1.1. PERENE and the solar factor of glazing

Rules of thumbs exist for the thermal design of building in the French tropical island of La Reunion. The name of this programme is PERENE — French acronym for ENErgy PERformances of buildings, but the PERENE programme focuses on the design of the envelope and the energy efficiency of active systems [1] Concerning the glazing solar protections, some requirements give the levels of performance of solar protections to be reached in term of solar factor for different orientations and different climatic zones (see Table 1). Zones Z1 and Z2 are respectively the upwind and downwind coastal zones. Zones Z3 and Z4 are respectively the Highlands zone (altitude between 400 and 800m) and the altitude zone (altitude above 800m). The requirements only concern an overhang-type shading.

As for the daylighting requirements in Reunion Island, the only document which deals with this point is the adaptation in the French overseas territories of the target "visual comfort" for High Environmental Quality standards [2] The document sets requirements in terms of daylight autonomy function of the level of performance of the target required.

Some papers of course deals with the problem of daylighting in buildings, but only few gives requirements for the high solar radiations of tropical climates. The studies mainly focused on moderate climates and use methods of calculation that ar not appropriate to Reunion Island.[3], [4].

The position of the sun has been simulated along the whole year in order to evaluate its influence and project actions to avoid heating during the summer and to favour solar exposure during the winter.

This will be of special interest for rooms of general used, which will thus be facing South. Figure 3 shows the trajectory of the sun for all months, referred to the concrete location of the building. The aim is to avoid shadowing by surrounding buildings.

2.1. Insulation

The process of thermal energy transmission in a building of these features takes place mainly by radiation process (75%), but also involves residual conduction and convection (25%). Therefore, any type of building insulation project should be designed mainly to impede the radiative thermal energy flux, but it should also account for residual conductive processes. This way, reflective insulation appears as the most adequate and efficient technique, provided very high output due to high reflective power and to the specific structure for the retention of air bubbles.

The results achieved by reflective insulation (versus traditional methods) are quite significant. Figure 4 shows the thermal resistance for several types of insulation (values of thickness between 1-10 cm, with 5 mm step interval).

Reflective insulation presents a flat curve from a concrete value of the air chamber thickness, and efficiency is not improved for higher values. However, thermal resistance is significantly higher than that of a conventional insulating material. In sum, this feature favours the optimisation of useful interior space.

Let us describe as an example the insulation pattern projected for both South and West facades of PETER building, following the actual order of the insulating coatings:

• Marble shield (model Frontek de Venatto), 2 cm thick.

• Low-emissive air chamber (4 cm).

• 4 mm Superpolynum reflective insulator, with intrinsic resistance 0.11 m2 K W"1.

• Structural panel (12 mm).

• Natural fibre insulator (25 mm).

• Low-emissive air chamber (2 cm).

• 4 mm Superpolynum reflective insulator, with intrinsic resistance 0.11 m2 K W"1.

• Low-emissive air chamber (4 cm).

• Laminated plaster sheet (15 mm).

The total transmission coefficient of this type of wall is U=0.31 W / m2 K.

The next step is the comparison of the thermal conductivity parameters with those of the TBC, DB — HE 1, which indicates the maximum limitation of the energy demand of a building, considering maximum required transmittance according to the type of walled enclosure and to the climatic zone of the location of the building. Taking this aspect into account, a detailed analysis of the energy demand shows energy savings over 69% in winter and over 86% in summer with respect to the values stated by the TBC (see Table 1).

*

Such a reduction of the energy demand will lead to lower power in the heating and the acclimatisation systems. Besides, if renewable energy devices were installed, then fossil fuels or conventional energy sources would not be required. The use of those devices would not only result in environmental benefits, but also in notable economic savings.

C. Rodrigues, S. Viana, A. Joyce, H. Gonsalves, A. Silva

INETI, Department of Renewable Energies, Estrada do Pago do Lumiar, 1649-038 Lisboa, Portugal

Corresponding Author, carlos. rodrigues@ineti. pt

Abstract

The purpose of this paper is to present the results obtained in the first two years of operation of the grid-connected photovoltaic (PV) systems installed in the named “Solar XXI” building. One PV system, made with multicrystalline silicon modules, has a peak power of 12 kW and was installed on the fagade; another system made with amorphous silicon modules has a peak power of 6 kW and was installed in the surrounding park area near the building.

