• Energy Research

Abstract A study of the molecular structure of regio-regular bulk poly-3-octyl-thiophene (P3OT) and poly-3-hexyl-thiophene (P3HT) and the phase transitions during heating and cooling scans in a temperature range of –158–773 °C has been performed by means of calorimetry of bulk samples and grazing incidence X-ray diffraction from synchrotron radiation. Additional calorimetric measurements were performed on samples in toluene solution. From the calorimetric temperature diagrams at different scan rates, we obtain the melting and crystallization temperatures, and we identify a low temperature calorimetric glass transition. This transition is expected because of the coexistence of amorphous and crystalline phases, which is further supported by scanning force microscopy images where lamellar structures have been observed. Thin films of both polymers have also been studied by grazing incidence X-ray diffraction, and the evolution of the (1 0 0) crystalline peak monitored as a function of sample temperature, showing different behavior in both polymers, d -spacing increases in P3HT and decreases in P3OT for increasing temperatures. The information presented in this article will be useful to design fabrication techniques for organic-based electronic devices, which could include high and low temperature cycles combined with structural quenching procedures.

Access to electricity has a positive impact on the socio-economic activity in rural livelihoods. Stand-alone photovoltaic (SAPV) systems are the most popular PV application for rural electrification in areas nonconnected to the grid, but it is still relatively expensive. Batteries are considered as a weak component of the system, comprising an important part of the total cost and are usually replaced multiple times during PV system lifetime. A priority load control algorithm has been developed in order to gain a better energy management over system loads and the battery storage, and therefore guarantee the energy supply for critical loads and extends the battery service lifetime. This will increase the reliability of the system and the end-user satisfaction. This article describes a stand-alone PV system model used for the development of a priority load control algorithm and explains and implements the algorithm. The results of several test scenario simulations are shown and discussed.

One way of increasing access to electricity for impoverished unconnected areas without adding significant amounts of CO2 to the atmosphere is by promoting renewable energy technologies. However, decision-makers rarely, if ever, take into account the level of in-built energy requirements and consequential CO2 emissions found in renewable energy, particularly photovoltaic cells and related equipment, which have been widely disseminated in developing countries. The deployment of solar panels worldwide has mostly relied on silicon crystalline cell modules, despite the fact that less polluting material—in particular, thin film and organic cells—offers comparatively distinct technical, environmental and cost advantages characteristics. A major scientific challenge has thus been the design of a single decision-making approach to assess local and global climate change-related impacts as well as the socio-economic effects of low-carbon technology. The article focuses on the functions of the multi-criteria-based tool SURE-DSS and environmental impact analysis focused on greenhouse gases (GHG) emissions balance to inform the selection of technologies in terms of their impact on livelihoods and CO2eq. emissions. An application in a remote rural community in Cuba is discussed. The results of this study show that while PV silicon (c-Si), thin film (CdTe) and organic solar cells may each equally meet the demands of the community and enhance people’s livelihoods, their effect on the global environment varies.

Procedures for testing organic solar cell devices and modules with respect to stability and operational lifetime are described. The descriptions represent a consensus of the discussion and conclusions reached during the first 3 years of the international summit on OPV stability (ISOS). The procedures include directions for shelf life testing, outdoor testing, laboratory weathering testing and thermal cycling testing, as well as guidelines for reporting data. These procedures are not meant to be qualification tests, but rather generally agreed test conditions and practices to allow ready comparison between laboratories and to help improving the reliability of reported values. Failure mechanisms and detailed degradation mechanisms are not covered in this report. © 2011 Elsevier B.V. All rights reserved.

Abstract In Spain, solar electricity (photovoltaic and thermoelectric) has reached a stable annual capacity factor above 20% since 2009; while wind achieved 23% since more than 10 years ago. This is the demonstration of an ongoing transition towards a more sustainable energy mix, further corroborated by the reduction of the capacity factor of gas-fired technology, which has seen a decline to values lower than 10% after an initial promising rise; this is a very low value for a fossil-fuel technology. Additionally, hydro installed capacity, which has been stable for the past 20 years, have demonstrated that can be used as a back-up power source in combination with solar and wind electricity, and it is capable of producing energy peaks that may increase from a stable base of 2000 GWh/month up to 6000 GWh/month and therefore meet demand at some particular times when solar and wind are generating less electricity without the need of installing new additional capacity at national level.

The diverse socio-economic and environmental impacts related to the setup of a new photovoltaic installation must be weighed carefully in order to reach the best possible solution. Among the different photovoltaic systems, there are several classification criteria, depending on the technology, application, and size of the modules that define them. The size (installed nominal capacity) stands out as an impartial and critical measure in the decision-making process. In this article, we use a multi-criteria decision-making method to analyze the responses of five experts to a detailed questionnaire in which several different criteria are correlated with various photovoltaic installation sizes. The limitation associated with a low number of experts is addressed with a robustness and sensitivity analysis. With this study, we seek first to apply and demonstrate the feasibility of a methodology that combines technical information with multi-criteria decision-making methods. Second, we obtain a clear result that increases the benefits of a forthcoming photovoltaic installation of modules in distributed generation, adding up to one GW total peak power in standard conditions. We observe a consistent result in which smaller photovoltaic modules provide the ideal solution, as this format maximizes the socio-economic benefits of any installation. If a decision has to be taken about the type of photovoltaic plant to be installed, the conclusion is clear: given a certain size, small, easily scalable installations are the best solution for stakeholders, the inhabitants, and the environment.

Organic and hybrid perovskite based solar cells have a huge potential to significantly contribute to a clean electricity supply of the future. However, so far they exhibit complex and hierarchical degradation paths and their understanding can only be acquired through the application of complementary chemical and physical characterization techniques. This limited device stability is the main hurdle for a successful and large scale market introduction of these emerging solar cell technologies. Our StableNextSol Action has created a highly interdisciplinary network of laboratories, as well as corresponding industry, overall more than 120 partners, with complementary analytical techniques for the study and understanding of the degradation mechanisms occurring in state-of-the-art devices. Our Action integrates and generates fundamental knowledge and expertise to foster disruptive innovations targeted to mitigate device failure and to propose and develop new concepts for more stable solar cells. Value is added to the entire value chain of photovoltaic research at European and international level, as well as variety decision makers in the public sector by supporting specialisation policy and standards still lacking in this research field. The outcome of the Action will contribute to resolve the global challenges facing the industry and this COST Action initiative has brought together all these expertises and resources to promote the cooperation between different sectors, academia, public authorities and industry.