PLEA’99 Conference
Refereed paper

INTEGRATION OF NATURAL AND ARTIFICIAL LIGHTING SYSTEMS:
A CASE STUDY OF THE CENTRAL MARKET RETROFIT OF BELO
HORIZONTE, BRAZIL
R V G de Souza, F Har å, E S de Assis, C P Vono, G F Viana Jr, T P Alves, V C D Lara
School of Architecture
Federal University of Minas Gerais, Belo Horizonte, Brazil
fax:
+55 031 269 1818
e-mail:
roberta@arquitetura.ufmg.br
ABSTRACT This paper presents a retrofit study, winner of the ’97 and ’98 Student Prizes
in Energy Efficiency and Honor Mention in Architecture of the Engineering Society of Minas
Gerais. It is a pioneer study in Brazil in terms of integration of natural and artificial lighting
systems. It deals with concepts of user comfort, environmental quality and artificial systems
optimization in order to achieve energy efficiency and conservation. The Central Market of
Belo Horizonte (28 800 m2) was detected as having poor lighting environment and its
potential of improvement in terms of quality and energy use was therefore analyzed. The
existing systems were measured and quantified and a retrofit approach was developed. The
results show that, improving the lighting conditions, a 41% energy saving could yet be
achieved in the public lighting system – corridors and parking lot (21 100 m2 - 73% of the
total area)- of the Central Market.
1
Introduction
This retrofit study aims to develop strategies to reduce the electric energy demand for
lighting in the commercial sector using the Central Market of Belo Horizonte as a case study.
This is justified by the great savings that can be achieved in this sector of the Brazilian
economy. The demand on electric energy for buildings (commerce and residences)
represents 54% of the total demand on electric energy in Brazil. The commercial sector
represents 18% of the total demand (Efficientia 98, 1998) and uses 40% of this electric
energy in lighting (ABILUX 1991).
This study also intends to integrate the use of natural illumination with the existing energy
conservation culture, reducing the need for artificial lighting and adding visual quality to the
built space. In order to quantify the savings obtained by the use of natural lighting a
methodology was developed that takes into account the mean available illuminances
obtained through IES mathematical models (in ASSIS, 1997), as there is no available
measured data of sky illuminances for Brazil.
The study is restricted to the natural and artificial illumination systems evaluation of the
common areas of the market (first floor’s circulation, parking lot and managing department).
The private portion is not included, as each owner has an independent lighting system and
there was not enough time to gather data about energy use of the individual stores. The area
studied represents 73% of the total, 21 100 m2.
2
The central market
Built in 1929 and acquiring its final configuration in the 60s, the Central Market of Belo
Horizonte is a building of historical importance and social significance in the landscape of the
city. It has a traditional, popular commercial character, of 28 800 m2 area, distributed in two
floors. The stores are located in the first floor while the second floor is occupied by the
parking lot and by the market’s administration department. In general, the parking lot serves
the clients of the market during the day and the public of the events that take place on the
conference centre, located in front of the market, at night.
As it hasn’t been modified since 1964, the market lighting system is obsolete and needs to
be retrofitted in order to achieve energy efficiency. It was also noted that the natural lighting
is very poor although there are clerestories intended to provide natural lighting for the space.
Both artificial and natural lighting systems are described in the following paragraphs.
The first floor artificial illumination system contains the circulation areas covered by the
parking lot’s floor. It has 190 luminaries of two 40W fluorescent lamps each, with a double
quick start ballast (20W). At the parking lot, the system contains 121 electric discharge
(mercury vapour) lamps - of which 40 of 250W are placed at the perimeter and 81 of 400W
are placed at the central area to illuminate the parking lot and the uncovered corridors of the
first floor.
The Central Market’s natural illumination is based on sidelight and toplight structures. The
sidelight structures are perforated ceramic blocks, that serve as external walls both to first
and second floor. These elements provide a good ventilation, but contribute poorly for natural
illumination as they are dark red and dirty (Fig.1). The toplighting is provided by 9
clerestories located on the metal dome ceiling that covers the parking lot. Those elements,
however, provide poor lighting as the ceiling is dark and the glass in the apertures is quite
dirty. As a result, the parking lot and the apertures for the first floor are quite dark (Fig.2).
Figs.1 and 2
External and internal views of the
Central Market of Belo Horizonte.
