Heat from the sun -- along with fancy catalysts and fine-tuned collectors for capturing heat from the sun -- could one day let you produce hydrogen at home.

Duke University professor Nico Holz has created a prototypesolarthermal system that effectively splits water into hydrogen and oxygen. Holz claims that the system is 28.5 percent efficient in summer and 18.5 percent efficient in the winter, which he claims bests similar systems powered by ordinary solar thermal collectors or PV panels.

He estimates that the system would cost $7,900 or so to install.

Hydrogen remains one of the most controversial topics in green energy. Right now, it's expensive to produce and most industrial hydrogen producers emit incredible amounts of carbon dioxide. That's because they harvest it by cracking methane molecules. It is also difficult to transport. Hydrogen fuel cells are, additionally, incredibly expensive and don't last long.

In other words, there are lot of negatives. On the plus side of the ledger is promise. If hydrogen can be produced cheaply from water, the relatively light gas could become a lightweight, ubiquitous medium for storing electrons. Homes and cars would contain canisters of hydrogen. When electricity was needed to run the TV or recharge the batteries in your EV, hydrogen gas could be run through a fuel cell membrane to harvest electrons.

The roadblocks to hydrogen nirvana include finding 1) a cheap source of energy for splitting water 2) catalysts that will reduce the amount of energy required to pull the oxygen atom from the two hydrogens in a water molecule and 3) a system that will let the process flow continuously.

Several companies (such as Signa Chemistry) and research departments at major universities like Purdue have been toiling away at coming up with a dream catalyst. Sodium is one of several candidates being considered.

Others, like MIT spin-off Sun Catalytix, have been trying to devise a low-energy production system along with catalysts.

While Sun Catalytix and Duke's Holz both want to harness the power of the sun, they appear to be taking different paths. Sun Catalytix employs a solar panel, which harvests electrons from sunlight, as a source of power. Holz uses heat. PV or thermal? It's one of the big divides in the solar industry. Some companies like ZenithSolar combine both thermal and PV. Conceivably, one could combine PV and thermal technologies in a hydrogen system, too.

The system consists of a series of copper tubes brushed with thin layers of aluminum and aluminum oxide. A mixture of methanol and water flows inside the tubes and gets heated up by the sun. In the end, this allows the temperatures inside the tubes to rise to 200 degrees Celsius, far higher than the 70 degrees Celsius achieved in conventional solar tubes. Catalysts are added and, voila, hydrogen.