Small Wind Electric Systems
• Wind Turbine Electrical Output
– Electricity from a spinning shaft
• Balance of Systems
– Types
– Components
First Things First. What does a small
wind turbine produce?
• Wild Alternating Current (Wild AC)
– “Wild” due to the fluctuating voltage, current and
frequency.
– Why is this?
• Most modern small wind turbines are direct drive
permanent magnet systems (there are exceptions)
– In most cases the wild AC needs to be rectified.
• Conversion of Alternating Current (AC) to Direct Current (DC)
WILD AC
DC
120 AC @
60Hz
Electricity from a Spinning Shaft
Click Here for Animation
http://www.reuk.co.uk/OtherImages/moving-magnet-past-wire-to-make-current.jpg
Why Alternating Current?
• Simplicity of permanent magnets alternators
• This AC power is rectified to Direct Current
regardless of battery or grid-tie configuration.
• 3 phase output is most common
http://bp1.blogger.com/_Ist6QgbdKFo/SIsThFlYcTI/AAAAAAAAAGw/-cBy0MQjDvI/s400/5.bmp
Why Three Phase?
• Most effective use of space and materials!
Leads to Battery
3 Rectifiers in parallel
3 Phase Output
(Short) Kill Switch
Axial Flux PM Alternators
http://flyingv.ucsd.edu/nima/Axial_Flux/motor_cad.jpg
Small Wind Systems
Small Wind Systems:
• Battery (off-grid) systems
• Grid-Tie with battery backup systems
• Batteryless / Direct grid-tied systems
• Direct Drive Batteryless Systems
Battery (off-grid) systems
Regulation and
Conversion
Battery (off-grid) systems
Controller
Off-Grid Hybrid System
• Combines multiple DC charging systems
Battery (off-grid) Hybrid system
Controller
Benefits of Hybrid Systems?
Wind and solar compliment one another!
Hours of sunshine or average
wind power (Watts/m2)
400
350
Hours of
Sunshine
300
250
Average wind power
200
150
Data from SE Iowa
100
Jan
Feb Mar
Apr May Jun
Jul
Aug Sep
Oct Nov Dec
The Effects of Seasons on Hybrid
Power Systems
Summer
PV modules and wind turbine
(active generation)
Battery
(storage)
Loads
(utilization)
PV modules and wind turbine
(no generation)
Battery
(storage)
Loads
(utilization)
Winter
Grid-Tie with Battery Backup
Controller
Grid-Tie with Battery Backup
• Benefits:
– Potential sale of excess energy
– Battery backup during electrical grid failure
– Incentives supported
• Downfalls:
– Expensive
– Added maintenance (batteries)
Batteryless / Direct Grid-Tie Systems
Controller
• Benefits:
– Sale of excess energy to the grid
– Lower system cost
– Incentives supported
• Downfalls:
– No battery back up. If the grid fails you are left in
the dark.
Direct Drive Batteryless System
Controller
http://image.made-in-china.com/2f0j00seKTaQUBJEhy/Water-Pump-MKP60-1-.jpg
• Benefits:
– Simplicity
– Lowest in cost (no balance of system needed)
• Downfalls:
– Only power loads when resource is available
– Heating applications require large turbines