Category Archives: EuroSun2008-4

Portuguese Methodology — SolTerm programme

The calculation methodology adopted in SolTerm, considers all solar thermal systems as pre-heat systems.

Подпись: Fig.2 - Schematic representation of a Thermal Solar System in SolTerm (adapted from [2]).

Simple schematic representation of the solar thermal system considered in SolTerm is given in Fig.2:

The main components of the system are:

• solar thermal collector characterized by the parameters: collector aperture area, zero-loss efficiency, heat loss coefficients determined according to EN 12975-2; section 6.1 (steady — state efficiency tests) [7]. The collector area is implemented by multiples of one collector and a data base of certified solar thermal collectors is integrated in the programme although the user can edit its own collector characteristics.

• collector loop including possibility to calculate pipe heat looses and efficiency of heat exchanger

• storage tank, characterized by its volume and heat losses coefficient

The energy delivered by the solar thermal system is a function of climate (climatic data base is included in the software tool) and by the load profile. A hourly load profile can be defined, as well as, week and week-end days and monthly load profiles.

The algorithm used, performs calculations in a simulation basis of the system behaviour in time steps on 10 min. Stratification of the storage tank is considered using an approach similar to the

one described in [6; chapter 8]. Transient behaviour of the system is not considered. The result of one simulation allows for the determination of:

a) monthly values of heat demand, i. e., Qsol, us, m, (calculated according to the load profile defined) where definition of load temperature and cold water temperature is included.

b) monthly values of energy delivered by the solar thermal system, i. e., Qsol, out, m The SolTerm version 5.0 was used in the comparison.

For comparison between the two methodologies, fixed values and procedures where adopted in SolTerm calculations in order to have input values as comparable as possible with the methodologie of EN 15316-part 4-3.

Since SolTerm allows for variations in Load profiles the option was to consider the same load profile seven days of the week with only one extraction between 17-18h.

Passive-On project

1.1 Passivhaus standard

The standard Passivhaus was first defined by the Passivhaus Institut in the early nineties. It describes a highly insulated house with extremely low energy consumption for heating and controlled mechanical ventilation with a heat recovery to make the building air tight, to guarantee

Information and publication

The task is about midway in the progress, and most of the expected outcome has still to be developed.

However, some information is already available at the task web-site: www. iea-shc. org/task37

• Task 37 flyer

• The exemplary housing renovation brochures

With financial support from the Enova and the State Housing Bank in Norway, a set of films about housing renovation have been produced:

These films which are also available in Norwegian and German, are expected to be available from the task 37 web-site before the start of EuroSun 2008.

Other reports which are expected during this and next year:

• Housing segments with the greatest multiplication and energy saving potentials.

• Business Opportunities in Advanced Renovation

• Packages of technically and economically robust concepts for housing renovation which could be applied in concrete projects.

• Innovative future solutions with great potential of primary energy reduction.

• A “basics” on sustainable renovation including principles for the design and realisation of renovation projects.

Remarks on Winter Shading Strategy and Human Intervention

The results derived from building simulations, of window shading profiles in winter, indicate that if shutters remain closed on the North West orientated fenestration, the reduction of solar gains and consequently the drop of indoor temperature is insignificant (0.1 to 0.2 deg. Celsius Table 1, 1.0,

1.1, 1.2). This is mainly attributed to:

i) Area — The window area on North and West sides is limited.

ii) Orientation-There is no direct solar incidence on these facades.

However if South facing glazing is left shaded, in winter, the solar losses are considerable; an area of 10% of shaded South orientated windows causes a reduction of indoor temperature by 2.0 degrees Celsius and reaches 10.0 degrees reduction as the shaded window area increases. The reduction is attributed to the large amounts of solar gains received by fenestration on this orientation, due to the low solar path and the small angles of incidence. This results to rapid

deviation of indoor temperature from comfort levels (Tables 1, 1.3 and 1.4). When all windows are left closed the indoor temperature drops below outdoor temperature (Table 1, 1.4).

The above results emphasise the sensitivity of the manually operated shading devices and the associated uncertainties which could hinder the successful performance of the design of the “Zero Energy House”.

