|Cycle 3 (2014 Deadline)
PRESSA: Photovoltaic Reliability Evaluation in Sub-Sahara Africa
PI: Gabriel Takyi (email@example.com), Kwame Nkrumah University of Science & Technology
U.S. Partner: Christiana Honsberg and Mani G. TamizMani, Arizona State University (ASU)
Project Dates: September 2014 to August 2016
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; encapsulant 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.
Summary of Recent Activities
During this reporting period, a lot of time was spent on gathering further data and information to address the concerns of reviewers of two of their papers. The two papers are:
1. Correlation of Infra-Red Thermal Imaging Results With Visual Inspection and Current-Voltage Data of PV Modules Installed in Kumasi, a Hot Humid Region of Sub-Sahara Africa
2. Photovoltaic modules for sub-Sahara Africa ambient: Technology, degradation factors and R&D challenges
Two students on work placement from the University of Energy and Natural Resources (UENR) Sunyani, Ghana, and five teaching assistants were involved in the data gathering to address the reviewers concerns.
The main activities involved can be summarized as follows:
- Use NREL checklist in the visual inspection of PV modules to identify defects
- Take IV Curves of selected PV modules
-Take IR images of selected modules
- Correlate the above results in order to evaluate the effect and rate of degradation
With regards to the PhD work on modeling of PV solder joint, they discovered a limitation in terms of computing power that is required for modeling the solder joint. Additional financial support is being provided from one of their projects to allow them upgrade the system. They have placed an order for computer accessories that will help improve the power of the workstation.
PEER Cycle 3 Grant Recipients