In order to calculate the total solar energy transmittance (g-value) [5], the secondary heat flux Is must be calculated. The thermal simulation program HEAT2 was used to estimate the heat flow into the room caused by the absorption on the back of the reflective layer and in the glass itself. It was assumed that the glass bars were positioned 1 mm from the outer glass pane. The bars themselves had a diameter of 10 mm, and the distance from the bars to the inner glass pane was 12 mm.

With the secondary heat flux Isec heat, the direct and diffuse intensities (Isec dir, Isec diff) and the incident global radiation Ig given, it is possible to compute the g-value:

Fig. 7 g-value of the system (в = 90°) for days with Idir = 0 (cloudy) and Idjr > 300 W/m2

(sunny).

The g-value was also estimated for the tilted system, with a slope of 30° (Fig. 8). One can see that the g-value for cloudy weather increases slightly while the one for sunny weather decreases. The latter comes from the fact that, especially in summer when radiation is strongest, we don’t get multiple reflections and so the absorptance on the darkened side remains small. This effect will be more pronounced for the secondary heat flow in this case.

As mentioned before (see Fig.4) a considerable part of the direct radiation is absorbed on the blackened side of the reflective layer. This will lead to a secondary heat flux into the room. In order to get a feeling for how much of the g-value is radiation that can be used for illumination and how much is heat radiation depending on the absorbed power, the amount of heat flowing into the room was computed with HEAT2. Figure 9 shows that even for the в = 0 case in summer the maximum heat flux into the room does not exceed 80 W/m2. For the tilted case (в = 30°) the secondary heat flow is even smaller (Fig.10).

40.0

30.0

20.0

10.0

0.0

0 730 1460 2190 2920 3650 4380 5110 5840 6570 7300 8030 8760

Time [h]

Fig. 10 Secondary heat flow into the room arising from the absorption on the blackened
side of the reflective layer, tilted case (в = 30°).

The percentile contribution of the secondary heat flux and the visible diffuse radiation to the g-value is plotted in Figure 10 for the vertical case. As one can see, the secondary heat flux Isec heat contributes only about 30 % to the total g-value, whereas the diffuse radiation transmittance makes up the greater part and should be sufficient to illuminate the room. For the tilted case Isec heat will contribute about 40% in winter and 15% in summer.

Conclusions

As has been shown, the system efficiently shuts out the direct radiation. This reduces glare. Even though the main part of the direct radiation is absorbed by the blackened side of the reflective layer, overheating should not be a problem, if the glass bars are positioned close to the outside glass pane, as the heat will be conducted that way.

Regardless of the system’s properties for direct radiation, the transmission for the diffuse radiation will be around 60% throughout the year, guaranteeing a high illumination level in the room.

Improvement could be made using photochromic layers, which would darken only on the focusing line). This would make a mechanical adjustment superfluous.

[1]

The improved case of the SIEEB resulted from the advanced technological solutions and control strategies such as sun shading, radiant ceilings, displacement ventilation and maximizing natural and minimizing artificial lighting. In the DOE simulations, these strategies are simulated as described below:

Sun shading: the values of direct and diffuse solar radiation are reduced to 50% during summer and 80% during winter.

Radiant ceilings: the set points for thermal comfort conditions corresponding to dry bulb temperature is increased by 1°C for summer and is decreased by 2°C for winter.

Displacement ventilation: reducing the values of fresh air volume by 20%.

Lighting: high efficient lamps and control sensors (dimming)

The above hypotheses considered for simulating the advanced technological solutions and control strategies are quite reasonable and are expected to calculate the values of energy savings reasonably well.

Figure 5 shows the monthly energy demand for cooling, heating and lighting & equipments corresponding to improved case of SIEEB preliminary design.

Figure 5. SIEEB (Improved case) — Monthly Energy Demand

The potential load reductions based on advanced technological solutions and control strategies are shown in figure 6. It has been observed that for improved case the annual energy load reductions for cooling, heating and lighting & equipments can be achieved up to 30%, 23% and 20% respectively.

