Category Archives: SonSolar

Solar Cell Structures in the Near and Distant Future

Many specialists share our opinion that in the near future a change of paradigma will occur in the solar cell production. It means that instead of elemental semiconductors, compound semiconductors will be used as solar cell materials [3]. The indirect energy band transition of silicon is not really suitable for optoelectronic devices. The reasons for using it in the fabrication of solar cells are: it has a stable technology and the relaively low price. The amorphous silicon is a more suitable material, because there is no longdistance orderlines of atoms, so the fine energy structures are undefined. The technology of amorphous silicon is made with chemical vapour deposition or sputtering. Its band gap is strongly technology dependent. High efficiency solar cells can be produced from direct band structure materials e. g. from galliumarsenide. For the selection of suitable semiconductor materials their electronic band structure has to be known. It is also important to know the absorption coefficients of these semiconductor materials. The most efficient solar cells are made from galliumarsenide, their efficiency is over forty percent. In the case of latter materials instead of the pn-junction one can use the built-in electronic field generated by different layers (so-called heterostructures) which are grown above each other, by metal-semiconductor interface (so-called Schottky junction) or by electrolyte junction. These materials are e. g. cadmiuntellurid, cooper-indium-diselenide and the above mentioned amorpous silicon or silicon- germanium. Because of the high absorption coefficience of the above materials thinner absorption layer can be used, too. These structures can be produced with different thin layer technics. Some of these materials have bad transport properties, therefore on these materials there are grown wide band gap, transparent and well conducting materials. They are e. g. zincoxid, tindioxid. These so-called windows materials serve not only as a transparent electrode but as antireflection coating and heat mirror, energy efficient window, as well. The window layers can be produced by thin layer technics, too.

Activities for the change

A great deal needs to be done to overcome the main problems in the development of renewable energy sector. The national RES strategy places specific obligations on the Government, while specifying tasks for the Ministers of several sectors.

The government strategy is to be evaluated every three years and recommendations concerning necessary changes and solutions will be proposed. A detailed inventory of renewable energy installations in Poland will be carried out and the results published in Statistics Yearly. A database of available renewable technologies should be created.

Tasks to implement the strategy include not only organisational activities within the Government, but legal actions such as executive regulations, assistance provided to the local and regional authorities in the preparation of energy plans, simplification of licensing procedures for electricity generation from RES etc.

As instruments enhancing economic viability of RES in the initial phase of the implementation of investments, specific funds are allocated from national and foreign institutions. Financial support for beneficiares and investors in the form of grants or preferential loans is available, though with some difficulty. National institutions such as: National Fund for Environmental Protection and Water Economy (NFOSiGW), Regional Funds for Environmental Protection (WFOS), Bank of Environmental Protection (BOS), EcoFund Foundation (EKOFUNDUSZ), Thermo-modernisation Foundation, Foundation for Support Programs for Agriculture (FaPa) and Techniques and Technology Agency (ATT) are engaged in allocation funds to RES purposes. In the framework of international co­operation EU pre-accession funds (ISPA, SAPARD) and PHARE have been launched. Participation of Polish partners in research and demonstration projects of European Union (FP5, FP6, ALTENER II, SYNERGY) is a support and good possibility to implement new techniques and technologies. Bilateral funds and others could be of assistance to Polish investors. These instruments should be resorted to until renewable energy sector is fully competitive on the market.

It must be emphasised that the development of the green sector would be of great benefit to the environment and to the regional and local communities in creating new jobs. And above all, diversification and decentralisation of the Polish Energy sector would contribute to security of energy supply.

Closing the experience gap in the field of PV energy. with training of social, technical, financial and business management skills

Georg Bopp, Sebastian Golz, Felix Holz, Werner Roth, Gisela Vogt
Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr.2, 79110 Freiburg, Germany
Tel +49 (0)761/4588-5228; Fax: +49(0)761/4588-9283; sebastian. goelz@ise. fraunhofer. de


Education, training and awareness raising is recognised to be a main task for the development of markets and technologies. One reason for the failure of many projects and programs of rural electrification attributes to the lack of knowledge, training and competence of participating people at all levels. (International Energy Agency IEA, 2003).

