Here’s the latest update from October — our efforts since the last update has been mainly around the electronics. We’ve discovered a few issues, that we believe to have solved now.
We’re waiting for the next batch of electronics to arrive, which we hope will be next week — then we need to to verify, and then shipping efforts should begin!
This update is a little later than usual; we wanted to have a solution for the electronics done before we’d be ready to push this update.
Challenges with the DC/DC ground converter; we need to verify our solution
We have had a range of issue with the DC/DC converter. That we discovered through testing field testing of our equipment doing the past few months.
The main functionality works great! However, we had minor issues around boot-ups and how it works in cases with low battery and other small issues that would not happen always, but will happen sometimes. It’s something we initially overlooked.
Here’s how it works:
The ground DC/DC converter steps down the voltage from the wind turbine (40V) to a voltage that can be used to charge batteries either directly or through a MPPT. One important feature of the DC/DC converter is the ability to pre-charge super-capacitors that’s used to stabilize the turbine voltage. Once those are charged, the pre-charging is used to power the servo motors that turn the blades to start the turbine.
The DC/DC step down functionality has been working flawlessly (since the early tests of the fully assembled prototype in early June)
Hacky setup, running both 12V and 39V into the DC-DC unit
Here we are testing two converters connected to turbines side by side to see the effect of white surface color on the temperature inside the DC/DC converter.
Issues from our own inhouse tests:
- Sometimes the system wouldn’t reboot after it has been turned off.
- Sometimes the pre-charge system wouldn’t be able to deliver enough power to the system to sufficiently power the microcontrollers and steppers needed to activate the system.
- The pre-charge system might draw too much current, meaning the power source (usually a portable power station) might shut off 12V supply).
How we’ve solved them:
- We designed a latching circuit that will fully turn off the microcontroller when sufficient energy is available. This means the controller is never in a state of partially powered on.
- We redesigned the pre-charge circuit to use on the of already existing power MOSFETS in the circuit to work as a linear regulator doing startup. This means the power loss is very low when the system is fully on and we can control the inrush current fairly accurately.
- Solution 2 also solves problem 3.
Example of the inrush current is seen on the oscilloscope below. The purple is the gate voltage and the yellow graph is the current. This is one of the first test that showed the principle working.
We have for the past week been running a complete off-grid setup at our test facility at Risø. We are in fact using two of our DC/DC converters to test the upgraded electronics. One received input from the solar panel and one from the turbine.
As a load we use our on-site server, anemometer, 4G router and video surveillance equipment.
Complete offgrid setup — we’re running solar to be able to boot up the turbine and electronics in case of a complete flat battery.
So far the system has been working flawlessly. The system is able to recover from a completely drained battery using the solar panel — enough for the turbine to start soon after.
5 Turbines ready for shipment
We’ve manage to pack, verify and test 5 turbines. They are sitting on our shelves waiting for the updated electronics ground station, and then we should be able to ship! Fingers crossed!
At the moment we’re not producing turbines, as we’re waiting for the electronics, but efforts will start again as we verify. We should be able to do 3 turbines per week, and then scale it up to 9/week shortly after.
We still want to test everything that we make in-house for a short time, before we’re ready to ship it out.
We’re preparing for electromagnetic compatibility (EMC) testing, when we’re and happy with the electronics. This is required when we’re selling the turbines.
We’ve begun initial efforts efforts for the test stand, and should be able to push this further once we get the electronics and we’re happy with everything.
Here’s a boom mounted with an air motor. We need to use an air motor, as we cannot but other motors into the magnetic chamber for the tests.
Continuing to clock in hours
From the last updates we’ve been able to run turbines continuously. Last update we mentioned a failure in the way we had attached the lines. The attachment allowed them to grind up against each other, eventually leading to a failure. At that point we had 50 days of continuous run time. This failure was the 31th of August — We’ve solved this issue and we’ve still not had a failure on that particular turbine (which is our “oldest”, the one that has done the most hours). We’re now up to 48 days again as of the writing of this post, so apart from the replaced lines, we’re almost up to 100 days of continues runtime.
The other day we also logged our most extreme gust yet — 19.5 m/s (43.6 mph). There was no troubles there.
The figure under here is our cumulative hours. You can really see the time in May when we managed to solve the passive pitch-up safety for the turbines. We’ve been able to log many more hours since then.
Cumulative operational hours — note it’s only for logged data, sometimes we’ve a bit of data. Also sometime we’ve had more than a single turbines, so this is ALL the data and hours that we’ve gathered.
We’ve begun fundraising as well, we’re now at a stage we’re the product is almost ready, and we’re soon to have the first deliveries. The next step for KiteX is to begin selling turbines again — you backers will receive your turbines first of course, but internally we’ve started dedicating time to fundraise a pre-seed round.
We need to raise money to scale our production and also sales efforts. We’re also quite excited about the possibility of scaling up Wind Catcher to a size that can be used residentially.
If you want to know more, let us now in the comments below — otherwise you can follow along on our LinkedIn to see the posts there.
This is how a bigger version of our concept could look like. Compared to a conventional type of the same rotor area, our design is 80% lighter, and has 4x better payback time.
Vibrations vibrations vibrations
At the moment we’re also pursuing efforts to mitigate vibrations.
The turbine sometimes “shakes” a bit for a few seconds, excited by natural frequencies. It does not damage the turbine. BUT it makes a rattling sound as the cable inside the tower hits the inside of the tubing, and it does not look good.
We’ve prototyped a solution of a foam liner inside the tower that seems promising — it eliminates the sound; however it does required a hinging mid tower node, as the cable needs to be installed more permanently inside the tower. It’s still possible to take it in/out, but it requires some effort to not damage/get stuck in the liner.
We still want to minimize vibrations for the visuals, so we’ve done and are still doing tests to understand the system better. It requires a lot of testing revolving different anchor set-up and and different line types. It is a lot of experiments and analysis.
Lastly we’re a little worried that too much shaking is a hazard for the ground anchor installment. We’ve not seen it rattle out, but we have not tested, and does not have the ability to test, in many types of soil.
We’ll dive more into this in the next update — it’s still ongoing.
Lastly; stuff that we’re working on:
Until next update we’re working on a few more things;
- The interface on the ground DCDC unit (how data is presented on the screen and how you -the user- will interact with it
- The App, how the turbine is controlled
- Automatic throttling; having the turbine to automatically throttle based on how much energy it can deliver
- Vibrations in tower — as mentioned above
- User guide; a writing/illustrative guide for using the turbine (set-up, usage etc.) And also a video explaining a quick guide, and also an in-depth video overview/guide on how to use everything.
That’s all for now, PLEASE write in the comments down below here on Medium, or in the kickstarter comments! We’d love to hear from you!
May you have good winds!
The KiteX Team