Category Archives: SonSolar

Integrated solar combined cycle systems (ISCCS)

The integration of a solar field with a combined cycle (CC) power plant seems to offer several advantages to solar power and also to other renewable energy sources. However, careful thought should be given to particular design features in order to circumvent sizeable, inherent green energy losses. The CC is an optimised system and upon integration with solar it is rendered out of optimum and may lose some percentage of its inherent high efficiency. For instance, it occurs upon combining two or more power-block subsystems, which operate with different capacities and varying fuel injection modes. Every percent of CC efficiency-loss due to the integration induces a considerably magnified effect on the green energy output of the system. For example, consider a 100 MW CC operating 8000 hours a year, to be integrated with a solar trough power plant capable of operating 2000 hours a year at 10 MW output (when operating alone with its own 10 MW engine). When the latter is integrated with the CC, a single percent loss of the CC annual output amounts to 8 GWh. This loss may be said to "eat up” a substantial portion of the 20 GWh solar plant green capability output. Any efficiency loss of a fuel fired engine is a green energy loss, because now more fuel has to be burnt to supply the same amount of the electricity prior to the integration.

In addition, another loss takes place during the solar hours. As the temperature of the working fluid produced by the solar field is often too low for accommodating the design conditions of the steam-cycle part of the CC, "back-up” fuel firing is generally resorted to, which is a severe, inefficient use of fuel [4]. It means a definite green energy loss. Every single percent of CC efficiency loss will be magnified as mentioned above, and is to be charged to the solar energy account.

Also, because site requirements for the solar field and the CC are in conflict, this brings about another source of annual CC output loss. The CC conversion efficiency is degraded due to the usual higher ambient temperature (and lower air density) at high solar radiation sites, which are beneficial to solar systems [4]. This might translate into additional percentage of solar green output loss.

There may be ISCCS or other solar-fuel hybrids configurations that make sense, but significant care and study must be taken in the integration design, otherwise it is possible to end up with a plant that uses more fuel per kWhe output than the fossil-only plant. Green energy considerations and analysis should help.

The role of the standard reference for defining avoided fuel (emissions reduction) or green energy is essential for enabling fruitful analysis of systems and for directing research options towards improved systems. It should be emphasized that in most cases the standards (references) are independent of the equipment characteristics of the system under examination.

A highly innovative, high temperature, high. concentration, solar optical system at the turn of the. nineteenth century. The Pyrheliophoro

by

Manuel Collares Pereira (Coordinator Researcher)

INETI, Renewable Energies Department,

Edificio G, Az. dos Lameiros,1649-038
Lisbon, Portugal
collares. pereira@ineti. pt

I-Introduction

The ISES initiative of recovering the recent and not so recent history of solar energy and its pioneers has prompted several investigations into the past. Several gems of ingenuity, scientific and technical capacity, way ahead of their time, have been uncovered. The one to be described in this paper is one of those, having produced quite a stir in its own time. It was soon to be forgotten given that the World in transition from the nineteenth to the twentieth century, was about to embark in the "oil race", and solar energy was not even given half a chance to be "in the race" at that time.

Father Himalaya 1902

The man behind the work described here was a truly remarkable personality, a self made scientist, a catholic priest, without a proper (academic) scientific training. Through life he tried to compensate for it by his constant travels, in particular to France (mainly Paris), but also to many other scientific relevant European Countries, in particular England and Germany and to the U. S., interacting and even studying with top notch people of his day, like Berthelot, Moissan, Violle, among others.

His name was Manuel Antonio Gomes, soon nicknamed by a friend as Himalaya, because he was taller than his colleagues. He added this nickname to his name and was ( and still only is) known by it. He was born in 1868, in Cendufe, a small village in the North of Portugal. He was one in a large family with little economical resources. As usual in those days and in such circumstances, he entered the Seminary, as a way to study and to succeed in life. He was ordained priest, and a practicing priest he was until his last day (in 1933), in spite of his very controversial life style, unorthodox views of the Church and its dogmas, the very critical position he had on items like the forced celibacy of priests and its constant fight for a more socially responsible and committed Church, embracing as he did the truly liberal, republican, socialistic and idealistic ideas of the day.

