The authors have developed and produced the laboratory model of solar-pumped iodine laser. The tube-type high pressure xenon lamps are used to simulate solar light.

The radiation spectrum of these lamps measured in VNIIEF (see fig. 1) corresponds to the solar spectrum within absorption band of the active laser medium [1]. The model has the

closed cycle system (CCS) for its active medium. The concept of the model is presented in

fig 2.

The following parameters of CCS were obtained for the present model.:

1. Vacuum sealing of CCS is sufficient for laser experiments without the danger of the distorted by atmospheric gases, O2, H2O (~ 10-3- 10-2 mmHg within 5 min) results.

2. CCS provides for the stable stationary flux of the operating substance going through the laser cell. The flux velocity is 10 m/sec and lower. The pressure of the operational substance in the flux is smoothly regulated within 0 40 mmHg.

3. Duration of the active phase of the experiment is specified by the temperature filed of the model and presently does not exceed 2 min due to heating the laser cell walls up to ~ 2000C.

Hans Georg Beyer*, Gerd Heilschei*#, Stefan Bofinger#

*FB Elektrotechnik, Hochschule Magdeburg-Stendal (FH), D-39114 Magdeburg, Germany hans-georg. beyer@et. hs-magdeburg. de, fon: 0055 48 331 9379 216, fax: 0055 48 2345119 #meteocontrol GMbH, Stadtjagerstrasse 11, Augsburg, Germany.

Introduction

The EU-funded Project PVSat-2 aims at further development of procedures for the performance check of grid-connected PV-systems based on remotely sensed radiation data. Within this procedure a simple, but sufficiently performing model for the estimation of the MPP power output based on information of the irradiance input and the ambient temperature is required. Whereas in the forerunner of this project, PVSat, main emphasis was put on the modelling of modules with cells of the crystalline Silicon (cSi) type, PVSat-2 should cover the whole range of different cell technologies. Thus a model, able to reflect the efficiency characteristics of both the classic crystalline silicon and the various thin film technologies is required. In view of the handling of a big number of systems, the additional requirements to the model are the need of a restricted number of device specific input parameters only together with the ease of their determination.

Flexible methodologies for the analysis and performance assessment of complex energy systems have been developed taking into consideration multiple energy carriers. The methodologies include technological, economic and environmental aspects, which will enable energy utilities to carry out detailed analysis of the investments as well as overall optimization of their energy supply systems. Governmental bodies will be able to do comprehensive scenario studies of local energy systems with respect to environmental impacts and consequences of different regulating regimes. The methodologies are usually based on two main levels of modeling: First, components with standard interface are combined to generate an energy network. Second, these components are represented with the necessary mathematical details, but seen from a system perspective they are all represented by standard variables. All these tools are imbedded in a specialized software package called "MODES". This package has been utilized to simulate the power system shown in figure (1) and to test the problem of voltage collapse without and with different penetration levels of DG. Table (1) gives a summary of the studied cases. The study has been carried out under variable load condition at nodes N204&N206 which simulate not a unique operating point but real system operation for almost 6 min. Nodes N204 & N206 can be viewed as the connection points of distribution networks with total active demand of 300 MW, total reactive demand of 167 MVAr ; this case was considered as the base case
without DG (case A). To study the influence of DG on the problem of voltage collapse with the above mentioned scenario, three different cases (B, C, D) illustrate different penetration levels as well as injection node. At any one of the studied nodes, if the load has zero value, it indicates that the DG is capable to supply the demand of this distribution section.

As a brief description of the software package used, program MODES enables the dynamic simulation of electric power systems. It operates as DOS application under WINDOWS (95 and higher). The MODES makes possible to simulate:

1. transient stability of generators (loss of synchronism),

2. middle-term dynamics concerned with the primary control of frequency (frequency collapse),

3. long-term stability concerned with Load Frequency Control (LFC), On-Line Tap Changers (OLTC) and the excitation limiter actions (voltage collapse),

4. transient phenomena in home consumption of the units (driven start-up, switching over to back-up),

5. steady-state stability investigation of the power system for small deviations (oscillations).

Table (1): Summary of the studied cases

A renewable energy systems optimised for a specific application in one location may be inadequate in another location even if the application and user requirements are identical. The enormous variations between RES, which are the result of design options, user requirements and local climatic conditions, make it difficult to compare RES and the operation of the components which have been selected. Without comparison it is not easy to analyse the performance of components and systems and draw conclusions on the most suitable products and operating strategies. But only recommendations which take the specific conditions of use into account and are based on conclusions drawn from measurements of RES operation provide guidance to planners, users and operators.

