Cisbat Stevanovic
-
Upload
dragance106 -
Category
Documents
-
view
226 -
download
0
Transcript of Cisbat Stevanovic
-
8/9/2019 Cisbat Stevanovic
1/6
ANALYSIS OF OPTIMAL FENESTRATION PARAMETERS FOR A
PASSIVE SOLAR OFFICE BUILDING IN SERBIA
S. Stevanović1,2
1: University of Primorska, Institute Andrej Marušič, Muzejski trg 2, 6 !o"er, #$ovenia2: University of %iš, &a'u$ty of #'ien'es and Mat(emati's, )išegradska **, 1+ %iš, #eria
ABSTRACT
Fenestration, important for adding aesthetics to the building design and providing adequate
daylight illumination levels, also plays a vital role for thermal comfort in buildings and is
easily considered as the most important individual strategy in passive solar design of
buildings. Purpose of this wor is to analyse and discuss optimal fenestration parameters for
an office building located in !elgrade, Serbia. "ffice buildings are characteri#ed by high
internal gains due to the presence of people, computer equipment and lighting during thewor hours, which may be beneficial in the heating season, but may pose a significant
problem in the cooling season.
$he case study is a four%story office building, rectangular in shape, with longer sides facing
south and north. &indows are present at southern and northern walls only. $he design
parameters include si' gla#ing types for southern and for northern windows each, seven
values of windows%to%wall ratio for southern and northern facade each, presence of e'ternal
shading at southern windows, as well as three (%values of e'ternal walls. )n total, 1*,+-
parameter combinations have been simulated in nergyPlus, with the building in a free
running mode and with annual heating and cooling discomfort hours recorded at the output.
$he analysis is focused on the set of Pareto optimal solutions with heating and coolingdiscomfort hours as competing performance ob/ectives.
$he simulation results clearly demonstrate importance of improved thermal insulation in the
continental climate of !elgrade and the necessity of using superior triple, low%e, argon%filled
gla#ing for all building variants with larger than minimal southern windows%to%wall ratio. $he
optimal choice of the southern windows%to%wall ratio turns out to be between 0,+ and +*,
with e'ternal shading of southern windows, while the optimal choice of the northern
windows%to%ratio is between 2+ and 0,+.
!ey-ords: "assive so$ar design, offi'e ui$ding, fenestration, Pareto front, .nergyP$us/
INTRODUCTION
Passive solar design strategies aim to use solar energy to help establish thermal comfort in
buildings, without the use of electrical or mechanical equipment. $he greatest opportunities
for integrating passive solar design strategies occur at the conceptual design level, by
determining the values of building envelope parameters that have critical influence on its
thermal performance. !uilding energy simulation plays a fundamental role in this process,
since the building3s future response to applied passive solar design strategies is highly
sensitive to local climate factors.
4mong the passive solar design strategies, fenestration may be considered as the most
important, since it has the largest influence on the admission of solar energy into the building
and, hence, plays a vital role in its thermal comfort. $he purpose of this wor is to analyse and
-
8/9/2019 Cisbat Stevanovic
2/6
discuss optimal fenestration parameters for an office building located in !elgrade, Serbia.
!elgrade has continental climate with hot summers 56fa in 78ppen classification9, with
average ma'imal monthly temperatures of 2,0:; in suggests
two alternative optimal building plans? a square plan, which minimi#es the ratio of the
envelope surface and the interior volume and thus increases energy efficiency, or an elongated
rectangle plan, with longer side oriented towards south, which enables better passive use of
available solar energy during winter. $he case study considered here has, therefore, a
rectangular plan with dimensions 2*m ' 1-m and four stories of -m storey height. "ffice
building is of open plan, so that the model has no internal partitions 5e'cept towards spaces
that do not have large influence on thermal characteristics, such as staircases and restrooms9.
!y current Serbian legislative =0>, e'terior walls have (%value at most *,0&@m27, while
typical (%value for e'terior walls of passive houses is around *,1 &@m2
7. $hree alternative(%values A *,1 &@m27, *,2 &@m27 and *,0 &@m27 have been used in simulations. 'terior
walls consist of plastic malter *,+cm on the outside, e'panded polystyrene of adequate
thicness, hollow bric 2+cm and cement stucco 2cm on the inside. $he remaining opaque
envelope components have fi'ed values? slab on the ground has (%value *,2-B &@m 27, the
construction between stories has (%value *,-1B &@m27, while the flat roof has (%value *,1-
&@m27. ;oncrete ceiling of each storey is stripped down, so that it serves as a thermal mass,
while the insulating layer above it reduces the transfer of accumulated heat to upper stories.
)nfiltration rate is good and set to *,+h%1.
Cla#ing properties have significant impact on a number of building functions? its (%value is
important for preservation of heat within the building, the solar heat gain coefficient 5SDC;9determines the transmittance of solar energy, while the visible light transmittance coefficient
5E9 influences the daylighting and reduces the needs for artificial lighting. Si' common
gla#ing types, whose properties are given in $able 1, have been considered in the case study.
