DIY Piggott Wind Turbines – Background information

The Ferrite Alternator Wind Turbines used by PureSelfMade

These are the wind turbines mostly built in PureSelfMade workshops or projects, although other sizes and types have been built too. They are all based on the Hugh Piggott design.

The 2F Turbine

The 2F Piggott Turbine Design

  • 2 m Rotor Diameter
  • 500W Rated power output at 12 m/s wind speed
  • 12/24/48 volt off grid battery charging or high voltage for grid-tie inverter
  • Annual energy production:
    ~500kWh / year @ 4,1 m/s average windspeed*
    ~1000kWh / year @ 5,6 m/s average windspeed*
  • 350€ – 400€ Material cost

2F Power Curve measured by Hugh Piggott

The turbine is mainly constructed following Hugh Piggott’s plan, although minor modifications are made.
A german translation of the Construction Manual is currently in progress by PureSelfMade.

The 4F Turbine

The 4F Piggott Turbine Design

  • 4 m Rotor Diameter
  • 2000W Rated power output at 12 m/s wind speed
  • 24/48 volt off grid battery charging or high voltage for grid-tie inverter
  • Annual energy production:
    ~1800kWh / year @ 4 m/s average windspeed*
    ~3000kWh / year @ 5 m/s average windspeed*
  • Around 700€ Material cost

The “F” machines have ferrite permanent magnets in their generators. What? But they are weaker than high-end rare earth neodymium magnets!! Yes that is true. But they have some great advantages too. They are much cheaper than neo magnets and because they are based on ceramic material they do not corrode. That is a big advantage in terms of lifetime and maintenance.

The Generator

All these turbines are constructed in a similar way, designed by Hugh Piggott. They have a rotor of three wooden hand carved blades, a disc

generator of two magnet rotors and one stator, a steel frame holding everything together and a tail that makes the machine face the wind. The tail also works as an overload control – when the windspeed rises too high it swings to the side and makes the whole machine “furl” out of the main wind direction. All by mechanic forces and wind pressure. No electronics involved.

The rated power output of a wind turbine is the maximum power a wind turbine is designed to produce. This value will only be reached in high winds and is therefore not very informative. Much more important is the amount of energy produced over a certain period of time.

The kWh numbers are just calculated by the average windspeed. In reality, the energy production will be higher, because power in the wind rises with the cube of the wind speed. Therefore, deviations above the average windspeed will have a greater impact than deviations below the average.

To get a more accurate result, you need to know the hours of each windspeed for a time period. Then you can calculate the deviations off the average caused by the cubic curve. The data would look like this for example:

234h  – 4 m/s
375h  – 5 m/s
286h  – 6 m/s
478h  – 7 m/s

and so on… Modern dataloggoing devices can record this kind of data.

The Power a wind turbine delivers rises:

  • with the rotor diameter squared
  • with the windspeed cubed

That means:

  • Twice the diameter gives you 4 times more power.
    It also requires 4 times strength of the construction and will cost more.
  • Twice the windspeed will give you 8 times the power, at the same cost.

Therefore in the end of the day it’s always better to have more wind (a higher tower or a better site) than a bigger turbine!

The environmental impact

Is it much “greener” to build a DIY wind turbine at home than buying a commercial one?

This question is quite hard to answer. For a really accurate calculation of the environmental footprint, you would need to know all the energy used and the co2 emitted while building the turbine. This also includes the manufacturing of the individual materials and their shipping. It becomes clear that it’s difficult to get proper results.

In general, I would say with a home built turbine you are more flexibel. You can chose your raw materials yourself and also you’re able to recycle a lot if you have resources of second hand stuff. It’s not very hard to find scrap metal or other useful parts for a wind turbine. Everything you recycle is something that doesn’t need to be produced newly, so that saves a lot of energy.

It’s worth considering that. One kg of Aluminum for example takes about 50 kWh in manufacture and also steel is not much different. The turbine needs to work a while to bring that back in. Recycling of materials makes this balance much better.

