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Intelligent Buildings Technology

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Title: Intelligent Buildings Technology


1
Intelligent Buildings Technology
2
Intelligent Buildings Technology
  • 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.

3
Intelligent Buildings Technology
  • 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.

4
Intelligent Buildings Technology
  • 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.

5
Intelligent Buildings Technology
  • Energy in Buildings
  • A more climate sensitive approach linked to the
    use of advanced control systems allows the
    building occupants to control their indoor
    environment whilst maximising 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 that are the prerequisite
    for a well balanced, comfortable and healthy
    indoor environment.

6
Intelligent Buildings Technology
  • Energy in Buildings
  • The purpose of energy management in buildings,
    and hence the role of the building energy
    manager, is to identify the areas in building
    stock where energy is used in excess.
  • Energy consumption in building is required for
    the following uses
  • Heating
  • Cooling
  • Ventilation
  • Lighting
  • Equipment and machinery
  • Domestic hot water

7
Intelligent Buildings Technology
  • Indoor Comfort
  • Thermal comfort
  • Visual Comfort
  • Indoor air quality

8
Thermal Comfort
9
Intelligent Buildings Technology
  • Thermal Comfort
  • Comfort is defined as the sensation of complete
    physical and mental well being.
  • Thermal neutrality, where an individual desires
    neither a warmer nor a colder environment, is a
    necessary condition for thermal comfort.
  • The factors affecting comfort are divided into
    personal variables
  • activity
  • Clothing
  • and environmental variables,
  • (air temperature,
  • mean radiant temperature
  • air velocity
  • air humidity

10
Intelligent Buildings Technology
Thermal Comfort Energy Balance
11
Intelligent Buildings Technology
  • Thermal Comfort Personal Variables
  • Clothing describes the occupants thermal
    insulation against the environment. This thermal
    insulation is expressed in clo units.

12
Intelligent Buildings Technology
  • Thermal Comfort Personal Variables
  • Activity The metabolic rate is the amount of
    energy produced per unit of time by the
    conversion of food. It is influenced by activity
    level and is expressed in mets (1 met seated
    relaxing person).

13
Intelligent Buildings Technology
  • Thermal Comfort Environmental Variables
  • Temperature
  • The average air temperature from the floor at a
    height of 1.1 m.
  • Mean Radiant TemperatureThe average temperature
    of the surrounding surfaces, which includes the
    effect of the incident solar radiation.
  • Air VelocityWhich affects convective heat loss
    from the body, i.e. air at a greater velocity
    will seem cooler.
  • Air HumidityWhich affects the latent heat losses
    and has a particularly important impact in warm
    and humid environments

14
Intelligent Buildings Technology
  • Thermal Comfort Indices
  • Although the four parameters of air temperature,
    radiant temperature, relative humidity and air
    movement are generally recognized as the main
    thermal comfort parameters, indoor environmental
    conditions in terms of thermal comfort can
    generally be assessed through three classes of
    environmental indices, namely
  • Direct indices
  • Rationally derived indices
  • Empirical indices

15
Intelligent Buildings Technology
  • Thermal Comfort Indices
  • Direct indices
  • dry-bulb temperature
  • dew-point temperature
  • wet-bulb temperature
  • relative humidity
  • air movement
  • Rationally derived indices
  • mean radiant temperature
  • operative temperature
  • heat stress, and
  • thermal stress
  • Empirical indices

16
Intelligent Buildings Technology
  • Thermal Comfort PMV Index
  • The perceived need for both heating and cooling
    is to achieve accepted standards of thermal
    comfort, usually defined (directly or indirectly)
    by temperature limits.
  • Controversy exists as to what these standards of
    thermal comfort are. It has been observed that
    there has been an apparent discrepancy between
    comfort predictions using models derived from
    laboratory experiments, such as those by Fanger
    (1970), and subjective assessments of comfort
    found in field studies. It has been found in a
    compilation of results from field studies in
    predominantly in warm and hot climates by
    Humphreys (1978) that the preferred comfort
    temperature in buildings was a function of the
    average monthly outdoor temperature (To is the
    mean monthly temperature)

17
Intelligent Buildings Technology
  • Thermal Comfort PMV Index
  • The Predicted Mean Vote (PMV) is a widely
    accepted mathematical expression of thermal
    comfort. This index is a real number and comfort
    is obtained if it lies within the specific limits
    of the comfort range. Since 1984, the index
    which is calculated through a complex
    mathematical function of human activity, clothing
    and environmental parameters has been the basis
    of the international standard ISO-7730.
  • This PMV is an index which predicts the mean
    value of the votes of a large group of people,
    and is directly related to the percentage of
    people dissatisfied (PPD), on the following seven
    point thermal sensation scale 3 Hot, 2 Warm,
    1 Slightly Warm, 0 Neutral, - 1 Slightly Cool,
    - 2 Cool, - 3 Cold.

