TECHNICAL SOLUTION
Name of solutionHugh Piggott Wind turbine
Category of solution
> Electricity production [LINK] > Energy storage [LINK] |
PDF version to download
Related Energy School
> Renewable energy | |||||||
Short introWind energy utilisation in wind mills is more than 2000 years old. In those days windmills were only used for mechanical purposes, such as grinding cereals. Even in the early 20th century a large part of water pumping in the US was achieved with windmills, while at the same time the first experiments with wind turbines for electricity generation started. During the 1970s an upscaling of research and development on wind turbines led to commercialization and the build-up of an entire wind energy industry. Those modern wind turbines are huge, industrial power plants converting the kinetic energy contained in the wind into electric energy via a generator. One of the most popular designs for small-scale DIY wind turbines stems from Scottish engineer and technician Hugh Piggot. He designed and built small wind turbines with a rotor diameter from 1.5 to 5 meters, and a power rating of 500 to 1500 Watt. While teaching others about those self-built turbines and offering a construction manual, the idea of small-scale wind turbines spread across the globe. Applications The main application for these small DIY wind turbines is in off-grid electricity systems on farms, homesteads or communities. Also these turbines can provide electricity in low-consumption cases in the global South and in rural areas of developing countries. |
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Complexity and cost of building and operatingLevel of difficulty Building: High Operating: Low to medium Cost Building: 300-1500 EUR (not including costs for anchors made out of concrete, stones or mounted in the ground, and not including supportive electrical systems, such as converters, battery-storage etc) Operating: 50 EUR/year 
Wind turbine number 1 in Suderbyn Ecovillage
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Description of the solutionWind is a renewable energy resource, and its kinetic energy can be transformed into mechanical and thus also electrical energy. Small wind turbines provide a possibility to run off-grid electricity systems and thus doing away with generators running on liquid fossil fuels. Small wind turbines are mainly put on masts between 8 and 15 meters. The wooden rotor of the wind turbines transforms the movement of air particles into a rotary motion. This transformation into rotation is achieved by using the aerodynamic principle of lift. The wooden rotor consists of three blades that are connected to a generator. The generator is an axial-flux generator, in which the rotary motion of the wind turbine rotor is transformed into electricity. The generator consists of disks fitted with magnets that turn with the rotor of the wind turbine. The stator (the part of the generator that does not move) is made up of several copper coils. The rotation of the magnets across the coils induces a voltage difference between the beginning and the end of the coils. The coils are connected as a three-phase system (dependent on the number of windings and the thickness of the copper wire the system voltage can be 12, 24, 48 V or even higher). If the three ends of each coil circuit is connected to a load or a battery electrons start to flow in the wire. In other word electric current runs through the wire and can either fill up a battery or can be directly used for a load. Depending on the diameter of the wooden rotor and the configuration of the generator, the rated capacity (at a wind speed of 10 m/s) of those small DIY wind turbines ranges from 300 to 1500 W. Wind speeds above 15 m/s can be detrimental to the tower and turbine. If wind speeds is believed to reach these levels, it is highly suggested that the wind turbine is lowered down in order to limit the risk of damage. Lowering the turbine is often done in 10-15 minutes and requires 3-5 people. This operation should be practised so that when needed it can be done efficiently and with control. If a site is subjected to high winds and/or seasonal storms, a reinforcement of the tower is suggested in order to prevent the pipe from bending. In combination with control electronics the alternating current produced in the wind turbine can be transformed to direct current and stored in a battery. Hybrid off-grid systems can consist of wind turbines, solar photovoltaics and possibly small-scale hydro to provide greater resilience against the intermittency of renewable energy sources. List over the properties of the solution and the system + renewable energy source + electricity generation + no fuel costs + lower environmental and carbon footprint compared to diesel generator + improved resilience for electricity generation + low maintenance - design of off-grid system required - building a well-functioning wind turbine needs some expertise - only viable on sites with good wind conditions - batteries required |
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Skills, tools & materials requiredSkills:
The build of a turbine involves working with wood, metal, concrete and electrical systems. Experience from these kind of processes will beneficial but no specific skills are required, apart from electrical work that is demanding certificates in some countries.
Tools:
Building a small wind turbine requires a well-equipped wood, metal and electric workshop. as well as some special materials, such as magnets, copper wires and epoxy resin for casting parts of the generator. Materials:
Apart from material to the major components and structure of the turbine, special materials, such as magnets, copper wires and epoxy resin for casting parts of the generator are needed. A complete list of materials can be found in the downloadable manual that is suggested to be used for the entire build process. |
Conclusions and errors to avoidHard winds
One of the lessons learned from the windy conditions for Suderbyn, on Gotland, has been that there’s a need to make reinforcements of the tower-structure, as this has at 2 times been destroyed. Reinforcement of the tower, as well as decreasing the height of the tower have been two seemingly appropriate measures to address this issue. 
