We report on the effect of a new laser annealing treatment for thin film CdTe solar cells using a 808 nm diode laser. As-deposited, laser annealed and MgCl2 treated/laser annealed CdTe thin films have been analysed. One part of the work has been focused on understanding the efficacy of the activation treatment by laser annealing. The results show partial chlorine diffusion and associated partial re-crystallisation of the absorber. The second part of this work has been focused on the effect of the treatment on the chemical composition of the CdTe surface. It has been found that the process also contributes to the formation of a Te-rich layer on the surface of the CdTe absorber, which may provide a useful process to produce a back contact. This paper reveals the effect of the laser treatment on the micro-structural properties of the CdTe absorber material. The microstructure has been analysed using STEM/EDX, HRTEM and XRD. Further work is required to optimise the process but it has the potential to provide much greater control than current activation methods and also to provide a Te back contact suitable for CdTe solar cells.
CdTe-based thin film solar cells currently represent one of the fastest growing PV technologies, with a superior combination of efficiency, energy payback time and lifecycle environmental impact. However, the current post-deposition annealing treatment is still an energy intensive step of the manufacturing process. A novel method is presented for annealing of CdTe using a high-power diode laser (35 W, 808 nm) for thermal post-processing, combined with holographic optical elements (HOE’s) for laser beam heat flow control. The advantage of a laser for annealing lies in its ability to selectively heat only the surface of the CdTe solar cell; improving energy efficiency, process speed and energy resilience. Heat transfer simulations were used to predict the effects of different laser irradiance profiles on the annealing process thermal cycle influence the experimental design and predict optimal laser irradiance profiles. Variations in power and process speed on as-deposited and MgCl2-treated close-space sublimated (CSS) CdTe samples have been performed. The results were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Optical properties were analysed with a spectrophotometer and ellipsometric spectroscopy (SE). The laser annealing treatment was found to be effective in promoting Chlorine diffusion and improving the optical and morphological properties of CdTe thin film devices.
The combustion of fossil fuels for energy generation has contributed considerably to the effects of climate change. In order to reduce fossil fuel consumption, designers are increasingly seeking to reduce the energy consumption of products over their life cycle. To achieve a significant reduction in energy consumption, it is essential that energy considerations are incorporated within the design phase of a product, since the majority a product's environmental impact is determined during this phase. This work proposes a new ‘Design for Energy Minimization’ (DfEM) approach, which is intended to provide increased transparency with respect to the energy consumed during manufacture in order to help inform design decisions. An energy simulation model based on this approach is then presented to aid designers during the design phase. The application of this novel design tool is demonstrated in two cases: That of a simple product (designed by a single Original Equipment Manufacturer (OEM) through a centralized approach); and a complex product (designed by a number of designers within a supply chain using a distributed approach). The subsequent benefits to energy minimization are then discussed and conclusions drawn.
Resource efficiency is one of the greatest challenges for sustainable manufacturing. Material flow in manufacturing systems directly influences resource efficiency, financial cost and environmental impact. A framework for material flow assessment in manufacturing systems (MFAM) was applied to a complex multi-product manufacturing case study. This supported the identification of options to alter material flow through changes to the product assembly design, to improve overall resource efficiency through eliminating resource intensive changeovers. Alternative assembly designs were examined using a combination of intelligent computation techniques: k-means clustering, genetic algorithm and ant colony algorithm. This provided recommendations balancing improvement potential with extent of process modification impact.
As resources become scarcer, efficiency improvements alone will not bridge the widening gap between supply and demand, resulting in the need for additional non-financial mechanisms to ensure the fairer allocation of resources. This paper asserts that, in the future, companies will need to demonstrate their products’ positive contribution to society as well as minimising their negative environmental/social impacts. A review and analysis of existing tools and assessment methodologies identifies current capabilities and highlights the need for 'Societal Value’ assessment that considers both quantitative and qualitative factors .This paper concludes by proposing a systematic framework for addressing the 'Societal Value’ of products as part of an integrated sustainability assessment and allows the evaluation and comparison beyond products’ shared functionality.
Experimental cutting tests on C45 carbon steel turning were performed for sensor fusion based monitoring of chip form through cutting force components and radial displacement measurement. A Principal Component Analysis algorithm was implemented to extract characteristic features from acquired sensor signals. A pattern recognition decision making support system was performed by inputting the extracted features into feed-forward back-propagation neural networks aimed at single chip form classification and favourable/unfavourable chip type identification. Different neural network training algorithms were adopted and a comparison was proposed.
