Wednesday, February 15, 2017

bad system drive

Without warning, the C: drive of my main computer quit a couple of days ago.

I was able to keep working on a backup machine which is physically the same as the main computer but without all the software.

Fortunately most of my work was on another drive which I backup regularly. I seem to have lost my sent mail however. My mail program data was on the failed drive. I should be able to retrieve my sent mail from my mail server? More learning.

I did not have a current backup to restore from. I have reloaded Windows 10 on a brand new C: drive, an upgrade from the failed 750MB to a new Seagate Barracuda 2TB.

The reload experience with Windows 10 was interesting. I had made a Windows 10 recovery disk (the CD in the picture) back in December and it did boot the amchine into Windows 10. It did offer to restore from a backup, if I only had one.

So I had to reload Windows 10 using the Microsoft Windows 10 Media Creation Tool. This makes an installer on a USB drive, a fresh copy of Windows 10 from the source and it automatically licenses somehow from my Microsoft ID.

Now I am reloading my programs: Adobe, Corel, LibreOffice, Thunderbird, Chrome etc and all their helper plug-ins. Apps in new speak.

Don't think this can't happen to you. Have a backup.

One piece of learning was that I had S.M.A.R.T. reporting turned off in the motherboard BIOS.The drive may have been trying to let me know there was a problem but I was not allowing it.

That system did seem to be taking a long time to boot and there was an occasional cryptic memory error message from Windows that I have captured somewhere. Also Windows Backup was nagging me that it had not completed (for some time now).

So maintenance was overdue, perhaps a system swap, test backup. I had the hardware but just had done none of those things.

The failed drive starts. I can hear and feel it start in my hand. The disk is turning, a few clicks and then it just spins. But it is not recognized on any of the live SATA ports I have tried it on. Maybe I can swap the circuit board if I can find another like mine. (click the picture to read the lable)

I had written about having twos of things.

George Plhak
Lion's Head, Ontario, Canada

Wednesday, January 25, 2017

fresnel lens 3

Video from about Fresnel lenses. He discusses the question of which side of the lens should face the sun.

From about 2:20 to 4:50, he measures the focal length of his lens in both orientations. His is the same 32 inches both ways. He then does a heat gain test with both orientations (to 6:10) and finds that with the grooved side facing the sun, he gets significantly more heat. His test is to heat 150 ml of water by 20F degrees at the focal point and measure the time in minutes. Shorter time indicates better heating.

Grooves facing sun: 1:55 (one minute, 55 seconds)
Flat side facing sun: 4:40

He provides an explanation of why this effect occurs - spherical aberration. He goes on to explain the difference between a linear and a spot lens from 8:00.

A very interesting site is Have a look around at some of the other impressive work shown there.

I found this interesting at NTKJ Co., Ltd. (Nihon Tokushu Kogaku Jushi) Fresnel lens supplier: an illustration showing the orientation of their Fresnel lens for solar concentrator with the statement: "Our standard fresnel lenses can also be used for the same purposes but with the opposite facing design. Namely its plano side faces focus and the fresnel surface faces parallel light source."

Perhaps this applies only to NTKJ lenses?

Their website is a useful catalog of different types of commercially available Fresnel lenses. I don't know if this company manufactured either of my Fresnel lenses.

The Green Power Science store is a source of Fresnel lenses of different sizes and types.

A video description of my temporary optical test bench used for measuring focal length of Fresnel lenses.

I was able to show myself that both of the lenses I have (your mileage may vary) focus much more precisely if the parallel light enters the lens on the Fresnel side but this not always have to be the case hence you might consider testing your lenses in a similar manner?

Finally, I notice that many who work with Fresnel lenses tend to use stands similar to those in the picture.

It is easy to understand why this is the most common approach. You need a rigid frame around the lens to keep it straight and what better way to add a pivot than at the center point of the frame?

I would imagine that the movement of the sun over time and the wind would make the this type of stand problematic.

This is a sketch of my stand concept. Imagine two cylinders, one inside the other. The Fresnel lens would be in a frame but the frame would have arms which are pivoted at each side of the work surface on the outer cylinder. Each arm would carry an adjustable counterbalance. The length of the arms would be so that the focal point would always land on the work table (the top of the inner cylinder) with the lens pivoting around it in two axes (#1 and #4). These axes could potentially be motorized with tracking added later.

The other degrees of freedom are #2 which allows the work table to rotate so different sides of the work could face the sun and #3 allows the work table to be raised and lowered, moving the work vertically in the focus.

Sorry if that is not more clear but it is only a concept that I hope to refine as I build something.

For now, I need the benches free so I must finish with these focal length measurements.

Thank you for your interest.

George Plhak
Lion's Head, Ontario, Canada

Monday, January 23, 2017

interesting diy solar concentrators

I have been watching the progress of сергей юрко on YouTube with his very interesting solar trough project.

сергей юрко is Sergey Briskly according to Google Translate. He describes himself as "Sergey, Mirgorod, Poltava region" (Ukraine) and gives his phone number in the video description on YouTube. He has a series of videos in which he describes the construction method and progress of his split trough solar concentrator, intended for heat capture and electricity production. His videos I've watched so far show the progress of what is now a rather large array.

I am using Google Translate to understand what I can.

In this latest video, Sergey walks the viewer through the array and the process of building from ordinary building materials with ordinary tools. He even shows the fasteners he is using.

The reflectors are an interesting split design. He is located at almost 50N latitude so for winter use, his array would point fairly low in the sky.

Since the array does not seem to have provision for tracking, Sergey has probably oriented the array east-west with seasonality adjustment on the back legs of the frame (where the yellow back leg joins the blue)? The bottoms of the ribs are hinged where they meet the ground support so the array "tilt" can be adjusted to better match the season.

The construction of the collector assembly, with insulation and multiple copper collector tubes is interesting. Although glass wool insulation decouples the collectors from some wind and thermal loss from the front, it does nothing to decouple the collectors from heat loss to the ambient air. It should be possible although more complex to use insulated glass tubes in the design.

Sergey presents numerous charts in Russian text. I would love to understand more about his work. This latest video is from last week and fairly complete (31 minutes). I encourage you to look at his work. I have not yet had any correspondence with Sergey.

Sergey: you will have a wider audience if you edit the automatic transcription of YouTube CC (closed caption) text on the video so viewers better understand your narration in other languages, like English. The default transcription (voice recognition) is not very good and gives poor language translation results.

I heard recently from Ebrahim Hashemi in Shiraz, Iran.

I am Ebrahim Hashemi, from Shiraz, Iran and I have invented the new method of ‘fixed-focus solar concentrators’ which is a unique method of using solar parabolic dishes.
Now, please introduce my website to all individuals interested in the solar energy.
it is my site:
Respectfully yours

I found it interesting that Ebrahim is keeping the center of rotation of the dish the same as the focal point. This is essentially what I have done with my parabolic trough. It makes the tracking mechanism simpler. I did ask him how he accomplishes the bearing on the back of the dish.

Some ideas from the internet for your inspiration.

Thank you for your interest,

George Plhak
Lions Head, Ontario, Canada