Could sun-sensitive paints replace old school solar panels to give electric boats and cars unlimited range?

The relentless push toward the electrification of items using internal combustion engines has driven the fastest rate of technological development since the space race of the 1960s.

Our world now includes new electric cars, new electric lawn mowers and new electric boats, all promising a more sustainable future without coughing out any of those nasty greenhouse gas emissions.

But what we still don’t have is a real answer to nagging concerns over range. For all their advances, electric vehicles are still tied to the limitations of today’s battery technology and a significant lack of charging infrastructure – especially once we leave the urban city core.

It is this range anxiety which represents the single greatest barrier to further adoption. I mean, it’s one thing to run out of battery power when you still have a narrow strip of lawn to mow on the far side of the patio. It’s quite another when you run out of juice six kilometres from shore.

Some boatbuilders have tried to address this by covering external surfaces of their vessels with solar panel arrays, with the idea of being able to charge the batteries on the fly.

It’s a good idea, but one that comes with its own share of caveats given that solar panels are bulky, heavy and awkward to install over the gracefully curved surfaces of modern boats, limiting the amount of real estate over which they can be applied.

But a new range of solar paints now under development could offer a better alternative to keeping the batteries of electric vessels from running flat.

Photovoltaic paint
Photovoltaic paint is paint capable of harvesting solar radiation and turning it into usable energy. It’s still in its early development stage but it has the potential to allow boatbuilders to turn an entire boat – hull, decks, superstructure, even fixtures like cup holders and railings – into a single, continuous power-generating surface.

Photovoltaic paints eliminate the need for bolt-on solar panels altogether, while vastly increasing the amount of surface area that can be used to generate power. Potentially, enough that an electric boat might never need to be plugged in at all.

Photovoltaic paint isn’t an entirely new concept, but in our relentless push toward the electrification of just about everything, it’s clearly been fast-tracked for development. In fact, there are no less than three separate solar paint technologies now emerging, with each offering its own unique advantages.

Perovskite
Perhaps the first photovoltaic paint technology to appear was Perovskite, which gained the nickname ‘spray-on solar.’ The paint is infused with dust-sized crystals composed of calcium and titanium oxide, which give it its solar sensitivity. A wire leads from the painted surface into a transformer, then into a battery pack, just as with a traditional solar panel.

Named for Russian mineralogist Lev Perovski in a nod to its unique mineral content, the technology was initially developed by research teams working independently both in Japan and in the UK at the University of Sheffield, where the world’s first successful spray-on solar panel was created in 2014.

A more recent champion of the technology has been the US Department of Energy’s National Renewable Energy Laboratory, which in 2018 published a paper supporting the continued development of perovskite. Researcher Kai Zhu says the manufacturing cost of perovskite paint is comparatively low, while its charging performance approaches that of traditional solar panels.

The disadvantage, to perovskite photovoltaic paint, for now at least, is an inherent sensitivity to moisture. That’s obviously a big problem for its use on boats, or even on electric cars that will inevitably see the odd rainy day. Current research is focused on developing varnish-like sealing topcoats for the paint that protect it from moisture without degrading its power-generating potential.

Quantum dot solar cells
Developed by Canadian researchers at the University of Toronto, Quantum Dot solar cell technology is a photovoltaic paint that uses nanoscale semiconductors instead of perovskite crystals to capture light and turn it into electric current. Replacing natural minerals in the formulation eliminates any need to mine the paint’s core ingredient, in keeping with its promise of greater sustainability overall. Best of all, Quantum Dot paint doesn’t suffer any sensitivity to moisture and is extremely fine in composition, making it easier to use in spray guns.

Quantum dot solar paint offers a number of other advantages as well, including being nearly as efficient at generating power as traditional solar cells, and comparatively cheap to manufacture.

University of Toronto researcher Susanna Thon says that flexibility is yet another key asset to the Quantum Dot technology. “The main advantage is that by simply changing the size of the quantum dot, you can change its light-absorption spectrum,” she says. “These dots could end up being up to 11% more efficient than traditional solar panels.”

