Centralised and distributed electricity systems

Because of their high level of integration, centralised energy supply systems are vulnerable to disturbances in the supply chain. In the case of electricity especially, this supply paradigm is losing some of its appeal. Apart from vulnerability, a number of further aggravating factors are reducing its attractiveness. They include the depletion of fossil fuels and their climate change impact, the insecurities affecting energy transportation infrastructure, and the desire of investors to minimise risks through the deployment of smaller-scale, modular generation and transmission systems.     

Historical costs of coal-fired electricity and implications for the future

We study the cost of coal-fired electricity in the United States between 1882 and 2006 by decomposing it in terms of the price of coal, transportation cost, energy density, thermal efficiency, plant construction cost, interest rate, capacity factor, and operations and maintenance cost. The dominant determinants of cost have been the price of coal and plant construction cost. The price of coal appears to fluctuate more or less randomly while the construction cost follows long-term trends, decreasing from 1902 to 1970, increasing from 1970 to 1990, and leveling off since then. Our analysis emphasizes the importance of using long time series and comparing electricity generation technologies using decomposed total costs, rather than costs of single components like capital. By taking this approach we find that the history of coal-fired electricity suggests there is a fluctuating floor to its future costs, which is determined by coal prices. Even if construction costs resumed a decreasing trend, the cost of coal-based electricity would drop for a while but eventually be determined by the price of coal, which fluctuates while showing no long-term trend.     

Solar photovoltaic electricity: Current status and future prospects

We review the technical progress made in the past several years in the area of mono- and polycrystalline thin-film photovoltaic (PV) technologies based on Si, III-V, II-VI, and I-III-VI₂ semiconductors, as well as nano-PV. PV electricity is one of the best options for sustainable future energy requirements of the world. At present, the PV market is growing rapidly at an annual rate of 35-40%, with PV production around 10.66 GW in 2009. Si and GaAs monocrystalline solar cell efficiencies are very close to the theoretically predicted maximum values. Mono- and polycrystalline wafer Si solar cells remain the predominant PV technology with module production cost around $1.50 per peak watt. Thin-film PV was developed as a means of substantially reducing the cost of solar cells. Remarkable progress has been achieved in this field in recent years. CdTe and Cu(In,Ga)Se₂ thin-film solar cells demonstrated record efficiencies of 16.5% and almost 20%, respectively. These values are the highest achieved for thin-film solar cells. Production cost of CdTe thin-film modules is presently around $0.76 per peak watt.     

Competitiveness,role, and impact of microalgal biodiesel in the global energy future

This paper examines the competitiveness, role, and impact of microalgal biodiesel in the 21st century using a global energy system model with a detailed technological representation. The major conclusions are the following. First, the competitiveness of microalgal biodiesel decreases as CO₂ stabilization constraints become more stringent. The share of microalgal biodiesel and renewable jet fuel produced from it in total global final energy consumption over the time horizon 2010–2100 is 5.1% in the case without CO₂ constraints compared with 3.9% and 0.7% in the case of CO₂ stabilization at 550 ppmv and 400 ppmv, respectively. This is because production and combustion of microalgal biodiesel release as much CO₂ as is captured from anthropogenic sources and assimilated by microalgae and because CO₂ prices raised by stringent CO₂ stabilization constraints make the economics of microalgal biodiesel unattractive. Second, the competitiveness of microalgal biodiesel is also greatly affected by microalgal production cost and microalgal lipid yield. Under a 400 ppmv CO₂ stabilization constraint, a 50% microalgal production cost decrease leads to increase in total global microalgal biodiesel production over the time horizon by a factor of 6.5, while a 50% microalgal lipid yield increase leads to increase in it by a factor of 4.5. Third, microalgal biodiesel plays an important role in satisfying the energy demand in the transport sector, thereby replacing petroleum products and Fischer–Tropsch synfuels. An increasing proportion of microalgal biodiesel is converted into renewable jet fuel over time to be used as a fuel for aircraft. Fourth, either without CO₂ constraints or under the 550 ppmv CO₂ stabilization constraint, the participation of microalgal biodiesel in the global energy market would have a large impact on the global energy supply and consumption structure. This is not only because of its substitution for other forms of final energy, but also because of the need to satisfy the demand for CO₂ for microalgal production.     