From 1st February 2006 until 31 July 2008, the measured daily average, of the building electrical energy consumption, was about 75 kWh and the two PV systems produced in average about 72 % of this energy. The averaged measured Performance Ratio of the systems was about 0.84 for the PV Fagade and about 0.76 for the PV in the Park.

Keywords: BIPV, Grid Connected PV systems, PV micro-generation

1. Introduction

The Portuguese commitment for electricity production from renewables, in the framework of the EU Directive 2001/77/EC, was that 39 % of all the electricity consumed in Portugal in 2010 should come from renewable energy sources. However in 2007 the Portuguese government decided a new objective of 45 % of renewable electricity in 2010.

Until the end of 2007, Portugal had an estimated installed PV capacity of about 17.4 MW, resulting from the start up of the new power plant at Serpa, with 11 MW, and of other plants of the order of 1 or 2 MW, witch gave rise to a jump in the installed PV capacity in the last year.

It is expected that in the next few years new jumps will appear due to power plants already announced mainly the one related to the big power plant of Moura with a final installed capacity of 46.41 MWp, which already started, and also the ones to be installed at several places in the South of Portugal and a 6 MWp power plant at the distribution market MARL near by Lisbon.

Recent legislation in Portugal related to energy production from renewable energy sources, namely Decree Laws 225/2007 and 363/2007, have provided the framework for the development of Building Integrated Photovoltaics (BIPV) in the electricity domestic market with a feed in tariff dependent of the integration of solar thermal solutions.

The PV market in Portugal is still dominated by the objective, which was stated for 2010, of 150 MW for PV conventional centrals plus 50 MW for BIPV (DL 225/2007). This market is almost completely filled and no new licences are being attributed for centrals or BIPV, putting a cap to the market growth.

The new law for micro-production (DL 363/2007) which started to be implemented this April, is supposed to contribute with about 10 MW of new PV capacity installed each year and until now it is well accepted by the consumers of electricity, stimulating the domestic production of electricity.

In this context the new “Solar XXI” building pretend to be, an example of low energy consumption for new buildings and simultaneously it is, an experimental facility of INETIs Renewable Energy Department.

The building and the surrounding car park, integrate two Photovoltaic grid connected systems: a 12 kWp system installed on the south vertical facade of the building with a heat recovering system in the back of the photovoltaic modules used to heat the offices of the south side of the building, and a 6 kWp system installed in the car park area as a shading device. The PV systems are part of a demonstration project, supported by the Portuguese PRIME Program. The building is an energy efficient building optimizing geographic orientation and natural lighting with integration of both passive and active solar thermal solutions, see also Gonsalves et al [ 2].

The purpose of this paper is to present the results obtained in the first two years of operation of the installed PV systems in terms of performance yields and contribution, of the energy produced, to the electrical energy needs of the building. We will present the results obtained for the two PV technologies used, amorphous silicon in the park and multicrystalline silicon on the facade, and the observed seasonal variations in performance, due mainly to temperature effects.

Building thermal regulations enforce different insulation levels all over Europe according to the severity of the climate. There is nevertheless a tendency towards more stringent levels in particular due to the EPBD in action and its expected second version.

Good insulation of walls and roof limits the heat losses in winter and increases the interior surface temperatures, minimizing the risk of interstitial condensations and improving thermal comfort of the occupants. During hot periods in summer, insulation may be beneficial at reducing the heat flow from the outside to the inside in particular due to solar radiation incident on the surface and high external temperatures. Conversely, high levels of insulation are disadvantageous at dissipating internal gains, and other passive cooling strategies, such as ventilation, may be advised.

Heat transfer in the walls and roof is generally higher than via the ground due to a higher temperature difference between the space and the outside, whereas the ground temperature is milder. Insulation levels are therefore much more important at surfaces in contact with the exterior. Interior walls (in contact with other spaces not heated/cooled) require less insulation.

