28-04-2011, 10:10 AM
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WhaT is Distributed Energy Resources (Distributed Generation)?
Distributed Generation (or DG)refers to small-scale(typically1KW-50MW)electric power generators that produce electricity at a site close to customers or that are tied to an electric distribution system
Centralised generation:
Currently, developing countries generate most of their electricity in large centralized facilities, such as fossil fuel(coal, gas powered) nuclear or hydropower plants
plants are built according to a number of economic, health & safety, logistical, environmental, geographical and geological factors.
usually transmit electricity long distances and can affect to the environment.
BLOCK DIAGRAMS
TECHNOLOGIES USED :
Efficient Clean fossil-Fuels Technologies
1.micro-turbines,
2.Fuel Cells
Environmental Friendly Renewable Energy Technologies
1.Biomass
2.Solar/Photovoltaic Array
3.Small Wind Turbines
4.Hydro Turbines
FUEL CELLS
21st Century -likely to be the century of the fuel cell, and as a result fuel cells will revolutionize the way to currently generate electric power offering the prospect of supplying the world with clean, efficient, sustainable electrical energy because they use hydrogen as a fuel.
A fuel cell is defined as an electrical cell, which unlike other storage devices can be continuously fed with a fuel in order that the electrical power can be maintained.
The fuel cells convert hydrogen or hydrogen-containing fuels, directly into electrical energy, heat, and water through the electrochemical reaction of hydrogen and oxygen.
FUEL CELLS(Electrochemical Devices
FC is a device used to generate electric power and provide thermal
energy from chemical energy through electrochemical processes.
Acts like a battery supplying electric energy as long as its fuels are continued to supply.
Unlike batteries, FC does not need to be charged for the consumed materials during the electrochemical processing as these materials are continuously supplied.
FC is a well-known technology from the early 1960s when they were used in the Modulated States Space Program and many automobile industry companies. Later in 1997, the US Dept of Energy testedgasoline fuel for FC to study its availability for generating electric power.
FC capacities vary from kW to MW for portable and stationary units.
Configuration of the fuel cell system
Advantages of fuel cells
Quite
Low Emissions
High Efficiency
High cost
limited field test experience,
low temperature waste heat may limit cogeneration potential
PHOTOVOLTAIC ( PV )
Solar PV:-
most versatile renewable technology with varied applications.
Consturction:
basic unit of PV is a cell may be round or square in shape, made of doped silicon crystal.
Cells are connected to form a module or panel and modules are connected to form an array to generate the required power.
BLOCK DIAGRAM
WIND – TURBINES(WT)
Construction:
WT is not a new form it has been used for decades.
consists of a rotor, turbine blades, generator, drive or coupling device, shaft, and the nacelle (the turbine head) that contains the gearbox and the generator drive.
Modern WT can provide clean electricity as individuals or as wind farms.
OPERATION:
wind rotates the windmill-like blades, which in turn rotate their attached shaft.
shaft operates a pump or a generator that produces electricity.
The energy characteristics of larger wind turbine farms are closer to the centralized energy sources.
Small WT(working as modules) can be combined with PV and battery systems to serve area of 25–100kW.
ADVANTAGES
Low cost energy
No harmful emissions
Minimal land use
No fuel required
Variable power output due to the fluctuation in wind speed
Location limited
Bird mortality
ISLANDING
Islanding is the situation in which a distribution system becomes electrically isolated from the remainder of the power system, yet continues to be energized by DG connected to it, known as micro-grid.
Current practice is that almost all utilities require DG to be disconnected from the grid as soon as possible in case of islanding.
Islanding can be intentional or non intentional.
CHALLENGES:
no uniform national interconnection standards addressing safety, power quality and reliability for small distributed generation systems.
Interconnection may involve communication with several different organizations
The environmental regulations and permit process that have been developed for larger distributed generation projects make some DG projects uneconomical.
CONCLUSION
The promise of a future world dominated by rapid population growth and unparalleled energy demand presents many challenges to the global energy industry and indeed society as a whole. Increased electrification will be central to future world energy development. The distributed generation concept offers many advantages over established electricity generation infrastructures and will play a major role in the provision of world energy needs.