19-04-2011, 02:49 PM
Presented by:
SASIDHAR KUMAR REDDY
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INTELLIGENT BUILDINGS
Energy in Buildings
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.
Introduction-Energy Management
Energy used in buildings accounts for almost half of the total amount of energy consumed in the European Community 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.
Introduction-Energy Management
With fossil fuels the primary energy source, the building sector currently produces 22% of total CO2 emissions in the EC. This is more than that produced by the industrial sector.
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.
Intelligent Buildings Technology
Visual Comfort
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.
Visual Comfort – Illuminance levels
Indoor air Quality
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.
In fact, in 1986 the WHO (World Health Organisation) 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).
Indoor air Quality – Ventilation
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.
Climate
Climate responsive design in buildings takes into account the following climatic parameters which have direct influence on indoor thermal comfort and energy consumption in buildings:
The air temperature,
The humidity,
The prevailing wind direction and speed,
The amount of solar radiation and the solar path.
Long wave radiation between other buildings and the surrounding environment and sky also plays a major role in building performance.
Climate
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.
Macroclimate is a term referring to the general climatic character of a region in terms of temperature, humidity, precipitation, wind, sunshine and cloud cover. An appreciation of the overall characterisation of the climate of a region is a fundamental requirement for climate responsive building design, this affecting the general design principles which should be followed.
Regional climatic factors are strongly affected by the local topography, vegetation and the nature of the area, resulting in deviations from the regional macroclimate. The effect of such factors results in climatic characteristics known as the mesoclimate. Heavily vegetated or densely built-up areas have a significant impact on the climate of a specific location.
The conditions of the climatic parameters of a specific site or around a building are termed the microclimate. Temperature, humidity, wind speed, and solar radiation around a building can be affected by the deliberate placement of vegetation, landscaping, water and fountains, and positioning of constructions
Intelligent Buildings Technology
Building – Climate interaction
Building Envelope
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 transfer
Conduction - C
Radiation - R
Convection - C
