Category Archives: BACKGROUND

The artificial sun and sky at Daylighting Laboratory ofthe Politecnico di Torino

Different types of artificial skies have been realised in the past: mirrorskies, dome skies, spotlight sky simulators or scanning skies, each characterised by different advantages and disadvantages7,8,9,10,11,12.

Comparing the potentialities and limits of each type of artificial sky, at the Daylighting Laboratory ofthe Politecnico di Torino it was decided to design and achieve a scanning artificial sky, able to reproduce the diffuse skylight component, supplemented by an artificial sun, able to reproduce direct sun-light component13,14. The facility was conceived not only for research purpose, but also and especially as a tool for designers (architects, engineers, lighting designers) to predict which way daylight characterises outdoor and indoorenvironments, since it allows both determining daylight levels (illuminance and daylight factor values, spatial distribution of daylight over an indoor room) and reproducing how a daylighted environment appears as well as what is the dynamic behaviour of sun penetration.

The “sky” reproduces one sixth of the vault, consisting of 25 individually dimmable luminaires (figure 1), based on the model ofsubdivision ofthe sky hemisphere proposed by Tregenza for sky luminance measurements and assumed by the CIE in the IDMP (International Daylighting Measurement Program)15,16. In orderto reproduce the entire sky dome, the model’s stand produces a six-step scan rotation, modifying foreach scan the luminance distribution. Global photometric quantities and pictures are therefore obtained adding the partial values and images. Different sky conditions are reproducible according to both standard models and real luminance values recorded at IDMP measuring stations. The “Sun” is in a fixed position, so the model’s stand is rotated an tilted to suitably reproduce the relative Sun-Earth position, according to solar geometry equations.

Figure 1 — The scanning sky simulator achieved at the Daylighting Laboratory ofthe Politecnico di Torino

In short, main advantages as tool for daylighting design may be summarised as follows17:

• good adherence with real situations

• possibility of simulating different sky conditions, referring to both standardised daylighting models and real skies, experimentally measured

• possibility of comparing performances of different daylighting systems

• possibility to carry out an objective measurement of photometric data (quantitative evaluation) and a perceptive assessment of the daylighted environment (qualitative evaluation), by taking photographs of the indoorsimulated environment

• possibility of carrying out studies with different aims and on different scales, from site planning to indoor environment to daylighting systems.

Apart from the advantages already listed a scanning artificial sky presents some limits, linked to the finite distance between the model’s stand and the portion of dome: especially when dealing

with large models, an horizon line error and a parallax error (different parts of the considered model receive different quantities ofdaylight and sun-light18) may occur.

Short presentation of the methods Solar volume

The solar volume method determines the maximum possible volume that can be built on a certain site (location) and not cause substantial shadowing of the neighbouring land or buildings. With the help of solar volume we can determine volume or check the existing urban tissue. This way of approach is very important in designing solar urban quarters. It can be easier applied in rural or suburban areas with lower urban densities. In densely built urban centres a shift from the basic ground level could be a sensible solution bearing in mind that ground-floor is usually designed for public or commercial spaces (Fig.1).

The peak of the pyramid is the top of the vertical pole. The north angles of the pyramid are determined on the basis of the shadow cast by the pole, when the sun has the minimum

chosen elevation (in the morning and in the afternoon at the winter solstice). Azimuth can be determined from the solar chart for the chosen latitude. The south edge of the pyramid is determined by the parallel projection of the north edge through the base of the pole. In our case the starting points were two: the15 ° elevation on the 21st of December and the legally required duration of solar exposure.

Summary

The first solar autonomous desiccant cooling system in Germany was proofed to be technical feasible. It is important to reduce the system costs by simple solar systems. A desiccant system with solar air collectors and no buffer storage can cope with the comfort needs of buildings used mainly during day time with a high glazing fraction in the facade.

The users of the chamber of commerce in Freiburg, Germany are satisfied with the comfort conditions in the two conditioned rooms. The approach of accepting some hours of exceeding the criteria of the German standard DIN 1946 part 2 to be able to realise a solar autonomous and economically viable system has been proofed positively.

The detailed analysis of measured data pointed out, that in further projects the amount of regeneration energy given by the collector should be controllable. This means to install devices which allow to reduce an exceed supply of collector gains for avoiding unfavourable heat transfer to the inlet air stream. This could be realised by mixing the heated air with ambient air or by using only part of the collector field if necessary.

The COP of the system is strongly depending on the plant design, the operation constellation and the ambient air conditions. Therefore one has to be careful in comparing this system with other systems.

The direction of rotation is influencing the quality of heat transfer. For the cooling case, the wheels should rotate in opposite directions. For the heating case they should rotate in the same direction. This was not known by the installation company. The direction of rotation will be changed before the next cooling season starts and the effect will be evaluated.

A New Building as a CO2 Sink — Wooden Parish Centre with a Regenerative Energy Supply

Lichtblau Florian, Lichtblau Architects BDA

Competition in 1994: Complex task — parish centre in the heterogenous outskirts of a town. Building design defined in dialogue with the Alpine backdrop.

