Why we have big plans for PV testingPosted: Wednesday, 15th February, 2012
There are some things we need to discuss
The comments section in a local newspaper is always an interesting thing to read – particularly when people are responding to an article about one of our projects. So when the Newcastle Herald published an article just before Christmas about CSIRO’s new research funding for testing the performance of solar panels, I returned a few days later to skim the comments and see what people were saying.
(A quick summary of the news article for those who don’t have time to read it in full: CSIRO has new research funding from the Australian Solar Institute to improve our knowledge of how photovoltaic (solar) panels perform under real-world conditions. The funding will be used for some new equipment to improve the way we make our measurements, plus a project to study how different types of PV panel perform under the typical variations in sunlight and temperature that occur throughout the day and the year. Accurate information of this type is becoming more and more important as Australia moves toward larger PV projects like the Moree Solar Farm.
One of the comments left under the newspaper article raised a very good question: Why is it worth spending research money on understanding photovoltaic performance? Shouldn’t we just be devoting all our effort to improving that performance?
It’s an excellent point, and one that I’ll address here in this post. I’ll try to explain why understanding PV performance is actually very important – and how (as was asked by other commenters on the same article) this work will benefit Australian companies, the Australian public, and the environment. Then, over the next few weeks, I’ll have a go at explaining exactly what we’ll be doing and how it all turns out to be quite interesting.
What you probably already know
Accurate testing and certification helps you avoid getting scammed when buying a product. It’s how you can be sure there’s real paracetamol in your headache tablets, that there are no dangerous contaminants in your drinking water, and that your 1.5 kW rooftop solar panel can actually produce 1.5 kW of power. Manufacturers who certify their solar panels to international standards have to regularly send samples to laboratories which can confirm their performance, and these labs themselves have to be regularly certified to make sure they’re accurate. This sounds reasonably straightforward. So why does a research heavyweight like CSIRO need to be involved?
It’s because things aren’t as simple as they seem.
The perils and pitfalls of PV performance prediction
Let’s say you’ve just had 1.5 kW of solar panels installed on your roof. It’s the middle of a clear and sunny day and the sun’s rays are hitting your panels head-on. But even under these perfect conditions you’re only getting, say, 1.3 kW of power. This makes you upset. Hasn’t it been tested in a fancy lab that confirmed its performance? What’s going on?
Well, one thing that’s probably happening here is that the certification was done in a lab at 25°C (because that’s what the standard says to do), but on your sunny rooftop the panels are likely to be much warmer – around 50 to 60°C. Why does this matter? Because for silicon cells, the efficiency (the ratio of electrical output to solar input) decreases as the temperature of the panel goes up. The information you were given by the manufacturer might have specified how strong this effect was expected to be – it’s often referred to as the power temperature coefficient – but anyway, temperature is just one of the factors that affect PV performance.
Three other important factors will also affect the output of your PV system as the sun moves through the sky during the day. These are (i) the intensity of the light from the sun, (ii) the angle of the sun’s rays incident upon the PV cells, and (iii) the spectrum (or colour mix) of the sunlight – for example, whether the sun is orange, like at sunrise and sunset, or contains lots of ultra-violet light, as in the middle of the day. These changing parameters combine in a complex way to influence the amount of energy your PV panels will generate over the course of a day, and over the year.
And just to make things more confusing, different types of PV panel respond differently to these changing parameters. Some PV types are less affected by temperature, and some hold their performance better on cloudy days. Just how these issues combine with the weather patterns for a particular location is not yet well understood, even with the modest range of PV technologies on the market today. And with new technologies such as the dye-sensitised solar cell and the organic solar cell on the horizon, the standard methods for predicting energy yield need to be updated and improved. A good standard method for energy yield prediction will help consumers understand what they are buying, prevent manufacturers from making unrealistic claims about the performance of their panels, and help Government direct research funds to technologies that can bring the most benefit.
The multi-million dollar issue
Of course, the issue grows with the size of the PV system you want to build. Now imagine that instead of buying eight panels for your roof, you’re a large company trying to get financial backing for a 750,000 panel photovoltaic power station. Even small errors in the output predictions could mean a difference in earnings of hundreds of thousands of dollars per year. Without an accurate understanding of the return on your investment, it’ll be very difficult to convince a bank to lend you money to build the solar field.
What we’re doing about it
In order to ensure the best possible outcome for this important project, we’re partnering with some world-leading organisations:
Scientists at the US Dept. of Energy National Renewable Energy Laboratory (NREL) have been working in this field for nearly four decades. They maintain the world’s leading PV test laboratory and will contribute know-how, as well as the use of equipment that would simply be impractical to install in Australia.
The Desert Knowledge Australia Solar Centre outside Alice Springs is the premier outdoor test facility for photovoltaic systems in Australia. Our collaborators there will help us ensure our new outdoor facilities are as good as they can possibly be.
Major property developer Lend Lease will bring great value to the project, based on a wealth of experience constructing large PV installations.
Why everyone benefits
As they say, knowledge is power. Our research will provide a clearer understanding of the way PV systems perform, particularly under Australian conditions. This will reduce the risk for large projects in Australia, improving the likelihood of financial backing. The flow-on is the encouragement of more manufacturing, which will bring prices down, encouraging more solar power plants… and so on. We see this research as an important step along the path to renewable energy that Australia (and indeed the world) will need to take if we’re to avoid harmful climate change.
The facilities will also enable some important new research, including studies of the durability of solar panels (an important factor when considering the economics of the up-front cost). The facilities will also provide a place where Australian scientists and developers of new PV technologies can have their products tested. This will greatly reduce the risk, the cost and the time involved when compared to sending these devices overseas for testing.
And so, hopefully all that goes some way to addressing any uncertainty about why we’re doing what we’re doing. For more details about exactly what we are doing, stay tuned to the blog – I’ll be giving more information on our individual projects over the next few weeks.