All these alerting experiences advise that different accompanying measures have to be considered in line with designing and implementing solar power systems. Both in grid coupled and off-grid markets cultural, social, economical, organisational, and financial aspects have to be incorporated (Will & Vogt, 2003). Various competencies and skills are required to plan, implement, commission, and promote solar power systems. Therefore the substantial objective of this article is to illustrate the spectrum of relevant training topics, to report from current state of knowledge in two exemplary markets and to describe the profit of customised training programs.

1. Training and further education for comprehensive market support

At all levels of off-grid and rural electrification projects an extensive demand for training can be identified (Vogt, Will, & Sauer, 2003). Investors, politicians, planners, installers, suppliers, users, and service personnel frame the target groups of different training programs. During the last years, the Fraunhofer Institute for Solar Energy Systems ISE has conducted various projects (SUNRISE, SOPRA-RE; SOLTRAIN) to design and to accomplish training concepts for these target groups. Starting from these experiences Fraunhofer ISE offers a broad assortment of programs for further education. The various job training, designed and applied by an interdisciplinary team, cover the following target groups and topics as listed in chart 1:

Study profile

The University of Applied Sciences Nordhausen pursues a fundamental system — oriented education in the domain of development, planning and operation of renewable energy systems. In addition to solid engineering basics the energy — and process-related principles of solar thermal, photovoltaic or wind energy systems and their integration into existing — and here in particular electrical — supply systems takes the centre of the training. Special attentions will be put to renewable energies in the vehicle technology — keyword fuel cell — and to bio energy systems.

Fig.1: System expertise is more than feeding electric energy into the public power supply

Graduates of this study program are to acquire expertise of renewable energy systems. This means for the example of a wind power plant knowledge of the fluid mechanics at the rotor, of the shaft bearing, of the conversion of mechanical into

electrical energy and of the feed of the electric energy into the public power supply system. In order to open the graduates a broad spectrum of vocational possibilities, the training also involves classical power engineering and additional subjects. Latter are for example information and diagnostic systems, management in the energy industry, energy law or the use of recycling materials for power generation.


To meet these requirements, a three-level model (Fig. 2) was developed which clarifies the study contents for the curriculum.

level I: energy sytem

level II: sytem Integration

level III: Implications

Level I: Energy system. The first level deals with basics of power engineering, power converters and energy transport. This covers work and power machines, cooling and heating up to photovoltaic and bio energy systems.

Level II: System inte­gration. The second level concerns with system engineering. This includes technical diagnosis as well as technical management of energy or buildings. Level III: Implications. for example energy law

The ongoing working process

Other organizational problems result by the prevailing conditions given in every day school life. During the working period on the Facharbeit students have to meet their supervising teacher several times to give a report about their work and discuss how to proceed further. But it is hard to find a date when both, teacher and student, have the needed time. That is why you get into a big pressure of time. This is unsatisfactory as well for the student as also for the supervising teacher. I myself had problems of this kind.

Additionally, the missing experience of teachers in guiding a Facharbeit results in many misunderstandings between teachers and students, and in ineffective work.

Sometimes the students have bad luck with their supervising teachers. At the very beginning some teachers say that they will guide a student’s work and afterwards they show no interest at all in this work, or they say that they have no time for the next few months to do anything to help the student, or they let the student work and do not even read during the working period the single text parts the student has written. This all happened to several friends of mine in my grade. In this point I was more lucky.

Successes and insights I won

In spite of all the difficulties I do not regret to have worked on a Facharbeit. Contrarily, I have won a lot of valuable insights. First, I have learnt a lot about a topic of my interest. Second, I performed a research work that requires another way of working, thinking, organizing and structuring as usual school work. Especially the kind of presentation and to work out a paper in scientific manner are valuable experiences far beyond of the skills usually learnt at school.

A special highlight was the participation at the competition “Jugend forscht” where I presented together with my sister Inge a part of my work. We received a lot of acknowledgements: the first price in the field of technique, the special price for environmental technique and the price for innovative work done by females. In the higher level we were proud to win a practicum at the department of inorganic chemistry at the university in Mainz.

A European Master run by renewables-experienced universities

The EUREC member network of renewable energy research centres covering all EU member states, the European Master in Renewable Energy has been designed in cooperation with nine universities in five EU countries, with each institution adding its specialised technological knowledge to the programme.