3.4 Thermal bridges

On highly insulated buildings the effect of thermal bridges may be aggravated when the insulating layer is interrupted. A special concern is made in the Passivhaus to avoid significant heterogeneities on the envelope that can result in thermal bridges. Those usually occur in corners, edges and joints. External insulation can minimize thermal bridges by creating a continuous layer.

It also enables the building to maintain its inertia on the construction walls and ceilings.

1.3. Weather Data

The model developed was implemented as a TRNSYS [11] component. It was then simulated for one year using the typical meteorological year (TMY) weather data and the Perez sky model for diffuse radiation for the three following Canadian cities: Yellowknife, Montreal and Iqaluit. From the cities climate information presented in Table 1, it can be observed that Yellowknife and Iqaluit have similar solar radiation potential than Montreal for south-facing vertical installation even though their global annual daily horizontal radiation is much lower. This can be explained by the cities high northern latitude and thus, lower sun angle throughout the year.

4.1. House 1: Cushamen.

• Geographic location: Latitude: 42°03’.157, Longitude: 71°10’.112, Height: 734,30m above sea level.

• Technical Data Card: — Project date: 1st of November of 2005; — Construction State: Concluded Work, December 2006.

• Architectural Response: It responds to a two-bedroomed unifamiliar house, with a covered surface of 95 m2 plus 8 m2 of greenhouse (total = 103 m2). It is synthesized on one floor with bedrooms, gallery and greenhouse to the North- for greater reception and collection of solar radiation — and with the service premises to the South as “stopper” spaces (Figure 5).

[1] Background

Helmut F. O. Muller1*, Jorg Schlenger1, Andreas PreiBler1, Heinrich Muller2, David Fiedler2

1 Chair of Environmental Architecture, Department of Architecture and Civil Engineering, Baroper Str. 301

2 Chair of Computer Graphics, Otto-Hahn-Str. 16,

Dortmund University of Technology, D-44227 Dortmund, Germany
Corresponding Author, helmut. mueller@tu-dortmund. de

Abstract

This paper describes a building energy evaluation method developed by the named chairs in co­operation with the Chair of Building Process Management, Dortmund University of Technology, in 2007-08. The method aims at an energy assessment of fa? ades of public office buildings in Germany. The evaluation aspect of energy considers the overall energy demand in reference to the EU directive 2002/91/EG as well as embodied energy and Global Warming Potential (GWP) of the building elements used. The aspect of energy, being dealt with in this paper, is integrated in a comprehensive assessment system covering economy as well. The basis of the energy assessment is a dynamic energy simulation with the computer program TRNSYS, applied for a defined room with four fa? ade orientations. The user of the assesemnt system has a quick and simple access to the results of the TRNSYS simulations by an EXCEL-Tool.

The fa? ade systems, which vary from convetional load bearing external walls to high-tech curtain walls, are classified by a “morphological box”; a table with 23 parameters and up to 6 options per parameter. The design parameters under consideration include shape, dimensions, material, construction, and functional properties of fa? ades. For the TRNSYS simulations the morphological varity of the fa? ade systems was reduced to a manageable number of 6 physical parameters, relevant for energetical properties. Each of these parameters was varied by five equidistant steps within an appropriate bandwidth.

The EXCEL based tool gives access to the overall primary energy demand index for a number of 150,625 possible fa? ade variations. Additionally there was developed a free choice of interpolation for properties by regession analysis. Thus an unbounded design variety can be evaluated quickly, based on a limited number of elaborate simulations. The main influences of fa? ade design on overall primary energy demand can be derived. Thus the energy assessment can be used for comparison as well as for optimization.

Keywords: assessment, energy, fa? ade, evaluation

1. Introduction

The method was developed as a framework for a specific assessment system to be used by a German federal institution in early design stages [1]. Various types of fa? ades for both new office buildings and renovated ones had to be included in this project. The assessment tool gives no absolute energy and cost values but specific indices for a relative comparison only.

