1. A PV-powered engine for your car? No, this doesn't involve putting solar panels on your car's rooftop. Instead, these researchers at MIT have been looking into the idea of a white-hot filament heated by fuel, along with a filter for the light and a thermophotovoltaic electricity generation system, to provide electric power for your car. It's analogous to some hybrid vehicle designs (so-called "series hybrids") which run a small internal combustion engine (running at constant, and thus more efficient, speeds) simply to charge up an electric drivetrain's battery system instead of directly driving the wheels. Thus, this is essentially a way to enable efficient electric-powered vehicles with much longer range than currently available options by using fuel, instead of batteries, as the primary energy storage. The real innovation here appears to be the use of a filter to only allow useful wavelengths to pass through to hit the thermophotovoltaic device, while others are reflected back onto the filament to heat it up even further...
In the end, these "build a better engine" ideas come down to several factors: a) how efficient is it; b) how reliable is it; c) how expensive is it; and d) how much of a frightful transition would it require for the auto makers, drivers, and the rest of the transportation value chain. (Of course, for investors there are even more factors such as the management team, valuation, etc. But I digress...)
As to the first factor, efficiency, below is a picture courtesy of the DOE showing where the energy from gasoline in your car actually goes -- while only 15% of the energy goes toward doing things you want (making your car go, running the A/C), only about 60% of the energy is lost due to inefficiencies in the internal combustion engine. The rest are lost to other factors (friction, gears, etc.), some of which are resolved by electric motors regardless of the source of electricity (ie: regenerative braking, no power loss during idling, simplified transmission, etc.). So looking back at the claims by the MIT scientists that "in theory... efficiency could be as high as 40 percent or 50 percent", it's unclear how much of an efficiency breakthrough this is, depending upon how system-wide a figure the scientists are looking at. It does seem to add a layer of efficiency loss if you're burning fuel to make light to make electricity. And there are certainly other ways to provide juice for an electric motor.
On the other factors, no moving parts is a plus in terms of reliability, but it's too early to tell how this and the other real-world concerns would affect such an early-stage innovation if it were to be commercialized. This uncertainty is typical, and illustrates the challenges investors face when evaluating promising technologies at an early stage. It will be interesting to track the developments on this one.
2. Direct hydrogen-powered engines? It's a topic that's been talked about before, but this article claims that a company called Hydrogen Energy Center is getting ready to offer this as part of a true "flexible fuel" industrial-scale engine. The company's engines will run on several other fuels besides hydrogen, which is good, because as the article notes, there are a lot of obstacles to the use of hydrogen as a transportation fuel regardless of drivetrain technology. Most notably, there are the usual questions of "where's the hydrogen going to come from," and "how are you going to store enough hydrogen onboard, safely?" As the article notes, direct hydrogen combustion perhaps has the best chance of being useful as a fuel and technology for stationary applications where storage is less of an issue.
But on the topic of hydrogen storage comes this other news of a patent that has been filed around the use of tiny palladium-filled glass spheres as a storage medium for hydrogen, providing safety and density.
Of course, another critical issue is cost. Palladium, while less expensive than some other metals, is still not cheap. How much palladium would be required (and what manufacturing process could be used to cost-efficiently embed it in trillions of glass spheres) is unclear. This is all, of course, on top of a recent Popular Mechanics study showing that, out of all of the available options for powering a car across the country, hydrogen would be the most expensive -- more than 10x more expensive than just using electricity. Perhaps the above innovations will help solve this problem, as the study was based on currently-available hydrogen fuel cell technology (GM's Hy-Wire concept car)...
3. So why not just make electric cars, then? As this article mentions, batteries are a big obstacle. Currently-used nickel metal hydride batteries are heavy. As the article mentions, there's a lot of research being put into lithium ion as a potential alternative. But the ability for rapid charging and discharging is an issue, as is lifespan, as is cost, and as is heat (as any laptop user can attest). Which is why some are pinning their hopes on ultracapacitors instead of (or perhaps in addition to) batteries in vehicles with electric drivetrains. There's even talk of being able to use improved lead-acid batteries for hybrids. Given the obvious large-scale applications if anyone can ever solve the transportation-related energy storage issue, it's no wonder so many cleantech investors are making big bets in this market.