The core is taught by universities having a strong record in general renewable energy technology teaching: Students can follow the core alternatively at the following universities:

■ Loughborough University, UK (language: English)

■ Carl von Ossietzky University at Oldenburg University, Germany (language: English)

■ Universidad de Zaragoza, Spain (language: Spanish)

■ Ecole des Mines de Paris at Sophia Antipolis (Nice), France (language: French) The core lasts from October to December and ends with a series of exams.

The specialisations take place at universities with a specific focus on one renewables technology: As specialisations, all taught in English, are available :

■ Wind energy — at the National Technical University of Athens, Greece

■ Biomass — at Universidad de Zaragoza, Spain

■ Photovoltaics — at University of Northumbria at Newcastle, UK

■ Hybrid systems — at Kassel University, Germany

■ Solar buildings — at University of Athens, Greece

The specialisation lasts from January to April and ends with a series of theory and practical exams.

In later years, it is expected that the list of specialisations available will grow. A specialisation in water power (to include micro-hydro, wave and tidal power) would be especially welcome and relevant as this technology is expected to soon reach a commercial stage.

A truly European course

Different to the few other existing Master-level RE courses, the European RE Master plays the European card: students are required to study in at least two different European countries. This feature reflects the fact that there is at present a tendency to cross national borders and set up foreign representations or carry out project work abroad, even for small and medium RE companies. Clearly, intercultural awareness and foreign languages are assets that present a plus for any employer today.

Cost of avoided carbon

A general figure of merit for a renewable-fossil hybrid system designed to reduce carbon dioxide emissions ("avoided carbon") is the resultant cost of one ton of carbon avoided (CCA). As before, it relies on the comparison of the hybrid system to an efficient, practical fossil fired power system, generally the baseline standard system. It is the same standard as for GREF and FCR. A particular cost parameter is obtained, based on essential information on both the costs and performance summary of both systems. As such it is a combined cost-performance parameter:


COST OF AVOIDED CARBON (CCA) ($/ton C) by hybrid system =


The parameter COST of output means here the annual system product cost, including both the annualized capital and operation costs ($/MWhe). The quantity of avoided carbon is equal to the GREF (dimensionless) times the specific fuel carbon consumption of the baseline standard system (ton/MWhe).

Equation 3 is useful in many ways. It can be used for observing functional tradeoffs and engineering optimization of system design. Also, for monitoring the CCA as a function of the number of operation hours in the year, electricity price-tariffs and other data. As well, for deriving the minimum cost of avoided carbon as a function of the number of annual operation hours and relevant variables.


Renewable-hybrid systems have the potential of playing a decisive role in massive supply of renewable energy in the near-term. However, the hybridization of renewable energy with fuel — fired generators has to be designed and operated properly. The issue of baseline standards is elucidated. Hybrid systems are analyzed by use of environmental parameters, the fuel consumption ratio (FCR) and a new parameter, the green energy fraction (GREF). They are numerically illustrated for several solar electricity systems. The FCR and REF establish vital metrics for environmental system evaluation by providing a summation figure for the overall fuel avoidance of the whole hybrid power system, simple or complex, for the full or part of the year. Together with the CCA (cost of carbon avoided, $/ton C) parameter, the three metrics (all defined with the same environmental reference standard), establish a unified technology — evaluation criterion, or figure of merit, enabling helpful assessments of various systems on an equal basis. This allows the comparative evaluation of renewable energy plants for upright clean (green) energy. The metrics and related equations provide useful yardsticks for project evaluation and for guidance in planning improved, cost effective, sustainable solar and other renewable-hybrids systems. They also provide generalized evaluation tools for emissions verification, which is necessary for green energy incentives management.


[1] Swezey, B., Bird, L. Buying green power… you really can make a difference. Solar Today, Jan/Feb 2003, pp.28-31 http//www. eere. energy. gov/greenpower/pdf/Buying_Green

[2] Geyer, M. Panel 1 Briefing materials on status of major project opportunities, Internatio Executive Conference on Expanding the Market for CSP, 19-20 June 2002, Berlin, German p.4

[3] Wholgemuth N, Missfeldt F. The Kyoto mechanism and the prospects for renewable technologies. Solar Energy 2000; 69(4):305-314

[4] Svoboda P. A.,. Solar boiler for a 100 MW integrated solar combined cycle system.

