As I was reading yet another article about Shai Agassi’s Electric Car project (a Google search turned up several references, such as The Electric Car Acid Test and Israel Is Set to Promote the Use of Electric Cars), I asked myself what if we could design a “liquid battery”.
Such a “liquid battery” would really be a fuel cell. We pump in two liquids (in the following – liquid/chemical A and liquid/chemical B). As the car is being driven, it gets the electrical energy from combining liquid A with liquid B, creating a third liquid (in the following – liquid/chemical AB). Liquid AB would later be withdrawn. In a processing plant, liquid AB would be electrolyzed and separated back into liquid A and liquid B, effectively charging the system with energy.
Such a system already exists, but using hydrogen. Hydrogen is combined with oxygen to yield water. Water is then electrolyzed to recover the hydrogen for another round.
The challenge is to find chemicals (which can be liquid, gas or solid powder) A, B and AB with the following properties:
- They store energy when separated rather than combined, so that no single chemical will be able to release energy uncontrollably i.e. explode. So, for example, ATP (used as energy storage medium by biological processes) would be out.
- No one of them can release energy by combining with oxygen or nitrogen. This would eliminate the big safety risk of hydrogen.
- Chemicals A and B can be combined in a fuel cell to efficiently release energy in the form of electricity.
- Chemical AB can be efficiently separated into chemicals A and B in a power plant.
- High energy storage density, relative to current technologies.