From 23rd-29th April 2016 i hosted a workshop here at Scoraig.
Seven “students”. Co-instructor Jonathan from Austria.
Project was 2.4m diameter 24-V battery charging turbine from the Recipe Book. See also the pdf guide to welding this machine. Mostly it was pretty standard, but we did a new magnet rotor mould design with wood-screws that adjust the height of the disk within the casting. This was the result of a group brainstorm session.
Get hands-on experience and learn transferable skills in welding, wood carving, and working with magnets & resin
Learn how to build and install a Hugh Piggott wind turbine from scratch using basic materials
Experienced tutors who have been running courses building Piggott turbines since 2007
A practical fun course for all experience levels
On the course we collectively build a 1.8m diameter Hugh Piggott wind turbine. All the participants spend time working on each of the three main parts of the build (wood, metal, and electronics) rotating through the different bases on the first day. On the second day we then come together as a group to assemble the machine.
V3 Power is a workers cooperative based in Nottingham. The turbine is a robust design that can be easily repaired, maintained and serviced and is an excellent example of appropriate technology.
Adriaan Kragten has been kind enough to notify me of his latest design work which is documented in his free pdf reports available for download here. Most of his wind turbines have been based on converting induction motors to pm alternators in the past Now he is designing axial flux ones with similar geometry to mine. But the designs are largely untested.
Here is a drawing from report KD571 which is about an alternator for a 1.36 m diameter turbine. Maximum output would be about 80 watts at 670 rpm with alternator efficiency below 40%:
This is a single-rotor machine with a steel disk behind the coils that has rather high iron losses due to eddy currents. My personal view is that although this is easier to construct the loss of efficiency is unacceptable. There are also rather high loads on the bearings. I would prefer a spinning steel disk behind the coils (as in my 1800 mm diameter design in the Recipe Book). But in principle this design will work and deliver useful output.
Adriaan has gone on the design a larger version in KD596, using 12 magnets (but at lower rpm) to achieve 50% higher power output with similar efficiency. He speculates that it might be worth overlapping the coils to obtain better usage of the space. I have seen this down a couple of times with axial flux alternators using specially designed presses etc and it can offer slight improvements in efficiency.
So Adriaan is looking for somebody to test this idea and others, most likely as an electrical engineering project. I suspect that he would be a helpful mentor, and much would be learned.
Finally I’d like to say mention a couple of pitfalls that engineering students tend to fall into. One is that you do not want to test this with a resistive load. Test it with a rectifier and a battery for realistic results. Second is do not worry about Hz or try to obtain a 50 Hz sine wave output. That is not relevant for small systems where the output is going to be converted to DC. Finally please do not use a vertical axis blade design for the turbine. For some reason everyone wants to do this, and it is a huge mistake.
Ian Woofenden has decades of experience living off-grid and teaching workshops.
Renewable Energy for the Developing World
Costa Rica – April 2-10, 2016
This workshop provides an introduction to all the major renewable energy technologies with a focus on designing and installing small, rural systems. We’ll get our hands dirty — the majority of the workshop is hands-on field work, and it also includes classroom sessions and the following projects: 1) building and using solar ovens, 2) a solar hot water or solar-electric system, and 3) installing a methane biodigestor. This is an experiential program, with a non-technical, overview focus. These hands-on installations give participants the opportunity to interact with local members of the community, experience both the challenges and satisfaction of working within the developing world, and the opportunity to install systems that can dramatically improve the living conditions of the local people. …read more
Between 2012 and 2014 Jon Sumanik-Learyand I did some performance measurements on wind turbines here at Scoraig, using Logic Energy mobile logging systems. Jon has finally completed the processing of the results and sent me some exciting curves.
Wind Empowerment have been contracted by the Scottish Government to carry out a market assessment for small wind turbines in Malawi in partnership with Community Energy Malawi. This will be carried out between December 2015 and March 2016 and will involve a week long training and planning session in Malawi with Community Energy Malawi staff. The project will be lead by Aran Eales and Jon Sumanik-Leary, who are looking looking to recruit two further research assistants/instructors to assist with the design and delivery of this research project.
A proposal containing further information about the project can be found here.
Please send any questions relating to this opportunity to firstname.lastname@example.org. To apply, please send a CV and covering letter to the same address by midnight UK time (GMT) on Monday 14th December.
If you’d like a homebuilt wind turbine but can’t find time to build one then you might consider adopting one built in a workshop course? V3Power are offering several wind turbines and parts on this basis here.
I am planning to hold a course here on Scoraig in April. We’ll build and test a wind turbine as usual. Accommodation is provided from Saturday 23rd to Saturday 30th April 2016. These will be the arrival and departure days. The course will run for six days from 24th to 29th. Your partner may be able to find accommodation here too without attending the workshop. Please ask for details.
Contact me for more details and to book a place. I do not plan to travel around teaching courses any more as I already did that for 12 years or so. This may be your only opportunity to be taught by me personally, although there are several other groups worldwide offering courses based on my Recipe Book or derivatives of it.
I don’t write enough about what goes on here at home on Scoraig so here is a run down on where my electricity comes from. I have two windmills and a collection of solar PV panels. 800 Ah Rolls 4000-series battery and 48 V and two Outback VFX 3 kW inverters.
5.3 metre diameter
3.6 metre diameter
2.5 kWp of solar PV
Big one Power curve
Big one heat v charge
The big windmill charges the 48 V battery via a couple of heaters in series. We get very little heat in low winds but almost all of the power goes to battery charging with very low cut-in around 60 rpm. As the current increases to (say) 20 A we get about 1000 W to the battery and 300 W of heat. When it reaches 40 A we get 2400 W at the battery (assuming 60V) and 1200 W of heat. The heat (combined with waste heat from cooking) is sufficient for our well insulated house most of the time. I prefer the windmill should not go a lot higher output than that, but it’s turbulent site in NW gales so we do see much higher surge outputs and there is trip that brings in extra heaters as a braking load when the voltage reaches 140 V (7.5 kW). I had a bad accident with this windmill (tower buckling) in a bad storm last January, and nowadays it is governed to about 1 kW average into the battery. It looks lazy but it does all we need.
The smaller windmill is an AWP from Zimbabwe but the blades are locally made from wood. It runs through an MPPT controller (I have tested both Classic and Tristar) that enhances the peak output to about 1500 watts.
The Solar array consists of 4 strings (pairs) of big 240 Wp 30 V modules and 2 strings (fours) of little 80 Wp 17 V modules totalling about 2.5 kWp. These feed into the battery, and surplus power (wind and solar) is dumped to hot water using a Tristar PWM diversion load controller. When the water tank is hot, the excess power is diverted to AC heating loads using a phase control SSR. We also have some evacuated tubes for hot water.
Electricity consumption is running at about 6500 kWh per year. (The UK domestic average is 4200 but I also run my business and the extended family house next door). We do most of our cooking with electricity, using a kettle, toaster, microwave, induction hob and halogen oven. We also recently replaced the gas oven with a big electric oven.
When the wind stops and there is not much sunlight the batteries get a bit of a fright, and I have to fire up a diesel generator. This has run for an average of 150 hours per year over the last two years, feeding about 2-3 kW of power into the system.