Sri Lanka milestone for Shell Solar

Shell Solar has reached a milestone in its efforts to provide rural communities with access to energy, in bringing PV electricity to 20 000 homes and small businesses in Sri Lanka. The company says strong demand for PV systems is likely to continue in Sri Lanka, where only 59% of households are connected to the electricity grid and thousands of rural residents rely on batteries and kerosene.Visit www.re-focus.net for the latest renewable energy industry news     

Solar photovoltaics: Trends and prospects

Key areas in the development of photovoltaic methods of solar energy conversion, which open up wide prospects for semiconductor solar energy conversion, are discussed. The article focuses mainly on photovoltaic cells based on III-V heterostructures, primarily on cascade solar cells, which provide the highest efficiency of solar energy conversion and are produced by high-tech methods such as MBE or MOCVD. It is shown that the use of intermediate sunlight concentration makes the area of solar cells smaller and, hence, lowers their cost proportionally to the sunlight concentration ratio.     

Sri Lanka and Canada: A comparison of telematic policy developments

The Canadian experience, though not wholly relevant to small developing countries like Sri Lanka, may have long term relevance. Canada took the strategic path of developing its telecommunications (including broadcasting) infrastructure as a response to the convergence of technologies and problems of cultural diversity and demographic dispersion. It did not simultaneously provide the impetus for the development of computer products and services which could be demanded by the expanded Canadian telemarket, leading to market penetration by overseas producers. Sri Lanka, despite its low capability in the area of telematics and informatics, does not perceive external penetration to be a threat, because of the relatively underdeveloped telecommunications systems. However, the new technologies have transborder dimensions which must be carefully examined in terms of opportunities and threats presented to a country's industrialization, investment promotion, telecommunications, energy, education and information policies.     

Getting small: a short history of the personal computer

Traces the development of the personal computer (PC). The article first considers the technological underpinnings; how integrated circuits and microprocessors replaced vacuum tubes etc. The computer had been developed mainly by and for large organisations, but it was the amateurs that caused the emergence of the PC, beginning with the Altair 8800, which the user assembled himself. The interface consisted of switches and flashing lights. The hardware and interfaces then developed and new manufacturers entered the market. Finally, the emergence of graphical user interfaces and user-friendly applications software made the PC of interest to users without the skill or inclination to be programmers     

Employee perception towards electronic monitoring at work place and its impact on job satisfaction of software professionals in Sri Lanka

Electronic monitoring is a rapidly growing phenomenon in Sri Lankan software industry. It allows employers to observe what employees do on the job and review employee communications, including e-mail and internet activity that employees consider private. Often, employers use electronic monitoring to ensure organizational confidentiality, limiting employer liability for employee misconduct. From the perspective of employees, electronic monitoring by employers involves several privacy and confidentiality concerns. Most of the time, employee performance and productivity aspects captured via electronic monitoring are effectively used by the Human Resources Departments, for decision making associated with the employees.Majority of the software development organizations in Sri Lanka today use some means of electronic technology to monitor their employee activities. Most of the time, employee perception towards electronic monitoring at work, contradicts with the need for law enforcement within the organization intended by the top management. Employers justify electronic monitoring at work place in terms of protecting the company’s confidential information, preventing the misuse of the organizational resources while uplifting the quality of work and productivity. On the other hand, the mutual trust that should be there between the employer and the employee is in question. Therefore, this study empirically investigated the relationship that might exist between the software professionals’ perception towards electronic monitoring at work place and its impact on their job satisfaction.Based on disproportionate stratified random sampling, data were collected from 380 software professionals in Sri Lanka, by administrating a structured questionnaire in which items were of 5 point Lickert scale. The data analysis included the univariate, bivariate and multivariate analyses.In this study, Perceived Relevance to Work and Personal Judgment of Effectiveness which were two variables used to measure perception of electronic monitoring were positively correlated with Job Satisfaction. This means that the software professionals, who view electronic monitoring as something which is relevant to their work as well as which uplifts the quality of their work, are satisfied in their jobs. Perceived Invasion of Privacy was negatively correlated to Job Satisfaction, which sheds some light in organizational electronic monitoring policy making. Also, Perceived Task Satisfaction was negatively correlated to Job Satisfaction. This means that the software professionals, who thought that working in an electronically monitored environment makes their tasks more complex, are rather dissatisfied in the job. Also, it appeared that the impact of electronic monitoring at work place on the job satisfaction of software professionals becomes less significant along with higher professional experience.The findings of this research can be incorporated in IT security policy making in the software development organizations in Sri Lanka and in similar economics, with a special emphasis on the job satisfaction of their employees, which is the most valuable asset of the organization.     

