Commercial and residential building energy labeling

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The percentage share of commercial and residential energy consumption as well has been ... All these use solar energy for water heating and do not contain.
Journal of Scientific & Industrial Research Vol. 64, January 2005, pp 30-34

Commercial and residential building energy labeling M Siddhartha Bhatt1,*, N Rajkumar2, S Jothibasu2, R Sudirkumar2, G Pandian2 and K R C Nair2 1

Central Power Research Institute, Field Engineering Services Division, Sir C V Raman Road, Bangalore 560 080 2 Central Power Research Institute, Energy Research Centre, Sreekariyam, Trivandrum 695 017 Received 13 May 2004; accepted 04 October 2004

The paper presents base line date for labeling residential and commercial office buildings on the basis of electrical energy consumption. The study is based on a sample of eight typical residential buildings in Bangalore and five commercial buildings in New Delhi of varying built-up areas. The overall SEC is in the range 1-3 kWh/ m2/month for residential buildings and 5-25 kWh/m2/month for commercial buildings. If only building energy consumption is considered, it is in the range 0.3-1.0 kWh/m2/month for residential buildings and 3-10 kWh/ m2/month for commercial buildings. SEC/person is in the range of 300-800 Wh/m2/person/month for residential buildings and 3-6 Wh/m2/person/month for commercial buildings. Commercial building energy intensities are higher than domestic intensities. The energy consumption (winter-summer) varies between 30-100 % peak value due to variation in ambient temperature and weather conditions. Keywords: Commercial building, Residential building, Energy labeling

Introduction The percentage share of commercial and residential energy consumption as well has been growing steadily. Between 1980 and 2004 the percentage share in buildings has increased from 12 to 18 per cent. Energy conservation in the commercial and residential building sector is one of the important routes for demand side management of the electricity sector. Energy conservation in this sector can be approached, both from improving the efficiency of installed equipment as well as from improving the system efficiency. Consequent to the passing of the Energy Conservation Bill 2001 and establishment of the Bureau of Energy Efficiency at New Delhi, buildings are being looked upon as a potential sector for energy conservation. The concept of the green building for India is emerging, calling for labeling of energy consumption and establishment of standards for the intensities of energy consumption in these buildings. Commercial buildings are being classified as designated consumers and it is mandatory for them to adhere to minimum building energy consumption norms. The green building concepts in Western countries focus on issues related to thermal insulation, ventilation and room heating systems. Substantial amount of energy are needed for keeping the dwellings warm in temperate and frigid zones. In tropical climates the temperatures being much nearer to comfort temperatures the energy requirements in buildings are much lower. Indian buildings are unique in having low requirements of energy for room heating and cooling as compared to temperate and frigid zones. In India, lighting, comfort air conditioning, and seasonal room heating are of great concern. Hence the green building standards or norms of Western countries1,2 cannot be directly applied in the Indian context. The low energy intensities may give a wrong conclusion that the energy usage is more efficient. This is not the case because the terms of reference and energy use patterns are entirely different. In the Indian context, ambient conditions strongly affect the energy consumption for bathing and air conditioning (cooling). A green building is one where energy concepts are embedded, both during its construction as well as its life long use. In the construction stage, it is built: (i) Smart; (ii) With minimum non-renewable inputs during building; (iii) With minimum pollution during building; and (iv) To ensure comfort, health, and safety of people who will live and work in them. In its lifetime of usage, it involves: (i) Resource conservation; (ii) Energy conservation; (iii) Use of renewable energy; (iv) Water harvesting and recycle; and (v) Energy recycle. In other words, a green building considers the construction, usage and maintenance in its entire life cycle.

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What Constitutes Building Energy? Building energy is composed of energy for: (a) Lighting; (b) Comfort-fanning/air circulation, cooling and heating of conditioned space; (c) Lifts, water pumps; and (d) Losses in the local electrical distribution networkEnergy for end tasks-refrigeration, bath water heating, TV, computers, office equipment, etc., though gets accounted in the building energy consumption and cannot be decoupled, are not actually part of building energy. Building energy depends on factors such as: (i) Ambient temperature; (ii) Weather conditions and daylight hours; (iii) Building design; (iv) Inherent Fig. 1—Variation of air conditioning power with ambient efficiency of equipment used; and (v) Installed efficiency temperature of equipment used. Indices for Labeling of Building Energy Data The indices for quantification of building energy data are as follows: (i) (ii) (iii) (iv) (v) (vi)

