The University of Newcastle in Australia has unveiled a 200m2 rooftop solar array made from innovative flexible and printed solar cells that could further revolutionise the global use and manufacturing industry of renewables. According to Professor John Mathews of Macquarie University in Australia, this could be a giant step forward for solar cells. Courtesy Global Green Shift blog
Transparent and flexible enough to coat buildings, vehicles and consumer goods, these third-generation organic photovoltaic (OPV) solar cells are easy to make in large quantities with standard printing equipment, and are based on abundant and cheap materials. The team behind the cells believes the low-cost technology is on the brink of commercialisation and will use the demonstration array to validate calculations that scaling it up to cover buildings over a square kilometre would generate 10MW at a cost of €6.19 million.
At Australia’s University of Newcastle (UoN), a new industrial revolution is being ushered in. It’s based on organic photovoltaic (OPV) solar cells – flexible coatings that can be printed on plastic film or sheets in great quantity at low cost. As such, OPV printed solar cells promise to further revolutionise renewables by making solar cells sufficiently transparent and flexible that they can be coated on buildings, vehicles and daily consumer items.
This is the revolution promised a decade ago by the US firm Konarka – except that Konarka never managed to bring the costs down sufficiently and went bankrupt in 2012. Now, the UoN team led by Professor Paul Dastoor is zeroing in on the costs and looks set to take the revolution forward – and in the process is creating a vast new manufacturing opportunity for Australian firms.
The new focus on costs marks a giant step forward for 3G solar cells
The first-generation (1G) solar photovoltaic revolution has been based on polycrystalline silicon solar cells – which are hard-wired and framed as the original ‘solar cells’. The cells can be connected together into a ‘panel’ and then the panels can be connected into a solar module, which might have a power output of a few kW.
When linked together, they can produce ‘solar farms’ operating at MW and even GW-scale. The technology underpinning such 1G cells is the p-n junction transistor; the panels are manufactured in complex semiconductor processes that call for high temperatures and close manufacturing control.
A second generation of solar PV utilised various ‘thin film’ processes, where a thin film of photosensitive material is deposited on glass, such as gallium arsenide (GaAs), or cadmium, indium, gallium and selenide (CIGS). These 2G solar cells can extract more energy from the sunlight depending on the number of films utilised, to produce hybrid or tandem cells – but they are subject to the same 1G constraint of needing to be deposited on glass, a major cost and flexibility constraint.
The new solar cells
Now, a range of 3G solar cells are able to overcome this constraint by utilising non-silicon-based photosensitive materials and being printed on polymer sheets (plastic), which makes them light, flexible and low-cost.
The outstanding contenders in this emerging 3G solar cell field are, firstly, the inorganic cells made from perovskite materials (abundant, cheap, but not yet sufficiently stable for mass utilisation) and secondly, organic polymer cells, where the photosensitive material is based on carbon molecules, such as those utilising the fullerene lattice.
These organic solar cells have great promise because the photosensitive material can be formed into an ‘ink’ and deposited at low temperature over a large area of cheap plastic (polymer) through a conventional printing process.
It is these printed, flexible organic solar cells that are being developed by Professor Dastoor and his team at the University of Newcastle, in the Priority Research Centre for Organic Electronics and in the neighbouring Newcastle Institute for Energy and Resources (NIER). A key feature of the OPV cells is that they have no toxic ingredients, as compared with some of the alternative inorganic solar cells being developed.
They can print these organic photovoltaic solar cells for less than €6.19 per square metre – because the process is not complex, uses abundant and low-cost materials and can be accomplished with standard printing technology
The difference between what is being done at Newcastle and what was accomplished by Konarka a decade ago is the new focus on costs, to keep the cost of the various fabricated photosensitive materials as low as possible. Professor Dastoor hosted a visit from the Global Green Shift blog this month, and explained how the new focus on costs marks a giant step forward for 3G solar cells.
This will partly be a function of scale of production, but partly also the judicious choice of materials involved. The whole process does not have to utilise the semiconductor fabrication techniques that have made the process of producing 1G and 2G solar cells so complex.
At this stage, the Newcastle team is concerned with creating a workable prototype of a functioning solar PV array. This has been accomplished, in a world-first 200m2 array erected on the roof of an industrial complex near Newcastle, by the bulk liquids and containers firm CHEP.
How do 3G OPV solar cells perform? First, the costs. Professor Dastoor and his team reckon that they can print these OPV solar cells for less than AU$10 (€6.19) per square metre – because the process is not complex, uses abundant and low-cost materials and can be accomplished with standard printing technology.
Scaling up to commercial quantities, of the square-kilometre range, the costs would be less than €6.19 million per square kilometre. That would be enough to cover several blocks of city buildings with their own power generators. How much power could such a city-based building-integrated OPV solar plant generate?