Table 1: Shading ^ fenestration profiles for winter and effect on indoor temperature

No. Profile

WINDOW SHUTTERS

INDOOR TEMPERATURE °C

Orientation

Area(m2)

Strategy

Average T

Ave. Deviation*

Deviation

WINTER DAY BETWEEN 07.00-19.00 HOURS

1.0

South

35.00

Open

All Unshaded

West

0.50

Open

19.70

BASE

0.0 — 0.0

North

3.50

Open

Winter Optimal

1.1

South

35.00

Open

Shaded North

West

0.50

Open

19.55

— 0.15

0.1 — 0.2

North

3.50

Closed

1.2

South

35.00

Open

Shaded N-W

West

0.50

Closed

19.50

— 0.20

0.2 — 0.3

North

3.50

Closed

1.3

South

17.50

Open

Shaded NWS

South

17.50

Closed

1/2

West

0.50

Closed

14.96

— 4.74

4.3 — 5.2

North

3.50

Closed

1.4

South

35.00

Closed

All Shaded

West

0.50

Closed

10.03

— 9.67

8.9 — 10.5

North

3.50

Closed

* Deviation: Deviation from BASE Winter Optimal Indoor Temperature of “Zero Energy House” — : Indicates decrease of Temperature from BASE

Energy produced by the PV systems versus energy consumed

From 1st February 2006 until 31 July 2008, the daily average electrical energy delivered to the grid by the PV systems was 53.7 kWh, corresponding to 23.6 kWh produced in the park and to 30.0 kWh produced in the fagade, Table 8.

The average daily consumption of the Solar XXI building was of 74.6 kWh and the contribution of both PV systems to satisfy this consumption was about 72 %.

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Ago 08

Подпись: 1st International Congress on Heating, Cooling, and Buildings, 7th to 10th October, Lisbon - Portugal /
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Table 8. Daily averages values of the energy produced by PV systems and consumed in the building.

2. Conclusion

The monitoring data of the two PV systems installed at Solar XXI building, shows very good performances. The daily average electrical energy delivered to the grid by the PV systems was 53.7 kWh, corresponding to 23.6 kWh produced by the amorphous silicon modules installed in the park and to 30.0 kWh produced by the multicrystalline modules in the fagade.

The measured average daily consumption of the Solar XXI building was of 74.6 kWh and the contribution of both PV systems to satisfy this consumption was about 72 %.

References

[ 1] A. Joyce, C. Rodrigues, R. Manso, 2001, “Modelling a PV System”, Renewable Energy 22, 275-280, Pergamon, Australia

[ 2] H. Gongalves, A. Silva, A. Ramalho, C. Rodrigues, 2008, “Thermal performance of a passive solar office building in Portugal”, EuroSun2008, Lisbon

[ 3] C. Rodrigues, 1997, “Dimensionamento de Sistemas Fotovoltaicos Autonomos”, master thesis Mechanical Eng., Institute Superior Tecnico, Lisbon

Implementing A New Method For The Design. Of Bioclimatic Buildings

Joao Mariz Graga1, Joao Bento2 and Helder Gonsalves1

1 INETI — Instituto National de Engenharia, Tecnologia e Inovagao;
Estrada do Pago do Lumiar, 22, 1649-038 Lisboa
2 Instituto Superior Tecnico,

Av. Rovisco Pais, 1049-001 Lisboa

A tool for support the design of bioclimatic buildings is under development. This tool is also specialy adapted to the particular needs of buildings in the portuguese territory, since it includes the possibility of doing evaluations according to the requirements that are imposed by the new regulations of thermal performance for buildings (RCCTE). This tool will allow designers of bioclimatic architecture to easily extract reports of different energy simulation programs, such as energy Plus, Radiance and RCCTE thermal code. The system is provided with a 3D Editor that shares multiple interfaces with the different simulation programs above mencioned.

A particular method for the conception of bioclimatic architecture is assumed, however different types of evaluations can be performed with this interface program.

