A concentrating solar thermal system collects 5 GJ/h of thermal heat, which is delivered to a 94% efficient hot water generator. The hot water generator is used to raise the water temperature from 15°C to 65°C. The specific heat of water (Cp) is 4.2 kJ/kg-°C. What flow rate (liter/second) of hot water can be delivered from the hot water generator?

• A.4.2 liter/second
• B.6.2 liter/second
• C.9.2 liter/second
• D.12.0 liter/second

Correct Answer: C

Step 1: Compute Useful Thermal Energy Output
Given:
* Solar system delivers 5 GJ/h
* Hot water generator efficiency = 94%

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A 3 MW rated wind-powered turbine has a rotor diameter of 113 meters. What is the efficiency of the wind turbine at rated power if it is operating in wind power calculated at 8.6 MW? Assume an air density of 1.225 kg/m³.

• A.42.7%
• B.28.4%
• C.34.9%
• D.59.3%

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Infiltration (inward air leakage) in a building is dependent on several factors. Which of the following is least likely to affect or influence infiltration in a building?

• A.Outside air temperature
• B.Building height
• C.Outside air wind speed
• D.Poor or missing weatherstripping
• E.Fuel type used for heating and cooling

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What term describes the difference between the control signal value and the set point?

• A.Dead time
• B.Error or offset
• C.Cut off
• D.Dead band
• E.Differential

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What is the main cause of low power factor?

• A.Harmonics
• B.Fluorescent lighting
• C.Solar flares
• D.Computers and electronic equipment
• E.Low-load induction motors

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