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Session Overview
• Provide an overview of renewable based power systems for rural areas.
• Describe renewable power penetration and the basic design of wind/diesel power systems
• Provide examples of power systems that have been installed.
• Review common power system components and their purpose
Session Goals
Provide a basic understanding of renewable based hybrid power systems
so that attendees will be able to understand these power system options
Key Messages
Hybrid power systems are an economic reality that can be used to limit or
reduce the dependence on diesel fuel and may provide power to remote
communities at a lower life cycle cost that other traditional alternatives.
Stages of Remote Power Systems
Renewable power system can be used to cover a wide range of needs.
These include:– Dedicated use: Water pumping/ice
making. – House systems: Power systems for
individual buildings, dispersed generation.– Community Power Systems: Power
provided to a large community with large loads
– Wind/Diesel Systems: Large communities with large loads
Agricultural Water Pumping
• Livestock watering at the Bledsoe Ranch Colorado, USA
NEOS Corporation
• PV, Mechanical wind and diesel backup solves problems with seasonal variations in resource
Direct Water Pumping
• Ranch near Wheeler, Texas
• Water-pumping for 120 head of cattle
• Whisper 1000 wind turbine, 1 kW, 9-ft rotor, 30-ft tower
Small Power Systems
• Systems do not have a dispatchable backup generator like most hybrids
• Very simple architecture:– Turbine, PV, Disconnects, Batteries– DC Loads or AC power through an inverter
• Primarily PV dominated for small loads, wind has potential at larger loads.
• In many instances a combination of PV and wind make most sense
• Can vary in size, power output
Energy Flow for a Small Hybrid
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Solar Home System
• Provide entry level of service– Lighting, radio– DC service
• Expandable in size, >20W
• Cost ~$700 for small unit
• Developed market
Wind/PV Home Systems
• Provide more energy
• AC Power• Higher output• Lower $/kW
Inner Mongolian wind/PV system
Village Scale Power Systems
• Larger, village scale power systems use centrally located power plants and distribute AC power to the connected homes.
• Single point of service and maintenance• Usually use larger or multiple generation units
to improve operation performance and benefit from quantities of scale benefits
• Act very much like small power utilities • Provide “grid” style power
Village System Architecture (DC)
D C Loads
Turbine Disconnect
Guyed Lattice Tower
Inverter or bi-directional converter
Turbine Controller
D C Source C enter
Battery Bank
P V C harge Controller
W ind Turbine
G enerator
AC Loads
PV Array
Micro-grid System Architecture (AC)
W ind Turb ine
G uyed Lattice Tow er
Turb ine D isconnect
G enerator
Turb ine Inverter and C ontro ller
PV Inverterand C ontro ler
PV A rray
B i-d irectional C onverterand System C ontro ler
Battery Bank
AC Loads
Micro-Grid Power Systems
• Supply communities with demands from ~100kWh/day load (15 kW peak load) up to ~700 kWh/day (75 kW Peak load)
• Components of wind, PV, biomass, batteries and conventional generators
• Generally provide AC• Use of batteries to store renewable energy for
use at night or low renewable times• Generator used as backup power supply• Mature market
Parallel System
•Morocco•Algeria•Jordan•Ghana•Egypt•Southern Africa Region•(Nigeria, Mozambique)0
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Both diesel and inverter needed to cover the maximum load.
Both units run together.
Woodstock, Minnesota• Wind farm maintenance shop and office
• Electric loads include lighting, PC, and shop tools
• Passive solar day-lighting, corn used for space heat• Installed cost $6,800 in 2001 (grid extension
alternative: $7,500)
• 1200 ft2 shop, 900 ft2 office
• Whisper H40 wind turbine, 900 W, 35-ft tower
• PV panels, 500 W
• 24 VDC battery, 750 Ah
• 4-kW inverter, 120 VACsingle phase
Santa Cruz Island, California, USA
• Remote Telecommunications station• Power System
– PV array– Two wind
turbines– No Backup
generator• Vary costly
access/site visits• Remote operation
and monitoring of system
Northern Power Systems
Mt. Newall, Antarctica
• Science Foundation Station project
• Repeater and Seismic monitoring station
• Power System– 3.3 kW PV array– Diesel generator– HR3 wind turbine
Northern Power Systems
Isla Tac, Chile• Island community
with Health post, school and 82 homes
• Power System:• 2x7 kW wind turbine
s• Flooded batteries• 2 x 4.5 kW inverter• 16 kWA backup gas
generator
Subax, Xinjiang, China• Small community of
60 homes in very remote part of Western China
• Power System– 2 BWC excel (8kW)
turbines– 2 15 kVA Inverters– 4 kW PV– Low Maintenance
battery bank– 30kVA diesel generator
Dangling Rope Marina, Utah, USA
• Remote National Park Center
• 160 kW PV / Propane generator hybrid system
San Juanico, Mexico
Remote fishing community of 400 people with tourism
Power System• 17 kW PV• 70 kW wind• 80 kW diesel
generator• 100 kW power converter/controller Advanced monitoring system
Wind-Diesel Power Systems
• Larger systems with demands over ~ 100 kW peak load us to many MW
• Based on an AC bus configurations• Batteries, if used, store power to cover short lulls in
wind power • Both small and large renewable penetration designs
available• Large potential mature with fewer examples• Due to cost - PV generally not used
Penetration
Instantaneous Penetration:
– Voltage and frequency control – Reactive power
Average Penetration: (generally a month or a year)
– Total energy savings– Loading on the diesel engines– Spinning reserve losses/efficiencies
(kW) Load ElectricalPrimary
(kW)Output Power WindnPenetratio ousInstantane
(kWh) DemandEnergy Primary
(kWh) ProducedEnergy Wind n Penetratio Average
There are many different potential configurations for Wind – Diesel power systems, one of the critical design factors is how
much energy is coming from the wind – called wind penetration
AC Based Hybrid System• Low penetration systems - Wind acts as a negative
load, very little control or integration of wind turbines into the power system is needed .
