Title: Renewable Energy: An UPS for People
Author: Ilyas Ahmed, Sr.Lecturer, Department of Electrical Engineering
College: Ajay Binay Institute of Technology, Cuttak
Energy continues to be an essential key to worldwide development approaching higher standard of life. The main source of energy in the past and present industrial nations has been fossil energy and in the next century these countries will need to depend more on coal, nuclear and renewable energy. Generation of energy from fossil fuels is always associated with loss of thermal energy as well as undesired by-products and polluting materials. Twenty years ago nuclear energy was widely believed to be energy of the future but today because of some unsolved problems in this field there is a large question mark on the whole nuclear industry. Overcoming these energy problems requires developing new energy systems which are environmental friendlier. In this paper author presents latest development and the results obtained from a project of integrated renewable energy storage (IREES) system. IREES system, which is total renewable energy based electricity supply system, finds so many applications as it can be used as a large scale power supplv being connected to national grid as well as small scale power supply for remote areas. Finding and results arising from this research project will be of practical value for both power suppliers and people as energy as this system not only conserves energy but also helps preserving the environment.
An environmental impact of using energy on society has raised concern for many people and organizations. Emissions produced by current generating systems significantly contribute to global warming which is currently seen as the most important environmental issue now facing us. It is obvious that rich countries arc more responsible for pollution from generating and use of energy. IREES system offers advantages of combining different type of sources of energy to produce power from mostly available and environmental safer one. Uninterrupted power generation, drastically reduction of undesired emissions per kWh per person. Storing energy at low demand periods, energy security etc.
FOSSIL ENERGY AND ENVIRONMENTAL PROBLEMS
The total amount of energy generated in power stations in 1989 was equivalent to more than 9000 million tonnes of oil. Every day the world power stations use more than four million tonnes of coal, six million barrels of oil and fifty million cubic meters of natural gas. The total energy produced is more than 200 billion mega joules. To produce this amount of energy every day nearly 60000 million kilogram carbon dioxide is poured into the atmosphere. It is obvious that fossil fuels we use will one day run out 90% of today’s world energy is from non-renewable source namely Fossil fuel and uranium and the rest 10% conics from renewable sources. According to high coal scenario 60% of world energy by the year 2100 is from coal and 40% from renewable and nuclear. Coal is main fossil fuel resource and is world’s most plentiful fuel. When coal or any fossil fuel is burnt for electricity generation or any other purpose gases are released into the atmosphere. Large amount of carbon dioxide are released when coal is burnt .This contribute global warming resulting from green house effect. Not only does coal produce up to 50% more carbon dioxide when burnt than other fossil fuels. Electricity produced from coal releases up to four times as much as carbon dioxide as docs the direct use of other fossil fuels. Nuclear Energy and the Future of Nuclear Industry Nuclear energy) was hailed as the solution to the world’s energy problem in 1970’s. But today after nuclear accidents in Three Mile Island in 1979 and in Chernonyl in I086 and also due to unsolved nuclear waste disposal problems this technology is considered as the most dangerous and unfitting way to produce energy. According to International Atomic Energy Organization (IAEO) by 1989 nuclear energy account for 16% of the world electricity, Every day world’s nuclear power stations USC more than 30 tonnes of uranium. So far 426 nuclear reactors have been connected to the global electric grid with a generating capacity of 31827 Mega Watts of energy (MWe) . 96 Reactors arc under construction which when completed will bring the total nuclear generating capacity to 397178 MWe. It is true that nuclear accidents are rare but they may occur and when they do happen the result can be very serious. Disposing of radioactive waste permanently is a difficult problem. The danger from thc nuclear waste can last for thousands of year. One method of disposal has been to dump the waste in sealed containers far out to sea. There is suggestion to bury the nuclear waste in the ground. Some organizations haw expressed concerns about what might happen if waste ever leaked from those sites or in the sea. In Sweden a referendum has called for termination of nuclear power generation by 2010. In Germany the Kalkar council plans to redesignate the site of Kalkar fast breeder nuclear power plant, the world’s largest fast breeder reactor, as an agricultural field. The owner of the site will be forced to dismantle the plant and turn the area back to a green field. (MPSoct1993).
