[mythtv-users] [Slightly OT] solar power for all our gadgets
linux at thehobsons.co.uk
Wed Mar 11 19:19:00 UTC 2009
Jon Bishop wrote:
>>Not saying wind is bad, but you have to think of the WHOLE picture.
>>Of course, solar is even worse, you know that EVERY day, all solar
>>in the US will stop generating. Just like ALL solar in Europe will
>>stop generating a few hours earlier.
>>So you either have to have storage (and apart from hydro we don't
>>have a reasonably cheap, large capacity storage technology), or we
>>cycle other plant to take the load. Since we've already used just
>>about all the <politically> possible pumped-hydro storage sites,
>>that means we have to cycle conventional plant more if we have
>>large amounts of solar.
>Storage is the solution. As a mentioned above, the molten salt
>batteries would be suitable for this application. They have high
>energy density, and last many decades with little or no reduction in
>storage capacity. As a bonus, power companies *are* starting to use
>them. I'll link again to this article I posted earlier.
Excuse me if I don't sound impressed. 1000MW target sounds
impressive, but when you work out what proportion of the total supply
capacity just 1GW actually is, it suddenly doesn't sound all that big.
I don't know if it's just wooly techno-babble from a technically
illiterate PR company, but expressing battery capacity in MW is
totally meaningless. At work I have a battery pack on the UPS that
would probably give a MW if you pushed it (like, dropped a
screwdriver across the terminals !) - but not for many seconds !
After all, there is a world of difference between something that can
provide 1GW for a few minutes for peak lopping only vs something that
can provide 1GW for hours or even days to cover for becalmed
There are however a number of 'chemical cell' technologies already in
use. The beauty of them is that you can increase storage capacity by
increasing the size of storage tanks for the reagents involved -
without the cost of increasing the energy conversion unit. With
batteries, you combine storage and conversion in one place, so to a
large extent, to increase storage capacity, you also increase the
size of the processing with the cost that goes with it.
I recall reading an article in one of the journals (IEE), and one
case study described was a lead processing plant. For obvious
reasons, having an uncontrolled shutdown with the risk of releasing
lead dust was considered unacceptable - so they had a chemical cell
based UPS to run the entire factory (about 1MW capacity I believe).
After a while, they did the sums and started using it to peak lop
their demand and so made considerable savings on power costs.
At 09:59 -0700 11/3/09, David Brodbeck wrote:
>On Wed, March 11, 2009 1:16 am, Simon Hobson wrote:
>> As it is, I believe in the US the main distribution
>> system is split (with DC links) to avoid the problem of trying to
>> control and keep stable an AC system the size of the North American
>> continent (or at least, last time I looked it was like that).
>There are actually three main North American grids, which are not
>interconnected with each other. Eastern, Western, and Texas. (Yes, Texas
>has its own independent power grid. Maybe in case they decide to secede.)
> Alaska and Hawaii also have their own grids, for obvious reasons.
>There are some DC lines, but not to split up the system; the grids don't
>connect with each other, and within each grid things are kept
>phase-locked. DC lines are used for long-distance connections because
>they have lower losses, and with a long enough run this makes up for the
>conversion losses at each end. The most famous example of this is the
>Pacific DC Intertie, which moves hydroelectric power from the Pacific
>Northwest down to L.A.
I stand corrected, another interesting tidbit to file away.
There is actually a different way of looking at things. A few months
ago I went to a talk given by a couple of chaps from Lotus
Engineering. After explaining why both electric and hydrogen powered
cars will never be practical, they then outlined how methanol is
practical now, and can be used in pretty well any vehicle*. And it
can be made in a carbon neutral or even carbon negative way.
* They reckon that just about all current petrol engined cars could
be made flex fuel with some basic software changes and potentially
different seal materials. The incremental cost of building this into
new cars would be minimal.
Basic process is that you can capture CO2 from the atmosphere with
potassium hydroxide. You can then add hydrogen and the potassium
hydroxide is reformed and methanol is created. Hydrogen can be
created by electrolysis. The power for that can be from PV solar
panels, wind (or in the meantime, nuclear).
The beauty of it is that the raw material (CO2) can be stored in
large quantities in the atmosphere and will be there when you are
ready to use it. The resulting fuel (methanol) is easily stored in
tanks without pressurisation. So you can simply run the process when
the power is available. If using nuclear power, you could integrate
the process control with grid control - and basically turn the
process up and down to create a level base load (ie when there is a
peak in demand, you turn down the demand from the methanol plant). If
using solar power, it simply runs when the sun is shining.
Of course, having made methanol, it's easily transported, compatible
with petrol (gasoline) and ethanol, and if you want to can be used as
a feedstock to make some plastics - and if you do that, the carbon
gets locked up and it's carbon negative.
I have to admit, it sounds rather good and I find myself asking -
where's the catch ? Apart that is, from the cost of covering an area
the size of Montanna with PV solar panels, stated to be enough to
supply the entire US road fuel demand !
And then the next question I find myself wondering is ... and what's
the minimum system setup cost to power my own motor ?
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
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