Annick Anctil

Material and energy intensity of fullerene production.

Fullerenes are increasingly being used in medical, environmental, and electronic applications due to their unique structural and electronic properties. However, the energy and environmental impacts associated with their commercial-scale production have not yet been fully investigated. In this work, the life cycle embodied energy of C(60) and C(70) fullerenes has been quantified from cradle-to-gate, including the relative contributions from synthesis, separation, purification, and functionalization processes, representing a more comprehensive scope than used in previous fullerene life cycle studies. Comparison of two prevalent production methods (plasma and pyrolysis) has shown that pyrolysis of 1,4-tetrahydronaphthalene emerges as the method with the lowest embodied energy (12.7 GJ/kg of C(60)). In comparison, plasma methods require a large amount of electricity, resulting in a factor of 7-10× higher embodied energy in the fullerene product. In many practical applications, fullerenes are required at a purity >98% by weight, which necessitates multiple purification steps and increases embodied energy by at least a factor of 5, depending on the desired purity. For applications such as organic solar cells, the purified fullerenes need to be chemically modified to [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM), thus increasing the embodied energy to 64.7 GJ/kg C(60)-PCBM for the specified pyrolysis, purification, and functionalization conditions. Such synthesis and processing effects are even more significant for the embodied energy of larger fullerenes, such as C(70), which are produced in smaller quantities and are more difficult to purify. Overall, the inventory analysis shows that the embodied energy of all fullerenes are an order of magnitude higher than most bulk chemicals, and, therefore, traditional cutoff rules by weight during life cycle assessment of fullerene-based products should be avoided.

Life-cycle assessment of organic solar cell technologies

Organic photovoltaics are often proposed as a solution to achieve low cost and low environmental impact in a solar cell. In this work, life cycle assessment (LCA) was conducted for various donor and acceptor materials, taking into account required purity of reactants and solvents, low yields for reactions, repeated purification steps, and toxic chemicals and solvents used for production of electronic grade semi-conductor materials. The full life cycle of complete single junction organic solar cells was done, based on current state-of-the art efficiencies reported for various donor/acceptor combinations. At this point, it is shown that the increase in device efficiency results in an increase in energy payback, mainly because higher concentrations of [C70]PCBM are being used which have a higher embodied energy compared to lower efficiency [C60]PCBM - based solar cells.

Ultra-Lightweight Hybrid Thin-Film Solar Cells: A Survey of Enabling Technologies for Space Power Applications

The development of hybrid inorganic/organic thin-film solar cells on flexible, lightweight, space-qualified, durable substrates provides an attractive solution for fabricating solar arrays with high mass specific power (W/kg). Next generation thin-film technologies may well involve a revolutionary change in materials to organic-based devices. The high-volume, low-cost fabrication potential of organic cells will allow for square miles of solar cell production at one-tenth the cost of conventional inorganic materials. Plastic solar cells take a minimum of storage space and can be inflated or unrolled for deployment. We will explore a cross-section of in-house and sponsored research efforts that aim to provide new hybrid technologies that include both inorganic and polymer materials as active and substrate materials. Research at University of Texas at Arlington focuses on the fabrication and use of poly(isothianaphthene-3,6-diyl) in solar cells. We describe efforts at Norfolk State University to design, synthesize and characterize block copolymers. A collaborative team between EIC Laboratories, Inc. and the University of Florida is investigating multijunction polymer solar cells to more effectively utilize solar radiation. The National Aeronautics and Space Administration (NASA)/Ohio Aerospace Institute (OAI) group has undertaken a thermal analysis of potential metallized substrates as well as production of nanoparticles of CuInS2 and CuInSe2 in good yield at moderate temperatures via decomposition of single-source precursors. Finally, preliminary work at the Rochester Institute of Technology (R.I.T.) to assess the impact on performance of solar cells of temperature and carbon nanotubes is reported. Technologies that must be developed to enable ultra-lightweight solar arrays include: monolithic interconnects, lightweight array structures, and new ultra-light support and deployment mechanisms. For NASA applications, any solar cell or array technology must not only meet weight and AMO efficiency goals, but also must be durable enough to survive launch conditions and space environments.

Anions for Near-Infrared Selective Organic Salt Photovoltaics

Organic molecular salts are an emerging and highly tunable class of materials for organic and transparent photovoltaics. In this work, we demonstrate novel phenyl borate and carborane-based anions paired with a near-infrared (NIR)-selective heptamethine cation. We further explore the effects of anion structures and functional groups on both device performance and physical properties. Changing the functional groups on the anion significantly alters the open circuit voltage and yields a clear dependence on electron withdrawing groups. Anion exchange is also shown to selectively alter the solubility and film surface energy of the resulting molecular salt, enabling the potential fabrication of solution-deposited cascade or multi-junction devices from orthogonal solvents. This study further expands the catalog and properties of organic salts for inexpensive, and stable NIR-selective molecular salt photovoltaics.

