ENERGY_EFFICIENCY_IN_ELECTRICAL_UTILITIES
(Chapter 10:Energy conservation in Buldings and ECBC)
Introduction
There are several different uses of energy in buildings. The major uses are for lighting, heating, cooling, power delivery to equipment and appliances, and domestic water. The amount that each Contributes to the total energy use varies according to the climate, type of building, number of working hours and time of year. Energy use for air-conditioning has the largest share at a national level. In areas where severe winters occur, heating load will be greater than cooling load in terms of the total energy use.
In some types of buildings in certain climatic zones, the lighting load might be greater than either the heating or cooling loads. Industrial and commercial buildings are dissimilar in terms of energy use, as industries primarily use large quantities of energy for specialized processes whereas buildings use the major amount of energy for human comfort. It is difficult to generalize energy use by type of building because there are many variables that determine the energy use in a particular building.
Building Definition as in the Energy Conservation (amendment) Act 2010
“building” means any structure or erection or part of structure or erection after the rules relating to energy conservation building codes have been notified under clause (p) of section 14 and clause (a) of section 15 and includes any existing structure or erection or part of structure or erection, which is having a connected load of 100 Kilowatt (kW) or contract demand of 120 Kilovolt Ampere (kVA) and above and is used or intended to be used for commercial purposes.
Energy Conservation Building Code (ECBC)
Energy Conservation Building Code defines the minimum energy efficiency standards for design and construction of commercial buildings, to encourage energy efficient design or major retrofit of Buildings without any compromise with the building function, comfort, health, or the productivity of the occupants.
In order to implement ECBC across the country, India has been divided into five climatic zones as per the weather conditions (Figure 10.1). The Five Climatic zones are:
1.Composite
2. Hot Dry
3.Warm Humid
4. Moderate
5. Cold
The ECBC Building Code considers the following aspects of the Buildings:
a) Building envelopes, except for unconditioned storage spaces or warehouses,
b) Mechanical systems and equipment, including heating, ventilation, and air conditioning,
c) Service hot water heating,
d) Interior and exterior lighting, and men Hot dry
e) Electrical power and motors.
a) Buildings that do not use either electricity or fossil fuel,
b) | Equipment and portions of building systems that use energy primarily for manufacturing processes
Compliance Approaches
The Code requires that the building shall comply first with all the mandatory provisions discussed in Chapter 4 to 8 (of the Code). But every building project is different: each building has its own site that presents unique opportunities and challenges, each building owner or user has different requirements, and climate and microclimate conditions can vary significantly among projects. Architects and engineers need flexibility in order to design buildings that address these diverse requirements. The Code provides this flexibility in a number of ways. Building components and systems have multiple options to comply with the Code requirements. To use the building envelope section as an example, designers can choose the Prescriptive Method that requires roof insulation be installed with a minimum R-value. Alternatively, the other options allow the designer to show compliance with the thermal performance (U-factor) of roof construction assembly. In addition building envelope tradeoff option discussed in Chapter 4 permits trade-offs among building envelope components (roof, walls, and fenestration) for Code compliance. If more flexibility is needed, the Whole Building Performance (WBP) Method approach may be used, but WBP requires simulation expertise.
a. Prescriptive Method
The Code specifies a set of prescriptive requirements for building systems and components. Compliance with the Code can be achieved by meeting or exceeding the specific levels described for each individual element of the building systems, covered in Chapter 4 through Chapter 8 of the Code. For building envelope, the Code provides a Trade-Off option that allows trading off the efficiency of one envelope element with another to achieve the overall efficiency level required by the Code. The envelope tradeoff option is discussed in Chapter 12: Appendix D of ECBC.
b. Whole Building Performance Method
Use of energy simulation software is necessary to show ECBC compliance via the Whole Building Performance Method. Energy simulation is a computer-based analytical process that helps building owners and designers to evaluate the energy performance of a building and make it more energyefficient by making necessary modifications in the design before the building is constructed.
These computer-based energy simulation programs model the thermal, visual, ventilation, and other energy consuming processes taking place within the building to predict its energy performance. The simulation program takes into account the building geometry and orientation, building materials, building facade design and characteristics, climate, indoor environmental conditions, occupant activitiesand schedules, HVAC and lighting system and other parameters to analyze and predict the energy performance of the building. Computer simulation of energy use can be accomplished with a variety of computer software tools and in many cases may be the best method for guiding a building project to be energy-efficient. However, this approach does require considerable knowledge of building simulation tools and very close communication between members of the design team.
Appendix B of the Code describes the Whole Building Performance Method for complying with the Code. This method involves developing a computer model of the Proposed Design and comparing its energy consumption to the Standard Design for that building. Energy consumption in the Standard Design represents the upper limit of energy use allowed for that particular building under a scenario where all the prescriptive requirements of the Code are adopted. Code compliance will be achieved if the energy use in Proposed Design is no greater than the energy used in the Standard Design.
Three basic steps are involved:
1. Design the building with energy efficiency measures; the prescriptive approach requirements
provide a good starting point for the development of the design.
2. Demonstrate that the building complies with the mandatory measures.
3. Using approved simulation software, model the energy consumption of the building using the proposed features to create the Proposed Design. The model will also automatically calculate the energy use for the Proposed Design.
If the energy use in Proposed Design is lesser than the energy use in the Standard Design, the building
complies with the Code.