He was quite famous in his lifetime and respected for his achievements. He became member of the Portuguese Science Academy and had at least an attentive audience amidst the politicians of that day.

This paper is dedicated to his crown achievement in the field of optics and solar thermal, but he is also known for many other original contributions, for which he got
a truly large number of patents, in Europe and in the U. S.. and, most notably, the Grand Prix at the St. Louis World Exhibition of 1904.

He really lacked a proper high level training in Physics and other basic sciences, which would have been very good to shape his enormous qualities has an experimentalist and as a mechanical genius. His training in chemistry was probably deeper (his interaction with Berthelot and other important chemists certainly had a crucial part in that). Among other things he invented and developed an explosive ( a chlorine based, smokeless-powder, the himalayite — said to be more powerful, easier and safer to use than dynamite) which he put to many pacific usages, in particular in agriculture and in quarries [48]. His explosive was sought after by several armies of the World (U. S., German, Portuguese, etc.) and his involvement with some of those is still more or less shrouded in mystery. Another one of his inventions, deserving a mention in this brief account, is the one of a rotary steam engine, looking very much like the rotary engines first proposed-and developed — many years after[49] .

He was also a Nature lover, a self trained biologist, a practitioner of natural medicine, but, most remarkably, he was an ecologist "avant la lettre", an explicit and stout advocate of sustainable development, through a proper balance of Humanity, its needs and Nature, regarded by him not just as a provider but also as an important part of the whole scheme of things. He constantly called for Renewable Energies (solar, hydro, tidal, wave,…) as the means for long term and balanced solutions for the many problems caused by poverty and starvation facing the World of his time and in particular of his own country. He had, in this regard, a truly modern view of the World and of the place of Man in Nature, a view which is taking another hundred years to affirm itself.

This note and comments are largely based on the remarkable book [1] written by Prof. Jacinto Rodrigues, which is now about to be translated in several languages and being used as the basis for a movie on the extraordinary life of this towering man and personality.

The Fundamentals and the Conventional Structures

The from 0.5 to 3 eV range is an important part of solar energy. Photons in this range can be used by special semiconductor devices for the production of electrical

Fig. 1. Structure of a polycrystalline silicon based solar cell

energy. Photons of suitable energy generate charge carrier pairs in the semiconductor. Making use of built-in electrical space the charge carriers can be separated and may do electrical work. One of the most frequently used solar cell types can be manufactured from polycrystalline (Fig. 1.) and amorpous (Fig. 2.) silicon with pn-junction. The current — voltage characteristics of the junction is well known. The efficiency of the solar cell is given by the quotient the highest available electrical power and the power of incident solar rays. Typical efficiency for commercially available — e. g. in architecture — used silicon based solar cells is 10 to 15 percent. The

solar cell is characterized by another parameter called fill factor, which describes the form of the current-voltage curve, and it is between 0.7 and 0.8 for a well-made commercial cell. How can the efficiency of the solar cell be improved? There is a very important factor: the energy band gap.

Fig. 2. Structure of an amorphous silicon based solar cell

Transport behaviour of the carrier in different materials is another important parameter. The carrier which is generated outside the space — charge region should the junction by diffusion before recombination. This is realized in silicon, in which the diffusion length of electrons in the p-region is around hundred microns. The efficiency can be improved with an antireflection layer on the surface.

Efficiency is influenced by the following parameters: band gap, absorption and diffusion length.

Barriers to the development of renewable energy sector

In view of the growing interest in renewables, there are still a number of barriers considerably hindering the development of RES sector. These include: legal, financial and
economical barriers, lack of suitable information, difficult access to new equipment and technologies, educational barrier and even barriers arising from landscape protection. Through lack of good legal regulations investors are discouraged from building new installations and reconstructing the existing ones. Insufficient economic mechanisms in the state budget, including tax mechanisms and high costs of investments in facilities, installations and plants in RES sector as well as high costs of renewable energy technologies, make RE investment very expensive. Lack of tax preferences for import and export of equipment and components for the systems utilizing RES is also a considerable problem. All the above as well as a lack of legal and financial consequences for distribution companies impedes meeting quota obligation ordinance to purchase electricity from RES.

