Distributed Generation
Mohammad Amin LatifiBureau of Privatization
Ministry of Energy
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US electric industry as an example
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Distributed Energy SystemsCentral Power Plants
Microturbine
Fuel Cell
Photovoltaic Array
Wind Turbine
Combustion GasTurbines
Future Trends of Electric Utility Industry
Energy StorageDevices
DistributionSubstation
Energy storage devices
Micro-turbinesGas turbines
Central Power Station
Transmission line Smart controller
Communication
Regional DispatchEnergy Value Information
Electric Power
Monitoring &Control Lines
Town Building HospitalFactoryRemote location
Stand-alone
Distribution line
Operating System For DG
Source: Distributed Utility Associates
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DefinitionDistributed Generation (DG) is the
implementation of various power generating resources, near the site of need, either for reducing reliance on, or for feeding power directly into the grid. DG may also be used to increase transmission and distribution system reliability.
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Gas technologies Combustion gas turbines
Micro-turbines
Fuel cells
Renewable Energy Technologies Biomass power
Small wind turbines
Photovoltaic Arrays
Technologies for DG
Technologies for Distributed Energy Systems (DG)
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Stand-alone
Standby
Grid-interconnected
Peak shaving
Applications for DG
Applications of DG
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Environmental-friendly and modular electric generation
Increased reliability
Fuel flexibility
Uninterruptible service
Cost savings
On-site generation
Standby Generation
Benefits of DG
Benefits of DG
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Value of DG
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Grid losses Vs. DG penetration level
Barriers of DG
Technical Barriers
Protective equipment
Safety measures
Reliability and power-quality concerns
Business-Practices Barriers
Contractual and procedural requirements for interconnection
Procedures for approving interconnection, application and interconnection fees,
Insurance requirements
Operational requirements
Regulatory Barriers
Tariff structures applicable to customers
Net metering
Environmental permitting
Barriers
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Power Electronics Technologies
Advanced Power Converter Design Technique
High-speed/high-power/low-losses power switches
New control techniques
Digital signal processors with high performance
New communications in the form of the Internet
Planning and valuation tools
Value to grid
Capacity needs assessment
What supports Technologies of DG?
What supports Technologies of DG?
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TechnologyCombustion Gas Turbine
Micro-turbine Fuel Cell Wind TurbinePhotovoltaic
Array
Size 0.5 – 30+MW 25 – 500 kW 1 kW – 10 MW 0.3 kW – +5 MW 0.3 kW -2 MW
Installed Cost ($/kW)
400 – 1,200 1,200 – 1,700 1,000 – 5,000 1,000 - 5,000 6,000 – 10,000
O&M Cost
($/kWh)0.003 – 0.008 0.005 – 0.016 0.0019 – 0.0153 0.005 0.001-0.004
Elec. Efficiency
20 - 45% 20 – 30% 30 – 60%
20 – 40% 5 – 15%Overall
Efficiency80 – 90% 80 – 85% 80 – 90%
Fuel Typenatural gas,
biogas, propane
natural gas, hydrogen, biogas,
propane, diesel
hydrogen, natural gas, propane
wind sunlight
Comparison of Several Technologies
Source: Distributed Energy Resources and Resource Dynamics Corporation
Combustion Gas Turbines (1)
Combustor
PowerConverter
Compressor
air
fuelPower Turbine
Generator
HRSG(Heat Recovery
Steam Generator) Feed water
Process steam
Fig. 1 Block diagram of Combustion Gas Turbine System.
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Features
Very mature technology Size: 0.5 – 30+ MW Efficiency: electricity (20 – 45%), cogeneration (80 – 90%) Installed cost ($/kW): 400 – 1,200 O&M cost ($/kWh): 0.003 – 0.008 Fuel: natural gas, biogas, propane Emission: approximately 150 – 300 ppm NOx (uncontrolled)
below approximately 6 ppm NOx (controlled) Cogeneration: yes (steam) Commercial Status: widely available Three main components: compressor, combustor, turbine Start-up time range: 2 – 5 minutes Natural gas pressure range: 160 – 610 psig Nominal operating temperature: 59 F
Combustion Gas Turbines (2)
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Advantages
High efficiency and low cost (particularly in large systems)
Readily available over a wide range of power output
Marketing and customer serving channels are well established
High power-to-weight ratio
Proven reliability and availability
Disadvantages
Reduced efficiencies at part load
Sensitivity to ambient conditions (temperature, altitude)
Small system cost and efficiency not as good as larger systems
Advantages & Disadvantages
Combustion Gas Turbines (3)
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Micro-turbines (1)
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Size: 25 – 500 kW
Efficiency: unrecuperated (15%), recuperated (20 – 30%), with heat recovery (up to 85%)
Installed cost ($/kW): 1,200 – 1,700
O&M cost ($/kWh): 0.005 – 0.016
Fuel: natural gas, hydrogen, biogas, propane, diesel
Emission: below approximately 9 - 50 ppm NOx
Cogeneration: yes (50 – 80C water)
Commercial Status: small volume production, commercial prototypes now
Rotating speed: 90,000 – 120,000
Maintenance interval: 5,000 – 8,000 hrs
Micro-turbines (2)
Features
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Advantages
Small number of moving parts
Compact size
Light-weight
Good efficiencies in cogeneration
Low emissions
Can utilize waste fuels
Long maintenance intervals
Disadvantages
Low fuel to electricity efficiencies
Micro-turbines (3)
Advantages & Disadvantages
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Fuel Cells (1)
Fig. 3 Block diagram of Fuel Cell System.
