• Energy Research
• 13. Climate action close
• 11. Sustainability close
• 4. Education close
• CH close
• IN close
• English close

Oligotrophic catchments with short spatey streams, upland lakes and peaty soils characterise northwest European Atlantic coastal regions. These catchments are important biodiversity refuges, particularly for sensitive diadromous fish populations but are subject to changes in land use and land management practices associated with afforestation, agriculture and rural development. Quantification of the degree of catchment degradation resulting from such anthropogenic impacts is often limited by a lack of long-term baseline data in what are generally relatively isolated, poorly studied catchments. This research uses a combination of palaeolimnological (radiometrically-dated variations in sedimentary geochemical elements, pollen, diatoms and remains of cladocera), census, and instrumental data, along with hindcast estimates to quantify environmental changes and their aquatic impacts since the late 19th century. The most likely drivers of any change are also identified. Results confirm an aquatic biotic response (phyto- and zooplankton) to soil erosion and nutrient enrichment associated with the onset of commercial conifer afforestation, effects that were subsequently enhanced as a result of increased overgrazing in the catchment and, possibly, climate warming. The implications for the health of aquatic resources in the catchment are discussed Environmental Protection Agency in Ireland (ILLUMINATE 2005-W-MS-40, P.McGinnity was supported by the Beaufort Marine Research Award in Fish Population Genetics funded by the Irish Government under the Sea Change Programme.

The SmartBay NIAP fund was made available in 2012 through Dublin City University over a two year period to enable researchers to access the SmartBay Ireland National Test and Demonstration Facility in Galway Bay. Research proposals were invited for funding under a number of activity types that are in line with the objectives of the SmartBay PRTLI Cycle 5 programme. This fund provided small awards (typically €2-25K) to research teams through a national competitive process, which was open to all higher education institutions on the island of Ireland. There were both open and biannual calls. The SmartBay NIAP fund was established to enable researchers in academia and industry to access the SmartBay Ireland national test and demonstration infrastructure. Proposals to access the infrastructure were brief and required information on the researcher(s), a description of the proposed research and its potential impact to the research team arising from the access to SmartBay Ireland. Marine Institute

Cholera epidemics have a recorded history in eastern Congo dating to 1971. A study was conducted to find out the linkage between climate variability/change and cholera outbreak and to assess the related economic cost in the management of cholera in Congo.This study integrates historical data (20 years) on temperature and rainfall with the burden of disease from cholera in South-Kivu province, eastern Congo.Analyses of precipitation and temperatures characteristics in South-Kivu provinces showed that cholera epidemics are closely associated with climatic factors variability. Peaks in Cholera new cases were in synchrony with peaks in rainfalls. Cholera infection cases declined significantly (P<0.05) with the rise in the average temperature. The monthly number of new Cholera cases oscillated between 5 and 450. For every rise of the average temperature by 0.35 °C to 0.75 °C degree Celsius, and for every change in the rainfall variability by 10-19%, it is likely cholera infection risks will increase by 17 to 25%. The medical cost of treatment of Cholera case infection was found to be of US$50 to 250 per capita. The total costs of Cholera attributable to climate change were found to fall in the range of 4 to 8% of the per capita in annual income in Bukavu town.It is likely that high rainfall favor multiplication of the bacteria and contamination of water sources by the bacteria (Vibrio cholerae). The consumption of polluted water, promiscuity, population density and lack of hygiene are determinants favoring spread and infection of the bacteria among human beings living in over-crowded environments.

Power generation from photovoltaic systems is highly variable due to its dependence on meteorological conditions. An efficient use of this fluctuating energy source requires reliable forecast information for management and operation strategies. Due to the strong increase of solar power generation the prediction of solar yields becomes more and more important. As a consequence, in the last years various research organisations and companies have developed different methods to forecast irradiance as a basis for respective power forecasts. For the end-users of these forecasts it is important that standardized methodology is used when presenting results on the accuracy of a prediction model in order to get a clear idea on the advantages of a specific approach. In this paper we introduce a benchmarking procedure to asses the accuracy of irradiance forecasts and compare different approaches of forecasting. The evaluation shows a strong dependence of the forecast accuracy on the climatic conditions. For Central European stations the relative rmse ranges from 40 % to 60 %, for Spanish stations relative rmse values are in the range of 20 % to 35 %. 24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 4199-4208

In this paper, we have studied the solar radiation data available at two meteorological stations located in the south of Tunisia. Measurements of global solar radiation on horizontal surface are compared to predictions made by different methods. The first method is based on Angström-Prescott formula which correlates relative global solar radiation H/H0 to corresponding relative duration of bright sunshine SS/SS0. The second method, a model due to Mechlouch et al., uses cloud cover N, the hours of the day t and the quantum of the year q. The third method, an empirical relation due to Sivkov, uses the monthly sunshine duration nm and the noon altitude of the sun h. The models are compared and tested on the basis of statistical error tests (MBE, RMSE, MPE and R2) and the results are presented.