In: Faiman, D. (Ed.), Proceedings of 7th Sede Boqer Symposium on Electricity Production, 18-20 March, 1996, Blaustein Inst., Sede Boqer, Ben-Gurion University, Beer-Sheva, pp.125-128.

The St. Louis Fair (1904) and the Pyrheliophero

2.1- Preliminary work

His next serious attempt was carried out in Lisbon. This second patented invention, a tracking section of a paraboloid and a solar furnace (patents [11,12,13]- basically translations of each other) can be seen in some of the figures reproduced below. The remarkable thing about this invention is the fact that it achieves a very high concentration factor, with full separation of the optics from the furnace.

Fig. 4: cut of the high temperature furnace.

A conceptual leap, as explained in the patent, is the fact that in previous 3D solutions radiation got to the focal zone from all sides, never allowing for sufficient concentration to be achieved on its outside walls (see Mouchot, Fig. 1), while taking only a paraboloidal sector allows for the maximum concentration achievable with it to be redirected into furnace Z for direct effect on the substances to process or heat. The built in flexibility of motion always ensures that reflected rays are directed at all times into the furnace Z. In modern terms we can see that the conical entrance aperture to the furnace, ensures a second stage concentration, taking care of reflection and tracking inaccuracies (spillage).

The complete set of drawings show a large number of novel possible combinations of mirrors and furnaces, their relative motions and sun tracking capabilities. Their thorough discussion is beyond the scope of this paper, but their careful consideration, even without any dedicated explanation, is very instructive and enjoyable. The solution of two concentrating mirrors, back to back, moving on the same tracking structure (for instance, drawing 7 within Fig. 6) and the other extreme where the optics and the furnace are combined in a unique set — no rails (drawing 11 of Fig.6) are very interesting. These

Fig.5: Excerpts from Patents [11,12,13]

Fig.6 Excerpts from Patents [11,12,13]

drawings show different solutions to track the sun in azimuth and elevation. Use is made of rotation around centre poles to compensate for the Earth’s rotation, with the furnace sometimes moving in a separate fashion, on rails, or as one with the mirror, but always with the possibility of adjusting to the sun’s elevation. But none of these movements could be made in fully automatic way in a modern sense, i. e, in unattended operation, since that would require modern day combinations of tracking motors and sun sensors.

Experiments with one of the possible configurations described in these patents (presumably one with the furnace going on a circular rail) were carried out in Lisbon (March/April 1902). Inaccuracies in the design and mechanical problems, plagued the
prototype. The day of the public demonstration the concentrated radiation destroyed the supporting structure and it was a fiasco!

It must be then that Father Himalaya sought about, quite beyond the fact that he needed to correct the faults with this prototype, that he needed a new idea for a truly practical system able to track the sun, unattended, at maximum concentration. A simple clock mechanism would do the trick, but that required a radically new design. That became the Pyreheliophero, to be described next.

Fig7: The prototype built for the Lisbon tests with what looks like the furnace in the


Ecological and other Architectural Applications

The thickness of active semiconductor part of solar cells spread from one to some hundred microns at most. These photo devices have to be packaged to protect them from damage and to make them rigid. A possible packaging construction is shown by Figure. The device is cased in plastic foil between two safety glasses. The front glass
provides protection and must have good transparency, the back glass serves as a holding structure and decreases the heat stress. There are metal plastic back layer devices, but in these cases the thermal expansion causes problems. The frame can be aluminium and other light metal. Fixing is done by these frames but there are photovoltaic devices without frame, too. Unit panels can be connected in series and in parallel, depending on the requirements. The form and size of unit panels depend on the solar cell technology (wafer, ribbon etc.), and it influences the image of the modules. The image of the solar module depends on the materials for colour and on the density and form of the collection electrode for morphology. The size of the module is determined by the size and number of the unit panels it contains.

