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NREL: getting the right PV for the job


Dave Williams

In the first of a series of posts related to PV quality research and standards, Dave Williams introduces us to some of the US organisation’s important work in this area…

The National Renewable Energy Laboratory and US Department of Energy is currently conducting some important research that all involved in the PV sector should take note of.

We will cover some of this research in this series of articles, as well as share NREL’s perspective on why it matters so much: the concepts that are being addressed are simple on the surface but when talking about quality it can be difficult to reach consensus.

We start with the importance of designed quality. It is important to recognise that the best-designed product with abundant features is then tasked with manufacturing consistency - when 10 prototypes, become 10,000 a day in production. The work of NREL and DOE will set standards that are adoptable across the industry and international borders, with comfort and consistency.

Stakeholders across the PV industry discuss the philosophy about ‘quality’ and what it means on a regular basis. Quality is universally recognised as something that matters, but defining it is a whole other matter.

Even more challenging is defining PV performance, when the panels are subject to the varied climatic conditions around the globe. National Renewable Energy Laboratory’s Sarah Kurtz has been on a multi-year journey to do just that. She is not alone. She is leading a ten-taskforce team with nearly fifty scientists representing manufacturing, academia, investors, and independent engineers.

This global team has undertaken a detailed and lengthy dialogue to define local stresses, and correlate to expected long-term performance. This is an international, thorough, and complex exercise that will ultimately result in standards that we as a community need to adopt for more confidence in project performance: i.e. making sure projects get the right PV for the job.

PV in varied environments

There is obvious concern that quality may be dependent on the conditions and exposure of panels throughout their lifecycle. So how can we become more confident in ‘these panels’ working wherever a project is built?

There is no doubt that solar projects are now growing to scale in more and varied project environments. NREL’s work will aim to provide a set of tools to the solar community, leading to consistency and investment confidence in new markets domestic and abroad. The investor stakeholders often glaze over as the dialogue starts down a path of thermal mechanical failure or some seemingly obscure engineering speak. But the result is that we should be discounting performance of panels with unknown climatic zone features.

We are manufacturing, selling, installing, financing, and operating plants all over the world with very little data on whether we have the right panel for the job. It is intuitive that different climates need additional testing to ensure that a panel fit for Munich will also work in Bangkok. UV, heat, humidity, and snow are all obvious stresses that will change the expected lifetime, or accelerate degradation. Some panels have additional cross braces that should lower vibration and micro-cracks over a decade of deployment. However, today, this is not easily captured in the performance models that have little data on the field performance of specific modules in particular climates.

These new standards will describe features and not set hurdles of ‘quality.’ Therefore a solar panel that does not have a specific feature is not necessarily a risk to the project or investment, rather may not be qualified for the job.

We need to better understand the risks we are taking. At some price, a panel that only lasts a few years may be acceptable if it is predictable. The challenge that we are facing is ignorance of performance in certain conditions. Will UV actually increase degradation? Will damp heat lead to pre-mature failures? Possibly. Are PV products being commoditised when some perform better in harsh conditions? Absolutely.

This work will help to define panels that are expected to perform well, and help quantify the risk and increase risk-adjusted returns.

Today, we should be discounting performance in ‘harsh’ conditions because of the unknown of running panels harder. The current IEC program should not be considered an absolute performance metric. It is as if we bought an off road car and get frustrated with its track racing abilities. It may be a fantastic car but not designed with features that make it competitive to another environment or it may be great at both. However, never testing it on a track and then taking to Le Mans is simply not logical. We should ensure that the systems we are installing are modeling against a scientific programmatic approach that gives an additional layer of features.

We need a consistent approach to understanding quality and performance in a variety of conditions: standards. Then we can correlate laboratory and field performance to help us understand if we are designing a system without the necessary science in place, and then adjust the standards as failure mechanisms are better understood in new environments.

Features and Benefits of PV panels

It is important to note that this is a feature of the panel, and not a grade of good to bad. A module that is made to work under particular environmental conditions is not necessarily better than another. In fact, we are also likely buying modules that are designed to survive a very wide variety of conditions since there is not a universal testing mechanism.

This universal module may be more costly than required for some environments, and every penny counts. ‘Failure’ is not necessarily an indication of a bad panel; rather a ‘failed product’ lacked a needed feature to survive in a particular location.

NREL’s work should increase awareness of failure modes and likelihood of such failure in particular climates. Manufacturers will be able to lower risk exposure by helping clients select panels with value-add features that best match the conditions and warranty obligations.

This better alignment of risk should ultimately lower install prices, decrease failures, and increase risk-adjusted returns.

Investors should insist on data that supports the panel’s performance in different regions or get guidance on discounting performance. This IEC standard will also help level manufacturers with the endless quest to commoditize panels for price per watt. This work can help give value to these features and not necessarily drive buyers to the lowest cost.

 

 


 

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This article is featured in:
Energy infrastructure  •  Photovoltaics (PV)  •  Policy, investment and markets  •  Solar electricity

 

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