Discussion on:

Is zero-emissions air travel around the corner?

I would think the lowering of the cabin noise level would be a huge factor in the success of this plane. Comparative dB levels, anyone?

The noise level is probably the same with am electric car - Very low, like a screwdriver.
The main difference between the noise of a classic car and a classic plane is that the plane engine has a shorter exhaust making it extremely laud. An electric plane doesn't need an exhaust.
Also a piston engine has a lot of pistons and other things witch, when they move they make the engine vibrate and this is not very god for the plane's integrity and for the comfort of the pilot. An electric engine doesn't have pistons so it has less vibrations.
The only huge factor for the success of an electric plane, car ore any other electric vehicle is the price and range and this one has both.

The other difference between a car and an airplane is the propeller noise.

...as I'd love to have a cheap vehicle available for practicing landings. But I think it will be a very long time before this has any commercial application.

The elimination of vehicle emissions, whether talking about airplanes or automobiles, is great but only addresses part of the problem. Natural gas vehicles have zero emissions, but fracking for the gas can create massive methane emissions (not to mention water contamination) on top of the standard emissions from the drilling operations. Electric cars and this solar hybrid plane have zero emissions, but power from gas, coal, and other fossil fuels creates a constant flow of greenhouse gases into the atmosphere. Even nuclear (fission) has emissions from the mining of uranium. Don't get me wrong, we're making progress, but we should do everything we can to avoid mistakes along the way.

Natural gas engines DO NOT have zero CO2 emissions. Not only does every molecule of CH4 oxidise to one of CO2 and two of H2O, but a thermodynamically efficient high pressure engine reaches temperatures high enough to oxidise atmospheric nitrogen.

Nuclear power, per megawatt-hour of energy, has minuscule quantities of fuel in and waste out compared with any fossil carbon.

In contruction, servicing and decomisioning Nuclear is subsidised by the underlying cost structures governed by Energy input, cement and educated operators, scientists and applied technology, all depend on Oil to get there.

I'm not too wildly optimistic about the lifetime of photovoltaic cells, and the disposal of the worn-out ones.
Batteries for electric power will probably need to be quite thoroughly reprocessed when recycled.

With the exception of some used car batteries being dumped on Mexico because of a loophole in NAFTA, over 98 percent of lead car batteries in the US are recycled nearly 100 percent.

I have yet to hear of a decent recycling effort for the high tech batteries in modern EVs.

We will likely end up with landfills being stuffed with them in a 10 years.