Sounds a bit silly when put like that, but the part that I missed out is that there is a time delay between splitting the water and using it to generate electricity.

Storage
Solar panels on the roof of the house generate electricity while the sun shines on them during the day, but at night they’re not generating anything. Additionally, during the day many houses are using less power since their occupants are out at work. The MIT plan is to use the excess energy from the panels during the day to split water into its two constituent gases, and store those in tanks in the house.

At night, when the panels are not generating any power, the hydrogen and oxygen are fed from the storage tanks into a fuel cell, generating electricity for the house’s night time needs (and water which can be split again the next day).

This video from MIT explains it in more detail:

Click To Play

Why Not Use Batteries?
Good question. Solar installations for off-grid projects will often make use of batteries to solve this problem of time shifting the power. The reason the hydrogen fuel cell idea is interesting comes down to energy density. A lithium-ion battery has a density of around 2.5 MJ/kg; a lead-acid battery is around 0.1 MJ/kg. Hydrogen has a density of 143 MJ/kg. So, storing the energy in the form of hydrogen makes sense as long as you can generate the hydrogen efficiently; and that has been the problem until now. The real breakthrough the MIT team claims to have made is in being able to efficiently split water into hydrogen and oxygen, and to do so using materials that are plentiful.

[Via Earth2Tech]

In PolyFuel’s prototype, the power supply features a detachable fuel cartridge – about the size of a deck of cards – that can be swapped out while the computer continues to run. Long-distance travelers, or others needing continuous, unconnected, easily portable power for their notebooks, would simply carry spare cartridges in their pocket or purse – a someday common practice that has already been approved for commercial aircraft by the various regulatory bodies around the world.

What are the Advantages?

From an environmental perspective, a methanol fuel cell is a much better technology than the lithium ion batteries we use today. Methanol is a renewable fuel, and the cells can be made from biodegradable or easily recycled materials. While the batteries in today’s laptops can be recycled, it is a much more costly process.

But, as with many things green, the methanol fuel cell has other advantages over the batteries it replaces: with current technology, they last three times longer than a lithium ion battery; in the future that may increase to as much as 10 times. They are also much lighter than batteries, so the traveling worker now has a power source that will last for a long haul flight, and make the hand luggage lighter (that alone is a big deal if you travel regularly with a laptop!). Since they’re also refillable rather than rechargeable, should it run out mid flight you just need to swap the methanol cartridge to keep working.

Disadvantages?

Well, like any new technology there are likely to be some issues for the early adopters. Getting through security checks at the airport with a new feature like this might take some patience (ask the folks with the solid state drive version of the Mac Air).

Being away from home and running out of methanol might be a problem too. Plugging in for a recharge is usually possible today where ever you are likely to find yourself with a laptop, but buying replacement methanol cartridges might be harder, especially when you get in at midnight after a delayed flight.

As this technology becomes more common though, these problems will go away and we’ll all be enjoying laptops that last for days on a lightweight power source.

[Via GreenUpgrader]