And even once the machine has brought back in all the energy thats being used in manufacturing, the fact that it has released toxic waste into the environment during some material production remains…

The cost of self-made small wind turbines

Normally it will be much cheaper to build a wind turbine yourself than buying a commercial one. It will eliminate all cost spent on marketing an and labour. For example, the materials of the 2F machine For example the material cost for the 2F machine is 350€ – 400€. That’s for the turbine head only, any additional system components are not included. This is much less of what a co

 

mmercial turbine of the same size would cost. The cost of DIY things always varies with the source of materials. If you can find second hand steel on the scrap yard or you already got wood around, it will save you some money. The Piggott turbines can of course compete with commercial machines (regarding energy production for example) and you gain a huge lot of experience and have good fun when building it yourself.

So if you ask me, doing it yourself is totally worth it, in several ways!
I try to provide the knowledge needed in my workshops, shaped in a nice experience for your life.

So when does it make sense to install a turbine?

A 2F Piggott turbine at a good site

It’s definitely worth doing a bit of planning when it comes to small wind turbines as an energy source.

So, when does it make sense to put up a small wind turbine for energy production? I know, one of the biggest reason for the turbine is because it is a lot of fun to build it and you will learn a lot, but this article is about the efficient use for energy production, explained in a straight forward way. The you look at it with the hard facts in the back of your mind, it will become quite clear that it is not really about putting up a wind turbine and being “Self Sufficient” or “Independent”…. I’m sorry, but it is not that easy…

First, what you need to run a turbine is WIND of course! (what a surprise…) And that doesn’t just mean “we have a windy place here so it should be fine”. Your site should be exposed and you really need to have a fairly constant blowing wind, which should not have any objects in the way. If you have trees or buildings around and your turbine tower doesn’t really go way up above those objects, the air is very turbulent. This will cause a lot of wear on the wind turbine and will reduce the energy production significantly. I know there are a lot of urban wind power projects but all these factors do not really look good in urban areas, so let’s see how the urban wind power things will come along…

I really like wind turbines and the way they work, but these things need to be said. It’s just to keep it real and realistic.

Mostly it makes sense to do some wind speed measurements over a period of time to figure out if your site has enough windspeed in average to make a small wind turbine work effectively. There are also some sits where one can tell at a first look if the site is a good or a bad one (the balcony is a bad one for example)

In general, Piggott wind turbines have quite a broad range of use, because they can be built in all different sizes system voltages, so they will fit most requirements.

Off-Grid system

In places where there is no mains electricity grid. In this case it will be a battery charging wind turbine configuration that either works on battery voltage and feeds straight into the battery of the system or it hast a controller (MPPT) to optimize the performance. Typical situations are: Buildings in remote areas, installations in developing countries, remote communication systems,… Batteries are necessary to stabilize the system voltage and to provide your system with power if there is no wind.

The energy can be used straight from the batteries as low voltage DC, but normally you will have an inverter that boosts the battery  low voltage DC up to 230V / 50Hz AC (mains level) for your loads.

The system needs to be designed to mach the loads, so you first need to find out what to power with your off grid arrangement and then you can define how big you will mage the components. It is not only important to know the maximum power of all the loads being switched on a t the same time, It’s also very important to define the time of each load to be switched on in a day. That you will need to determine the energy consumption and afterwards the battery capacity, the size of wind turbine, and so on…

Feeding into the electricity grid

That’s the way to go if you are not off-grid and want to use the turbine as a “green” energy source. In this case you will need a Grid-Tie Inverter that is connected straight to the wind turbine and feeds the energy into the grid. You normally will not need a battery in this scenario, although there are hybrid systems which have a battery as well so you can run your system even if the grid drops out.

In a grid connected system you can easily use way more energy than your turbine can produce – it will just come out of the grid.

The generator of the wind turbine need to have the right output voltage for the grid tie inverter, so its worth having the inverter in advance and make the generator windings in a way to fit the Inverter’s needs. Also some over-voltage protection circuit is needed to save the inverter from high voltages caused by the turbine  in the case of failure.

It always makes sense to combine a small wind turbine with some photovoltaic panels (PV), because sun and wind are two resources which supplement each other very well. If there is a thunderstorm there won’t be sun but on a calm sunny day there might be no wind….

I will extend this article & write more about this topics soon.