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
14
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
18
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
21
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
22
Technologies to help reduce
peak loads on micro-hydro
mini-grids
Voltage drops
23
Miniature Circuit Breakers (MCBs)
or PTCs to limit peak loads
600
kWh meter
500
w atts
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
25
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.
26
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”
27
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
chris@palangthai.org
www.palangthai.org