Energy used in buildings accounts for almost half of the total amount of energy consumed in the Pakistan today.
Almost 85% of the energy used in buildings is for low temperature applications such as space and water heating.
Appropriate building designs involving clean and efficient technologies are already available and there use may help to reduce future energy consumption as well as to provide a better quality of life for citizens.
With fossil fuels the primary energy source, the building sector currently produces 22% of total CO 2 emissions in the EC and unknown figure regarding Pakistan. This is more than that produced by the industrial sector in Europe.
Intelligently designed buildings are those that involve environmentally responsive design taking into account the surroundings and building usage and involving the selection of appropriate building services and control systems to further enhance building operation with a view to the reduction of energy consumption and environmental impact over its lifetime.
Buildings are inherently linked to their usage and surroundings and hence their indoor environment is the result of a range of interactions affected by seasonal and daily changes in climate and by the requirements of occupants varying in time and space.
The design of buildings in the mid-late twentieth century has sought to eliminate the effect of outdoor daily and seasonal changes through the use of extensive heating, cooling, lighting and ventilation equipment, resulting in spiraling energy consumption and environmental impact.
A more climate sensitive approach linked to the use of advanced control systems allows the building occupants to control their indoor environment whilst maximizing the contribution of ambient energy sources to the creation of a comfortable indoor environment through the use of a more climate sensitive design approach.
Under almost all circumstances it is necessary at some point in time to provide some form of auxiliary heating, cooling, lighting or ventilation since natural sources cannot always cover the requirements for thermal comfort visual comfort and IAQ (Indoor Air Quality) that are the prerequisite for a well balanced, comfortable and healthy indoor environment.
Visual comfort is the main determinant of lighting requirements.
Good lighting provide a suitable intensity and direction of illumination on the task area, appropriate colour rendering, the absence of discomfort and, in addition, a satisfying variety in lighting quality and intensity from place to place and over time.
People’s lighting preferences vary with age, gender, time and season. The activity to be performed is critically important.
Various agencies (ASHRAE, CIBSE, etc.) and text books list optimal illuminances for different activities. These are generally based on uniform and constant levels of artificial light falling on the working plane.
Natural light is a fluctuating source of light. It depends on the hour of the day, the season, the climate and the latitude of the location.
The objective of a daylight technique consists of providing the best possible indoor luminous environment as often as possible.
A luminous environment should be appropriate to the function of the room: there should be enough light for reading, writing, or filing documents.
Illuminance of 300 to 400 lux on a desk are often considered as minimum required levels for most of office tasks. Hallways might require lower levels, 100 lux, and commercial centres higher levels, 700 lux. These requirements are defined by CIE.
Performance does not depend only on these illuminance levels. The location of the source of light with respect to the direction of observation may require higher illuminance, for instant when the observer faces a window.
The daylight factor is a measure of the daylight level at any position indoors as a percentage of the luminance levels outdoors. The daylight factor at any point on a working plane is calculated in terms of light coming directly from the sky (the sky component), light reflected from outdoor surfaces (the externally reflected component) and light reflected form surfaces within the room (the internally reflected component). The average daylight factor in a space can be calculated from:
If a predominately daylit appearance is required, then the daylight factor should be 5% or more if there is to be no supplementary artificial lighting, or 2% if supplementary lighting is provided.
Discomfort is caused when the eye has to cope with, simultaneously, great differences in light levels, the phenomenon we know as glare. Maximum recommended values for the ratio between different parts of a visual field, the luminance ratio, as shown in the following table.
A conflict has always existed between adequate ventilation and energy costs has long existed.
During the last three decades, decreased ventilation rates for energy conservation, along with increased use of synthetic (i.e. man-made) materials in buildings have resulted in increased health complaints from building occupants. However, energy efficiency and good indoor air quality in buildings need not be mutually exclusive.
Good indoor air quality is a function of a number of parameters including: the initial design and continuous maintenance of HVAC systems; use of low toxic emittance building materials; and consideration of all sources of indoor air pollution such as occupant activities, operation of equipment and use of cleaning products.
In fact, in 1986 the WHO (World Health Organization) reported that "energy-efficient but sick buildings often cost society far more than it gains by energy savings".
The result of the reductions in ventilation rates in buildings have led to the so called "Sick Building Syndrome" (SBS) and "Building Related Illness" (BRI).
Every building has a number of potential sources of indoor air contaminants.
Some sources, such as building materials and furnishings, release contaminants more or less continuously. Other sources are related to occupant activities and therefore release contaminants intermittently.
Such activities include cooking, smoking, use of solvents, pesticides, paint, and cleaning products, and operation of office machines and equipment.
