Tuesday, December 12, 2017

india one drone video

Sharing this wonderful aerial view of the India One solar concentrator.

India one - Solar Thermal Power Plant from Freysteinn on Vimeo.

The application is a solar thermal power plant at an institution, Brahma Kumaris.

There is 16 hours of heat storage at the focus of each concentrated beam and all are joined, all 700+. The reflectors are made on-site.

For your interest.


Another video shows construction.

Friday, December 01, 2017

refrigerator 5

INDEX to the series

I have a new refrigerator! Actually, a friend's three year old model since she was wanting to upgrade. I feel like it is a new fridge (new to me!)

It is like new clean, full of food, and has been working steadily (and hopefully efficiently!) for the last two weeks. It is quiet and seems to be using less energy.

We had some concern as we had to lay the fridge on its back for the short ride here (about 5km) but I let it sit overnight before plugging it in. There is lots written on the web about this question of how to safely transport a refrigerator.

Mine did trip out after reaching temperature and the temperature inside rose for several hours but it came back on by itself and rapidly got to the prescribed temperatures (about zero F for the freezer and about 40F for the refrigerator.) The control (actually there is only one!) is at mid point. I have big clunky heavy mechanical industrial thermometers that I know to be accurate inside each compartment.

Readers will know that I had been controlling the old fridge use of peak power with a timer. Basically the fridge was OFF during peak power billing periods. The fridge would come ON at the end of peak power.

Even with the old fridge, I was able to cruise through the hottest summer day without loosing any ice cream. I was surprised given the condition at the bottom of the old fridge door seal which was torn but not really visible until it got moved out.

With the old fridge, I had done an experiment to add insulation to the outside of the freezer compartment of the old fridge. The added insulation did not make as much of a difference as I had hoped. The graph is a quick look at the data for fridge performance with changing ambient temperature. The blue dots are the insulated fridge, the red dots are with insulation removed (on July 13). I would have expected two parallel best fit lines. I did not plot the best fit for the red. I don't think I have enough data for the uninsulated case but all the red dots clearly land to the left of the blue dot cluster so there was a difference, just not as much as I had hoped.

I will have to wait until the furnace is no longer required next Spring to gather date using the same method but I added a plug in energy meter to the fridge so I will have another way to know the energy use.

On Aug 1, I had installed a plug-in power meter in line with the fridge timer. So I have two plug in devices in line with my refrigerator. One to measure (the first one in the wall) and another to control run time. I also have the same two devices in line with the freezer. I have been reading and then resetting the power meters at the beginning of each month.

So today I got my first look at a comparison. There was no fridge at that outlet for three days and then the new fridge took over about Nov 10. I am pleased to see that the very first reading of energy used with the new fridge was about one third of the months previous. That is probably optimistic. The freezer also seems to have done better this month compared to the previous three. The ambient temperature of both the basement and the main floor has dropped significantly with November now hovering around 15-20C rather than 20-25C of October which was a warm month.

Fridge40394014*16 << GOOD NEWS!

* Updated Jan 1: The November number for the fridge is mixed data. The first week is the old fridge. When the new fridge arrived, it was off for three days. The old fridge ran on another outlet until food was transferred and the old was unplugged. The new fridge usage was the balance of November from Nov 10.

That the new fridge uses MUCH less energy, LESS THAN HALF is shown with the December usage which was entirely on the new fridge.

This is a comparison of the old and new ENERGUIDE labels (the new is on the right) The new fridge is almost half the usage of the old. Close enough and nice to have this confirmed with my own data. The new fridge should make a big difference to lower my kWh use. The freezer has now become my highest usage refrigeration and my next target.

Thanks for your interest,

George Plhak
Lion's Head, Ontario, Canada

INDEX to the series

Wednesday, November 22, 2017

radon testing

Radon is a naturally occurring radioactive gas that may accumulate in a home. Radon is colourless and odourless; it can enter a home anywhere there is contact with the ground, such as basements. Testing is the only way to know if it is present. 

I have begun two long term radon gas tests in the basement of my old house. Radon gas in a dwelling or at work is a possibility in most parts of Canada and the US. We should test for radon in the places we spend the most time ie have the most exposure.

There are excellent web references and tons to read. I have never done a test for Radon.

I was excited to have a "free" kit offered by local Grey Bruce Public Health. I also purchased a long term test kit (SKU 3616930 $43 with tax + $40 analysis report fee in six months) from Scott's Home Hardware to compare. My plan is to run both tests for six months (from today will be May 21 2018).

