Initially work concentrated on editing the specification document for UESP. Here component classes have been defined for all available power supply components and loads. General systems layout of UESP systems have been designed, considering the specific requirements of the various target applications (from small telecom power supply
to minigrids). For the communication bus CAN (Controller Area Network) has been chosen. It is widely used in the automotive industry and therefore is both reliable and inexpensive. The basic communication procedures between components as well as their parameter sets and quantities have been specified.

Currently the UESP component interfaces are developed. They will enable for conventional components to be operated in a UESP system as long as UESP compatible components are not commercially available. Simultaneously the first version of the software protocol stack is developed. Shortly system tests will be carried out.

A second example of the application of the technique is the provision of a uniformly illuminated receiver surface for heliostat field. The major difference between a paraboloidal dish and a heliostat field is that the optical properties of the heliostat field vary with the incidence angle of the solar radiation, because single heliostats track the sun. This is not the case for a paraboloidal dish where the complete system is always orientated to face the sun. Therefore, with a heliostat field the shape of an optimally uniform illuminated surface varies with the incidence angle of the sun.

By example, Fig. 6 shows the north south cross-section of four different surfaces for a single tower plant and the distribution of concentration over the receiver. The heliostat field has ground coverage by the reflectors of 100% when they are stowed parallel to the ground, and the solar zenith angle is varied for a solar azimuth of 0.

For a heliostat field, the angle between the incoming radiation and the normal of the heliostat field and the angle between the outgoing radiation and the field normal are not equal as in the case of the dish. Therefore the area ATower, which is normal to the radiation reflected onto the tower, usually is not equal to the area ASun, which is normal to the incoming solar radiation.

We may define pSun to be the angle between the normal of the heliostat field and the incoming solar radiation while pTower to be the angle between the normal of the field and the radiation reflected onto the tower. If pSun > pTower than AS. un < A^ower and if

в Sun < Slower than AU > ATower. For the case fisun < pTower, which is predominantly the case for regions further away from the tower or the sun standing in the zenith, radiation is lost due to blocking as described by Schramek and Mills (2003). Therefore, the density of radiation passing the area A^ower is E^ower = ESun.

For the case zenith angle of the sun pSun — 0 as shown in Fig. 6 we have pSun < PTower for the whole heliostat field which means that Elower — ESun. For an assumed flat receiver d2FieU / dReceiver — const. for all a where dFiM is the distance from the focal point to the specific point in the heliostat field. Therefore for the heliostat field, analogously to the dish, we have following equations:

and

CRecever (a) — cos(r(a)) (Eq. 6)

Receiver

Since for a flat receiver d2FieU / dReceiver — const. while cos(y(a)) is decreasing for the outer regions the concentration decreases in the outer regions as well. Therefore, the receiver has to be bent closer to the focal point in the outer regions to achieve uniform illumination. In Fig. 6 it can be seen that this is the case in the optimised result.

If eSun > 0 there is a region close to the tower where pSun > pTower and where therefore Elower is given by Eq.4. Therefore, we may use the following equations:

dField(a) — AField(a) — EReceiver(a) C°s(Psun) — C1 (a) C0S(eSun) (Eq 7)

dRece, ver(a) ARece, ver(a) ELer(a) ESun С0^(в Tower) Rece"er С0^(в Tower) ‘

and

This gives us the generalised equation:

This means that for pSun > 0, for the outer regions where pSun < pTower, the receiver is equal to the receiver for /3Sun — 0 ,while in the inner region the receiver has to be bent closer to the focal point as well. This effect can be seen in Fig. 6 as well.

Fig. 8 shows the surfaces for uniform illumination for an Multi Tower Solar Array (MTSA), (Schramek and Mills, 2003).

Conclusion

It was shown that for a given concentrator system a receiver surface can be defined which is evenly illuminated.

This approach provides a means of avoiding the use of reflectors and their attendant optical loss and cost while providing acceptable uniformity of illumination over the receiver surface. It allows formation of uniformly illuminated surfaces either between the reflector and the focal point, or on the other side of the focal point.