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Power Converter
Reformer
Fuel
H2O2
from air
Anode Catalyst
CathodeCatalyst
PolymerElectrolyte
+
H2OExhaust
AC Power
Electrochemical energy conversion: Hydrogen + Oxygen Electricity, Water, and Heat
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Size: 1 kW – 10 MW
Efficiency: electricity (30 – 60%), cogeneration (80 – 90%)
Installed cost ($/kW): 1,000 – 5,000
O&M cost ($/kWh): 0.0019 – 0.0153
Fuel: natural gas, hydrogen, propane, diesel
Emission: very low
Cogeneration: yes (hot water)
Commercial Status:
PAFC: commercially available
SOFC, MCFC, PEMFC: available in 2004
Fuel Cells (3)
Features (2)
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Wind Turbines (1)
Gear Box
Generator
Low-speedshaft High-speed
shaft
Wind
Power Converter
Nacelle
Fig. 4 Block diagram of Small Wind Turbine System.
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Size: small (0.3 - 50 kW), large (300 kW – +5 MW)
Efficiency: 20 – 40%
Installed cost ($/kW): large-scale (900 - 1,100), small-scale (2,500 - 5,000)
O&M cost ($/kWh): 0.005
Fuel: wind
Emission: zero
Other features: various types and sizes
Commercial Status: widely available
Wind speed:
Large turbine: 6 m/s (13 mph) at average sites
Small turbine: 4 m/s (9 mph) at average sites
Typical life of a wind turbine: 20 years
Wind Turbines (2)
Features
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Advantages
Power generated from wind farms can be inexpensive
Low cost energy
No harmful emissions
Minimal land use
: the land below each turbine can be used for animal grazing or farming
No fuel required
Disadvantages
Variable power output due to the fluctuation in wind speed
Location limited
Visual impact
: Aesthetic problem of placing them in higher population density areas
Bird mortality
Wind Turbines (3)
Advantages & Disadvantages
Photovoltaic Arrays (1)
Fig. 5 Block diagram of Photovoltaic Array System.
PV module
Array
Power Converter
Charge Controller
Batteries
DC power
AC power
Cell
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Size: 0.3 kW – 2 MW
Efficiency: 5 – 15%
Installed cost ($/kW): 6,000 – 10,000
O&M cost ($/kWh): 0.001
Fuel: sunlight
Emission: zero
Main components: batteries, battery chargers, a backup generator, a controller
Other features: no moving parts, quiet operation, little maintenance
Commercial Status: commercially deployed
An individual photovoltaic cell: 1 – 2 watts
Photovoltaic Arrays (4)
Features (3)
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Advantages
Work well for remote locations
Require very little maintenance
Environmentally friendly (No emissions)
Disadvantages
Local weather patterns and sun conditions directly affect the potential of photovoltaic system.
Some locations will not be able to use solar power
Photovoltaic Arrays (5)
Advantages & Disadvantages
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Energy Storage Technologies
Batteries
Capacitors
Flywheels
Superconducting Magnetic Energy Storage
Compressed air energy storage
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Different Configurations for DG
Fig. 6 Block diagram of a Power Converter connected in a stand-alone AC system.
1. A Power Converter connected in a Stand-alone AC System (1)
DistributedEnergySystem
Power Converter
VdcLoads
DSPController
Sensors
V, I, P, Q
3 AC240/480 V
50 or 60 Hz
Trans.
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Fig. 7 Simplified block diagram of Fig. 6.
I
VdcV E
Load 3 AC240/480 V
50 or 60 Hz
Different Configurations for DG
1. A Power Converter connected in a Stand-alone AC System (2)
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2. A Power Converter connected in Parallel with the Utility Mains (1)
Fig. 8 Block diagram of a Power Converter connected in parallel with the utility mains.
DistributedEnergySystem
Power Converter
Vdc
UtilityMains
3 AC240/480 V
50 or 60 Hz
DSPController
Sensors
V, I, P, Q
Trans.
Loads
Different Configurations for DG
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Fig. 9 Simplified block diagram of Fig. 8.
UtilityMains
I
VdcV E
3 AC240/480 V
50 or 60 Hz
2. A Power Converter connected in Parallel with the Utility Mains (2)
Different Configurations for DG
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Fig. 10 Block diagram of Paralleled-Connected Power Converters in a Stand-alone AC System.
3. Paralleled-Connected Power Converters in a Stand-alone AC System (1)
Power Converters
Micro-turbine
Fuel Cell
Loads
DSPController V, I, P, Q
Sensors
DSPController V, I, P, Q
Sensors
3 AC240/480 V
50 or 60 Hz
Trans.