ECBC Guidelines on Building Envelope
The building envelope refers to the exterior facade, and is comprised of walls, windows, roof, skylights, doors, and other openings. The envelope protects the building’s interior and occupants from the weather conditions and other external elements. The design features of the envelope strongly affect the visual and thermal comfort of the occupants, as well as energy consumption in the building.
Building Envelope
The Exterior and semi-exterior portions in the context of defining as building envelope include:
o Elements that separate the conditioned spaces from the weather conditions, or
o Elements ofa building that separate the conditioned spaces of the building from the unconditioned spaces, 1.e. office space from unconditioned storage.
Building Envelope Sealing
The following areas of the enclosed building envelope shall be sealed, caulked, gasketed, or weatherstripped to minimize air leakage:
a) Joints around fenestration and door frames,
b) Openings between walls and foundations and between walls and roof and wall panels,
c) Openings at penetrations of utility services through, roofs, walls, and floors
d) Site-built fenestration and doors,
e) Building assemblies used as ducts or plenums, and
f) All other openings in the building envelope.
Envelope design Basics
From an energy efficiency point of view, the envelope design must take into consideration both the external and internal heat loads, as well as day lighting benefits. External loads include mainly solar heat gains through windows, heat losses across the envelope surfaces, and infiltration in the building. Internal loads include heat gain from electric lighting systems, equipment, and people working in the building.
One of the goals of the envelope design should be to introduce day lighting into the interior space of the building through windows and skylights, thereby reducing the need for electric lighting. Thus, giving proper orientation to the building and due consideration to the size and placement of windows at the design stage can provide the advantage of day lighting.
Secondly, to maintain thermal comfort and minimize internal cooling / heating loads, the building envelope needs to regulate and optimize heat transfer through roof, walls, windows, skylights, doors and other openings. Effective insulation of roof and walls, appropriate selection of glazing and framing
for windows, and suitable shading strategy are important in designing energy efficient buildings.
Passive Solar Design Strategy
Architects should pay attention to the following basic design elements in an effort to reduce the energy
consumption in small commercial buildings that can be operated without Central HVAC System.
Siting and Orientation
In a predominantly hot climate, cooling load affects the total energy consumption in commercial buildings in a significant manner. Thus, controlling heat transfer through the roof, walls, and windows becomes of utmost importance and needs to be considered from the initial stages of design. Therefore, site planners and designers should properly orient buildings to minimize solar gains in the summer. Plot lines and roads should be situated to minimize building exposure to the east and west. These orientations provide the highest solar heat gains. Subdivisions should be planned so that the longer sides of the buildings face north and south. With proper planning, there may be no added costs for good orientation.
Shade
Use different shading strategies to minimize solar heat gain and reduce glare inside buildings. Provide
vertical louvers on east and west side and horizontal shading devices on south side.
Cross-Ventilation
Building envelope should allow the movement of breeze throughout the building.
Cool Roof
This refers to the property of roof that describes its ability to reflect and reject heat. Cool roof (Figure
10.2) surfaces have both high solar reflectance and a high emittance (reject heat back to the environment).
Solar Reflectance and Absorptance
The solar reflectance is the fraction of solar radiation reflected by roof. The complement of reflectance
is absorptance (Figure 10.3); whatever radiant energy incident on a surface that is not reflected is absorbed in the roof. The reflectance and absorptance of building materials are usually measured across the solar spectrum, since these are exposed to that range of wavelength. Reflectance is measured on a scale of 0 to 1, with 0 being a perfect absorber and 1 being a perfect reflector. Absorptance is also rated from 0 to 1, and can be calculated from the relation:
Reflectance + Absorptance = 1.
Thermal Emittance
Thermal emittance is the relative ability of a material to radiate the absorbed heat (Figure 10.3). Emissivity (or thermal emittance) of a material is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. It is a measure of a material’s ability to radiate the absorbed energy. A true black body would have an e =1 while any real object would have e <1. Emissivity is a dimensionless quantity (does not have units). In general, the duller and blacker a material is, the closer its emissivity is to 1. The more reflective a material is, the lower its emissivity. The emissivity of building material, unlike reflectance, is usually measured in the far infrared part of the spectrum.
Solar Heat Gain Coefficient (SHGC)
Regardless of outside temperature, heat can be gained through windows by direct or indirect solar radiation. The ability to control this heat gain through windows is characterized in terms of the SHGC of the window. SHGC is the ratio of solar heat gain that passes through fenestration to the total incident
solar radiation on the fenestration (Figure 10.4). Solar heat gains includes directly transmitted solar heat and absorbed solar heat, which is re-radiated, conducted, on convected into the interior space.
Visible Light Transmittance (VLT)
It is the ratio of light passing through the glazing to light passing through perfectly transmissive glazing (Figure 10.4). VLT is concerned only with the visible portion of the solar spectrum, as opposed to SHGC, which is the ratio of all solar radiation. VLT is an important parameter for day lighting of
buildings.
Fenestration
Fenestration systems include windows, skylights, ventilators, and doors that are more than one-half
glazed. All openings (including the frames) in the building envelope that let in light.
Skylight
A fenestration surface having a slope of less than 60 degrees from the horizontal plane (Figure 10.5).
Vertical Fenestration
All fenestration other than skylights.
Fenestration Area
Total area of the fenestration measured using the rough opening (including glazing, sash and frame). For glass doors where glazed vision area is less than 50% of the door area, the fenestration area is the glazed vision area; otherwise, it is the door area.