Because of a lack of information on the energy to be harvested with portable solar panels, the PES group decided to do an exploratory research to quantify the difference of harvested energy with portable and stationary solar panels. The results from this research give an indication of the amount of energy that can be harvested with solar panels when integrated in portable products. The experiment was carried out by A. Takahshi and M. Weeda.

For the experiment eight identical RWE-Solutions ASI-OEM amorphous silicon PV-cells are used. The output of these cells has been proven identical under a one-sun halogen lamp. Four cells are placed on a (portable) shoulder bag, see figure 2. A thermo-couple is placed at the cross-point of the four cells. The shoulder bag is furthermore equipped with a Grant Squirrel 800 data-logger, in order to log the output that is generated by the four PV — cells. During use the surface of the bag on which the PV-cells are placed has an inclination of 70 to 90 degrees compared to the horizontal plane. The other four PV-cells are placed on an installation on the roof of a building, see figure 3. The output of these cells is also logged by a Grant Squirrel 800 data-logger. This stationary installation has a panel inclination of 70 degrees and is directed to the south. On the shoulder bag, as well as on the stationary installation, the four PV-cells are connected parallel.

During the experiments data is gathered simultaneously with the portable shoulder bag and with a stationary installation that is placed on a roof within a range of five kilometres of the shoulder bag. Every 30 seconds two parameters are logged: the voltage over a 0,1 Ohm resistor and the temperature at the cross-point of the four cells. The shortcut current is calculated from the voltage that is generated over the 0,1 Ohm resistance. The output power and efficiency of the PV-cell is calculated from the specified operating voltage of the PV-cell, the calculated shortcut current and the surface area of the PV-cell.

The shoulder bag is used on 17 December and 18 December 2002, 24 hours a day.

During the sample the bag is carried around by a student during a usual working day, resulting in measurements mainly inside buildings (93% of the day). Figure 4 shows the power generated on 18 December for both the portable and stationary setup. Figure 5 gives the Power Ratio over the day. This ratio is defined as the "portable power” over the "stationary power,” respectively generated on the shoulder bag and the roof installation. Based on this one day measurement it seems that the portable panels harvest 20 to 60% of the stationary power when outside. When the panels are used inside, for instance in between 9:00 and 11:30, the power ratio is very small, only 3 to 5%. During the sunny period of the day, from 9:00 to 16:50, the overall mean Power Ratio is 12,6%, with a standard deviation of 19%. The measurements should be executed over a longer period of time to give an adequate mean Power Ratio which can be used as an indication for portable products equipped with outside solar-panels.

Among the innovative technological approaches in the field of biofuel production that have been recently proposed by Russian researchers, the High-Rate Heating (HRH) is worth being mentioned because it provides a possibility to reduce the energy consumption of thermophysical and thermochemical processes used in biofuel production industry, and consequently, the price of biofuels. For instance, moisture extraction from wood sawdust by the HRH enables to diminish the moisture related energy consumption by approx.

40% [10]. This technology could be applied to pellets preparation process.

Russia also has priority in the field of electric power transportation through Resonance Single Wire Transmission Systems [11]. Based on the principal of high frequency wave propagation discovered by Nikola Tesla, this method uses the ability of low-conductivity media, such as thin wires made of steel, carbon fibres, etc. or even glass fibres with thin-
film metal coating which serve as a guide for high power electromagnetic wave. Commercialisation of this technology could give a start to revolutionary changes in power transmission practice and to substantial decrease of power transportation costs, thus enhancing the accessibility of Russian biofuel resources.

Conclusion

Russia has a great biomass raw-stock potential for a large-scale production of biofuels and electric power generation on their base. Low price for plant biomass, low labour costs, far too incomplete employment in rural areas and traditionally high level of expertise in high — tech industries provide extremely favourable conditions for that. At the same time, the biofuel consumption inside the country is not expected to expand significantly within the next two decades. Besides, in present transient economic conditions, projects with relatively long payback period do not appeal to national operators, and an external investments and/or financial support or/and guarantees from the government are needed to initialise the process. With the moderate-scale investments, it would be possible to establish a regular flow of Russian energy bio-products to the EU countries.