Shaping the future of global energy delivery

Globally, the increasing power demand is coupled with environmental constraints and strong competition that require advanced solutions for global power transmission. System reliability and congestion relief are imperative under dynamic market conditions to ensure that transmission systems provide a steady return on investment and cash flow as well as operate with the flexibility and security that will be required to serve future demand and load growth. Given all of the factors that must be balanced, the one certainty is that new technology will be a key enabler to move transmission investment forward and increase capacity. A few of the innovations that have the potential to shape the future of the global power system are already available or will soon be commercially available. Some, but definitely not all, of these new technologies are briefly discussed in this article including flexible AC transmission system (FACTS), HVDC transmission, short current limiters, overhead lines, gas insulated transmission lines, gas insulated switchgear, and grid connected wind generation.     

Load management in municipal electricity systems

Load management is one means of reducing maximum electricity load, and hence also the cost of electricity. In Sweden, the amount charged during the maximum load hour might be about 200 times higher than the standard charge for one kilowatt-hour. If the load could be reduced by certain equipment in factories and buildings, the need for new power stations and higher capacity in the grid would also be decreased. Using electricity load data for one full year and a short computer program, this paper shows by how much the load could be reduced by postponing demand. If part of the load could be postponed by only one hour, this part may need to be only very small for maximum benefit. If longer time segments were practicable, larger chunks could be transferred. The main result of the study is, however, that load management in practice is a very subtle task if an optimal solution is to be achieved. © 1997 John Wiley & Sons, Ltd.     

Electric power systems: past, present, and future

The author mostly discusses the future of electric power systems, mentioning the past primarily to point out mistakes and so, hopefully, to avoid repeating them. The author discusses frequency and voltage control, complexity of systems, energy sources, and structure of the electric utility industry     

Geothermal energy and the environment: The global experience

The conflict between energy supply and the environment is one of the critical issues of our time, and geothermal energy, often touted as plentiful and environmentally benign, has received a measure of attention as one possible answer to the problem. Some environmental issues, however, have been encountered during the development of the world's geothermal resources and these have had an impact on the speed of development. The environmental problems at each of the world's geothermal generating stations are discussed in this paper.The significant environmental impacts include conflicts in land use, air pollution, subsidence, water pollution, induced seismicity, blowouts, and noise, and every country has encountered some difficulty with one or more of these problems. Development plans have been slowed by environmental concerns in some countries. In the U.S.A., this problem has been the emission of hydrogen sulfide; in Japan, land use in national parks plus waste-water disposal; in El Salvador, waste-water disposal. Other environmental impacts which have not had an appreciable effect on development plans include: waste-water disposal and subsidence in New Zealand, land use and air pollution in Mexico. Italy has encountered no particular environmental barriers yet, but this may be a function of minimal monitoring.Collectively, the environmental difficulties at the operating power stations around the world have been minor compared to the actual disasters that have befallen other processes of generating electricity. Even the potential environmental hazard of geothermal energy development is much less. It cannot be compared to a massive oil spill, a strip mine, or a radiation leak. Nevertheless, geothermal development faces an array of rules and regulations which, in view of world-wide environmental experience, need not be so strict. Regulation is particularly tight in the United States, a country which would, with appropriately relaxed controls, stimulate a global acceleration in development. Instead, the U.S. lies smothered in rules, and electrical geothermal development everywhere remains mired in a role of insignificant contribution.     

Future development of the electricity systems with distributed generation

Electrical power systems have been traditionally designed taking energy from high-voltage levels, and distributing it to lower voltage level networks. There are large generation units connected to transmission networks. But in the future there will be a large number of small generators connected to the distribution networks. Efficient integration of this distributed generation requires network innovations. A development of active distribution network management, from centralised to more distributed system management, is needed. Information, communication, and control infrastructures will be needed with increasing complexity of system management. Some innovative concepts such as microgrids and virtual utilities will be presented.     

