123451109 Intelligent Building Technology

7/27/2019 123451109 Intelligent Building Technology

1/60


2/60


3/60

Introduction-Energy Management With fossil fuels the primary energy source, the building

sector currently produces 22% of total CO2 emissions inthe EC. This is more than that produced by theindustrial sector.

Intelligently designed buildings are those that involveenvironmentally responsive design taking into accountthe surroundings and building usage and involving theselection of appropriate building services and controlsystems to further enhance building operation with a

view to the reduction of energy consumption andenvironmental impact over its lifetime.

Intelligent Buildings Technology


4/60

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 inspiraling energy consumption and environmental impact.



5/60

Energy in Buildings A more climate sensitive approach linked to the use of

advanced control systems allows the building occupants tocontrol their indoor environment whilst maximising thecontribution of ambient energy sources to the creation of acomfortable 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 alwayscover the requirements for thermal comfort, visual comfortand IAQ that are the prerequisite for a well balanced,

comfortable and healthy indoor environment.



6/60

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 thefollowing uses:

Heating

Cooling

Ventilation Lighting

Equipment and machinery

Domestic hot water



7/60

Indoor Comfort

Thermal comfort Visual Comfort

Indoor air quality

Intelligent Buildings

Technology


8/60

Thermal Comfort


9/60


10/60

Thermal Comfort Energy Balance



11/60

Thermal Comfort Personal Variables Clothing: describes the occupants thermal insulation against

the environment. This thermal insulation is expressed in clounits.



12/60

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 byactivity level and is expressed in mets (1 met = seatedrelaxing person).



13/60

Thermal Comfort Environmental Variables Temperature

The average air temperature from the floor at a height

of 1.1 m.

Mean Radiant Temperature

The average temperature of the surrounding surfaces,

which includes the effect of the incident solar radiation.

Air Velocity

Which affects convective heat loss from the body, i.e.

air at a greater velocity will seem cooler. Air Humidity

Which affects the latent heat losses and has a

particularly important impact in warm and humid

environments



14/60

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 threeclasses of environmental indices, namely:

Direct indices

Rationally derived indices

Empirical indices



15/60

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



16/60

Thermal Comfort PMV Index The perceived need for both heating and cooling is to

achieve accepted standards of thermal comfort, usuallydefined (directly or indirectly) by temperature limits.

Controversy exists as to what these standards of thermalcomfort are. It has been observed that there has been an

apparent discrepancy between comfort predictions usingmodels derived from laboratory experiments, such asthose by Fanger (1970), and subjective assessments ofcomfort found in field studies. It has been found in acompilation of results from field studies in predominantlyin warm and hot climates by Humphreys (1978) that the

preferred comfort temperature in buildings was a functionof the average monthly outdoor temperature (To is themean monthly temperature):



17/60

Thermal Comfort PMV Index The Predicted Mean Vote (PMV) is a widely accepted

mathematical expression of thermal comfort. This index isa real number and comfort is obtained if it lies within thespecific limits of the comfort range. Since 1984, the index which is calculated through a complex mathematical

function of human activity, clothing and environmentalparameters has been the basis of the internationalstandard ISO-7730.

This PMV is an index which predicts the mean value ofthe votes of a large group of people, and is directly relatedto the percentage of people dissatisfied (PPD), on thefollowing seven point thermal sensation scale: + 3 Hot, + 2Warm, + 1 Slightly Warm, 0 Neutral, - 1 Slightly Cool, - 2Cool, - 3 Cold.



18/60

Thermal Comfort PMV Index



19/60

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 freerunning buildings, in which people still seem to be comfortable. Someof the possible explanations for the apparent discrepancy between theprediction of the Fanger model and the findings of the Humphreyssurvey, are:

The thermal comfort parameters, air temperature, radiant temperatureand air movement vary spatially in a room, and the actual valuesexperienced by an occupant may not be those described by a "room-average value".

Thermal comfort parameters vary with time whereas the Fanger modelpredicts a response for steady conditions.

The description of clothing level assumed in the use of the Fangerequation 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 thedescription of the clothing ensemble.

The metabolic rate as assumed from the description of the activitymay not be the same as the actual metabolic rate.



20/60


21/60

Visual Comfort Visual comfort is the main determinant of lighting

requirements.

