimated to be around 42.3 MWh. As Overstrand municipality requires PV system customers to purchase more electricity from the utility than they feed back onto the grid on a consecutive 12 month period, the systems are designed to produce 30 - 35 MWh.

Climatic data at the site is assessed by comparing data from local weather station and different databases in order to determine the available solar resource. The yearly global horizontal irradiation is assumed to be between 1709 and 1854 kWh/m^2. The average temperature is found to be 16.9 C, with rainfall mainly occurring during winter months.

PVsyst is used as the simulation software to design and simulate the PV systems. Design parameters such as module orientation, shading, inter-row spacing and loss factors are evaluated. A shading analysis shows that the ground area has the least amount of shading. Shading loss mainly occurs during winter for the ground area and summer for roof surfaces.

A base case simulation is performed using different module and inverter types to find the best performing system. The effect of using optimizers or module inverters to maximize energy production is investigated. The performance ratio is generally higher for ground mounted systems than for roof mounted systems. The best performing system is a ground mounted system having Solar Frontier modules. It produces 31.8 MWh and has a performance ratio (PR) of 84.2%. Using optimizers increases the performance by 0.5%, while module inverters increases the performance by 3.6%, compared to using string inverters. The main system losses are inverter losses and module efficiency loss due to temperatures different from STC. The ground mounted systems have a better correlation between the monthly production and consumption, compared with the roof mounted systems.

Different factors affecting the system performance are investigated in a sensitivity analysis. The analysis shows that a change in irradiation data could increase the system yield by 5%, while changes is soiling loss and the thermal parameter mainly affect the PR. When considering 20 years of ageing losses, the PR decreases by 6 - 9%, depending on the module and inverter used. The irradiance and electrical loss due to mutual shading strongly depends on the inter-row spacing, and increases with decreasing inter-row spacing.

The levelized cost of electricity varies between 1.4 - 1.8 R/kWh in the economical evaluation. The best performing system is not the most profitable. All systems have a negative net present value and a payback time exceeding the lifetime. There are uncertainties in the economical evaluation both in the investment costs and the predefined parameters.

Formålet med denne masteroppgaven er å undersøke potensialet og lønnsomheten for å installere et nett tilknyttet fotovoltaisk (PV) anlegg hos Panthera Africa, lokalisert i Overstrand kommune i Sør Afrika. Panthera Africa har flere nordvendte tak overflater, samt et tilgjengelig bakkeareal. Energiforbruket er estimert til å være rundt 42.3 MWh årlig. Systemene er designet til å produsere 30 - 35 MWh, siden Overstrand kommune krever at PV system kunder må kjøpe mer elektrisitet enn de selger til kraftselskapet over en sammenhengende 12 måneders periode. Værdata fra ulike databaser og værstasjoner vurderes for å bestemme den tilgjengelige solressursen. Den globale innstrålingen er mellom 1709 og 1854 kWh/m2 årlig. Den gjennomsnittlige temperaturen er 16.9 ◦C og nedbør forekommer hovedsakelig om vinteren. Simuleringsprogrammet PVsyst brukes for å designe og simulere PV systemene. Designparametere som modulorientering, skygging, system tap og avstand mellom PV modul rader evalueres. Skyggeanalysen viser at bakkemonterte moduler har de laveste skyggetapene. Skyggetapene foregår hovedsakelig om vinteren for bakkemonterte moduler og sommeren for takmonterte moduler.