• Mid penetration systems - Wind becomes a major part of the power system. Additional components and limited automated control is required to insure that power quality is maintained. Little operational control required though may be used.
• High penetration systems - Completely integrated power system with advanced control. Limited operational control of system by plant staff
System Penetration
These are really three different systems which all should be considered differently
Note: People play loose with the definitions
Low Medium High
Peak Instantaneous
<50% 50 – 100% 100 – 400%
Annual Average
<20 20 – 50% 50 – 150 %
Commercial status
Fully utilized
Well proven Fully commercial Multiple use
System prototype Operating
Examples Denmark, Greece
San Clemente, CA Kotzebue, Ak Coyaique, Chile
St. Paul Wales Ak
Diesel Only Power System
Po w
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Time
Diesel Gensets
Village Load
System Controller
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Multiple Diesel Plants with ControlIn multiple diesel systems the diesels may be dispatched to take advantage of size and load.
Generally requires automatic diesel control.Favorable in power systems with renewables
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Load, kW Dsl #1Power Dsl #2 Power
Potential use of a 500 and 1000 kW diesels
Low Penetration wind/diesel system
Diesel Gensets
Wind Turbine
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System Controller-20
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Kotzebue, Alaska
• 11 MW remote diesel power station in Northern Alaska
• 2 MW peak load with 700kW minimum load
• Installation of 10 AOC 15/50, 50 kW wind turbines and 1 NW 100, 100kW wind turbine
• KEA, Island Technologies, AOC
Coyaique, Chile
• Large regional distribution system
• 3x 660 kW wind turbines• 4.6 MW of mixed hydro• 16.9 MW of diesel
• Manually operated through local control center
• Currently runs as a wind/hydro facility
Medium Penetration W/D Schematic
AC Wind Turbines
AC Bus
Community load
System Control
Diesel Engines
C ontro lD um pLoad
San Clemente Island, California
Plant Details• Four generators
• 3 NEG-Micon 225 kW turbines
Yearly impact -• $97,000 fuel savings• 871,785 Ton CO2
avoided
• U.S. Navy island off San Diego• Diesel powered grid• 850-950 kW avg; 1,400 kW peak
Ascension Island• U.S. Air Force installation in the Atlantic ocean.• Prime diesel generation with rotary interconnect to
British 50 hertz system• Four NEG-Micon 225 kW turbines.• Operating since 1996• Average penetration 14-24%
Expansion in 2005• 2 MICON 900 kW turbines• Synchronous Condensers and 2 electric boilers for fresh water
Impacts• 650,000 gal/yr fuel saved
Selawik, Alaska
• Small Alaska Village Electric Cooperation community in northern Alaska
• Installation of 4 e15, 50 kW wind turbines and dump loads
• Part of a diesel plant retrofit project AVEC, Entegrity, Sustainable Automation
Toksook Bay, Alaska
• Small community in western Alaska• Installation of 3 NW100kW turbines and dump
loads• Part of a diesel plant retrofit project• Installed winter of 2006
AVEC, NPS
High Penetration w/out storage
AC Bus
C ontro lSystem
SynchronousC ondenser
C ontro lD um pLoad
D ispatchedLoads
Wind Diesel without Storage
When the wind power is larger than the
load by some margin - Diesel is shut off.
• Frequency controlled by dump load
• Voltage controlled by condenser
-20
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Red = DieselBlue = LoadGreen = Windpower
High Penetration W/D Schematic
AC W ind Turbines
AC BusD C
R otary C onverter
Battery
D C Bus
C ontro lSystem
C ontro ledD um pLoad
AC
AC D iesels
D ispatchedLoad
Wind/Diesel with Short Term Storage
• Diesel used to provide power to system when the wind can not cover load.