Good lighting provide a suitable intensity and direction ofillumination on the task area, appropriate colour rendering,

the absence of discomfort and, in addition, a satisfyingvariety in lighting quality and intensity from place to placeand over time.

Peoples lighting preferences vary with age, gender, timeand season. The activity to be performed is criticallyimportant.

Various agencies (ASHRAE, CIBSE, etc.) and text bookslist optimal illuminances for different activities. These aregenerally based on uniform and constant levels of artificiallight falling on the working plane.



22/60

Visual Comfort Illuminance levels



23/60

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 bestpossible indoor luminous environment as often as possible.

A luminous environment should be appropriate to the function of theroom: there should be enough light for reading, writing, or filingdocuments.

Illuminance of 300 to 400 lux on a desk are often considered asminimum required levels for most of office tasks. Hallways mightrequire 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. Thelocation of the source of light with respect to the direction of

observation may require higher illuminance, for instant when theobserver faces a window.



24/60

Visual Comfort The luminous environment should be comfortable, which

means that sources of glare should be avoided.

Oversized glazed windows with clear glazing are sourcesof 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 thevision to the outside, the beauty of the design and theattractiveness of the space are very important.



25/60


26/60

Visual Comfort The daylight factor is a measure of the daylight level at any position

indoors as a percentage of the illuminance levels outdoors. Thedaylight factor at any point on a working plane is calculated interms of light coming directly from the sky (the sky component),light reflected from outdoor surfaces (the externally reflectedcomponent) and light reflected form surfaces within the room (theinternally reflected component). The average daylight factor in aspace can be calculated from:



27/60


28/60

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.



29/60

Indoor air quality


30/60

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 energyconservation, along with increased use of synthetic (i.e. man-made)materials in buildings have resulted in increased health complaints frombuilding occupants. However, energy efficiency and good indoor air qualityin 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 lowtoxic emittance building materials; and consideration of all sources of indoorair pollution such as occupant activities, operation of equipment and use ofcleaning 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 energysavings".

The result of the reductions in ventilation rates in buildings have led to theso called "Sick Building Syndrome" (SBS) and "Building Related Illness"(BRI).



31/60

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, releasecontaminants more or less continuously. Other sources are related tooccupant 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 longperiods after they are emitted. Although some sources may be common inall building types, office and commercial buildings vary greatly fromresidential buildings in terms of design, air handling systems and occupantactivities and therefore certain indoor air pollutant sources may be more

prevalent in some types of buildings.



32/60

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 ascracks 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.



33/60

Climate


Technology


34/60

Climate Climate responsive design in buildings takes into

account the following climatic parameters which havedirect influence on indoor thermal comfort and energyconsumption 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 rolein building performance.



35/60

Climate The outdoor air temperature has a significant effect

on building thermal losses due to conductionthrough the walls and roof of the building, as well as

affecting ventilation and infiltration losses due toeither desirable or undesirable air changes.

In warm climates the relative humidity plays animportant role in determining thermal comfort levels,since during warm weather the high pressure of

water vapour prevents the evaporation ofperspiration from the body thereby inhibiting thebody from being maintained at a comfortabletemperature.



36/60

Climate Prevailing wind speed and direction affect significantly

the building thermal losses during the heating season,increasing both convection at exposed surfaces andhence encouraging envelope losses and also by

increasing the air change rate due to natural ventilationand infiltration. During the cooling season, theknowledge of both the direction and wind speedpermits the design of the building to facilitate passivecooling.

The sun-path and the cloud cover determine theamount of solar radiation impinging on differentlyinclined surfaces and since the sun-path changes fromseason to season, so does the amount of direct solarradiation impinging on these different surfaces.



37/60


38/60

Building Climate interaction


Technology


39/60


40/60

Heat transfer

Conduction - C

Radiation - R

Convection - C



41/60

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, whilstheat transfer through stagnant gases and liquids takes place by

conduction with some radiation. Convection enhances the thermalequilibrium process in moving fluids. The thermal conductivity k of asubstance determines its ability to conduct heat.

Conductive heat transfer with respect to buildings concerns the heatlosses 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, withenergy entering the one surface at a higher temperature and leavingthe other surface at a lower temperature. Therefore, buildings aregenerally affected by envelope losses in the winter and envelopegains in the summer.



