Sovereignty Module: Capture the Wind
Complete Windmill Construction, Wind Power, and Mechanical Energy Guide
Wind is free, renewable, and available everywhere. Windmills have ground grain, pumped water, and sawed timber for 1,000 years. This campaign covers every windmill type from simple sail designs to multi-blade water pumpers.
Chapter 1: Windmill Types Compared
| Type | Blades | Power Output | Complexity | Best Application | Wind Speed Needed |
|---|---|---|---|---|---|
| Panemone (drag type) | Vertical axis, scoops | 0.1-0.5 HP | Very low | Water pumping (low volume) | 5+ mph |
| Post mill (European) | 4 sails, horizontal axis | 5-30 HP | High | Grain milling, sawing | 10+ mph |
| Tower mill | 4 sails, rotating cap | 10-50 HP | Very high | Large-scale milling | 10+ mph |
| American multi-blade | 12-18 blades, tail vane | 0.5-3 HP | Moderate | Water pumping | 7+ mph |
| Savonius (vertical axis) | 2-3 scoops, vertical | 0.1-1 HP | Low | Water pumping, small electric | 5+ mph |
| Cretan sail | 6-12 cloth sails, horizontal | 1-5 HP | Low-moderate | Water pumping, milling | 8+ mph |
| Modern HAWT (3-blade) | 3 blades, horizontal | 1-100+ HP | High | Electricity generation | 8+ mph |
Chapter 2: American Multi-Blade Windmill (Water Pumper)
| Component | Material | Specification | Function |
|---|---|---|---|
| Tower (derrick) | Steel angle or timber | 20-60 feet tall | Elevates rotor above ground turbulence |
| Rotor (wheel) | Sheet metal or wood blades | 6-14 feet diameter, 12-18 blades | Captures wind energy |
| Tail vane | Sheet metal on boom | Keeps rotor facing into wind | Self-orienting |
| Gearbox (optional) | Cast iron/steel gears | Converts rotation to reciprocating | Drives pump rod up/down |
| Pump rod | Steel rod | Connects rotor to pump below | Transmits power down tower |
| Cylinder pump (at bottom) | Cast iron/brass | At water level in well | Lifts water with each stroke |
| Furling mechanism | Spring or weight | Turns rotor out of wind in storms | Prevents damage in high wind |
Output: A 10-foot diameter multi-blade windmill in 15 mph wind pumps approximately 3-5 gallons per minute. Over 24 hours: 4,000-7,000 gallons. Enough for a small farm (livestock + irrigation).
Chapter 3: Simple Savonius Rotor (Easiest to Build)
| Step | Action | Time | Details |
|---|---|---|---|
| 1 | Cut barrel or drum in half vertically (two half-cylinders) | 1 hour | 55-gallon drum, oil drum, or sheet metal formed |
| 2 | Offset halves on vertical axis (S-shape from above) | 1 hour | Gap between halves = 1/6 diameter |
| 3 | Mount on vertical shaft (pipe or rod) with bearings | 2-4 hours | Top and bottom bearings |
| 4 | Connect to pump or generator at base | 2-4 hours | Direct drive (no gearbox needed for low RPM) |
| 5 | Install on tower or elevated platform | 1-2 days | Higher = more consistent wind |
Savonius advantages: Works in any wind direction (no tail vane needed), starts in very low wind (5 mph), simple construction, low maintenance. Disadvantages: lower efficiency than horizontal axis (15-20% vs 35-45%), limited power output.
Chapter 4: Cretan Sail Windmill
| Step | Action | Time | Details |
|---|---|---|---|
| 1 | Build tower (stone, brick, or timber): 15-25 feet tall | 1-4 weeks | Circular or square, sturdy |
| 2 | Install horizontal axle at top with bearings | 1-2 days | Heavy timber or steel shaft |
| 3 | Attach 6-12 radial arms (spokes) to axle | 1-2 days | Equal spacing around axle |
| 4 | Rig triangular cloth sails between arms | 1 day | Canvas or heavy cloth, furled/unfurled as needed |
| 5 | Connect axle to millstones or pump via gearing | 1-3 days | Wooden gears (lantern and wallower) |
| 6 | Add brake mechanism (lever pressing on wheel) | 1 day | Essential safety feature |
Cretan windmill: Used for 2,000+ years in Mediterranean. Simple, effective, repairable with basic materials. Cloth sails are adjustable (reef in high wind, full spread in light wind). Powers grain mills and water pumps.
Chapter 5: Wind Energy Calculation
| Parameter | Formula | Unit |
|---|---|---|
| Power in wind | P = 0.5 × ρ × A × V³ | Watts |
| Air density (ρ) | 1.225 kg/m³ at sea level | kg/m³ |
| Swept area (A) | π × r² (r = blade radius) | m² |
| Wind speed (V) | Measured or estimated | m/s |
| Maximum extraction (Betz limit) | 59.3% of wind power | Theoretical max |
| Practical efficiency | 25-45% (depending on design) | Actual output |
Quick estimate: Power (watts) = 0.15 × D² × V³ (D = rotor diameter in meters, V = wind speed in m/s). Example: 3m diameter rotor in 7 m/s wind = 0.15 × 9 × 343 = 463 watts.
Chapter 6: Site Selection and Tower Height
| Factor | Ideal | Acceptable | Poor |
|---|---|---|---|
| Average wind speed | 12+ mph (5.4+ m/s) | 8-12 mph | Below 8 mph |
| Obstructions | None within 500 feet | Trees/buildings below rotor height | Surrounded by tall obstacles |
| Tower height | 60+ feet (above all obstacles) | 30-60 feet | Below 30 feet |
| Terrain | Hilltop, ridge, open plain | Gentle slope, open field | Valley, forest, urban |
| Prevailing direction | Consistent from one direction | Mostly consistent | Highly variable/turbulent |
Rule of thumb: Tower must be at least 30 feet above any obstacle within 300 feet. Every doubling of height increases wind speed by 10-15%. Wind power increases with the CUBE of speed: double the wind = 8x the power.
Reference Card
- Wind power scales with CUBE of speed: double wind = 8x power. Height matters enormously.
- American multi-blade: best for water pumping. 10-foot rotor in 15 mph = 3-5 GPM.
- Savonius (barrel halves): easiest to build, works in any direction, starts in 5 mph wind.
- Cretan sail: 2,000-year proven design. Adjustable cloth sails, powers mills and pumps.
- Tower height: minimum 30 feet above all obstacles within 300 feet. Higher = exponentially more power.
- Betz limit: maximum 59.3% of wind energy can be captured. Practical: 25-45%.
- Quick power estimate: Watts = 0.15 × D² × V³ (D in meters, V in m/s).
- Furling mechanism essential: windmill must turn out of wind in storms or it self-destructs.