Re: Art, where's the buzz on nanotech saving America today?



On Wed, 29 Mar 2006, BMJ wrote:

Straydog wrote:


On Mon, 27 Mar 2006, rrc wrote:

BMJ wrote:


Afterwards, that is if there's a world in the 23rd century, we'll have
innovate in the solar realm that is if they're not suffering from
another "S&E shortage" during that time.


One of the present drawbacks with photovoltaics is the relatively low
conversion efficiency of modules. This means that a PV installation
will require significant areas of land. In addition, renewable systems
require a large initial capital expenditure when compared with existing
systems. (I investigated the economic optimization of hybrid renewable
systems for my Ph. D.)


That's why I'd placed the 23rd century as a caveat. Present day
photovoltaics are pretty dead end.


You guys are not reading the newspapers. I don't have it handy, but there were about two WSJ articles where out in california quite a few new homes have solar panels built in (they get a tax break, I think) as a supplement
in case they have brownouts or rolling blackouts and everyone is happy with the direction this is going in. Its got a long way to go but the technology is already here and been here for 1-2 decades.

I know what you're referring to as, if I remember correctly, it has the backing of the governor. What I meant was about how systems are designed and what the present technology is like.

PV modules can convert only a small fraction of the available insolation into electricity. One of the main limitations is the semiconductor materials that are used. Until something more efficient becomes available, there's little that can be done about it.

Everyone knows this. The point is that solar power is now, in low unit quantities, a $7 per watt source of renewable energy. Last night I looked up the electric generation capacity in the USA and made a very very very rough calculation that if the DoD budget were diverted to solar power generation, we could be totally off non-renewable, non-radioactive, no waste products energy sources in about 100 years. That is all with
_existing_ technology, the _existing_ conversion efficiency, and no unknowns o
r breakthroughs needed. If we had started some 30 years ago, we would be
about 1/3 the way and research of all kinds might have improved cost/unit
figures and maybe even lifetime and efficiency.

PV module capacities are, at the most, on the order of a few hundred peak watts. That means that if one were to use them to, say, power a house, they would need a large area of land to properly site and space them.

I made rough calculations and found that about 1/2 of the area that is needed is already on 1-story house roofs. The rest could be obtained by using a "fence" behind the house. I thought about this for our retirement house but at my age would not recoup the investment before I died. It would take commitment at an early age.

Building
them into houses restricts their usefulness as their orientations would be fixed. In order to better utilize the available insolation over the year, the elevation angle should change to follow the angle of the sun with respect to the horizon. In some cases, modules can be set up to follow the sun during the day using solar trackers, but that can make the installation more expensive.

My brother got into the panels about 10+ years ago. Gets about 1/3 of all of his electricity needs. And, he used only a fraction of his house roof.

A lot of systems are over-sized, so that means that a lot of the power they produce could be wasted after meeting the required load demand.

Or fed back into the grid and make money for the owner.

Some of it
can be stored, but that's limited by battery size as well as the charging current. (Avoiding gassing is important, particularly if one uses, say, lead-acid batteries.) Unless one has either an auxiliary load, which operates if the power is available, or it can be put into a utility grid (obtaining permission to do that can prove to be a regulatory headache),

At least in some areas the laws are already on the books to just read the meter even if it runs backwards and pay the owner.

whatever's left is often dissipated.

Better put on the thinking cap and do something with it. At least I would.


.

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