A particular method for the conception of bioclimatic buildings is here sugested. It begans with the evaluation of the complience with the portuguese thermal codes. Once the shape and construction for the building under design are conformant with regulations, other evaluations are sugested. The system provides the possibility of automaticaly generate a geometric definition for future energy plus simulation that maches the previous RCCTE definition, however with some simplification assumptions. This can bring closer the evaluations of the thermal code requirements with the energy Plus evaluations, and so to take advantage of a large number of energy plus features in a detailed analysis.

The program under development provides automatic generation of some particular features of Energy Plus that were found very usefull for design tasks of bioclimatic buildings, such as the generation of; adjacent zones, trombe walls zones, earth tubes, detailed window variables, etc.

Future Development

Up until now solar thermal cooling plants have been assembled on site. This requires highly trained installers and construction supervision, and is therefore both complicated and expensive. In order to reduce the construction period and the risk of mistakes, we have developed pre-fabricated units. The various components including the solar unit, cooling machine, pumps and valves, the control unit and the cold water buffer tank are all pre-assembled in a container.

The first such container was used for a project in Phoenix. These cabins are initially to be designed for projects requiring 15KW — 200KW of cooling power.

/This EnergyCabin is portable and therefore perfectly suited for contracting and leasing, even for projects abroad. The solar collectors for exclusively cooling applications are mounted close to the cabin.

Solar availability for rooms at attics

For the purpose of the presented studies, calculations of solar radiation incident on surfaces with different azimuth and inclination angles have been performed using the averaged representative hourly solar radiation data for Warsaw [3] for the anisotropic sky model, Hay — Davies — Klucher — Reindl [5]. To describe and solve problems of the dynamics of processes in the building envelope and surrounding, a mathematical model of energy transfer phenomena in opaque and transparent elements has been developed [1], [2]. Focus has been put on the influence of solar energy and because of that, special attention has been paid to energy transfer through the windows.

Window consists of three main components: centre glass area, edges of glass, frame. All these 3 components influence on each other from the point of view of the heat transfer [4]. The model of unsteady energy transfer outside and inside the window, as well as within the cavity formed by the glass sheets has been developed [1]. It includes heat conduction and heat capacity of opaque (frame) and transparent (centre glass area, edge of glass) elements. It also includes heat convection (free) with indoor and (forced) outdoor surrounding and inside window cavity; and radiation (thermal — long wave) exchange between the ground, the sky, i. e. the outdoor environment, and windows; and radiation exchange between windows and the room cavity, i. e. indoor environment; and radiation exchange between glass panes of the window.

Solar radiation incident on surfaces with different orientation and inclination is considered in details. Window constitutes three dimensional object. Solar irradiance on glazing and front surfaces of the frame is the same at given time but it differs for frame surfaces perpendicular to glazing (that have not only different orientation but inclination, too). The developed model takes into account all these phenomena and solar absorption at frame surfaces. Solar absorption, transmission and reflection of all transparent surfaces (bodies) are analysed, and the effects of orientation and inclination on them are considered.

The developed model enables to calculate energy transferred through the window into/out of the room at any time. These energy transfer takes into account not only heat transfer because of temperature difference between indoor and outdoor environment, and specific conditions at boundary surfaces (including absorption of solar energy), but also solar energy transferred directly into the room under consideration. The results of calculations of energy transferred through the some selected examples of windows throughout the averaged year are presented in Fig. 1-4. Figures 1-2 show the case of inclined (450) small (1 x 1 m2) and big (2 x 2 m2) south windows respectively and Figures 3-4 show the case of inclined (450) small (1 x 1 m2) and big (2 x 2 m2) north windows respectively. The opposite orientation (south and north) and different size of windows have been selected to show the influence of orientation and size of a window, and in consequence the influence of solar energy, on energy transferred through the window. For the south orientation the maximum hourly solar radiation that enters the room through a window is at noon in May and for the small window it is about 1,15 MJ for 1 m2 (of the window) and for the big window it is about 5,1 MJ for 4 m2 (of the window). The minimum is in December and for the small window at noon it is about 0,25 MJ for 1 m2 (of the window) and for the big window it is about 1,1 MJ for 4 m2 (of the window). For the north orientation the maximum hourly solar radiation that enters the room through a window is at noon in June and for the small window it is about 0,57 MJ for 1 m2 (of the window) and for the big window is about 2,6 MJ for 4 m2 (of the window). The minimum hourly solar radiation that enters the room through a window at noon is in December and for the small window is about 0,11 MJ for 1 m2 (of the window) and for the big window is about 0,5 MJ for 4 m2 (of the window). Generally hourly solar radiation entering the south room is about two times bigger than for the north room. It can be seen that the increase of size of the window cause the increase of energy flow through a window but not exactly proportional.