Planning from 1998: Without access barriers, located in a predominantly natural setting, modular, flexible, pre-fabricated in wood and glass. Immediacy of the structure, materials, artistic design.

Energy, ecology: "Passive" efficiency due to the optimised envelope (heating balance, daylight, airtightness). "Active" technology solely with regenerative energy sources (ground heat source/sink, sunlight, biomass).

Southern aspect, baptismal chapel, northern aspect

Synergetic balance: Maximal comfort for minimal energy (2/3 from environment, 1/3 from wood). Solid wooden construction + regenerative energy = positive CO2 balance for standard costs!

Eco House

The eco house project has been prepared for the architectural competition “Bio-climatic Dwellings” in Tenerife, Canary Islands. The eco house is an ecologically designed cubic dwelling that is 120 m2 and has two stories and a basement. Cubic dimensions of the building optimize heat load because of less surface to build. Building has simple modular plan having axes of (3.20m+1.60m+3.20m). That enables of designer flexibility to set services; kitchen, toilet, bath and circulation in-group as of 1.60m quarter multiples etc. and living dining 3.20m+0.80m multiples.

Entrance, living, dining, kitchen and 2 bedrooms are located to access of South East wind. Greenhouse serves as a tampon area in summer conditions or to collect heat when needed. Greenhouse is at the center of building. Its design eases to conduct desired air to other spaces via direct openings plus special details for conduction. That is living and bedrooms adjacent to greenhouse heat is collected and stored adjacently to the thermally linked spaces.

South region of the Tenerife island is a place, with sunny and arid climate, having large amount of solar energy all the months and with very small temperature swings between the seasons and also between the day and night. Ordinary flat plate photo thermal converters needs can easily supply domestic hot water. The energy for the appliances and lighting for a self-sufficient house can be produced by a stand-alone solar cell modules and battery system. The climate of this region of the island is so suitable that the amount of reserve capacity for the batteries is relatively small as the region being sunny and arid (Green, 1982) and the efficiency decrease due to temperature increase of the Pv cells is also small because of the moderate temperatures and low temperature swings. Temperature increase of the cells can further be reduced by a proper installation taking into account the direction ofthe wind.

Monthly-average solar energy values on horizontal surface are estimated using a quadratic relation between the solar radiation and bright sunshine hours. The universality of this relation was verified by using the measured data of 100 locations all over the world (Akinoglu, and Ecevit, 1990). Diffuse component is calculated using Page’s correlation (Page, 1964).

Solar radiation values on tilted surface are estimated using the procedure outlined in Duffie and Beckman (Duffie, and Beckman, 1991) for the three different tilt angles. Calculations are carried out for all seasons (tilt=latitude), winter (tilt=latitude+12) and summer (tilt=latitude-12) applications and the results showed that the winter application is relatively better for designing the systems, with a minimum value of around 18 MJ/m2 days for the summer months. However, the differences between the monthly radiation values for the all seasons and winter applications are very small. Note that the calculations are carried out for 6 m2 installation and more that the sun according to the year 1995’s conditions can supply 80 % of the load.

Total daily requirement of electricity is obtained to be around 3100 W-hr/day. The reserve capacity of the batteries is assumed to be 3 days, which is quite reasonable for sunny and arid regions having very short rainy and cloudy periods. This gives around 12 lead-acid batteries of 260 A-hr capacity (Roberts, 1991).

The climate of the south region of the Tenerife Island is excellent to build a self-sufficient house. A wise insulation and may be the use of thermal mass walls for some of the rooms might be effective in solving insignificant requirements of cool nights and hot afternoons. According to estimations the total cost of the building is $ 80.500,00 for the year 1995. The materials have been selected with aspect to renewable resources and re-used; materials are mainly brick, wood, volcanic stone and natural insulation.

Toilet solid wastes, kitchen and garden organic wastes, leaves roots are collected, stored and composed to be fertilizer in the edible landscape in and outside house. A specially designed toilet leads urine separately collecting pipe system to be stored in the basement and sold in the market. Pipe equipment set leads gray waters to basement and ponds in the garden to be clarified, re-used and at the end for watering. Detergents waters are used in the same washing cycle. Separated detergent sold to be re-fabricated and re-used. Rainwater collecting from roof, surface waters and well supplies go directly to pond.

For gray water treatment and mix, it is recycled in basement, emerges in cascades into one of the two ponds. Total 400m2 area of garden and greenhouse is supported by homebred fertilizer and water supports %80 of annual consumption of the vegetable, fruit
and white meat of the family. Edible landscape is designed according to their light, water irrigation requirements, aesthetic and creative demands of the people living in the house.

Biogas collection produced by composting process and house unit wind energy is researched for gas production for kitchen and alternative electricity supplement. Wind speed of 5-7 m/s can be used to supply up to 1 kW of energy with a wind turbine having a diameter of 1.5-2.5 m (Randell, Ed., 1988). A rotor type windmill can be installed in the vicinity of the building, which may be attracting due to its easy construction and noise-free operation.