Window-Wall Ratio (WWR)
Ratio of vertical fenestration area to gross exterior wall area. Gross exterior wall area is measured horizontally from the exterior surface; it is measured vertically from the top of the floor to the bottom
of the roof.
Effective Aperture of Glazing
In simple terms, as the area of an aperture /opening in the building envelope increases, the amount of
daylight received in the building space also increases. However the glazing material within that aperture can effectively reduce the amount of visible light that enters the space. Therefore, aperture size alone is not an effective determinant to measure illumination levels. If the glazing in an opening is perfectly transparent material the effective aperture size would be equal to the area of opening (because the visible transmittance of the glazing would be one). If however the glazing has a VLT of 0.5, the opening will transmit only half of the light striking it, and the effective aperture will be half of the actual size of the opening.
The Effective Aperture (EA) or light admitting potential of a glazing system is determined by multiplying the Visible Light Transmittance of the glazing by the window-to-wall ratio (WWR) of the building. The window to wall ratio is the net window area to the exterior wall area. This value is given as equal to Visible Light Transmittance X Window-Wall Ratio.
EA=VLT X WWR
Example:
Case 1:
WWR = 0.4
VLT = 0.26
EA = 0.4x0.26 = 0.104
EA > 0.1 Glazing complies with ECBC
Case 2:
WWR= 0.6
VLT = 0.15
EA = 0.6x0.15 = 0.09
EA < 0.1 Glazing does not complies with ECBC
The value of VLT is taken from the ECBC for different Window to Wall Ratio (WWR).
Opaque Wall:
All areas in the building envelope, except fenestration and building service openings such as vents
and grills.
Sound Transmission
An important requirement in some type of projects like theaters, hotels, where Energy efficient glazing
delivers improved acoustic performance as a side benefit.
Spectral Selectivity
This refers to the ability of a glazing material to respond differently to different wavelengths of solar energy. In other words, to admit visible light while rejecting unwanted invisible infrared heat. Newer glazing products have achieved this characteristic, permitting much clearer glass than previously available for solar control glazing. A glazing with a relatively high Visible Light Transmittance (VLT)
and a low Solar Heat Gain Coefficient (SHGC) indicates that a glazing use special absorbing tints or
coatings, and are typically either clear or have a blue or blue/green appearance.
Weather stripping
Materials, such as a strip of fabric, plastic, rubber or metal, or a device used to seal the openings, gaps
or cracks of venting window and door units to prevent water and air infiltration.
U-Factor (W/m? k)
When there is a temperature difference between inside and outside, heat is lost or gained through the
window frame and glazing by the combined effects of conduction, convection, and long wave radiation.
U-factor is the rate of heat flow through one square meter of wall/fenestration assembly when there is
1°C temperature difference. The lower the U-factor, the lesser heat transfer takes place. Center-of-glass
U-factors are generally lower than whole-window U-factors, which account for the effect of the frame
and mullions. This property is important for reducing heating load in cold climates and for reducing
cooling load in hot climates.
Roof and opaque wall’s U-factor also refers to the amount of heat transferred (lost/gain), due to a
temperature differential of 1°C between inside and outside, per square meter.
The overall heat transfer coefficient and the insulation resistance for walls and roofs are indicated in
Table 10.1 & 10.2. The vertical fenestration U factor and SGHC requirements as per ECBC guidelines
are given in Table 10.3.
Compliance Approaches
After establishing the specific climate zone in which the building is located, determine which compliance approach is the best fit for envelope design. The ECBC allows the following approaches: Prescriptive Approach: prescribes the minimum performance requirements for each building component.
It is quick and easy to use, but this approach is somewhat restrictive because requirements have to be
met exactly as specified.
The prescriptive requirements for walls, roof and fenestrations are climate-based and different for buildings used during the daytime, and those with 24-hours of use. Roofs and Opaque Walls should meet maximum U-factors for assemblies or minimum R-values for the insulation only [ECBC 4.3.1
and 4.3.2].
Cool Roof should meet minimum solar reflectance of 0.7 and initial emittance levels of not less than 0.75, and determined in accordance with specified standards. [ECBC 4.3.1.1] Skylights should meet maximum U-factor and SHGC with skylight area limited to a maximum of five percent of the gross roof area [ECBC 4.3.4].
Envelope Trade-off Approach: allows the designer to trade enhanced energy efficiency in one building component against decreased energy efficiency in another component, thereby offering flexibility. These trade-offs are applicable only within major envelope components 1.e., roof, walls and fenestration.
Appendix D of ECBC provides guidance on the calculation of the Envelope Performance Factor (EPF).
This is calculated for the proposed design and for the baseline design, for compliance. The proposed building’s EPF must be equal to or better than that of the baseline design.
Whole Building Performance: Approach compares the proposed design with a standard design (same building meeting all the prescriptive requirements of ECBC) and demonstrates that the estimated annual energy use of proposed design is less than that of the standard design. This approach allows great flexibility but requires considerably more effort. Computer-based Energy Simulation Program can be helpful in this exercise.
This approach (Appendix B of ECBC) requires computer-based energy simulation program to determine and compare the estimated annual energy use of the proposed design with that of a standard design.
ECBC Guidelines on Heating Ventilation and Air conditioning System
Heating ventilation and air conditioning (HVAC) refers to the equipment, distribution systems and terminals that provide HVAC requirement of the building. The best HVAC design considers all the interrelated building systems while addressing indoor air quality, thermal comfort, energy consumption
and environmental benefits.