As a first step, a method is required how to evaluate the data of monitored renewable energy systems (RES) in such a way that the operating conditions and performance of individual components and the system as a whole can be analysed and compared. It is then necessary to classify RES into a number of distinct categories in which the components are used in a similar manner and are subjected to the same combination of stress factors. Only RES belonging to the same category of use can be compared in a meaningful manner. Recommendations on how to design and operate a RES and how to test components and select the most suitable product can be made for each category. A particular RES has to be assigned to the categories which best reflect the overall conditions of use of the components and the recommendations for each category are then used as recommendations for the components and the system as a whole.

Authors to whom correspondence should be sent

Michele Pellegrino, A. Matano, C. Privato and R. Schioppo *

ENEA Centro Ricerche, Localita Granatello. P. O. Box 32,1-80055 Portici (NA), Italy. tel:+39-81-7723-267, Fax:+39-81-7723-344; mail to Michele. pellearino@Dortici. enea. it *ENEA Centro Ricerche Area Sperimentale di Monteaquilone (FG), Italy

PV plants could be the cause of radio frequency (RF) conducted radiated emissions, namely electromagnetic signals, at both the levels of voltage and current, travelling along the electric cables. The problem can be even more relevant for the Building Integrated PhotoVoltaics BIPV applications since their closeness to the domestic activities; preliminary measurements have been carried out for pre-compliance purpose at the Research Centre ENEA on a small photovoltaic fagade, while the plant was being in operation, e. g. delivering power. The pre-compliance procedure is vey important since if the conducted radiations overcame the standard values the same levels of signals could likely be present in other parts of the electric circuit inside the building, giving unwilling interferences with the other connected appliances. Another kind of noise could generate because the size of the modules and the length of the connection cables could make the plant acting as receiving antenna, so capturing and then introducing foreigner RF electromagnetic signals inside the buildings, mainly local broadcasting radio stations. In our survey the effects of differently configured inverters have been analysed: in one case one by one module connected inverters and the more traditional single inverter for a module string, in the other.

The surface grating structures designed by the numerical calculations are fabricated on Si substrates by using micromachining technique. We have used the dry etching process. The patterns are fabricated by photolithography, and the Si substrates are etched by the reactive Ion etching (RIE) technique. A typical SEM image is shown in Fig. 8. The scale of fabricated grating is almost the same as the designed values. Since Si is transparent in this wavelength region, Pt film is deposited after fabrication. The thickness of the film is about 200nm. The optical reflectance shows a typical absorption due to the micro cavity effect as predicted by the simulation.

2. Conclusions

The sky radiators with spectrally selective emission surface are designed by using the principle of diffraction optics. The surface grating shows high spectral emissivity at the atmospheric window region. By using numerical simulation of RCWA, the optimum design parameters of surface grating structures are determined in this study. The estimated cooling power shows very high performance. Surface grating are fabricated on Si substrates by using micromaching technique. The development of processes to fabricate the large area radiator is essential to practical applications.

I. Farkas1, I. Seres1 and L. KocsisS

department Physics and Process Control, Szent Istvan University (SZIU)
Peter K. u 1, H-2103 Gddollo, Hungary
Tel.: +36 28 522055, Fax: +36 28 410804, Email: ifarkas@fft. gau. hu

2Process Control Research Group, Hungarian Academy of Sciences-SZIU
Peter K. u 1., H-2103 Gddollo, Hungary

Abstract

In this paper a study has been carried out concerning to the preliminary design aspects of a 10 kWp photovoltaic grid-connected system.

Recently, the main issue was to select the most appropriate site for the installation of the area of about 160 m2 taking into consideration the shadowing-free solution. Three different places were considered including their advantages and disadvantages.

In order to make the final decisions for the selection the solar radiation income of the sites was modelled and calculated.

Introduction

In the framework of the PV Enlargement Project of the European Union, a 10 kWp photovoltaic system is under construction in the Godollo campus of the Szent Istvcn University, Godollo, Hungary. This set-up will be the largest PV instdlation in Hungary, and beside of the energy production it will serve as demonstration and educational purposes, as well.

The first step of the system determination, the finding the optimal site for the system is presented, along with the different alternatives. Until now the main units of the system were determined, and the type of the main elements were chosen. For the PV panels two different options are proposed as multicristalline and amorphous silicon technologies. The reason for the use of different technologies is the demonstration and educational purpose, such as the comparison of the different technologies at the same location under the same operating conditions.

