PRESSA: Photovoltaic Reliability Evaluation in Sub-Sahara Africa

PI: Gabriel Takyi (gabrieltakyi@yahoo.co.uk), Kwame Nkrumah University of Science & Technology
U.S. Partner: Christiana Honsberg and Mani G. TamizMani, Arizona State University (ASU)
Project Dates: September 2014 to February 2019

Many countries are procuring and installing large numbers of photovoltaic (PV) modules for various grid-tied and stand-alone applications. These modules need to be evaluated to ensure that they will meet the safety requirements (both electrical and mechanical), meet the nameplate rating requirements (rating tolerance shall be minimum), and be reliable and durable for at least 20 years. Because consumers decide to purchase modules based on their "$/watt" ratio as per the nameplate rating, it is critical to ensure that the rating is accurate. In this PEER project, the nameplate rating will be verified by the principal investigator's laboratory in Ghana before procurement decisions are made by investors and the government of Ghana.

The lifetime of PV modules is dictated by failure modes and degradation rates. PV module manufacturers typically provide 20-year warranties, but there are two problems. First, due to the dynamic nature of the investors’ decisions, many manufacturing companies do not last longer than a few years, rendering the 20-year warranty useless. Second, most manufacturers provide a 20-year warranty due to heavy competition in the industry but do not have substantiated evidence to justify these long warranty periods. Based on the experience gained in the U.S. partners' laboratory at ASU, it has been demonstrated that the majority of modules do not meet warranty requirements, and most manufacturers are no longer in business to make good on warranty claims when they are made. Three of the major failure/degradation modes in the climatic conditions prevalent in Ghana are solder-joint degradations/failure; encapsulate browning; and high relative humidity/rain-related degradation. In this PEER project, samples of PV modules will be evaluated for the above failure and degradation modes both in the field and the laboratory.

Two major impacts are expected with regard to purchasing decisions by various stakeholders, including the government of Ghana and Ghanaian investors and consumers. The first impact is related to nameplate rating verification. The stakeholders can purchase the modules based on their independently measured power provided by the Ghanaian researchers rather than their manufacturer rated power. The second impact is related to the lifetime of the modules in the field. An extensive evaluation of PV modules is required to predict module lifetime under various climate conditions. In the proposed limited-budget PEER project, the entire lifetime-related research cannot be performed, but a few key reliability studies will be carried out in the laboratory and in the field to identify the major failure modes using less expensive, non-destructive tests.

Final Summary of Project Activities

This project has come to an end. The data collected so far under PRESSA provides compelling evidence that some of the PV modules that are imported do not perform as expected based on the manufacturers’ nameplate ratings. The Ghanaian consumer (including individuals, government agencies etc.) and other stakeholders must be aware of this through the demonstration of their research findings. For instance, research on risk priority number (RPN) of a 2.5 MW solar power plant in Northern Ghana indicates that after only five years of operation, the rate of degradation has exceeded the rate that is expected in 25 years. These results will be presented to the Volta River authority, the operators of the plant. They have been able to show the performance in terms of prevalent degradation and rate of degradation of different PV technologies installed at different climatic zones (Tropical Savannah and Semi-Arid Zones) in Ghana.

The project's potential development impacts include:

1. Prediction of life of PV modules installed in SSA using accumulated strain energy density from the modelling of solar PV interconnections.
2. The prevalent defects of PV modules installed in the tropical savanna and semi arid climatic zones in Ghana have been identified. This could be of great benefit in product development.
3. The use of climatic condition (temperatures of KNUST) has helped generate a temperature profile representative of sub-Sahara Africa. This Information will be useful for manufacturers in the design of robust crystalline silicon PV modules. 

The PI and his team will continue to collaborate with the US Partner on both current and new research. KNUST is currently partnering with ASU on MasterCard Accelerated Masters Degree Programs (3+1+1) in mechanical engineering, biomedical engineering and business programs. Under this program, ASU will be training up to 150 KNUST students for 5 years. The US partner has agreed to take some of the students to do their projects in his laboratory at ASU Polytechnic.

Publications

Nyarko F., Takyi G., Amalu E., Adaramola M., Generating temperature cycle profile from in-situ climatic condition for accurate prediction of thermo-mechanical degradation of c-Si photovoltaic module, Engineering Science and Technology, an International Journal, Volume 22, Issue 2, 2019, Pages 502-514, ISSN 2215-0986, https://doi.org/10.1016/j.jestch.2018.12.007.

Takyi G. Correlation of Infrared Thermal Imaging Results with Visual Inspection and Current-Voltage Data of PV Modules Installed in Kumasi, a Hot, Humid Region of Sub-Saharan Africa. Technologies. 2017; 5(4):67. https://doi.org/10.3390/technologies5040067



PEER Cycle 3 Grant Recipients