The Energy Conservation Building Code (ECBC) covers several prescriptive requirements for HVAC systems including requirements for economizer, duct and pipe insulation, controls optimization, and system balancing.
Equipment Efficiency
HVAC equipment is required to meet or exceed minimum efficiency requirements mentioned in ECBC
5.2.2. Power consumption ratings for unitary air conditioners, split systems and packaged air conditioners are referred to BIS codes. Cooling systems not included are referred to ASHRAE 90.1 — 2004. Single zone unitary systems are covered as well as multiple zone air and water systems. The more complex the system, the more requirements apply to that system: a single-zone unitary system has fewer requirements than a complex system made up of chillers, boilers, and fan coil units. For natural ventilation requirements, buildings are required to follow the design guidelines provided for natural ventilation in the National Building Code of India, 2005 [ECBC 5.2.1].
Controls
Controls determine how HVAC systems operate to meet the design goals of comfort, efficiency, and
cost-effective operation. The ECBC requires that all HVAC equipment (>28 kW cooling and/or >7kW heating capacity) be controlled with a time clock capable of retaining programming for at least 10 hours, controlling varying schedules. [ECBC 5.2.3]
All heating and cooling systems are required to be temperature controlled [ECBC 5.2.3]. Each zone must be controlled by an individual temperature controller. A temperature of dead band of 3°C (5°F) is required for equipment that supplies both heating and cooling. Thermostats must also prevent simultaneous heating and cooling. [ECBC 5.2.3.2].
Distribution System
Distribution systems carry a heating or cooling medium to condition the space. The two most common
mediums are air and water. Air-based systems are often “forced air” because they use a fan to push the air from the furnace or air conditioner through the duct work to the conditioned space. Water-based systems are often called hydronic, and steam based systems are called steam systems, both of which use a piping system to circulate water or steam.
Forced hot air systems are more common than hydronic or steam heating systems because they cost much less to install. However, hydronic systems perform better than forced hot air because they leak less heat, are easier to insulate, make almost no noise, can be easily zoned and can provide more even temperatures. Hydronic systems also do a much better job of serving a radiant heating system.
The energy efficiency of a distribution system depends largely on the design and installation quality. Duct distribution systems are prone to the most significant losses - especially if the ducts are poorly sealed and/or installed outside the “thermal envelope” of the building (in an unconditioned attic, for example). Hydronic systems are typically installed within conditioned or “buffered” spaces like an unconditioned basement. In either case, it is important to insulate ducts/ hot water pipes that are in unconditioned spaces.
The ECBC requires insulating ducts and pipelines to reduce energy losses in heating and cooling distribution systems. Insulation exposed to weather is required to be protected by aluminum sheet metal, painted canvas, or plastic cover. Cellular foam insulation needs to be protected as described above, or be painted with water retardant paint.
Duct sealing: Duct sealing applies to supply and return duct work and to plenums that are formed by part of the building envelope. Proper duct sealing ensures that correct quantities of heated or cooled air is delivered to the space, and not be lost to unconditioned spaces or the outdoors through leaks in the ducts.
This may be one of the most important conservation features to check. A properly sealed duct system will increase the comfort and lower the energy use of the building. Some areas to be sealed include:
¢ Longitudinal seams are joints oriented in the direction of air flow.
e Transverse joints are connections of two duct sections orientated perpendicular to airflow.
¢ Duct wall penetrations are openings made by any screw or fastener.
e Spiral lock joints in round and flat oval duct need not be sealed.
Pipe insulation: To minimize heat losses, the Code requires that piping of heating and cooling systems,
(including the storage tanks,) must be insulated. The Code specifies required R-values of insulation
for heating and cooling systems based on the operating temperature of the system.
Air System Balancing
Air balancing is a small part of the building commissioning process. Commissioning involves the functional testing of all components of an HVAC system to insure proper operation. Commissioning is a systematic process of verification and documentation from the design phase to a minimum of one year after the construction that all systems perform in accordance with design documentation and intent, and in accordance with the operational needs. The air-balancing portion of the commissioning process is usually done at the completion of a new construction project.
Air balancing should verify damper operation and adjust settings to deliver the designed airflow to each zone. It is important that some balancing be done prior to occupancy for several reasons. Some equipment has minimum airflow requirements across the coils to avoid compressor damage. The total supply, return, and outside airflow quantities should be measured for each air handling system. The ECBC requires that air systems be balanced in a manner to first minimize throttling losses; then for fans > 0.75 kW (1.0 HP) the fan speed needs to be adjusted to meet design flow conditions. [ECBC 5.2.5.1.1].
Hydronic System Balancing
A balanced hydronic system is one that delivers even flow to all the devices on that piping system. Each component has an effective equal length of pipe on the supply and return. And when a system is balanced, all of the pressure drops are correct for the devices. When that happens, the highest efficiencies are possible in the system, which translates into reduced pumping costs.
ECBC requires hydronic systems to be proportionately balanced in a manner to first minimize throttling losses; then the pump impeller must be trimmed or pump speed adjusted to meet the design flow conditions [ECBC 5.2.5.1.2].