I have had most concern about where to place the test modules for the duration of the test. The kits and online info provide guidance. But if I followed it all, in my case, there would to be no place better than the middle of my living room on the main floor except it is adjacent to the kitchen which is a no-no. According to most instructions, I am to test in the lowest "lived-in" room in the house. A basement if it is finished and someone spends some amount of time down there.

I am probably erring on the side of excessive caution but I'd rather know if the room was safe BEFORE I put someone's living quarters down there. Unfinished and probably will never be except perhaps for some insulation. There is still a chance of a "water event" in my basement although things have been improved and it has been pretty dry down there the last couple of years. I wanted a worst case type of reading.

Other negatives, I am not to test in a furnace room although the furnace is across the room. I am to be away from walls and floors.  I built the little test stand to keep the modules safe and dry, about 2 foot off the concrete floor sitting under the open stair well.

Today I cut open the sealed bags. Both modules look the same, a black top hat module about 3cm in diameter with identical markings (but different numbers) just like they had been made in the same factory. Same air desiccant bag inside the plastic.

The one from the Public Health comes with paperwork from AccuStar Canada (with address POB Cap-Rouge Office Quebec. There is a plastic bag and a postage paid return envelop addressed from the Cap-Rouge Office to ACCUSTAR LAB 11 AWL STREET POB 158 MEDWAY, MA. I am supposed to mail the Public Health module together with the completed AccuStar Datasheet in this envelop. No additional charges mentioned. There is a statement in their instructions which states that test devices must be sent to the US address, not AccuStar Canada.

AccuStar calls the test "Long Term Radon Test Kit for Radon in Air (Alpha Track)". I had read that I could not measure for the presence of radon with a Geiger type counter since the radiation is alpha which is not detected by a Geiger tube. I need an alpha transparent window, like a mica window to make an active detector.

Passive radon detectors like these rely on a small piece of sensitized plastic film. It has to go back to a lab for reading. A one shot device. Time is a key input to determine an exposure range. These long term detectors should be exposed 90 days to one year and the exact period recorded on the datasheet.

The Public Health package includes a booklet "Radon: A Guide for Canadian Homeowners". Good basic information. I notice that you can get a pdf copy here if you submit your email.

The package from Home Hardware, a Pro-Lab "Long-Term Radon Gas Test Kit, product number RL116 contained an envelope made out to Pro-Lab with address in Woodbridge, Ontario, a short "information sheet" to be filled in and on the other side instructions. The standard Lab results are obtained by sending back the detector and test info sheet together with check or money order for C$40. They also take Visa, MaterCard, AMEX or Discovery cards. A phone number is given.

So now we wait for six months...

added june 27 2018: radon testing 2 - my results are in!

Thanks for your interest.
George Plhak
Lions Head, Ontario, Canada

Radon Cancer infographic
Radon - Canada.ca.
US EPA on radon

Saturday, May 06, 2017

heat 3

INDEX to the series

(click graph to enlarge)

It has been interesting to record how hard my furnace works as the outside temperature changes. The points are observations of the running time of the furnace and how often it comes on taken first thing in the morning from my smart meter compared to the outside temperature. The process takes about the same time as a morning cup of coffee to record one point. The graph fills in as I add more points but I can already clearly see the trend (the line).

I divide the run time by the time between cycles to get a fraction (and then a percentage) which I've called the Duty Cycle. This is how much of the time the furnace runs. The colder it gets outside, the more the furnace runs, using electricity and oil in my case to generate heat for the house.

As an example, here is the smart meter graph from this morning with some measurements I have made from the graph.

Being overnight, the only things going on in the house electrically (other than the base load) are the furnace (the peaks that I have put dimensions on), the refrigerator and the freezer. The fridge and freezer are the "choppiness" in the graph. They use much less electricity than the furnace.

I can pick them out with difficulty but I don't need to since I am only interested in when the furnace is running. The water heater is also "running" but it does not appear in this section of chart because it cycles over a much longer time (six to twelve hours) so it does not show up in this time period from about 1:30am to 6am. So the furnace is relatively easy to measure.

The dimension lines I add to a screen capture with a drafting tool (CorelDraw). The dimensions are cm which I convert to time by noting the length of an hour on the graph bottom scale. The top set of numbers is the furnace run time, the middle set is the time between runs (the cycle time) and the bottom number I use to convert centimeters to time.

Here is the calculation for this morning's data point at 4 degrees C. The spreadsheet is here.

Since I don't have smart meter data from last year I can't compare historically like I could with degree days. Next year I should be able to see the effect of improvements to insulation for example. When I get a new, more efficient furnace I should be able to see a difference in this chart.

