Thursday, October 4, 2007

Battery Discussion Follow-up: A Battery Revolution?

Thanks to everyone who attended/participated in the recent Battery Discussion ('A Battery Revolution?', Oct 3, '07). There was a ton of participation for a diverse number of people with great backgrounds/perspectives.

I've been requested to follow up the discussion with this blog to encourage continued discussion on this topic. I'll first summarize some of what we talked about, then try to stimulate more discussion.

I've uploaded a slideshow and the handout I put together for the discussion:


-Batteries are appealing because they have a low enough cost, long lifespan, are very reliable, and have enough power-to-energy suitable for most portable applications. Batteries were really enabled by portable applications - otherwise, electronic devices can simply run off of grid power, or generator power.

-Fuel cells have higher energy/power density that batteries, but their round-trip efficiency is ~35%, compared to >90% for Li-ion batteries, and they are more expensive.

-Neither batteries nor fuel cells, in of themselves, are 'renewable energy sources', but rather, they could play a role in the energy infrastructure, enabling renewable energy sources (like wind, solar, hydro, nuclear (?)) to charge the batteries/create hydrogen, which in turn, could power our cars. This could break the CO2 cycle and reduce dependence on foreign oil.

-Flywheels and capacitors can supply a lot of power, but do not have good energy density (or cost per unit energy, $/kWh).

-There is a company in Texas (EESTOR) making some pretty revolutionary claims about new ultracapacitors with higher 'energy' density that lithium-ion batteries (not to mention, longer lifespan, lower cost, and high power density). I would be very excited if this becomes a reality, but I am skeptical until I see a working model.

-There was much discussion about the use of batteries in hybrid electric vehicles (HEV's) /plug-in (PHEV's). Batteries are certainly pushing towards these markets, but they have more challenges to overcome, including safety, cost, and energy density.

-Lastly, the talk shifted towards other applications, such as renewable energy (i.e. wind power) support. Such a storage device must cost ~$100/kWh, have moderate efficiency (>70%), and very long lifespan (>3000 deep cycles). It's a very tough market to enter, but if a battery can do it, it's a 'game changer'. Some utilities in the US are already installing sodium-sulfur (NAS) or flow batteries (Premium Power) for this (and other) grid power applications. The cost of the NAS battery alone is ~$170/kWh, vs. $100/kWh for lead-acid batteries (which don't have the cycle-life required for these applications), vs. $1000/kWh for Li-ion batteries.


There were a couple of areas that we touched upon but didn't have any good answers to. I'd like to finish this post by posing the following questions:

1) What makes up the cost of a battery? I've heard that ~30% is materials related - but what are the other cost components? (i.e. manufacturing, transportation, labor, disposal of toxic chemicals?)

2) Is there a "Moore's Law" equivalent for batteries? How has the cost/energy density/power density improved over time?