The ECBC addresses Variable Flow Hydronic Systems [ECBC 5.3.2] in several ways. First, it requires that pump flow rates be controllable to either 50% of the design or the minimum required by the equipment manufacturer for proper operation of the chillers or boilers. Second, the ECBC requires that circulation pumps > 3.7 kW (5 HP) in water-cooled air-conditioning units or heat pumps contain a two-way automatic isolation valve to shut off the condenser water flow when the compressor is not operating [ECBC 5.3.2.2]. Thirdly, the ECBC requires pump motors in all hydronic systems > 3.7 kW (5 HP) shall be controlled with variable speed drives [ECBC 5.3.2.3]. While throttling reduces the flow, the motor is still running at full speed and works even harder as it has to work against a restriction. By reducing the speed of the motor, the variable speed drive ensures reduction in energy consumption while maintaining the required flow.
Scale Control in Water Circuit
In a water-cooled air-conditioning system, heat is rejected from the refrigerant to the cooling water in the condenser. The impurities in the cooling water circuit get accumulated, and thus the scales and deposits are built up in the condenser tubes, creating scaling problems on the condenser heat transfer surfaces. This reduces the heat transfer efficiency of the condenser and thus increases chiller energy consumption. The ECBC requires [ECBC 5.2.6.2] use of soft water for condensers and chilled water systems to reduce scale formation.
Economizers
An economizer is a collection of dampers, sensors, actuators, and logic devices that together decide how much outside air to bring into a building. When the outdoor temperature and humidity are mild, economizers save energy by cooling buildings with outside air instead of by using refrigeration equipment to cool recirculated air. A properly operating economizer can cut energy costs by as much as 10 percent of a building’s total energy consumption, depending mostly on local climate and internal cooling loads. ECBC requires an economizer for cooling systems over 1,200 liters/sec (2,500 cfm) fan capacity and with a cooling capacity > 22 kW [ECBC 5.3.1.1].
ECBC Guidelines on Service Hot Water
Solar Water Heating
Residential facilities, hotels and hospitals with a centralized system shall have solar water heating for at least 20% of the design capacity.
Supplementary Water Heating System
Supplementary heating system shall be designed to maximize the energy efficiency of the system and shall incorporate the following design features in cascade:
a. Maximum heat recovery from hot discharge system like condensers of air conditioning units,
b. Use of gas fired heaters wherever gas is available, and
C. Electric heater as last resort.
Piping Insulation
The entire hot water system including the storage tanks, pipelines shall be insulated conforming to the
relevant IS standards on materials and applications.
Heat Traps
Vertical pipe risers serving storage water heaters and storage tanks not having integral heat traps and serving a non-recirculating system shall have heat traps on both the inlet and outlet piping as close as practical to the storage tank.
Swimming Pools
Heated pools shall be provided with a vapor retardant pool cover on or at the water surface. Pools heated to more than 32°C (90°F) shall have a pool cover with a minimum insulation value of R-2.1 (R-12).
ECBC Guidelines on Lighting
Lighting systems shall apply to:
a. Interior spaces of buildings,
b. Exterior building features, including facades, illuminated roofs, architectural features, entrances, exits, loading docks, and illuminated canopies, and,
c. Exterior building grounds lighting that is provided through the building’s electrical service.
Lighting Control
Interior lighting systems in buildings larger than 500 m? (5,000 ft?) shall be equipped with an automatic control device. Within these buildings, all office areas less than 30 m2 (300 ft”) enclosed by walls or ceiling-height partitions, all meeting and conference rooms, all school classrooms, and all storage spaces shall be equipped with occupancy sensors. For other spaces, this automatic control device shall function on either
a) Ascheduled basis at specific programmed times. An independent program schedule shall be provided for areas of no more than 2,500 m? (25,000 ft?) and not more than one floor; or,
b) Occupancy sensors that shall turn the lighting off within 30 minutes of an occupant leaving the space. Light fixtures controlled by occupancy sensors shall have a wall mounted, manual switch capable of turning off lights when the space is occupied.
Lighting for all exterior applications shall be controlled by a photo sensor or astronomical time switch
that is capable of automatically turning off the exterior lighting when daylight is available or the lighting is not required.
Lighting Power Density (LPD)
The interior lighting power required for different activities are per ECBC guidelines are discussed. Lighting power density is an indicator of Power in watts per Sq meter. The lighting Power Density is
derived by two methods namely:
¢ Building area method
¢ Space function method.
The installed interior lighting power calculated shall include all power used by the luminaries, including lamps, ballasts, current regulators, and control devices.
Building Area Method
Determination of interior lighting power allowance (watts) by the building area method (type of building) shall be in accordance with the LPD values given in code. The interior lighting power allowance is the sum of the products of the gross lighted floor area of each building area times the allowed lighting power density for that building area types.
Example: A hotel has four floors each of 1000 m? area. If the LPD is 10.8 W/m’, find out the interior
lighting power allowance.
= (1000 x 10.8)x 4
= 43200 W
Space Function Method
Determination of interior lighting power allowance (watts) by the space function method (type of operation) shall be in accordance with the LPD values provided in the code. The interior lighting power allowance is the sum of the lighting power allowances for all spaces. The lighting power allowance for a space is the product of the gross lighted floor area of the space times the allowed lighting power density for that space.
Example: An enclosed office has 400 m’ area. If the LPD is 11.8 W/m’, find out the interior lighting
power allowance.
= 400 X 11.8
= 4720 W
Exit Signs
Internally-illuminated exit signs shall not exceed 5 W per face.
Exterior Building Grounds Lighting
Lighting for exterior building grounds luminaires which operate at greater than 100 W shall contain lamps having a minimum efficacy of 60 lm/W unless the luminaire is controlled by a motion sensor. For building exterior lighting applications specified in ECBC [Table 7.4], the connected lighting power
shall not exceed the specified lighting power limits specified for each of these applications.