"You can't manage what you don't measure" - Peter Drucker

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

INDEX to the series

Sunday, April 30, 2017

heating degree days 2

INDEX to the series

(click graph to enlarge)

This graph shows my progress at using less electricity for heat.

The blue line is the 2016-2017 heating season. The blue line is lower than the others and slopes less. The graph tells me that I used less electricity per heating degree day last year than the previous three years.

Although I heat with an oil burning furnace, a fair amount of electricity gets used to power the two motors in the furnace, about 600 watts while it runs. If it runs less often, it uses less kWh.

The graph was simple to make and only requires two numbers for each month. One number, the total kWh used, is from my electricity bill. The second number is the heating degree days for that same month that the electricity was used from a government site like the one I showed in the previous article. A copy of my spreadsheet (.xls) is here.

I made a number of improvements in the house to reduce heat loss but particularly last summer (new insulation, leaks plugged, air circulation cut from the sun room and a new door) so it is good to be able to show the improvement in spite of changing weather.

I am ignoring price here and focusing only on the kWh used and the outside temperature as expressed in the heating degree days for my location.

Last winter was not as cold as the previous three but that does not matter when the data is compared as kWh per heating degree day.

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

INDEX to the series

Saturday, April 29, 2017

heating degree days

INDEX to the series

(click graph to enlarge)

In order to compare my energy costs for different periods I am looking at the "heating degree days" for the nearest weather station Tobermory.

The graph confirms my memory of the last few winters. Certainly this past winter was NOT AS COLD as the previous three. I need to keep this in mind before I go patting myself on the back for energy reduction this past year as I have worked on this project.

I am midway between Tobermory and Wiarton. The data for other locations in Canada are available at weatherstats.ca. I thought Tobermory might be slightly more pessimistic data since it is further north and indeed as I compare month by month for last year, Tobermory is usually, but not always colder than Wiarton (higher degree days for the month).

The data is available monthly as well as quarterly.

Heating Degree Days are similar but different from Growing Degree Days (for agriculture) or Cooling Degree Days (for air conditioning).

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

INDEX to the series

Friday, April 21, 2017

the new water heater

INDEX to the series

(click graph to enlarge)

I had previously determined that my hot water heater was one of my top five largest electricity uses.

So I recently replaced my old electric water heater with a new electric heater of the same type, but 23 years newer. I now have data which shows less electricity to keep my water hot than before. The red line is the new water heater, the blue is the old.

I didn't get anything special. Mine is a GSW (AO Smith) base model but I will treat it with a bit of extra insulation. Even without the insulation I will add, so far I can see that the new heater has better insulation than did the old heater from 1994. It is ON less often.

The graph shows the percentage of the time that the water heater is ON. The new heater has the same standard 3000 watt heaters as did the old so it uses the same amount of energy when it is ON. The difference is that it is not ON as much as the old heater as shown by the %.

I am measuring the duty cycle % in the same manner that I did in the old water heater article then plotting the data points as I make them. The red regression line of the new heater data should grow towards the right as the temperature in the basement gradually rises with the coming summer.

A water heater will work harder when the surrounding air cools (lower ambient temperature). My water heater is in the basement near the furnace which causes the temperature in the basement to vary by a few degrees as the furnace goes through its cycle so I have a fair amount of scatter in the data points the more the furnace runs.

Here is the new water heater on a sort of pedestal that I made from wood and 1-1/2 inch Styrofoam sheet that I hot wire cut to a disc shape to sit between the heater and the wooden base.

The old heater was sitting directly on the cold concrete floor. The base and insulation will help reduce heat loss through the bottom of the heater.

I plan to wrap the heater with a blanket layer of insulation. I have another circular disc to close the top.

Both the new and the old set points are the same, the recommended 60C / 140 degrees F to prevent bacterial growth. The new water heater is also controlled with an electronic timer to prevent it from operating during peak rate periods.

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

INDEX to the series

Tuesday, April 18, 2017

reader questions - concentrator versus flat plate

Re article Summary/Conclusion - DIY Flat Plate vs. Concentrator Performance

On 4/17/2017 8:29 PM, Paul Arnold wrote:
> Hi. I came across your website via builditsolar.com and was interested in your comparison of the flat plate collector vs concentrator. You don't mention cost and ease of construction factors. Could you say which is cheaper to build on average? You built both. Which would you say would be easier to construct? What about speed of construction when attempting to build a large array?
> I am also intrigued by the idea of running a steam engine with your concentrators. Would you be able to guess the cost comparison per watt of useful energy with solar panels? I'm assuming you would capture the exhaust from the steam engine for space and water heating so it might be close. I'd love to hear your thoughts on this.
> -Paul Arnold

Hi Paul. Thanks for your interest and your good questions.