Slavisa Djukanovic, Advanced School of Business Novi Sad, Serbia and Montenegro

slavid@eunet. yu

Abstract

Global heating increases profitability of solar energy application in the Balkans. The most important market segments for wider solar cells utilization in Yugoslavia (Serbia and Montenegro) are solar pumps for irrigation in agriculture, traffic lights, lighting of weekend houses, air-conditioning, telecommunications, electric vehicles, solar hydro-electric power plants, sports centers and schools and ortodox monasteries. In addition to these applications of solar modules of relatively high capacity, a wide scope of applications of mini solar modules in consumer goods is given serious consideration (flashlights, bicycle lights, fan caps, beach hats, solar parasols, toys for children, solar watches, mini­computers, walkmans and alike). In this paper is projected gradually increase of solar cells applications in Yugoslavia, from 772 kW in 2006., to 3,901 kW installed photovoltaic power in 2010. year. The largest parts of this projected 3.9 MW in 2010., ought to be solar pumps (498 kW), telecommunications (470 kW) and traffic lights (468 kW).

Introduction

The energy sector is a fundamental sector of national economy and has considerable effects on the social and economic relations of every country. In Yugoslavia (Serbia and Montenegro), the emissions of harmful substances occur in dispersion by the final energy consumption (road transport, individual and industrial fire places) and concentrated in coal mines and thermal power plants. Pollution can be considerably abated by the use of filtering facilities and renewable energy sources. This can be implemented only if the consumers are willing to pay a correspondingly higher price for energy. Nowdays level of domestic final electricity prices (4 to 12 Us cents/kWh, depends on the consumption) are relatively high and promise better days for utilisation of solar energy.

26 kWp will be installed on one multi-family house in the same area as Holmen/Grynnan. In this project PV modules will be integrated in a freestanding sunshade in front of the south faqade and on the roof. From the very beginning the architecturally constraints were finding an application where the PV modules will be heavily exposed. A real-estate company, renting out the apartments, will own the building.

3.3 Ekoviikki, Finland

24 kWp are installed on one multi-family house in a new residential area close to Helsinki city centre. Special considerations have been given to ecological and sustainable planning principles. The PV modules are installed in the balcony balustrades acting as shading devices. In addition to this double function feature, an IT-approach has been taken for the management of the system.

3.4 NCC Head office, Finland

15 kWp will be installed on the roof and partly integrated in the windows of the new NCC head office building in Helsinki. The modules will face east and south. The project will demonstrate how PV can be incorporated into a modern high-class office building fulfilling the aesthetic demands. This building will give experiences about PV installations and effectiveness of modules at such high latitudes as Helsinki.

Despite high initial costs, Solar Home Systems (SHS) are emerging as an attractive option in the face of costly or unreliable alternatives and escalating grid power tariffs. A growing number of households are therefore turning to SHS as a matter of necessity and convenience in Karnataka, a southern state of India. An initial barrier to the growth of SHS was the lack of widespread service infrastructure for PV products and systems. This issue began to be addressed with the establishment of solar rural electrification companies, or mini utilities, in the 1990s starting with SELCO and then followed by Shell Solar and others. However, despite being competitive in the long term, the high up-front costs of SHS, coupled with the reluctance of banks to finance an unfamiliar product, has proved a major barrier to the adoption of this technology. Beginning in 2002 a UNEP programme was formulated to address these issues, with support from the UN Foundation and the Shell Foundation. A study carried out during the programme’s planning phase indicated the following cost profile for various decentralized options available to Karnataka households.

Note: 1 USD = Rupees 45 (approx.)