ECBC Guidelines on Electrical Power
ECBC has only mandatory requirements for electric power systems installed in buildings. These provisions are related to distribution transformers, electric motors, power factor, and distribution losses. The mandatory requirements of ECBC cover the following electrical equipment and systems of building:
¢ Transformers
¢ Energy- Efficient Motors
¢ Power Factor Correction
e Electrical Metering and Monitoring
¢ Power Distribution Systems
Power transformers of the proper ratings and design must be selected to satisfy the minimum acceptable efficiency at 50% and full load rating. In addition, the transformer must be selected such that it minimizes the total of its initial cost in addition to the present value of the cost of its total lost energy while serving its estimated loads during its respective life span.
All permanently wired polyphase motors of 0.375 kW or more serving the building and expected to operate more than 1,500 hours per year and all permanently wired polyphase motors of 50kW or more serving the building and expected to operate more than 500 hours per year shall have a minimum acceptable nominal full load motor efficiency not less than IS 12615 for energy efficient motors. Motor
horsepower ratings shall not exceed 200% of the calculated maximum load being served. All electricity supplies exceeding 10A, 3 phase shall maintain their power factor between 0.95 lag and unity at the point of connection.
Services exceeding 1000 kVA shall have permanently installed electrical metering to record demand (kVA), energy (kWh), and total power factor. The metering shall also display current (in each phase and the neutral), voltage (between phases and between each phase and neutral), and total harmonic distortion (THD) as a percentage of total current.
Services not exceeding 1000 kVA but over 65 kVA shall have permanently installed electric metering to record demand (kW), energy (kWh), and total power factor (or kVARh).
Services not exceeding 65 kVA shall have permanently installed electrical metering to record energy (kWh). The power cabling shall be adequately sized as to maintain the distribution losses not to exceed 1% of the total power usage.
Building Water Pumping Systems
The pumps used in the buildings are for chilled water circulation, cooling water circulation, domestic water, hot water and sewage water. The water requirement for cooling, drinking and general purpose requirements in buildings are meat by the local authorities and also from the independent bore wells. The water received is stored and pumped to the overhead tanks provided on the building terrace are hydro pneumatic system is used. Normally the pumps used in the building are of centrifugal type with efficiencies of 60%. The following energy conservation measures are adopted to reduce energy consumption in water pumping in buildings:
¢ Installation of high efficiency pumps
¢ Operation of pumps in parallel
¢ Auto pump operation with low level/high level flow control systems.
¢ Installation of variable frequency drive for chiller water and cooling water pumps
Uninterruptible power supply
An Uninterruptible Power Supply (UPS) is device that has an alternate source of energy, typically a battery backup that can provide power when the primary power source is temporarily disabled. The
switchover time must be small enough to not cause a disruption in the operation of the loads (Figure 10.6).
The components of a UPS are converter (AC to DC), battery, inverter (DC to AC), monitor and control hardware / software.
There are two type of UPS architecture namely line interactive (OFF line) and ON line. Simple OFF Line UPS systems, connect the load directly to the input AC line. Line Interactive systems have also the ability to correct UPS output if AC input voltage deviates beyond preset limits by means of an auto- transformer based Automatic Voltage Regulator. In case of significant utility voltage deeps or outages these systems transfer the UPS to battery operation.
Due to its direct connection to input AC power, OFF Line types, including Line Interactive systems
offer higher efficiency when compared to an Online UPS. But, unstable grid environment, with frequent power interruptions or outages, might cause these systems to suffer from frequent transfers to battery operation. Thus, exposing the critical load to possible failures due to unsmooth or unsuccessful transfer, or to battery failure, because of numerous battery discharges, which decrease drastically battery life time.
An Online UPS system, frequently called Double conversion system, first converts the AC input voltage to stabilized DC, which is then converted back to AC, to feed continuously the critical load, with pure stabilized sinusoidal output, coming either from the input line via AC/DC converter, or from batteries in case of power failure.
Energy efficiency of a UPS is the difference between the amount of energy that goes into UPS versus the amount of useful energy that comes out of the UPS and actually powers loads (Figure 10.7). In all UPS systems, some energy is lost as heat when it passes through the internal components of the UPS (including transformers, rectifiers, and inverters).
Almost all UPS power 100% nonlinear loads +viz., computers, servers and electronic equipment,
though the manufacturers test their UPS often using linear loads. UPS efficiency is often much higher
when powering linear loads.
The second major factor to influence UPS efficiency is the power level at which the efficiency is measured. Most UPSs typically have their best efficiency operating at 50% to 100% load level. But in the real situation, most UPS systems operate at 25% to 60% of their nominal load- not fully loaded. To determine accurate efficiency, the UPS should demonstrate efficiency at loads between 25-50%, where most UPS will likely to be operating.
Escalators and Elevators
The requirement of the maximum allowable electric power indicates ultimately the energy performance of the equipment. The power for lift equipment is to be measured when the lift is carrying its rated load and moving upward at its contract speed. For escalators and passenger conveyors, since the rated load is usually defined as number of person (not in kg weight), there is no theoretical rated load in kg for the equipment. Thus the electric power is to be measured when the escalator/conveyor is carrying no load and moving at its rated speed either in the upward or downward direction.
In escalators and elevators, the dominating factors that determine the energy consumption are the efficiency of the motor, friction, the controller and the driving gear box. The proportion of frictional loss of the machine can also become significant in the power consumption in no load condition, as it is the fixed overhead to keep the equipment running.
