Electronics as paint can be dangerous

8th July 2020
Alex Lynn

You do not give a car battery to your children. It is dangerous. The same caution must be exercised as energy harvesting and storage arrives as electronics as paint. For example, a precursor of this is the InfinityPV adhesive solar tape you cut to any length, this determining voltage and power output.

The company cautions that, ‘These solar cells build up potentially lethal voltage for lengths above ten centimetres depending on the layout. You need to download, sign, and send us the customer awareness declaration form before we can ship this product to you’. However, properly used it is an excellent product.

As they say, it can be applied to rods, window blinds, window frames, glass, UAV drone / RC airplane wings, cabinets etc. wherever you would like and where you might have a need for power. The solar tape is ideal for solar energy integrators, sensor devices, Internet of Things, electronic projects, makers, and DIY hobbyists. Their converter board lets it charge batteries and provide USB output.

No more components-in-a-box. Welcome to the new world of structural electronics and electrics as multifunctional load-bearing material and protective and decorative film. It is detailed in the overview IDTechEx report, ‘Smart Materials Opportunities in Structural Electronics and Electrics 2020-2030’.

Now electrically-active paint is on its way. There are research programs on photovoltaic paint that is variously organic, quantum dot and perovskite PIN junction photovoltaics. Like supercapacitors and batteries planned as paint, the cell voltages and currents are mainly low, but connections can produce something dangerous.

Spray-on thermoelectrics may be another breakthrough. 72% of global primary energy consumption of around 160,000TWh is lost as heat. Much of this is at a temperature above 100°C where fit-and-forget thermoelectrics could, in principle, covert a valuable few percent into electricity. 

Unfortunately, thermoelectrics generating more than a few kilowatts are a commercial failure – too high cost per watt. That is partly because getting close thermoelectric contact with hot metal chimneys, pipes and exhausts has been difficult. Today’s collar design is usually inadequate given that thermoelectrics start by being among the most inefficient energy harvesters.

Cold spray to the rescue?

Cold-spray involves introducing tiny metal particles into a supersonic gas and slamming them onto a metal surface. The impact converts them into seamless coating, but they must be malleable materials. However, in 2020, the US Energy Department’s Lawrence Livermore National Laboratory partnering Thermoelectric Technologies reported, 

‘The team concluded that cold-spray deposition can fabricate bulk pieces of thermoelectric bismuth-telluride on a wide variety of substrates, without loss of structural integrity, demonstrating that cold-spray is a viable alternative to traditional manufacturing approaches for thermoelectric materials.

‘The sprayed material has a randomly-oriented microstructure largely free from pores (> 99.5% dense), and deposition is achieved without substantial compositional changes. The Seebeck coefficient and thermal conductivity are largely preserved through the spray process, but defects introduced during deposition significantly increase electrical resistivity. Defects can be removed, and compressive strain relaxed by a post-deposition anneal, which leads to Bi2Te3 blocks with a typical ZT of 0.3 at 100°C’.

IDTechEx believes this may be a route to a large market creating ten to 50kW levels of ‘free’ electricity in industrial plants and maybe the largest diesel gensets, both new and by retrofit. It is unlikely to be cost-effective in the ever-cooler exhausts remaining in cars. It is not appropriate for home improvement so fortunately, your children will not be using it.

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