Comparison of short and long wavelength absorption electron donor materials in C60-based planar heterojunction organic photovoltaics

Buckminsterfullerene, C₆₀-based planar heterojunction (PHJ) organic photovoltaics (OPVs) have been created using a short wavelength absorption (λ_max = 490 nm) electron-donating bis(naphthylphenylaminophenyl)fumaronitrile (NPAFN). NPAFN exhibits a hole mobility greater than 0.07 cm² V⁻¹ s⁻¹ as determined by its field-effect transistor. It can be attributed to such hole mobility that enables a thin layer (<10 nm) NPAFN in PHJ OPV, ITO/NPAFN/C₆₀/bathocuproine/Al. Because of the low lying HOMO energy level (5.75 eV) of NPAFN and relatively high ionization potential ITO (∼5.58 eV), such OPVs exhibit a very high open circuit voltage of ∼1.0 V, relatively high fill factor of 0.60, and a relatively high shunt resistance of 1100 Ω cm⁻², which all compensate for a relatively low short circuit current of 3.15 mA cm⁻² due to the short absorption wavelength and inferred short exciton diffusion length of NPAFN. Altogether, NPAFN OPVs display a power conversion efficiency (η_PC) of 2.22%, which is better than other long wavelength absorption materials in similar PHJ OPVs, such as pentacene (λ_max 670 nm, HOMO 5.12 eV, η_PC 1.50%) and copper phthalocyanine (λ_max 624, 695 nm, HOMO 5.17 eV, η_PC 1.43%).     

Progress in crystalline multijunction and thin-film photovoltaics

Photovoltaics are important in terrestrial applications such as remote power and renewable energy but are the primary source of electrical power for space systems. Here, priorities are high conversion efficiency and resistance to radiation-induced degradation and emphasis is on III-V multijunction solar cells and lower efficiency but flexible, lightweight thin-film solar cells. Triple junction III-V solar cells have reached conversion efficiencies of 30% at air mass zero (AM0). New lattice mismatch techniques and nitride materials hold promise for further efficiency increases. Thin-film solar cells generally have less than 15% efficiency but greater radiation resistance, lower cost, and lower mass.     

Crystalline silicon photovoltaics: the hurdle for thin films

The dominant photovoltaic (PV) technology today is crystalline silicon, used in 85% of the terrestrial modules shipped in 1996. Thin-film PV technologies promise to allow significant reductions in the cost per watt of electricity generated by PV modules. However, thin films must meet or exceed the standards for performance, reliability, and cost set by crystalline silicon in order to successfully penetrate the market. This paper reports the results of a detailed economic analysis done for a 25 MW year⁻¹ multi-crystalline silicon production facility, including crystal growth, water slicing, solar cell fabrication and module assembly. The module manufacturing cost is projected to be $1·78 W⁻¹. The sensitivity of module cost to polysilicon cost and cell efficiency were determined. This analysis provides a near-term (1998–2000) cost/performance benchmark against which thin-film technologies can be compared. © 1997 John Wiley & Sons, Ltd.     

