Around the world on a solar ebike

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solarEbike   10 W

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Re: Modeling daily Wh with PVWatts

Post by solarEbike » Sep 03 2018 4:29pm

UPDATE: This post is now obsolete. I've created a new version of this solarEbike Trip Planner which automatically imports weather data for any city in the world. The new version is available here: https://docs.google.com/spreadsheets/d/ ... edit#gid=0

solarEbike wrote:
Sep 03 2018 3:24pm
I've pre-loaded the spreadsheet with weather data for Oakland, California so you will need to import data for your own city. I will add instructions for doing this in a follow-up post.
If you want Wh for a city other than Oakland, California, follow these instructions closely. It looks like a lot of steps but it's mostly just tedious. There's some repetition and it's relatively straightforward.
  1. Make a copy of the spreadsheet: File > Make a copy...
  2. Open to https://pvwatts.nrel.gov/pvwatts.php in a separate browser tab.
  3. Enter a location in the search box. A city name is usually sufficient but be aware that the first Google Maps result will be automatically selected so you will want to specify "Vancouver, Washington" or "Vancouver, BC" and not just "Vancouver".
  4. The SOLAR RESOURCE DATA screen usually has a map to help you confirm that the correct location was selected but the map is currently disabled. If the location looks right, select Go to system info to continue.
  5. DC System Size (kW): 4 (do not change this, you will specify your panel size in the spreadsheet later)
  6. Module Type: Premium (if using SunPower cells)
  7. Array Type: Fixed (open rack)
  8. System Losses (%): 0 (we will specify these later in our spreadsheet)
  9. Tilt (deg): 0
  10. Azimuth (deg): 180
  11. Click Go to PVWatts results
  12. On the RESULTS page, scroll down to Download Results: Hourly and download the hourly CSV file
  13. Go to your spreadsheet and select the 0° fixed tilt tab at the bottom.
  14. Select File > Import... > Upload and upload the CSV file you just downloaded from PVWatts
  15. You will be asked for the Import location, choose Replace current sheet. This is the 4th option. Then, click Import data.
  16. Go back to your PVWatts browser tab and click Go to system info to go back one screen. If you wait too long, the site may time out and ask you to select your location again. Don't panic. This is normal.
  17. On the SYSTEM INFO screen, change Array Type: 1-Axis Tracking, all other values should be the same as for steps 5, 6, 8, 9 and 10 above.
  18. Click Go to PVWatts results
  19. On the RESULTS page, scroll down to Download Results: Hourly and download the hourly CSV file
  20. Go to your spreadsheet and select the 1-axis NS tab at the bottom.
  21. Import the second CSV file the same way as steps 14 & 15 above. Do not mix up the CSV files!
  22. Go back to your PVWatts browser tab and click Go to system info to go back one screen.
  23. On the SYSTEM INFO screen, change Azimuth (deg): 90, all other values should be the same as the last CSV file.
  24. On the RESULTS page, scroll down to Download Results: Hourly and download the hourly CSV file
  25. Go to your spreadsheet and select the 1-axis EW tab at the bottom.
  26. Import the third CSV file the same way as steps 14 & 15 above.
  27. Go back to your PVWatts browser tab and click Go to system info to go back one screen.
  28. On the SYSTEM INFO screen, change Array Type: 2-Axis Tracking, all other values should be the same as the last CSV file. Tilt and azimuth will be disregarded for 2-axis tracking.
  29. Go to your spreadsheet and select the 2-axis tab at the bottom.
  30. Import the fourth (and final!) CSV file the same way as steps 14 & 15 above.
  31. Go back to the Summary tab and check for any errors or broken formulas. You should see your new city name in row 17 repeated 4 times. If everything looks ok, your Outputs row should now be showing data for your new location.
You can save multiple scenarios by making copies of your spreadsheet. You don't need to repeat the import steps above unless you want to add a new city.
Last edited by solarEbike on Sep 11 2018 6:47pm, edited 2 times in total.
SWB recumbent, Grin all-axle hub (5T in 20" wheel), Phaserunner, 6x LiGo battery, 330 watt sun-tracking solar trailer with 3 Genasun MPPT boost controllers (in progress), CA3 (SolarAnalyst firmware), GPS Analogger, Rohloff IGH. Solar ebike build, Website, Instagram, YouTube

Tommm   100 W

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Re: Around the world on a solar ebike

Post by Tommm » Sep 03 2018 4:48pm

If you had some test runs, what is your average speed and how far you go one day, and how many hours you spend moving?

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solarEbike   10 W

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Re: Around the world on a solar ebike

Post by solarEbike » Sep 03 2018 5:20pm

Tommm wrote:
Sep 03 2018 4:48pm
If you had some test runs, what is your average speed and how far you go one day, and how many hours you spend moving?
I've logged about 2000 miles (3000 km) with various solar setups over the years, mostly short 2 day weekend camping trips in the San Francisco Bay Area between May and September. Average speed and distance varied a lot depending on the size of the solar panel I used, batteries I carried, availability of plug-in charging along the way, terrain, etc. My longest day ever was 144 miles (232 km), averaging 15 mph (24 kph) with 9 hours 33 minutes of moving time.

