DCV Energy Performance Analysis - California

Persily et al. [5] modeled DCV with various assumed minimum ventilation rates when CO2 concentrations did not exceed the maximum CO2 set point. The minimum ventilation rates modeled were as follows:
  • DCV 1. No minimum ventilation.
  • DCV 2. A minimum ventilation rate of 25% of the rate specified in ASHRAE Standard 62-2001.
  • DCV 3. A minimum ventilation rate per floor area based on the requirements in ASHRAE Standard 62-2001.
  • DCV 4. A minimum ventilation rate per floor area based on the requirements in California’s Title 24 Standards.
A fixed minimum ventilation rate as specified in ASHRAE Standard 62-2001 [6] was the reference case.

For the first three DCV options listed above, the maximum CO2 concentration was the concentration predicted at steady state with design occupancy and a fixed ventilation rate as specified in ASHRAE Standard 62.1-2001. For the final DCV option listed above, the maximum CO2 concentration was 800 ppm.

Only DCV 4 complied with Title 24 standards (Figure 1). The percentage reductions range from -17% to 0% for the office building, 64% to 72% for the conference room, 32% to 43% for the lecture hall, 40% to 60% for the classroom, 13% to 25% for the portable classroom, and 52% to 76% for the fast food restaurant. The report by Persily et al. [5] also provides additional details, including the predicted heating, sensible cooling, and latent cooling loads.

Table 1 provides the estimated total heating and cooling loads for the four California cities (Bakersfield, Los Angeles, Sacramento, and San Francisco) and the percentage reductions in these loads when applying the three DCV options. Note that these numbers pertain to heating and cooling loads which differ from energy consumed due to the efficiencies of heating and cooling equipment. For example, combustion heating systems have an efficiency less than unity while cooling systems have a coefficient of performance greater than unity. 

Table 1. Ventilation Heating and Cooling Load (MJ/m2)
(a) Office Building

 BakersfieldLos AngelesSacramentoSan Francisco
DCV 12617 
DCV 2275171
DCV 3194121
DCV 4357211

(b) Conference Room

 BakersfieldLos AngelesSacramentoSan Francisco
DCV 11114110473
DCV 215156145106
DCV 3304224
DCV 41294812285

(c) Lecture Hall

 BakersfieldLos AngelesSacramentoSan Francisco
DCV 1568219537428
DCV 2645248614502
DCV 32424021595
DCV 4714302687585

(d) Classroom

 BakersfieldLos AngelesSacramentoSan Francisco
DCV 197198744
DCV 2105219345
DCV 388168033
DCV 41192310853

(e) Portable Classroom

 BakersfieldLos AngelesSacramentoSan Francisco
DCV 164176137
DCV 271176540
DCV 376177244
DCV 494279263

(f) Fast Food Restaurant

 BakersfieldLos AngelesSacramentoSan Francisco
DCV 1516158489381
DCV 2574180550442
DCV 32222917450
DCV 4490125465345