ensuring comfort in office buildings

Ensuring comfort in office buildingsDesigning a KNX monitoring and control system

Dr. Ing. Catalin BujdeiProf. Dr. Ing. Sorin-Aurel Moraru

TRANSILVANIA UNIVERSITY OF BRASOV, ROMANIAELECTRICAL ENGINEERING AND COMPUTER SCIENCE

RESEARCH DEPARTMENT:SYSTEMS FOR PROCESSES CONTROL

The 7th International Conference on Intelligent Environments 25-28 July 2011, Nottingham, United Kingdom

Content

City, University and Genius Campus

The main research project

Comfort demands

Employee eficiency

Comfort

Thermal comfort

Visual comfort

Acustic comfort

Air quality comfort

Long term comfort

KNX automation system

WSN network node

Brasov city

core of the country

old cultural city, hosting the first school in Romanian

multinational and multilingual area (romanian, hungarian, german citizens)

Transilvania University of Brasov, Romania

State University, founded in 1948

“Full Confidence” in the national evaluation

Ranked among the first at national level for Research of Excellence

Extended cooperation with European universities

Transilvania University of Brasov, Romania

Genius Campus – the new Institut

RTD Institute(Structural Founds)

Education Area(Regional Founds)

Students Facilities(Governmental

& Regional Founds)

Business Centre(Structural Founds)

Clusters research providers + + research direct andindirect beneficiaries

Technology Transfer

The Solar Park(RTD Projects)

Phase 1

Phase 1

Phase 2Phase 2

Phase 3

Genius Campus – the new Institut

September 2009April 2010

May 2011

March 2011

The main research project

Main goals:

– implement a wireless sensor network (WSN) for ambient conditions monitoring and control

– integrate building systems together (central information storage, monitor and control)

– increase the energy efficiency

– increase the comfort of the occupants

at the end of the work a comparison could be made for determine the efficiency of the obtained results

Comfort demands - evolution

long time ago …(simple life style)

present(complex life style)

future(more complex life style)

Employees efficiency

a person could accomplish successfully its activities as long there are no external factors which to disturb him (e.g. heat, cold, noise, low air quality)

if the comfort is satisfied also the maximum efficiency of the employees is ensured

a low decrease in employees efficiency for a big company represents a huge lost of time and money

Employees efficiency

At a new office building design

– the initial cost and energy efficiency are the first points analyzed

– the people’s comfort (with influence to their productivity) is less discussed

As observations:

– people spend 80-90% of the time from their lives indoor

– the lighting, heating, air conditioning, ventilation systems ensure comfort to the occupants of the building

– it is not possible to reach the highest level of comfort, since could not exist a maximum for it, but we could make one step further into the future and create better conditions for our indoor lives

Comfort characteristics

comfort = all existent conditions from a space for which a person will not prefer a different space with other conditions

ISO 7730 defines the thermal comfort as that condition of mind which express satisfaction with the thermal environment (thermal neutrality – when a person doesn’t feel too warm, either too cold)

comfort = a complex concept that depends on a set of external and internal factors.

Maybe it is easier to define what it means, but it is more complicated to convert the definition into physical parameters and establish relations between them (create equations that will permit a mathematical analysis)

Comfort types

The indoor comfort could be described from multiple points of view:

– thermal: temperature, humidity and air velocity (very import type of comfort)

– visual: light intensity and other factors which could influence a person view

– acoustic: maximum level of noise or repeatable noise

– air quality: parameters which characterize the air conditions and are suitable for respiration and human health (e.g. oxygen level, pollutions level)

– stability: without uncomfortable movements, vibrations or shocks;

– security comfort: feel safe at the working place;

– daily timetable: a constant daily timetable will not influence the life habit;

– economical factors: the fear of insufficient funds for proper living.

A person could feel comfortable from some points of view but uncomfortable from other points of view.

Thermal comfort

directly dependent on temperature, humidity and air velocity parameters

Markus and Morris, would describe thermal comfort with the following parameters:

– physical parameters: air temperature, radiant temperature, relative humidity, air velocity, atmospheric pressure and light intensity;

– organic parameters: age, sex, national characteristics;

– external parameters: activity type, clothing type, social conditions.

many studies have been done on thermal comfort and how it is possible to define it into a mathematical form

Thermal comfort – mathematical form

first mathematical model used for estimate the thermal comfort was proposed by Fanger, 1970. He started from the equilibrium equation (how the human body maintain the heat balance).