18
Intelligent Buildings Technology
Thermal Comfort PMV Index
19
Intelligent Buildings Technology
  • Thermal Comfort PMV Index
  • The result of using Fangers equations seems to
    predict the need for much more closely controlled
    conditions than are usually found in free running
    buildings, in which people still seem to be
    comfortable. Some of the possible explanations
    for the apparent discrepancy between the
    prediction of the Fanger model and the findings
    of the Humphreys survey, are
  • The thermal comfort parameters, air temperature,
    radiant temperature and air movement vary
    spatially in a room, and the actual values
    experienced by an occupant may not be those
    described by a "room-average value".
  • Thermal comfort parameters vary with time whereas
    the Fanger model predicts a response for steady
    conditions.
  • The description of clothing level assumed in the
    use of the Fanger equation may not be the same as
    is actually worn in the real situation.
  • The insulation value of the clothing may not be
    as predicted from the description of the clothing
    ensemble.
  • The metabolic rate as assumed from the
    description of the activity may not be the same
    as the actual metabolic rate.

20
Visual comfort
21
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.
  • Peoples 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.

22
Intelligent Buildings Technology
  • Visual Comfort Illuminance levels

23
Intelligent Buildings Technology
  • Visual Comfort
  • 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.

24
Intelligent Buildings Technology
  • Visual Comfort
  • The luminous environment should be comfortable,
    which means that sources of glare should be
    avoided.
  • Oversized glazed windows with clear glazing are
    sources of glare, and this can be fought in using
    multiple apertures, if possible on different
    walls.
  • Glossy materials and inappropriate shading
    devices might bring excessive amount of light in
    the field of vision.
  • Also, psychological aspects such as the quality
    of the vision to the outside, the beauty of the
    design and the attractiveness of the space are
    very important.

25
Intelligent Buildings Technology
  • Visual Comfort
  • Natural light comes from three directions
  • Direct Sunlight
  • Diffuse light from the sky, and
  • Light Reflections from the Environment

26
Intelligent Buildings Technology
  • Visual Comfort
  • The daylight factor is a measure of the daylight
    level at any position indoors as a percentage of
    the illuminance 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

27
Intelligent Buildings Technology
Visual Comfort Indoor lighting distribution
28
Intelligent Buildings Technology
  • Visual Comfort
  • 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.

29
Indoor air quality
30
Intelligent Buildings Technology
  • Indoor air Quality
  • 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
    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).

31
Intelligent Buildings Technology
  • Indoor air Quality Indoor pollutants
  • 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.

32
Intelligent Buildings Technology
  • 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.

33
Intelligent Buildings Technology
Climate
34
Intelligent Buildings Technology
  • 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.

35
Intelligent Buildings Technology
  • 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.

36
Intelligent Buildings Technology
  • Climate
  • 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.

37
Intelligent Buildings Technology
  • 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

38
Intelligent Buildings Technology
  • Building Climate interaction

39
Intelligent Buildings Technology
  • 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.

40
Intelligent Buildings Technology
  • Heat transfer
  • Conduction - C
  • Radiation - R
  • Convection - C

41
Intelligent Buildings Technology
  • Heat transfer Conduction
  • Conductive heat transfer is a process by which
    thermal energy is transmitted by direct molecular
    communication.
  • It is the only mechanism by which heat flows in
    an opaque solid. Conduction in a translucent
    solid is accompanied by radiation, whilst heat
    transfer through stagnant gases and liquids takes
    place by conduction with some radiation.
    Convection enhances the thermal equilibrium
    process in moving fluids. The thermal
    conductivity k of a substance determines its
    ability to conduct heat.
  • Conductive heat transfer with respect to
    buildings concerns the heat losses through the
    building envelope the walls, windows and doors.
  • Heat transfer is caused by a temperature
    difference across the envelope, always in the
    direction of the temperature gradient, with
    energy entering the one surface at a higher
    temperature and leaving the other surface at a
    lower temperature. Therefore, buildings are
    generally affected by envelope losses in the
    winter and envelope gains in the summer.

42
Intelligent Buildings Technology
  • Heat transfer Conduction

43
Intelligent Buildings Technology
  • Heat transfer Convection
  • Convection is a process of heat transfer by the
    combined action of heat conduction, energy
    storage and mixing motion.
  • Convection is combined to fluids only and
    requires an external force -either forced or
    natural (buoyancy)- to be present.
  • The rate of heat transfer depends on the
    temperature difference between the fluid and the
    surface and the convective heat transfer
    coefficient h.
  • The convective heat transfer co-efficient is a
    function of
  • 1) the geometry of the system,
  • 2) the velocities and mode of fluid flow,
  • 3) the physical properties of the fluid and
  • 4) possibly on the temperature difference.
  • The convective heat transfer is therefore not
    constant or uniform over the whole surface,
    although for all intensive purposes in building
    physics it is often considered to be so.