There is an urgent need for more information on RES issues, for better dissemination of technical potentials and for companies involved in consulting, designing and manufacturing services, which could offer cost-effective solutions to customers.

A number of education and training programmes should be organized to address the needs of individuals and group users. Good practices and guidelines should be disseminated to RES investors.

What gets in the way of widely implementing RES technologies in Poland is the low cost of energy from fossil fuels. There are no mechanisms to guarantee a stable revenue for independent green power producers. This creates problems particularly for wind power producers, as prices of electricity are not fixed for a longer period-contracts, are valid for one year only and have to be renegotiated every year.

Future training is essential

Since 1997 the concept of the Academies has evolved, providing a growing basis of information focusing on the central aspects that impact on solar building design — including scientific and technical issues; cultural; management; climatic and regional aspects. The intention is to encourage other organisations, also tertiary education institutions, to organise similar events or to include relevant themes on solar building into their core curricula.

This process has started, for example the SAMSA 2002 inspired university lecturers in Mozambique to organize a similar course in Maputo, funded by the Italian Cooperation and promoted by ISES. The event titled “Controlo Ambiental e Energia Renovavel na Arquitectura” was held in October 2003 at the Faculty of Architecture and Physics of the University Eduardo Mondlane, and was attended by more than 100 people.

The SAMSA concept focuses on the Mediterranean basin area, but, as a large section of this area forms part of Europe, it is also closely connected with other European activities and regional training events. In 2004 three similar Academies will be organised by ISES and its partners, as a component of the EC ALTENER supported project “Teaching About

Renewable Energies in Buildings", implemented by several prominent European universities and organisations. This project is also aimed at coordinating the development of web-based downloadable teaching packages, organising the first European Master’s degree in this field and holding three further education training events, namely:

• Rome, Italy:

o Summer Academy for Mediterranean Solar Architecture (SAMSA 2004) o Focus on tools for solar building design in the Mediterranean region. o www. ises. org/samsa2004

• Freiburg, Germany:

o ISES Solar Academy: Integration of Solar Technologies in Building Design (Freiburg 2004)

o Focus on the integration of solar technologies in the design of residential buildings in a temperate to cold climate.

o www. ises. org/freibura2004

• Prague, Czech Republic:

o ISES Solar Academy: Solar Technologies for Building Renovation (SOTERE 2004)

o Focus on the renovation of historically significant buildings using of solar technologies in a temperate to cold climate.

o www. ises. ora/sotere2004

The Academies, promoted by the ISES network, are inter-connected and promote the electronic sharing of data and results on solar architecture aspects, thereby supporting and enhancing the role ofthe European network ofskilled solararchitecture professionals.

5. Conclusion

Professionals — mainly architects and engineers, but also related professions — and students require clear and structured information on the different aspects relating to the application of RETs, EE and solar architecture strategies in the built environment. Experience gained with the SAMSA 2002 and similar events has encouraged the NGOs and universities linked to the ISES network to continue their activities in the formative sector, addressing the growing need for similar capacity building events.

Within the ISES network there is a wide range of expertise available, with a supportive international network, where professionals and students interested in sustainable energy can find mutual interests, and exchange ideas and experiences. ISES will celebrate its 50™ anniversary in 2004 as the oldest and largest NGO that promotes Renewable Energy globally. Many of the Society’s activities have encouraged people to consider sustainable energy issues — a particularly interesting one for solar buildings are the results of the first international solar architecture competition organised in 1957 (Image 3). These results, when compared to solar buildings of today, show that the basic strategies and principles have essentially not changed, but the technologies and materials available today add new and fascinating dimensions to solar buildings.

