ЭКОЛОГИЧЕСКИЕ АСПЕКТЫ ИСПОЛЬЗОВАНИЯ АЛЬТЕРНАТИВНОЙ ЭНЕРГЕТИКИ, ЭКОЛОГИЯ МЕГАПОЛИСОВ, МАЛЫХ ГОРОДОВ, ДЕРЕВЕНЬ
ECOLOGICAL ASPECTS OF ALTERNATIVE ENERGY AND ECOLOGY OF MEGAPOLISES, CITIES AND VILLAGES
THE GLOBAL STATUS OF RENEWABLE ENERGY TECHNOLOGIES
K. J. Touryan
NREL
1617 Cole Blvd. MS 1635 Golden, CO 80401 Phone: 303-275-3009; fax: 303-275-3040; e-mail: ken_touryan@nrel.gov
Kennel J. Touryan, Ph. D., Manager, NIS Country Programs, Chief Technology Analyst
As part of the NREL Technology Transfer Team, Ken Touryan manages a variety of technology transfer activities, including NREL's Initiatives for Proliferation Program (IPP). Ken created the IPP program at NREL and has managed this multi-laboratory effort for the past nine years. The IPP program was initiated in 1994 to control and reduce the global threat represented by nuclear, chemical and biological weapons. IPP aims to identify and develop non-military applications for defense technologies and create high-tech commercial employment opportunities for weapons scientists and engineers. Under Ken's leadership, this program has created many successful partnerships between U.S. firms and former weapons scientists, provided synergies with NREL's applied research, and established a unique link between NREL's technical expertise and global security.
The inability of fossil fuels to keep up with the rapidly increasing demand for energy, especially in developing countries, is making imperative the search for alternate energy sources. Renewable technologies, including the use of hydrogen, offer new hope of meeting this increasing demand in significant ways. To this end, we review the status of several of these renewable energy technologies and their readiness to compete in the energy market, in the immediate future.
Introduction
As we enter the 21st century, all indications are that the world will run out of fossil fuels much sooner than past predictions. In fact, most forecast point to the time frame of 2010—2015 when oil production world wide, will peak, and 2020, when natural gas production will peak (Fig. 1). Coal may last until the end of the century, but subject to stringent environmental controls. In fact, there are five global trends that are converging, to make the introduction of new energy technologies, such as renewable energy and hydrogen, viable options to replace a significant portion of the increasing global energy demand. These five are: 1) Increasing environmental awareness specially as it pertains to the emission of green house gases; 2) The availability of new technology options, such as energy from wind, solar, biomass and hydrogen from renewable resources; 3) World energy demand growth, specially in Asia;
4) Increased security risks, with terrorists attacking power oil/gas pipelines, refineries and large power plants, plus uncertainties in the availability of fossil fuel resources caused by political unrest,
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Fig. 1. Source: John F. Bookout (President of Shell USA), "Two Centuries of Fossil Fuel Energy". International Geological Congress, Washington DC; July 10,1985. Episodes, Vol. 12. P. 257-262 (1989).
Статья поступила в редакцию 11.11.2005. The article has entered in publishing office 11.11.2005.
and 5) Increasing business interest in the energy field, with the potential profitable markets for introducing new sources of energy.
It is important to note, that renewable energy RE technologies (RET), including the proposed hydrogen economy, are well poised to respond to the above five challenges. RETs are environmentally far more benign than fossil fuels. Unlike oil and gas resources, they are evenly distributed throughout the world and are available to every country, and they are easier to protect against terrorism, because by their very nature they operate as distributed systems.
Renewable energy resources include: wind, solar, biomass, geothermal, hydro and ocean energy. Because of lack of space, in this paper we will focus on wind, solar and biomass, and only touch upon geothermal, hydro and marine sources of energy. We will also cover briefly, the use of hydrogen as the fuel that can meet future global transportation needs.
Resource Assessment
In order to estimate the viability of using a given renewable energy technology, one needs to gather data on the availability of the resource itself, whether it be wind, solar, biomass, etc., In fact, there are certain minima below which the new technology will not be competitive with fossil fuel sources. For example, at today's cost of electricity, at 4—10 cents a kWhr, wind will become economical only if it is available at 300,000 kWhrs/ year, or more (Fig. 2).