Glazing U-value (!"#$% S&GC VL
double, clear 2,-2 *,-0 *,*1
double, clear, selective 1,B2 *,-21 *,B2
double, tinted, selective 1,B2 *,2G1 *,-*
triple, clear 1,G *,B+ *,20
triple, low%e, argon%filled *,G0 *,-G+ *,B+1
triple, low%e, tinted 1,21- *,2+- *,022
0a$e 1: $azing ty"es/
&indows%to%wall ratios 5&&H9 on southern and northern facade vary from 2+, necessary to
satisfy minimal daylighting requirements, to 1** in steps of 12,+. &indows shading is
provided with e'ternal blinds. !lind slats are hori#ontal with 1*cm depth and 1*cm vertical
distance between ad/acent slats, which shade windows completely from Iay 2* to September
2*, the period when ma'imal daily temperature is higher than 2:; in !elgrade =1>.
)nternal gains are determined by the presence of employees. &oring hours are am%-pm,
five days per wee, although it is assumed that a half of the employees will be present from
-
8/9/2019 Cisbat Stevanovic
3/6
.0*am%am and also from -pm%-.0*pm. ach employee occupies area of Gm2 and has a
1**& computer equipment. $he metabolic rate for light office wor, standing and waling,
for a mi' of equally many men and women, is 11-,0G& per person, which yields internal
gains of 20,2 &@m2 from presence of people and computer equipment. 4rtificial lighting uses
$+ tubes, which in the absence of daylighting, use 10,2&@m2 to provide -**lu' light intensity.
Since the gla#ing type and shading greatly influence availability of daylight, and respectivelythe energy needed for artificial lighting, the case study has a photosensor at des height in the
center of each storey and linear lighting control.
Jatural ventilation is used as a passive cooling measure, as the oscillation between ma'imum
and minimum daily temperatures in !elgrade is 1*,-:%1*,+: from Iay to . Jatural ventilation is available from 4pr 1+ to "ct 1+ during
woring hours as necessary and during nighttime from 1*pm to Bam, whenever the internal
temperature is above 2*:; and above the e'ternal temperature. )t has ma'imum rate of +,*h %1,
with at most 2* of windows area allowed to open. Further, mechanical ventilation is used to
provide minimum of 1*l@s of fresh air per person during woring hours.
SIMULATION RESULTS
$he case study office building has several variable parameters? three e'terior walls (%values
5*,1K *,2K *,0 &@m279, si' gla#ing types for southern facade 5$able 19, si' gla#ing types for
northern facade 5$able 19, seven &&H values for southern facade 52+K 0,+K ...K 1**9,
seven &&H values for northern facade 52+K 0,+K ...K 1**9 and the indicator of
presence@absence of southern windows shading. )n total, 1* +- building variants were
simulated in nergyPlus, using /Plus =B> to automate simulation process.
$he building variants were simulated in free running mode, with the simulation output
consisting of heating and cooling discomfort hours. )f zone,i,j,t denotes operative temperature in
#one i 5iL1,2,0,-9 during the woring day 3 in a year and 1+%minute long timestep t , then the
heating discomfort hours are defined as
9,:;*,:;2*ma'5-
1,,,
,,
t ji zone
t ji
0 454 −=∑ 519
while the cooling discomfort hours are defined as
9.:;*,:;2Bma'5-
1,,,
,,
−=∑ t ji zonet ji
0 654 529
Dence, the heating discomfort hours represent the number of degree hours that the operative
temperature is below the heating setpoint of 2*:;, while the cooling discomfort hours
represent the number of hours that the operative temperature is above the cooling setpoint of 2B:;. $he discomfort hours have been used before in =-,+> as the heating and cooling energy
indicators. ssentially, as pointed out in =+>, it can be e'pected that the building minimi#ing
heating and cooling discomfort hours will also minimi#e heating and cooling energy demand.
Jatural ventilation was simulated using the nergyPlus option ;alculated, which taes into
account wind and buoyancy effects. Simulation of each building variant too between 11*s
and 1-*s on Fu/itsu ifeboo 2 with )ntel ;ore i%0B12MI processor on 2.1CD#. Since
the processor allows e'ecution of eight nergyPlus simulations in parallel, simulation of all
1* +- building variants too litlle more than +* hours.
Figures 1%- represent heating and cooling discomfort hours for all building variants,
differently colored with respect to e'ternal wall (%value 5Fig. 19, southern gla#ing type
-
8/9/2019 Cisbat Stevanovic
4/6
5Fig. 29, southern &&H 5Fig. 09 and northern &&H 5Fig. -9. $hese figures also show the
Pareto front, made from those building variants for which no other variant has smaller both
heating and cooling discomfort hours. $he Pareto front, in this case, is made up of two parts? a
steep line on the left with heating discomfort hours below +**:;, and an almost hori#ontal
part with cooling discomfort hours below 2 +**:;. Since heating requires substantially more
primary energy than cooling, the five Pareto solutions situated at lower left peas in the steep part of the Pareto front may be considered as the optimal choices. $hese five Pareto solutions
all have?
