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Technologies that Empower
Distributed Generation for Rural
Electrification:
Options for Myanmar
Yangon, Myanmar
Dr. Chris Greacen
September 5, 2013
Outline
• Mini-grids and conventional grid extension
– What happens when the grid arrives?
• Low cost pre-electrification (solar microgrid)
• Lowering distribution cost for low-density
rural electrification (SWER)
• Technologies to help spread out peak
loads on mini-grids (MCBs, Gridshare)
2
Electricity for whom?
3
Extending the grid and rural mini-grids
Customers
National
Grid
Large Plants
Customers
MiniGrid
Small Power
Producer
4
Electrification:
26%
5
Electrification:
50%
6
Electrification:
75%
7
Rice husk gasifier
Myanmar – Kayuklot Township
electricity to 500 households
What to do when the “big grid”
expands to reach the “little grid”?
• Option 1: formerly off-grid
generators connect to the
grid to sell electricity
– DC sources (e.g. solar)
• Grid-connect inverter required
– AC generators (e.g. hydro)
• Digital relay required
Chris Greacen, Richard Engel, and Thomas Quetchenbach, A Guidebook on Grid Interconnection and Island Operation of MiniGrid Power Systems Up to 200 kW (Schatz Energy Research Center and Palang Thai, LBNL--‐6224E).
What to do when the “big grid”
expands to reach the “little grid”?
• Option 2: purchase
electricity from national
grid for distribution on
mini-grid.
– Mini-grid must be built to
acceptable standards
What to do when the “big grid”
expands to reach the “little grid”?
• Option 1 + 2: both!
•Mae Kam Pong, Chiang Mai, Thailand
•Built by government & community
•40 kW
•Used to be off-grid;
•Making arrangements to sell electricity to grid
4 MW hydro - Tanzania
electricity to 4000 households in >15 villages & sells to the grid
Affordable pre-electrification
• Pre-electrification is:
– safe lighting
– cell phone charging
– small appliances
• Pre-electrification is generally not:
– Agricultural milling
– Power tools (electric saws, etc.)
– Water pumping
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Pre-electrification solar micro-grid
Devergy in Tanzania
www.devergy.com
Devergy
•Every household that wants
electricity gets an electronic pre-paid
meter
•Electricity paid with cell phone
•About $7 per month
Devergy pre-electrification technology
•Every 5-6 households served
by an “Enbox”
•60 watts of PV
•24 volt, 20 Amp-hr battery
•ZigBee wireless
electronics, networked to
metered households and
other Enboxes
•The micro-grid sends update
on status of all meters, voltage
& current of all Enboxes via
cell-phone (GPRS) carrier to
internet every 5 minutes.
Single Wire Earth Return (SWER)
• Single wire system using
ground as return
conductor
• It is used for low cost
rural electrification
Source: Tulloch & Davies, 2006. SWER: New Zealand & Australian Experience.
http://siteresources.worldbank.org/EXTENERGY/Resources/336805-1137702984816/21357341142446048455/SWERIan.ppt
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How it all started
• Lloyd Mandeno invented SWER in
New Zealand in 1925.
• Seen in 1940’s as preferred
solution for remote, sparsely
populated areas.
• 200,000 km of SWER now in NZ
and Australia.
• Successfully used in NZ, Australia,
Canada, India, Brazil, Africa and
Asia for sparsely populated areas
Source: Tulloch & Davies, 2006. SWER: New Zealand & Australian Experience.
http://siteresources.worldbank.org/EXTENERGY/Resources/336805-1137702984816/21357341142446048455/SWERIan.ppt
How does it work?
Resistance R1 = R (conductor) + R (earth return path)
Allow 0.05 ohms/km at 50 Hz for earth return path.
Source: Armstrong. Single Wire Earth Return www.ruralpower.org/oldsite/images/rubberdocs/019_SWER.ppt
Advantages of SWER
• Cost Reduction
–
–
–
–
One conductor, less pole top equipment
Long, hilltop to hilltop spans
Fewer switching and protection devices
In Australia & NZ:
• Capital cost 50% less than 2-wire, single-phase
• 70% less than 3-wire, 3 phase
• Design Simplicity
• Reduced maintenance costs
• Estimated 50% maintenance cost saving
• Reduced bushfire hazard – avoid conductor
clashing
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Source: Armstrong 2002. Single Wire Earth Return
Limitations of SWER
• Restricted load capacity
• Requirement for reliable low resistance
earthing at isolating and distribution
transformers
• Possible interference with metallic
communications systems
• Higher losses due to charging currents
Source: Tulloch & Davies, 2006. SWER: New Zealand & Australian Experience.
http://siteresources.worldbank.org/EXTENERGY/Resources/336805-1137702984816/21357341142446048455/SWERIan.ppt
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Technologies to help reduce
peak loads on micro-hydro
mini-grids
Voltage drops
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Miniature Circuit Breakers (MCBs)
or PTCs to limit peak loads
600
kWh meter
500
watts
400
300
200
100
S1
11pm
9pm
7pm
5pm
3pm
1pm
11am
9am
7am
5am
0
Mini-circuit breaker can encourage peak load reduction
Mini-circuit
breaker
CASE STUDY - LOAD MANAGEMENT
• A 35 kW micro-hydro plant
in Rukubji, Bhutan
• Lighting, TVs, rice cookers
and water boilers are the
common loads
Voltage drops
As on many mini-grids,
when load exceeded
generation capacity,
brownouts occurred
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Source: Schatz Energy Research Center
GRIDSHARE LOAD MANAGEMENT TECHNOLOGY
• Humboldt State University team, in
partnership with Bhutan Power
Corporation and Bhutan DOE
developed the GridShare.
•
The GridShare, installed in each
household, limits household load
only during a brownout or voltage
drop.
•
The device is intelligent enough to
detect rice cookers, and keeps
them turned on for people to finish
cooking their rice.
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GRIDSHARE LOAD MANAGEMENT TECHNOLOGY
Electrical data indicated a reduction of over 90% in
severe brownouts
Reduced spoiled rice
and
Residents stated:
“the grid is more predictable”
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Conclusions
Technology
Application
Impact
Interconnection relays
mini-grid connect to
main-grid
Lowers risk to
developers of isolated
mini-grids
Solar pico-grid
Affordable preelectrification
deliver small amounts of
electricity, deploy quickly,
inexpensively
ZigBee & GPRS internet
connecctivity
monitoring of remote
mini-grids
Lowers repair costs by
catching problems early
on.
SWER
Low cost grid extension
Reduced hardware cost
MCBs and GridShare
Management of peak
loads
Fewer brownouts
Chris Greacen
Palang Thai
[email protected]
www.palangthai.org