Factors That Affect Energy Consumption in Elevators and Escalator System
Energy is consumed by lift and escalator equipment mainly on the following categories:
1. Friction losses incurred while travelling.
2.Dynamic losses while starting and stopping.
3. Lifting (or lowering) work done, potential energy transfer.
4.Regeneration into the supply system.
The general approach to energy efficiency in lift and escalator equipment is merely to minimize the friction losses and the dynamic losses of the system. There are many factors that will affect these losses for elevator and escalator system:-
(A) Characteristic of the equipment
The type of motor, drive and control system of the machine, the internal decoration, means to reduce
friction in moving parts (e.g. guide shoes), type, speed and the pulley system of the equipment.
(B) Characteristic of the premises
The population distribution, the type of the premises, the height of the premises and the house keeping
of the premises,
(C) The configuration of the lif/escalator system
The zoning of the lift system, the combination of lift and escalator equipment, the strategies for vertical transportation and the required grade of service of the system.
General Principles to Achieve Energy Efficiency
In general the principles for achieving energy efficiency for lift/escalator installations are as follows:
1.Specify energy efficiency equipment for the system.
2.Do not over design the system.
3.Suitable zoning arrangement.
4.Suitable control and energy management of lift equipment
5.Use light weight materials for lift car decoration.
6.Good house keeping.
Building Energy Management System (BEMS)
Energy management systems can vary considerably in complexity and degree of sophistication. The simplest timing mechanism to switch systems ON and OFF at pre-determined intervals on a routine basis could be considered as an energy management system. These progresses to include additional features such as programmers, thermostatic controls, motorised valves, zoning, and optimum start controllers and compensated circuits.
The most complex of energy management systems have a computerised central controller linked to numerous sensors and information sources. These could include the basic internal and external range Shown schematically in Figure 10.8, along with further processed data to include: the time, the day of the week, time of year, percentage occupancy of a building, meteorological data, system state feedback factors for plant efficiency at any one time and energy gain data from the sun, lighting, machinery and
people.
microprocessor is then the main feature of the control system. Data on temperature, flow rates,pressures, etc., as appropriate, are collected from sensors in the system and the treated spaces and stored in the memory of the processor. Provided that
equations defining the performance of the
control elements, the items of plant and the behavioural characteristics of the systems controlled have
been developed and fed into the micro-processor as algorithms, deviations from the desired performance
can be dealt with by calculation, the plant output being varied accordingly. Mathematical functions replace control modes. For example, if room temperature rose in a space conditioned by a constant volume reheat system, the correct position of the valve in the low temperature hot water line feeding the heater battery could be calculated and corrected as necessary, to bring the room temperature back to the set point as rapidly as possible, without any offset. Data can be stored to establish trends and anticipation can be built into the program so that excessive swings in controlled conditions may be prevented. Furthermore, self-correction can be incorporated so that the control system learns from experience and the best possible system performance is obtained. This implies that commissioning inadequacies and possibly even design faults can be corrected but only to a certain extent. Optimum results are only obtainable, and the cost of the installation justified, from systems that have been properly designed, installed and commissioned. Under such circumstances it is then feasible to extend the scope of microprocessor control to include the management of all the building services with an economic use of its thermal and electrical energy needs.
The functions ofa building management system (BMS) or building energy management system (BEMS) are monitoring and control of the services and functions of a building, in a way that is economical and efficient in the use of energy. Furthermore, it may be arranged that one system can control a group of buildings.
Star Rating of Buildings
Star rating programme for buildings is based on the actual performance of a building in terms of its specific energy usage in kwh/sqm/year. The programme rates office buildings on a 1-5 Star scale, with 5 Star labeled buildings being the most efficient. The label provided under it is applicable for a period of 5 years from the date of issue. The Star rating Programme provides public recognition to energy efficient buildings. Different categories of buildings such as office buildings (day use and BPOs), Shopping Malls, Hotels, Hospitals and IT parks in the five climatic zones have been labeled under the
scheme.
The rating normalizes for operational characteristics that define the building use, hours of operation, climatic zone and conditioned space. To provide a useful benchmark the rating provides a comparison to the building’s peer group representing those buildings that have the same primary business function, and operating characteristics. The rating is based on an analysis of national data that accurately reflects
the distribution of energy use for each building type.
The national energy performance rating is a type of external benchmark that helps energy managers to assess how efficiently their buildings use energy, relative to similar buildings nationwide. Additionally, building owners and managers can use the performance ratings to help identify buildings that offer the best opportunity for improvement and recognition.
The objective of the Star rating is to create a market pull for efficient buildings. Improved energy efficiency is a primary goal which could be achieved through promotion of higher performance in buildings. Building rating and verification systems are an effective measure to encourage building owners to go beyond the minimum and creating an awareness of these systems would add substantial momentum to promote energy efficiency.
Energy performance Index: (EPI)
Energy Performance Index (EPI) in kWh / sq m/ year will be considered for rating the building. Bandwidths for Energy Performance Index for different climatic zones have been developed based on percentage air-conditioned space. For example a building in a composite climatic zone like New Delhi and having air conditioned area greater than 50% of their built up area, the bandwidths of EPI range between 190-90 kWh/sq m/year. Thus a building would get a 5-Star rating if its EPI falls below 90 kWh/sg m/year and | Star if it is between 165-190 kWh/sq m/year.