Table 1. Ecological evaluation ofthe buildings and projects

ECOLOGICAL CRITERIA

BUILDINGS & PROJECTS EVALUATION

1

2

3

4

5

6

7

DESIGN

Energy efficiency

kkk

kkk

kkkk

kkkk

irkirk

kkkk

kkk

Renewable energy use

kirk

kkk

kkkk

kkk

kkkk

kkkk

kkk

Flexibility and sustainability in design

kkk

kkk

kkkk

kkkk

kkk

kkk

kkk

Optimization in material use

kkkk

kkkk

kkkk

kkkk

kkk

kkk

kkk

Renovation of existing buildings

kkkk

Structural resistance

kkk

kkkk

kkkk

kkkk

kkkk

kkkk

kkk

MATERIAL

Low embodied energy use

kkkk

kkk

kkkk

kkkk

kkk

kk

kkk

Durable materials

kkk

kkk

kkkk

kkk

kkk

kkk

kkk

Maintenance facility

kkk

kkk

kkk

kkk

kkk

kkk

kkk

To avoid from harmful gas emission materials

kkkk

kkkk

kkkk

kkkk

kkk

kkk

kkk

Use and preference of regional materials

kkkk

kkk

kkkk

kkkk

kkkk

kk

kkk

Preference of recycled materials

kkk

kkk

kkk

kkkk

kk

kk

kk

To utilize waste materials

kkk

kk

kk

kkkk

kk

kk

kk

LAND USE

Minimum automobile use

kkk

kkk

kkkk

kkk

kkk

kk

kk

Development of mix-use functions

kkk

kkk

kkk

kkk

kk

kkk

kk

To utilize the resources in site

kkk

kkk

kkkk

•kkk • kk kkk I kkk kkk • kk

kkkk • kkk kk : kkk kk ; kkk

kkk

kkk

kk

kkk

kkk

kkk

kkk

kkk

kkk

kkk

kkk

kk

kk

To settle the buildings in minimum impact to the environment і ***

kkkk

kkk

To utilize the existing landscape

kkkk

kkkk

kkkk

SYSTEM

EQUIPMENTS

Energy efficient heating and ventilating system

kkk

kkk

kkkk

High efficiency in lighting system

kk

kk : kk

High efficiency in water cycling system

kk

kk ; kk

To provide mechanical ventilation system

— ; **

BUILDINGS:

1. Adobe house in Hasandede

2. Durudeniz dwellings in Mugla

3. Bodrum ikizada Turkcell base Station

4. Straw-bale house in Hasandede.

EVALUATION GRADES: * : Poor

** : Average

*** : Good **** : Excellent

PROJECTS:

5. Bio-climatic house for 5 house-holders,

6. Metropolitan Istanbul Municipality; Headquarter.

7. Ecorenovation in Batikent

Conclusions

SHAPE * MERGEFORMAT

DURUDENIZ

STRAWBALE HOUSE

ECO-RENOVATION

TURKCELL

ADOBE HOUSE

SHAPE * MERGEFORMAT

Figure 1. Ecolagically considered buildings


MUNICIPALITY;

HEADQUARTER

ECO-HOUSE

Figure 2. Ecological projects


Examples of application of the scanning sky simulator

Since 2002, a number of different studies have been carried out at the Daylighting Laboratory, ranging from site planning to single indoorenvironments ordaylighting components analysis.

Most studies carried out in the facility refer to one of the following categories:

— comparison of environmental performances of different daylighting systems (openings, glazed surfaces, shading devices)

— optimisation, during the design stage, of a specific daylighting system.

The different goals of the studies belonging to the two categories imply different procedures in the use of the scanning sky simulator and artificial sun.

Forthe comparative evaluation ofdifferent daylighting systems, models reproducing sample environments are used. Besides, reference conditions are assumed, both forsky conditions and sun positions, and repeated in orderto compare environmental performances due to

assessed systems. At present, for this category, most studies have been carried out to evaluate the performances ofdifferent shading systems (overhangs, vertical fins, Venetian blinds, light-shelves, PVC, wood or aluminium louvered screens) for both residential and non-residential environments (e. g. attics, offices, classrooms, etc.)19,20,21.

The optimisation of a specific daylighting system is carried out during the building design stage and it is related to the distributive and photometric characteristics ofthe space for which the system has been conceived. At present, forthis category, most studies have been carried out to optimise the design of shading systems such as mobile or fixed, matt or specular, continuous or micro-perforated louver shades. Aim of the studies has been concerned with maximising the amount of admitted daylight while screening direct sun­light, hence controlling glare and overheating phenomena and meeting at the same time the Daylight Factorstandard requirements. In these cases, quantitative (illuminance and Daylight Factor levels) and qualitative (images taken inside the scale model) data were collected fordifferent louver tilt angles and for maximum and minimum daylight availability during the year (clear and overcast skies, June and December, morning and noon)22,23.