EMP Renewable Energy Systems 3

Question 1

How does a pumped hydro energy storage (PHES) facility store electrical energy?

Accepted Answer

Uses surplus electricity to pump water to an upper reservoir for later release through turbines

Answer

PHES stores energy as gravitational potential energy by pumping water uphill during low-demand periods and recovers it by releasing water through turbines when demand is high.

Question 2

What effect does increasing a PV module's cell temperature have on its power output?

Accepted Answer

Power output decreases because open-circuit voltage drops

Answer

Rising cell temperature reduces open-circuit voltage (Voc) at roughly -0.3% to -0.5%/°C, which decreases overall module power output despite a slight increase in short-circuit current.

Question 3

An offshore wind project has a hub height of 120 m and measures wind speed of 9 m/s at that height. Using the wind power equation P = ½ρAv³, if wind speed increases to 10 m/s, how does power output change approximately?

Accepted Answer

Increases by about 37%

Answer

Power scales with the cube of wind speed: (10/9)³ ≈ 1.372, so power increases approximately 37% for an 11% increase in wind speed.

Question 4

In the context of solar resource assessment, what does GHI represent?

Accepted Answer

Global Horizontal Irradiance — total solar radiation on a horizontal surface

Answer

Global Horizontal Irradiance (GHI) is the total shortwave radiation received on a horizontal surface and is the primary metric used in solar resource evaluation and energy yield modeling.

Question 5

What is 'curtailment' in the context of renewable energy systems?

Accepted Answer

Intentional reduction of a renewable generator's output below its available capacity

Answer

Curtailment occurs when grid operators instruct renewable generators to reduce output—often due to transmission constraints or oversupply—resulting in foregone clean energy production.

(EMP) Energy Management Professional Practice Test

(EMP) Energy Management Professional Practice Test

EMP Renewable Energy Systems 3