From: everything-list@googlegroups.com
[mailto:everything-list@googlegroups.com] On Behalf Of John Clark
On Sat, Mar 1, 2014 at 12:10 AM, Chris de Morsella <cdemorse...@yahoo.com>
wrote:
>> Who cares about gravimetric density?
> Evidently you don't; that much is clear. The automobile companies that are
moving towards electric vehicles care - and care a lot.
Why? They care about weight and how much energy it can store, but I don't
see why they'd care how dense it was. Well OK if it had the density of
styrofoam there could be a problem finding a place to put 200 pounds of it
in a small car, but that is not a realistic issue; as long as the battery
was reliable and cheap and stored lots of energy for its weight I don't see
why car makers would much care if it was as dense as aluminum or as dense as
lead.
Gravimetric density is the measure of unit of potential energy per unit of
weight; while volumetric density measures unit of potential energy per unit
of volume. While both are measures of energy density; they are not
inter-changeable and are measuring different things. Both are important. To
give you an example hydrogen gas has a very high gravimetric density, but a
very low volumetric density. Weight essentially determines how much power a
car will need; the more a car weighs the more energy it will require to move
it along. If a battery system has twice the gravimetric density as another
type of battery it can store twice as much energy per kilogram of mass.
Can't you see how important this is for automobile manufacturers - or for
that matter for the makers of all the mobile electronic devices becoming so
ubiquitous nowadays.. The smartphones, tablets, digital cameras, music
players and so on.
Hope this clears up any confusion on your part on the specific meaning of
these two related means of measuring energy density.
> The advanced battery field is moving very fast
>>I disagree. Nearly all electronic components are astronomically better
than they were 50 years ago, but batteries are the exception, they are only
slightly better.
That was the case up until recently, but the need for better batteries is
huge. Just the market for powering portable devices itself is huge and
growing. Whereas before battery R&D spending languished and was stuck in the
slow lane, for the last ten to fifteen years R&D spending has really ramped
up on it and the results of all of this effort is moving through the R&D
pipeline towards market.
But I agree it has moved frustratingly slow compared to the pace in say chip
transistor density.
Energy density is critical for transportation and portable applications; it
is much less of a factor for fixed large scale energy storage facilities.
What matters for these is of course COST, scale, durability (how many cycles
before degradation becomes a factor) and metrics of this nature.
Costs keep coming down -- EOS Energy Storage, for example, intends to launch
its zinc-air battery next year with a price of $200-$250/kWh, which includes
the cost of the inverters to go between DC and AC power. This is starting to
close in on the cost for gas turbines, which are the current default means
of providing spinning reserve for the grid.
> It may surprise you but I wish the US would start up an LFTR program. in
fact, I wish the 8+ billion dollar loan guarantee now earmarked to fund
those nuclear white elephants in Georgia was instead - much more wisely IMO
- being used to kick start an LFTR program.
Well, we agree on something. And I would rather they had spent 8 billion
dollars on research to improve photovoltaic cells and batteries rather than
build more reactors based on designs from the 1960s; even the most promising
ideas can go south and this matter is too important to place all our bets on
just one vision.
We do agree on this.
Chris
John K Clark
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