PV Gap

Mario Said:

Te active area of a 0.5V photovoltaic cell is 120mm by 145mm?

We Answered:

The missing part of the question is the current. Since its the sun you'll have to make some assumptions. Take a look at the site given below. Scroll down to the bottom. Its a problem very similar to yours.

Once you have your current its simply a difference is power.
P = V*I
you have the area (0.012m x 0.0145m) and include the efficiency factor and you are set.

Alma Said:

If a Strirling Engine was used to cool a concentrated Photovoltaic cell, how efficient would the system be?

We Answered:

Compared to other thermodynamic cycle processes , Stirling process has the advantage, that it could extract the maximum possible amount of work of a heat stream. That means it could operate with Carnot efficiency, whci is given by:
? = 1 - T_cold/T_hot

For the given temperature gap it is
?_se = 1 - 358K / 1873K = 1515/1873 = 80.9%

The efficiency of the photvoltaic cell operates is the fraction
of the incoming heat converted to wort
?_pc = W_pc/Q_in
<=>
W_pc = ?_pc ·Q_in

The rest of heat, which is not converted to work, is rejected by the cell. It is:
Q_r = Q_in - W = (1 - ?_pc) · Q_in

These heat is transferred to the Stirling engine. Hence:
W_se = ?_se · Q_r = ?_se · (1 - ?_pc) · Q_in

The total effiency of the cell-engine system is
?_total = (W_pc + W_se) / Q_in
= ?_se + ?_se · (1 - ?_pc)
= 70/230 + (1515/1873) · (160/230)
= 86.7%

This represents the theoretical maximum efficiency, which can be achieved by combination of photovoltaic cell and striling engine.
The efficiency of a real Stilring engines is lower than Carnot efficiency. The wikipedia article states that they only reach one half of Carnot efficiency. I doubt this and think it is more, but I'm not an expert on heat engine design.