MIT scientist Daniel Nocera has released new publicity around his solar leaf concept. The basic idea is that instead of converting sunlight to electricity and storing it in a battery, use the electricity to split hydrogen from water allowing the hydrogen to be used in a hydrogen fuel cell. An inherently lossy process which will require a system to keep hydrogen and oxygen separated until it can be directed into the fuel cell for conversion back to electricity. Theoretically it could provide an almost permanent supply of electricity and stored energy if combined with a rain water capture system. However due to the lossiness of the conversion process it does seem to be running at a significant disadvantage to normal electricity storage in the form of a Lithium Ion battery. However as it is using a fuel cell that probably requires at least some rare earth elements during the manufacturing process which will of course contribute greatly to the amount of energy consumed to completely make the system.
In the meantime a Japanese company has already taken the process to it’s inevitable conclusion and produced a full scale home sized hydrogen conversion system. They claim that with a solar panel, 1500 cc of water and their hydrogen conversion and storage system they can provide 5000 KwH of electricity which is around that amount that an average home would use during a night. 5000 KwH is approx enough stored energy to provide 16 hours of electricity to an average home PC with a 300 watt power supply. However if you add a refrigerator or washing machine into the mix you start to see some significant decreases in energy supply time. The main benefit of this system is that it can be run simply on water and solar. Once the investment is made it will provide around 50 years of constant supply of energy as long as you don’t need to use more than 5000 KwH of energy between charges. If connected to a rain water capture system it is theoretically a 50 year life cycle version of a perpetual mobile. It will no doubt be very useful as a replacement for fossil fuels in low energy consuming households. Combined with a larger solar hot water and electricity storage system and you would be able to live with a degree of energy security.
If Nocera has a better and cheaper more energy efficient system up his sleeve he is keeping the details to himself at the moment. No doubt he is still waiting for approval from MIT to do something actually useful for a change. The general rule of thumb with anything from MIT is that it never actually gets anywhere other than securing more funding for the scientists involved in the projects.