Heat produced by the body = Heat lost by the body

Thermal comfort – mathematical form

Seppanen made a study to determine the influence of temperature to the health and productivity. The analyze concluded that exists about 2% decrement in work performance per 1 °C increment when the temperature is above 25 °C

the 21 to 25°C temperature range is considered to be the range of temperatures comfortable according to the thermal comfort standards.

from the experiments analyzed it resulted that the range should be 22 to 25°C, and that the lower values have better impact to the thermal comfort. The quality of the air could be better preserved at lower values of temperature. For this reason we will consider an initial value of 23.5 °C for our experiments and calculations.

Thermal comfort – ISO 7730 standard, PMV

The ISO 7730 standard proposed to use 2 parameters for estimating the thermal comfort level:

– PMV (Predicted Mean Vote) – defined from Fanger balance equation

• [-3, 3]; the negative values presume that it is discomfort caused by a cold sensation, and the positive values suggest discomfort caused by a hot sensation.

Parameters: metabolic rate (M, met), effective mechanical power (W, W/m2) , clothing area factor (fcl ), clothing surface temperature (tcl, °C), heat convective transfer coefficient (hc, W/m2/°C) , partial water vapor pressure in the air (pa,Pa), air temperature (ta, °C), thermal resistance of clothing (Icl, clo), mean radiant temperature (tmr, °C) .

Thermal comfort – ISO 7730 standard, PMV

– PMV (Predicted Mean Vote)

• seven-point ASHRAE thermal sensation scale – Fig. 2): hot (+3), warm (+2), slightly warm (+1), neutral – thermal comfort (0), slightly cold (-1), cool (-2), cold (-3)

– It is recommended that the value of the PMV parameter to be somewhere into the interval between -0.5 and 0.5.

– usually into a closed space (room) it is not a constant value of the PMV parameters in all the subareas, but distinct values according to different factors, since the characteristic parameters don’t have constant values.

Thermal comfort – ISO 7730 standard, PPD

– PPD (Predicted Percent of Dissatisfaction)

• the percent of people which feel the sensation of discomfort

• when PMV has a 0 value, PPD will have a value of 5%. it is impossible to ensure thermal comfort for all the people, because of the existing differences between them (e.g. activities, clothing and metabolism).

– The goal is to ensure thermal

comfort for as many people as

possible.

Thermal comfort

Thermal comfort – local discomfort

Thermal comfort – ISO 7730 standard, PMV, PPD

– The studies realized by ASHRAE (American Society of Heating, Refrigerating and Air-conditioning Engineers Inc.) have concluded that the PMV parameter could be used to determine the neutral (comfort) temperature with a margin of error of 1.4 °C.

– As many other studies presented, there could be a difference between the comfort established using the PMV and PPD indices and real life felt comfort.

– For this reason we consider that the thermal comfort should be establish in 2 distinct steps (solution which to be used together with the KNX system and WSN):

• computing using the models - determination of ambient parameters which should ensure the minimum PPD value;

• calibration - the variation of the ambient parameters according to the occupancies opinion until a point of equilibrium could be found (where the most of people feel comfortable in that ambient conditions).

Thermal comfort – PMV, PPD indices calculation

Matlab application:

– M =1.2 met = 69.78 W/m2;

– W= 0 W/m2;

– fcl = 1.15;

– hc = 6.0 W/m2/°C;

– Icl = 1.0 clo = 0.155 m2°C/W;

– φa = 45% (relative humidity; it permits to calculate the pa parameter value);

– ta = 23.5 °C;

– we approximate tmr = ta + 2 °C = 25.5°C.

PMV = 0.0403

PPD = 5.0336

thermal comfort could be ensured into the office space with these

parameters values (at least from mathematical equations).

Visual comfort

– it is necessary to ensure a normal level of light intensity.

– inside an office space most activities involve the use of a computer. From this point of view it is necessary to ensure an equilibrate contrast between the screen light and the light from the ambient.

– It is also important to not have flashing lights which could distract the attention and which could produce rapidly tiredness.

Since most of the activities from an office

suppose a short distance focus of the eye,

it is important to have the possibility to change

this distance – very important for the health

of the human eye.

Acoustic comfort

Noise is represented as a negative sound and it’s always unwanted.

