Optimization of a wind-power fuel-cell hybrid system in an autonomous electrical network environment

Stability considerations associated with intermittency prevent high wind energy penetration in small electrical networks. The case of the islands of the Aegean is presented. [Ntziachristos L, Kouridis C, Samaras Z, Pattas K. A wind-power fuel-cell hybrid system study on the non-interconnected Aegean islands grid. Renewable Energy 2005;30(10):1471–1487] proposed a wind turbine(WT)–fuel-cell hybrid as a means to store wind energy and increase penetration in these islands. The effect of network restraints was, however, not included in that study. Simulation results including network restrictions prove that when network restrictions are relatively “strict”, hybridizing a WT using the scheme presented in the same paper will indeed increase the WT's energy output. However, in the case of “lenient” network restrictions, that hybridization scheme will in fact decrease the WT's energy output. Moreover, the system configurations presented that paper could not achieve financial viability at current electricity prices due to high capital costs. Two alternative operating principles for the hybrid system are presented in this study. These operating principles significantly improve the hybrid system's energy performance even under “lenient” network restrictions. In some cases, these operating principles manage to yield hybrid systems that are financially viable assuming current electricity prices.     

New scenario of the non-conventional renewable energies on Chile after the incentives created on the “Short Law I”

Non-conventional renewable energies have never played an important role in the Chilean energy generation system, mainly due to the economic barriers that actually exists on our country for the inclusion of these kinds of technologies. Nevertheless, the use of renewable energy system technologies have started to be an interesting issue for the Chilean government, and for that reason, the last modification of the Energy Law during 2004, usually known as “Short Law I”, introduced the first direct incentive to renewable energy generation (specifically in the art. 71-7).In this work we analyze in detail the modification on the electric law we mentioned before, especially for geothermal and wind power generation, and we compare the economic incentive generated with the new law and the differences between the real energy costs using renewable energy systems technologies and the current energy price in Chile. It is clear from the analysis that the total incentives do not cover more than 8.3% of the price differences between incomes and costs.     

Pre-feasibility study of stand-alone hybrid energy systems for applications in Newfoundland

A potential solution for stand-alone power generation is to use a hybrid energy system in parallel with some hydrogen energy storage. In this paper, a pre-feasibility study of using hybrid energy systems with hydrogen as an energy carrier for applications in Newfoundland, Canada is explained. Various renewable and non-renewable energy sources, energy storage methods and their applicability in terms of cost and performance are discussed. HOMER is used as a sizing and optimization tool. Sensitivity analysis with wind speed data, solar radiation level, diesel price and fuel cell cost was done. A remote house having an energy consumption of 25 kW h/d with a 4.73 kW peak power demand was considered as the stand-alone load. It was found that, a wind–diesel–battery hybrid system is the most suitable solution at present. However, with a reduction of fuel cell cost to 15% of its current value, a wind–fuel cell system would become a superior choice. Validity of such projection and economics against conventional power sources were identified. Sizing, performance and various cost indices were also analyzed in this paper.     

New sunshine project and new trend of PV R&D program in Japan

The development and application of new energy resources seems to promise significant effects in tackling the problems of reassembling Japan's feeble energy supply structure and of the damages done to global environment by acid rain, carbon dioxide and its offspring known as greenhouse effect. Now, the development of new energy is promoted under the ‘New Sunshine Program” started in 1993, following “Sunshine Project” started in 1974. As a result of technical development and legislative supports, the introduction and dissemination of photovoltaic (PV) power generation has been promoted recently. To promote new energy introduction in Japan including PV power generation, a “Basic Guidelines for New Energy Introduction” was decided upon in a December 1994 Cabinet meeting. In the “Guidelines” a policy was formulated whereby the introductory targets for PV power generation were set at 400MW in 2000 and 4,600MW in 2010. The state, local public bodies, and the private sector are cooperatively to promote accelerated introduction.Since its founding in October 1980, NEDO (New Energy and Industrial Technology Development Organization) has, as the central organization in Japan for development of new energy including PV power generation, strived to meet this obligation, with assistance from various spheres. The thesis is outline of the “New Sunshine Program” and Japan's contribution in the technological development and dissemination of PV power generation being made on the initiative of NEDO.     

