Solar Photovoltaic Systems Questions and Answers

Answer: A

Solar energy is converted directly into electricity by a photovoltaic cell.

A photovoltaic (solar) cell is made of a semiconductor, usually silicon, with a p-n junction. Photons of sunlight free electrons in the semiconductor, and the junction's electric field drives them as a current, so electricity is produced with no moving parts or intermediate heat.

Dry cells and rechargeable cells store or produce electricity chemically, not from sunlight. A photothermal device converts sunlight into heat, which would need a further step (a turbine) to make electricity, so the conversion is not direct.

Answer: A

The output of a solar cell depends on the intensity of solar radiation.

A photovoltaic cell produces current in proportion to the number of photons absorbed, so the current, and hence the power, rises almost linearly with the intensity of incident sunlight (irradiance). That is why output falls on cloudy days and is highest when the sun is overhead.

Heat (infrared) actually reduces a cell's efficiency, since higher temperature lowers its voltage. Silicon cells respond mainly to visible and near-infrared light, not chiefly to UV or mid-infrared (MIR), so neither component determines the output.

Answer: C

Photovoltaic cells convert solar energy into electrical energy.

A PV cell is a semiconductor junction, usually silicon. Photons of sunlight free electrons in the material, and the built-in field of the p-n junction drives them through an external circuit as direct current. This is the photovoltaic effect.

Tidal, hydro and wind power are converted mechanically: moving water or air turns a turbine that drives a generator. None of them uses a photovoltaic cell.

Answer: B

The thin-film material is cadmium telluride (printed 'telluroide').

Cadmium telluride (CdTe) has a band gap of about 1.45 eV, close to ideal for absorbing sunlight, and absorbs strongly enough to work in layers only a few micrometres thick. It is the leading thin-film photovoltaic technology.

Cadmium sulphide is used only as a thin window (buffer) layer on top of CdTe, not as the absorber. Cadmium oxide and cadmium sulphate are not used as photovoltaic absorbers.

Answer: D

The International Solar Alliance has its headquarters at Gurugram, India.

The ISA was launched by India and France at COP21 in Paris in November 2015 to promote solar energy among countries lying wholly or partly between the tropics. Its secretariat is on the campus of the National Institute of Solar Energy in Gwalpahari, Gurugram, Haryana. It became the first treaty-based international organisation headquartered in India.

Paris is where the alliance was announced, not where it is based. Tokyo and New York host other bodies, such as the United Nations University and the UN headquarters, but not the ISA.

Answer: A

Both (A) and (R) are true and (R) is the correct explanation of (A). Solar photovoltaic cells are expensive because they are made from high-purity crystalline silicon, whose purification and wafer production are costly, and because they convert only about 10-12 per cent of the sunlight to electricity in the cells cited here. A low efficiency means that a large area is needed per unit of power, which raises the cost per kilowatt. The reason is therefore a direct cause of the assertion, which excludes the code that treats it as unrelated.