A numerical model of the vegetation elements has been elaborated and is currently under validation. It will be incorporated into the code AGLA [1], [2]. The effects of the plants over the facade are: (i) Interaction with solar radiation (ii) Evaporation cooling (iii) Reduction of wind velocity (and thus, heat transfer coefficient) at the facade surface (iv) Shielding of thermal radiation.

Mathematical modelling of complex living entities such as plants is extremely complex. To elaborate a model of reasonable accuracy, the first task was a sensitivity analysis of the effect of each of the previous phenomena over the energy that is gained/lost by the facade. The conclusion is that the main effect is the interaction with the solar radiation. Therefore, most of the work has been addressed to predict it correctly.

To do so, a Montecarlo ray tracing code (VICACO — VIrtual CAnopy COde) was developed. If the detailed geometry of the plant (leaf by leaf) and the optical properties of the plants (see the previous section) are available VICACO, allows to evaluate the fraction of incident solar energy that reaches the facade after multiple reflections within the canopy. Illustrative VICACO results are shown in Fig. 7. Using random distributions of leaves, VICACO has allowed us to identify the main geometric parameters that describe the canopy.

A complete description of the models is beyond the scope of this paper and will be pub­lished at the end of the project.

Preliminar results of the numerical model are presented in Fig. 10. As can be seen, the presence of the plants can reduce substantially the overheating in summer. The main effect is the reduction of solar radiation. This reduces the energy spent in air conditioning but also the temperature of the indoor facade surface, improving the indoor thermal comfort.

It was the aim of the project to develop a practical planning and diagnostic tool focusing on the analysis and optimization of energy use, in the framework of renovation and retrofitting programs, in existing buildings, as well as new buildings starting from the design phase. In order to ensure the practicality of the tool, the engineering firm GERTEC GmbH, Essen, was integrated into the project as an commercial partner of the Solar Institute Julich. The following functions were encompassed:

Jorn Herz, Andreas Doll, Klaus Brinkmann
Umwelt-Campus Birkenfeld, Germany

Address for Contact:

Prof. Dr. Klaus Brinkmann
Umwelt-Campus Birkenfeld
Automation and Energy System Technology
P. O. Box 1380, D-55761 Birkenfeld/ Germany
E-Mail: k. brinkmann@umwelt-campus. de

This paper presents an analysis of the system technology of an earth-heat — exchanger combined to a heat pump, which was (ca. 1995 — 2002) realised at the building of the Umwelt-Campus in Birkenfeld, which belongs to the University of Applied Sciences Trier in Germany. The heat pump works for a recovery of the stored heat in a massive absorber at the air-outlet, in order to minimise energy losses in the atmosphere. Examinations and comparisons to others up to now realised earth-heat-exchanger projects in Germany, done by Jorn Herz for reaching his diploma degree, show, that the special configuration at the Umwelt-Campus Birkenfeld seems to be the first of that kind. This presentation gives an overview of the system technology and working principle. Measurements and mathematical modelling were done, in order to evaluate the efficiency of this combined system and to identify to advantages and disadvantages of this realisation. Additional, practical experiences with stability and working conditions etc., made by Andreas Doll, the responsible technical engineer for the Campus Buildings, are integrated.

Only a few works have been devoted to the matters of electro-adsorption interaction of SVHI screens with the residual gas [1-5]. At the same time, the F. F. Vol’kenshtein’s monograph [48] is devoted to electronic process on semiconductor surfaces where the results of the 40-year work of the author and his colleagues in the field of physics and chemistry of semiconductor surfaces are summarised. The semiconductor surface in the work cited above is considered from the positions of the interface between two phases. The interaction between gas molecules of the residual medium and free semiconductor electrons and holes occurs at this interface. As the majority of metals have an oxide film, then their surfaces in most cases are semiconductor surfaces. Among works devoted to the physics and chemistry of semiconductor surfaces, the most substantial are monographs by K. Haufe [49] and S. Morrison [50], F. F. Vol’kenshtein [48], A. V. Rzhanov [51]. It is necessary to note a great contribution of the V. S. Kohan’s school into the theory of interaction of active gases with metal films [52]. A very meaningful is the monograph of the Indian physicist K. L. Chopra [38]
devoted to the investigation of physical processes passing in thin films of metals, semiconductors and dielectrics.