Estimation of the energy of a PV generator using artificial neural network

The integration of grid-connected photovoltaic (GCPVS) systems into urban buildings is very popular in industrialized countries. Many countries enhance the international collaboration efforts which accelerate the development and deployment of photovoltaic solar energy as a significant and sustainable renewable energy option. A previous method, based on artificial neural networks (ANNs), has been developed to electrical characterisation of PV modules. This method was able to generate V–I curves of si-crystalline PV modules for any irradiance and module cell temperature. The results showed that the proposed ANN introduced a good accurate prediction for si-crystalline PV modules performance when compared with the measured values. Now, this method, based on ANNs, is going to be applied to obtain a suitable value of the power provided by a photovoltaic installation. Specifically this method is going to be applied to obtain the power provided by a particular installation, the “Univer generator”, since modules used in these works were the same as the ones used in this photovoltaic generator.     

“Energy Tower” combined with pumped storage and desalination: Optimal design and analysis

The “Energy Tower” (ET) is a power plant project which uses hot dry air and seawater to produce electricity. An optimized design of a system that is a combination of an ET, pumped storage and seawater desalination plant is considered. A model set covering each subsystem, and results of the optimized design for a project in the area of Eilat are presented. The additional benefit from combining the systems comes from an efficient use of the energy in the brine water coming from the desalination process, and from using pumped storage in an unconventional way. The benefits of the combined system lead to an increase of 14% in the annual net profit, compared to the sum of profits from optimally designed stand-alone systems.     

Model simplification and optimization of a passive wind turbine generator

In this paper, the design of a “low cost full passive structure” of wind turbine system without active electronic part (power and control) is investigated. The efficiency of such device can be obtained only if the design parameters are mutually adapted through an optimization design approach. For this purpose, sizing and simulating models are developed to characterize the behavior and the efficiency of the wind turbine system. A model simplification approach is presented, allowing the reduction of computational times and the investigation of multiple Pareto-optimal solutions with a multiobjective genetic algorithm. Results show that the optimized wind turbine configurations are capable of matching very closely the behavior of active wind turbine systems which operate at optimal wind powers by using a MPPT control device.     

Passive solar heating of buildings using a transwall structure

Passive solar heating systems can utilize a number of design approaches, but the most prominent ones are those employing “direct gain” or a “Trombe thermal storage wall”. In this work we propose a new passive system employing a “transwall”, which is a partially transparent thermal storage wall placed adjacent to a window admitting solar energy. Part of the solar energy is absorbed within the transwall, and the remaining part is transmitted to the interior of the room. The transwall is architecturally more attractive than the completely absorbing Trombe wall, since it admits light to the room and allows the occupants to see out through the window without glare and overheating problems of direct gain systems.Calculations using thermal network models and based on reasonable assumptions for relative comparisons have been used to compare thermal performance of transwall, Trombe wall, and direct gain systems. The analysis shows that the transwall system can be expected to have thermal performance very close to or exceeding the other systems, depending on how effectively convective heat transfer is quenched in the thermal storage medium.The important question of visual clarity for the transwall system has been evaluated for a prototype by photographing a scene with and without optical transmission through the structure. Optical distortion is minimal in the transwall transmission photograph.     

Matching economical, energetic and environmental benefits: An analysis for hybrid CHCP-heat pump systems

The optimization of design and operation of combined heat, cooling and power systems usually leads to select different plant lay-outs and size of components, depending on the adopted optimization criterion (maximum profit or energy saving or minimum environmental impact). This occurs when the current energy prices and the normative provisions supporting cogeneration are not able to coincide with the specific customer’s interest and the overall “social interest” for a reduction in energy consumption and in pollutants’ emissions. At EU level, polygeneration is considered to have a large potential for residential and commercial buildings district network, for the tertiary sector and for industrial applications. In such applications, it is often convenient to integrate the trigeneration system with a reversible heat pump, because of a low ratio between electric demand and that for heating and cooling. In this paper, the design and operation of such hybrid systems is discussed. The results achievable through different operation modes are compared and, with reference to a 600-rooms hotel and a 300-beds hospital in Italy, the effects on plant design from an hour-by-hour optimization of plant operation are assessed. Finally, the need for a flexible support system for cogeneration plants is put into evidence and some criteria are listed for an effective regulation.     

“Key” sectors in final energy consumption: an input–output application to the Spanish case

In this paper we analyze the determination of “key” sectors in the final energy consumption. We approach this issue from an input–output perspective and we design a methodology based on the elasticities of the demands of final energy consumption. As an exercise, we apply the proposed methodology to the Spanish economy. The analysis allows us to indicate the greater or lesser relevance of the different sectors in the consumption of final energy, pointing out which sectors deserve greater attention in the Spanish case and showing the implications for energy policy.     

