Category Archives: EuroSun2008-9

Experience to consider

Many countries’ leaders stress the need for strengthening human resources for improving the quality of energy. They urge their governments to focus efforts on promoting renewable energy technologies and pledged international community with commitment to strengthen national energy sector with renewable energy technologies. On one hand, most of developed countries succeeded in their efforts and currently renewable energy contribution in those countries are significant and the industry in general is on the stage of exponential growth. The same is true for those developing nations whose governments have taken concrete steps towards harnessing renewable energy resources for socio-economic development of their country. On the other hand, many efforts in last years by a number of states and organizations have yet to achieve a renewable energy marketplace. Experts view this was a consequence of three fundamental things: (i) first, not achieving the critical messages and motivators needed to affect business and consumer behavioural change; (ii) second, despite widespread publicity and media coverage of the subject, most consumers are not aware of any compelling reason to choose renewable energy; (iii) third, not effectively leveraging the investment and incentives as most available research suggests that price is still the single most important factor in selecting a renewable energy comes with a premium price; (iv) fourth, the target audience is diverse and complex [5].

The demand for skilled and knowledgeable labour throughout the renewable energy industry and increasing interest from students has spurred several educational institutions across the U. S. and Europe to add undergraduate or graduate degrees, or certification programs in renewable energies to their curricula.

Obviously as a part of obstacles is that benefits of renewable energy have not clearly communicated with the public, customers and decision makers. Educational quality, measured by what people know, has powerful effects on individual earnings, on the distribution of income, and on economic growth [6]. The role of education and its quality becomes important and crucial not only in general terms but in this specific area as well.

In fact, what most people like about their utility is the total absence of having to think about it at all. For those who have an understanding of options, reliability is then a worry. Concern about a change to an unfamiliar source represents a significant barrier to switching that must be addressed and overcome.

Another key factor is that education supports market and industry development in renewable energy field. For an economy, education can increase the human capital in the labour force. It can also increase the innovative capacity of the economy, knowledge of new technologies, products, and processes promotes growth. Education facilitates the diffusion and transmission of knowledge needed to understand and process new information and to implement new technologies devised by others, again promoting growth [7].

Combination modes of solar cells

One individual silicon solar cells provides under nominal conditions, on average, in the order of 600 mV and 30 mA/cm2. Solar cells are then rarely used individually. Rather, cells with similar characteristics are connected and encapsulated to form modules which, in turn, are the basic building blocks of solar arrays. Starting from individual solar cell load curve, the curve of the combination of certain number of cells will preserve the basic series-parallel interconnection laws (Figure 1). Voltage for serially connected elements is the sum of partial voltage across the individual cells and the same current flows through every solar cell. If higher currents are demanded in a system, these can be obtained by parallel connection of the individual strings. In a parallel connected configuration, the

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voltage across each solar cell or solar module is equal, while the total current is the sum of all cell or module partial currents. At present, PV generators in grid connected systems work in the range of hundreds volts and amperes.

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Fig. 1 Interconnection modes of identical solar cells

The work ahead for the creation of Italy’s Archive on the History of Solar Energy

The results of the research done during the 2006-2007 period at the Central State Archive on the Patents and Trademarks Collections have secured new commitments. The Italian State Archives Department and GSES signed a cooperation agreement and established an ad hoc working group (Solar Archive Working Group) in 2008 to perform a nationwide survey of sources and create a multimedia database. The work already done in the Central State Archive’s Patents and Trademarks Collection, and by GSES in the private archives of Italian solar energy pioneers, has produced useful technical and scientific results that can provide a starting point for this survey, which might well focus first of all on sources regarding patents and trademarks contained in the State Archives and in private archives.

The work ahead for Italy’s Solar Archive was illustrated by Terenzoni from the State Archives Department at the seminar on April 4 [7]. She addressed the main aspects related to archival sources and tools for historical research on solar energy in Italy. Italy’s archives contain miles upon miles of shelves filled with all kinds of documents, information and data produced by government bureaus and agencies, public and private enterprises, and individuals. Very often their contents are accessible only by means of “traditional” systems. To consult documents regarding a particular subject, it is sometimes necessary to be familiar with, or reconstruct, the history of the institution or the biography of the individual that produced the documents, as well as the

circumstances that led to their production, drawing one to look into all the ramifications (real or suspected) of a given activity.

The archival sources are heterogeneous and the existing research tools are complex and not easy to handle, and will thus require some terminological-control tools, for instance a glossary and dictionaries of standard terms, which can enable users to search through databases by keywords and identify descriptors. Moreover, language and terminology evolve; therefore, in order to produce a truly useful search tool it will be necessary to clarify linguistic ambiguities and the relationships among terms that belong to the same family.

The Solar Archive Working Group has already started looking into this. The systemic aspects of solar energy is guiding the terminology work, both when we think of solar energy resources on earth as well as when we think of solar know-how and technologies that can convert those resources in energy forms useful to us (food, heat at low, medium and high temperatures, daylight, fuels, electricity, materials etc.).