Hydrogen solar paint
A third approach to harvesting power through painted surfaces is currently under development by researchers at the Royal Melbourne Institute of Technology in Australia.

Where Perovskite and Quantum Dot paints directly harvest solar radiation and drive it into a battery to power an electric motor, hydrogen solar paint absorbs moisture from the air, and uses solar energy to split the vapour into its core components – hydrogen and oxygen.

Oxygen is simply released into the atmosphere while the hydrogen can be directed into a fuel cell and used as clean energy. Or, alternatively, burned in an existing ICE engine that has been mechanically modified to burn hydrogen rather than petrol or diesel. Proponents of the technology say the comparative ease and low cost of modifying an existing pool of engines worldwide to use a new fuel – rather than requiring their complete replacement – is what gives the technology a winning edge.

“Our new development has a range of advantages,” says lead researcher Dr. Torben Daeneke. “You don’t have to be over water. Any place that has water vapour in the air, even remote areas far from water, can produce fuel.”

The advantage of solar coatings
All three photovoltaic paint technologies share some common attributes, including the ability to be easily applied over a variety of surfaces, including those with curved or complex shapes, making them a natural fit for use on boats and cars.

As a result of this broader application, the paints allow a boat to generate far more power than it ever could with traditional solar panels mounted to the roof because the entire vessel can be used to generate electricity, rather than just a portion of it.

That includes the side walls, narrow frames around windows, and any other spaces where mounting a traditional solar panel would be difficult or impractical. Realistically, that’s most of the surface area on any boat.

Of course photovoltaic paints have enormous potential uses on more than just boats, with electric cars being obvious – exactly why automakers worldwide are pouring money into the development of photovoltaic paints.
But it doesn’t stop there. At the end of the day, we’re talking about paint. Looking beyond the obvious, virtually any exterior surface could be coated with the stuff and used to generate power. Think buildings, bridges, road signs, parking meters … the long-term implications could be huge.

And just to think, this all started with electric boats.

While we’re not yet at the point where we should rush down to the chandlery and load up on brushes and rollers, a new wave of technological evolution is clearly on the horizon. Get ready, because the future has never looked brighter.

Windows too

It isn’t just boat exteriors that hold potential to generate solar power. Researchers in the US are also exploring ways of using window glass to help turn sunlight into usable energy.

Photovoltaic glass could prove to be a game-changing technology with the potential to vastly increase the scope of solar power overall. But the very concept of a solar panel window is counter-intuitive, because where traditional solar panels are designed to capture light, windows are designed to transmit it.

That’s why ground-breaking research being conducted by a team at Michigan State University (MSU) is attracting the attention of scientists in the energy sector all around the world.

The MSU team has successfully produced what it describes as the world’s first fully transparent glass panel with the capability of harvesting solar energy. Described as a transparent luminescent solar concentrator, or TLSC, the window absorbs solar radiation while allowing visible light to pass through by incorporating organic salts into its chemical formula.

The salts absorb specific invisible UV and infrared wavelengths and convey that energy to a thin photovoltaic cell positioned along the window edge, which converts the energy into electricity. The resulting current can then be either directed into a battery bank or tapped to power onboard equipment.

The researchers estimate that with today’s technology, a commercially manufactured version of their TLSC could deliver an efficiency of about 10%. While that lags behind the 15% – 18% average efficiency of current commercial solar arrays, it’s more than enough to be transformative in view of how much surface area on an average yacht is represented by glazings.

Back on Terra Firma, solar windows installed on homes or office buildings could generate significant levels of power, and only drive further investment to make solar windows even more efficient.

The MSU researchers note that their transparent luminescent solar concentrator is a glass product, distinguishing it from existing solar films and coatings already on the market.

The TLSC, they say, outperforms coatings by having the ability to be formed into windows of varying sizes, shapes and curvatures. With the photovoltaic elements incorporated into the glass itself, the TLCS product is not subject to damage from scratching or peeling, allowing its use in power windows and sunroofs.