Progress in crystalline multijunction and thin-film photovoltaics

Photovoltaics are important in terrestrial applications such as remote power and renewable energy but are the primary source of electrical power for space systems. For space applications, priorities are high conversion efficiency and resistance to radiation-induced degradation. The emphasis is on III-V multijunction solar cells and comparatively lower efficiency but flexible, lightweight thin-film solar cells. Triple-junction III-V solar cells have reached conversion efficiencies of 30% at air mass zero (AM0). New lattice mismatch techniques and nitride materials hold promise for further efficiency increases. Thin-film solar cells generally have less than 15% efficiency but greater radiation resistance, lower cost, and lower mass.     

Probing film solidification dynamics in polymer photovoltaics

Semiconducting conjugated polymers have drawn a great deal of attention over the past decade due to their solution processability and potential use in roll to roll fabrication of organic solar cells. Here, we report the effect of solvent vapor pressure on poly(3-hexylthiophene):[6,6]-phenyl C₆₁-butyric acid methyl ester (P3HT:PCBM) blade coated inverted solar cells using ZnO as the electron transporting layer and MoO₃ as the hole transporting layer. The resultant morphology and device performance are investigated for devices processed from solvents with varied vapor pressure and a mixed solvent. We report that the use of a mixed solvent system is advantageous for controlling the initial vapor pressure of the processing solution, thereby controlling the phase separated morphology between P3HT and PCBM which impacts ultimate solar cell performance.     

Electronic structure of fullerene derivatives in organic photovoltaics

The electronic structures of the fullerene derivatives [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), [6,6]-diphenyl C₆₂ bis (butyric acid methyl ester) (bisPCBM), C₇₀, [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₀BM), [6,6]-phenyl-C₆₁-butyric acid butyl ester (PCBB), [6,6]-phenyl-C₆₁-butyric acid octyl ester (PCBO), [6,6]-thienyl-C₆₁-butyric acid methyl ester (TCBM), and indene-C₆₀ bisadduct (ICBA), which are frequently used as n-type materials in organic photovoltaics, were studied by ultraviolet photoelectron spectroscopy and inverse photoemission spectroscopy. We also performed molecular orbital calculation based on density functional theory to understand the experimental results. The electronic structures near the energy gap of the compounds were found to be governed predominately by the fullerene backbone. The side chains also affected the electronic structures of the compounds. The ionization energy and electron affinity were strongly affected by the number of carbons and functional groups in the side chain.     

Research opportunities in crystalline III–V photovoltaics

Although III-V solar cells have been developed to a high level of performance, opportunities for fundamental advances still exist. For example, new structures could lead to substantial gains in conversion efficiency, multi-junction solar cells could achieve efficiencies well above 50%, and new materials could be developed for applications such as thermophotovoltaics. In this paper, the authors describe research opportunities that could provide the scientific base for substantial enhancements in the performance of crystalline III-V photovoltaic cells.     

Event report: Sunrayce 93: Collegiate competition introduces American public to photovoltaics

Thirty-four university teams raced their solar-powered cars from Texas to Minnesota during the week of the summer solstice, 20-26 June 1993. the event, called Sunrayce 93, was a dazzling display of creativity and ingenuity by some of the brightest students in North America. Organized by the United States Department of Energy as an educational programme for college-level science and engineering students, the race also serves to introduce the public to photovoltaics, electric vehicles and energy efficiency.     

Gold nanorod enhanced organic photovoltaics: The importance of morphology effects

Organic photovoltaic devices with a 30% improvement in power conversion efficiency are achieved when gold nanorods (Au NR) are incorporated into the active bulk heterojunction (BHJ) layer. Detailed analysis of the system is provided through microscopy, device characterization, and spectroscopy, demonstrating that the enhancement effects are predominantly caused by induced morphology changes in the BHJ film rather than plasmonic effects. Wide angle X-ray diffraction provides evidence that the nanorods loaded into the BHJ film have an effect on polymer crystal orientation, leading to a systematic performance increase in the devices as a result of both internal and external efficiency improvements.     