Photovoltaic (PV) energy generation has become one of the key pillars of the shift to a renewable energy future. Current devices, under favorable conditions, can already undercut the price per kWh electricity of other technologies on the market. Further reduction in the cost of installed PV systems and increase in solar module conversion efficiency will improve the affordability even more and will substantially aid in wider market penetration and enhance the volume of PV installations. Currently the PV market is dominated by silicon wafer based solar cells, but alternative technologies offer some distinctive advantages, making them interesting for numerous applications. Thin film technologies, as for example based on Cu(In,Ga)Se2 (CIGS) compound semiconductors with high optical absorption coefficient, are becoming important due to lower material and energy requirements for processing of high conversion efficiency solar cells. Inherent advantages are large area depositions with low production costs, and the possibilities for construction of lightweight, flexible devices with roll-to-roll manufacturing processes. The highest efficiency of single-junction CIGS solar cells is approaching the thermodynamic limit, making the use of alternative concepts such as concentration or multijunction (tandem-) devices the next logical step for further increase in efficiency beyond the Shockley-Queisser limit (S-Q limit). Especially the multi-junction technology, in which the thermodynamic losses are reduced by stacking of solar cells with different band gaps, decreasing thermalization of charge carriers excited with energies above the band gap, is a promising approach for enhanced utilization of the solar spectrum, yielding improved efficiency. Such devices, based on epitaxial layers of III-V compounds have already demonstrated remarkably high efficiencies beyond the S-Q limit. However, these devices grown on rather expensive single crystal wafers and with small size are prohibitively pricey for low cost terrestrial solar electricity generation. On the other hand, multi-junction solar cell technology based on polycrystalline thin films is an attractive option for large area, low cost production, provided adequately high efficiencies are achieved. In this context, two-junction tandem devices, developed by stacking a semitransparent large band gap solar cell of 1.6-1.7 eV on top of a low band gap (~1.0 eV) bottom cell, is a viable option. Earlier attempts in this direction were not so successful, but with the rise of perovskite thin film solar cells as a compatible high efficiency wide band gap (>1.6 eV) top cell and CIGS with a tunable band gap as bottom cell, the prospect for all thin film tandem devices with efficiencies beyond the single-junction limitations has opened. Such all thin film devices hold the potential for the low cost production necessary for large scale terrestrial application. This thesis focuses on the development of high efficiency narrow bandgap (1.0 eV) CIGS solar cells for application in all thin film tandem devices. While for CIGS with band gap of around 1.15 eV efficiencies of over 23 % have been demonstrated, cells with a narrow band gap close to 1.0 eV only reach 15.0 %. The efficiency of these narrow band gap cells are limited by charge carrier recombination, leading to low open circuit voltage (VOC) and reduced fill factor. For solar cell efficiency enhancement it is necessary to investigate the underlying reasons contributing to the deficits in PV parameters and develop processes to overcome the limiting factors. An option to reduce recombination within the solar cell is the implementation of a band gap grading as discussed in Chapter 3. The increase of the band gap at the location of highest recombination leads to a reduction in diode current, and therefore an increase in VOC. To keep the band gap of 1.0 eV a substantial part of the absorber needs to be Ga free. As the primary source of recombination is not obvious, different gradings (realized by a change in the Ga to In ratio) are implemented and compared. A single grading with increased band gap (higher Ga/In ratio) towards the front of the absorber shows no significant improvement on photovoltaic parameters. Any gain in VOC is offset by losses in current due to reduced charge collection, mainly visible for long wavelength photons and probably a result of the upwards bending in the conduction band. A single backgrading (higher Ga/In ratio towards the back electric contact) on the other hand leads to substantial improvements in performance ( from 12.0 % to 16.1 %). It is shown that the collection of photo-generated charge carriers improves and recombination is reduced. Measurements of the effective lifetime by time resolved photo-luminescence are carried out, showing an increase from approximately 20 ns to 100 ns when comparing ungraded with back-graded absorbers. By selectively changing the recombination speed at the back contact, strong differences in the behavior of cells with and without a band gap widening towards the back are observed. The results support that considerable recombination at the back contact is present in pure CIS solar cells, and that the single Ga back-grading approach is effective at suppressing this loss channel. In Chapter 4 the alkali treatment of CIS based solar cells is investigated. Alkali elements are known to strongly influence doping and passivation in CIGS solar cells. It is shown that the amount of sodium necessary to reach sufficient doping levels for high performance CIS solar cells is not achieved using the processes developed for CIGS. This may be based on insufficient Na diffusion into the grain, as those cells generally show larger grains than their CIGS counter parts, and since alkali migration energies in CIS are reported to be higher compared to those in CGS. If CIS cells are grown on soda lime glass without any diffusion barrier and additionally receive post deposition treatment (PDT) with NaF they still show low apparent doping concentration and poor PV performance ( = 10.9 %). However, additional annealing at ~ 370 C substrate temperature after PDT is shown to solve this problem, leading to an increase in apparent doping levels close to 1016 cm−3 and cell efficiency of 15.0 %. The application of an additional heavy alkali PDT, specifically RbF, is shown to lead to further improvements in cell efficiency. Changes at the front interface due to the PDT allow a decrease of buffer layer thickness, leading to a higher photo current (approximately + 1.0 mAcm−2). In addition, reduced recombination and the resulting increase in lifetime leads to additional gains in VOC, resulting in considerably improved device performance, up to an efficiency of 18.0 %. Further efficiency improvement is achieved by investigating the effect of close to stoichiometric compositions of Cu to group III elements as described in Chapter 5. The sub-stoichiometric Cu composition of state-of-the-art CIGS absorbers leads to a high concentration of detrimental defects. The defect density within the absorbers is reduced by approaching a stoichiometric Cu composition. Improvements in the defect density are identified by the decrease of Urbach energy from 20 to 16 mV and an increase in doping is observed for cells with almost stoichiometric Cu content. Cells with high, and especially stoichiometric Cu composition tend to be limited by recombination at the front interface, leading to a decrease of VOC of about 20 mV. Using the modified absorber surface after heavy alkali PDT, these losses are suppressed. Based on these improvements, a narrow band gap cell with record breaking 19.2 % efficiency and an open circuit voltage of 609 mV is achieved. Throughout the whole thesis the suitability of these cells for tandem devices with semitransparent perovskite top cells is investigated by 4-terminal tandem measurements. The improvements achieved in this work led to CIS based solar cells that not only show outstanding single cell performance, but also enable highly efficient tandem devices up to 25.0 %. They outperform state-of-the-art single junction CIGS and perovskite cells while showing prospects for further efficiency improvement. Due to the low band gap of the CIS absorber the current density from the bottom cell is high enough to produce current matched tandem devices with high efficient perovskite top cells (19.2 to 18.6 mAcm−2 in 4-terminal configuration), and also monolithic two-terminal configurations are feasible in the future.