SMART authors: Alessandro Simeone
The majority of the environmental impact of a product is decided during the design phase, and as such there has been a rapid growth in generation of methodologies and tools that aim to improve design and include sustainability considerations in product development. Although these methodologies and tolls and have introduced measurable benefits, in most cases they have been incremental in nature as opposed to producing radical `Factor X` improvements. The highlights the need for a careful analysis of existing sustainable design methods to identify their shortcomings and to enable a greater understanding of ecodesign and its extension into sustainable design improvement. This paper provides a brief overview of the evolution of ecodesign and its extension into sustainable design. It assesses the key influencing factors of current practice and identifies a number of future research challenges, promoting the next stage in its development in which sustainability will become a ubiquitous part of the design process.
Fuel cells offer attractive possibilities for efficiency generation across many applications. Within the context of Extended Producer Responsibility legislation and increasing concerns regarding material scarcity and waste, it is important that preparation for end-of-life management of the technology is made, prior to mass commercialization. Using a case study approach, life cycle environmental impact assessment, cost analysis and evaluation of legislative requirements are shown to support strategic development of end-of-life strategies for fuel cells. The findings highlight how the early identification of priorities for recycling of high impact, high value materials may help to avoid future detrimental impacts at end-of-life.
SMART authors: Shahin Rahimifard
The growing interest in bio-polymers as a packaging material, particularly from companies looking to reduce their environmental footprint, has resulted in wider adoption. Traditionally the selection and specicification of packaging materials was based on aesthetic, technical and financial factors, for which established metrics exist.
However with bio-polymers, where the primary rationale for their use is environmental, alternative metrics are required. Furthermoe, there is a significant stratgeic element to the decision process that requires a broader range of horizontal and vertical inputs, both within the business and the wider supply chain. It is therefore essential that a holistic approach is taken to the bio-polymer based packaging design process to ensure that the final packaging meets the original strategic intent and overall requirements of the business. Current ecopackaging design tools are generally limited to professional users, such as designers or packing engineers, and generally provide tactical rather than strategic support. This disconnect, between the need for inclusivity and greater strategic support in holistic design, and the exclusivity and largely tactical support of current eco-design support tools, indicates a clear need for a new decision support tool for sustainable pack design using bio-polymers.
This paper proposes a framework for an eco-design decision support tool for bio-polymer based packaging that has been developed using a predominantly qualitative research approach based on reviews, interviews and industrial packaging design experience and is an extension of previously published work. This research investigatesfurther how existing eco-design methods, such as the 'Balanced score card', can be applied within the tool and how the shortcomings associated with incorporating social and environmental aspects can be partly resolved, through a simplified set of metrics tailored specifically for bio-polymer packaging decisions. The results of this research is a framework for the development of a three tier eco-design tool for bio-polymer packaging that provides decision support at the three critical stages of the design process: stratgic fit, Feasbility assessment and concept/pack development.
The industrial sector consumes a significant amount of the world’s energy supply; the rationalisation of energy consumption would provide the most effective method of reducing greenhouse gas emissions attributed to manufacturing and use of products. Energy consumed across the various stages of a product’s lifecycle varies significantly depending on the product design and its application. In non-energy using products such as furniture, food, and clothing, the material preparation and production phases represent a significant proportion of energy consumption over the product lifecycle. This paper proposes a new design methodology targeted at these products to minimise energy consumption during ‘production’ phase.
SMART authors: Shahin Rahimifard
Bioplastics derived from renewable polymers such as sugars, starches and cellulose, have attracted significant interest from companies looking to reduce their environmental footprint. New production capacity and improved materials have resulted in their increasing adoption for mainstream consumer products packaging. However questions remain regarding their overall environmental benefits and how the maximum environmental gain can be achieved. These uncertainties highlight the need for a decision support tool to aid the packaging design process. This paper examines the issues surrounding bio-derived polymer use and discusses the development of an eco-design tool to assist in their rapid and efficient adoption.
Concerns for the enviroment are currently dominated by global warming and climate change, caused by the consumption of fossil fuels. A significant factor is the consumption of energy by manufactured products during their use phase. The production of these products is also a focus of attention because of the inefficient way that society in general and industry in particular manages resources. A responsible approach to design and manufacture of products should embrace efficient resource use by reducing the consumption of non-renewable resources throughout a product's life-cycle. This provides tremendous opportunities for practicing a whole raft og concepts and practices that embrace, for example: design for environment, environmentally benign/conscious manufacture, waste minimization, dematerialization and product service system, energy conservation and management, green/sustainable supply chain management, product end-of-life management and reverse logistics.
The cocnerns for the environment are intrinsic to the concept of sustainable development but this concept also embraces the economic and social context within which concern for the environment is exercised. Whilst the broad concept of sustainable development is commonly accepted, it is the emphasis on resource use and conservation that most strongly permeate legislation. Governments have recognized theur responsibility to the environment and exercised their authority through legislation that directly affects manufacturing businesses. Such legislation requires that businesses reduce their consumption of resources, especially energy, minimize their waste and accept their responsibility for their products when they reach the end of the their working life. It is within this context that the proposal for a special issue was generated.
SMART authors: Shahin Rahimifard