technologies that empower distributed generation for rural electrification: options for myanmar...
TRANSCRIPT
Technologies that Empower Distributed Generation for Rural
Electrification:
Options for Myanmar
Yangon, Myanmar
Dr. Chris GreacenSeptember 5, 2013
Outline
• Mini-grids and conventional grid extension– What happens when the grid arrives?
• Low cost pre-electrification (solar micro-grid)
• Lowering distribution cost for low-density rural electrification (SWER)
• Technologies to help spread out peak loads on mini-grids (MCBs, Gridshare)
2
Large Plants
Customers
Small Power Producer
Mini-Grid
Customers
Extending the grid and rural mini-grids
NationalGrid
4
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 Mini-Grid 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
• Mae Kam Pong, Chiang Mai, Thailand• Built by government & community• 40 kW• Used to be off-grid;• Making arrangements to sell electricity to
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
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
18Source: Tulloch & Davies, 2006. SWER: New Zealand & Australian Experience. http://siteresources.worldbank.org/EXTENERGY/Resources/336805-1137702984816/2135734-1142446048455/SWERIan.ppt
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/336805-1137702984816/2135734-1142446048455/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
Source: Armstrong 2002. Single Wire Earth Return
21
22
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/336805-1137702984816/2135734-1142446048455/SWERIan.ppt
5am
7am
9am
11am
1pm
3pm
5pm
7pm
9pm
11pm
S1
0
100
200
300
400
500
600
wat
ts
Miniature Circuit Breakers (MCBs) or PTCs to limit peak loads
Mini-circuitbreakerMini-circuit breaker can encourage peak load reduction
kWh meter
25
CASE STUDY - LOAD MANAGEMENT
Source: Schatz Energy Research Center
Voltage drops
• A 35 kW micro-hydro plant in Rukubji, Bhutan
• Lighting, TVs, rice cookers and water boilers are the common loads
As on many mini-grids, when load exceeded generation capacity, brownouts occurred
26
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.
27
GRIDSHARE LOAD MANAGEMENT TECHNOLOGY
Reduced spoiled rice
and
Residents stated:
“the grid is more predictable”
Electrical data indicated a reduction of over 90% in severe brownouts
Conclusions
Technology Application Impact
Interconnection relays mini-grid connect to main-grid
Lowers risk to developers of isolated mini-grids
Solar pico-grid Affordable pre-electrification
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
www.palangthai.org