The entire system is planned to consist of three different subsystems, about 3,3 kWp each. Every subsystem is planned to use an own inverter (the same type for each system). The system set-up includes the plan of the electrical connections and the mechanical installation to the roof, too.

Because of the educational and research purpose of the PV set-up, a detailed data logging system is planned to monitor every important data of the operation. The data logging system with the type of sensors and the monitored quantities are introduced.

Parallel with the system planning modelling was carried out for the determination of the behaviour of the system. Some modelling results are introduced. In the near future some preliminary measurements are to be carried out with the units available, first of all with the two types of PV panels. Beside some efficiency measurements the wavelength sensitivity of the efficiency will be analysed, as well. Another important factor, the effect of the shading is also planned to study along with different shape and size of shadowing, based on the measurements.

The solar laminates were made up as shown in figure 5. Six-inch square samples of glass, EVA and tedlar were chosen and the PV cells were placed in the centre of the laminate. A layer of fibreglass was placed behind the cell and is the same size as the cell. All the layers were cleaned with a chemical detergent to ensure full contact between the individual layers.

Eighteen such laminates were made up and individually tagged to account for all possible combinations shown in table 2.

Using heat resistance equations and the measured data from earlier conducted at University of Limerick, the following results were obtained:

PV cells have usually a blue or black colour. The reason for this is the normal choice of antireflection coating or the surface finish.

Colour of PV cells and modules can be altered by two methods namely:

1. By varying the thickness of the anti-reflection coating. So the colour does not need always to be blue. It can be silver-like, blue, bronze, gold, green, and magenta. It can even be a rainbow if the thickness varies gradually.

2. By using coloured and or screen-painted glass to cover or sandwich the PV cells. Even opaque glasses can be used for this purpose.

We perceive that a surface has one certain colour if that particular surface mainly reflects that colour. A blank uncoated Silicon surface will reflect nearly all the incident light therefore it gives us a silver-like appearance. On the other hand a surface with a black finish will hardly
reflect any colour therefore absorb maximum the incident light. This would be the ideal PV surface finish. An overview of possible colours is given in Figure 14. The typical cost for adding colour to cells is 2 to 3 times the price of normal cells (per cell). The colour will also result in a degradation of performance over normal cells of about 20%.!!

Figure 14: Example of various coloured solar modules by varying thickness of anti reflection coating of the cells. This is typically associated with the need to create a distinctive look either for security reasons or for architectural reasons [BP Solar, 2004]

1.1 Optical properties:

Optical properties of ZnS thin film depend on the initial solution, its flow and the substrate temperature. ZnS films prepared from ZnCl2 precursor show, in general, better optical properties than the films prepared from zinc acetate dehydrated solution. Transmitance values obtained from thin films vary from 80% to 85% for zinc acetate and zinc chloride solution, respectively; these results are in agreement with the values found by other authors (75-90%) [7,18,19]. Figure 1 shows the transmission spectra of ZnS thin films obtained from ZnCl2 solution onto the silicon substrate, using different spray rates. The band gap and thickness values calculated from experimental measurements using Swanepool Method [15], are 3.80eV and 360nm respectively, for the ZnS thin film prepared from ZnCl2 precursor. The increase in the fundamental band gap of nanostructured material can be attributed to the quantum size effects [19-21].

1.2 Structural and morphological properties:

ZnS thin films prepared from zinc acetate dehydrated and thiourea solution are amorphous, while thin films prepared from zinc chloride solution show low crystalline and its difractogram have a unique peak at 20=28.77. In general, ZnS thin films prepared from both solutions have smooth, homogeneous and dense surfaces (Fig 2). ZnO/ZnS bilayers show a less smooth surfaces produced by the ZnO thin film prepared over the ZnS thin film.

Figure 1.- Transmission spectra ofZnS thin film obtained from zinc chloride and thiourea solution at 450°C, using different spray rates. (A) 30 ml/h; (B) 40 ml/h; (C) 50ml/h.

Figure 2.- SEM micrograph of ZnS samples on silica substrate. 2.1.Prepared from zinc acetate dehydrated and thiourea solution (A) x5000. 2.2.Prepared from zinc chloride and thiourea solution (A) x5000 2.3 y 2.4. ZnO/ZnS bilayer where the ZnS thin film has been prepared from a zinc acetate dehydrated solution and thiourea, (2.3)x5000, (2.4)x25000.