CEA Energy Modeling & Simulation Tools 5

Question 1

In EnergyPlus, which object defines the performance curve for a centrifugal chiller's coefficient of performance (COP) as a function of part-load ratio?

Accepted Answer

Chiller:Electric:EIR with CurveFit objects

Answer

The Chiller:Electric:EIR object uses bi-quadratic and quadratic performance curves (CurveFit objects) to model COP variation with part-load ratio, entering temperatures, and capacity.

Question 2

What is the key difference between 'occupied' and 'unoccupied' setback schedules in a building energy model?

Accepted Answer

Setback schedules allow space temperatures to drift farther from comfort range during unoccupied hours to save energy

Answer

Temperature setback allows HVAC systems to operate less during unoccupied periods by widening the acceptable temperature range, reducing heating and cooling energy.

Question 3

In energy modeling for LEED compliance, what baseline system type is typically assigned to a building with a single-zone per floor and floor area under 75,000 ft²?

Accepted Answer

System 3 - PSZ-AC (Packaged Single Zone with Air Conditioning)

Answer

ASHRAE 90.1 Appendix G assigns System 3 (PSZ-AC) as the baseline for non-residential buildings with floor area under 75,000 ft² and fewer than 5 stories in climate zones 1-3.

Question 4

What is the purpose of 'shadowing' calculations in building energy simulation software?

Accepted Answer

To compute which surfaces block solar radiation from reaching windows and roof surfaces

Answer

Shadowing calculations determine which building surfaces, overhangs, or neighboring structures obstruct direct solar radiation from reaching specific exterior surfaces at each hour.

Question 5

In eQUEST or EnergyPlus, what does 'part-load ratio' (PLR) of HVAC equipment represent?

Accepted Answer

The ratio of actual load served to the equipment's full rated capacity

Answer

PLR is the fraction of rated capacity at which equipment operates at a given instant; PLR = 1.0 means full load while lower values indicate partial-load operation with different efficiency characteristics.

(CEA) Certified Energy Analyst Practice Test

(CEA) Certified Energy Analyst Practice Test

CEA Energy Modeling & Simulation Tools 5