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Energy Efficiency in Commercial Buildings
Cities contribute significantly to the growth of any country's economy. At present, Indian cities contribute to 60% of the country’s gross domestic product (GDP), and by 2030 this percentage is expected to increase to 70. Due to the swift urban sprawl and transformation of cities into economic hubs, India is facing the challenge of urgent development of urban infrastructure such as housing, office spaces, mobility, and energy generation and distribution.
As per the Twelfth Five-year Plan (2012–17), commercial building is defined as any building, which is neither used for residential nor for industrial purposes. These building types include offices, hospitals, hotels, retail outlets, educational buildings, government offices, and so on. According to Energy Conservation (EC) Act 2001, ‘building’ means any structure or erection or part of a structure or erection, after the rules relating to energy conservation building codes have been notified under clause (a) of section 15 of clause (l) of sub-section (2) of section 56, which is having a connected load of 500 kW or contract demand of 600 kVA and above and is intended to be used for commercial purposes. An amendment was made to the EC Act in 2010, which states that ‘Commercial buildings which are having a connected load of 100 kW or contract demand of 120 kVA and above come under the purview of ECBC under EC Act.
Commercial buildings can be broadly categorized into three based on:
1. the number of functions it serves,
2. the ownership, and
3. the operating hours.
Based on the number of functions it serves, they can be classified into two, as given below.
a) Single function building (buildings used for only as offices, hotel, hospital, etc.)
b) Multiple functions building (buildings catering to two or more building functions such as shopping and hotel, shopping and offices, etc.)
Based on the ownership, buildings can be classified again into two.
a) Owner-occupied building, where the owner invests money for the building design and construction and finally occupies and operates the building. In this building, the benefits of upfront capital investment on energy efficiency measures will be directly appreciated by the owner.
b) Core and shell building, where the developer invests on the building design and construction and finally rent, lease or sell to single or multiple tenants. In this building, the benefits of capital investment on energy efficiency measures will be enjoyed by the tenants. Due to this split benefit, the developer of the Core and Shell project is often reluctant to invest on energy conservation measures unless higher premium on the project is assured.
Based on the operating hours, a building can fall into the following four categories.
a) Single shift operation (~8 hours)
b) 1½ shift operation (~14 hours)
c) Double shift operation (~16 hours)
d) Triple shift operation (~24 hours)
The commercial building sector consumes about 8% of the total electricity generated in India and this is growing at 11%–12% annually. Based on the study conducted by ECO III project on estimation of commercial floor space in India, the total built-up area of commercial buildings will be 763 million square metres by 2013 (extrapolated considering 5% as CAGR). It is expected that the commercial stock will annually increase by 3%–5%. According to the study on building energy benchmarking conducted by ECO III project, the average energy performance index (EPI) for commercial buildings will be ~70 kWh/m2/year.
The above plot summarizes the EPI range for various commercial building types. It can be seen that ‘public sector office buildings’ have EPI of ~100 kWh/m2/annum; this may be associated with relaxed acceptable thermal comfort requirements in public office buildings and less air-conditioned area. The EPI of ‘three-shift commercial office buildings’ has been benchmarked at 350 kWh/m2/annum. This is primarily due to extended operation timing of these building. Shopping malls have EPI of around 250 kWh/m2/annum; this is due to excessive air-conditioned areas. By integrating energy conservation measures mentioned in the Energy Conservation Building Code (ECBC), it is expected that the overall energy requirement for commercial buildings can be reduced by 30%–40%.
Energy Conservation Building Code
In 2001, the EC Act was introduced by the Government of India to emphasize the national priority on energy efficiency in all sectors. Under the provisions of the EC Act, the Bureau of Energy Efficiency (BEE) was established in 2002. The BEE is mandated to reduce the energy intensity of the Indian economy by actively working with stakeholders to accelerate the adoption of energy efficiency measures.
For mainstreaming the energy efficiency in the building sector, the BEE has introduced ECBC in May 2007. This is applicable to both new buildings and those undergoing renovation. The ECBC is applicable to buildings or building complexes with the connected load of 100 kW or greater or contract demand of 120 kVA or greater.