Although SHS costs are competitive over the long term, since most potential users lack access to credit, they cannot afford to pay up-front for the twenty years of electricity supply that a PV system can provide. It was thus clear that there was a real need to improve access to credit to finance this clean energy option, linking the repayment to their paying capacity and existing energy expenditures.

Although solar home systems can provide a reliable and cost-effective electricity service, they have yet to be established as a mainstream electrification technology, in part due to limited access to financing. India has a well-developed rural banking infrastructure, although its links to the renewable energy sector had yet to be consolidated. It was therefore concluded that a short-term intervention was needed — to address the issue of risk perception by banks, to increase consumer access to credit, and initially to lower the cost of this credit. Once these key barriers are addressed, it is expected that the market will begin to expand without further external support. Therefore, the objective of the programme is to help Indian banking partners develop lending portfolios specifically targeted at financing solar home systems in poorly served regions of South India. It was also decided to keep the focus of the programme on the poor in rural and semi-urban areas, who bear the brunt of power shortages and have limited access to expensive alternatives. It is expected that the long-term result of the programme will be improved
access to modern and clean electricity services for poorly served rural and peri-urban Indian households and small enterprises. The programme is also attempting to contribute to poverty alleviation efforts by the Government of India with a strategy to reach the poor through both local Grameen banks and group lending via Self Help Groups (SHGs). Increased confidence and lending for solar electrification services would mean the expansion of sustainable energy in South India.

Cooling of linear geometries present a greater challenge than for single-cell geometries, and both active and passive cooling have been employed in these systems. Florschuetz

[9]

uses his cost-efficiency model to assess both active and passive cooling options for a linear geometry. He suggests that a plane heat sink would be sufficient for very low concentration levels (less than 5 suns) and a finned one would work for higher levels (10 suns). With reliable winds, these systems could work under slightly higher concentrations. The trough-type photovoltaic concentrator EUCLIDES in Spain [10], with a concentration level of about 30 suns, is cooled by a lightweight aluminium-finned heat sink. The fin optimisation resulted in fins to be 1 mm thick, 140 mm long and spaced about 10 mm apart. A costly manufacturing method was needed which means the heat sink is projected to contribute to more than 15% of the total cost of an EUCLIDES-type plant, while photovoltaic modules and the mirrors contribute around 12% and 11%, respectively.

Edenburn [5] suggests using a "finned mast" (Figure 2) to cool a linear trough design where cells are mounted in a V-type geometry with concentration levels up to 40 suns. He found passive cooling of a linear design to be much more expensive than for a single cell

design and the suggested configuration not to be cost-efficient. Filling the cavity of the "mast" with an evaporative fluid that would work as a thermosyphon to transport heat away from the cells at a very low temperature differential is suggested as a possible improvement. This is further explored by Feldman et al. [11] on a concentration ratio of about 24 suns. With benzene as the working fluid, this gives a maximum evaporator surface temperature of about 140 °C. Outdoor testing shows that the operating temperature is a strong function of wind speed, and less of ambient temperature, wind direction and mast tilt angle. A linear, trough-like system which uses heat pipes for cooling is described by Akbarzadeh and Wadowski [12]. Each cell is mounted vertically on the end of a thermosyphon, which is made of a flattened copper pipe with a finned condenser area. The system is designed for a concentration level of 20 suns, and the cell temperature is reported not to rise above 46 oC on a sunny day, as opposed to 84 °C in the same conditions but without fluid in the cooling system. Florschuetz [9] considers cooling a strip of cells actively by either forced air through multiple passages or water flow through a single passage. Forced air cooling results in a substantial temperature gradient along the cells due to the low heat capacity of air. The required pumping power is also quite large compared to the effective cooling. For these reasons, forced air cooling does not seem to be a viable alternative.