Fig. 3. Grid connected photovoltaic system

Buildings are perfectly suitable for the placement of solar cells (Fig. 3.) [4, 6]. Solar cells can be looked at as a unit of building construction, which can be used well in architecture. Solar cell can be mounted on the flat roof to be used only for energy production and protection against radiant heat, having no other building construction

effect (Fig. 4.). The image of the building will not be influenced, because it cannot be seen from below. The weight of the wind and of the snow can be taken over simply by the holding apparatus. The only requirement is that the modules should not shade each other even at low position of the sun. Photovoltaic cells on the high — pitched roof and on the facade have aesthetical and building physical influence. It has been already mentioned about the dependence of the colour, form, size and morphology. Mounted solar cells give on the building surface an air shell, which in the summer protects against radiant heat and in the winter improves the thermal isolation of the roof. In case of mounting it on the roof both wind pressure and suck should be considered. A special roof tile which contains the holding apparatus must be fixed to the rafter. The relationship between the building tectonics and facade mounted solar cells is shown by Fig. 4. In this case the windows plain and the solar cell plain coincide. The distances betweenfloors of glass-only buildings can be used for energy production

Concluding remarks

To meet the targets set in the Development Strategy of Renewable Energy Sector envisaging that by the end of the decade 7.5 percent of energy generated in Poland will be derived from renewable sources, work is carried on and discussions are held to create important legislation: the RES act. Our main goal should be to create a RES market, which in our economic reality is far from simple. The strong coal and energy lobby, which represents large power plants, determines the conditions of operating in this sector. Thus it is a political necessity to find a way to reconcile differences and solve conflicts among all the interested parties.

To meet its official international obligations regarding the reduction of pollution caused by greenhouse gases emissions, Poland has to produce more renewable energy. This can be done through increasing the utilisation of environmentally clean energy from RES such as solar, biomass, wind energy, geothermal and hydropower. Such energy policies will not only contribute to the reduction of environmental pollution, but will also bring significant results, measured in financial benefits for the country and in better health of the citizens in the future.


White Paper for a Community Strategy and Action Plan: Energy for the Future: Renewable Sources of Energy. COM (97) 599 (final) of 26th Nov. 1997.

Directive 2001/77/EC On the Promotion of Electricity Produced from Renewable Energy Sources in the Internal Electricity Market. Official Journal of the European Communities 27.10.2001. L 283/33









[4] [11]


Development Strategy of Renewable Energy Sector adopted by the Council of Ministries on 5th September 2000 and passed by the Parliament on 23rd August 2001. Parliament No 2215 (2000)

The treaty of Accession of Czech Republic, the Republic of Estonia, the Republic of Cyprus, the Republic of Latvia, the Republic of Lithuania, the Republic of Hungary, the Republic of Malta, the Republic of Poland, the Republic of Slovenia and the Slovak Republic of 31st January 2003 No AA 2/03 (MD 171/6/02 REV 6)

Anna Oniszk-Poptawska. Dostosowanie polskiego prawa do prawa UE w zakresie wykorzystania odnawialnych zrodet energii. Gospodarka paliwami i energiq.


White Paper on European Transport Policy. COM (2001) 370 of 12th Sept. 2001. Directive 2002/91/EC of 16.12.2002. Energy Performance of Buildings.

Proposal for a Directive 96/61/EC of 23.10.2001. Greenhouse Gas Emission Allowance Trading.

Directive 2003/30/EC of 8.05.2003. The Promotion and Use of Biofuels in Transport.

Community Guidelines on State Aid for Environmental Protection. 2001/C 37/03. Notes on Poland’s Energy Policy to 2020 (Ministry of Economy, approved by Council of Ministries on 22nd February 2000)

Sustainable Development Strategy for Poland to 2025 (Ministry of Environment. 2000)

The Energy Law (Council of Ministries.1997. Dz. U. 1997. No 54. p.348)









The Environmental Protection Act (Council of Ministries.2001. Dz. U. 01. No 62. p.627)

The RES Act (in preparation)

The Quota Obligation Ordinance of Purchasing RES Electricity (Ministry of Economy on 15th December 2000. Dz. U. 2000. No 122. p.1336)

The Amendments to the Quota Obligation Ordinance (Ministry of Economy. 2003. Project on 15th December 2000. Dz. U. No 104. p. 971 on 13th June 2003.)

IEA Statistics. Renewables Information 2003 Le Barometre EurObserv’er (Systemes Solaires) 2003.

Grzegorz Wisniewski. Zrodta energii odnawialnej w Polsce: stan obecny, zarys prawny oraz mozliwosci rynkowe. Konf. Min. of Environment. On 16th January 2004. (Promotion of the European Experience of Renewable Energy Sources Development and Climate Change Commitments in the New Member States and the Candidate Countries: A High Level Approach).