Currently, the ECBC is in voluntary implementation phase and the compliance rate is forecasted to increase gradually from 10% until 2013 to 35% in 2015 and 65% by 2017. The ECBC provides both requisite and prescriptive requirements for five building components, namely (a) Building Envelope, (b) Heating, Ventilation and Air Conditioning (HVAC), (c) Service Water Heating and Pumping (d) Lighting, and (e) Electrical Power. For compliance with ECBC, the project can adopt either the ‘prescriptive method’ or ‘whole building performance method’. The trade-off method is available only for building envelope category. Online conformance tools ‘ECOnirman Prescriptive’ and ‘ECOnirman Whole Building Performance’ can be used to show compliance with ECBC requirements.
BEE Star Rating for Buildings
The BEE has introduced the star labeling programme for existing commercial buildings, which provides label to the buildings based on their actual energy performance. The BEE star labeling is applicable to buildings with the connected load of 100 kW or greater or contract demand of 120 kVA or greater. One to five stars are awarded to the buildings based on their specific energy use with five star label recognized as the most efficient building. A standardized format of data collection of actual energy consumption of the building was developed to collect information pertaining to building built-up area, conditioned and non-conditioned areas, type of building, hours of operation of building in a day, climatic zone, and other information related to facility.
Currently, this rating is applicable to office buildings, business process outsourcing (BPO) buildings, and shopping malls. In future, the BEE would extend the star labeling to hotels and hospitals.
For office buildings and shopping malls, the EPI in kWh/m2/year is considered for the building energy performance, while for BPO buildings the average annual hourly EPI (AAhEPI) in Wh/h/m2 will be used to report the building energy performance. Both grid and captive electricity will be considered for the calculation of EPI and AAhEPI but this will exclude on-site renewable energy production such as photovoltaic. The rated project has to submit the details of the energy consumption annually to show its conformance to the awarded rating.
For office buildings, the EPI bandwidth for three climatic zones in India (composite, warm-humid, and hot and dry) are provided for two categories (more than 50% air-conditioned built-up area and less than 50% built-up area). The EPI bandwidth for shopping malls and AAhEPI bandwidth for BPO buildings are also collated based on the four climatic zones in India (composite, warm-humid, hot and dry, and temperate). As per BEE website in January 2014, 108 buildings are awarded with BEE star label.
Building Rating Systems
There are three voluntary rating systems applicable for building design. These are
- Leadership in Energy and Environmental Design (LEED)/Indian Green Building Council (IGBC)
- Green Rating for Integrated Habitat Assessment (GRIHA)
LEED India or GRIHA pre-certified projects will get opportunity for out-of-turn environmental clearance. This fast-track clearance would be applicable for building projects with the total built-up area ≥20,000 m2 to <1,50,000 m2.
Integrated Design Charrette
BEEP will organize integrated design charrette for 24 large commercial projects at their early design stage to make them energy efficient. Design charrette is conceptualized as a four-day workshop where a team of senior Swiss architect, senior Swiss engineer, and Indian experts works with the local project team to develop an energy efficiency concept for the project. Design charrettes will be organized for both public and private projects. Projects are selected based on the expression of interest received from the project proponents or developers.
Request for ‘Expression of Interest’ (EoI) is shared periodically with developers, developer's association, state designated agencies (SDAs), and public sector undertakings (PSUs).
Integrated Design Seminar
BEEP will conduct 16 integrated design seminars to disseminate the knowledge and experience of high performance building designs. The seminars will be targeted at architects, planners, builders, developers, engineers, and government officials.
External Movable Blind
External movable blinds are innovative technology, which are used for the dynamic protection of buildings from excessive solar gains. In several European countries, they have become a mainstream practice. In Switzerland, they are compulsory for cooled commercial buildings. In India, the use of this technology is at a very initial stage. Therefore, a design competition for external movable shading systems is proposed forinducing the development of an India-based production of external movable shading devices.
Earth Air Tunnel (EAT)
The EAT technology is a promising low-energy technology for conditioning of buildings. A dimensioning tool will be developed on the basis of an existing tool created by Dr Pierre Hollmuller of the University of Geneva.
Based on his research, he has developed a Microsoft Excel-based simplified design and dimensioning tool, and TRNSYS-based simulation tool. Using the monitored data from the two EATs in Indian tropical climate, he has adopted the tool for Indian climatic conditions.