Water cooling, on the other hand, permits operation at much higher concentration levels [9]. Edenburn [5] found active cooling was found to be more cost-efficient than passive cooling in his linear design described above. An actively cooled system, where the cooling methods considered consist of various geometries of coolant flow through extruded channels, is described by O’Leary and Clements [14]. An optimal geometry is suggested based on maximum net collector output versus coolant flow. Because the rate of decrease in thermal resistance drops as the mass flow increases, and the required pumping power increases with increased flow rate, an optimum flow rate can be found for a given system. Russell [13] has patented a heat pipe cooling system where linear Fresnel lenses focus the light onto strings of cells mounted along the length of heat pipes of circular cross­section (Figure 3). Several pipes are mounted next to each other to form a panel. The heat pipe has an internal wick that pulls the liquid up to the heated surface. Thermal energy is extracted from the heat pipe by an internal coolant circuit, where inlet and outlet is on the same pipe end, ensuring a uniform temperature along the pipe. The CHAPS system at the Australian National University [15] is a linear trough system with a concentration of 37 suns where the row of cells is cooled by liquid flow through an internally finned aluminum
pipe. Under typical operating conditions, the thermal efficiency is 57% and the electrical efficiency is 11% for the prototype collector.

These results contradict existing opinion that for fabrication of silicon sutable for PV cells pure hydrogen or pure neutral gases or vacuum are strictly required. And that for purification of silicon from boron metallurgical methods are not suitable. Obtained results cannot be explainen in terms of traditional understanding of semiconductor silicon production. Explanation of this phenomena one has to search in specific peculirities of the considered process.

The process can be presented as following (fig. 1 ).

Crystallization process occurs on a liquid — solid border. In this case solidified material properties are determined not only by processes at the front of crystallizftion, but by processes at liquid — gas phase frontier as well.

Energy for the process in form of concentrated sunlight flow is transfered to the surface of the melted zone. Therefore, melt temperature near the front of crystallization will be near the Si — melting temperature (namely 1412 oC).

At the same time the temperature at the liquid-gas phase border will be much higher. Thereby the gradient of temperature between a free surface of melted zone and front of crystallization is formed.

Crystallization process occurs on a liquid — solid border. In this case solidified material properties are determined not only by processes at front of crystallizftion, but by processes at liquid — gas phase frontier as well.

Energy for the process in form of concentrated sunlight flow is transfered to the surface of the melted zone. Therefore, melt temperature near the front of crystallization will be closed to the Si-melting temperature (namely 1412 o C). At the same time the temperature at the liquid-gas phase border will be much higher. Thereby the gradient of temperature between a free surface of melted zone and front of crystallization is formed.

On the other hand, the situation on an interface liquid — gas phase will be defined not only by processes of interaction of the fused silicon and its vapor at near surface areas of a gas phase with components of the air environment (oxygen, nitrogen, a moisture) but also by processes of interaction of a surface of the fused silicon with the concentrated sunlight. Therefore one can assume that gas phase composition in a thin layer adjoining to melted silicon will be depend upon not only the diagrame of condition of a comlex system consisting of oxigen-nitrogen-mousture-carbon dioxide-impurities. Very important role can play mechanism of interraction of concentrated solar radiation with a fused silicon surface itself and adjacent to the surface thin gas phase layer.

In these conditions it is possible to expect existence of components not only in atomic, but also in ionized state, capable to active interaction. In this case the conditions arising on the surface can be compared to conditions on a surface of the fused silicon subjected plasma processing.

Distinctive feature of the silicon obtaining process under influence of the concentrated sunlight is the opportunity for fabrication of high quality ingots directly on open air. It allows to lower expenses for expendable materials and to simplify a design of installation.

It is not enough received experimental data for identification of the processes occures in these conditions, and chemical compounds formed in this case.

Probably the process of impurities removal in the given conditions could be explained within the framework of the mechanisms described in [4].

Purification of crystallized silicon under the considered circumstances occurs in two ways:

1- cleaning due to segregation phenomena on border liquid-solid from impurity with low coefficiet of distribution;

2- cleaning due to removal of impurities from a bath of melt into a gas phase through liquid — gas phase interface as volatile substances.