2. Conclusions

A methodology for the energy efficient design of the Sino-Italy Environment & Energy Building (SIeEb) is presented. It has been shown that using various advanced technological solutions and control strategies in the SIEEB, an appreciable amount of energy savings can be achieved. Since the results, presented here, are in comparison with a reference case in which the building envelope is already optimised, therefore, compared to a baseline building, constructed as per the current practices in China, the

SIEEB is expected to contribute much higher amount of energy savings. SIEEB is an ecological and energy efficient pilot building and represents a model for a new generation of sustainable buildings. SIEEB can also be seen as an ideal case for assessing the benchmark for implementing the clean development mechanism (CDM), aimed to reduce CO2 emissions according to the accounting procedures defined within Kyoto protocols (IPCC, 2000).

References

J. Chang, Dennis Y. C. Leung, C. Z. Wu, Z. H. Yuan (2003), ‘A review on the energy production, consumption, and prospect of renewable energy in China’, Renewable and Sustainable Energy Reviews, 7, 453-468.

F. Butera, S. Ferrari, N. Aste, P. Caputo, P. Oliaro, U. Beneventano and R. S. Adhikari (2003), ‘Ecological design procedures for Sino-Italian Environment and Energy Building : Results of Ist Phase on the Shape Analysis’, Proc. PLEA-2003 Conference, Santiago, Chile, November 2003.

DOE-2 Manuals (Version 2.1) (1980), US National Technical Information Service, Department of Commerce, Springfield, Virginia, USA.

J. Chen (2003) Sustainable Buildings: the Chinese Perspective, Challenges and Opportunities, Presented at the COP-9 Conference, December 1-12, 2003, Milan, Italy.

IPCC(2000), Website www. ipcc. ch.

The buildings of the Umwelt-Campus are supplied completely with renewable energies, with a various amount of converters combined with equipments for rational energy usage like photovoltaic systems, solar collectors, heat pumps, air conditioning, solar architecture, earth-heat-exchanger etc. and a biomass energy conversion plant nearby for heat and electricity. All these technical active and passive converter are integrated in the building automation. The whole system has still to be analysed and optimised. For this reason, it is advantageous to integrate these necessary work on this system in the study courses to teach students, with the possibility of students own real experiences. In a first step, project and diploma works are started, to give an overview of the single system technologies and the technical data together with the underlying physical theories. An important support for this purpose is the deeper inside and knowledge of the technical engineer Mr. Andreas Doll, who is responsible for the whole building system. His experiences and reports given to the students are very valuable. The next step would be optimisations and integration of new technologies for research and development.

One of the first works for diploma thesis is that of Jorn Herz, who analysed the earth-heat — exchanger, which is combined to a heat pump and massive absorber. The earth can be used as a solar heat storage, which can in winter as well as in summer be used for an air­preconditioning. The heat exchanger system consist of horizontal pipes under the earth surface, which guides the air from outside in the building, with a cooling effect in summer and heating in winter. The earth is therefore used as a seasonal heat storage.

Additionally, there is a heat recovery system implemented, which restores a part of the heat of the air leaving the building back to the earth. A massive absorber at the air outlet works as heat storage for a heat pump.

Aim of the diploma thesis of Mr. Herz was first to describe the installed earth heat exchange system at the Campus and the corresponding physical foundations. And second he made measurements and model calculations, to get information about the quality of this installation.

The variational description of heat and mass exchange processes for a heterogeneous system with the account of electro-sorption processes in the continuum approximation has been carried out with the attraction of the basics of analytical thermodynamics. Analytical thermodynamics is a new trend in the development of classical phenomenological thermodynamics. Having the investigation subject and method being common with the classical thermodynamics, analytical thermodynamics differs from it at least by two peculiarities.