Simplified reactive power management strategy for complex power grids under stochastic operation and incomplete information

In the current released energy market, the large-scale complex transmission networks and the distribution ones with dispersed energy sources and “intelligent” components operate under uncertainties, stochastic and prior incomplete information. A safe and reliable operation of such complex power grids is a major issue for system operators. Under these circumstances an online reactive power management strategy with minimum risk concerning all uncertain and stochastic parameters is proposed. Therefore, new concepts such as reactive power-weighted node-to-node linking and reactive power control capability are introduced. A distributed and interconnected stochastic learning automata system is implemented to manage, in a unified and unique way, the reactive power in complex power grids with stochastic reactive power demand and detect the vulnerable part. The proposed simplified strategy can also consider more stochastic aspects such as variable grid’s topology. Results of the proposed strategy obtained on the networks of IEEE 30-bus and IEEE 118-bus systems demonstrate the effectiveness of the proposed strategy.     

Development of a test facility for photovoltaic-diesel hybrid energy systems

To quantify the potential for performance improvements of photovoltaic-diesel (PV-diesel) hybrid energy systems, a test facility has been installed at the Centre for Renewable Energy Systems Technology. The research facility is part of the cooperative program to develop improved power conditioning systems for the provision of electricity in remote areas (ACRE Project 4.1). A customised control interface has been developed using the control and data acquisition software, LabVIEW. The graphical user-interface supports the automatic or manual definition of control parameters, which allows the system designer to apply optimal control methods for the management of PV-diesel hybrid energy systems. Continuously monitored weather data supports the integration of photovoltaic resource and load demand forecasts as part of the control strategy. The paper describes the developed test facility and discusses the potential for performance improvements of stand-alone renewable energy systems, which can be achieved through the application of “intelligent” energy management strategies.     

An analytical method for reflected flux density calculations

Conception, evaluation and real time control of solar “power tower” systems require the use of fast and accurate computer programs for calculating the flux density distributions on the receiver. Since the classical methods of “cone optics” and “hermite polynomial expansion” have some limitations of speed and accuracy, we have built an analytical model for calculating the convolution of the solar brightness distribution with the principal image of a heliostat (i.e. the fictive image for a “point sun”). We first characterize a principal image of a focusing heliostat by its shape and its geometrical concentration factor. Then this image is projected back onto the central plane (which passes through the center of the mirror), and considered as a flat reflecting surface. And the problem is reduced to density calculation for a flat heliostat. For each point of the receiver, the density of flux reflected by a heliostat is obtained by direct resolution of a convolution integral. The different formulations used to express the density function correspond to the various types of intersections between the image of the solar disk for the considered point and the principal image of the heliostat. Confrontation of this method with a program based on “cone optics” shows a good concordance of results and a strong decrease of computation time. We want to apply this method to the existing “THEMIS” solar plant built in France and to compare our results with real observations. Our density calculation programs will help conceiving fields of focusing heliostats for a new generation of power systems (gaz turbine systems).     

An improved computer code for the simulation of solar heating systems

A generalised solar energy simulation code, which represents a significant improvement over fixed step iterative simulation codes, is presented. The key features of the code are the simultaneous solution of all differential equations arising from closed loops in the system, and the technique for advancing the simulation from “control function” to “control function”. Computer time is minimised by the use of sparse matrix techniques together with automatic time step control generated from an error bound estimate. The application of the improved code to the simulation of solar energy systems is demonstrated on two example problems. In the first problem, emphasis is placed on predicting the temperatures of the fluids within the system and the controller actions, while in the second problem the emphasis is on predicting long-term system performance. The simulation results of both these problems demonstrate that the improved code is suitable for both detailed system control and long-term system performance studies.     

