On a roll … the lightweight solar solution that can take PV to new places
The race to reap energy from the sun is contested by enormous solar companies all thinking largely along the same lines. They manufacture panels of about two square metres that weigh about 20kg and are roughly 20% efficient.
In the years ahead of us the standard solar panel will slowly reach higher efficiencies, and some companies already make modules that are less than 8kg, but for now the industry seems to have settled on the two-square-metre, 20kg format.
But why not think a little differently? If a less powerful but far lighter alternative can be rolled off the presses like pages of a magazine, why not try it? It could be just the thing for all those places heavy and rigid PV tablets aren’t practical.
That’s what’s happened deep in the corridors of the University of Newcastle, NSW, where a flexible form of lightweight solar panel has been developed and, in July, put to use in a demonstration project in Sydney.
The printable PV technology produces at about 1% efficiency, or about 50Wh a day per square metre. Compared with standard PV panel technology, which can send out about 800Wh*, it’s nothing special.
But that’s not the point, says Professor Paul Dastoor, the director of the Centre for Organic Electronics at the university’s Department of Physics.
In a world focused on replacing polluting sources of energy with clean ones, the flexible, lightweight, totally recyclable PV solution opens up a wide range of new applications.
“A key parameter here is not necessarily efficiency or lifetime; it’s what is the cost of the energy,” Professor Dastoor says. “We don’t need to have very high efficiencies or long lifetimes in order to deliver levelised costs of energy [LCOE] that are very low. We don’t actually gain very much by going to very high efficiencies or very long lifetimes.”
The solar ribbon, if we can call it that, has a target lifetime of one to two years and target efficiency between 1-2%. If it can reach a 2-3% efficiency and a two-to-three-year lifetime, the LCOE will be about 20c/kWh, Dastoor says. At 5-6% efficiency and a five-to-six-year lifetime, the LCOE will reach 11-12c/kWh, “and that is right smack where fossil fuel-based generation is.”
Relative low efficiency or not, if there is plenty of room to literally roll out this energy solution then you’d be silly not to.
A standard solar module might deliver peak power over 300W per square metre, sure, but that will weigh 15-20kg whereas a less-powerful printed PV alternative will weigh about 200-300g a square metre.
The world record efficiency for “organic photovoltaics [OPV]”, to give this tech sector its proper name, is 17% in laboratory conditions. The key challenge, Dastoor says, is how can you achieve higher efficiencies for the same low cost.
“There is a bit of a nuanced argument here, around the complexity of synthesis of those materials,” he says. “If it takes me 47 steps, say, to synthesise those new materials in very complex procedures I’ll never get that cost down low enough to make OPV viable. But the materials we use we make ourselves and we control the entire production chain.”
Expectations for efficiency results between 3 and 4% are at the level where “people are interested in commercial applications of the technology.”
The featherweight nature of the tech makes it a nice solution for vast industrial-zone rooftops that are often structurally designed to guarantee not much more than shelter from the rain. Beyond that, Dastoor is enthusiastic about the prospects for “solar roads” on the shoulders of thousands upon thousands of kilometres of highways.
“We literally roll out these solar cells,” he says. “Now that is an enormous area which then allows those regions to access power right where they want it – so you immediately get energy development of those regions. And those regions include big gaps between our major cities.”
Energy generated this way could be used to charge electric vehicles, purify water and provide lighting, he says. “Easy.”
The solar rolls can be printed on regular presses, like the ones that turn out newspapers, although “it’s really quite tricky getting it to work”.
“We’ve been developing this technology for over 20 years – so, if I was being completely honest with you, I would admit it’s easy and difficult.”
Elements include a printed silver-based ink electrode and copper tape for the busbar. The active layer is an organic semi-conducting blend, a special class of polymer. “We blend them, we print them, and when light is incident upon them, electrons are excited.”
The flexible PV solution is powering interactive public lighting at a recreation park in Land Cove, Sydney, where the panels generate power during the day which is stored in a battery to power the display at night.
The researchers have access to a manufacturing facility at the university’s Newcastle Institute for Energy and Resources, which has been supported by the Australian National Fabrication Facility. The print facility can manufacture hundreds of metres of material a day, although Professor Dastoor says “it’s reached the point where we need to significantly scale this level of production.”
Commercial-scale equipment would be capable of producing kilometres of material a day. “No other renewal energy technology can be manufactured as quickly.”
Other possible uses include disaster relief and the defence industry, floating covers for dams and pools, yacht sails, smart blinds for residential and high-rise buildings, greenhouse covers and more.
Put plainly, Professor Dastoor’s goal is to coat as many surfaces as possible with the material.
“Imagine a world where everyone has access to electricity, and where every surface can generate clean, low-cost, sustainable energy from the sun. That’s a world I want to live in.”
*EcoGeneration’s extremely rough calculation based on four times the output of half a 400W panel.