Modern conceptions of progress, based on the dominant Cartesian reductionist paradigm, are associated with a linear drive towards ever greater ascendancy, order, organisation, homogeneity, hegemony, performance, efficiency, and control. Similarly modern conceptions of progress are associated with positivist approaches to overcoming and extinguishing disorder, inchoateness, uncertainty, redundancy and risk. In this framework, diversity is conceived as a threat to system organisation, efficiency and control. Many contemporary conceptions of sustainability and sustainable development, framed within this paradigm, envisage sustainability as aligning with such ideas of progress. By this narrative, sustainable systems are achievable through ever greater efficiency, through for example, technological prowess, improved organisational structure/control, taming of “big data” and through risk reduction/extinction. Similarly, corporate sustainability would be advanced through growth, mergers and acquisitions, rationalisation, pruning of smaller operations/sites within firms, layoffs, increased corporate control, accountability and managerialism. “Bigger is better” is the apposite maxim. From a complex systems perspective however, a very different picture is evident. In the ecological domain, sustainable ecosystems have been quantitatively shown to be those which maintain an appropriate (context, time and space dependent) dynamic balance between opposing tendencies of ascendancy and efficiency on one hand and diversity and redundancy on the other (Ulanowicz, 2009; Goerner et al., 2009). Ecological biodiversity is an absolute requirement for ecosystem endurance since it facilitates system resilience in the event of significant perturbation (whether sudden shock or longer term stress). For example, a species which can feed on a selection of available prey species is more resilient against partial ecosystem destruction/prey extinction than one which relies on a single species for food. While the latter scenario represents a situation of greater efficiency, it is also more rigid and less resilient. Moreover, while the tendencies of complex systems towards ascendancy (organisation, efficiency) and disorder (redundancy, diversity) are antagonistic at local levels, they are in fact mutually dependent at higher levels (Ulanowicz et al, 2009): “A requisite for the increase in effective orderly performance (ascendency) is the existence of flexibility (reserve) within the system. Conversely, systems that are highly constrained and at peak performance (in the second law sense of the word) dissipate external gradients at ever higher gross rates”. This model has been mirrored across techno-economic and social domains wherein similar sustainability models have been proposed (e.g. Stirling, 2011). This framework has manifested itself in research outputs across virtually every discipline, where in different guises sustainable and persistent systems have been shown to require a balance between tendencies of control, structure and organisation and those of diversity and disorder.

