Today we have learned a lot about the history of the Diever. But before we can dive into the story behind our most famous (but not most notorious) windmill we will cover an introduction about windmills in general.

In the lecture the rotor power coefficient (Cp) was touched upon and why some blade and rotor designs are more or less suitable for their designated purpose. Electricity generating windmills require less start-up torque to function and benefit from higher rotational speeds. This is why you see windmills with less blades that can utilise higher wind speeds. On the other hand water pumping windmills (WPW’s) require a much higher starting torque to lift the water column. Hence they employ more blades and a slower rotational speed, as you can see in the figure below.

Next we look into the shape of the blades. The most optimal blade shape is difficult to manufacture, so for budget friendly approaches, one is often limited to more simplistic designs. Such as the sails of the Crete or steel sheets based blades.

The goal of such water pumping windmill is to convert kinetic energy of the wind into gravitational energy by pumping a column of water up. This is possible by transmitting the rotational motion of the rotor to a vertical pumping motion. There are three main ways of transmission:

The most simple method involves a crankshaft. The crankshaft is connected to a wheel and the pumping rod as can be seen in the image below. A second method is using a four bar linkage. This method is most famously employed in pump-jacks, but is also very suitable for windmill transmittions. Finally, there is the pitman-arm transmittion. While this is a efficient aproach, the gears require lubrication and make the manufacturing and maintanance labor intensive.

Another important aspect of a windmill is the security. This is a mechanism that causes the windmill to turn out of the wind when it is storming and can also be subdivided into three main methods:

The first two methods use a helper vane that creates torque, such that the head of the windmill wants to turn. This is counteracted by the main vane that has more surface and thus keeps the head pointed towards the wind in normal conditions. One method is to add a spring to the main vane such that in stormy wheather it is pushed to the side and thus rotates the head out of the wind, this is used in the Oasis. Another method is to add a slanted mane vane/tail, such that pushing the tail to the side also requires it to be pushed upwards. With this design gravity replaces the role of the spring, this is used in the Kijito.

The last method is the tilting side-vane, which is used in both the Virya and the Diever on the WOT terrain. In this case the rotor is shifted sligthly off-axis (replacing the role of the helper vane). The main vane is also put off-axis to counteract the torque that is created by the rotor such that the head is turned into the wind direction. Is stormy weather the tail can tilt up, in this case the rotor wins the torque balance and turns the head out of the wind.

With this introduction in our heads we got into the developments that lead up to the newest version of the Diever in 2018. The story starts with another windmill that is designed at the WOT. The 12PU500 (a.k.a. Ghazipur) windmill was designed by Niek v.d. Ven and Willem Nijhof in 1979, when our association was in its first years. In this time period the Dutch goverment was willing to give subsidies in order to create water pumping windmills into an export product. With these subsidies and the TOOL foundation the 12PU500 windmill design got exported to multiple developing countries, there was even a factoy set up in Ghazipur, India. Eventually 3000 or more of these windmills were produced, but the project was seen as a total flop. Because a report came out stating that this windmill was too expensive and unreliable.

With this feedback Frans Brughuis drew up the first design of the 18PU450 (a.k.a. Diever) in 1987 at the WOT. These designs were published in 1990 and spread to developing countries, but we did not always hear back. With the information we did get back we figured that there are a couple dozens of Diever’s out there, mainly in Bolivia where a small setup was created that produced them.

But the development of the Diever did not end with this design. The first design had a slanted tail and a PVC pump. Later in 1993 the design was updated with a tilting side-vane and a brass pump. This design had an official opening with the former Dutch minister for Foreign Trade and Development Aid. In 2004 a new design was created with the four bar linkage transmission instead of the crankshaft in previous designs. In 2016 the head of the Diever on our terrain was replaced with the 2004 transmission and in 2018 the drawings of the new design were published. You can read more about the Diever and the reports on our website.

The technical report in 2018 included 3 versions:

• DA – a complete galvanisable version, without welds.
• DB – with the 2016 improvements, as built on the WOT terrain.
• DD – improved rotor and counterweight, this version was built in South Africa.

In 2018, the same year that the newest version was published, a South African farmer, Bennie, contacted us that he wanted to built a Diever windmill. So we sent him the drawings of the improved version (DD) and he got to work. When this version was built, some WOTters travelled to South Africa to watch it in its full glory. In the image below you can see the South African windmill with its four bar linkage pumping transmission.

