L B wrote:
>
> Equipping
> > them with solar panels for those laptops would only
> > help with another
> > 4%. As you can see, the key to savings in computers
> > is moving to lower
> > internal operating voltages.
>
> I used to work for the National Renewable Energy Lab.
> The last thing I remember is the Photovoltaics
> department being elated that their solar panel
> research had elicited a new and improved
> 17-point-something percent efficiency. I was
> underwhelmed. These are some of the most quoted
> physicists in the world, and this was the result (I am
> sure a lot of the the baby steps were due to
> DOE/government meddling anyway).
>
> Does anyone have any current numbers on this? I
> haven't talked to anyone there for years. Thanks.
Due to constraints of physical law, the theoretical maximum efficiency
of photovoltaic cells is approximately 36% or so. Current state of the
art cells using dual layers (GaAs and GaAnt) to capture more of the IR
spectrum have achieved around 33.5 to 34% efficiency, however they are
very expensive, too much for the degree of greater efficiency over
silicon cells. The other approach is to make the easiest to fabricate
cells very cheap to make. Thin film amorphous cells are around 10%
efficient but are very cheap to make, costing around 12-25 cents /kWh
(versus over $2.00 for high efficiency cells).
The efficiency of cells is also affected by the amount of flux they are
receiving. For example, the GaAsAnt cells mentioned above are slightly
more efficient in space than on earth, and reach their peak efficiency
in a natural gas furnace, converting the highly concentrated IR energy
of natural gas flames to electricity for a unique hybrid electric car
that Washington State University was developing in the mid-90's. The 34%
efficiency exceeded (and total 24% efficiency) of the test vehicle the
14-18% efficiency typical of IC autos.
This archive was generated by hypermail 2b30 : Fri Oct 12 2001 - 14:39:42 MDT