改革电价发展绿电

火力发电占全国发电量的80%以上，为缓解电力短缺，目前全国在建电力项目约1.3亿千瓦，大多依然是火电项目，过度信赖煤炭这种化石燃料可能为将来埋下祸根。     

A strategic review of electricity systems models

Electricity systems models are software tools used to manage electricity demand and the electricity systems, to trade electricity and for generation expansion planning purposes. Various portfolios and scenarios are modelled in order to compare the effects of decision making in policy and on business development plans in electricity systems so as to best advise governments and industry on the least cost economic and environmental approach to electricity supply, while maintaining a secure supply of sufficient quality electricity. The modelling techniques developed to study vertically integrated state monopolies are now applied in liberalised markets where the issues and constraints are more complex. This paper reviews the changing role of electricity systems modelling in a strategic manner, focussing on the modelling response to key developments, the move away from monopoly towards liberalised market regimes and the increasing complexity brought about by policy targets for renewable energy and emissions. The paper provides an overview of electricity systems modelling techniques, discusses a number of key proprietary electricity systems models used in the USA and Europe and provides an information resource to the electricity analyst not currently readily available in the literature on the choice of model to investigate different aspects of the electricity system.     

制冷剂对全球环境的影响及其替代的选择

论述了CFC类和HCFC类制冷剂对破坏大气臭氧层的影响和温室气体对全球气候变化的影响,探讨了如何正确协调《蒙特利尔议定书》与《京都议定书》的要求,着重分析了几种替代制冷剂的特性,阐述了在实际使用中如何进行替代制冷剂的选择。     

Present situation and future prospects of electricity generation in Aegean Archipelago islands

The Aegean Archipelago is a remote Hellenic area, including several hundreds of scattered islands of various sizes. In these islands more than 600,000 people are living mainly in small remote communities. The main economical activities of the islanders are apart from tourism, seafaring, fishery, agriculture and stock farming. One of the major problems of the area is the insufficient infrastructure, strongly related with the absence of an integrated and cost-effective electrification plan. In this context, the present work is concentrated on analyzing the present situation and demonstrating the future prospects of electricity generation in the Aegean Archipelago islands. For this purpose, one should first investigate the time evolution of the corresponding electricity generation parameters (i.e. annual electricity consumption, peak power demand, capacity factor, specific fuel consumption) for the last 30 years. Subsequently, the corresponding diesel and heavy-oil consumption along with the electricity production cost for every specific autonomous power station of the area are investigated. Special attention is paid in order to estimate the contribution of renewable energy sources (RES) in the energy balance of each island. Finally, an attempt is made to describe in brief the most realistic electricity production solutions available, including the operation of hybrid RES-based power plants in collaboration with appropriate energy storage facilities. Additionally, the idea of connecting the islands of the area with the mainland and interconnecting them is also taken into consideration.     

Changing Sunshine: Analyzing the dynamics of solar electricity policies in the global context

Although solar costs have been dropping in recent years, solar power is still more expensive than conventional and other renewable energy options, and in most applications solar power still needs continuing government policy support. However, the need to achieve multiple objectives and ensure sufficient political support for solar power makes it difficult for policy makers to design an optimal solar power policy. The dynamic and uncertain nature of the solar industry, combined with the constraints imposed by broader economic, political and social conditions further complicates the task of policy making. In this paper, we present a framework to critically analyze the objectives behind different country policies, how factors such as macro-economic conditions and development paradigms affect the policy outcomes and finally, how these outcomes affect the overall cost reduction of solar energy. We find that while the extent of cost reduction through creation of large demand remains to be seen, it is essential for governments to provide adequate support for leapfrog RD&D, and exploit real comparative advantages across countries for effective solar cost reduction. Policy makers need to optimally design their policies by balancing national objectives and paying capacity with the global objective of solar power cost reduction in order to realize its full potential.     

地区电网DMS支撑环境的研究

介绍了一个适用于地区电网配电管理系统 ( DMS)的支撑环境 ,该支撑环境采用了面向对象的设计思想和分布式的体系结构 ,具有可视化、智能化的特点     

Methanol opportunities for electricity and hydrogen production in bioelectrochemical systems

An anodic syntrophic consortium (exoelectrogenic plus fermentative bacteria) able to use methanol as sole carbon source was developed for the first time in a bioelectrochemical system. In this frame, promising results were obtained in single chamber MFC, comparable to those obtained with readily biodegradable substrates. Regarding MEC operation, the presence of homoacetogenic bacteria led to electron recycling, avoiding net hydrogen production in single chamber MEC. In a double chamber MEC, satisfying results (in terms of coulombic efficiency and cathodic gas recovery) were obtained even though energy recovery still restrained the feasibility of the process. The approach used in this work with methanol opens a new range of possibilities for other complex substrates as electron donors for bioelectrosynthesis.