By the present time, the main tendencies of further development of the superinsulation have been carried out in the following directions. First of all, studies devoted to the optimal installation of the superinsulation [53], the process of vacuuming of the cryogenic equipment superinsulation [54-57], investigations of gas permeability of the superinsulation [58, 59], the determination of diffusion coefficients of residual gases in the superinsulation [60], investigations of the kinetics of gas release of heat-insulating materials in vacuum [61], investigations on studying of the distribution law of residual gases in superinsulation layers [62], investigations on studying if the unsteady pressure field in the superinsulation [63], investigations of the properties of superinsulation materials [64, 65], investigations of heat and mass exchange in the superinsulation [66-68]. The work [69] has a high theoretical and practical value, Mikhalchenko with colleagues have detected therein a hundred-fold pressure ratio in the middle of the sample over its thickness and on the outer insulation layer with the temperature of 77K. In the work [70], it has been obtained that the pressure in the superinsulation grows proportionally to the squared insulation thickness. In addition, it has been detected that the pressure distribution over the insulation thickness in the steady mode has a parabolic nature.

In order to improve the conditions of superinsulation vacuuming, it has been proposed to perforate screens [71]. Barron [72] has come to a conclusion that if the perforated hole area equals to 10% of the screen area, then the rate of gas pumping-out from the insulation increases approximately by 1000 times. In the work [73], it has been shown that gas releases of screens can be absorbed inside the insulation, for example, by means of the use of glass — fibre paper with filaments from activated charcoal as a pad’s material. In the work [74], it has been determined that gas releases of screens can be absorbed inside the insulation, for example, by means of a low-temperature gas absorber.

Studies are known devoted to surface effects on a dimension-quantised screen — vacuum heat-insulation in the conditions of cryogenic temperatures and vacuum [75], influence of surface centres on the gas medium formation in HIC, selection of a metallised coating of the superinsulation, optimisation of the technology of manufacture of a metallised film with the account of electro-adsorption phenomena on the film surface: selection of the crystal size to be applied onto the polymer film substrate, values of the thickness of the metal spraying onto the film, management of the metallised film properties by the introduction of special alloying gases at the manufacture, etc.

Quite a few works have been devoted to operational methods and means of maintaining and monitoring of the optimal mode of the superinsulation functioning [76, 77].

The investigations devoted to surface effects on dimension-quantised films in the superinsulation, influence of the surface centres of superinsulation screens on the gas medium formation in HIC, selection of the metallised coating of superinsulation screens, optimisation of the technology of manufacture of a metallised film with the account of electro­adsorption phenomena on the film surface, selection of the crystal size to be applied onto the polymer film substrate, values of the thickness of the metal spraying onto the film, management of the metallised film properties by the introduction of special alloying gases at the manufacture, management of the value of the surface potential of superinsulation screens by means of connection of the superinsulation screen to an external potential, etc., are completely absent.

In addition, the matters of selection of the protective casing of the reservoir, introduction of an additional "dry" volume into the cryogenic reservoir design between the
casing and the additional moisture-insulating shell are completely missed. The shell can be made with an overflow moisture-impermeable valve. As to the matter of exclusion of a moisture film on the outer heat insulation surface, we are aware of only one work [78].

It is well-known that the film alloying by gas impurities can lead to the improvement of their properties [79]. The task of management of the film properties by their alloying with impurities was stated in a number of works [80].

A special attention will be paid to the management of properties of screens on the polymer basis by means of their modification by the ion implantation. By the present time, a sufficiently large volume of work on the investigation of kinetic phenomena in conducting organic films has been carried out [81-86].

The complexity and diversity of processes being observed in heat-insulating cavities cause a necessity of the conduction of additional emergent experiments with the use of newest measuring apparatus.

The urgency of investigations on the development of a fundamentally new superinsulation is in the present time dictated by the beginning of intensive works on the development of ecologically clean transport on hydrogen in all developed countries.

All levels of society should be sensitive to the environmental issues. The ecological parameters must be taken into consideration as a part of the external costs. But these costs someone has to pay. The sustainable development has to balance power supply and demand respecting both economical and ecological criteria. However, it will be very difficult to secure energy at low cost, with high rates of economy growth and acceptable pollution levels. Having this in mind, renewable energy resources could play a dominant role in the 21st century alone and in combination with other ecologically acceptable fuels.

The price of fossil fuels (coal, oil, natural gas) does not represent their true cost to the society. Besides many factors the ecological impost also has to be included in cost of fossil fuel. The impost consists of:

— Repayment of environment contaminators according to the emission of CO2, SO2, NOx,

— Repayments according to the burden of the environment-communal or dangerous waste,

— Repayments for the environment contamination caused by traffic — motor vehicles.

The example of solar energy utilization project described here shows savings of

thermal energy in the system of space heating and domestic hot water preparation. A yearly value of solar contribution at level of 70 % is expected. The solar contribution in electricity supply of the house is around 50%. Also a temporary excess of electricity produced in PV generator can be delivered to the network. The reduction of the emission of the CO2 at the rate of 6500 kg per year is expected.