High concentrations of pollutants can remain in the indoor air for long periods after they are emitted. Although some sources may be common in all building types, office and commercial buildings vary greatly from residential buildings in terms of design, air handling systems and occupant activities and therefore certain indoor air pollutant sources may be more prevalent in some types of buildings.
There are two types of ventilation: natural and mechanical.
Natural ventilation includes the movement of outdoor air through intentional openings such as doors and windows and through unintentional openings in the building shell scuch as cracks which result in infiltration and exfiltration.
Mechanical or forced ventilation is intentional ventilation supplied by fans or blowers. These fans are usually part of the buildings HVAC system which heats, cools, mixes and filters the air being supplied to the building.
The outdoor air temperature has a significant effect on building thermal losses due to conduction through the walls and roof of the building, as well as affecting ventilation and infiltration losses due to either desirable or undesirable air changes.
In warm climates the relative humidity plays an important role in determining thermal comfort levels, since during warm weather the high pressure of water vapour prevents the evaporation of perspiration from the body thereby inhibiting the body from being maintained at a comfortable temperature .
Prevailing wind speed and direction affect significantly the building thermal losses during the heating season, increasing both convection at exposed surfaces and hence encouraging envelope losses and also by increasing the air change rate due to natural ventilation and infiltration. During the cooling season, the knowledge of both the direction and wind speed permits the design of the building to facilitate passive cooling.
The sun-path and the cloud cover determine the amount of solar radiation impinging on differently inclined surfaces and since the sun-path changes from season to season, so does the amount of direct solar radiation impinging on these different surfaces.
Intelligent Buildings Technology
Building – Climate interaction Intelligent Buildings Technology
The building envelope responds dynamically to the impact of the outdoor climate on the envelope exterior and the effect of the occupancy pattern and building usage on the interior.
However, the performance of the heating, ventilation and air-conditioning systems, artificial lighting, fenestration opening and shading can be harmonized and optimized in response to occupancy needs and climatic conditions through a building energy management system which allows direct control of the necessary actuators either manually or automatically.
In this manner the individual components of the building can be controlled to produce the best possible indoor environment with minimum energy consumption.
Heat Conduction Heat transfer through a material, from one molecule to the next is called conduction. The heat entering this metal rod is flowing to the ends.
Convection When we move heat by circulating a medium like air or water, we call the process: convection. The coolant circulating in the cooling system transfers heat from the engine to the radiator and the warm or cool air circulating through the vehicle are both examples of convection.
Radiation The heat transfer from the Sun to the Earth is an example of radiation. Heat is transferred, but it does not warm the medium (space) through which it passes. Radiant heat will warm the interior and exterior of a vehicle that is parked in the sun.
Provides a productive and cost-effective built environment through optimization of its four basic components - structure, systems, services and management - and the interrelationships between them. (focused on the benefit of the Owners)Creating Desired indoor environment)
So as to maximize the efficiency of its occupants (focused on the benefit of the Users) (Influence of creating desired indoor environment on occupants)
And to allow effective management of resource with minimum life costs (focused on the benefit of the Managers) (Environmental and economic impact of creating desired indoor environment)
B uilding E nergy M anagement S ystems- How much energy can be saved
Intelligent Buildings Technology
B uilding E nergy M anagement S ystems- Hardware
The basic architecture consists of :
Multiple programmable control panels, called N etwork C ontrol U nits (NCUs) [each NCU manages an area of the building facility]
O perator W ork S tations (OWSs) that communicate with each other over a high speed communication network [normally a standard PC]
This communication network is called L ocal A rea N etwork (LAN)
NCU capacity can be increased with remote panels called N etwork E xpansion U nits (NEUs)
The NCUs and NEUs directly control central plant equipment, while the management of smaller air handlers, heat pumps, lighting circuits and other building services systems is delegated to a family of A pplication S pecific C ontrollers (ASCs)
The enthalpy program monitors the temperature and relative humidity or dew-point of the outdoor and return air and then positions the outdoor air and return air dampers to use the air source with the lowest total heat or least enthalpy
The load reset program controls heating and/or cooling to maintain comfort conditions in the building while consuming a minimum amount of energy
The zero- energy band program saves energy by avoiding simultaneous heating and cooling of air delivered to spaces
The occupied-unoccupied lighting control is a time-based program that schedules the on/off time of lights for a building or zone to coincide with the occupancy schedules
The structures of BEMS change with evolution of technologies and products.
Early BEMS were centralized energy management systems and first appeared in the 1970s, having been developed in the USA. The central station was based on a minicomputer, which contained the only computing power or "intelligence" in the system, with "dumb" or unintelligent outstations which were boxes or cabinets for relays and connections to sensors and actuators.
Since about 1980, with the rapid development of technologies, the outstations became as powerful as the previous minicomputer, if not more so.
Also, the outstations have gained considerably in processing power giving them "intelligence".