42/60

Heat transfer Conduction



43/60

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 differencebetween the fluid and the surface and the convective heat transfercoefficient 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 and4) possibly on the temperature difference.

The convective heat transfer is therefore not constant or uniform overthe whole surface, although for all intensive purposes in buildingphysics it is often considered to be so.



44/60

Heat transfer Convection



45/60

Heat transfer-Radiation All bodies emit radiation. Heat transfer via radiation occurs

when a body converts part of its internal energy (a result ofits temperature) into electromagnetic waves.

In buildings heat transfer due to radiation is most apparent

with transparent elements, where a large amount of theimpinging radiation coming from the sun is transmitted tothe building material.

Radiative heat transfer can also contribute to the cooling ofexternal surfaces through exposure to the night sky, wherin

these surfaces emit net radiation towards the clear sky, or inthe effect of discomfort associated with sitting next to hot orcold surfaces (i.e. cold windows).



46/60


Heat transfer-Radiation


47/60

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, isgiven by:



48/60

Energy Management Systems


Technology


49/60

Intelligent Building-DefinitionsEIBG (European Intelligent Building Group):

One that incorporates the best availableconcepts, materials, systems and technologies

integrating these to achieve a building whichmeets or exceeds the performancerequirements of the building stakeholders, whichinclude the owners, managers and users, aswell as the local and global community.

Also from EIBG but more often quoted: One thatmaximizes the efficiency of its occupants andallows effective management of resource withminimum life costs



50/60

Intelligent Building-Definitions

IBI (The Intelligent Buildings Institute in

Washington DC, US): one that provides a

productive and cost-effective environmentthrough optimization of its four basic

components - structure, systems, services

and management - and theinterrelationships between them.



51/60


52/60

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



53/60


54/60

Building Energy Management Systems-How much energy can be saved



55/60

Building Energy Management Systems- Hardware

The basic architecture consists of: Multiple programmable control panels, called Network Control

Units (NCUs) [each NCU manages an area of the building facility]

OperatorWorkStations (OWSs) that communicate with each other

over a high speed communication network [normally a standardPC]

This communication network is called LocalArea Network (LAN)

NCU capacity can be increased with remote panels calledNetwork 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 delegatedto a family ofApplication Specific Controllers (ASCs)



56/60

BEM Systems Software [1]

Direct Digital Control (DDC) is the major concept ofBuildingAutomation System (BAS) in nowadays

DDC control e.g. loops for damper operation are available toprovide ventilation requirements or to utilize outdoor air forcooling

Building energy management features are available inside amodem 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 byapplying night ventilation



57/60

BEM Systems Software [2]

The enthalpy program monitors the temperature and relativehumidity or dew-point of the outdoor and return air and thenpositions the outdoor air and return air dampers to use the airsource with the lowest total heat or least enthalpy

The load reset program controls heating and/or cooling tomaintain comfort conditions in the building while consuming aminimum amount of energy

The zero- energy band program saves energy by avoidingsimultaneous heating and cooling of air delivered to spaces

The occupied-unoccupied lighting control is a time-basedprogram that schedules the on/off time of lights for a building orzone to coincide with the occupancy schedules



58/60

BEM Systems Architecture [1] General Architecture

Central Unit

Sensors Actuators



59/60

BEM Systems Architecture [2] General Architecture

Central Unit

LocalController

LocalController

LocalController

ActuatorsSensors ActuatorsSensors ActuatorsSensors



60/60

BEM Systems Architecture [3] The structures of BEMS change with evolution of technologies andproducts.

Early BEMS were centralized energy management systems and firstappeared in the 1970s, having been developed in the USA. Thecentral station was based on a minicomputer, which contained theonly computing power or "intelligence" in the system, with "dumb" orunintelligent outstations which were boxes or cabinets for relays andconnections to sensors and actuators.

Since about 1980, with the rapid development of technologies, theoutstations became as powerful as the previous minicomputer, if notmore so.

Also, the outstations have gained considerably in processing powergiving them "intelligence".


Date post:	02-Apr-2018
Category:	Documents
Upload:	dreamseller123
View:	219 times
Download:	0 times

123451109 Intelligent Building Technology

Documents