x io5 Solar heat through window, with Beta = 45, Gamma = 0 Xt = 1Yt = 1

image382

 

image383

Jan

—— Feb

Mar

Apr

May

Jun

Jul

— Aug

— Sep Oct

— Nov

— Dec

 

x io5 Solar heat through window, with Beta = 45, Gamma = 180, Xt = 1, Yt = 1

image384

Fig. 3. Solar energy transferred into the room through the north inclined (450) small window

 

Подпись: Q (J)Подпись:Подпись: t (h)image388—— Jan

—— Feb

—— Mar

Apr May Jun

— Jul Aug

— Sep Oct Nov

— Dec

Thermal Performance of Residential Buildings in Lisbon. with Large Glazing Areas

M. Tavares H. Gonsalves1 and J. Bastos2

1 INETI, Department of Renewable Energies, Campus do Lumiar do INETI, 1649-038 Lisbon, Portugal
2 FA-UTL, Department Technology of Architecture, Polo Alto da Ajuda, 1349-055 Lisbon, Portugal
^Corresponding Author, marcia. tavares @ineti. pt

Abstract

This work presents the results of an experimental study of residential buildings (multi-family apartments) with glazing areas greater than 75% of the total facade area, and for different solar exposures in Lisbon. These buildings were designed after the implementation of the first Portuguese Buildings Thermal Regulation and they are intrinsically related with the construction and architecture practiced in the last few years. The analysis includes the thermal behaviour of the apartments selected for the study during the summer (2007) and winter (2007-2008). During the monitoring process important data were obtained to assist in the understanding of the thermal performance of the observed units. The main thermal exchanges in a building generally take place through the transparent elements and these can be considered an element of great flexibility and adaptation to climatic variations. The mean of the interior temperature means in the different monitored compartments during the hot season was approximately 27°C (some cases close to 29°C), while in the cold season 21°C (some cases close to 18°C).

Keywords: Glazing areas, thermal behaviour, heating, cooling, thermal comfort

1. Introduction

The energetic optimization reveals how important is the building envelope, as the main element between the exterior and interior conditions. The conduction and convection transfers through glass present a similar behaviour of the opaque elements with the possibility of the air change control between the interior and exterior — opening or closing the windows. Meanwhile, radiation becomes the principal factor because its portion is transmitted directly through the glass to the interior.

The non-opaque envelope can be considered an element of great importance in the control of radiation, ventilation and natural illumination. A more dynamic element, easier to adapt and adjust to obtain the desired interior conditions, in other words, it presents a comparatively greater degree of adaptation control and flexibility to the climatic variations than the opaque envelope. In addition, glass and other transparent materials are essential elements for the successful application of the majority of the passive solar heating systems. The heat transfers occur differently depending on the types of materials and proportions being applied in a specific building (opaque and non­opaque envelope).

Solar Power Station

At the start of the project the goal was to design a PV powered bilge pump for open boats. Already in the beginning of the project it was concluded that a multifunctional product would have more market potential. This resulted in the design of the Solar Power Station as a product that can keep valuable and vulnerable products dry, and that can provide energy to a range of electric devices such a a water pump, cell phone, GPS device, and a weather station that is integrated in the product. The Solar Power Station charges it battery via the PV panel. The PV panel can be placed separate from the station, on a location where it can convert energy optimally. Also can the panel be tilted towards the sun. The devices can be connected via 12V sockets and USB sockets. The product was developed up to a prototype. The company the product was developed for announced that it is planning to produce a small series of the product.

image466

Fig. 9. Solar Power Station prototype with tilted PV panel