The results ofthe Academies and the enthusiasm ofthe participants has encouraged ISES to continue these activities as part of its Awareness, Education & Capacity Building

Image 1 — SAMSA 2002 group

SUMMER ACADEMY FOR MEDITERRANEAN SOLAR

ARCHITECTURE

Faculty of Architecture Untvenlty Ы Roma Tre

Image 2: SAMSA 2002 official poster

Image 3: Results ofthe 1957 ISES Architecture competition on CD/DVD

Programme (AEC). The aim is to ensure that a point of reference is established in the field of solar architecture, not only in Europe but also internationally — thereby assisting the experts and professionals to join forces, centralise the information and spread information on solar architecture — relevant both to new building design and building renovation — considering aesthetics and energy consumption (reduction), using clean energy sources as equally important aspects in the design process.

Renewable Energy Engineering

Prof. Dr.-ing. Viktor Wesselak, wesselak@fh-nordhausen. de University of Applied Sciences Nordhausen,

Weinberghof 4, D-99734 Nordhausen, Germany

In WS 2003/04 at the University of Applied Sciences Nordhausen the new study program Renewable Energy Engineering started. It is a combination of the energy related parts of electrical an mechanical engineering, with a clear focus on renewable energy systems. The students graduate as Dipl.-Ing. (FH).

University of Applied Sciences Nordhausen

The University of Applied Sciences Nordhausen is the most recently created university in the region of Thuringia, in the centre of Germany. It was created in 1997 and the first students began their courses on October 1998. Until today seven study programs have been implemented including three engineering study programs: Brownfield and Materials Recycling, Computer Engineering and Renewable Energy Engineering.

With about 1000 students the University of Applied Sciences Nordhausen is quite a small university. This leads to limited numbers of students per study program und ensures that each student benefits from teaching methods which address his or her individual requirements. Beside this attractive study conditions are ensured by a systematic modular study structure combined with the European Credit Transfer System (ECTS) and obligatory language instructions. For further information have a look at our internet presentation (www. fh-nordhausen. de).

Information material

With the help of my father, I also succeeded to get the literature I needed for my work. In general, the search for adequate literature as well as the getting of it is not very easy for students.

First we have to know where and how to seek. Second we have to come to know which literature is understandable for us as students with relatively poor knowledge, and this, often without haven’t yet seen the literature. Third we have to choose out of this a sample that gives us all information we need for our work. And fourth we have to find out if the information given in this material is reliable. For all this, help from experts is needed, and teachers are often overtaxed with this task.

I myself have begun my work with an internet search. You can find much in the internet about future energy issues, especially also very actual information. But it is not good structured, and out of the waste information only a small part is usable for a Facharbeit.

A big problem, especially in future energy issues, is that you haven’t got the guarantee that the facts presented are objective true. Even if you get your information out of serious books (we luckily have a lot of them at home) you cannot be sure if the information given is reliable. Special people who work for the industry or want to sell something may have interest to falsify information. Thus you can find many contradictory reports or fact presentations and you do not know which one you can really trust.

My teacher could not help me in this question. He is not an expert in this field (how could he be?). The only thing I could do, was to collect first all information I could get and compare the single presentations in order to find similar information given by different authorities. But even then you cannot be satisfied because you still do not know if this information is right.

Another point is, that you have to collect much different information in order to get this way just a little security that the information you use in your work is reliable, and also in order to get all the needed information for the work. The internet sources are not enough. So it is necessary to have the possibility to use good libraries which have books about your working theme. But you cannot find such libraries everywhere. Normally only libraries of universities with nature or engineering sciences or have sufficient technical literature. With respect to future energy issues there exists a special financial problem: Actually university libraries in Germany have not got enough financial resources to be all up to date in fields developing as fast as that one of renewable energies.

But even if the desired literature is available in an university library in the surrounding area of your home, there exists a further organizational problem. In Birkenfeld for example the next university library with sufficient literature is about 60 km away, if you travel by car (but the most school students cannot travel by car!).

The library of the Umwelt-Campus Birkenfeld is up to now not completely built up and comparably small. With trains and busses the way is even longer and costs a lot of time. I myself have every day at least until half past three in the afternoon lessons at school, and thus it is nearly impossible to visit a university library.

