BerkeleyUNIVERSITY OF CALIFORNIA /

© 2

013

LM

AS

c

onta

ct e

mai

l: Integrated Facility HVAC Energy Consumption Model

Josh

ua M

. Chi

en

lmas

.ber

kele

y@gm

ail.c

om

■  Create a simply yet comprehensive facility (HVAC) energy consumption model

■  Integrate activity (i.e. heat dissipation) during manufacturing via parameterization of a thermodynamic model

Funding Sources: Daimler AG

Objectives

■  Facility level energy consumption is non-negligible ■  Numerous factors involved: location, building type, temperature

and humidity, process equipment, etc. ■  Existing professional software: overly complex; lack parametric

ability for manufacturing, difficult to integrate with other models

Introduction

Model Overview Model Formulation

Sources of Heat Case Study: Vancouver

Results Summary

■  Hybrid model utilizing: ■  Bin Method: piecewise (hour-by-hour) modeling based on

temperature differences ■  Forward modeling: based on thermodynamics and actual

engineering principles (e.g. building design, location, etc.)

■  Determine change in internal stored heat energy ■  ΔE(t)stored = E(t)in – E(t)out + E(t)generated ■  Calculate if heating or cooling is necessary based on the facility

temperature setpoints and the generated heat due to manufacturing

■  Temperature setpoints vary depending on time of day (work vs. non-work hours) and day of year (winter or summer)

■  Input empirical data for outdoor temperature, solar irradiance (direct and diffuse), and outdoor wind velocity

■  Resistive network (1-D): ■  Tou : outdoor temperature ■  Tin : indoor temperature ■  Tro : roof/ceiling temperature ■  Tgr : ground temperature ■  Ti

wa : ith wall temperature ■  Tj

wi : jth window temperature

■  Thermo-energy balance

■  Qs(t): process heat dissipation

■  Solar irradiation and process heat

§  Lighting §  HVAC §  Water heating §  Auxiliary

equipment §  Etc.

Integrate Heat  

Manufacturing

Facility

Total = 14.7 quads (primary)

Miscellaneo u s 14%

H VAC O th er 30%

8%

O ffice Eq u ip m ent

8%

C o o kin g 2% W ater H eatin g

8%R efrig eratio n 4% L ig h tin g

26% Figure 2-1: Commercial Building Primary Energy Consumption Breakdown (from BTS, 2001; ADL, 1999;

ADL, 2001)

Commercial building HVAC primary energy consumption is relatively evenly distributed between heating, cooling, and “parasitic” end-uses (see Figures 2-2, 2-3 and 2-4, from ADL, 1999 and ADL, 2001).

C oo ling En ergy C onsum p tio n T otal 1 .4 qu ad s (prim ary )

Ro tary S crew C h ille rs Rec ipro ca tin g

RAC s 3% C h ille rs 12%Ab s o rp tio n

C h ille rs 2%

C e n tr ifug a l C h ille rs

14%

Heat P u m p 7%

Figure 2-2: Commercial Building Cooling Energy Consumption in 1995 (from ADL, 2001)

P T AC 3%

Un ita ry A/C (Ro o fto p s )

54%

5%

2-2

Source: Roth, K.W. et al. (2002)

0.0  

20.0  

40.0  

60.0  

80.0  

100.0  

120.0  

140.0  

All Buildings

Ener

gy In

tens

ity (k

Wh/

sqft.

)

HVAC Electricity Consumption Intensity

Commercial Building Primary Energy Consumption Breakdown

Source: 2003 CBECS Survey Data (2008)

Tou

Tin,  Mair  

Tgr  

Tro,  Mro  

Tiwa,  Miwa  

Tjwi, Mj

wi

QS t( )− UAdTi t( )i∑ =MCP dT dt

HVAC

Direct

Diffuse

Reflect

Process heat

Jan FebMar Apr MayJun Jul AugSep Oct NovDec Jan0

200

400

600

800

1000

Month

Sola

r Rad

ianc

e (W

/m2)

Solar (direct)Solar (diffuse)

Jan FebMar Apr May Jun Jul Aug Sep Oct Nov Dec Jan−10

−5

0

5

10

15

20

25

30

Month

Tem

pera

ture

(deg

C)

Temp (outside)Temp (ground)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Pro

cess

Hea

t (kW

)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Pro

cess

Hea

t (kW

)

Solar Irradiance Input

Outdoor and Ground Temperature Inputs

Scenario A Input

Scenario B Input

Source: climate.weatheroffice.gc.ca (2013)

Facility HVAC Model

Total Energy Consumption

Scenario A: constant line utilization Scenario B: higher line utilization during colder months

Scenario A Scenario B

Jan Feb Mar Apr MayJun Jul AugSep Oct NovDec Jan−150

−100

−50

0

50

100

Month

Ener

gy C

onsu

mpt

ion

(kW

h)

HeatingCooling

Jan Feb Mar Apr MayJun Jul AugSep Oct NovDec Jan−150

−100

−50

0

50

Month

Ener

gy C

onsu

mpt

ion

(kW

h)

HeatingCooling

64.6 MWh 54.5 MWh Annual Energy Consumption

■  HVAC energy consumption is a complex balance between solar irradiation, outdoor temperature and wind speed, process heat, outdoor air intake, and indoor temperature setpoints

■  Process heat dissipation can play a significant role on the HVAC energy consumption

■  Reduction in the HVAC energy consumption: ■  Optimizing the production scheduling for a given heat profile ■  Incorporating a dynamic air intake controller to balance the

internal heat with with the outdoor air temperature ■  Relaxing the temperature setpoints

■  Model accuracy can be improved: ■  More precise building and HVAC design data ■  Better understanding of ventilation and airflow

requirements, which influences material heat transfer properties

■  HVAC energy dominated by cooling load ■  Shifting manufacturing to higher utilization in the colder months reduced

annual energy consumption by 15% (with same total heat dissipation) ■  Can perform process/scheduling optimization to reduce HVAC heat load

and optimize the outdoor air-intake to reduce cooling load

200  

20  

200  

20  

Ground

Outdoor  air  intake  (e.g.  infiltra=on)  

■  HVAC cooling and heating required to balance internal heat gain

■  Outdoor air intake can be adjusted depending on temperature difference (current model assumes fixed air intake)

■  Outdoor wind changes the building’s heat transfer properties

Building Design

(not  shown:  outdoor  wind    speed  and  direc=on)