Let us scale the CHEP prototype up through calculation to see what could be accomplished. Working from the insolation received at the earth’s surface of 1000W/m2, and assuming an unrealistically low level of conversion efficiency of 1%, would mean that the OPVs would produce power at a rate of 10W/m2. Scaling this up (and assuming effectively no limit to the availability of polymer substrate for the OPVs) would mean that a system could produce 10MW from a sheet 1km2 in area.
Professor Dastoor considers the sweet spot for this technology to be around 20-30MW/km2, where (according to his group’s calculations) the OPV would deliver electrical energy at a levelised cost of 20 Australian cents (about €0.123) per kWh. So efficiency in sunlight conversion would only need to be improved two to three times to achieve such a sweet spot – something which is actively being investigated by the Newcastle group.
Professor Dastoor calculates that if a large area of OPV could produce power at the rate of 50-60MW/km2 (raising the conversion efficiency five to six times) then power could be produced at a levelised cost even lower at around 10-11 Australian cents per kWh (about €0.062-0.068) – highly competitive with present costs of power produced by burning fossil fuels.
So the key cost and power parameters are as follows. A printed OPV solar cell would cost less than €6.19 per square metre, which would scale to €6.19 million per square kilometre – enough to cover several blocks of city buildings. Power would be generated at 10W/m2, or scaled up at 10MW/km2.
So a city block of several buildings could be producing its own power at 10MW at an installation cost of less than €6.19 million. A key target for research at UoN would be to validate these calculations with actual observations of the power and energy generated by the experimental array installed at CHEP.
Producing fresh vegetables
Let us explore the potential applications of this emergent technology. Consider the case of a food production system producing fresh vegetables under glass, and utilising only renewable energy for the desalination of seawater and water circulation through the greenhouses – which is the model of food production perfected in Australia by Sundrop Farms.
Now, Sundrop Farms currently uses a concentrated solar power (CSP) plant utilising 23,100 heliostats and a 127m ‘power tower’ – all of which is working perfectly adequately.
We have an obvious multi-million R&D project to propel Australia to the forefront in next-generation OPV printed solar cell technology
How would utilising transparent printed OPV solar cells change things? The calculations above reveal that organic solar could deliver the same result, if scaled to a 1km2 OPV array. The Sundrop greenhouses cover an area of 20 hectares (or 0.2km2), so allowing for OPV to cover the sides and roof area of the greenhouses would call for photosensitive material covering an area of 0.3km2.
Three such farms, able to produce 45,000 tonnes of fresh tomatoes per year, would call for 1km2 of OPV – which could easily be scaled up from the existing demonstration ‘strip’ of 200m2.
Professor Dastoor considers this scaling up to be entirely feasible, given the ease of printing and producing the photosensitive materials. The power produced by such a 1km2 OPV operating at 10MW would be ample to power the desalination plant and pumping systems involved in running the farm. Here we have an obvious multi-million R&D project to propel Australia to the forefront in next-generation OPV printed solar cell technology.
It is the potential manufacturing possibilities raised by the OPV approach that are of great interest to the Newcastle team. There is a range of possibilities associated with OPV solar cells, utilising different materials and different fabrication methods. There is as yet little international competition – but that could be expected to change as word gets out that OPV is on the brink of commercialisation.
China changed the global 1G solar cell industry in less than a decade, becoming world leader from a standing zero start, and is now addressing the 2G solar cells revolution (through companies such as Hanergy). There is enormous potential in China for a 3G solar cell industry – and great potential for the companies, and countries, that can supply the technology.
Australia missed out on the 1G and 2G solar cell industrial revolutions – not for want of trying. (Remember Pacific Power, with its efforts to commercialise 2G solar cells developed under Professor Martin Green’s leadership at the University of New South Wales? Now there is another possibility presenting itself with 3G solar cells.
There is enormous potential in China for a 3G solar cell industry – and great potential for the companies, and countries, that can supply the technology
To become a player, Australia would have to move rapidly from the lab-based research currently being demonstrated at the University of Newcastle to industrial-scale demonstration – involving assessment and evaluation of kilometre-scale OPV material printed on commercial-scale printers adapted from the newsprint industry.
Such a scaling-up needs to be fashioned by strong government leadership, with a clear focus on the value chain of materials supply that leads to the end product of the OPV solar cell and to its diffusion. Strong government leadership is, of course, what has been signally lacking in Australia as the country navigates the energy transition away from fossil fuels. Now, here is a chance for a different outcome.
John Mathews is professor of strategic management at MGSM, Macquarie University. This article was first published on Mathews’ Global Green Shift blog and is republished here with permission.