Originally I built a concentrating pool heater array which was un-insulated. It worked well for that application for five years (until I had to move and I took it down).

In that situation, I thought the concentrator was less expensive than flat plate although more complex, especially since I would be doing it for the first time. I could not find a suitable design for a concentrator so had to come up with a design myself. (This resulted in my first book "How to Build ...").

For pool heating, I was trying to heat a huge quantity of water by only a few degrees which the concentrator did admirably. Insulation was not required for the pool heater application, so lower cost.

I continued to work on a set of improvements which I called Gen2 which is an insulated version. This second version of the concentrator with the insulated collector (The Home Experimentor's Manual) would be more expensive. The added insulation (primarily the glass evacuated tubes) would not be required for a pool heater but made possible higher temperatures and higher latitude use in winter.

I publish cost estimates for both my parabolic designs although these are only for guidance. Your approach may differ from mine. See Bill of Materials here.

The cost of building a flat plate will depend on the design and materials you use. Whether it will be insulated, for example. You will find many versions and Gary's recommendations at his site builditsolar.com. Determine your cost of making a flat plate after you decide on your favored approach for your application.

About making electricity from steam, I am not currently pursuing this nor do I know anyone who has demonstrated a durable, safe, long term approach. Since the price of PV solar panels has plunged over the past ten years, it seems that interest in doing the alternative, with solar generated steam and some sort of turbine/generator, has faded. Are you clear that you cannot make steam with a flat plate? You need a concentrator for that. The two are not interchangable.

Best of luck with your efforts. Let me know if you build something that works for you. If trying steam, be SAFE!


George Plhak

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 rimstar.org 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 rimstar.org. 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

fresnel lens reading list
fresnel lens
fresnel lens 2
fresnel lens 3 (this article)

AND Use of fresnel lens for 3D solar printing.

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.

The array does not have provision for tracking. Sergey has 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: http://fixedfocus.ir/viewpage.php?page_id=2
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

Thursday, January 19, 2017

fresnel lens 2

I had written in fresnel lens about wanting to determine the focal length of a large Fresnel lens removed from an old rear projection television. I want to know the focal length to design a mount to aim the lens at a fire-proof adjustable work table in a safe manner.

I am using laser pointers to see where the light beam is bent. I have a measurement for each lens but I am confused about which side of the lens to point toward the sun. I am seeing an unusual effect that I wanted to explore further.

The simple test setup I was using showed me that I was on the right track but I realized that I could improve the setup to make the measurement more accurate and repeatable.

This is a picture (click to enlarge) of my temporary wood shop optical bench setup. There is one Fresnel lens lying flat on the left table. You can see the circular rings. The other is hanging vertically between the two tables. I have made some improvements which I'd like to tell you about.

I would like to use one of my lenses to construct a solar concentrator, primarily to fuse materials. An example by Dan Rojas of Green Power Science. Grant Thompson "the King of Random" shows how to remove the lens from the donor set.

A very thorough article on using Fresnel lenses for communications purposes.

I had read an instructable which suggested using two laser pointers resting on chairs. I am trying to use the same concept but using a more stable setup. I had some difficulty following the laser beam when I was manually holding the pointer.

As before I am using two benches with the lens suspended between them. Previously, the benches were about the same height. Now one bench is about 1 inch shorter in height. This difference allows space for a sliding cart to hold the laser pointers. The cart rides in a track so that I can smoothly move the laser pointer across the front of the lens.

There are two laser pointers on the cart. The yellow emits a red dot and the black emits a green dot. The pointers are held to the cart with hot glue. The height of the pointers is adjusted before gluing with a pair of tapered shims under each pointer to bring the dot high enough so that it just skims the out table top. If you enlarge the picture, you will notice the red laser dot just at the tabletop height of the out table (the higher one).

The red pointer has a rocker switch which allows it to stay ON. I must hold the button on the green pointer to keep it on.

A view of the side of the cart and it's track. The track is not fastened to the table and may be lined up parallel with the lines I have marked on the tabletop at 5, 10 and 15 inches back from the lens. The lens is on the left side.

You'll notice I haven't got the fronts of the laser pointers at the same distance but I don't think it matters. I have been using only one of the pointers at a time, not both of them. They are fixed down, the button on the green is over the beam so it is less tipsy and they can be slid easily.

I have the sheet to be tested hanging level with its focus (the center of the Fresnel pattern) at table top height (the height of the out table). I have two short strips of wood with hook eyes in the ends that I clamp to each side of the sheet.

