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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.

Vineyards cover about eight millions of hectares worldwide and their annual pruning generates a large amount of ligno-cellulosic biomass, potentially available for industrial and energy use. Commercial pruning residue harvesters are now available, which may allow cost-effective recovery. The study aimed at determining the quantity and the quality of pruning residues potentially derived from vineyard management. Data were obtained from 17 fields in Northern and Central Italy. Fields were harvested with seven different machines. The experimental design adapted to the necessities of field trials, but was adequate for testing the main sources of variability. Net residue yield varies around 1 oven dry tonne per hectare, with minor differences between grape varietals and harvesting technologies. Losses are still high, and are generally related to ineffective management techniques. Moisture content at harvest varies between 40% and 45%, whereas the higher heating value is slightly lower than that of forest fuels. Comminuted vineyard residues are unsuitable for firing residential boilers, due to the frequent presence of oversize and/or undersize particles. The application of pesticides does not result in any significant contamination with noxious chemicals, because these products are almost completely weathered before residues are recovered. In wine-producing regions, the recovery of vineyard pruning residue may represent a substantial source of industrial bio-fuel. © 2011 Elsevier Ltd.

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.

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 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.

In this paper we deal with the problem of efficiently optimizing microgrid operations while satisfying a time-varying request and operation constraints. Microgrids are subsystems of the distribution grid comprising sufficient generating resources to operate in isolation from the main grid, in a deliberate and controlled way. The Model Predictive Control (MPC) approach is applied for achieving economic efficiency in microgrid operation management. The method is thus applied to an experimental microgrid located in Athens, Greece: experimental results show the feasibility and the effectiveness of the proposed approach.

Abstract Industrial systems management is nowadays increasingly devoted to improve the control of most critical production aspects. In this context, the performance of all the systems involved in production processes have to be measured and analysed in order to get better insights in terms of potential production and quality improvements as well as energy savings. In order to evaluate the performance of a certain system, a possible and effective way is to compare it with data from similar systems, thus to conduct a benchmark analysis. In the area of energy management, although the compressed air system (CAS) is one of the most important and energy consuming services within industrial plants, enterprises often have difficulties understanding and appreciating the entity of potential benefits coming from the improvement of its energy efficiency. The present paper aims at developing a new benchmark analysis for compressed air systems in industrial plants. The proposed methodology starts from the KPIs (Key Performance Indicators) already available in the scientific literature for CASs’ energy performance and is mainly based on the analysis of a huge real dataset collected from over 15,000 energy audits made on a wide range of different companies, all related to produced quantity of compressed air and energy consumed by CASs. Collected data present some limitations and related improvements and corrective actions have been undertaken and are presented in the followings. Data analyses have been followed by complementary surveys regarding compressed air systems’ use, maintenance and monitoring practices performed within several Italian enterprises and aimed at enhancing and creating a more reliable baseline for benchmarking.