Describe the difference between photovoltaic cells and solar heating panels.

A solar farm is made up of photovoltaic cells of area 25 000 m². The average solar intensity falling on the farm is 240 W m^–2 and the average power output of the farm is 1.6 MW. Calculate the efficiency of the photovoltaic cells.

Determine the minimum number of turbines needed to generate the same power as the solar farm.

Explain two reasons why the number of turbines required is likely to be greater than your answer to (c)(i).

solar heating panel converts solar/radiation/photon/light energy into thermal energy AND photovoltaic cell converts solar/radiation/photon/light energy into electrical energy

Accept internal energy of water.

power received = 240 × 25000 = «6.0 MW»

efficiency «\( = \frac{{1.6}}{{6.0}}\) = 0.27 / 27%

area = \(\pi \) × 17² «= 908m²»

power = \(\frac{1}{2} \times 908 \times 1.3 \times {7.5^3}\) «= 0.249 MW»

number of turbines «\( = \frac{{1.6}}{{0.249}} = 6.4\)» = 7

Only allow integer value for MP3.

Award [2 max] for 25 turbines (ECF from incorrect power)

Award [2 max] for 26 turbines (ECF from incorrect radius)

«efficiency is less than 100% as»

not all KE of air can be converted to KE of blades

OR

air needs to retain KE to escape

thermal energy is lost due to friction in turbine/dynamo/generator

Allow velocity of air after turbine is not zero.