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

117

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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