2.1
Figs.3 and 4 1st and 2nd floors plans. The hatched
areas represent stores and the solid fill the areas of
the 1st floor illuminated through the 2nd floor
The market’s existing artificial lighting system
In order to evaluate the artificial lighting system of the central market, a qualitative analysis
was done through visual observation and quantitative analysis through illuminance
measurements (ABNT, 1985; ABNT, 1991). Both on first and second floors, the working
plane was considered to be the floor, as the main activity in those areas is walking.
In the first floor, all the lamps are turned on for 24 hours. Although the luminaries are
regularly distributed along the corridors, there’s a feeling that the corridors are poorly
illuminated, as there are quite a lot goods displayed outside the stores, which absorb the
light. It was also noticed that the luminaires’ arrangement is not always the best, creating
zones of shadow between them (Fig.5). The mean illuminance levels registered are of 36 lux,
which is not enough for the circulation activity that demands at least 75 lux according to
Brazilian legislation (ABNT, 1991).
Fig.5a - 5b
Incorrect distribution of luminaires
Fig.6a - 6b
Correct distribution of luminaires
All the lamps in the parking lot are turned off during the day and turned on from 6:00 pm to
6:00 am. The mean illuminance level registered in the parking lot is 47 lux. Despite this value
is considered enough, once the Brazilian legislation demands a minimum of 50 lux on the
working plane (ABNT 1991), the illumination is unsatisfactory, since the luminaires are too far
apart and the surfaces are quite dark, creating a bad distribution of light through the space,
creating bright areas and dark zones. The differences in wattage of the lamps also create
different illuminances in a continuous area which should be homogeneous.
2.2
The market’s existing natural lighting system
The natural lighting system of the market was also analyzed through quantitative and
qualitative parameters. Qualitative analysis was done through a photographic survey and
quantitative analysis through measurements of the area’s illuminance levels. The qualitative
analysis of the natural illumination distribution was based on the methodology developed by
Demers and Hawkes (1995): the contrast and brightness levels were evaluated. The
quantitative analysis was done based on the Brazilian legislation for measuring the
illuminance levels of internal areas. (ABNT 1985; ABNT 1991).
The parking lot system, besides offering insufficient levels of illumination in general terms,
causes serious visual disturbances, with excess of contrast between shadow zones and
highly illuminated areas (as shown in the contrast study in Fig.7), which causes glare to the
people who park their cars, making them loose direction and orientation, making it difficult to
find the stairs to go downstairs or to locate the cars when returning from shopping.
Fig.7a
Photo of the parking lot in the second
floor. The high levels of contrast can de seen.
Fig.7b
Study of contrast levels according to the
methodology proposed by Demers & Hawkes (1995).
The isolux curves were built from the measurements taken using the software Surfer. The
natural illuminance levels are higher at the edges, where the ceiling domes are opened and
under the centre of the clerestories, showing an uneven distribution of light.
Fig.8
Illumination projection: the focal
illumination points are easy noted.
Fig.9- Illumination volume of the market’s interior
3
The retrofit
3.1
Optimization of the artificial illumination system
The artificial lighting systems of the Central Market were considered quite inefficient so a
whole new system is proposed, using efficient lamps, luminaries and ballasts in a more
rational arrangement. The new dimensioning was based in the Lumen Method (Niskier 1992)
and the Philips method of maximum spacing between luminaries (Philips 1997). In the
proposal for the parking area, the number of luminaires and lamps was increased - 258 sets
- but lamps of a lower wattage were used along with a more efficient luminaire - HPL-N
125W and the industrial luminaire HDK E-27 + ZDK 472 for one lamp, with anodized
aluminum reflectors (Philips 1997). On the first floor, a redistribution of luminaires was
proposed, according to the best direction for walking and the sets were replaced by the 32W
TDL RS 32/84 lamps and one-lamp TMS 500 luminaires without reflector (Philips 1997), in a
total of 199 sets. To emphasise the entrances and exits, 9 downlighter luminaires to one PLC 26 W compact fluorescent lamp were used.
3.2
Retrofitting the natural lighting system
Based on the prior analysis, interventions on the ceiling structure are proposed:
• White reflective painting of the ceiling, in order to provide a better natural light
distribution;
• replacement of the clerestory glazing by horizontal louvres on the north and south
orientation, and for vertical louvres on the east and west orientations, in order to block the
direct sunlight and promote the warm air exhaust.
• Redesign of the clerestories adding external and internal curved reflectors in order to
capture and redistribute light internally as shown in Fig.10. The outside reflector is made
of a curved metal structure located in the perimeter of the clerestory in order to collect
and redirect light inwards. The internal structure is composed of a white reflective Ushaped canvas fixed in the top of the clerestories intended to spread reflected light,
redistributing it to the building’s interior.