In the first place, it is based on the variational principle, which consequences are basic macrosystem laws — the first and the second laws of thermodynamics, and therefore has a broader scientific basis as compared with the classical thermodynamics. In the second place, the analytical thermodynamics differs from the classical thermodynamics by the analysis method, i. e. the vector analysis. The use of vector analysis reduces a body of mathematics of the classical thermodynamics to the generally accepted one for other macrophysical theories.

The outstanding works by Onsager have laid down the beginning of the deductive theory of irreversible processes and the establishment of variational principles of non­equilibrium thermodynamics [96]. The variational formalism provides a possibility of construction of the whole phenomenological theory of thermodynamics based on the variational principle. The heat and mass exchange problems in the system in question are characterised by an unsteady nature, a considerable non-linearity, the interconnection of heat and mass transfer processes, multi-dimensionality, non-homogeneity and electrochemical activity of heat-insulating system.

To main advantages of the variational description of irreversible processes, one normally relate the following [97-104]:

— a high degree of generality of the physical content of variational principles, as they express fundamental physical laws, and differential equations of irreversible processes in macrosystems and boundary conditions of their implementation can be obtained from variational principles,

— the use of direct methods, by means of which accurate, approximate analytical and numerical solutions in the problems formulated in the variational form can be obtained,

— an opportunity to obtain rough approximation to the accurate solution of the problem, which is especially important in engineering calculations, at that most various information on the process can be used for the selection of a trial solution, including empirical data or accurate solutions of simpler problems of this class;

— the use of extreme values of variational principles functionals for obtaining of integral estimates of the approximate solution accuracy;

— a property of functionals to express important characteristics of irreversible processes such as energy dissipation or entropy production, heat taking part in the process.

The variational principle developed by my teacher V. V. Chikovani [44,45] has been called basic variational principle of the classical phenomenological thermodynamics. Such name of the variational principle is connected with the fact that the basic laws (principles) of classical thermodynamics follow from it — the first and the second laws of thermodynamics.

The main differences of the V. V. Chikovani’s variational principles from the well-known principles of thermodynamics of irreversible processes [100, 105, 106, 108, 109] as well as from the conditions of steadiness of functionals having a formal mathematical nature [101, 110-120] is that they, though being an expression of the basic variational principles of the classical phenomenological thermodynamics, have a simple and clear physical meaning expressed in terms of fundamental macrosystem properties. These principles have an integral form both by spatial variables and by time, which provides the use of not only the Kantorovich’s method but also the most effective direct method of variational calculus, i. e. the Ritz method.

As it is well-known, at the description of heat and mass exchange processes in continua, an assumption on the local equilibrium is used, in accordance with which any differential volume of the continuum is an internal equilibrium thermodynamic system [45].

Each differential continuum volume can be considered as a multi-phase system characterised not only by thermodynamic parameters of state being equilibrium over the whole differential volume but also by parameters determining irreversible processes of interphase interaction inside the differential volume being non-equilibrium within the limits of the differential volume (but being equilibrium within the limits of each phase being a part of the differential volume.

A peculiarity of the proposed superinsulation model as a continuum is the concept of any differential volume in the form of a two-phase system (V. V. Chikovani,

N. V. Dolgorukov,1991). The mass exchange occurs between the gaseous and solid phases due to sorption processes. The temperature within the limits of the differential volume is considered identical for both phases. We will describe the sorption system "adsorbent — adsorbate (solid phase)” by parameters characterising it on the whole, i. e. without account of the real structure of the adsorption phase. Such approach allows to use the gas release characteristics of the superinsulation materials being determined experimentally and obtain a mathematical model being suitable for the description of heat and mass exchange processes, both at the availability of gas adsorption in the surface layer and in the material micropores (V. V. Chikovani, N. V. Dolgorukov, 1991).

In order to obtain the variational formulation of the mathematical model of molecular heat and mass exchange processes in the superinsulation, one can use the basic principle of the classical phenomenological thermodynamics [44,45]:

bQ = 8j Pdr =8j ^Pn(xj, х2,Хз,…,xN)dxn = 0, (1)

1-2 1-2 n=l

‘where P is a vector in the N-dimensional space of macrophysical parameters of state Xn(n=1,…, N) of a thermodynamic system characterising its interaction with the environment; dr is the radius-vector differential in the same space.

