• Energy Research
• Restricted close

The scaling of thin film photovoltaics to a commercially viable size relies on the series connection of multiple small cells into modules. These interconnections are typically formed by three patterning steps, each of which have an impact on the series resistance and consequently on the total module performance. Here, we implement the transmission line method for the complete analysis of the P2 patterning step of the photoactive layer in organic photovoltaic modules. Devices are investigated with a sample design that allows for a comparative study of the P2 connection on the solar cell performance. We compare subtractive mechanical scribing to a newly developed additive pre-patterning method for the P2 step. Aerosol Jet printed pre-patterning lines of low surface energy and conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified with a fluorosurfactant repel the subsequently spray coated photoactive layer. Furthermore, the influence of MoO3 in the P2 pattern is elucidated, displaying a substantial increase in series resistance and decrease in device performance.

Abstract This paper reports part of a methodology for a model-based exploration of land use motivated by the lack of sustainability of small farming systems in southern Uruguay. Explorative land use studies aim to gain insight into future possibilities for agricultural development. They support strategic thinking during the design of new farming systems. The crop rotation plays a central role in a farming system and represents a logical starting point in the design process. The combination and sequence of crop species determine characteristics of farming systems such as crop yields, soil erosion, occurrence of soil-borne pests, diseases and weeds, and dynamics of nitrogen and labour. Here, we present a software tool called rotat , designed for generating crop rotations based on agronomic criteria in a transparent manner. The program combines crops from a predefined list to generate all possible rotations. The full factorial number of possible combinations of crops is limited by a number of filters controlled by the user. These filters are designed to eliminate crop successions which are agronomically unfeasible and for farm-specific reasons not practical or desirable. The filters represent expert knowledge in a quantitative and explicit way. The use of this computer program as a stand-alone tool in the process of designing crop rotations is illustrated with a published case study from an ecological pilot farm in Flevoland (The Netherlands). Using this software we were able to design 840 rotations based on the same crops and designing criteria that were used for the example farm. Many of these rotations might be interesting alternatives to the one actually implemented. Coupled with a sound procedure to evaluate the performance of such a large number of rotations ‘a priori’, rotat can reduce the risk of ignoring promising options and the arbitrariness present in previous studies dealing with design of rotations. The usefulness of rotat for designing production activities in explorative land use studies based on linear programming is discussed.

AbstractReplacing existing wind turbines with new and higher capacity turbines (‘repowering’) is to become a major challenge for planners within the next decade. While the benefits of repowering are evident, it cannot be assumed that the process will proceed automatically and without problems. The acceptance of future developments will be significantly affected by whether expectations of benefits from previous projects have been met, and whether perceived advantages of existing wind farms have outweighed their disadvantages. Therefore, it is important to explore how existing wind farms and their impacts on local development and well-being are assessed. This paper presents the results of a survey with local governments and inhabitants of municipalities in the Czech Republic where wind turbines have been implemented and are in operation. The findings prove that perceived positive effects dominate over negative impacts and that a majority of local authorities and inhabitants are willing to support further de...

Abstract With the rapidly increasing capacity of renewable energy production, the volatile nature of, e.g., wind and solar power necessitates solutions for storing excess energy. A finite-element model for simulating a geomembrane energy storage system is developed, in order to aid the development of the system and provide first insights into the performance of the system. Conceptually, energy is stored by pumping water from a nearby surface reservoir into a subsurface reservoir confined by a geomembrane, which lifts the overlying mass of soil, thereby increasing the potential energy due to gravity. An axisymmetric finite-element model is developed employing fluid cavity elements and fluid exchange links to simulate inflow and outflow of the reservoir, which resembles energy storage and energy re-harvest, respectively. A sophisticated constitutive model for a granular soil is employed using a hypoplastic model with intergranular strain extension, which includes essential characteristics as stress and density dependency, critical-state behavior as well as stress reversals. Analysis of repeated storage cycles provides realistic but undesirable deformation patterns, encountered by increasing irreversible displacements with advancing cycles. The reliable results of the model directly provides estimates of energy efficiency and can serve as a tool for further development and optimization of the energy storage system.