Course structure

The 12-months programme is divided in three parts, getting progressively more and more practical:

The “core” provides a firm comprehensive background in the key renewable energy technologies (wind, sun, biomass, water). It concentrates on energy production and use and addresses the socio-economic context. Mostly theoretical courses are completed with laboratory workshops.

The “specialisation” focuses on the specific technology and implementation aspects of one renewable energy discipline of the student’s choice: Wind energy, biomass, photovoltaics, hybrid systems, or solar energy in the built environment. In-depth theory classes alternate with extensive practical work in laboratories and testing facilities, while study excursions illustrate real-life implementation.

The project is the opportunity for students to apply and further develop the skills acquired in the technology of their specialisation during a placement in a renewable energy company or a research centre. A tutor from the host company supervises and guides the student during project work, while a second supervisor from the university at which the student will undertake his or her specialisation helps the student with his/her project work.

Industry relevant education

The balanced mix of theoretical and practical courses optimally prepares graduating engineers for jobs in the growing renewable energy industry. Both core and chosen specialisation include laboratory assignments since practical and experimental skills are regarded as important for the potential employers. An extensive 4-months company placement for hands-on project work is an integral part of the programme. It provides students with valuable working experience, while allowing companies to fill their short-term human resources needs and to “try out” potential future employees. Companies are encouraged to contact EUREC Agency with a project proposal they would like to have a trainee for. EUREC Agency then finds trainees for them. All trainees already hold an engineering or other relevant degree and have followed the European Master in RE core and specialisation by the time they enter a company; they are already junior RE experts.

Green energy fraction (GREF) equations

In terms of fuel quantities, the general equation for the green energy fraction (GREF) of a solar power plant system is, by definition,

(1)

GREF = (gr baseline — gr input)/ gr baseline

GREF = 1 — (gr input)/(gr baseline)

Where,

gr input — — total fuel consumption in the hybrid system

in grams per 1kWhe net electrical plant-output (gr/kWhe)

gr baseline — — 160 gr/kWhe, the specific fuel consumption of the chosen reference system (baseline standard), (for visualization, a CC using fuel of around 9000 kcal/kg)

For simplicity, both the hybrid system and the reference power system here use the same fuel. It should be realized that the grams-ratio expressions signify the inverse efficiencies ratio. The use of grams emphasizes the requirement that any fuel used in the plant should be counted and included in the equation.

The concept of fuel avoidance requires to compare the fuel-blended, renewable hybrid system to a baseline standard, which is a real, competing, efficient, non-renewable system, set as reference. On circumstances where CC systems cannot be considered as a useful alternative fuel fired electricity generator, thence the 60% baseline becomes impractical. Then, another a locally competing, fuel-fired, efficient system is to be selected for reference standard. Thus, the 40% Rankine-cycle system may serve as a secondary standard against which solar systems will have to compete. In such a case, because by definition the green energy is a functionally reference-dependent parameter, the resulting value for the green energy fraction will be different.

Transformation of a green energy fraction from one reference standard to another can be performed by

(2)

GREF1/GREFF2 = (B2/B1) (B1-gr)/ (B2-gr))

Where,

GREF1 — — green energy fraction 1 GREF2 — — green energy fraction 2

B1 — — baseline 1- — in gr/kWhe, (reference standard 1)

B2 — — baseline 2- — in gr/kWhe, (reference standard 2)

gr — — the total fuel consumption in grams by the hybrid system, per 1kWhe net

plant electricity output

This equation converts a GREF 1 of baseline 1 to GREF 2 of baseline 2. It is significant for enabling comparison between technologies and systems.

The Pyrheliophoro

II.1- The first steps: the metallic lens

Father Himalaya, from his early days, saw solar energy as means to provide energy not just for the production of hot water or steam, but as a direct means to provide energy for industrial processes, in particular to those associated with materials production or processing, if high enough temperatures could be achieved. Among other objectives, he wanted to produce nitrogen based agricultural fertilizers by extracting the nitrogen directly from the air! He could never achieve that with his devices, as we can today well understand, but he managed to achieve perhaps the highest controlled temperatures of the day, about 3800°C, in the solar furnace of his pyheliophoro, a truly remarkable achievement.