Same goes for the solar insolation. One needs over 2000 solar hours/year, before one can use solar hot water or photovoltaic (PV) power to replace fossil fuels. For each location, careful measurements must be taken, over a period of least a year, plus using meteorological data, covering a period of 10 years, before consideration is given for the use of wind turbines or solar PV panels. At the National Renewable Energy Laboratory (NREL), computerized mapping techniques exist, based on GIS and meteorological data that can be used to obtain global, mesoscale or microscale distribution of winds and/or solar insolation for any country in the world. In addition, NREL has developed software (VIPOR, HOMER and Hybrid 2) that can evaluate the economic feasibility for the use of any renewable technology, in any location, based on input data that includes the local energy resource, the fossil fuel price (or cost of electricity), the availability of a power grid, etc.
Wind Energy
Of all the RETs, wind energy is the most competitive in the present market and has made the widest penetration, to date; 40,000 MW world wide. In 2003, wind provided 15 billion kWhrs of energy world wide at an average cost of 5—6 cents/Whr. Germany is the lead country in the use of wind
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energy, followed by Denmark, Spain, the UK and the USA. The new trend for installing wind farms is the use of very large machines, 1-5 MW per unit, and moving the wind farms, off shore, to conserve space. In addition to larger machines, future innovations include: advanced blade materials and manufacturing, low speed direct drive generators, custom power electronics, feedback control of drive train and rotor loads and more flexible structurally. The target O&M cost for the next generation turbines is 3 cents/kWhr. As far as their environmental impact is concerned, the only issues are the aesthetics of large wind farms near populated areas and bird-kills, especially along bird migration paths.
Solar Thermal Energy
Along with wind energy, the use of solar thermal power for hot water is commercially available and in wide use in temperate climates, such as Israel and Cyprus. Not so for space heating; too costly for Northern climates. The main emphasis these days is on electric power generation using solar energy to heat a working fluid, convert it to steam and run engines or turbines. Three types of concentrating solar power technologies are under development: single-axis tracking parabolic trough systems, dual tracking dishes, or flat plates with Fresno lenses, and power towers (Fig. 3). Trough technology is the most advanced of the above three systems. It has 354 MW of commercial power generation in operation in South West California (Kramer Junction) It operates in a hybrid mode with natural gas, using organic Rankine cycle for power generation. Plans are to install 1000 MW systems by 2010, reducing O&M costs from 12 cents/kWhr to 4 cents/kWhr.
The dual tracking dish systems employ Bray-ton or Sterling cycle engines at their focus, and come in 25-30 kW units. The receiver and generator are integrated into a single assembly that is mounted at the mirrored dish. To reduce the cost of reflectors, glass is replaced by thin reflective polymer membranes stretched across each receiver section, with another membrane stretched on the back, creating a partial vacuum that in turn forms spherical shapes that are ideal for the dish concentrator. Even the Fresno lenses are made of poly-
acrylic material rather than glass, providing up tot 300 sun concentration. Dish concentrator systems are well suited as distributed power generators. The third dual tracking system is the power tower. The Solar Two, 10 MW systems, with 400 heliostats is operational at Dagett California, using molten salt for storage, which is then used to boil water and run a steam turbine. As with the parabolic trough system, power towers can operate in a hybrid mode as solar/fossil plants.
Solar Photovoltaic Energy
Direct conversion of solar energy to electricity, with no moving parts, and no intermediate steps, makes solar photovoltaic technology (PV) the most desirable energy conversion system. Mono-crystalline or poly-crystalline silicon (c-Si) cells represent over 90 % of commercially available PV systems. World PV Cell/module production exceeded 1 GW in 2004 and is growing at the rate of 30-40 % per year. Shortages in the availability of solar grade silicon has led to the development of thin film solar cells such as amorphous Si (a-Si), cadmium telluride cells (CdTe), and gallium indium di-selenide cells (CIGS), Also a new effort is underway for using thin film crystalline Si cells (<100 microns). Of these thin film cells, a-Si cells have the widest commercial application at present. The third type of PV cells is the gallium indium phosphide/GaAS, multij unction
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