Removal of impurities on both specified ways may be intensified by active mixing within melted zone.

As a result impurities which are concentrating in liquid phase near the border with solidifized silucon because of segregation will be more actively removed from the front of solidification into a volume of liquid silicon, and impurities which are removing into gas phase as a volatile components come from volume to the border with gas phase with higher velocity.

It is obvious, that realization of active mixing in the liquid drop formed on an end face of a growing crystal is extremely difficult, practically impracticable problem because the volume and the form of a bath melt at an end face of an ingot are rather critical parameters for growing of homogeneous on diameter and electrophysical parameters ingots.

Any influences on volume of the fused silicon drop result or to it spilling, or in change of the form of obtained ingots.

The technological processes realized in laboratory scale (solar heating in the concentrator in diameter of 3 m and plasma heating with application of energy sources up to 100 kw) do not allow to use them for large-scale SOG-Si manufacture.

Werner Hiller, Technische Universitat Chemnitz, D-09107 Chemnitz

Udo Rindelhardt, Forschungszentrum Rossendorf e. V., PF 510119, D-01314 Dresden

Ingo Voigtlander, Solaris-VerwaltungsGmbH, 09116 Chemnitz

Even in former East Germany, photovoltaic was being used increasingly for generating electricity. Through weaker buying power the absolute numbers are far lower than in the western federal states, but a series of remarkable results was achieved nonetheless. This paper discusses the developments in the federal state Saxony.

It is based on long term results on selected photo-voltaic plants as well as data recorded by the regional electricity supplier Energieversorgung Ostsachsen (ESAG), Dresden, in 2002 and 2003 [1].

Development of installed power and the systems engineering

In 1990, the first (and only) photo-voltaic power system (PVS) of the GDR (East Germany) was connected with the ESAG network (East Saxony) in Oberseifersdorf. From 1992 to 1994, in the frame of the German 1000-roofs-program 150 PVS with a total power of 523 kW followed. According to the conditions of this program these PVS had an power between 1 and 5 kW. This program was intended to test various technologies, as well as to attempt to standardize the PVS design. Modules from about 10 European manufacturers came to be used; thereby inverters with various designs and manufacturers were utilized. As at that time the predominant tendency was to run the PV-generator in the extra-low voltage range (i. e. <110V), several PVS, in particular the larger ones, showed many parallel strings (up to 20 and more).

In 1994 the first larger plant was built at the Kirnitzschtalbahn near Bad Schandau. This PVS had an output of 40 kW and is still the largest PVS in the ESAG net. Between 1995 and 1999, growth stagnated in PVS. Remarkable growth occurred only with the implementation of the EEG as well as the 100,000-roofs-program did in the year 2000. Figure 1 shows the development in the net of the regional supplier ESAG until the end of 2003. In the frame of the 100,000-roofs-program totally 405 pVs with a power of 1,5 MW were put into operation in Saxony. The average PV power plant capacity has not changed in recent years, when compared with the older PVS; it lies around 3-4 kW. Even the number of larger PV power plants, which were mostly built by investors, has remained small. The power of 100 kW has only two times exceeded, so far.

For the newer PVS, the transition to the (one-)string-concept is technically characteristic. Through the higher admissible generator voltages and the use of string-inverters, the cabling is much simplified. The market leader SMA with its model SunnyBoy also clearly dominates in Saxony among inverters. Conversely, since the year 2000 a noticeable number of new modules has appeared on the market, even from smaller manufacturers. Modules of the Dresden firm Solarwatt alone are represented in many PVS; only Siemens (now Shell), Kyocera and ASE (now Schott Solar) are worth mentioning alongside. Other PVS are divided among 20 other manufacturers. A detailed analysis of the results of each module would not be meaningful, since even recently similar modules use different solar cells, depending on the manufacturer [2]. Altogether, about 1000 photovoltaic power plants were being used in Saxony at the end of 2003, with a total capacity of about 4 MW.

year

Figure 1: Development of grid connected PVS in the ESAG net