Photovoltaic (PV) System Design Flashcards

What does one 'peak sun hour' represent?

Answer: 1 kWh/m² of solar insolation, equal to 1,000 W/m² for one hour

Peak sun hours restate daily insolation as the number of hours at 1,000 W/m² that would deliver the same energy.

For maximum annual energy from a fixed south-facing array, the tilt angle is usually set close to what?

Answer: The site's latitude

A tilt near the site latitude roughly maximizes annual insolation on the plane of the array.

A 10 kW DC array gets 5 peak sun hours per day and has a performance ratio of 0.80. About how much energy will it produce per year?

Answer: 14,600 kWh

10 kW × 5 h × 0.80 × 365 days = 14,600 kWh per year.

What are the Standard Test Conditions (STC) for rating PV modules?

Answer: 1,000 W/m², 25°C cell temperature, AM1.5 spectrum

STC is 1,000 W/m² irradiance, 25°C cell temperature and the AM1.5 spectrum.

What is a typical power temperature coefficient for crystalline silicon modules?

Answer: -0.40%/°C

Crystalline silicon modules usually lose about 0.3–0.45% of their power for each °C rise in cell temperature.

In a PV system, what does the performance ratio (PR) measure?

Answer: Actual energy yield divided by theoretical yield from plane-of-array irradiance

PR compares actual output with ideal output and captures all system losses, independent of how much sun the site gets.

When orienting an array to true south with a magnetic compass at a site with 10° east magnetic declination, what compass bearing should be used?

Answer: 170°

With east declination, true bearing = magnetic + declination, so true south (180°) corresponds to a magnetic bearing of 170°.