Terabit memory systems: A design history

The TBM memory system development effort is described, starting with initial concepts in 1965, through feasibility experiments in 1966, engineering model in 1968, manufacturing prototype in 1971, first delivered system in 1972, and system developments that have occurred in the last three years. The evolution of the initial concepts is illustrated by examining the features incorporated in these successive models. Projections describing possible future systems are also made.     

Opportunities in silicon photovoltaics and defect control in photovoltaic materials

Silicon is the dominant semiconductor material in use for terrestrial photovoltaic cells. The critical issues in cell design, materials specification and cell processing are reviewed. Specific attention is given to light trapping, minority carrier lifetime control and novel microstructures for enhancing photon absorption. Relevant topics in generic defect control are discussed with particular emphasis on compound semiconductor materials.     

高精度太阳能跟踪控制器

针对目前采用的传统太阳能跟踪控制器传感器形式单一、抗干扰性差、跟踪精度不高等问题,设计了一种基于可编程逻辑控制器(Programmable Logic Controller,PLC)的太阳能跟踪控制器系统。该系统将固定轨迹粗略跟踪方式与光电传感器精确跟踪方式有效地结合起来,并重点将光电传感器加以改进,从而有效地提高了太阳能利用率。由伺服电机作为执行机构控制太阳能板对太阳位置的跟踪,可以实现对太阳高度角和方位角的双自由度跟踪,使太阳能跟踪装置始终正对着太阳光线位置。通过对比实验表明,该跟踪控制器可以达到较高的跟踪精度。     

Catalysts for the diffusion of photovoltaics — A review of selected programmes

The diffusion of photovoltaics still rests strongly on the availability of suitable support programmes. This suggests a closer look at their function as a catalyst for the spread of the technology. The paper defines this function, gives hints for the programme design, and identifies six different variables of a catalyst. These are then related to concrete programmes in Germany and Switzerland, the two countries showing the highest diffusion of photovoltaics in Europe. The analysis embraces the ‘1000 Roofs Programme’, ‘rate‐based incentives’, ‘utility programmes’ and ‘large scale photovoltaic programmes’. In spanning the last decade the study provides a historic perspective unfolding from the past to the present. A variety of programmes are compared so as to determine their effect on the actual installation of photovoltaics. The paper elucidates some of the inner structure of programmes and portrays their changing landscape and approaches in space and time. Thus, it may serve as a decision aid for the design of future programmes. Copyright © 2001 John Wiley & Sons, Ltd.     

Third generation photovoltaics: Ultra‐high conversion efficiency at low cost

Since the early days of terrestrial photovoltaics, a common perception has been that ‘first generation’ silicon wafer‐based solar cells eventually would be replaced by a ‘second generation’ of lower cost thin‐film technology, probably also involving a different semiconductor. Historically, cadmium sulphide, amorphous silicon, copper indium diselenide, cadmium telluride and now thin‐film polycrystalline silicon have been regarded as key thin‐film candidates. Any mature solar cell technology seems likely to evolve to the stage where costs are dominated by those of the constituent materials, be they silicon wafers or glass sheet. It is argued, therefore, that photovoltaics is likely to evolve, in its most mature form, to a ‘third generation’ of high‐efficiency thin‐film technology. By high efficiency, what is meant is energy conversion values double or triple the 15–20% range presently targeted, closer to the thermodynamic limit of 93%. Tandem cells are the best known of such high‐efficiency approaches, where efficiency can be increased merely by adding more cells of different bandgap to a cell stack, at the expense of increased complexity and spectral sensitivity. However, a range of other more ‘paralleled’ approaches offer similar efficiency to an infinite stack of tandem cells. These options are reviewed together with possible approaches for practical implementation, likely to become more feasible with the evolution of materials technology over the next two decades. Copyright © 2001 John Wiley & Sons, Ltd.