Azure Micro-Grid Village Power Systems

Prepared By:

Christopher Freitas Chris Greacen

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 grid Includes energy storage (large batteries) Typically includes back-up generator for poor weather

periods

Micro-Grid Power Systems can use different configurations:

• Can range from being more like a “grid-tied” or an “off-grid” type 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 interconnected together

• No real agreed upon definition of the term “Micro-grid”

Some Micro-Grids use solar power to reduce a generator’s fuel consumption:

• Generators still operate 24 hours a day

• Solar is typically limited to about 25% of the generator’s

rating (higher is possible with more sophisticated controls)

• Inverters tend to be simpler, smaller and less expensive

• Examples:

– Greek Islands

– Alaskan villages with wind turbines

Other Micro-Grids use solar to power all of the loads:

• Solar is used to power loads during the daytime and to

recharge 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 enough to power all loads – even starting multiple loads at same time

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 air

conditioning or industrial equipment

• Example:

– Hospitals in Haiti (USAID / Solar Electric Light Fund)

Micro-Grid System Configurations and Terminology:

• DC Coupled Systems

• AC Coupled Systems

• Combined AC and DC Coupled Systems

DC Coupled Micro-Grids:

• Solar power sources are interconnected together as DC and power is only converted into AC power only when loads consume it

• Traditional configuration for off-grid systems

• High power DC wiring and safety equipment can be difficult to source and expensive

• Power electronics tend to be smaller and cheaper

• Higher efficiency for loads operating at night

DC Coupled Micro-Grid:

Solar Array

Controller

Batteries

Controller Controller

Solar Array Solar Array

AC Distribution and Loads

Inverter/Charger Generator

AC Coupled Micro-Grids:

• Solar power sources are immediately converted into AC and are 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 source and 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

AC Coupled Micro-Grid:

Solar Array

Grid-Tie Inverter

AC Distribution System and Loads

Solar Array Solar Array

Batteries

Inverter/Charger Generator

Grid-Tie Inverter Grid-Tie Inverter

AC and DC Coupled Micro-Grids:

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

• Highest efficiency for both day and night loads

• Complex design

• Can be difficult to coordinate with growth in loads

AC and DC Coupled Micro-Grid:

Solar Array

Grid-Tie Inverter

AC Distribution System and Loads

Solar Array Solar Array

Batteries

Inverter/Charger Generator

Grid-Tie Inverter Controller

Examples of Micro-grids

• Partner in Health Hospitals (Haiti) • Beaconhouse School Campuses (Pakistan) • Alcatraz Island (San Francisco) • MW Scale PV Hybrid Systems (Malaysia)

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

Partners-In-Health (Haiti)

Partners-In-Health (Haiti)

• New university teaching hospital in Mirebalis, Haiti

• Located on good power quality power line direct from main hydro 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.

Partners-In-Health (Haiti)

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

Beaconhouse Schools (Pakistan)

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)

Alcatraz Island (San Francisco, USA)

Alcatraz Island (San Francisco, USA)

MW Scale PV Hybrid Systems (Malaysia)

• 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)

MW Scale PV Hybrid Systems (Malaysia)

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

MW Scale PV Hybrid Systems (Malaysia)

MW Scale PV Hybrid Systems (Malaysia)

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

MW Scale PV Hybrid Systems (Malaysia)

MW Scale PV Hybrid Systems (Malaysia)

MW Scale PV Hybrid Systems (Malaysia)

MW Scale PV Hybrid Systems (Malaysia)

Other topics

• Metering • Funding • PV mounting / land issues • Maintenance • Social issues