I’ve been reading about the future of the fuel cell car and this got me thinking about the whole topic of energy for mobile devices, including large ones like cars.

I started by ignoring the energy cost associated with manufacturing the different devices. This is clearly insane if your trying to properly assess the environmental merits of a particular technology. The whole life cycle cost must be included for a full environmental impact analysis, but since I’m mainly interested in the local effects of energy consumption I feel justified in letting myself off this time.

How’s the energy stored?

Not too may options here at the current time, if you want a reliable source of energy.

  1. Electrically using a battery or similar device.
  2. Chemically in some sort of fuel, probably liquid or gaseous.

Now right here we have the first problem: The electrical energy stored in the battery had to be generated somehow, with the original source probably a chemical fuel as well. Wind, solar and tidal power are also possible sources.

But what about turning it into electricity?

Each of these technologies has it’s own particular impact on the environment; the old adage of there being no free lunches certainly holds true here! Power stations, whether traditional and alternative, will fall a long way short of 100% conversion efficiency. However, generation on a large scale is often more efficient than that on the scale required by individual devices. This is the basis of the idea of centralisation which gave the UK, and other countries, a national power grid.

The grid is a big problem.

Unfortunately, most of the efficiency gained by centralised generation is promptly lost during the transmission of this electricity to where it is needed. Some estimates put the UK grid losses at 10% of total power generated and the more remote the power station, the bigger the problem; bad news for the off-shore wind-farm!

We could convert the energy into liquid or gaseous chemicals for transportation, negating the grid losses, but this action is also very inefficient. This is essentially where the hydrogen or methanol for fuel cells would have to be produced, converting fossil or nuclear fuels into another type of chemical fuel source.

So it’s just a question of where we burn the fuel.

Do we burn it remotely and move the energy, in either electrical or chemical form, or just move the original fuel and burn it locally?

If your generating power from nuclear fuels it’s a bit of a no brainer. Currently the only safe way to use this fuel is remotely, but the energy released could be used to bring the hydrogen economy to life. Manufacturing hydrogen from water requires a great deal of energy and few other sources would make this economically or environmentally viable. The alternative of creating hydrogen from fossil fuels lacks credibility: Why waste energy doing it?

The answer is to provide a fuel that when burnt releases less harmful pollution locally, but without fully addressing environmental issues on a global scale. This brings me to the numb of the problem regarding the conversion of any hydrocarbon fuel. Most of the alternative systems today are simply less efficient than the best available combustion plant. So if your deriving your energy from fossil sources in the first place, and most of what we use is, this is probably still the way to go.

But it’s a matter of scale and use. Not everyone wants a two-stroke engine attached to their laptop or mobile phone, and in this case batteries have the edge on small fuel cells for me; the main problem being the fuel storage.

Batteries also start to win out is when coupled with local alternative generation technologies. This could be solar panels on your roof or pocket calculator; or a small wind turbine in the garden. This type of distributed power generation has promise, especially in locations without a grid supply and suitable environmental conditions. Batteries also provide the technology behind hybrid vehicles that can charge from electricity generated locally by combustion of fuel. This combines the advantages of both approaches. But, these types of application are where the environmental impact of manufacture raises it’s ugly head. A topic for another day.