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Behnke M.,DNV KEMA Energy and Sustainability | Ellis A.,Sandia National Laboratories
Conference Record of the IEEE Photovoltaic Specialists Conference | Year: 2013

As an important part of evaluating the transmission and distribution system impacts of interconnecting new generation sources, network operators must assess the impact of these sources on fault interrupting capabilities of automatic switching devices and protective relay coordination for balanced and unbalanced faults on the network. A growing component of these new generation sources is solar photovoltaic-based systems. Modeling of these sources for short circuit studies is complicated by the non-linear control characteristics of their associated inverters. These characteristics preclude the use of linear circuit analysis techniques based on Thévenin equivalents that are the prevalent methodologies relied upon in most commercial short circuit analysis tools. This paper contrasts the physical characteristics of well-understood synchronous generator technology with that of modern-day PV inverter technology. Limitations of commercial short circuit analysis tools for addressing solar PV generation systems, and recommendations for development of industry consensus standard analysis methods, are presented. © 2013 IEEE. Source

Stam A.F.,DNV KEMA Energy and Sustainability
Advances in Materials Technology for Fossil Power Plants - Proceedings from the 7th International Conference | Year: 2014

The EU NextGenPower-project aims at demonstrating Ni-alloys and coatings for application in high-efficiency power plants. Fireside corrosion lab and plants trials show that A263 and A617 perform similar while A740H outperforms them. Lab tests showed promising results for NiCr, Diamalloy3006 and SHS9172 coatings. Probe trials in six plants are ongoing. A617, A740H and A263 performed equally in steamside oxidation lab test ≤750°C while A617 and A740H outperformed A263 at 800°C; high pressure tests are planned. Slow strain rate testing confirmed relaxation cracking of A263. A creep-fatigue interaction test program for A263 includes LCF tests. Negative creep of A263 is researched with gleeble tests. A263 Ø80 - 500mm trial rotors are forged with optimized composition. Studies for designing and optimizing the forging process were done. Segregation free Ø300 and 1,000mm rotors have been forged. A263 - A263 and A293 - COST F rotor welding show promising results (A263 in precipitation hardened condition). Cast step blocks of A282, A263 and A740H showed volumetric cracking after heat treatment. New 'as cast' blocks of optimized composition are without cracks. A 750°C steam cycle has been designed with integrated C02 capture at 45% efficiency (LHV). Superheater life at ≤750°C and co-firing is modeled. Copyright © 2014 Electric Power Research Institute, Inc. Distributed by ASM International®. All rights reserved. Source

Chaturvedi S.K.,Old Dominion University | Gagrani V.D.,DNV KEMA Energy and Sustainability | Abdel-Salam T.M.,East Carolina University
Energy Conversion and Management | Year: 2014

Direct expansion solar assisted heat pump systems (DX-SAHP) have been widely used in many applications including water heating. In the DX-SAHP systems the solar collector and the heat pump evaporator are integrated into a single unit in order to transfer the solar energy to the refrigerant. The present work is aimed at studying the use of the DX-SAHP for low temperature water heating applications. The novel aspect of this paper involves a detailed long-term thermo-economic analysis of the energy conservation potential and economic viability of these systems. The thermal performance is simulated using a computer program that incorporates location dependent radiation, collector, economic, heat pump and load data. The economic analysis is performed using the life cycle cost (LCC) method. Results indicate that the DX-SAHP water heaters systems when compared to the conventional electrical water heaters are both economical as well as energy conserving. The analysis also reveals that the minimum value of the system life cycle cost is achieved at optimal values of the solar collector area as well as the compressor displacement capacity. Since the cost of SAHP system presents a barrier to mass scale commercialization, the results of the present study indicating that the SAHP life cycle cost can be minimized by optimizing the collector area would certainly be helpful in lowering, if not eliminating, the economic barrier to these systems. Also, at load temperatures higher than 70 C, the performance of the single stage heat pump degrades to the extent that its cost and efficiency advantages over the electric only system are lost. © 2013 Elsevier Ltd. All rights reserved. Source

Hermeling C.,Center for European Economic Research | Loschel A.,Center for European Economic Research | Loschel A.,University of Heidelberg | Mennel T.,DNV KEMA Energy and Sustainability
Energy Policy | Year: 2013

This paper introduces a new method for stochastic sensitivity analysis for computable general equilibrium (CGE) model based on Gauss Quadrature and applies it to check the robustness of a large-scale climate policy evaluation. The revised version of the Gauss-quadrature approach to sensitivity analysis reduces computations considerably vis-à-vis the commonly applied Monte-Carlo methods; this allows for a stochastic sensitivity analysis also for large scale models and multi-dimensional changes of parameters. In the application, an impact assessment of EU2020 climate policy, we focus on sectoral elasticities that are part of the basic parameters of the model and have been recently determined by econometric estimation, alongside with standard errors. The impact assessment is based on the large scale CGE model PACE. We show the applicability of the Gauss-quadrature approach and confirm the robustness of the impact assessment with the PACE model. The variance of the central model outcomes is smaller than their mean by order four to eight, depending on the aggregation level (i.e. aggregate variables such as GDP show a smaller variance than sectoral output). © 2012. Source

Mullen J.D.,University of Georgia | Lamsal M.,DNV KEMA Energy and Sustainability | Colson G.,University of Georgia
Environmental Science and Technology | Year: 2013

This research draws on and expands previous studies that have quantified the costs and benefits associated with conventional roofs versus green roofs. Using parameters from those studies to define alternative scenarios, we estimate from a private, public, and social perspective the costs and benefits of installing and maintaining an extensive green roof in Atlanta, GA. Results indicate net private benefits are a decreasing function of roof size and vary considerably across scenarios. In contrast, net public benefits are highly stable across scenarios, ranging from $32.49 to $32.90 m -2. In addition, we evaluate two alternative subsidy regimes: (i) a general subsidy provided to every building that adopts a green roof and (ii) a targeted subsidy provided only to buildings for which net private benefits are negative but net public benefits are positive. In 6 of the 12 general subsidy scenarios the optimal public policy is not to offer a subsidy; in 5 scenarios the optimal subsidy rate is between $20 and $27 m-2; and in 1 scenario the optimal rate is $5 m-2. The optimal rate with a targeted subsidy is between $20 and $27 m-2 in 11 scenarios and no subsidy is optimal in the twelfth. In most scenarios, a significant portion of net public benefits are generated by buildings for which net private benefits are positive. This suggests a policy focused on information dissemination and technical assistance may be more cost-effective than direct subsidy payments. © 2013 American Chemical Society. Source

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