Trans.
Different Configurations for DG
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Fig. 11 Simplified block diagram of Fig. 10.
Vdc1
I1
V EI2
Vdc2
VE
Loads
3. Paralleled-Connected Power Converters in a Stand-alone AC System (2)
Different Configurations for DG
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4. Paralleled-Connected Power Converters with a common DC grid in a Stand-alone AC System (1)
Fig. 12 Block diagram of Paralleled-Connected Power Converters with a common DC grid in a Stand-alone AC System.
Different Configurations for DG
Power Converters
Micro-turbine
Loads
DSPController
3 AC240/480 V
50 or 60 HzV, I, P, Q
Sensors
Sensors
V, I, P, QDC Grid
Fuel Cell
DSPController
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Fig. 13 Simplified block diagram of Fig. 12.
I1
Vdc
E
I2E
DC Grid
Loads
3 AC240/480 V
50 or 60 Hz
4. Paralleled-Connected Power Converters with a common DC grid in a Stand-alone AC System (2)
Different Configurations for DG
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Schematics of an average European electricity grid and connection levels for DG and RES
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DG Network Connection IssuesImpact on power system operation (changing
power flows, voltage profile, uncertainty in power production and etc)
Voltage regulation Power lossesPower quality (Sags, swells and etc )HarmonicsShort circuit levelsLocation and size of DGSafety and protection consideration
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Voltage regulation example
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Data needed to evaluate the DG impactSize rating of the proposed DRType of DR power converter (static or rotating
machine)Type of DR prime energy source (such photovoltaic,
wind or fuel cellOperating cyclesFault current contribution of DRHarmonics output content of DRDR power factor under various operating conditionsLocation of DR on the distribution systemsLocations and setting of voltage regulation equipment
on distribution systemLocations and settings of equipment for over current
protection on distribution system40
Main Barriers to DG
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RES Historical Development
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Distributed Generation (DG) Share of Total Generation Capacity (2007)
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What is CHP?
Integrated System Provides a Portion of the
Electrical Load Utilizes the Thermal
Energy Cooling Heating
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Overview of CHP TechnologiesTechnology Pros Cons
Fuel Cell - Very low emission
- Exempt from air and permitting in some areas
- Comes in a complete “ready to connect” package
- High initial investment- Limited number of commercially
available units
Gas Turbine -Excellent service contracts-Steam generation capabilities-Mature technology
- Requires air permit- The size and shape of generator
package is relatively large
Micro-turbine - Lower initial investment- High redundancy- Low maintenance cost- Relative small size and installation
flexibility
- Relatively new technology- Requires air permit- Synchronization problems
possible for large installations
Recip.
Engine
- Low initial investment- Mature technology- Relatively small size
- High maintenance costs- Low redundancy
Benefits of CHP High Efficiency, On-Site Generation Means
Improved ReliabilityLower Energy CostsLower Emissions (including CO2)Conserve Natural ResourcesSupport Grid Infrastructure
Fewer T&D ConstraintsDefer Costly Grid UpgradesPrice Stability
Facilitates Deployment of New Clean Energy Technologies
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Factors for CHP SuitabilityHigh Thermal Loads-(Cooling, Heating)
Cost of buying electric power from the grid versus to cost of natural gas (Spark Spread)
Long operating hours (> 3000 hr/yr)
Need for high power quality and reliability
Large size building/facility
Access to Fuels (Natural Gas or Byproducts)48
GeneratorsTwo Types of Generators
Induction• Requires Grid Power
Source to Operate • When Grid Goes
Down, CHP System Goes Down
• Less Complicated & Less Costly to Interconnect
• Preferred by Utilities
Synchronous• Self Excited (Does
Not Need Grid to Operate)
• CHP System can Continue to Operate thru Grid Outages
• More Complicated & Costly to Interconnect (Safety)
• Preferred by Customers
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Power Station Fuel(U.S. Fossil Mix)
186
lb/MMBtu
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CHP Fuel (Gas)
Lb/MMBtu
CO2 Emissions Reductions from CHP
39,000 Tons CO2 Saved/Year
Power Plant
6.0MWe
70,000 pphSteamBoiler117
Boiler Fuel (Gas)
Lb/MMBtu CO2 Emissions
56k Tons/yr CO2 Emissions
43k Tons/yr
…TOTAL ANNUAL CO2 EMISSIONS…95k Tons 56k Tons
CO2 Emissions
52k Tons/yr
Conventional Generation Combined Heat & Power:Taurus 65 Gas Turbine Efficiency: 31%
Steam
Efficiency: 80%
Efficiency: 82.5%
CHP and Energy Assurance
Combined Heat & Power (CHP) can Keep Critical Facilities Up & Operating During Outages
For Example, CHP can Restore Power and Avoid:
– Loss of lights & critical air handling
– Failure of water supply
– Closure of healthcare facilities
– Closure of key businesses
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ThanksAny Question?
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