The variational description of the heat and mass exchange processes for a heterogeneous system with the account of electro-sorption processes will be given in detail in the second part of the review.

The new library is constructed with high facade windows and through-going skylights which assures a high level of daylight and a good daylight distribution in the library. The aim was to obtain the high level of daylight and good daylight distribution without glare problems and at the same time reducing the internal heat load from the sun.

For this purpose the light planning software Relux Professional/Vision was used. The calculation is based on a version of Radiance that has been revised by Relux.

1.1 Skylights

For reducing the internal heat load from the sun and overcome possible glare problems the skylights have been developed with integrated constructive solar shading, as seen in figure 3.

The depth of the constructive solar shading (fins) is 200 mm at intervals of 500 mm has been considered carefully with Relux. The advantages of the constructive solar shading are:

— Part of the skylight construction

— Permanent solar shading

— Permanent glare shading

— No mechanical parts

— No repairs and maintenance

— Contributes to an optimized daylight distribution in the library

— Gives a special ray of solar radiation into the library, see figure 10

In figure 4, a picture of the skylight as constructed on site is shown

M. Ciampi, F. Leccese and G. Tuoni

Department of Energetica “Lorenzo Poggi” — University of Pisa

Faculty of Engineering — Via Diotisalvi, 2 — 56126 Pisa (Italy)

e-mail: m. ciampi@ing. unipi. it; f. leccese@ing. unipi. it; g. tuoni@ing. unpi. it

The energy performance of peculiar ventilated structures, such as walls with advanced screen, is investigated. In these structures the duct thickness is small and the air flow inside is laminar.

The obtained results show that an energy saving, even exceeding the 20%, can be achieved by using these structures in summer, compared to the same non — ventilated structure; in winter, the increase in heat losses, due to ventilation, can result to be remarkable and such as to make advisable closing the air duct or reducing the ventilation.

Introduction

The European Directive 2002/91/CE on the energy performance of buildings [1] devotes its attention to the necessity of more carefulness in the building design, with particular respect to its envelope, in order to reduce the energy consumption as well as the impact on the outdoor environment. The Directive also focuses its attention on the fact that the air­conditioning plants have become, in the last few years, widespread systems; this causes a remarkable electricity demand growth in summer, e. g. during the last August, in Italy, several black-outs occurred due to an excessive demand from the users. For this reason the Directive suggests adopting priority strategies which could enhance the thermal performance of buildings especially in summer. For instance, passive cooling techniques could be developed in order to improve the indoor climatic conditions as well as the microclimate around buildings. The Member States of the European Union have to bring into force the laws, regulations and administrative provisions necessary to comply with the Directive at latest on 4th January 2006.

The ventilated walls (VW) are fully included in the passive cooling techniques, explicitly provided for by the Directive. In the last few years they have been widely investigated by several authors [2-10]. In [4, 8, 10] the same authors have proposed a calculation method, suitable for design applications, in order to evaluate the reduction in summer thermal loads achievable by using VW. They have also studied, in [5], the influence of the variation of several thermal and fluid dynamic parameters on the energy performance of a VW.

In this paper, referring to several remarks synthetically reported by the same Authors in [9], the energy performance achievable, with particular reference to the summer case, by using VW characterized by small thicknesses of the air duct and by laminar flow, is investigated. These building components are generally indicated, in technical literature, as walls with advanced screen (ASW) which are frequently used in contemporary architecture. The obtained results show that an energy saving, even exceeding the 20 %, can be reached by using these structures in summer, compared to the same non — ventilated structure.