• e'terior walls (%value of *,1* &@m27,
• triple, low%e, argon%filled gla#ing at both southern and northern windows,
• shading present at southern windows,
• northern &&H equal to minimal value of 2+,
while the southern &&H ranges from ,+ for the variant with 5 454 , 54 9L5+ 12:;,
1* 2*-:;9 down to 0,+ for the variant with 5 454 , 54 9L5 0B+:;, 2 +0:;9.
&igure 1: 7ui$ding variants 'o$ored a''ording to U8va$ue/
&igure 2: 7ui$ding variants 'o$ored a''ording to sout(ern g$azing ty"e/
-
8/9/2019 Cisbat Stevanovic
5/6
&igure *: 7ui$ding variants 'o$ored a''ording to sout(ern 99/
&igure ;: 7ui$ding variants 'o$ored a''ording to nort(ern 99/
DISCUSSION
)t can be seen from Figure 1 that the building variants with smaller e'terior wall (%value are
generally closer to the Pareto front than the building variants with higher (%value. $ogether
with the fact that all Pareto optimal variants have the e'terior wall (%value of *,1 &@m27, this
clearly demonstrates the importance of thermal insulation in the continental climate of
!elgrade. Jevertheless, large overlaps between areas with different (%values also show that
the (%value itself is not the only decisive factor, as the numbers of heating and cooling
discomfort hours largely depend on fenestration parameters as well.$he grouping of variants according to the type of southern gla#ing is easily noticeable from
Figure 2. $he smallest heating and cooling degree hours are generally obtained when triple,
low%e, argon%filled gla#ing is used at the southern facade, and all Pareto optimal solutions
with less than 1* ***:; heating discomfort hours have this gla#ing type both at southern and
northern windows, together with shading present at southern windows. $he triple, low%e,
argon%filled gla#ing is superior to other gla#ing types due to the smallest (%value, important
for heat conservation during the heating season, and medium SDC; value. &hile it can be
noticed from Figure 2 that some building variants, which use triple, clear or even double,
clear gla#ing, are close to the lower left part of the Pareto front, such variants have minimal
southern &&H, which limits the influence of gla#ing parameters.
-
8/9/2019 Cisbat Stevanovic
6/6
Iost Pareto optimal solutions have the southern &&H equal to either 2+ or 0,+. $here
is, however, a number of Pareto optimal solutions with the southern &&H between +* and
1**, which all have triple, low%e, argon%filled gla#ing both at southern and northern facades
and shading present at southern windows. $hese variants, due to the beneficial effect of winter
solar gains have the smallest heating discomfort hours 5less than ***9, but at the same time
have the largest cooling discomfort hours 5from 0 +- for the southern &&H of +* up to10 -0B for the southern &&H of 1**9. $he optimal choice of the southern &&H is
between 0,+ and +*, with shading present, which enables beneficial effect of solar gains
during the heating season, without large negative impact on cooling discomfort hours.
$he northern &&H has significant impact on heating and cooling discomfort hours, as visible
from Figure -. !uilding variants with larger northern &&H are generally further away from
the Pareto front, while only variants with the northern &&H up to +* appear close to the
lower left part of the Pareto front. $he fact that Pareto optimal solutions come in pairs, one of
which has the northern &&H of 2+ and the other 0,+, suggests that these values are
optimal choices for the northern &&H, which prevent large heat loss during the heating
season, with appropriate influence on cooling of the interior space during summer months.$he northern gla#ing type, with such &&H, does not appear to have large influence on the
number of discomfort hours.
AC$NOLEDGEMENTS
$he author has been supported by the Hesearch Pro/ect $H0B*0+ NSpatial, environmental,
energy and social aspects of the development of settlements and climate change A mutual
influencesO of the Iinistry of ducation, Science and $echnological 6evelopment of the
Hepublic of Serbia.
REFERENCES
1. Hepublic Dydrometeorological Service of Serbia? Ieteorological yearboo A climate data 2*11, !elgrade, 2*12. 4vailable at
http?@@www.hidmet.gov.rs@podaci@meteogodisn/aci@ Ieteorolosi2*godisn/a
2*12*%2*limatolosi2*podaci2*%2*2*11.pdf , accessed 4pr 2, 2*10.
2. Stevanović, S.? "ptimisation of passive solar design strategies. Henewable and
Sustainable nergy Heviews, 2*10, accepted for publication.
0. Covernment of the Hepublic of Serbia? Hegulation on energy efficiency of
buildings. "fficial Ca#ette of the Hepublic of Serbia, Eol. B1, !elgrade, 4ug 1G,
2*11.
-. Porritt, S., Shao, ., ;ropper, P., Coodier, ;.? 4dapting dwellings for heat waves.Sustainable ;ities and Society, Eol. 1 52*119, 1%G*.
+. !ouchlaghem, J.? "ptimising the design of building envelopes for thermal
performance. 4utomation in ;onstruction, Eol. 1* 52***9, 1*1%112.
B. Qhang, R.?