Assessment of shading devices with integrated PV for efficient

T e c h n i c a l U n i v e r s i t y o f C r e t eD e p a r t m e n t o f E n v i r o n m e n t a l E n g i n e e r i n gLaboratory of Renewable and Sustainable EnergyS y s t e m s

Sitia Development Organization S.A.

Assessment of Shading Devices withintegrated PV for efficient energy useMaria Mandalaki, Konstantinos Zervas, Theocharis Tsoutsos and Alexandros Vazakas

Table of Contents

� Introduction and Purpose of the Assignment

� Case Study Shading Devices

Assumptions of the Case Study Sample Space� Assumptions of the Case Study Sample Space

� Meteorological Data and Climate Area Review

� Methodology

� Results

� Conclusions

Our work at the TUC considers a decentralized energy saving and energy producing system that can be intergraded in buildings and be utilized both by the domestic and business sections.

Introduction and Purpose of the Assignment

� Problem� Main characteristic of Mediterranean Climates

� Mild Winter / Hot Summer

� Intensive Physical Lighting

� Major power Consumption due to Cooling Loads

� A Solution� Use of Shading Devices as a Common Solution

� Balance between Thermal Comfort and Light availability

� Visual Comfort (especially in office buildings)

� Exploitation of R.E.S. (outer shading devices)

The problem that the solution of Shading systems is trying to solve exists mainly in climatic areas such as Greece where …. The most common practice is the use of shading devices and has been used many centuries ago to block the extra radiation from the sun . The need of constructing houses and aiming in controlling the inner environment is indeed very old. Let me remind you the words of the philosopher Socrates recordered by his student xenophon that describes which the best practice for the openings of the houses to be placed south with bigger walls than the north sides so the beneficial winter radiation can enter the inner environment

� Three main types of Shading devices (S.D.)� External S.D. are considered best option, value for money

� Avoids thermal entrapment between the gap (glazing-S.D.)

� Most economical in terms of payback period


� Easy to mount, easy to un-mount (best for offices, do not interfering with the inner working environment)

� Option for embodying R.E.S. (P.V. panels follow electrical demand)

Continuing there are mainly as you can see three types of shading systems but only the outer ones are considered as best option . This is because of three main groups of reasons, Thermodynamically we don’t have entrapment of radiation between the shaders and the glass , A well designed external shading system can give an Architectural meaning in the building façade and more important this can give as the opportunity to integrate reunable energy technologies on the shading systems such as PV panels

� Purpose of the Assignment� Survey design of the best Shading Device for south oriented

façade � Control daylight availability – glare


� Minimize excess heat input during hot period

� Maximize heat input during cold periods

� Transform Solar radiation on usable electrical current

� Creation of a guide for sustainable design of S.D. in environmental friendly buildings through a manual for “best practice guidelines”

The purpose of this assignment is to study the best design of a Shading System that is placed in a south oriented façade that …. The final goal is a guide

Case Study Shading Devices� 13 types of external shading devices compared to a room

without shading protection

� “Machines” of energy production and reduction

In order to evaluate fixed external south facing S.D. according to their energy consuming factor, we examine thirteen types that have been used in office buildings. The S.D.’s are being conceived as machines of energy production and machines of energy reduction, that contribute to the building’s energy balance. The types are

� Every S.D. has been compared to the single window type without shading

� Criteria of evaluation� Cooling and heating loads of inner space

Case Study Shading Devices

� Cooling and heating loads of inner space� Electricity needed to ensure visual comfort� Energy production of P.V. panels

� Factor of Visual Comfort� Ratio of electricity produced by P.V. to the electricity needed for

visual comfort

All this shading devices are considered to be attached to a typical room as we will see in the next illustrations and are compared to the same room without a shading protection but also with themselves There are evaluated by three main criteria and categorized among them by factors such as the

� Simulation has been held for Crete in Chania territory (T.U.C. campus)

� Meteorological data has been used from the Meteorological laboratory of T.U.C.

� Fixed inner yearly temperature range of 18-26 oC .

� Lighting levels of 500 lux for a

Modeling Assumptions

� Lighting levels of 500 lux for a daily period of 08:00 – 20:00.

� Sunlight surfaces of S.D. are covered with PV cells.

� Typical office room dimensions 3.5m x 5.4m x 2.9m.

� Single window facing North (24% of floor area)

� PV cells are considered typical polycrystalline efficiency

� Repetition of the module is taken account (Not to over shade the above stories)

� Thermal loads from surrounding walls were considered invariant

� The only variable of the analysis is the type of the S.D.

� Energy needs (thermal & lighting) are calculated with Energy Plus v3.1

� Lighting Levels and PV production are calculated with Autodesk Ecotect v5.6

Modeling Assumptions

Meteorological Data & Climate Review°C

30

40

50

°C

30

40

50

Dry bulb temperature,(°C

)

Relative humidity, (%)

Direct Solar radiation(W/m²)

Wind Speed, (m/s) Wind Direction Cloud Cover Rain

Estimation of internal

temperature

Wk

Hr

48

1216

2024

2832

3640

4448

52

4

8

12

16

20

24

0

10

20

30

Wk

Hr

48

1216

2024

2832

3640

4448

52

4

8

12

16

20

24

0

10

20

30

Methodology

� Form’s of S.D. were taken from Literature Review.

� Dimensions of every S.D. were calculated by minimizing the Summer Irradiation and maximizing Winter irradiation.

� Modeling in Ecotect – EnergyPlus incorporating weather data

� Extracting results and develop useful conclusions

Results

The positive lighting independence factor means that for these S.D. the electricity production is sufficient for supporting the electric light needed. It is important to note that, even if the SD of horizontal louvers has a very good performance in terms of electricity production through its integrated PV, it has negative lighting independence factor, due to the fact that reduction of the daylight is much higher than almost all the other SD. One could provide this spare energy for lighting into the inner common spaces. The three more darkening SD are: horizontal louvers outwards inclined, the horizontal louvers and the surrounding shading. It is important to note that the electricity produced by each device is not relevant to the surface of the PV installed in the system. That is happening due to the geometry of each shading device and the position of each PV panel according to this geometry, that allows the overshadowing between the elements.

Results

KWh/m2

Results

Conclusions

� Best for a bioclimatic approach

� Minimum electricity generation for light needs

� Best for a Renewable energy application approach

� Less efficient in thermal needs

T e c h n i c a l U n i v e r s i t y o f C r e t eD e p a r t m e n t o f E n v i r o n m e n t a l E n g i n e e r i n gLaboratory of Renewable and Sustainable EnergyS y s t e m s

Sitia Development Organization S.A.

Thank you for your attention

Konstantinos Zervas – Environmental engineer, MSc Energy [email protected]

Assessment of shading devices with integrated PV for efficient

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