The southern curtain wall composed of PV modules is capable not only of electricity, but also heat generation. The sun rays falling on their surface are being
transformed into the heat. Due to the so-called "greenhouse effect” the heat is trapped in the empty space between the layers. In this way, a 15 cm cavity is heated by means of insolation. During winter, the heated air is conducted to a heating plant, where it is used to warm the fresh-air intake. The heat gains from PV modules surface also play a significant role in passive heating and cooling of the inner space. The cavity becomes a passive solar collector and thermal buffer. It participates in decreasing unfavourable temperature fluctuations by the inner layer of the southern wall, as well as constitutes an extra thermal isolation. The same thinking happens in summer. The heat coming from the PV modules causes the so-called "stuck effect” that intensifies natural ventilation in the void between two layers. This enables to draw out used warm air from the inner space, favourably increasing air volume exchange. This contributes to preventing overheating during sunny outcast days. In this way, the PV modules’ usage exerts influence on thermal comfort directly all year round (fig.2).

In terms of visual comfort, the cells within the PV modules are laid to a pattern that allows daylight to pass through the gaps. This creates a pleasant lighting environment in summer, shielding the interior against excessive direct sunlight and giving subdued natural light under heavy solar radiation. On the other hand, the densely laid opaque PV cells stop desirable winter daylight causing the inner space to be naturally lit with the aid of the skylights, glazed surfaces in the rear walls and glazed „belt” in the upper part of the southern curtain wall. During outcast days, sun rays leaking through the gaps cause strong contrasts and shadow patterns on floor surfaces that may disadvantageously affect lighting environment and comfort of the user.

fig.3lighting environmentbythe Last but not least the curtain waN made of PV

wall with PVm0dules modules does not allow the occupants to retain visual

contact with the outside (fig.3).

Both the energy use of the whole buildings and of single classrooms have been simulated separately in order to evaluate general consumptions and local discomfort conditions.

At building scale total consummations for cubic meter was calculated for the school models and divided into:

— heating consumption to maintain comfort conditions inside the building;

— cooling consumption to maintain comfort conditions inside the building;

— lighting consumption for the period when no natural lighting is available and areas with

low daylight.

At room scale: classrooms with critical interior conditions have been selected and analysed; for each classroom the following parameters have been evaluated:

— average internal temperature;

— sensation temperature trend over a two weeks period (based on typical temperature of the four seasons);

— daily temperature variation (At).

Strategies of interventions

The strategies of interventions for the schools, can be divided into three categories:

— energy gains control (internal or solar gains);

— structural cooling;

— sensible cooling.

For these categories several strategies of interventions have been proposed; for each strategy a table that describes: technology, dimensions and physical parameters has been proposed.

Energy gains control

Reduction of thermal gains through the envelope:

— roof insulation;

— facade insulation by ventilate facade;

— replacement of the windows.

Solar control trough:

— shading of the windows;

— shading of the fagades.

Reduction of internal gains:

— increase of daylight using sun ducts and light shelves applied to the windows;

— improving energy efficiency of lighting fixtures.

Structural cooling by active night ventilation

Improving night ventilation, it is possible to reduce energy consumption in summer, when the outside temperature is low then the inside, the outside air is faced in the building.

Sensible cooling by direct cross ventilation of the classroom

As known, to have a sensible cooling it is necessary to have air temperature below skin temperature (33°C). In Mediterranean countries this effect can be better achieved using low speed fan especially when the outside air temperature becomes to hot for direct ventilation.

Guidelines

The guidelines are intended as a support for the planner during the selection of the retrofit interventions. For every intervention the effect on energy consumption and comfort conditions can be visualised. On the other hand it is possible to plan the interventions with the best energy efficiency and pay back.

A short description of the effects of some interventions are reported:

Roof insulation

The analysis shows that the roof insulation produces the largest energy saving in every school building with low dependence on orientation and building technologies:

Improving roof insulation energy saving of about 40% can be achieved.

This percentage can be improved shading the roof using tents or pergolas (summer cooling reduction)

Windows shading

The cooling consumption can be significantly reduced using shading systems to protect transparent surfaces.

For every type of window and orientation, the effect of some shading devices is reported together with the description of the technological solutions (figure3).