Inputs to clarify linguistic ambiguities and relationships among terms will also come from the material contained in the archives, documentation, and bibliographies collected thus far.

Going for imperative

More and better education is a prerequisite for rapid development of renewable energy industry, growth of the businesses and markets. Education stimulates economic growth and improves people’s lives, and empowers individuals and governments make right decisions and support renewable energy development. On the other hand, nation’s commitment to education is both demand-lead and supply-lead [8].

For example, with surging interest from the residential construction sector and new requirements for utilities to generate portions of their energy from renewable sources, the renewable energy industry in the U. S. is flourishing, and job opportunities are increasing. As the industry grows, however, a workforce shortage is expected [9].

In Armenia, education about renewable energy has mostly been limited to learning tracks and seminars at industry tradeshows and conferences. Clean energy should start playing a significant role in people’s lives, and thus teaching of renewable energy should be emphasized in education and public awareness campaigns. Education in renewable energy fields should become a priority for the state. Some curriculum developers and teachers in both schools and academic institutions should incorporate renewable energy related activities in their curricula.

As mentioned earlier, one of barriers to mainstream adoption of renewable energy systems is the lack of awareness among consumers. Many consumers have heard at least some reference to renewable energy at various times in their lives, but they do not know how to incorporate it into their daily lives and they lack the necessary knowledge to purchase and utilize renewable energy technologies.

"There are a lot of great engineering and architectural firms that want to do things with energy but aren’t quite sure what to do with them. We need to educate more people," says Michael J. Newtown, director of the State University of New York-Canton’s (SUNY-Canton) Alternative and

Renewable Energy Applications degree program. "As engineering and architectural firms come together, there really is a need to educate the populace on how renewable energy gets used, and where it gets used, and what’s the best application" [9].

At this stage, the limitation of reaching the set targets for renewable energy development is indeed related to education and training. Per words of Dr. Ad van Wijk, Chairman and Founder of Econcern (the Netherlands) “we developed many scenarios for the integration of wind power and energy efficiency. The reality has always exceeded the most optimistic scenarios. The only thing that is limiting goals is a shortage of skilled people. We have train and educate in a range of skills and technologies that are not traditionally taught in colleges and universities. It is a real challenge”

[10] .

The importance of general public education is proved by lack of understanding by a consumer of the technology. While, numerous surveys have confirmed widespread public interest in renewable energy, hurdles identified by the California Energy Commission (CEC) included [11]:

• lack of awareness about choice and how to switch to new, and fear of switching and losing reliability

• price premium for renewable energy with return on the investment unclear

• lack of knowledge regarding the environmental impacts of electric generation and the benefits of renewables

• lack of knowledge regarding the equipment and its technology application and availability

• a perception that the installation processing is difficult and complicated

• difficulty in finding a qualified installer and lack of trusted references from (friends, neighbours, etc.) that have installed their own solar or wind systems.

Mismatch effect

Подпись: Fig. 2 Parametric representation of PV cell generator load curve

In general terms, given a temperature and irradiance values, the load curve of a conventional solar cell can be represented by a classical parametric model (Figure 2) in which it can be distinguished 3 operation zones in regard to the load nature. As shown, cells being operated in reverse bias mode can suffer structural damage. Mismatch appears when the electrical parameters of one or several solar cells are significantly altered from those of the remaining devices and being altered the resulting curves shown in Figure 1. The alteration of a cell can consist, as advanced, of slight parameters modification due to the tolerance in manufacturing process or a change in its operating conditions in regard to the rest because the blocking of radiation impinging the cell surface.

For simplicity, we will restrict the description of the influence of mismatched parts to a circuit constituted by 2 single cells, A and B (Figures 3 and 4), being the cause of the unbalanced behavior the shading of cell B.

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For a series interconnection, Figure 3 (right) shows how open circuit conditions for A+B generator are no highly affected by mismatching of cell B. However, as the current through the two cells must be the same, the overall current from the combination cannot exceed that of the poor cell. Therefore, the current from the combination cannot exceed the short-circuit current of the poor cell. At low voltages where this condition is likely to occur, the extra current-generating capability of the good cells is not dissipated in each individual cell (as would normally occur at short circuit), but instead is dissipated in the poor cell. An easy method of calculating the combined short circuit current of series connected mismatched cells is to consider that the current at the point of intersection represents the short circuit current of the series combination (VA+VB=0).

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For parallel connected cells, at low voltages, there is no real problem with mismatch as the currents just add and the total current is always higher than the individual cell currents. However, the resulting open circuit conditions are highly affected because the addition of mismatched cell B reduces the open circuit of A+B generator to a lower value in regard to the original one. A simple method to calculate the resulting open circuit voltage in this situation is to consider according individual cells curves that the above will occur when iA + iB = 0,as shown in Figure 4 (right).

Fig. 4 Mismatching in parallel connected cells