There is another South African farmer that the WOT has cantact with and some WOTters have visited, namely Burgert Terblanche. He is called a water pump fanatic and has done several inventions. One of which is the HDPE pump, which can be more read about in this blogpost. The terrain of Burgert is full of small and large innovations on water pumps and windmills, such as a pumping rod with wood instead of a breakpin and the use of springs to dampen pumping strokes. He also thought of the “Forskop” that allows windmills to pump water up higher than their output. We also have some floating ball valves from him that we are testing on our terrain.

Hand drilling a well by hand is affordable, quick, and uses local resources. But in many areas, it’s not possible due to low water yield. A new method developed by Wolfgang Buchner addresses this issue, allowing hand-drilled wells to be installed in more locations.
Hand-drilled wells are usually small in diameter, which creates problems in soils that don’t allow water to flow easily, like clay or mica-rich soils. The small diameter limits the surface area through which water can enter, and the well’s filter screen often clogs with fine particles, leading to slow refilling; the well is pumped dry quickly.

In these soils, hand-dug wells have traditionally been used, as their larger diameter provides better flow. However, digging is a lot slower and dangerous work. Buchner’s method solves these issues and makes manual drilling feasible, even in challenging soils.
Here’s how it works: After drilling, a temporary casing—a pipe with large side slots and an open bottom—is installed. Water is pumped out, flushing fine particles that would otherwise clog the filter. Once the water runs clear, a permanent, slightly smaller casing with a filter is installed inside the temporary one. The temporary casing is then removed for reuse.

This approach cleans the surrounding soil of small particles and effectively increases the well’s diameter, combining the benefits of a small-diameter well with the water yield of a larger one. Best of both worlds!
To learn more about the method, have a look at the video:

Now that the winter has subsided, we decided it was time to turn on our solar shower again.
The system was turned on during the April working weekend, and two WOTters actually enjoyed a (still very cold) shower, a very welcome surprise after all the mud that was picked up at the other activities 🙃.

At an association night (Wednesday the 10th of April) we noticed two problems with the system.
-The water temperature was rising unexpectedly fast on Saturday and Sunday (for the sun intensity those days) and dropping too fast at nights.
-The pump failed to switch on on Monday and Tuesday. The system thinks it switched on the pump but the return-line temperature was not following the collector temperature. Which also meant the tank-temperature was not increasing on those days.So that Wednesday we checked the water level of the tank and sure enough the tank was almost empty, during dinner we let the tank fill up. And we used the bottom flush of the tank to try to flush some rust out of the system, which might have been blocking the pump.

We were hoping this would work, but during the following days, we noticed that the pump still was not switching on correctly. On some days it was (like Saturday the 12th of April), but on other days it was not. We can however see that the tank now heats up and cools down slower than it did when it was not completely filled.

Here you can find a graph displaying the data that is measured live from the solar shower system. This graph shows the temperatures of various sensors and the time the pump was on for every 10 minutes.
-The pink line shows how long the pump was on, the pump cycles on automatically when the collector temperature is higher than the tank temperature.
-The dark-blue line shows the temperature of the collectors, it quickly rises if the sun is shining.
-The red line shows the temperature of the water flowing out of the collectors and into the tank.
(This means it follows the collector temperature while the pump is on but the temperature quickly drops towards ambient once the pump has shut off)
-The light-blue and yellow line show the actual water temperatures in the isolated storage vat this is the water that is used to heat the shower water through a heat exchanger.

On Monday the 14th of April we flushed more rust out of the pump, this time by actually manually disconnecting the pump and running it with some clean water. This did not seem to work, because on the 18th the pump was jammed. On the 23th a small hole was found in a pipe and had been welded shut, this explains why the tank was as good as empty during the working weekend. The pump was replaced with another one on the 24th and this seemed to have helped, because the pump has been functioning every day up to the day of writing (the 3th of May). Since the 29th of May the days kept getting warmer and on the 1th of May the tank was at a temperature of 45°C and someone had a nice and warm shower 😊.

It’s Christmas time! Like many buildings, the WOT site got a makeover too last week. Thousands of Christmas lights bring magic to the place.
No doubt about it: all lights are LED’s!

It’s worth watching it, especially in snow.