Implications for current regulatory waste toxicity characterisation methods from analysing metal and metalloid leaching from photovoltaic modules

The appropriateness of regulatory methods to characterise the toxicity of photovoltaic (PV) modules was investigated to quantify potential environmental impacts for modules disposed of in landfills. Because solar energy is perceived as a green technology, it is important to ensure that end-of-life issues will not be detrimental to solar energys success. United States Environmental Protection Agency Method 1311, California waste extraction test, and modified versions of both were performed on a multi-crystalline silicon module and cells and a copper indium gallium diselenide (CIGS) module. Variations in metal leachate concentrations were found with changes in testing parameters. Lead concentrations from the multi-crystalline module ranged from 16.2 to 50.2 mg/L. Cadmium concentrations from the CIGS module ranged from 0.1 to 3.52 mg/L. This raises doubt that regulatory methods can adequately characterise PV modules. The results are useful for developing end-of-life procedures, which is a positive step towards avoiding an e-waste problem and continuing trends of increasing installation and cost reduction in the PV market.

An educational simulation tool for integrated coastal tourism development in developing countries

In spite of the importance of coastal tourism for the economies of many developing countries, tourism infrastructure has often been developed without full consideration of long-term impacts on the environment. The simulation model presented in this paper aims to address critical gaps in awareness and capacity for integrated decision-making and planning in tourism infrastructure development in a developing country context. We build a simple closed-loop model of tourism infrastructure investment, which integrates typical economic, social and ecological dimensions of the problem. The model is calibrated so that within 20 years, investment projects in tourist capacity done without concomitant investment in solid waste and wastewater treatment result in a collapse of fish stocks and a sharp drop in tourist attendance. The model includes several policy options that allow users to intervene at various points in the loop, allowing stakeholders to explore how various combinations of policies perform in financial, environmental and social terms over the long period. The model can, therefore, be used as an educational tool for training and capacity-building.

Life cycle assessment of silicon solar panels manufacturing in the United States

This work discusses the life-cycle impact associated with manufacturing silicon monocrystalline (c-Si) and multi-crystalline (mc-Si) photovoltaic (PV) panels in the United States compared to China. It has two significant contributions. First, the impact of importing panels manufactured in China to install in the US is compared with domestic US manufacturing using a database modeling approach. Second, the life cycle analysis is improved by using specific electricity and material inventory based on disassembled Suniva panels for which the actual material inventory has been compiled. The results from the U.S. lifecycle assessment using standard lifecycle inventory shows that modules entirely made in China or assembled in U.S. from Chinese solar cells have a similar carbon footprint. However, the complete manufacturing of panels in the U.S. reduces the carbon footprint by 13 to 22% because of the difference in the energy mix and the reduction in transportation. By incorporating the data from dismantling and digesting modules, the use of metals in small quantities is accounted for, unlike previous studies, and allows for a more complete environmental comparison. Evaluating the metal use in PV modules shows the metal usage in the U.S. manufactured c-Si module is four times higher than other scenarios.

Integrating algaculture into small wastewater treatment plants

Algaculture has the potential to be a sustainable option for nutrient removal at wastewater treatment plants. The purpose of this study was to compare the environmental impacts of three likely algaculture integration strategies to a conventional nutrient removal strategy. Process modeling was used to determine life cycle inventory data and a comparative life cycle assessment was used to determine environmental impacts. Treatment scenarios included a base case treatment plant without nutrient removal, a plant with conventional nutrient removal, and three other cases with algal unit processes placed at the head of the plant, in a side stream, and at the end of the plant, respectively. Impact categories included eutrophication, global warming, ecotoxicity, and primary energy demand. Integrating algaculture prior to activated sludge proved to be most beneficial of the scenarios considered for all impact categories; however, this scenario would also require primary sedimentation and impacts of that unit process should be considered for implementation of such a system.

Life Cycle Assessment of Organic Photovoltaics

The unlimited abundance of solar resources ensures that photovoltaic technologies have the potential to supply a significant amount of the energy required to fulfill currentand futureenergy demands while reducing greenhousegases emissions. So far, the high cost of photovoltaics compared to other energy sources has limited their use. However, emerging technologies, such as organic photovoltaics (OPV), which take advantage of man-made materials and solution processing, hold the promise for inexpensive devices. While solar cells could be an alternative to energy produced from fossil fuels, it is necessary to ensure that, in doing so, new environmental issues are not created. For this reason, life cycle assessments (LCAs) can be undertaken on emerging organic technologies to evaluate a priori the environmental impact of large-scale production and identify pathways toward sustainable energy production. In this chapter, the methodology of life-cycle assessment is presented, emphasizing photovoltaics usages, and is applied to emerging organic photovoltaics.

Dye-sensitized bulk heterojunction polymer solar cells

At present, there is a real limitation one can achieve with state-of-the-art fullerene-polymer solar cell materials in a fully optimized device based upon the poor mismatch to the solar spectrum. Empirical modeling has been performed using device parameters from current-voltage and spectral response measurements. The limiting Jsc has been simulated from the spectral response profile of PCBM[70]-MEH-PPV and PCBM[60]-P3HT devices. The maximum efficiency for these systems is calculated to be between 6 and 9%, under 1 sun illumination. Empirical simulations show that molecular dyes absorbing between 800-900 nm in a properly structured device can theoretically increase the device photocurrent sufficient to reach a power conversion efficiency of 16% in a bulk heterojunction polymer solar cell under 1 sun AM1.5 illumination. We have investigated the use of soluble organic dyes with measured bandgaps in the nearinfrared (NIR) to extend the spectral conversion in polymeric solar cells. An appropriate energy level structure (to promote exciton dissociation and charge transport to the fullerene derivatives and polymer) has been measured using cyclic voltammetry for certain indolylidene dyes. The incorporation of these dyes into a PCBM-P3HT device structure has shown an enhancement in the spectral response at 1.5 eV.