Although pressure reducing valves (PRVs) have traditionally been employed to regulate pressure and reducer water leakage, researchers have been increasingly investigating the strategy of ...micro-hydropower generation using pumps as turbines (PATs) to enable both pressure reduction and energy production as an alternative strategy in water distribution networks (WDNs). However, due to the continuous variability of flow discharge during the day, selecting the optimal PAT remains a challenging issue. To address this, the authors have developed HYPER, a freely available software app that implements an innovative approach for selecting the most suitable PAT in systems that involve both hydraulic and/or electrical regulation. In enabling the identification of the PAT parameters that maximize energy production, HYPER thus provides a fast and effective PAT selection tool. The effectiveness of the proposed approach was further demonstrated with application to a real WDN. Four operational patterns varying in terms of available flow and head drop were considered, showing that the most efficient pumps consistently tended to be located in close proximity to the maximum produced energy. Furthermore, the results confirmed that hydraulic regulation and coupled hydraulic/electric regulation-based installation layouts represent the best solutions in terms of energy produced. The solely electrical regulation option, given its poor flexibility, returns in all cases lower energy production with the lower adaptability of commercial pumps.
► Integrating oscillating water column devices with floating breakwaters can reduce costs. ► The integrated system can widen the frequency range for energy extraction. ► The integration of OWC ...devices can improve the performance of a floating breakwater.
Integrating oscillating-water-column type converters (pneumatic chambers) with slack-moored floating breakwaters can be a viable option for cost-sharing between wave energy capturing devices and shore-protection structures, and thus enhance the cost-effectiveness of wave energy utilization. When designing such integrated systems, it is desirable to have a system that can capture wave energy over a wide range of wave frequency. In this study, a configuration of floating breakwater with asymmetric pneumatic chambers (a narrower chamber on the seaside and a wider chamber on the leeside) is proposed to increase the amplitude of the oscillating air-pressures inside both chambers over a wide range of wave frequency (thus to improve the performance in wave energy extraction). A series of experiments were carried out under regular wave conditions to study the effects of asymmetric pneumatic chambers on the hydrodynamic performance of the floating breakwater and on the oscillating air-pressures inside the two chambers. It was shown that (1) the breakwater with asymmetric chambers performed as good as that with symmetric chambers in terms of wave transmission and motion responses and (2) with asymmetric configuration, it is possible to increase the amplitude of the oscillating air-pressures inside both chambers. The new concept provides a promising way to extend the frequency range over which wave energy can be extracted.
In an effort to ensure energy independence and exploit mineral resources, the governments of Amazonian countries are embarking on a major dam building drive on the basin’s rivers, with 191 dams ...finished and a further 246 planned or under construction. This rush to harvest the basin’s vast renewable energy capacity has come without proper consideration of the likely negative environmental externalities on the world’s most speciose freshwater and terrestrial biotas. Here we highlight the economic drivers for hydropower development and review the literature to summarise the impacts of dam building on Amazonian biodiversity. We identify both direct and indirect impacts through the anticipated loss, fragmentation and degradation of riparian habitats. We then propose a series of measures to assess, curb and mitigate the impacts of destructive dams on Amazonian biodiversity.
This open access book presents (selected) new and innovative developments for sustainable and fish-friendly hydropower. It offers unique insights into the challenges, practices and policies of ...hydropower developments across 8 European countries, providing examples from on-site studies and European-wide analyses. The case studies throughout the book are practical “real-world” examples, which are intended to serve as inspiration for anyone who would like to know more about how solutions for more sustainable hydropower production can be designed and implemented. Hydropower is an important renewable energy source, which, however, can also impact aquatic ecosystems, fish populations and hydro-morphology. EU and national water, environmental and energy legislation strive for sustainable energy and water resource management as well as the protection of important habitats and species. These have an effect on the requirements and decision making processes for hydropower planning, commissioning and operation. With a high variety of measures existing and site-specific conditions as well as national and EU level legal requirements to consider, it can be difficult to determine, what issues to address and which measures to implement.