Electrical energy consumption (E) (kWh/month); Specific energy consumption (SEC) based on build up area (kWh/m2/month); SEC/person based on build up area [SECp] (Wh/m2/person/ month); Connected load (CL) (kW); Electric power (P) (kW); and Specific power (kW/m2)

Experimental Procedure Two types of buildings are taken up for the study: (i) Commercial office buildings; and (ii) Residential buildings-cottages and multi-storeyed buildings. Commercial office buildings are of build-up area in the range 4,000-50,000 m2 with occupancy of 1,000-5,000 persons at a time. Since the range of variation in ambient temperature is very high in Delhi, the buildings are selected in Delhi for the study. In this study, the sample size is five buildings and the date for the past 2-3 y is considered. The major energy consumption is for window air conditioners in summer and room heaters during winter. The other loads are lighting, lifts, pumps, canteens and office equipment. All-electric residential buildings located in Bangalore are considered with a sanctioned load of 3 kW. The sample size (8 buildings) was found to be adequate for obtaining baseline data. All these use solar energy for water heating and do not contain air conditioners, room heaters or lifts. Results and Discussion Effect of Ambient Temperature

Under variation of theoretical minimum thermal power for comfort air conditioning with ambient temperature, the power varies between 0-0.65 kW/m3 of conditioned space (Fig. 1). When the ambient temperature exceeds 35°C, no additional energy input is needed for bathing energy (Fig. 2). Under thermal energy requirement in India for bathing as a function of the ambient temperature, the variation is observed between 0 and 1.0 kWh/person (Fig. 3). The annual range of ambient temperature3 is 31.4°C in Delhi, whereas it is 18.9°C in Bangalore, and 16.8°C in Mumbai (Table 1). Hence the maximum variation (over the year) in building energy can be expected in Delhi where the temperature ranges between 12-44°C..

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SEC varies between 30-100 per cent of the peak value (Figs 4-6). Power wise, the variation is 70-100 per cent of the peak power. Lighting power is nearly invariant with seasons and the variation is around 10-12 per cent of the peak value. Pumps, lifts, and other mechanical loads, which constitute building energy, are invariant with ambient temperature. During summer, fans and comfort air conditioner loads account for nearly 50-60 per cent of the total power, while during winters, room heaters account for 50-60 per cent of the total power. However, room heaters consume less energy than air conditioners because of lower usage factor and hence winter loads are Fig. 2—Variation of comfortable bathing temperature with lower than summer loads. ambient temperature Break-up of Building Energy Loads

In residential buildings, the building related energy consumption accounts for nearly one-third of the

Table 1Range of ambient temperatures in t S No.

Temperature

Delhi

Mumbai

1

Maximum ambient, °C Minimum ambient, °C Mean ambient, °C Annual range, °C

43.5

38.0

12.1

21.2

13.933.3 31.4

23.9-30.1

2 3 4 Fig. 3—Variation of thermal energy required for bathing with ambient temperature

Fig. 4—Variation of specific energy consumption per unit area with months

Fig. 5—Variation of specific energy consumption with time

16.8

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Fig. 6—Variation of specific energy consumption with time

energy consumption, while the balance is by non-building related equipment (Table 2). In contrast, in commercial office buildings, the building related energy accounts for nearly two-third of the total energy consumption. In other three studies4-6, the break-up of energy consumption in commercial buildings is as follows (respectively): lighting, 27, 60, 30-35; and air conditioners, 40, 32, 40%. Building Energy Indices

Energy intensity in commercial buildings is nearly five times higher than in residential buildings (Table 3). If the comparison is made only on the basis of building related SEC (excluding non-building related installed equipment), then the intensity of energy usage in commercial buildings is nearly ten times than that of residential buildings. The reasons for the higher energy consumption could be: (i) Restricted use of air conditioning in residential buildings; (ii) Weak communication between the source and the load in commercial buildings resulting in wasteful consumption; (iii) Impersonal attitude of the inmates towards the energy charges; (iv) No fine-tuning of equipment design to suit the user requirements; and (v) System is not designed to respond to variations in energy demand.

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Table 2Break-up energy and power demands of residential and commercial office buildings S No

1 2 3 4 5 6 7 8 9

Parameters

Residential Energy % Power %

Lighting Air conditioners Room heaters Fans Air coolers Electric heaters/boosters to solar water heaters Water pumps Lifts Equipment not related to building energy

Commercial office Energy% Power%

20-40 10-15 0-20

10-15 4-6 20-30

15-20 30-40 7-10 2-3 3-5 -

10-15 30-40 8-12 3-5 3-5 -

5-8 50-70

5-10 50-70

1-2 1-2 30-35

1-2 2-3 30-40

Table 3Range of parameters of energy data for residential and commercial buildings S No.