Abstract Rapidly changing hydrological conditions under climate change, upstream developments, and local water infrastructures require transformative changes in water management strategies for the agriculture sector in the Vietnamese Mekong Delta (VMD). For more than three decades, the agricultural policies in Vietnam have emphasized the intensification of rice production. In recent years, however, the Vietnamese government has started to pay more attention to longer-term sustainability considerations. Recent regional plans and high-level policies, including the Mekong Delta Plan and the Resolution 120 emphasize the development of high-value, sustainable and climate-resilient agriculture and food production. This shift has its challenges. One of them relates to changes in the government-mandated flood-control strategy. The increased awareness of the agricultural and environmental benefits of seasonal floods including soil fertility maintenance and pest management has resulted in new government regulations that require farmers to adopt a so-called 3–3–2 cropping cycle which means that every three years, farmers protected by high dikes should allow their rice fields to get flooded during the third rice season. Some of the farmers, however, have been reluctant to shift their farming cycle away from the triple-rice cropping system because of livelihood security-related concerns. Our study examines rice farmers’ livelihood sustainability in the upper delta by applying a sustainable livelihood framework to systematically identify prospects and challenges for more sustainable flood-based livelihoods. We interviewed 160 rice farmers and conducted two focus group discussions in two communes in An Giang province. Our results show that appreciation of the benefits of the 3–3–2 cycle has increased while the results of the livelihood capital index calculations show relatively good status of livelihood sustainability of farming households, indicated by the overall 5–capital scores of over 0.4. The study also identifies other constraints to sustainable farm-based livelihoods including unstable rice markets and shortage of labor. A key finding, however, is that unless more supportive policies and enhanced viability of flood-based crops are developed, farmers will not be sufficiently motivated to change their farming practices.

This paper deals with an investigation on the combustion process and pollutant formation of a small diesel engine fuelled with blended and pure biodiesel. The engine is a three-cylinder, 1028 cc, equipped with a common rail injection system. Endoscope based optical setup was used to observe in the cylinder without significant interference to the combustion process. Combustion images were post-processed by two-colour pyrometry method to evaluate the flame temperature and the in-cylinder soot concentration. Optical data were correlated to the nitrogen oxides and the particulate matter emissions measured at exhaust. Experiments were carried out at different operating conditions. It was found out that without EGR (exhaust gas recirculation), blended and pure RME (rapeseed methyl ester) were characterized by higher flame temperature and also by higher NOx emissions. In presence of EGR, lower flame temperature was detected for biodiesel; in this case higher NOx emissions were measured with biodiesel but the difference with NOx emissions from diesel fuel were reduced. Moreover, blended and pure biodiesel combustion was characterized by lower in-cylinder soot formation and also lower PM (particulate matters) at exhaust

This article reviews evidence from biogeography, palynology, geology, historical linguistics, and archaeology and presents a new synthesis of the paleoclimatic context in which the early Bantu expansion took place. Paleoenvironmental data indicate that a climate crisis affected the Central African forest block during the Holocene, first on its periphery around 4000 BP and later at its core around 2500 BP. We argue here that both phases had an impact on the Bantu expansion but in different ways. The climate-induced extension of savannas in the Sanaga-Mbam confluence area around 4000–3500 BP facilitated the settlement of early Bantu-speech communities in the region of Yaounde but did not lead to a large-scale geographic expansion of Bantu-speaking village communities in Central Africa. An extensive and rapid expansion of Bantu-speech communities, along with the dispersal of cereal cultivation and metallurgy, occurred only when the core of the Central African forest block was affected around 2500 BP. We clai...

AbstractThe synthesis and determination of the structure of a Förster resonance energy transfer probe intended for the detection of specific nucleic acid sequences are described here. The probe is based on the hybridization of oligonucleotide modified quantum dots with a fluorescently labeled nucleic acid sample resulting in changes of the fluorescence emission due to the energy transfer effect. The stoichiometry distribution of oligonucleotides conjugated to quantum dots was determined by capillary electrophoresis separation. The results indicate that one to four molecules of oligonucleotide are conjugated to the surface of a single nanoparticle. This conclusion is confirmed by the course of the dependence of Förster resonance energy transfer efficiency on the concentration of fluorescently labeled complementary single‐stranded nucleic acid, showing saturation. While the energy transfer efficiency of the probe hybridized with complementary nucleic acid strands was 30%, negligible efficiency was observed with a noncomplementary strand.