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Electrochemical capacitors, called supercapacitors (SCs) or ultracapacitors, are devices conveniently used for embedded electrical energy management owing to their huge capacitance, low internal resistance and flexible control through power electronic conversion. This paper proposes a main power supply of hybrid Wind Generator (WG)–SC within the train station for feeding the traction onboard SC through specified limited feeding transit durations. Onboard SCs provide the train with the requested start–up self–energy. The hybrid WG–SCs system is an environmental–friendly source that enables the independency on national grid and guarantees an efficient bidirectional power transfer for energy management with enhanced dynamic performance. Therefore, the dynamic modelling and the experimental analysis of the modern hybrid WG–SCs used for managing the charge/discharge operation of SCs at Unity Power Factor (UPF) mode are presented. For this purpose, the Port–Controlled Hamiltonian (PCH) methodology is deduced and explicitly presented. Simulation results, via MATLAB™, reveal that the proposed PCH control methodology can be successfully implemented to ensure acceptable system dynamic behavior. Numerical results are validated with experimental measurements to investigate the significance of the PCH approach for the energy management operation in eco-tractions.

To investigate the application of hybrid technology in scenarios with high concern for system self-accommodation rapidity, an operationally flexible configuration based on SOFC and twin-shaft free turbine engine has been proposed in this research. The corresponding turbomachinery matching expressions are integrated with thermodynamic and electrochemical descriptions in the novel model so that mechanical equilibrium running states can be guaranteed throughout design and off-design analysis. Inclusion of SOFC and combustor pressure losses (3% and 5%) in high-pressure turbine design can effectively alleviate poor turbine operation and improve cell voltage by 54%, thermal efficiency by 31% under design conditions. For the hybrid gas generator, an integrated calculation algorithm has been developed to satisfy both flow and work compatibility requirements, which essentially constitute a closed binary nonlinear equation set after allowed assignment. The coupling of SOFC not only affects along stream parameters, but also imposes restrictions on the solution scope of the equation set from both horizontal and vertical directions. The flow compatibility between the two mechanically separated turbines finally enables the depiction of equilibrium running line/point on turbomachinery characteristics. With one of the appropriate pairing designs of turbines, the running line can pass through the point of rated rotational speed and compression ratio, where a thermal efficiency of 49.3% is achieved.

About 72 million households in rural India do not have access to electricity and rely primarily on traditional biofuels. This research investigates how rural electrification could be achieved in India using different energy sources and what the effects for climate change mitigation could be We use the. Regional Energy Model (REM) to develop scenarios for rural electrification for the period 2005-2030 and to assess the effects on greenhouse gas emissions, primary energy use and costs. We compare the business-as-usual scenario (BAU) with different electrification scenarios based on electricity from renewable energy, diesel and the grid. Our results indicate that diesel systems tend to have the highest CO2 emissions, followed by grid systems. Rural electrification with primarily renewable energy-based end-uses could save up to 99% of total CO2 emissions and 35% of primary energy use in 2030 compared to BAU. Our research indicates that electrification with decentralised diesel systems is likely to be the most expensive option. Rural electrification with renewable energy tends to be the most cost-effective option when end-uses are predominantly based on renewable energy, but turns out to be more costly than grid extensions when electric end-use devices are predominantly used. This research therefore elaborates whether renewable energy is a viable option for rural electrification and climate change mitigation in rural India and gives policy recommendations. (C) 2009 Elsevier Ltd. All rights reserved.

While the available resource in terms of waste process heat in the UK is substantial, there are a wide variety of issues to consider and barriers to overcome in order to realise its potential. This paper discusses one particular factor, namely public opinion. We describe the results of two focus groups with a potential domestic client group, namely elderly people, and the postal questionnaire responses of 323 individuals living in the proximity of a large potential heat source, namely the Corus steel-works in Port Talbot, Wales. While those questioned were broadly supportive of the idea of district heating, particularly if this would involve reductions in domestic heating costs, both the qualitative and quantitative work revealed significant concern about contractual lock-in. In contrast, the stability of long-term demand is highly valued by those responsible for the supply-side. We also observe some gender differences in first reactions to district heating and the role of environmental commitment. We conclude that while the results imply that an appeal to the environmental performance of district heating with waste heat may facilitate acceptance, trust-building and price inducements will also be required to overcome end-user concerns.