1 2 3 4 5 6 7 8 9 10 11

Parameters

Units

Residential buildings

Commercial buildings

Range of area Range of occupancy Range of overall energy consumption Range of overall specific energy consumption per person Range of overall specific energy consumption Curve fit for overall energy consumption Curve fit for overall specific energy consumption per person Curve fit for overall specific energy consumption per person Specific overall power Building related energy as a percentage of overall consumption Building related SEC (excluding un-connected equipment)

m2 No. of persons kWh/month for residential MWh/month for commercial Wh/ m2/person/month

0-200 2-10 50-250

1,000-50,000 1,000-5,000 5-500

300-800

3-7

kWh/ m2/month

1-3

5-25

kWh/month for residential MWh/month for commercial Wh/m2/person/month

W/m2 %

62.874 + 0.6836 [A] 2593.3 [A-0.4213] 16.138 [A-0.5394] 20-50 30

22.759 +0.0072 [A] 6.5673 [A-0.0352] 7.5427 [A-0.003] 100-350 60

kWh/m2/month

0.3-1.0

3-10

kWh/m2/month

The power intensity of residential buildings is 20-60 W/m2 while that of commercial buildings is 100-350 W/m2. The energy consumption is 1-3 kWh/m2/month for residential buildings while for commercial buildings it is 5-25 kWh/m2/month. In Western countries, the residential consumption is 25-35 kWh/m2/month and efforts are being made to reduce it to around 6 kWh/m2/month7. Bansal7 has estimated the energy consumption for six regions in India (considering heating and cooling energy) as: Leh, 56; Simla, 43; Delhi, 37; Jodhpur, 40; Mumbai, 41; and Bangalore, 15 kWh/m2/month. Another study6 of commercial buildings has estimated the energy consumption as 10-41 kWh/m2/month with a variation of 16 per cent between summer and winter consumption. For a fast food unit, the energy consumption is estimated at 60-94 kWh/m2/month. For star hotels, the energy consumption has been estimated at 35-50 kWh/room/d during winter and 60-80 kWh/room/d in summer. Technologies for reduction of building energy consumption which have been successfully tried in a few sample installations in India are active and passive solar flat plate/transpired collectors, recuperative heat

BHATT et al.: COMMERCIAL AND RESIDENTIAL BUILDING ENERGY LABELING

wheels5, integration of energy efficiency equipment with buildings8, and feed back control sensors9.

Table 4Energy indices for lighting systems S No.

Parameters

Lighting Loads

SEC for lighting is nearly five times in commercial buildings as that of residential buildings (Table 4). The lighting norms are 10 W/m2 in Singapore and 20 W/m2 in the US. The measured lighting power in a typical commercial installation in the US9 is 15.5 to 17.8 W/m2. The Indian lighting intensities are in the range of 20-70 W/m2. Lighting loads can be reduced by controls such as, day light sensors and lighting controls, occupancy sensors, photo sensors, and programmable lighting systems9.

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1 2

3 4

Lighting loads, W/m2 Range of specific energy consumption for lighting systems, kWh/m2/month Norms for lighting in USA, W/m2 Norms for lighting in Singapore, W/m2

Residential buildings

Commercial buildings

4-10 0.2-0.6

20-70 1-3.2

20

20

10

10

Conclusions (i) The overall SEC is in the range 1-3 kWh/m2/month for residential buildings and 5-16 kWh/m2/month for commercial buildings. (ii) If only the building energy consumption is considered, SEC is in the range of 0.3-1.0 kWh/ m2/month for residential buildings and 3-10 kWh/m2/month for commercial buildings. (iii) In residential buildings, the building related energy consumption accounts for nearly one-third of the energy consumption while the balance is by non-building related equipment. In contrast, in commercial office buildings the building related energy accounts for nearly two-third the total energy consumption. (iv) The SEC/person is in the range of 300-800 Wh/m2/person/month for residential buildings and 3-6 Wh/m2/person/month for commercial buildings. Commercial building energy intensities are higher than domestic intensities because of air conditioning of space, weak source-load communication, impersonal attitude of occupants, sluggish response of load variations and no fine-tuning of equipment to suit specific user requirements. (v) Lighting energy intensities are very much on the higher side in the commercial buildings (20-70 W/m2) as compared to international norms calling for task oriented energy efficient lighting with control systems. (vi) The variation of energy consumption is in the range of 30-100 per cent (power: 70-100%) of the peak value due to ambient temperature and weather conditions. References 1 2 3 4 5 6 7 8 9