• Battery used to fill short gaps in or to start diesel
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Battery power (Charging is negative)
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Diesel p
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St. Paul Alaska, USAIsland in the middle of the Bering SeaPeak load of 160kWCost of Power, + $0.21/kWhWaste energy used for heatingTDX and Northern Power Systems
Wales, Alaska
• Remote community in Northern Alaska
• 80kW average load with 2 AOC 15/50 wind turbines
• Short term battery storage with rotary converter
• Resistive loads used for heating and hot water
• Operation with all diesels turned off• Problems with maintenance and
operation• AVAC, KEA and NREL
Systems and Components
• Hybrid power systems are made up of separate pieces of equipment that are brought together to form a cohesive power system
• Configuration and component size depend on the load and resource available at site
• Controlling the power systems is a complicated question, both logically and technically.
• Must understand the components
Dispatchable Generators
• Generators that can be turned on with short notice.– Diesel, Gas, Natural
Gas, Bio-gas• Usually require a lot of
maintenance• Role depends on system
design.• Wide range of old and new
technology• Wide range of control
40 kW Diesel Generator
10 kW Diesel Generator w/Fuel tank
Wind Turbines for Hybrids
• Range in size from 300W to 750kW
• Large AC turbines for diesel plants
• Small turbines designed for remote applications, generally DC but also AC being developed
• Self erecting or tilt up towers common
• Installed cost $3-6/W with production from $0.10-0.20/kWh
Northwind 19/100
Entegrety e15
Bergey XL10
Photovoltaics
• Applicable for small, remote applications
• Installation cost of ~$10/W, LCC of $0.22/kWh
• Low maintenance requirements
• Quite accepted internationally
• Not used commonly in large applications but there are some examples
PV on Active Tracker
Micro and Run of River Hydro
• Applicable for areas with a dependable resource.
• Lower head systems available
• Run of river up to 50kW pre-commercial
• Generally larger infrastructure cost
Micro Hydro facilityat remote ranch
UEK 50kW flow turbine
Hybrid System Power Converters• Convert energy from DC to AC
and back• Some units contain power system
control• Solid state or rotary systems• Solid state range in size from 1kW
to 300kW• Rotary systems built to size
depending on needs• Combined with batteries for
storage
Trace Tech 100 kW
converter
Wales AK 156 kW rotary
converter
Xantrax 4kW converter
Batteries• Many types
– Lead Acid (deep cycle and shallow cycle)
– NiCad• Two uses/sizing:
– Store energy to cover long periods
– Store power to cover short periods
• Requires periodic replacement
• Sensitive to environment• Life dependent on use and
the environment
Other Power Control Devices for Large Power Systems
Flywheel
Low Load Diesel
75 kW Synchronous Condenser
Grid Conditioner
Controlled Dump load
System Controllers
Monitoring and Remote Access
• Remote access allows oversight of system performance
• Enables real time system interrogation and troubleshooting even when off site
• With expert analysis system reduces maintenance and down time
• Small incremental cost
That looks simple – doesn't it?
The design and implementation of power systems is a complex matter and although the models (and initial presentations) make it look
simple, it is never that easy.
Every power system is complicated, some much less than others but you do need to think about the design and how it will be
implemented.
The Complication is with Uncontrolled Generation
By their nature renewable generation are stochastic (uncontrolled) and vary with the resource.
The amount of variation and thus the amount of system control to handle the variation depends
on the
1. Renewable resource being used2. The load3. Power system design
Two basic types• DC based systems that feed AC loads
– Relatively simple in nature
– System control provided by the battery bank based on battery voltage
– Issues associated with component efficiency and power factor of the loads
• AC based systems– More complex in nature
– System control needs to be considered carefully since it many cases it must be done actively
– Issues of power quality and system stability
DC Based Small System Architecture
Turb ine D isconnect
G uyed Lattice Tower
Inverter (b i-d irectional optional)
Turb ine Contro ller
D C Source Center
Battery Bank DC Loads AC Loads
PV C harge C ontro ller
W ind Turbine
G enerator
PV Array
Power system schematic
W T G (B W C E xce l R 7kW )1 2 0 V , 3 P , 3 W
G
Turb ine 1.8 D ow n-Tow erD isconnect
40A
1.5" EM T3-1/C #61-1/C #8 G ND.3-1/C #6 Arm ored, Jacketed Cable
S ite 1 .8 O ne-L ine E lectrica l D iagram for BW C Insta lla tion(C hile R eplica tion P ro ject)
G N D . R O D
1-1/C #2 G N D.