Energy saving and emission reduction revolutionizing China's environmental protection

Great pressure to curb carbon emission and increased need for energy have forced China to develop an “energy saving and emission reduction” (ESER) plan. ESER has become China's basic national policy, and a guideline for China's energy and environmental issues during the 11th Five-Years Plan (2006–2010). ESER represents a recalibration of China's economic model, moving away from growth-at-all-cost in favor of a more “balanced and sustainable” output. In 2007, China's GDP grew by 11.4%, but emission of COD and SO₂ decreased by 3.14% and 4.66% respectively compared to 2006, energy consumption for each unit of GDP declined by 3.27% also compared to 2006. ESER is also the engine behind reform of China's traditional administrative system which has always favored economic growth over environmental protection. The ESER accountability system sets green efforts as a decisive factor in determining the career prospects of local leaders. Also, China's State Environmental Protection Agency has been upgraded to the Ministry of Environmental Protection, gaining cabinet status for the first time. A greener future relative to the previous three decades can be anticipated with confidence for China provided that the best practices enunciated by ESER are taken to heart by policymakers.     

Energy recovery from industrial waste of a confectionery plant by means of BIGFC plant

The search of environment friendly solutions for waste management, along with increasing costs and recent regulations on waste disposal, leads toward the recovery of energy and requires research activities related to plant definition and thermo-economic comparison. On the other hand, energy recovery from waste has never been an easy task. The high pollutant level in waste combustion gases requires low maximum temperatures in thermodynamic cycles thus affecting the efficiency of the “heat to electricity” conversion process. The recent progress of high temperature fuel cells seems to bring a significant change in this scenario, thanks to the feasible combination with advanced gasification systems. A thermo-economic comparison of different solutions for energy recovery from industrial waste is reported, considering an advanced dual bed gasification-MCFC integrated plant. The solution has been applied to a confectionery plant. Even if this system seems to promise high thermodynamic efficiency, a lot of effort in research is necessary for technical analysis of the advanced plant open issues and for the thermo-economic evaluation of potential advantage over consolidated systems. The thermodynamic analysis has been conducted interfacing Aspen⁺ flowsheets developed with the integration of a proprietary numerical code. The definition of a complex plan of costs would have been presumptuous at this stage of the development; therefore, a reverse economic approach has been used and is suggested by the authors; a specific solver has been implemented for this purpose. An extensive survey of the confectionary plant has been conducted considering the present energy system, the current supplies, and the trends of the required energy needs. The results show that the proposed advanced energy system can represent a valid solution for both industrial waste management and for integration in energy supply.     

An approach to develop space solar power as a new energy system for developing countries

The idea of space solar power proposed by Glaser was explained as a set of a solar power power station in geostationary earth orbit to transmit microwave power and a ground station to receive the microwave power. Most of the ideas and concepts since Glaser used the same context. On the other hand, Collins et al. (Proceedings SPS '91, pp. 132–141, 1991) introduced the concept of microwave “fuel” to assess the commercial relations of power from space, in which space solar power stations are considered to sell microwave power to any unspecified rectenna. This concept changed the theoretical context of “power from space” to an industrial and economic relation of producers and buyers of an industrial product. This new context has been applied to the SPS 2000 conceptual study. As a result, if 2.45 GHz microwave power transmission is used, each rectenna can be planned and engineered independently from the space sector by local users, especially in developing countries, who are familiar with such activities as introducing solar energy systems.     

Design of a photovoltaic electric power system for an indian village

Photovoltaic generation and electrochemical storage of electrical power offer an attractive possibility for the electrification of a village that is normally considered “uneconomic” for electrification by the conventional REP. The modular nature of both solar cells and storage batteries make it possible to use either a centralised or a decentralised system within a village. A critical analysis of the electrical energy requirements of the village including its domestic, agricultural, community and street lighting needs and its technoeconomic aspects is therefore to be made for the most cost effective and maximum beneficial choice between (a) the centralised village energy centre or (b) highly decentralised roof top units within the village. A methodology is first developed in this paper to investigate this problem on the basis of balance of systems (BOS) cost per peak watt and is then applied to a typical village in West Bengal, India. The analysis indicates that the centralised village energy centre approach is about five times more cost-effective than the roof top approach under the assumed conditions.     

The Fundamentals of Integrating “the commons”: Application as community tissue or urban implant

Clarifying the means by which we define and shape the commons, can become the platform from which we can seek to achieve community-scale integration in service to principles of sustainability. This paper presents the formulation of energy-related environmental variables — sun, light, wind and water — in “envelope form” for purposes of modeling alternative integrative patternings of communities as “tissue on the land”. Such modeling yields prototype designs of urban districts, urban blocks and/or individual buildings whose designs capitalize on passive energy manipulation as a “first order” response, thus structuring strategies for the integration of efficient “second order” metabolic systems which together provide the technical base for energy-related resource management.