44
Intelligent Buildings Technology
  • Heat transfer Convection

45
Intelligent Buildings Technology
  • Heat transfer-Radiation
  • All bodies emit radiation. Heat transfer via
    radiation occurs when a body converts part of its
    internal energy (a result of its temperature)
    into electromagnetic waves.
  • In buildings heat transfer due to radiation is
    most apparent with transparent elements, where a
    large amount of the impinging radiation coming
    from the sun is transmitted to the building
    material.
  • Radiative heat transfer can also contribute to
    the cooling of external surfaces through exposure
    to the night sky, wherin these surfaces emit net
    radiation towards the clear sky, or in the effect
    of discomfort associated with sitting next to hot
    or cold surfaces (i.e. cold windows).

46
Intelligent Buildings Technology
Heat transfer-Radiation
47
Intelligent Buildings Technology
  • Thermal storage
  • The ability of a material to store energy is
    characterised by its specific heat (cp, J/kgK).
    The specific heat of a material is defined as the
    amount of heat necessary to raise a unit mass of
    the material by one degree. The heat that is
    stored in the mass of the material, m, for a
    temperature change, ?T, is given by

48
Intelligent Buildings Technology
  • Energy Management Systems

49
Intelligent Buildings Technology
  • Intelligent Building-Definitions
  • EIBG (European Intelligent Building Group) One
    that incorporates the best available concepts,
    materials, systems and technologies integrating
    these to achieve a building which meets or
    exceeds the performance requirements of the
    building stakeholders, which include the owners,
    managers and users, as well as the local and
    global community.
  • Also from EIBG but more often quoted One that
    maximizes the efficiency of its occupants and
    allows effective management of resource with
    minimum life costs

50
Intelligent Buildings Technology
  • Intelligent Building-Definitions
  • IBI (The Intelligent Buildings Institute in
    Washington DC, US) one that provides a
    productive and cost-effective environment through
    optimization of its four basic components -
    structure, systems, services and management - and
    the interrelationships between them.

51
Intelligent Buildings Technology
  • Intelligent Building-Definitions
  • An Intelligent Building is one that
  • 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)

52
Intelligent Buildings Technology
  • Building Energy Management Systems-Definitions
  • Building Energy Management Systems aim to
    optimise the use of energy in buildings by
    maintaining at the same time the indoor
    environment under comfort conditions
  • Practically, a BEMS is a computerised system that
    attempts to control all or some of the energy
    consuming operations in a building
  • HVAC systems (Heating Ventilating and Air
    Conditioning)
  • Lighting systems (natural and artificial)
  • Indoor climate

53
Intelligent Buildings Technology
  • Building Energy Management Systems-Definitions
  • BEMS are now available with a wide range of
    building automation facilities and in many
    installations BEMS have replaced hardwired
    controls, with control strategies implemented in
    software
  • BEMS can combine many technologies
  • Passive heating and cooling
  • Efficient daylight penetration by using suitable
    shading devices
  • Efficient appliances that reduce the electricity
    consumption
  • High efficiency windows (e.g. electrochromic)
  • Natural ventilation for indoor air quality and
    passive cooling
  • Improvements in building services for HVAC
  • Building Energy Management and Control

54
Intelligent Buildings Technology
  • Building Energy Management Systems- How much
    energy can be saved

55
Building Energy Management Systems- Hardware
Intelligent Buildings Technology
  • The basic architecture consists of
  • Multiple programmable control panels, called
    Network Control Units (NCUs) each NCU manages an
    area of the building facility
  • Operator WorkStations (OWSs) that communicate
    with each other over a high speed communication
    network normally a standard PC
  • This communication network is called Local Area
    Network (LAN)
  • NCU capacity can be increased with remote panels
    called Network Expansion Units (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 Application Specific Controllers (ASCs)

56
BEM Systems Software 1
Intelligent Buildings Technology
  • Direct Digital Control (DDC) is the major concept
    of Building Automation System (BAS) in nowadays
  • DDC control e.g. loops for damper operation are
    available to provide ventilation requirements or
    to utilize outdoor air for cooling
  • Building energy management features are available
    inside a modem BAS
  • e.g. the duty cycle program reduces electrical
    energy consumed by the fan by cycling it on and
    off
  • The unoccupied period program, e.g night cycle
    program, is a function that can reduce the indoor
    temperature of a space by applying night
    ventilation

57
BEM Systems Software 2
Intelligent Buildings Technology
  • 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

58
BEM Systems Architecture 1
Intelligent Buildings Technology
  • General Architecture

59
BEM Systems Architecture 2
Intelligent Buildings Technology
  • General Architecture

60
Intelligent Buildings Technology
  • BEM Systems Architecture 3
  • 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".
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