Freitas and Greacen Micro Grid Presentation

8/12/2019 Freitas and Greacen Micro Grid Presentation

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Azure Micro-Grid

Village Power Systems

Prepared By:

Christopher FreitasChris Greacen


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Solar Electric Power Systems are

typically divided into two types:

Grid-Tied Systems

Utility connected

Typically has no energy storage (no batteries)Only is able to operate when the utility is operating

Off-Grid Systems

Remote / Independent of utility gridIncludes energy storage (large batteries)

Typically includes back-up generator for poor weatherperiods


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Micro-Grid Power Systems can use

different configurations:

Can range from being more like a grid-tied or an off-gridtype system or something in-between

Systems can power an entire village or just one facility

Can be made up of a single centralized system or can be

made up of several distributed systems interconnectedtogether

No real agreed upon definition of the term Micro-grid


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Some Micro-Grids use solar power to

reduce a generators fuel consumption:

Generators still operate 24 hours a day

Solar is typically limited to about 25% of the generatorsrating (higher is possible with more sophisticated controls)

Inverters tend to be simpler, smaller and less expensive

Examples:

Greek Islands

Alaskan villages with wind turbines


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Other Micro-Grids use solar to power all

of the loads:

Solar is used to power loads during the daytime and torecharge the battery energy storage system

Batteries are used to power loads at night

Back-up generators are used when weather is poor

Requires that the inverter & battery system be large enoughto power all loads even starting multiple loads at same time


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Micro-Grids can also be a combination of

grid-tie and off-grid configurations:

Some loads may only be powered from the generator

Other loads are powered from the solar and/or batteries all

the time

Often used when large loads are required such as airconditioning or industrial equipment

Example:

Hospitals in Haiti (USAID / Solar Electric Light Fund)


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Micro-Grid System Configurations and

Terminology:

DC Coupled Systems

AC Coupled Systems

Combined AC and DC Coupled Systems


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DC Coupled Micro-Grids:

Solar power sources are interconnected together as DC andpower is only converted into AC power only when loadsconsume it

Traditional configuration for off-grid systems

High power DC wiring and safety equipment can be difficultto source and expensive

Power electronics tend to be smaller and cheaper

Higher efficiency for loads operating at night


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DC Coupled Micro-Grid:

Solar Array

Controller

Batteries

Controller Controller

Solar Array Solar Array

AC Distribution and Loads

Inverter/ChargerGenerator


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AC Coupled Micro-Grids:

Solar power sources are immediately converted into AC andare then interconnected with the AC loads

Power is converted back into DC to recharge the batteries

High power AC wiring and equipment can be easier to sourceand less expensive

Power electronics tend to be larger and more expensive

Can allow for solar to be distributed around the village

May be easier to grid interconnect if utility becomes available

Higher efficiency for loads operating during the daytime


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AC Coupled Micro-Grid:

Solar Array

Grid-Tie Inverter

AC Distribution System and Loads


Batteries


Grid-Tie Inverter Grid-Tie Inverter


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AC and DC Coupled Micro-Grids:

Some of the solar power is immediately converted into ACand are then interconnected with the AC loads while othersolar power is kept as DC to recharge the battery to powerloads at night

Highest efficiency for both day and night loads

Complex design

Can be difficult to coordinate with growth in loads


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AC and DC Coupled Micro-Grid:

Solar Array

Grid-Tie Inverter

AC Distribution System and Loads


Batteries


Grid-Tie Inverter Controller


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Examples of Micro-grids

Partner in Health Hospitals (Haiti)

Beaconhouse School Campuses (Pakistan)

Alcatraz Island (San Francisco)

MW Scale PV Hybrid Systems (Malaysia)


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Partners-In-Health (Haiti)

Designed and Installed by Solar Electric Light Fund (SELF)

Remote locations with difficult fuel delivery no utility power

DC coupled configuration

Thirteen facilities installed - 15 to 60 kW of PV array

Power Electronics by OutBack Power Systems (USA)

Rooftop mounted for security


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New university teaching hospital in Mirebalis, Haiti

Located on good power quality power line direct from mainhydro generator

AC coupled configuration with generators

Not able to operate stand-alone without generator

400 kW PV array rooftop mounted

Power Electronics by Solectria Renewables (USA)

Utility cost $0.35 / kWh Three year payback expected.


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Beaconhouse Schools (Pakistan)

Private school system located throughout Pakistan

Designed 12 school systems and installed one pilot system

AC coupled configuration with utility and generator

10 kW PV array for pilot system others 100 to 250 kW

Power Electronics by SMA (Germany)

Rooftop mounted for pilot system

Combination of rooftop and ground shade structures planned


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Beaconhouse Schools (Pakistan)


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Alcatraz Island (San Francisco, USA)

No utility power generator only

AC coupled design with back-up generator

307 kW+ PV array

2 MWh battery

Eight 100 kW inverters

Power Electronics by Princeton Power Systems (USA)


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Village scale PV + Diesel power systems

Two installed and operating / two more under construction

AC and DC coupled configuration with back-up generator

Power Electronics by Leonics (Thailand)


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3.2 MW system - RPS Kemar, Gerik, Perak, Malaysia

PV array: 850 kW

Inverter: 850 kW

Battery: 4,800 kWh / 480Vdc

Diesel Generator: 1,600 kW


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4.2 MW system Tanjung Labian, Sabah, Malaysia

PV array: 1,262 kW

Inverter: 1,650 kW

Battery: 4,320 kWh / 480Vdc

Diesel Generator: 1,350 kW


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Other topics

Metering

Funding

PV mounting / land issues Maintenance

Social issues


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Documents

Freitas and Greacen Micro Grid Presentation