In this way, I can easily unhook the sheet and reverse it so that I can send the beam into either the Fresnel side of the sheet or the smooth side. It is necessary to move the out table away to make some space to flip the lens. Normally I push the tables together to clamp hold flat the Fresnel lens at the desired height.

Here are my results so far (shown also in the first picture above):

Fresnel lens focal length
38x29in (96.5x73.7cm) Lens A30.5in (77.5cm)
35x27in (88.9x68.6cm) Lens B28.0in (71.1cm)

Note that my results are with the Fresnel surface of each lens facing the laser pointer (the top of the two illustrations).

I thought the lens performance would be approximately equal in the two orientations. In my observation, the determination of the focal length is less clear when the smooth surface of each lens is facing the pointer. I will do some more work and report shortly.

Thanks for your interest.

George Plhak
Lion's Head, Ontario, Canada

fresnel lens reading list
fresnel lens
fresnel lens 2 (this article)
fresnel lens 3

Friday, January 13, 2017

fresnel lens

I have a large flat plastic Fresnel lens hung between two benches that are the same height, more or less. The benches are pushed together so that the sheet is sandwiched between them. The sheet is supported on wires from hooks in the ceiling. I can vary the height by adjusting the wires.

I have two of these sheet lenses, but they are different. I am trying to measure the focal length of each, the distance from the lens to the point at which the light converges. A Frensel lens is like a magnifying glass, except in thin lightweight plastic sheet form.

Mine both came out of discarded rear projection televisions. It does take a bit of effort to free one of these from the set and it isn't for the faint of heart. I generated quite another pile of waste by taking out every part from the frame but perhaps my separation of the waste helps with the ultimate recycling effort?

Both lenses came from the sets as an assembly of two sheets, the Frensel and another sheet with very fine vertical stripes, like a diffraction grating. The two sheets were taped together anong their edges and held in plastic frames. I removed the frames and tape to get the assembly apart to free the Fresnel sheet.

At any rate, I have the sheet hung from the ceiling so that the center is approximately at the table height. I am using a laser pointer to see the direction that the beam is bent as it passes through the sheet.

This is a series of pictures showing the bending at the back of the sheet. The metal ruler is perpendicular to the back of the lens lined up with the main axis (at the center of the sheet).

I have marked lines parallel to the laser beam near both edges of the sheet with a ruler and I find that the lines converge at a point that is 30 inches from the sheet. This is the Focal Length of this sheet.

The sheets are different and seem to give different results depending on which side of the sheet faces the laser pointer.

Fresnsel lenses have application in concentrating photovoltaics with some interesting examples shown by Green Rhino Energy.

Fresnel lenses can also be used as solar concentrators to reach very high temperatures, like this.

Not sure what I am going to do with mine yet.

Thank for your interest

George Plhak
Lion's Head, Ontario, Canada

fresnel lens reading list
fresnel lens (this article)
fresnel lens 2
fresnel lens 3

The donor of one of my lenses, a Sony KP-43T70, made in Westmoreland, PA in February 2000.

Saturday, January 07, 2017

major appliances

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Now that I have one summer and a few months of winter electrical data, I am able to predict the relative usage of my major appliances in these two pie charts. My data is the percent of typical daily kilowatt hours kWh used by these major appliances.

The big light blue section of the chart is everything else (lighting, ovens, washer, dryer, dishwasher, computers, chargers, power tools, plug in heaters, garage door openers etc, etc). None of these are used often enough to deserve their own slice of the pie so I have lumped them together in one slice. I want to focus on my heavy electrical users, the other slices, for now. But the everything else category accounts for over half of my usage!

My spreadsheet (.ods format) is here.

Starting at the top left, water heating is the dark blue segment. My old electric water heater accounts for about 15% of my electrical usage both summer and winter. The water heater actually uses more during the winter because the ambient temperature of the basement, where my water heater is located, is cooler in the winter. My overall home usage goes up in the winter months as does the water heater so it is about 15% the total year round.

The refrigerator (orange) and freezer (yellow) together account for about 23% of summer usage, falling to about 15% together in winter.

The furnace (green) is not active in the summer but makes up a whopping 25% of winter usage. Although I have an oil burning furnace, it uses about 620 watts of electrical energy when running. I last wrote about my furnace here.

Finally, the base load (red), the things that are always ON, accounts for 17% of summer falling to 11% of winter usage. The base load is made up of a whole bunch of things which deserve their own category. I wrote about my base load here.

Thank you for your interest.

George Plhak
Lion's Head, Ontario, Canada

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