Renewable source of energy is a potential source of energy mainly beyond the year 2000 ( but is not likely to be a total answer to the world’s energy requirement). All forms of renewable energy are regarded as CO2 neutral. The main renewable energies are: Solar, Wind, Hydro, Tidal, Wave, Land fill, Sewage and other ‘bio’ gas, Incineration of waste (municip1, industrial, hospital etc.), Geothermal and Bio fuel(Wood, Straw). Some of these sources such as solar and wind are classified as intermittent renewable sources and some others like hydro and biomass are classified as non-intermittent sources. Environmental impacts of renewable energy are much smaller than those of fossil for example has a vast high quality, solar energy resource which has the potential to be used to meet country’s entire electricity requirements. Only 0.1% of the Australia’s land area would be required to generate Australia’s electricity needs for the foreseeable future. The present cost of electricity produced b5- solar components of the power plants is estimated to be sonic 21 cents /kWh. In the USA this cost recently has been recorded as some 11USCentikWh. In a report prepared for the US Department of Energy, solar – thermal base electricity costs have been projected to fall to around 8 – 10 cents / kWh by 2000 and some 5 cents / kWh by year 2030.
INTEGRATED RENEWABLE ENERGY AND ENERGY STORAGE (IREES)SYSTEM
A. SMALL SCALE IREES FOR RAPS
For many years, people who are remote from National Grid have diesel generators to supply electricity for their use. These generators are auto-start/auto-stop and their size are at least four times larger than the average load requirement and they have to run for a long period of time under light load which causes relatively high maintenance and fuel costs. It is not possible to include renewable sources in such systems. If battery is added to this system, the battery is used during periods of light load and generator is used during periods of heavy loads. Using battery has this advantage that diesel generator running time is reduced and power is available 24 hours a day. Another advantage of this system is that renewable sources of energy namely solar, wind etc. can be easily added to this system. PLC controls the power flow between the inverter. Generator and the battery bank to optimize the operation time and the loading of the diesel as well as to maximize battery life.
B. LARGE SCALE IREES
Most of renewable energy sources are of an intermittent nature such as solar energy and wind energy, therefore it would be appropriate to use intermittent sources of energy in conjunction with non-intermittent sources such as hydro and biomass. If this power supply mix is used to supply an interconnected grid, more effective use could be made of the most prospective renewable energy.
Energy Storage System:
Due to cyclical human life, utility loads appear to be cyclical too. During daytime when most factories are in operation, the electricity demand is very high. When most people are sleeping from midnight to daybreak, the electric load is very low usually only half of the peak load amount. To meet this large gap between peak load and light load, utilities must idle many generation plants during light load period while operate all generation plants during peak load period no matter how expensive they are. This low utilization factor of generation plants and uneconomical operation have
sparked utilities to invest in energy storage devices such as pumped storage plants, compressed air energy storage plants, battery energy storage system (BES) and superconducting magnetic energy storage system (SMES) etc. Among these, pumped storage is already commercialized and is the most widely used device. However, it suffers the limit of available sites and will be saturated in the future. Other energy storage devices are still under research to reduce the cost. Battery energy storage is one of the most promising devices that may succeed pumped storage as the next generation storage device.
DIFFICULTIES IN RELATION TO INTEGRATION OF WIND TURBINE IN ENERGY SUPPLY SYSTEM
The integration of wind turbine into electricity network causes negative effects on quality of supply and reliability of system. The effects of wind turbine on the dynamic behavior of a network includes worsening the voltage and frequency quality, increasing demand on control devices of wind turbine and increasing load on network control. The power fluctuations are the results of changes in wind speed in different times. In order to reduce the negative effects of integrating of wind turbine into a network there are conventional actions such as using rotation-variable generating system, increasing the short circuit power at the junction of wind turbine and the network. Power fluctuations can be compensated by integration of energy storage devices located next to the junction of wind turbine and network. Storage devices are used to improve the quality of supply and to guarantee the system reliability. While the battery storage systems are used as long term storage. SMES systems are more appropriate to be used as short term one.
Our future energy needs will be supplied by a combination of many different sources, ranging from small wind and water wheels that provide power for a single home to central power stations that provide power in very large scale fed into the national grid Computer control systems will integrate the performance or al the systems 10 make sure that as Much as possible power comes from environmentally friendlier sources. As alternative sources become more vividly available. Small scale systems meeting local needs may start lo replace current large scale central power stations. The IREES system offers advantages such as combining different type of sources of energy to produce from mostly available and environmentally safer one. Uninterrupted energy renewable based electricity supply. . Drastically reduction of undesired emissions per kWh storing energy at low demand periods. Energy security and etc. IREES system finds so many applications as it can be used 3s a large scale power supply king connected to national grid as well as small scale power supply for remote areas. Finding and results arising from this research project will be of practical value for both power suppliers and people as energy users as this system not only conserves energy but also preserves environment.
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