The house is also equipped with rain-water collection system, saving almost 55% of overall sanitary domestic water demands.

2. Conclusions

The pilot project "Solar roof Spansko-Zagreb" shown here presents production of both thermal energy and electricity in the family house. In this work the possibility of energy savings in the system of space heating and domestic hot water preparation is presented in the case when solar energy is used, and electricity production from solar energy is shown. On the other side, almost ideal supplementation of the city gas as an additional fuel with solar energy, especially in the reduction of harmful gases emission is shown. The significance of this pilot project is in the usage of renewable energy resources, which are capable to ensure large enough amounts of energy for both economic growth and sustainable development for the well of future generation.

It is possible to reach high accordance of the measured and simulated room air temperatures, when very detailed input data is available. Little differences i. e. in the user behaviour can alter the results significantly because the heat demand of the building is very small (ref. Table 1). An increase of the room set temperature from 20°C to 25°C increases, for example, the space heating energy demand by over 50% (with all other parameters fixed).

For detailed simulations and comparisons the user behaviour taken from standards is not sufficient. Even user profiles evaluated from questionnaires are sometimes not accurate enough (this is especially true for the ventilation by windows). Figure 2 shows the examples for the daily distribution of persons in the apartment and the electricity demand other than HVAC system chosen in this study.

Figure 2 Average daily distribution of persons in the apartment (left) and electricity
demand other than HVAC-system (right) (Streicher et al. 2004).

The three operations, measurement, decision and action, are always present in every type of control. Measured are ambient conditions, in our case the internal illumination, global and reflected solar radiation and the current position of the roller blind. On the basis of the measurements, the controller decides what to do to follow the desired (set point) inside illumination. As a result of the controller’s decision, the system must take an action. This is in our case accomplished with the suitable alternation of the roller blind position. Variable
solar radiation is called a disturbance in the process, because it causes the deviation of the controlled inside illumination from the set point value. Because of the external disturbances, such as changeable solar radiation, the automatic process control for the window geometry alternation is justified. The illumination algorithm was designed and developed progressively during the research procedure. The design of the light control loop was based on experimentation. The first set of measurements was used to examine the relation between the outside solar radiation and the inside daylight illumination with different surfaces of the window and in changeable weather conditions. After getting the experience in this sphere the control algorithm was developed and improved progressively with the aid of experiments. The control algorithm is created in the IdR BLOCK environment, where placing and interconnecting various blocks define the control scheme. To each block a subprogram, which performs the necessary operation of input data, is assigned. Blocks are grouped into block groups, called loops, and they are framed into control algorithm. The proper functioning of the control algorithm is of essential importance for the adequate adjustment and velocity of alternations of the roller blind with regard to external disturbances, i. e. solar radiation changes. The assessment of the control algorithm is subjective. We observed, how the alternation of the window geometry — roller blind positioning — influences the internal lighting and luminous efficacy with respect to the given solar radiation.

For adaptable window geometry fuzzy logic [7,8,9] is a system advantage in controlling, because of the fuzzy controllers’ ability of non­linear mapping between the ambient conditions and the corresponding roller blind position. In fuzzy systems the advantage of reduced complexity is taken into account and it is achieved with subjective estimation of the used information. The principle, which derives directly from human reasoning, is based on a linguistic model, which is expressed with a set of conditional rules, IF-THEN statements. We want the movable shading device to be alternating, as if it was adapted manually to the internal demands and external conditions. We have to find a linguistic model for the optical process as a basis for the fuzzy controller, expressed with a set of fuzzy rules. With the determination of IF-THEN statements and fuzzy sets the input and output relations for each fuzzy controller are determined. The inputs are in our case on-line measured external and internal conditions and the output is an appropriate roller blind position. The designer must select appropriate fuzzy sets with membership functions for all input and output variables (Fig 2).

The input and output numerical values must belong to appropriate membership functions, which are correlated and combined with the aid of logical fuzzy in IF-THEN statements. With the aid of the linguistic terms the measured values are described as sets of ordered pairs: numerical values and degrees of memberships to fuzzy subsets. The correlation, non-linear mapping between two inputs and one output, is graphically represented with a specific 3D shape as shown in Fig. 3. The actual numerical output value, the current position of the roller blind, is located on the 3D shape. The output values depend on the inputs, measured condition values and on the designed fuzzy model.

The control algorithm is defined as cascade control (Fig 4). Fuzzy controller is used as the main controller while PID is the auxiliary one.