Energy standards for buildings except for low rise residential buildings, ANSI/ASHRAE /IESNA Standard 90.1-2001 (Office of the Energy Efficiency and Renewable Energy, US Deptt. of Energy , DOE, Chicago) 2001. Building energy codes for residential buildings, commercial buildings and federal buildings, DOE Building Energy Code Programme,(Office of the Energy Efficiency and Renewable Energy, US Dept. of Energy, DOE, Chicago) 2001. Misra A & Hukmani N S, Weather data and ambient design conditions for Indian Stations (WeDCo Database), SESI, 12(1) (2002) 25-36. Banarjee Ranjan, Opportunities in commercial building sector, Bull Ener Efficiency, 3(1) (2002) 6-8. Misra A, Achieving energy efficiency in commercial buildings, Bull Ener Efficiency, 3(1) (2002) 13-15. Ramesh Kumar I V & Satyakumar D V, Bench marking building energy management, Bull Ener Efficiency, 4(1) (2003) 31-33. Bansal N K, Energy conservation in buildings and building establishments, Bull Ener Efficiency, 3(1) (2002) 9-12. Mili Majumdar, Sustainable buildings-building consciously for a better tommorow, Bull Ener Efficiency, 3(1) (2002) 16-17. Anon, Energy efficiency achieved in Richmond City Hall, Bull Ener Efficiency, 3(1) (2002) 21-23.

________ *Author for correspondence Fax: 91-80-23601213

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Table 1Range of ambient temperatures in three cities S No.

Temperature

Delhi

Mumbai

Bangalore

1

Maximum ambient, °C Minimum ambient, °C Mean ambient, °C Annual range, °C

43.5

38.0

36.2

12.1

21.2

18.3

13.933.3 31.4

23.9-30.1

20.5-27.6

16.8

18.9

2 3 4

Table 2Break-up energy and power demands of residential and commercial office buildings S No

1 2 3 4 5 6

Parameters

Lighting Air conditioners Room heaters Fans Air coolers Electric heaters/boosters to solar water heaters

Residential Energy % Power % 20-40 10-15 0-20

10-15 4-6 20-30

Commercial office Energy% Power% 15-20 30-40 7-10 2-3 3-5 -

10-15 30-40 8-12 3-5 3-5 -

BHATT et al.: COMMERCIAL AND RESIDENTIAL BUILDING ENERGY LABELING

7 8 9

Water pumps Lifts Equipment not related to building energy

5-8 50-70

5-10 50-70

1-2 1-2 30-35

1-2 2-3 30-40

Table 3Range of parameters of energy data for residential and commercial buildings S No.

1 2 3 4 5 6 7 8 9 10 11

Parameters

Units

Residential buildings

Commercial buildings

Range of area Range of occupancy Range of overall energy consumption Range of overall specific energy consumption per person Range of overall specific energy consumption Curve fit for overall energy consumption Curve fit for overall specific energy consumption per person Curve fit for overall specific energy consumption per person Specific overall power Building related energy as a percentage of overall consumption Building related SEC (excluding un-connected equipment)

m2 No. of persons kWh/month for residential MWh/month for commercial Wh/ m2/person/month

0-200 2-10 50-250

1,000-50,000 1,000-5,000 5-500

300-800

3-7

kWh/ m2/month

1-3

5-25

kWh/month for residential MWh/month for commercial Wh/m2/person/month

W/m2 %

62.874 + 0.6836 [A] 2593.3 [A-0.4213] 16.138 [A-0.5394] 20-50 30

22.759 +0.0072 [A] 6.5673 [A-0.0352] 7.5427 [A-0.003] 100-350 60

kWh/m2/month

0.3-1.0

3-10

kWh/m2/month

Table 4Energy indices for lighting systems S No.

1 2

3

Parameters Lighting loads, W/m2 Range of specific energy consumption for lighting systems, kWh/m2/month Norms for lighting in 2

Residential buildings

Commercial buildings

4-10 0.2-0.6

20-70 1-3.2

20

20

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4

USA, W/m2 Norms for lighting in Singapore, W/m2

10

10

Figure captions Fig. 1—Variation of air conditioning power with ambient temperature Fig. 2—Variation of comfortable bathing temperature with ambient temperature Fig. 3—Variation of thermal energy required for bathing with ambient temperature Fig. 4—Variation of specific energy consumption per unit area with months Fig. 5—Variation of specific energy consumption with time Fig. 6—Variation of specific energy consumption with time