The rapid growth of clean technologies to address climate change has emphasized the increasing complexity of materials, some of which face criticality and potential supply disruptions. Inte- grated assessment models (IAMs) used for designing illustrative mitigation pathways (IMPs) lack comprehensive information on material annual demand projection. This study focuses on the demand for the rare earth element neodymium (Nd) until 2050 in wind power and transporta- tion sectors. The assessment is based on the three most ambitious IMPs, namely “Low Energy Demand” (LD), “Sustainability Pathways” (SP), and “Rapid Technology Change” (Ren), from the Intergovernmental Panel on Climate Change’s (IPCC) Assessment Report 6 (AR6). The results show that Nd demand steadily increases in all scenarios, but the magnitude and growth rates vary. The LD scenario exhibits the lowest material needs in passenger transport due to shared road transport and rail preferences, consequence of a focus on final energy use changes, while the SP scenario presents the highest growth in material demand. The Ren scenario, char- acterized by fast electrification and energy intensity improvements, represents a middle-ground scenario for material demand with good opportunities for recycling. This study underscores the significance of considering material demand in scenario design and highlights the importance of better assessing crucial external factors used for material stock determination in the future. The findings contribute to improving scenario design precision and the understanding of material use implications, providing valuable insights for climate policies and resource management strategies.

Today's electrical grid is undergoing deep changes, resulting from the large integration of distributed Renewable Energy Sources (RES) in an effort to decarbonize the generation of electrical energy. In addition to the emergence of this volatile electricity production, the worldwide demand for electricity increases due to a growing population and the intensified electrification of buildings. Smart-buildings represent promising assets for supporting the electrical grid in balancing demand with a supply based on non-dispatchable RES. A smart-building denotes a building equipped with sensor/actuator hardware connected to a federating Building Data Management System (BDMS) which enables high-level applications and services. Tapping into the flexibility inherent to its various entities (load, storage, and generation), a smart-building can provide Demand Response (DR) functionality through the optimization of its energy profile in response to varying electricity prices or commands from the grid.This PhD thesis provides a set of tools, algorithms, and frameworks, revolving around the notion of smart-buildings that foster an enhanced Building-to-Grid (BtG) integration. The tools developed here aim to fill the gap encountered in the literature created by the recent rollout of BDMSs and the ubiquitous Internet of Things (IoT). Furthermore, the mismatch between current DR and the future RES-based smart-grid opens the way to the development of innovative algorithms and frameworks to manage the flexibility offered by smart-buildings for grid-side agents. Built upon BDMSs, two open-source tools have been developed. Firstly, an integrated high-speed emulation and simulation software, dubbed Virtualization Engine (vEngine), allows the simulation of non-existing components of a building directly on-site. The multi-threaded, light architecture of vEngine permits efficient simulations, in a modular environment conceived for developers. Secondly, we describe Open Energy Management System (OpenEMS), a platform that seamlessly connects to any existing BDMS and provides its users with an environment to create their own energy management algorithms, with a focus on Model Predictive Control (MPC). Simulations using a realistic Swiss residential building model demonstrate the effectiveness and modularity of both tools. Additionally, we propose a multi-state load profile identification algorithm tailored to Non-Intrusive Load Monitoring (NILM). Applied to energy disaggregation, it shows promising results for enhanced energy feedbacks to the occupants. To attain daily energy balance within the smart-grid, we propose several algorithms and energy management frameworks, using smart-buildings. An incremental MPC formulation is derived to better balance monthly costs associated to energy and peak demand of large commercial buildings. Simulations data show substantial benefits, for both the building's owner and the grid. Furthermore, we present a decentralized framework for autonomously managing the energy in a community of smart-buildings, with RES. Based on blockchain technology and smart-contracts, the framework optimizes an objective common to the whole community without the need for a central agent. Finally, we suggest a unified BtG model that could benefit grid-side aggregators in both microgrids and electricity markets.