Examples of IEQ factors. Healthy IEQ and energy efficiency. What type of system is the best? Ideas and concepts from research and reality.

Transcription

1 Healthy IEQ and energy efficiency Ideas and concepts from research and reality Lars Ekberg Energy Management AB A Chalmers Industriteknik Company 1 Examples of IEQ factors Thermal climate -operative temp. -surface temp. -air movements - Air Quality -formaldehyde -nitrogen dioxide -particles - Illustration: SP The Swedish Technical Research Institute 2 What type of system is the best? What type of system is the best? Mechanical ventilation Displacement ventilation A system suited for its purpose Designed with respect to the building, the activities and the requirements Hybrid ventilation Air conditioning Natural ventilation Mixing ventilation Correctly dimensioned and designed with respect to service och maintenance Designed so that it does not cause disturbance (draught and noise) 3 4

2 Indoor Environment Guidelines Thermal Climate (EN ISO 7730) Desired operative temperature, air velocity etc. PMV & PPD indices Portugese offices Thermal climate Swedish offices Indoor Air Quality (EN 15251, WHO, ISIAQ ) Mainly specification of airflow rates required Limited guidelines regarding specific air pollutants 5 Reference: Stoops, J. (2001) 6 Air Quality CO 2 The CO 2 requirement Portugese offices Swedish offices CO 2 - indicator for the perception of pollutants from people Percentage dissatisfied (%) Note, Valid for visitors! (Fanger, 1988) Your experiences? CO 2 concentration (ppm) Reference: Stoops, J. (2001) 7 8

3 The CO 2 requirement 60 To make the technical solution work The air distribution system Percentage Dissatisfied, dissatisfied % (%) North Americans Common air hygiene criterion of today Europeans Japanese Discussed among researchers Ventilation rate, l/s per standard person Outdoor air supplied (l/s per person) Pollution Climate + - Heat Pollution and the technical solution 9 10 How to ensure efficient ventilation? Displacement ventilation Right! Illustration: SP Heat sources in the room Relatively cooler supply air Correct placement of air terminal units Appropriate supply air temperature Correct adjustment of the throw length Sufficient airflow rates Two main principles displacement and mixing ventilation 11 Wrong! The supply airflow rate Too high supply air may also be too low! temperature! 12 Illustration: SP

4 Mixing ventilation Risk of annoyance! Displacement ventilation Right! Relatively cooler supply air Sufficient throw-lenght Too high supply air temperature! Illustration: SP Wrong! Too low supply air velocity! Cold air and air movements close to the air terminal unit Always high risk of draught within about 1 2 m Risk of annoyance! Mixing ventilation The room air distribution can be checked by tracer gas measurements Air change efficiency Ventilation efficiency Local air change index Local air quality index.. Downdraught if supply air velocity is too low Risk of draught if incorrect design or operation Caution! This may be time consuming and expensive! 15 16

5 The air change efficiency, ε a Mixing ventilation ε y0.45 Displacement ventilation ε y0.65 Piston flow ε y % higher efficiency with displacement ventilation? 17 Illustration: Skistad Ventilation effectiveness Local ventilation index Contaminant removal effectiveness C exhaust C breath 18 Ventilation effectiveness Local ventilation index Contaminant removal effectiveness When cooling Mixing ventilation The Stratification Displacement ventilation Reference: CEN CR % higher efficiency with displacement ventilation? Supply airflow rate 8 l/s per person Walking speed 0.7 m/s 19 Reference: Mattsson, M. (1999) 20

6 People moving Classroom experiments Supply airflow rate 8 l/s per person Walking speed 1.3 m/s Reference: Mattsson, M. (1999) 21 Reference: Mattsson, M. (1999) 22 The classroom IAQ A simulated office Tracer gas measurements Tracer gas generation Reference: Mattsson, M. (1999) 23 Reference: Mattsson, M. (1999) 24

7 The office IAQ The office IAQ 21 l/s and heat generation 295 W No disturbance by movements Reference: Mattsson, M. (1999) l/s and heat gen. 395 W 37 l/s and heat gen. 395 W No movements by person simulator Reference: Mattsson, M. (1999) 26 People moving in the office A sportshall Breathing zone Height = 4.2 m CO 2 measurement Pollution spread to the breathing zone The computer was the only source of contamination Reference: Mattsson, M. (1999) 27 Reference: Matson, M. (1999) 28

8 The sportshall IAQ The examples indicate that displacement ventilation works: without disturbance from movements if the supply airflow rate is high enough CO l/s 3 l/s per m 2 floor Six people W lighting Reference: Matson, M. (1999) 29 Typical applications are found in the industry High rooms Large airflows required for removal of 30 heat and that displacement ventilation does not work: If the supply airflow rate is too low even with moderate disturbances Why not displacement in offices? Major risk of discomfort due to draught Reduced useable floor area Because it may need 3 4 times higher airflow rate than required for air hygiene Displacement ventilation requires l/s per person Air hygiene requirement is about 10 l/s per person 31 32