In addition to the star rating of the existing office buildings a Specific Star Rating programme has also been introduced for Business process outsourcing buildings such as call centers and allied services. The salient features of the BPO star rating programmes is highlighted below.
Average Annual hourly Energy Performance Index (EPI) i.e. (AAhEPI) in (Wh/sqm)/hr will be considered for rating the BPO building. AAhEPI shall be in terms of purchased and generated electricity divided by built up area in sqm and total annual hours of operation. However the total electricity would not include electricity generated from on-site renewable sources such as solar photovoltaic etc.
AAhEPI — AAhEPI (Wh/sqm)/hr is defined as Average Annual hourly EPI of a Building. This value is calculated from EPI values, mentioned in the table 10.12, as follows
[EPI/ (Daily hours of Operation X days of operation in a week X 52 weeks in a year)] X 1000. This value will be independent of time and therefore applicable to all types of BPO operations.
Built up Area — Built up area is the carpet area + area covered by thickness of walls + balconies etc. and would exclude basement and other areas used for parking. In case basement is being utilized for purpose other than parking, it should be included.
Energy Efficiency Measures in Buildings:
Air-Conditioning System:
Weather stripping of Windows and Doors
Minimise exfiltration of conditioned air and infiltration of external un-conditioned air through leaky
windows and doors by incorporating effective means of weather stripping. Self-closing doors should
also be provided where heavy traffic of people is anticipated.
Temperature and Humidity Setting
Ensure human comfort by setting the temperature to between 23°C and 25°C and the relative humidity
between 55% to 65%.
Chilled Water Leaving Temperature
Ensure higher chiller energy efficiency by maintaining the chilled water leaving temperature at or above 7° C. As a rule of thumb, the efficiency of a centrifugal chiller increases by about 2’4 % for every 1° C rise in the chilled water leaving temperature.
Chilled Water Pipes and Air Ducts
Ensure that the insulation for the chilled water pipes and ducting system is maintained in good condition. This helps to prevent heat gain from the surroundings.
Chiller Condenser Tubes
Ensure that mechanical cleaning of the tubes is carried out at least once every six months. Fouling in the condenser tubes in the form of slime and scales reduces the heat transfer of the condenser tubes and thereby reducing the energy efficiency of the chiller.
Cooling Towers
Ensure that the cooling towers are clean to allow for maximum heat transfer so that the temperature of the water returning to the condenser is less than or equal to the ambient temperature.
Air-handling Unit Fan Speed
Install devices such as frequency converters to vary the fan speed. This will reduce the energy consumption of the fan motor by as much as 15%.
Air Filter Condition
Maintain the filter in a clean condition. This will improve the heat transfer between air and chilled water and correspondingly reduce the energy consumption.
Lighting System:
All lighting systems generate heat that needs to be dissipated. By designing energy efficient lighting system that integrates day lighting and good controls, heat gains can be reduced significantly. This can
reduce the size of the HVAC system resulting in first-cost savings.
Day lighting
Day lighting benefits go beyond energy savings and power reduction. Daylight spaces have been shown to improve people’s ability to perform visual tasks, increase productivity and reduce illness. Building fenestration should be designed to optimize day lighting and reduce the need for electric lighting.
Orient the building to minimize building exposure to the east and west and maximize glazing on the south and north exposures.
Daylight strategies do not save energy unless electric lights are turned off or dimmed appropriately. ECBC requires controls in day lit areas that are capable of reducing the light output from luminaires by at least half.
¢ Install dimmers to take advantage of day lighting and where cost-effective.
¢ Replace rheostat dimmers with efficient electronic dimmers.
* Combine time switching with day lighting using astronomical time clocks.
¢ Control exterior lighting with photo controls where lighting can be turned off after a fixed interval.
Switch off Lights When Not in Use
Provision of Separate Switches for Peripheral Lighting
A flexible lighting system, which made use of natural lighting for the peripherals of the room, should be considered so that these peripheral lights can be switched off when not needed.
Install High Efficiency Lighting System
Replace incandescent and other inefficient lamps with lamps with higher lighting efficacy. For example, replacing incandescent bulbs with compact fluorescent lamps can reduce electricity consumption by 75% without any reduction in illumination levels.
Fluorescent Tube Ballasts
The ballast losses of conventional ballast and electronic ballast are 12W and 2W respectively. Hence, consider the use of electronic ballast for substantial energy savings in the lighting system.
Lamp Fixtures or Luminaries
Optical lamp luminaries made of aluminum, silver or multiple dielectric coatings have better light distribution characteristics. Use them to reduce electricity consumption by as much as 50% without compromising on illumination levels.
Integration of Lighting System with Air-Conditioning System
In open plan offices, the air-conditioning and lighting systems can be combined in such a way that the return air is extracted through the lighting luminaires. This measure ensures that lesser heat will be directed from the lights into the room.
Cleaning of Lights and Fixtures
Clean the lights and fixtures regularly. For best results, dust at least four times a year.
Use Light Colors for Walls, Floors and Ceilings
The higher surface reflectance values of light colors will help to make the most of any existing lighting
system. Consider light colored furniture and room partitions to optimize light reflectance. Avoid furniture colors and placement that will interfere with light distribution. Keep ceilings and walls as bright as possible.
Deal with each activity area and each fixture individually
Eliminate excessive lighting by reducing the total lamp wattage in each activity area
Task Lighting
Lighting layout should use task lighting principle. Install focusing lamps or flexible extensions wherever needed.
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