G
Turb ine 1.8 C ontro l Room
D isconnect40A
1.5" R T C om p EM T3-1/C #61-1/C #8 G ND.
30 K VA: 36 .1A P rim ary
480V /208V
110A
G
1.5" R T C om p EM T3-1/C #11-1/C #6 G ND.
P os. FusedS olid Neg.300A
2-1/C 1 /0 W eld
2-1/C 1 /0 W eld
2-1/C 4/0 1-1 /C #4
Inverter5 .5 kV A, 1P4 8 V D C - 1 2 0 V AC
Kohler Generator5 kV A, 1P
1 2 0 V AC
50 AG
.5" EM T2-1/C #8 1-1 /C #8
GN
G
G N D . R O D
D C B us
G
G
Trojan T105 Battery Bank4 8 V , 5 2 k W h
W TG C ontro ller
R ectifier/V oltage R egulator
L igh tn ing Arrestor
LP 1.8
To Load To Load
P os. FusedS olid Neg.250A
P os. FusedS olid Neg.150A
G
G
G G round B ar (or equ iva lent)
G
.5" EM T2-1/C #8 1-1 /C #8
.5" EM T2-1/C #8 1-1 /C #8
1-1/C #8
1-1/C #8
continuous1-1/C #8
1-1/C #8
(DC)
Neg
Neg
Neu
Neu
50A or less
1-1/C #4 G nd
N o N egative /G round C onnection
N o N eutra l/G roundB onding Jum per
1-1/C #4 G nd
System Drawings and Documentation
All systems should have simple one line drawing that shows the location and
size of all of the fuses and circuit breakers in the system. This should be
posted in the building and will help people find problems.
Things to worry about in DC based systems
• True availability of your battery (due to control and temperature)
• Yearly variation in resources and loads• Starting currents on large loads• Space requirements for components• Maintenance and service infrastructure• Venting of battery bank
Wire Losses• Lower voltages
mean higher currents
• Higher currents mean larger wires (or higher losses) (increased cost)
Basic Electrical
• Everything should be fused with the ability to disconnect specific components if that is needed.
• Good junction boxes that are properly installed
• Cables are well protected and buried
Grounding
2.2
2.2
2.2
2.22
.2
2.2
2.2
2.2
2.2 2
.2
1
2
34 5
6
7
35
Energy Sys tem
Wind T urbine/T ow er
E lec tric al/E lec tronic Equipment
Grounding Details• Solid ground for towers or PV arrays further than 15m from
main junction • Lightning arrestors to protect towers• Lightning arrestors to protect the electrical/electronic equipment• Transient voltage surge suppressors (TVSS) for the most
sensitive electronic equipment• Solid ground for all metallic housings of equipment• Grounded metal conduit for buried power leads• Low impedance connection to earth potential• Tied earth planes to eliminate potential differences
Facilities• Water proof with
overhang• Separate rooms
for major components
• Safe diesel storage
• Ventilation• Good lighting and
security• Work
environment
Site Issues• Access issues - need to be sure
you can get to the site when it is needed
• Strong Fences - Keep animals from damaging equipment, gives the sense of importance to the site
• Good and plentiful signs - Keeps people safe and off equipment
Things to Worry About
• Power factor of installed loads• Temperature (for batteries) • Environment – Corrosion,
humidity - protective coatings• Vandals, animals, insects...
Lead Acid Batteries … the known evil
But there is nothing else that is really available, especially in
remote areas, that can compete based on simplicity,
cost and availability
Battery explosion at a school
system in Chile
Batteries Can Be DangerousThe use of batteries has to be considered carefully and
appropriately.. This starts from proper system design
Wireless Energy, Chile
General Battery Types
• Starting Batteries– Automotive applications– Unsuitable for renewable
energy storage (but are commonly used due to availability)
• Deep Cycle Batteries (traction or stationary batteries)
– Robust construction designed for repeated, deep discharge
– Highly suited (even optimized) for renewable energy storage
Considerations for Batteries• The deeper the discharge, the fewer the cycles • One bad battery can bring down the whole string and
can even affect parallel strings (practice due vigilance)• Ensure a reliable supply of distilled water• Avoid leaving batteries at a low state of charge for long periods• Extractable capacity dependent
on a number of factors
http://www.benchmarking.eu.orghttp://www.ecn.nl/resdas/
Conclusions• There are a lot of options / configuration of hybrid
systems - Depend on load, resource, and costs.• Many configurations for small DC-based power
systems for smaller communities or individual loads• Options for larger communities are also available –
Advanced diesels and control, locally derived bio-fuels, wind/diesel applications
• Renewable based rural power systems can help supply energy to rural needs in a clean, inexpensive way that does not burden the national economy
• Configuration depends on many factors• Social issues dominate over technical issues• Its never as easy as it seems
Renewable power systems havea place in rural development