Potential induced degradation (PID): a test campaign at module level

By J. Carolus, Hasselt University and imec vzw; M. Daenen, Hasselt University and imec vzw

Potential induced degradation (PID) of photovoltaic (PV) modules gets a lot of attention since 2010 when Solon published their findings about a degradation mechanism in their PV modules caused by high potential differences. When multiple PV modules are connected in series, a potential difference up to 1000 V or at some places even 1500 V is created between the cell and the grounded frame. This electrical field causes a leakage current and ion diffusion. PID is a multi-level degradation with causes and solutions at cell, module and system level. A test campaign was conducted within the frame of a feasibility study for pidbull, a curing technology for PID developed by pidbull nv. 80 PV modules were characterized whereof 49 PV modules were stressed and cured for PID. The selected set of PV modules was composed of 49 different module types of 33 brands. The test was done according to the foil-method, as described by the standard in progress IEC 62804. However, to apply higher stressing and curing rates, the modules were tested with an aluminium foil inside a climate chamber for 96 hours. After the stress test, only 22% of the tested modules passed the 5% loss criteria as described by IEC 62804. In other words, 78% out of a set of today's most installed PV modules in Flanders are PID sensitive. Remarkable is that only 16 out of the 49 PV modules have less than 20% PID after the stress test. Additionally, a linear trend for PID reversibility was shown for modules with a stress level of less than 85%. The modules which lost more than 85% due to PID showed a lower recovery rate or in worst case didn’t recover at all.

Preventive O&M - Maximising PV plant availability

By Arnoud Klaren, Arnoud Klaren is Foresight’s senior portfolio manager and technical director for UK and Spain. He joined Foresight in 2011 from SolFocus, where he spent four years managing solar projects in Spain, Saudi Arabia and Greece based on concentrated PV technology. Prior to SolFocus he founded and managed ThinkSpectrally, a spin-off company of the University of Valencia in Spain, dedicated to quality assurance in PV manufacturing.

Asset management | As one of the biggest utility PV owners in the UK, Foresight has extensive experience of getting the most out of operational solar plants. Its technical director Arnoud Klaren draws on some of the lessons the company has learned from minimising the risks that affect solar projects over their lifetime.

New approaches to solar O&M in China

By Karl Hong Wan, Karl Hong Wan attended the graduate school of Southeast University in China, majoring in electrical engineering, power system measurement and intelligent instruments. He has been engaged in the design, construction and operation of power substations, power plants and renewable energy generation for 30 years. He currently works in the design and research institute of GCL New Energy

Operations & maintenance | Proposals by Chinese authorities to scale back the subsidies available for grid-tied PV will require new efforts to maximise the performance of power plants. Karl Hong Wan of the GCL Design & Research Institute explores some of the innovations in O&M practices that will help China’s solar industry cope with decreasing financial support.

Mobile revolution

By Sara ver Bruggen

The past two years have seen a boom in the deployment of mobile PV testing laboratories. Sara ver Bruggen reports on how technological advances are helping investors and developers in new and emerging solar markets get the best from their assets.

All about PID – testing and avoidance in the field

By Peter Hacke, Senior scientist, National Renewable energy Laboratory; Steve Johnston, National Renewable Energy Laboratory

Potential-induced degradation can cause significant power loss in modules if the appropriate precautions are not taken. In the first part of a new series in PV Tech Power on module failure, Peter Hacke and Steve Johnston assess the current state-of-the-art in detecting, avoiding and mitigating the worst effects of PID.

Solar O&M grows up

By Ben Willis, Solar Media

The European solar industry has followed the lead taken by its counterparts in the US by developing best practice guidelines for the burgeoning O&M business. Stefan Degener, senior director of O&M at First Solar, who led a group to develop the guidelines, speaks to Ben Willis about their significance and aims.

Why standardisation in O&M is key to PV’s future

By Vassilis Papaeconomou, Alectris, Managing Director

The maturing of the solar operations and maintenance business has shone a spotlight on the need for some universally accepted standards and practices across the industry. Vassilis Papaeconomou explains why such a step forward will be vital to ensuring the full value of solar assets is realised.

Proactive monitoring in effective PV asset management

By Edmée Kelsey, 3megawatt; Gwendalyn Bender, Vaisala

Datasets from multiple sources allow PV power plants to be monitored more closely than ever before, but how best to use this data is another ball game. Edmée Kelsey and Gwendalyn Bender look at how data should best be stored, managed and mined for effective solar asset management.

How O&M contractors can deal with issues in newly and recently built PV plants

By Vicente Parra & Gorka Oña, Enertis

With either newly built PV plants or plants in operation for a couple of years, an O&M contractor may face a series of issues related to the plant’s design and construction, the quality of the equipment and parts, and warranty claims. Vicente Parra and Gorka Oña highlight some of these issues and recommend how O&M contractors can address them.

PV plant design and SCADA programming

By Marcos Blanco

The optimal incorporation of SCADA systems into a PV power plant can have a significant bearing on the profitability of a project. Marcos Blanco looks at how the layout and design of a PV system can best be configured to optimise a project’s performance.

How soiling and cleaning impact module performance in deserts

By Nicoletta Ferretti; Juliane Berghold

In recent years the number of PV installations in desert regions has increased, and a regular cleaning of the modules in these areas is necessary because of energy yield losses due to soiling. Investigations carried out by Nicoletta Ferretti and Juliane Berghold at PI Berlin, however, suggest that the stress caused by the cleaning procedure employed potentially affects the module performance during its lifetime.

A global approach to solar O&M

By Florian Danner, Managing Director, Conergy Services; Jens Kahnert, Managing Director, Conergy Services; Bjarn Rose, Senior Manager, Conergy Services

Operations and maintenance | The distribution and growing size of PV fleets mean new approaches to plant operation and maintenance are needed. Florian Danner, Jens Kahnert and Bjarn Röse of Conergy Services outline the key ingredients for cost-effective O&M in a globalised industry.

Testing times

By Ben Willis, Head of Content

On-site testing | PV project owners are becoming increasingly conscious of the need to understand how their plants are performing in the field. Ben Willis explores how mobile testing units are emerging as an important tool in the early detection of faulty module equipment.