Following up on the depolymerization initiative of the DOD, there is a similar initiative being undertaken by the DOE. Hydrogen age, here we come.
In the next quarter to half century, further advances may lead to large-scale production of hydrogen gas for fuel cells and the ability to store in the ground both bio- and fossil-derived CO2. Microbes could enable the inexpensive production of hydrogen by consuming a hydrogenated feedstock and releasing H2, for example, splitting water with light or splitting hydrogen from biomass or even coal.
2007-03-14: Hydrogen car dashboard

Driving around Monterey in the BMW Hydrogen 7.
The liquid hydrogen tank is in the trunk (at -418°F), and a H2 button on the steering wheel switches the V12 engine between hydrogen and gasoline.
2007-06-22: Superconducting Turbojet
A superconducting motor would be very lightweight and far more efficient electrically, generating 3x the torque of a conventional electric motor for the same energy input and weight. In addition, an electric aircraft would be far quieter than a conventional jet as there are no internal combustion processes involved. Liquid hydrogen is cold enough to make the superconducting magnets work but also has 4x as much energy weight for weight than aviation fuel.
2008-01-11: Thermoelectric Energy Conversion. Using hydrogen as a heat exchanger, solid state, 60% efficient energy generation. Can be used with solar, internal combustion, turbines and other sources of waste heat.
The JTEC is an all solid-state engine that operates on the Ericsson cycle. Equivalent to Carnot, the Ericsson cycle offers the maximum theoretical efficiency available from an engine operating between 2 temperatures. The JTEC system utilizes the electro-chemical potential of hydrogen pressure applied across a proton conductive membrane (PCM). The membrane and a pair of electrodes form a Membrane Electrode Assembly (MEA) similar to those used in fuel cells. On the high-pressure side of the MEA, hydrogen gas is oxidized resulting in the creation of protons and electrons. The pressure differential forces protons through the membrane causing the electrodes to conduct electrons through an external load. On the low-pressure side, the protons are reduced with the electrons to reform hydrogen gas. This process can also operate in reverse. If current is passed through the MEA a low-pressure gas can be “pumped” to a higher pressure.
The JTEC could utilize heat from fuel combustion, solar, low grade industrial waste heat or waste heat from other power generation systems including fuel cells, internal combustion engines and combustion turbines. As a heat pump, the JTEC system could be used as a drop in replacement for existing HVAC equipment in residential, commercial, or industrial settings.
2008-02-08: Mach 5 Civil Transport
To compliment the Scimitar engine, Reaction Engines has proposed a suitable vehicle configuration (A2) that attains the necessary subsonic and supersonic lift/drag ratio for efficient commercial operation. The airframe is designed to have adequate control authority about all axes to handle engine-out and to achieve pitch trim over the full Mach range. In addition the airframe configuration is an efficient structural shape with circular cross section hydrogen tankage and uninterrupted carry-through wing spars. The vehicle is sized to carry 300 passengers since this is typical of future supersonic transport designs and thought to be the minimum to achieve a competitive seat/km cost.

They also have an unpiloted, reusable spaceplane intended to provide inexpensive and reliable access to space.
skylon space plane will be ~$550 / kg to orbit initially and $145 later, significantly cheaper than spacex, which is around $1500 / kg. the space shuttle was $22k / kg. this is achieved with a lower mass ratio, because skylon is air breathing up to 25k altitude. this is a very interesting design and i hope they succeed.
2010-07-13: Hydrogen Drone
Boeing has unveiled the hydrogen-powered Phantom Eye unmanned airborne system for collecting data and communications, a demonstrator that will stay aloft at 20 km for up to 4 days.
Between this and the british unmanned fighter plane, an inflection point.

2014-03-14: Making hydrogen storage practical will make tesla batteries look like amateur hour, and have huge implications.
DOE had hoped that by 2017, a research team could pack in 7.5% hydrogen by weight by 2020. Li’s team has already crossed that threshold, with a hydrogen storage density of 9.5%. The team has also demonstrated the potential to reach an even higher density
2020-06-09: The push to make America tun on hydrogen. This seems at least partially a boondoggle like ethanol.
Nikola’s truck cab—a 1000-horsepower system comprising carbon fiber tanks, hydrogen fuel and a fuel-cell stack—will push an 18-wheeler up to 1200km and weighs 9000kg. The same juice would demand a lithium-ion battery that would add at least 2000kg to a truck with the same range.
2020-12-10: Negative emission car. This is extremely silly, but then again I remember how much people enjoyed the display in a Prius that tells you how much energy you’re getting back from braking. Anything can be turned into a game.
The car is equipped with Toyota’s “Minus Emissions” technology, whereby air is taken into the vehicle, purified, sent into the fuel stack in order to generate electricity, then vented back out of the vehicle. By the time it comes out of the exhaust, the air has been scrubbed of any harmful chemicals and particulate matter 2.5 microns or greater in size. Are people around you likely to notice that you’ve left fresher air? Perhaps not, but you will: “The large 31cm center display includes an Air Purification display that shows the amount of air purified when driving through an easy-to-understand graphic of runners and digital display. It also includes an Air Purification meter that shows how much air is purified during acceleration. The meter enables the driver to feel the contribution that the new Mirai is making to the environment.”