alt.energy.renewable

jan siepelstad wrote:
> I would see it this way:
>
> Take a conventional steam turbine system.
> The efficiency of the cycle is somewhere between 40 en 45% with high steam
> temperatures (around 560°C).
> This steamtemperature is not achieved in most solar concentrator systems
> (beware: I talk about the steamtemp. not the max. temp. that could be
> achieved in the focal point).
> So let's assume something like 32% for the complete solar system. (Including
> mirror efficiencies of between 95-98%)

Glad to see we reached the same efficiency !

> When the area of land that is needed for 1 m2 of effective solar receiving
> (=mirror) area would be 4 m2, then you are already there: 25% of 32% = 8% !

I missed that loss : the required horizontal ground surface equates
4 times the concentrator surface. Yet it's obvious ;). Thanks.

Note that PV cell efficiency is computed for a perpendicular
-normal- illumination. 'In situ' efficiency of a PV cell is
considerably smaller too. So that 8% is not that bad.

> However it's still a lot better than biomass production from the sunlight
> (assume 1% efficiency) and use this in a conventional powerplant with 40%
> efficiency, so that % is left as electricity.....


> "Mauried" wrote in message
> news: @news. ...
>> Just been researching some efficiencies of existing Solar Thermal
>> Power Plants including both Solar Trough collectors and also Central
>> Towers using focussed Mirrors and the efficiencies seem to be
>> extremely low , around 8% .
>> Anyone know why .

Maybe you missed that too ? :)

>> I would have thought that this type of plant would have high
>> efficiency given they simply use mirrors to concentrate sunlight.
>> Where is all the energy lost.

Erdy