If not before, at least in Paris, at the end of the turn of century, he became quite likely familiar with the works of A. Mouchot [2], Louis de Royaumont [3], Charles Metelier [4]. Also, mainly from his corresponcence and from documents found among his belongings, it is fair to assume that he must have had some degree of familiarity with the works of John Ericson [1,8] W. Adams [1,8], Calver [1,8,5], Aubrey Eneas [1,6,7,8], among others.

He was critical of the devices produced by Mouchot-Piffre, and soon understood that he needed to modify them in order to obtain higher temperatures and also in order to break the mechanical coupling between the solar furnace ( placed in the "focal zone") from the structure supporting the mirrors. If possible he also wanted a stationary solar furnace, while only the optics would do the necessary tracking of the sun’s apparent motion in the sky.

In Fig1.(a) the device developed by Mouchot-Piffre is shown, a paraboloid like shaped structure with reflecting inner walls, and a furnace place along its optical axis.

(a) (b)

Fig.1.- (a) Solar device of Mouchot-Piffre (b) parabolic trough of Ericson

Truncated cone like shaped mirrors (Eneas Fig.1. (c)[6,7], Pasadena, California, 1901) and large flat ones (Calver, [5]Tucson, 1901) were among some of the solar optics of the day. John Ericson [1,8] proposed a parabolic shaped mirror in 1880 (Fig. 1(b)), but Himalaya’s ideas went in rather different directions.

References [5,6,7] are explicit instances of Portuguese magazines dedicating space, in those days, to those and other inventions and F. Himalaya likely read them. It was not possible to consult the referred magazines and therefore their level of technical detail is not known to the author. However these were publications for a general audience and little should be expected beyond some photos or drawings and a reference to the purpose of the inventions. .

To the interested reader the author recommends the first section of a modern book [8] containing an interesting introductory chapter on the history of solar energy. This book makes an explicit mention of Father Himalaya and his crown solar achievement — the Pyrheliophoro — at the St. Louis Fair of 1904.

10

Fig.1. (c) — solar experimental apparatus of Eneas

He soon understood that the very high concentration factor he needed required two axis type tracking. With materials processing in mind, he needed solutions that would not have, in his own words, "the furnace between the reflector and the sun”. He thus first thought of lenses to do the job, since these could send the concentrated light down and out, towards the target. However the required dielectric (glass!) lenses were not a practical idea in those days and his first remarkable attempt can be seen in Fig.2 and 3. It is a metallic Fresnel lens type, done with flat-strip — mirrors, ring shaped, the whole ingeniously tracking the sun in elevation and compensating for the earth’s rotation, by moving together on circular rails.

Fig2.- Figures from Patent [10]

Fig.3(a)- the device and Himalaya standing in front of it, in Paris

His experiments were carried out in the French Pyrenees, (Castel d’Ultrera) not far from Odeillo and Font-Romeu (of later day fame, for very similar solar reasons!)

The results he obtained were not as good as he expected, but it seems that he was able to achieve temperatures in excess of 1500°C (melting iron), a remarkable achievement, given the choice he had of materials for the mirrors, and a good measure of the mechanical precision with which he was able to produce his device. It should be noted that the solar furnace itself was object of careful developments, to be able to contain the materials he was melting/processing with it. His temperature measurements were crucially dependent on what he was able to melt.

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Fig.3(b) — the device at Castel d’Ultrera

In fact the furnace itself was the object of patents, perhaps the most important of which being Patent [9].

Fig.4 is taken from that patent, showing a radiative type furnace, where the side walls c, c’ were to be heated with the burning of fuel and the heat radiated into the triangular shaped cavity was to be concentrated (focussed) down onto the hot cavity F, by a paraboloid shaped upper wall d. This furnace was later very easily (and much better) adapted to the solar focussing optics to be described next, with solar radiation coming trough an aperture placed in d and the side walls c, c’ now serving as a second stage concentrator.

In the process of these developments he invented also a radiometer — to measure solar radiation intensity using his metallic lens concept.