The fa? ade technology considered varies from conventional load bearing external walls with window openings to high-tech curtain walls for high-rise buildings, fulfilling a performance spectrum from minimum building standards to high quality and low energy solutions. The evaluation aspect of energy performance is considered by an overall energy demand for heating, cooling, ventilation and lighting with reference to the EU directive 2002/91/EG as well as embodied energy of the fa? ades and Global Warming Potential (GWP) of the building elements used.

Since the heating energy criteria is not met in most of the apartments, a new round of upgrade measures is necessary to achieve compliance. Table 7 shows the upgrade measures considered in each of the apartments in order to try to achieve the compliance. Table 8 shows the results after this new round of constructive changes. The results show that all apartments now fall within energy class B.

This clearly shows that the compliance with the energy requirements of the RCCTE is possible without interfering with the architectural appearance of the building and even without solar thermal collectors for domestic water heating.

The Energy Matching Model describes the elements of the energy chain of a PV powered product. The purpose of this model is to optimize the matching between these elements. The main elements of the Energy Matching Model, depicted in figure 2, are: a) user context defined incident light, b) PV power converter, c) electrical energy storage media, d) energy use in the functional product application and e) user context defined power/energy use pattern of the product.

Through so called matching interfaces (MI 1-3) the elements in the energy chain interface with each other. In addition to these interfaces, the overall energy balance also has to be analysed. The feedback-loop through the overall application matching interface (OMI) is closed by two overall energy balance tracks.

To evaluate, quantify and predict to what extent the matching between the elements is actually achieved the Figure of Matching algorithm is developed. This is a combination of the stimulus — response concept and the correlation concept. The Figure of Matching algorithm is illustrated in figure 3.

According to Kan [2] the Energy Matching Model and the Figure of Matching have to be used as essential tools in each design phase to create successful PV powered products.

• Geographic location: Latitude: 43°27’.085, Longitude 70°15’.325, Height: 1048, 30m above sea level.

• Technical Data Card: — Project Start Date: 10th of January of 2007; — Construction State: Final stage of construction.

• Architectural Response: The prototype responds to a one-floored unfamiliar house. It possesses a multifunctional space — for sleeping and living-, bathroom and kitchen. Its surface is 22.12 m2 plus 11.20 m2 of greenhouse; total of 33.32 m2. It is north-oriented for greater solar profit by means of a greenhouse incorporated to the functional development of the house and it faces these spaces, which they overflow (Figure 11).

• Construction modality: since the addressee is an elderly person, manual labor from the programme was chosen to support self-production of the house.

• Walls, Roof and Floor: Traditional construction techniques were recovered and material and human resources from the area and few industrialized materials were employed. a) Wall: Masonry of champa de mallm (compact block of earth from the region) of 0,30 m of exterior thickness and of 0,15 m interior; “in situ” units of extraction; of: 0,30 m x 0,40 m x 0,12 m or 0,15 m x 0,40 m x 0,12 m settled on mud; superficial masonry finish of unfurled metal and plastering with water repellent cement, thick and fine; Carpentry: Wooden doors and windows; b) Ceiling: Wooden structure, matched wood ceiling with water repellent insulation — with tarred paper — and thermal insulation — with glass wool — and cover of zinc sheet metal (Figure 12); c) Floor: Flagstone on slab foundation of stone.

• Energetic and Environmental Conditioning Systems:

A) Solar systems to (Figure 13):

— Passive heating: solar gain is direct by means of heat-sealed double-glazed windows — and of the greenhouse.

— Storing: Most heat accumulation is achieved in the exterior and interior champa de mallm.

— Hot water: the system of sanitary water heating counts on a commercial collector of 1 m2 and an isolated accumulator water tank of 50 litres which feeds the bathroom and kitchen artefacts.

— Greenhouse: the system permits the production of fruit and vegetables; it possesses a polycarbonate sloped closure which acts as a ceiling lateral closure to the North.

B) Wind-powered systems: power obtainment -12 volts, continuous current — is done by means of a wind-powered generator of 600 w.

C) Conventional heating and cooking: a high performance sheet metal oven was installed — “Nuque Oven”- for cooking and heating.