• The structures created should be regularly cleaned so the system will not loose its
efficiency along the time. In order to do that an easy access to the proposed structures
should be designed.
Fig. 10 – Clerestory redesign
In order to evaluate these proposals, a scale model of the market was built (using materials
and surfaces similar to the real ones). Illuminance levels were measured in the model before
and after the modifications were carried out to compare the results between the two. Both
situations were photographed and are shown below (Figs.11-13)
Internal view of the model
Fig.11
External view of the scale Fig.12
Internal view of the model Fig.13
model of the central market
simulating the real situation of the simulating the proposed lighting
market.
structures for the market.
The natural light measurements showed a mean increase of 25% in the illuminance levels
due to the use of the proposed lighting structures. A new pattern of light was also achieved,
with a better distribution along the internal area.
3.3
Sensors
To optimize even more the use of artificial light in the Central Market a series of light and
occupation sensors were added to the project, along with a dimmer control system that can
set the lamps at complete charge, 50%, 33% and off. 28 sensors were located in the parking
lot, the output of each set of 4 sensors is read by a controller system that is responsible for
the dimming of lamps. Each controller has four basic programs: 1- day function (photocells
on and occupation sensors off); 2- night surveillance mode (occupation sensors on and
photocells off); 3 – events mode (occupation sensors on, photocells off); 4- emergency. The
system can operate automatically but the controllers can be accessed manually in case of
emergency.
The savings obtained by the use of sensors for program 1 – day function, were calculated
based on the estimated frequency of occurrence of external illuminance levels for partly
cloudy sky in Belo Horizonte (ASSIS 1998) as a function of the daylight factors found in the
scale model. For a given external illuminance a mean internal illuminance is calculated for 28
areas which are measured by the sensors and so the percentage of time in which the lamps
are going to be dimmed can be estimated (see Table 1) and the energy savings calculated.
Table 1 – Estimate of energy savings through use of light sensors and lamp dimmers
External illu- Occurrence Internal
illuminance Need of suplementary Lamp
minance level frequency
due to natural lighting artificial lighting
dimming
62%
73%
77%
100%
50 lux
33 lux
25 lux
0 lux
0 lux
17 lux
25 lux
50 lux
100%
66%
50%
0%
Percentage time
of dimming *
62%
11%
4%
23%
*considering a mean period of 8 hours in which daylight is available
For programs 2 and 3, a plan of occupation was assumed and a series of hypotheses tested
in order to estimate the percentage of time in which the lamps should be off.
3.4
Energy savings
Energy savings of 41,4% were obtained in the consumption of energy/month, compared to
the existing illumination system installed at the Central Market, according to the table below.
Table 2
Analysis of the energy consumption (kWh/month) x economy factor
Sector
1st floor
parking lot
TOTAL
4
Existing lighting system
(kWh/month)
13 680,00
10 911,84
24 591,84
Proposed lighting
system (kWh/month)
4 889,70
9 521,70
14 411,40
Energy savings
(kWh/month)
8 790,30
1 390,14
10 180,44
Energy savings
(%)
64,3%
12,7%
41,4%
Conclusions
The lighting of a space is of extreme importance as it gives a variety of information to the
user. A good lighting design should consider not only the levels of lighting but also the levels
of contrast and the quality of the visual information given as a reference and communication
tool. It helps to organize the space in terms of directions, locations and use. This study tried
to cover all of those items, doing so to reach a satisfactory result in terms of energy savings
and visual quality.
The study proposed to retrofit and integrate both the artificial and natural lighting systems of
the Central Market, using concepts and technology of energy efficiency and strategies of light
design based on solar collectors and light distribution. The energy savings of 41,4 % and the
improvement in light quality achieved for the retrofitting of the market common areas, prove
that it’s possible not only to obtain profits in visual quality but also to save energy and turn
the retrofit studies into a profitable business. If the private stores are retrofitted the reductions
in energy use should be even more attractive.
The exploitation of analysis methods to verify the performance of lighting structures using
physical models, showed that besides being a simple to built and to measure the scale
models provide reach visual information that can be evaluated through the use of a
photograph treatment method in order to verify the presence of glare effects or excess and
lack of brightness.
Most of the improvements were achieved could be qualified and quantified through simple
design strategies, easy and cheap to use, that optimize the natural illumination contribution.
The rational circuits distribution and the settlement of a proper maintenance program could
increase even more the illumination system efficiency.
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