A polymer electrolyte fuel cell stack of 2 kW of peak power has been designed, manufactured and tested. Such a fuel cell stack has been envisaged to be applied for manned lunar exploration missions, as secondary energy source for both mobile vehicles and fixed power plants. The stack has been bread-boarded in order to test and demonstrate the technology. The following constraints have been considered during the study: (i) operation with pure hydrogen and oxygen (ii) low humidification levels (iii) use of commercial Membrane Electrode Assemblies. The breadboard has been made consisting of two modules, each of 500 W of nominal power. Specific tests have been conducted to prove the effect of gravity on the breadboard performance and verify its ability to follow variable load profiles over time, representative of different lunar surface exploration missions. The breadboard has shown a good performance during the test campaign, even if some failures of the Membrane Electrode Assemblies have been observed. The study has demonstrated the high performance of the developed stack and the potential of fuel cell technology for use in future human lunar exploration missions. At the same time, it has highlighted serious criticalities related to the reliability and robustness of the commercially available Membrane Electrode Assemblies, which need to be investigated further, before the use of this technology in a real space exploration mission can be possible.

Abstract Finding cost effective retrofits for heat exchanger networks remains a challenge. Whilst it is often straightforward to find retrofit changes to an existing network that can improve energy performance, in practice such changes are most often uneconomic. This paper will present an approach to heat exchanger network retrofit around a fixed network structure. Network energy performance is improved through the selective use of heat transfer enhancement. A sensitivity analysis is used to find the most effective heat exchangers to enhance in order to improve the performance of the overall network. The sensitivity analysis used is an extension of a previous sensitivity analysis that was introduced to study network flexibility. The proposed method is applicable for heat exchanger networks involving streams with linear or non-linear physical properties. The enhancement of the most sensitive heat exchangers and avoiding new equipment, together with piping and civil engineering costs, allow much more cost-effective heat exchanger network retrofit.

Abstract The use of thermal energy storage (TES) systems for solar heating and cooling applications has received considerable attention in recent decades because it has a high potential in energy savings. Phase change materials (PCMs) can store large amount of energy per mass unit compared with other TES materials. Nevertheless, the selection of the suitable PCM for each application is a key issue in any TES system design. The most important properties to take into account to select a PCM are the melting and solidification temperature, the phase change enthalpy and the stability after several thermal cycles. In this paper, d -mannitol was a candidate material to be tested as PCM in a solar cooling application due to its melting point (167 °C) and a relatively high enthalpy (316.0 kJ/kg). The experiments performed by DSC have shown that the d -mannitol presents polymorphic structural changes and, therefore, its thermal properties are not always the same. Depending on the polymorphic phase obtained, d -mannitol has different melting temperature. This behaviour was corroborated in a storage tank, where it may be seen that the cooling rate of the d -mannitol is a key parameter in the formation of the different polymorphic phases.

Abstract The energy-water nexus presents important implications at seasonal scale. For instance, electricity prices and streamflow have complex seasonal patterns and changes in both may adversely impact hydropower plant revenue. In order to quantify the effect of changes in price and water seasonality on future revenue distribution and its related uncertainty, we consider the case of a run-of-the-river plant. To this end, we integrate a hydrologic model, a hydropower model, two glacier inventories, six climate scenarios and five electricity price seasonal scenarios. Our results show that the impact of climate change on streamflow of the considered run-of-the-river plant will decrease the revenue by 20% in a business-as-usual price scenario. This decrease is mostly driven by a reduction of the annual streamflow due to glacier shrinkage rather than by the evolution of seasonality. From this perspective, the difference between the various climate scenarios is low. In contrast, change in electricity price seasonality induces a marked uncertainty in revenue. According to our scenarios, which assume no change in the mean annual electricity price, a change in price seasonality may indeed exacerbate or mitigate the impact of climate by 50 or 33% respectively, compared to the business-as-usual scenario. Our analysis highlights the need for considering intra-annual dynamics when investigating the energy-water nexus.