[mythtv-users] [Slightly OT] solar power for all our gadgets

[Jon Bishop]

On Mar 11, 2009, at 1:16 AM, Simon Hobson wrote:

> In general (and yes, it's a sweeping generalisation), people in the  
> electricity industry aren't keen on large levels of embedded  
> generation. In small amounts it's "OK", but there are real worries  
> about what large amounts of embedded generation will do to control  
> and stability. 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).

Well, that's true of most current portions of the grid, there's a lot  
of talk going on about smart grids and vehicle to grid systems, that  
do exactly what I am suggesting. There are some important keys though.

> How much embedded generation is tolerable before system stability is  
> at risk is something that's "keenly debated" !
>
> So the distribution companies aren't keen as it complicates their  
> switching and protection. Generators aren't keen as it either takes  
> some of their base load (the most profitable) or makes them vary  
> output more, or both. And the people running the grid and  
> responsible for it being stable don't like it because it's hard to  
> control.

Of course the establishments would like to keep the status quo.  
Profitability is a poor motive that leads to short sighted thinking.  
The difficulty to control will be alleviated by automation.

> And there is the detail every pro<whatever> campaigner seems to  
> ignore - certainly for wind, for every kW of wind capacity, you need  
> a kW of conventional capacity to back it up when the wind stops  
> blowing. The usual counter argument is that the wind will blow  
> somewhere - but historical figures show that a few years ago, the  
> whole of Europe was more or less becalmed for 10 days ! Now, if you  
> are a generator, being asked to provide 'back up' capacity that  
> won't be called on much, and will be required to cycle a lot, then  
> you aren't going to put in the cleanest, most advanced gas turbines  
> (about the only technology with the speed of response required) -  
> you'll put in the cheapest on the basis that it's not going to earn  
> much revenue when it's not generating, and it's not going to last  
> too long when constantly cycled. Result ? Wind results in more  
> emissions !

Not if the wind isn't directly feeding the grid, but instead charging  
large arrays of molten salt batteries. Then there isn't a direct  
effect on the grid - as long as the batteries store more energy than  
the windmills can produce for an alotted time. I think that windmills  
are only useful as a small scale supplement though - too many people  
ARE betting the farm on them, and they're not going to cut it.

> 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. http://www.aep.com/newsroom/newsreleases/?Id=1397

And, there's a wholly unmentioned technology available to us today,  
right now, that could result in all the power generation we need,  
without using any fuel at all. Enhanced Geothermal Systems. Read about  
the study MIT just recently completed here: http://www1.eere.energy.gov/geothermal/pdfs/evaluation_egs_tech_2008.pdf

And I think that I've strayed far enough off topic with this one... so  
lets get back to the important stuff, like how to cram 30TB of hard  
drives and 10 tuners into the same case, and where to find a power  
supply to run them all :-)

~Jon