Inside an office space, it is important to have a low level of noise. In this way the occupancies will be able to achieve their activities more easily without being distracted.

It has been determined, from our own observations or studied papers, that into the office spaces could be presented the next types of noise sources:

external noise: refers to the noise

raised from outside building sources.

This type of noise could be determined

by the road traffic, industrial machines,

community activities, etc.

inside noise: refers to the noise produced by the installations .

(systems) or equipment from inside the building. .

Acoustic comfort - NPD

Clausen defined a mathematical equation for the acoustic discomfort.

NPD (Noise Percentage Dissatisfied)

– x, class of noise [dB]

when NPD < 20% -> comfortable.

Air quality comfort - QPD

The quality of the air ensures that the human body performs properly and a person is able to accomplish its activities in normal conditions. If the quality of the air is low it could appear health affections, but also fatigue and decrease of concentration.

QPD – Air Quality Percentage Dissatisfied

– CO is the perceived value of outdoor air quality [decipol];

– G is intensity of indoor air pollution [olf];

– Q is the flow rate of fresh air [l/s].

Air quality comfort - QPD

Ilinois Department of Public Health (IDPH) created guidelines to be followed for ensuring indoor air quality (these are not mandatory but recommended).

A part of guidelines have been defined also by the ASHRAE Organization.

Air quality comfort - parameters

Humidity and Temperature:The humidity is considered to be acceptable somewhere in the interval of values of 30-60 percent indifferent of the season time. For summer it is recommended a temperature of the air of 23-26 °C and in the winter of 20-24 °C.

Carbon dioxide:Carbon dioxide is a constituent of the exhaled breath and it is normal that in closed spaces with low ventilation and many occupancies the value of the carbon dioxide to increase. Into the outdoor environment the normal value is somewhere between 300-400 ppm (parts per million).

Carbon monoxide:Carbon monoxide is produced usually during the incomplete combustionAnd its property of being colorless and odorless makes it hard to detect by a person. Into an office area the normal values of this parameter are considered to be between 0-5 ppm.

Hydrogen SulfideIts normal value, into a building, is under 0.01 ppm. A higher valuecan be detected by the people inside the building (it has an easy detectable odor).

Ozone

The normal level of ozone is under 0.08 ppm.

Particles (dust)

Long term comfort

Long term comfort refers to all the factors that could affect a person after a longer period of time.

Into an office space the long term discomfort could be determined by electromagnetic radiation produced by different equipment (wireless communication), continuous repeatable noise, pollutants presence (even they are not perceptible by smell), the continuous presence of cold, toxic behavior of the building construction materials, etc.

CPD index

CPD (Comprehensive Percentage Dissatisfied)

– for comfort evaluation, according to thermal factor, noise and indoor air quality

TPD – Thermal Percentage Dissatisfied (same as PPD)

NPD – Noise Percentage Dissatisfied

QPD – Air Quality Percentage Dissatisfied

α1 = 0.6738, α2 = 0.1007, and α3 = 0.2255 (determined by gradation analyze)

The CPD index varies in the interval of values 3.37 and 100:

• < 20, comfortable;

• 20 – 40, little uncomfortable;

• 40 – 60, some uncomfortable;

• 60 – 80, uncomfortable;

• 80 – 100, very uncomfortable


KNX system, a small part of a BMS (Building Management System)

integrate the KNX system with a Wireless Sensor Network (WSN) - both of them could monitor parameters and control different systems.

the sensor nodes of the WSN network are still under developing. They should be able to compute aproximatively the comfort indices PMV, PPD, NPD, QPD and CPD.


– configurable classroom

– the cost of the KNX system is quite high but after installation it should produce an increase of the comfort and decrease of the energy consumption.

– another advantage of this type of system is that it could be easily reconfigured. It is possible to save different configuration (scenes) into the system memory and load them for specific usage situations.


the main components of the KNX system:

– 24V Voltage Source;

– USB Interface;

– KNX acting devices;

– KNX access panel;

– movable partition wall;

– Blinds;

– lighting;

– light intensity and movement detection sensors;

– heating.

WSN node (end device)

based on Arduino and Xbee

modular, easy reconfigurable, low cost

could be used with sensors or actuators auxiliary boards (monitoring and control)

Thank you for your attention!

questions sugestions

ensuring comfort in office buildings

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