The aim of this study is to estimate the mean annual power absorption of a selection of eight Wave Energy Converters (WECs) with different working principles. Based on these estimates a set of power ...performance measures that can be related to costs are derived. These are the absorbed energy per characteristic mass kWh/kg, per characteristic surface area MWh/m
2, and per root mean square of Power Take Off (PTO) force kWh/N.
The methodology relies on numerical modelling. For each device, a numerical Wave-to-Wire (W2W) model is built based on the equations of motion. Physical effects are modelled according to the state-of-the-art within hydrodynamic modelling practise. Then, the W2W models are used to calculate the power matrices of each device and the mean annual power absorption at five different representative wave sites along the European Coast, at which the mean level of wave power resource ranges between 15 and 88 kW per metre of wave front. Uncertainties are discussed and estimated for each device.
Computed power matrices and results for the mean annual power absorption are assembled in a summary sheet per device. Comparisons of the selected devices show that, despite very different working principles and dimensions, power performance measures vary much less than the mean annual power absorption. With the chosen units, these measures are all shown to be of the order of 1.
► 8 Wave Energy Converters with different working principles are calculated. ► Using numerical modelling, their power matrices are estimated. ► Annual energy production and power measures iarecalculated at five different sites. ► Comparison shows that despite very different levels of energy production, power measures are of similar order of magnitudes.
A fully open-source available framework for the parametric cross-sectional analysis and design optimization of slender composite structures, such as helicopter or wind turbine blades, is presented. ...The framework—Structural Optimization and Aeroelastic Analysis (SONATA)—incorporates two structural solvers, the commercial tool VABS, and the novel open-source code ANBA4. SONATA also parameterizes the design inputs, postprocesses and visualizes the results, and generates the structural inputs to a variety of aeroelastic analysis tools. It is linked to the optimization library OpenMDAO. This work presents the methodology and explains the fundamental approaches of SONATA. Structural characteristics were successfully verified for both VABS and ANBA4 using box beam examples from literature, thereby verifying the parametric approach to generating the topology and mesh in a cross section as well as the solver integration. The framework was furthermore exercised by analyzing and evaluating a fully resolved highly flexible wind turbine blade. Computed structural characteristics correlated between VABS and ANBA4, including off-diagonal terms. Stresses, strains, and deformations were recovered from loads derived through coupling with aeroelastic analysis. The framework, therefore, proves effective in accurately analyzing and optimizing slender composite structures on a high-fidelity level that is close to a three-dimensional finite element model.
Due to rising energy demands and abundant untapped potential, hydropower projects are rapidly increasing in the Neotropics. This is especially true in the wet and rugged Andean Amazon, where regional ...governments are prioritizing new hydroelectric dams as the centerpiece of long-term energy plans. However, the current planning for hydropower lacks adequate regional and basin-scale assessment of potential ecological impacts. This lack of strategic planning is particularly problematic given the intimate link between the Andes and Amazonian flood plain, together one of the most species rich zones on Earth. We examined the potential ecological impacts, in terms of river connectivity and forest loss, of the planned proliferation of hydroelectric dams across all Andean tributaries of the Amazon River. Considering data on the full portfolios of existing and planned dams, along with data on roads and transmission line systems, we developed a new conceptual framework to estimate the relative impacts of all planned dams. There are plans for 151 new dams greater than 2 MW over the next 20 years, more than a 300% increase. These dams would include five of the six major Andean tributaries of the Amazon. Our ecological impact analysis classified 47% of the potential new dams as high impact and just 19% as low impact. Sixty percent of the dams would cause the first major break in connectivity between protected Andean headwaters and the lowland Amazon. More than 80% would drive deforestation due to new roads, transmission lines, or inundation. We conclude with a discussion of three major policy implications of these findings. 1) There is a critical need for further strategic regional and basin scale evaluation of dams. 2) There is an urgent need for a strategic plan to maintain Andes-Amazon connectivity. 3) Reconsideration of hydropower as a low-impact energy source in the Neotropics.
PDF