9 The energy aspect Some calculated examples Mixing Displacement 16 C 24 C 24 C 26 C 24 C 18 C Assume correct function 33 Temperature ( C) Energy for air handling Mixing Duration (hours per year) 15 kwh/m 2 per year Flow rate = 3 l/s per m 2 Outdoor temp T_supply = 16 deg C 40 Electricity for cooling 34 Temperature ( C) Displacement Duration (hours per year) 9 kwh/m 2 per year Outdoor temp T_supply = 18 deg C > Fan electricity = 27 kwh/m 2, year in both cases Temperature ( C) If we add demand control: Ventilation rate Duration (hours per year) Outdoor temp Supply temperature Demand control Electricity (kwh/m 2 per y) Min flow rate Max flow rate t sup t room t exh Fans Cooling Total 1 l/s, m 2 3 l/s, m 2 16 C 24 C 24 C l/s, m 2 3 l/s, m 2 18 C 24 C 26 C l/s, m 2 3 l/s, m 2 18 C 24 C 26 C l/s, m 2 3 l/s, m 2 18 C 24 C 26 C C 24 C 24 C 26 C 24 C 18 C 35 36

10 Further examples Literature Im, P. (2005) Literature review on underfloor air distribution (UFAD) system, Energy Systems Laboratory, Texas A&M University System Mattsson, M. (1999) On the efficiency of displacement ventilation with particular reference to the influence of human activity, Royal Institute of Technology, Stockholm Novoselac and Srebric (2001) A critical review on the performance and design of combined cooled ceiling and displacement ventilation systems, Energy and Buildings, 34, Matsumoto,H. and Ohba, Y. (2004)The influence of a moving object on air distribution in displacement ventilated rooms, Jour. Asian Arcitecture and Bldg Eng. Fitzner,K. (1996) Displacement ventilation and cooled ceilings, Results of laboratory tests and practical installations, Proceedings of the Conference Indoor Air 96, Nagoya Lau, J. And Chen, Q. (2006) Energy analysis for workshops with floor supply displacement ventilation under the U.S. climates, Energy and Buildings, 38, Kim, I.G., Homma, H. (1992) Distribution and ventilation efficiency of CO2 produced by occupants in upward and downward ventilated rooms. ASHRAE Technical Data Bulletin, Vol. 8, No. 2. Mattsson, M. (2002) Vertical distribution of occupant generated particles in a room with displacement ventilation, Proceedings of the Indoor Air 2002 Conference, Vol. 1, pp , Monterey, California Nielsen, P.V. (1993) Displacement Ventilation Theory and design, Dept. Of Building Technology and Structural Engineering, Aalborg University, Denmark REHVA Design Guidebook No. 1, Displacement Ventilation in non industrial Premises, 2 endition, 2002, Federation of European HVAC Assoc Source: Novoselac and Srebric (2001) Healthy IEQ and energy efficiency Deviation from desired climate Energy Management AB A Chalmers Industriteknik Company Loads Desired climate Minimize the energy use and the complexity: Thank you! Sun irradiation, people, equipment, lighting, pollution generation, building products, furniture Compensation by installations -Minimize the loads -Motivate the requirements lars.ekberg@cit.chalmers.se 39 40

11 The supply airflow rate will match the thermal plume 36 m 3 /h = 10 l/s Extra material 200 m 3 /h = 55 l/s 36 m 3 /h = 10 l/s 200 m 3 /h = 55 l/s Experiments by Kim & Homma 1992 Ventilation efficiency 1,4 1,2 1 0,8 0,6 0,4 0,2 0 Kim & Homma (1992) Three out of 15 "Upward" experiments beytter than mixing ventilation The "Downward" experiments indicate poor function at low ventilation rates Ventilation rate (l/s per person) Upward Downward 43 No draught No noise The right temperature Possibility to control the climate Clean air No unpleasant smells 44

12 Air change rates (ACH = air changes per hour) Control of air quality by removal of air pollutants Residential buildings ACH Office rooms with hydronic cooling ACH Operating theatres in hospitals ACH Clean rooms >200 ACH How the indoor climate occurs Deviation from desired climate Desired climate Control of temperature by removal of heat surplus Office rooms with an all air system 3 6 ACH Supermarkets, department stores 6 10 ACH Auditoriums, lecture rooms, theatres 5 12 ACH Compensation of air exhaust required for safety ventilation, process air flows Laboratory rooms with fume hoods Restaurant kitchens ACH ACH How the indoor climate occurs Deviation from desired climate How the indoor climate occurs Deviation from desired climate Desired climate Desired climate Loads Sun irradiation, people, equipment, lighting, pollution generation, building products, furniture Loads Sun irradiation, people, equipment, lighting, pollution generation, building products, furniture Compensation by installations Compensation by Heating or cooling Removal of pollutants 47 48

13 How the indoor climate occurs Deviation from desired climate Desired climate Loads Sun irradiation, people, equipment, lighting, pollution generation, building products, furniture The complexity and size of the installations depend on The strength of the loads The indoor climate requirement Compensation by installations 49