Shading the windows the reduction of energy consumption changes significantly according to orientation. In the model A (prefabricated panels dimension 60×240 cm) for example, we had the following results:

building with north-south axis 19% energy saving;

building with east-west axis 22% energy saving;

building with northeast-suthwest axis 30% energy saving.

Shading the windows both energy consumption can be reduced and thermal comfort improved due to the reduction of direct solar radiation near the window.

Fagades insulation

Ventilated fagades reduce the cooling consumptions of approx. 20%. This construction is quite easy to build and the solution is highly recommended for school buildings without or with poor insulation into vertical panels.

Windows replacement

The effect of old windows in bad conditions is very important but cannot be easily modelled by simulation software. In our experience this problem is normally under estimated.

Windows replacement is necessary in all rooms facing north and when plastic sheets have been used for the orientations the effect of windows replacement has be evaluating.

The global effect of all the interventions leads to a 60% of energy saving in all the simulated buildings.

SHAPE * MERGEFORMAT

heathg Cooling lighting

figure: 5 example of a table proposed for each solution. The graphic compare the comparison the energy consumptions (total, heating, cooling and lighting) of the building before the retrofit with the energy consumption after the retrofit.

The icons describes the physical proprieties of every surface (wall, floor, window, etc).

Rosangela Tenorio, University of Auckland

This paper demonstrates how the use of active or passive means only does not give the appropriate answers to a tropical design when considering housing. The author discusses about the idea of both modes of operation being used simultaneously or in parallel, and how this concept has been developed for one experimental prototype in tropical areas of Brazil (Northeast region). Extensive parametric simulations have been conducted using the prototype, and thermal comfort levels along with energy use were assessed and compared. The prototype design has also taken into account the appropriate use of resources through sustainable design features. The results have demonstrated that for regions such as the warm-humid tropics, the use of a mixed running strategy have optimized energy performance and provided better levels of thermal comfort in a much more effective way. It has also demonstrated the integration of energy efficiency and a PV grid connected system, while enabling those daytime electrical needs to be accomplished by the photovoltaic component.

Lacasa can be compared to a library of building blocks of buildings and technical installa­tions, ordered in "Classes" and "Subclasses", and one which allows further development and additions. Each Block models a real building block, such as walls, windows, heating units, pipes or controls. When you click on a block, a dialog window pops up, allowing the user, for example, to select the geometry of a wall or look at its construction (see Figure 1). The input parameters can be either given as numbers, or alternatively as freely defin­able variables. The latter feature is particularly interesting when using the models for an optimization procedure.

In order to account for the needs of design engineers as well as scientists, Lacasa offers the possibility to select among different applications ("ENGINEERING", "SCIENTIFIC", and various forms of data administration), just by using the mouse. For further details, an

online help can be activated from the input mask of each block, and printed out if needed (PDF file). The building-blocks structure of Lacasa propagates through all levels of the li­brary. Its intuitive and uniform operation control makes getting started easy, and vastly fa­cilitates implementing new models.

Lacasa was developed under Windows2000 using MATLAB-Simulink Version 13, but will work under Linux as well. This requires the existence of a license for MATLAB-Simulink for Linux, and recompiling all C-sources with the appropriate Linux compiler. All other files are in principle Linux-compatible. At the present stage of development, Lacasa consists of 740 files which require 40 MB of disk space. It is worthwhile pointing out that 82% of these files are aimed at user-friendliness, as for example the easy data management and the graphi­cal user interface. The computation models needed for simulations and the online-help claim only 8.2% and 8.8%, respectively, of Lacasa’s total amount of data.

4 Database

All the data concerning the characteristics of the components and materials used in the application "ENGINEERING" are saved as text data files. The data management is such, though, that the user does not need to access the text files directly. Lacasa possesses a pre-processor for weather information, which can read any file, structured in columns,

containing raw weather data, automatically filling in the missing weather elements and generating a data set with 21 weather elements, formatted according to the requirements of Lacasa.