Reinforcement of the original pipes with flat iron to prevent bending in strong winds
Not allowed to give electricity to the grid and the electricity for heating water It might not be allowed to provide electricity to the main-grid without it being regulated, and challenges might be presented in order to find a solution. If this is technically not feasible, as it has not been in Suderbyn, there are alternatives. The energy could for example be used as DC (direct current) for a heating coil in a water-heater, which would transform the electricity directly to thermal energy and stored in a thermal battery (water-tank). The turbine still needs to be able to break itself, which is done by increased resistance, and if the temperature in the water-tank gets close to 100°C, the capacity to dump the energy decreases. It is important to think about this when designing such a solution, so that the energy can still be dumped and that the turbine can have a change to use its brakes, decreasing the risk for the blades to spin too fast and destroy the wind turbine. |
Cost & Life cycle analysisCost:
Construction phase: Only taking into account the turbine and the tower, not the electronics and the battery, or anchors needed as well. Depending on the size of the turbine and how much material can be scavenged from recycling stations or purchased second hand the price can range from 300-1500 EUR, excluding working hours and tools. Maintenance and repair: The most common costs associated with the maintenance or repair are made up by the time spent. In regards to materials it is mostly connected to paint, changing of bearings or new wood. LCA: Construction phase: Only taking into account the turbine and the tower, not the electronics and the battery needed as well. Energy requirements are taken from Low-tech Magazine. The table below depicts the energy requirements per material type for a small wind turbine. 
Approximate energy and material requirement for a small wind turbine
The energy requirements for the materials needed for a Hugh Piggot wind turbine amounts to approximately 3770 MJ or 1045 kWh. This number assumes all the material is new and nothing is being used from old materials or recycled parts. Being able to find especially steel for the tower and the hub of the turbine can reduce energy requirements by three quarters. The electricity needed for the tools to build the wind turbine is estimated to be about 5 kWh. Total energy requirement for the wind turbine (new material) sums up to 1050 kWh. A small Hugh Piggot wind turbine of 800 Watt capacity will produce roughly 1000 kWh of electricity per year at an average location. Energy pay-back time is therefore in the order of one year. Operating phase: No fuel is needed during the operating phase. Replacement of parts takes a small part of the energy requirement of a small wind turbine. About one new blade needs to be made every three years. This equates to an energy cost according to table 1 of 22 MJ or 6 kWh per year in the operating phase. Replacement of parts (mainly the blades): about one new blade in three years, 0.03 m3 of wood. |
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Step by step guidelines for building the solutionAs there are many specific instructions needed for both the building, assembling and maintenance of the Piggot wind turbine, it is suggested that a handbook is used. A version of this can be downloaded from the attached links regarding references and articles. These are either free or can be purchased in exchange for a small donation (10-15€).
Below is an overview of some of the steps involved in the making of the wind turbine, not necessarily shown in order. The wooden blades
The wooden blades need to be formed into an aerodynamic shape. The shape itself is important in order to optimise the efficiency of the turbine, but most important is that the 3 blades are as similar as possible. If the blades have different shape and weight it will create an unbalanced rotor which can both mean lower efficiency and create a risk of failure/damage when the rotor spinns with high speed.
The tail
The tail has the function of directing the rotor to the winds as well as protecting the turbine when the wind is too strong to prevent failure. It is made out of wood and can be done in various shapes, offering a good opportunity to be creative and give the turbine its own character. 
Example of tail
Example of tail being protected with epoxi as varnish
The stator
There are many steps involved when creating the generator. One step is to create templates and moulds for the coil winder and for the casting of the generator and its' parts.
The rotor
The magnets need to be placed on the metal disks and moulded in place. Remember to wear protection when handling epoxi and to be in a well ventilated space.
Metal work and assembling the parts
There are quite some metal work involved when building the solution and specific details can be found in the manuals. Make sure to wear appropriate protection and act in a safe manner when working with metals.
Electrical components
The wind turbine requires similar electrical system as an installation for solar panels, with a few alternation. One extra function that is needed is a dump load resistance which functions as a break for the turbine when needed.
Raising the turbine
As described above, 3-5 people is needed for raising and lowering the turbine. If the turbine would be larger than what is required for 1 kW max output, the solution would be too heavy to be handled without specialised equipment. 
A pully-device is valuable when raising or lowering the turbine
Enjoy your turbine and the wind! |
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Legal & legislationIn many jurisdictions small wind turbines can be erected without a building permit if the tower is below 10 meters. However local building codes might differ. Depending on the intended usage of the electricity, specific regulation might apply, both in terms of specific certificates needed for installation as well as if the electricity is supposed to be connected to the local grid. Communication with the local grid-provider is needed in order to understand what is allowed, or what measures need to be taken.
References & Relevant links and articlesThere are many available versions of manuals online. Here is one example:
https://scoraigwind.com/pmgbooklet/itpmg.pdf http://scoraigwind.co.uk/about/ https://www.youtube.com/watch?v=vhXtW0s9T6w&t=2s https://globalsustainabilityblog.wordpress.com/2015/02/04/build-a-small-wind-turbine-construction-course/ https://erni-kollektiv.org/ Local prototypeSuderbyn ecovillage in Sweden has 2 turbines operating that has been built on site.
Place: Suderbyn, Gotland, Sweden Period: 2017 - Contact: info@suderbyn.se Example: http://www.suderbyn.se/closed-loop.html Other examples: Place: Scoraig, Scotland, UK Period: 1990 - Contact: hugh@scoraigwind.co.uk Example: http://scoraigwind.co.uk/about/ Place: Berlin, Germany Period: 2016 - Contact: info@taschengeldfirma.org Example: https://taschengeldfirma.org/windrad-thf/ Who are the people, community, institution and/or organisation operating the prototype?Suderbyn Ecovillage, an intentional community with a population of 20-25 people.
Experts involvedSimon Goess
simon.goess@gmail.com Contact informationAuthor of the contentSimon Goess
Martin Ahlström |
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