The Technology of blueEnergy

Turbine

For starters we want to acknowledge the work of Hugh Piggott of Scoraig Wind Electric. The design used by blueEnergy is largely based (about 95%) on his work and his tireless efforts to improve the design and share it with the world have been an inspiration for us. If you are considering building your own wind turbine, we strongly recommend you purchase a copy of Hugh's most up-to-date plans, which can be found here. In addition, we recommend you get his book "Windpower Workshop" (found at the same site) and read it before you dive into construction. If you are really serious, attend a turbine building workshop hosted by Solar Energy International (SEI) and learn from the experts. This page DOES NOT represent a comprehensive guide to building a wind turbine and is meant as a survey of the technology. Also keep in mind that the process described here is for building turbines in Nicaragua and may be different from your situation. Building a wind turbine is fun and exciting, but is also complicated and can be dangerous if not approached properly. We recommend that you join the discussion groups "Fieldlines.com" and "awea-wind-home" to hear about other people's experiences before you get started.

The main components of the turbine include: body, alternator, rotor (blades), and tail.

Body (i.e. Hub/Carriage)

The body is made up mostly of welded pieces of 5 cm (2 in.) angle iron and houses a used car wheel hub, which serves as the bearing for the rotation of the blades and the alternator. The body is the connection piece that allows the horizontal axis of the rotor to be mounted on the vertical axis of the tower. The body also includes a hinge for the tail vane boom.

Alternator

The alternator is an axial flux permanent magnet design. It is composed of two magnet rotor discs and one copper coil stator. In the 2.6m (8ft.) diameter turbine model, each rotor disc has 12 rare earth neodymium magnets (NdFeB) mounted on to it and the stator has 10 copper coils. The copper coils are hand-wound and the number of turns per coil determines the output voltage (we use 80 turns per coil with #15 wire for 12 V, 150 turns per coild with #18 wire for 24 V, and 290 turns per coil with #21 wire for 48 V). Both the magnet rotor discs and the stator are cast in common boating resin and reinforced with rough fiberglass cloth. In this configuration the alternator produces a 5-phase alternating current. Finally, the 5-phase AC output of the alternator is rectified by five bridge rectifiers (using diodes) to produce DC for battery charging.

Blade Rotor

The turbine rotor consists of three wood blades, which are hand carved using primarily drawknives and spokeshaves. Wood is currently the preferred material for several reasons: it is cheap, locally available, strong, and local craftsmen already know how to work with it. The wood used is Nancitón, a local tropical wood with a blood-red color that has proven to be very resistant when it dries out. There were some initial problems with blades warping after carving due to the wetness of the wood, but that was mostly solved by introducing a drying period prior to carving. Other woods are currently being tested including Mahogany which is also locally available. Mahogany has the advantage of being easier to work with, however it is a weaker wood. blueEnergy is experimenting with resin-coated Mahogany blades to see how they hold up against the frequent rain showers of the region.

Other experiments are being carried out with fiberglass blades, which would lead to a significant improvement in the standardization of the manufacturing process. Fiberglass is more expensive than wood but is also a material that local craftsmen are familiar with due to the boat building and repair industry in Bluefields.

Tail Vane

Lastly the turbine is given a tail vain, which serves two very important purposes: keeping the turbine facing into the wind during normal operating conditions and turning the turbine out of the wind during dangerously high winds. A detailed description of the tail vane mechanism is provided in Hugh's literature. The tail is made up of a piece of steel pipe and a piece of plywood.

Basic Specs

The turbine specifications provided here are VERY ROUGH ESTIMATES. They have NOT been confirmed yet by field tests and should be viewed skeptically. The apparent decimal point precision is artificial as it was generated during unit conversion and kept to avoid conversion value confusion.

Cut-in Speed ~ 2.7 m/s (6 mph)

Rated Power ~ 500 - 600 watts @ 9.8 m/s (22 mph)

Max Power ~ 800 watts

Cut-out Speed ~ 12.5 - 13.5 m/s (28 - 30 mph)

See pictures of the construction of a complete turbine (made in Oregon, USA)

See pictures of the construction of a complete turbine (made in Bluefields, Nicaragua)

Tower

Tower

The most common tower being built is a standard tilt-up 20 m (60 ft), guyed tower. The tower is made of 7 m (20 ft) sections of 10 cm (4 in.) diameter steel pipe. The sections are connected to each other with couplers that fit on the inside of the pipe. A rebar-enforced concrete base with a steel hinge provides a foundation for the tower and allows it to be raised and lowered.

Guy Wires

Guy wires are used to stabilize the tower and maintain verticality. When the tower is standing up, most of the weight points along the axis of the tower and the tower itself supports the weight. However, during the lowering and erecting of the tower, guy wires support most of the weight through the use of a leveraged pole called a ginpole. In addition, when wind strikes the turbine it creates a force (which creates a moment about the hinge at the bottom of the tower) that tries to topple the tower in the direction of the wind. The guy wires act to resist this toppling force. For a 20 m (60 ft) tower, the guy wires are made out of threaded stainless steel, 0.6 cm (1/4 in.) in diameter. Wires are attached in all four directions every 7 m (20 ft).

Anchors

The guy wires are anchored at the four corners. The anchors (also called “dead-men”) are made of two pieces of steel I-beam welded together, providing a resisting area of approximately 0.5 m^2 (4 ft^2) . They are painted with an anti-oxidant paint and buried 1 m to 2 m (3 ft to 6 ft) deep depending on soil characteristics. Metal chains are attached to the anchors and rise to the surface where they are connected to the guy wires.

See pictures of tower construction in Bluefields, Nicaragua

Electrical System

Batteries

Batteries are the heart of a renewable energy system. They are used to store the irregularly produced energy from the generators and allow the operators to use the energy when they desire. The project promotes the use of deep-cycle batteries, which are well suited for use in renewable energy systems as they are designed to handle many deep discharges. While they have a higher upfront cost than car batteries, they are much cheaper in terms of dollars per kWh delivered over their lifetime, if they are well maintained.

Charge Controller and Dump Load

Batteries are also the most sensitive part of a renewable energy system and must be protected from overcharging as well as over discharging. A charge controller is used to regulate the charging of the battery by diverting the energy produced by the generator to a dump load when the battery is full. Like hydro generators, wind turbine should always have a load on them to regulate their rotation speed. The simplest type of dump load, and the one build by the blueEnergy, is an air heater. blueEnergy builds dump loads using locally available spare filaments for hot water shower heads.

Inverter and Power House

The battery bank provides DC power. If AC appliances are desired then an inverter is installed to convert DC to AC. A power house is constructed near the base of the turbine tower to organize all the electrical components and protect them from children, animals, and the elements. Finally, structures are hard-wired for end-use of the electricity.

Solar Component

blueEnergy is supplementing its wind energy systems with small amounts of solar power to help even out energy output and provide a boost during low wind months.

Other Projects Using Similar Turbine Designs

The Dans of Otherpower.com: here and here
Mark Pitterle of PLACES: here
Peter Haas of AIDG: here
Many many more at Fieldlines.com