CEM Renewable Energy and Cogeneration

Question 1

Combined Heat and Power (CHP) systems improve overall fuel efficiency compared to separate generation because they:

Accepted Answer

Capture and utilize waste heat from electricity generation that would otherwise be rejected

Answer

CHP (cogeneration) recovers waste heat from prime movers (engines, turbines) for space heating, water heating, or industrial processes, achieving overall efficiencies of 65-85% versus 33% for separate generation.

Question 2

The capacity factor of a solar photovoltaic (PV) system represents:

Accepted Answer

Actual annual energy output divided by the energy the system would produce at rated power continuously

Answer

Capacity factor accounts for daily and seasonal variation in solar irradiance; typical US PV systems have capacity factors of 15-25% depending on location and tilt.

Question 3

A wind turbine's power output varies with wind speed according to:

Accepted Answer

A cubic relationship (power ∝ speed³)

Answer

Wind turbine power output is proportional to the cube of wind speed; doubling wind speed increases power output by a factor of 8, making site wind resource critical.

Question 4

Net metering allows facilities with on-site generation to:

Accepted Answer

Credit excess electricity fed back to the grid against future consumption charges

Answer

Net metering policies allow on-site generators to bank excess kWh fed to the grid, offsetting future purchases at retail rates and improving the economics of distributed generation.

Question 5

A microturbine used in CHP applications differs from a reciprocating engine CHP unit in that microturbines:

Accepted Answer

Operate at very high RPM with fewer moving parts and produce lower-temperature exhaust heat

Answer

Microturbines spin at 50,000-120,000 RPM with air bearings (no oil lubrication), have very few moving parts, and produce lower-temperature exhaust (450-600°F) suitable for hot water or low-pressure steam.

CEM - Certified Energy Manager Practice Test

CEM - Certified Energy Manager Practice Test

CEM Renewable Energy and Cogeneration