Michael Polak is a Sun Trip participant who tweets his daily numbers here: https://twitter.com/ArachneLabs

Does anyone else know about other sources with more of this kind of data? I know JLE uploaded log files recorded at 1Hz but are there any daily totals and averages out there for a long-ish solar ebike trip?
SWB recumbent, Grin all-axle hub (5T in 20" wheel), Phaserunner, 6x LiGo battery, 330 watt sun-tracking solar trailer with 3 Genasun MPPT boost controllers (in progress), CA3 (SolarAnalyst firmware), GPS Analogger, Rohloff IGH. Solar ebike build, Website, Instagram, YouTube

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solarEbike   10 W

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solarEbike Trip Planner 2.0

Post by solarEbike » Sep 11 2018 8:16pm

I've updated the solar modeling tool I posted earlier so that it now automatically imports weather data for any city in the world. Just enter your location, pick any date range and change the battery/panel specs to match your solar bike. Supports fixed and tilted arrays.

Use cases:
  • Figure out the solar panel size you need to meet your daily travel goal.
  • See if adding a tilt mechanism is worth the added weight, cost and complexity.
  • Plan a solar ebike trip.
The new version can be found here: https://docs.google.com/spreadsheets/d/ ... sp=sharing

Screen Shot 2018-09-11 at 5.53.34 PM.jpg

It can take up to 60 seconds to fully import and parse the data for a new city so please be patient while it loads. I'm looking for feedback on anything that needs clarification. I've tried to keep this as simple as I could without dumbing it down so much as to be useless.

PS: I've been playing around with it and it's telling me that the optimal design is to use dual-axis tracking whenever the sun is shining, store the energy in a 3kWh battery pack and only ride at night or when it is overcast. Some user discretion is advised.
SWB recumbent, Grin all-axle hub (5T in 20" wheel), Phaserunner, 6x LiGo battery, 330 watt sun-tracking solar trailer with 3 Genasun MPPT boost controllers (in progress), CA3 (SolarAnalyst firmware), GPS Analogger, Rohloff IGH. Solar ebike build, Website, Instagram, YouTube

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solarEbike   10 W

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sun tracking tilt mechanism

Post by solarEbike » Nov 12 2018 9:41pm

I've had a few requests for details about the sun tracking tilt mechanism I built so I'll try to gather the key bits here in one place. This is not going to be a clear how-to guide with easy to follow steps. I've had lots of failures and a few successes and I'm still working on optimizing my design. If you're reading this because you're planning to build your own tracker be prepared to fill in some blanks. Post your questions here. I'll answer them if I can.

For starters, here's the trailer and tilt mechanism I'm talking about. In this video clip, I'm demonstrating the full range of motion which is about +/- 45° from horizontal. The tilt axis is parallel to the direction of travel. I'm controlling it with a DPDT toggle switch which simply reverses the polarity on the 12V DC motor of the linear actuator. I'll discuss automated tracking using an Arduino and light sensors later in this post.


I'm using a recumbent bike but there's nothing about any of this that is recumbent specific. The above trailer is my own design, optimized for low weight and a wide range of tilt travel. However, any bike trailer will work. Below is an early iteration of this design with no motorized tilt mechanism. This is a Burley Flatbed trailer with a couple of selfie sticks to prop up the panel. It worked just fine but switching the tilt from the left side to the right side was cumbersome.
Burley flatbed solar trailer.jpg
The red support panel is 1" (2.5 cm) rigid building insulation foam covered with a layer of fiberglass and epoxy with aluminum inserts at mounting points for structural support. The construction is similar to how surfboards are made. It is reasonably lightweight and stiff but it was a lot of work to make. This might be the right approach for you if you're familiar with composites but it's a messy learning curve if this is your first such project. There are commercially available "sandwich panels" like this but they're generally very expensive as the lightest ones are driven by industries with big budgets: aerospace, racing, yacht building. Other solar bike builders have created supports with inexpensive aluminum extrusion products as ribs under the solar panel. I've avoided this approach because my ultimate choice of solar panel requires a fully solid support surface.

Assuming you have mounted your solar panel on a trailer or overhead as a canopy roof and it is free to pivot left and right, the next step would be to ask if motorizing the tilt is worth the added weight and complexity. Based on my experience, you should definitely be able to manually tilt your panel at least 45° for charging while stopped. Early and late in the day, the correct tilt angle can more than double your solar output. This makes a big difference for long distance solar ebike touring. You can accomplish this by leaning your bike against something while stopped.

Adding the ability to automatically change the tilt while riding can add 5-30% to your average daily solar watt-hours, although 10-20% is more realistic. The actual number depends on your location, time of year, travel direction, number of daily hours riding vs. stopped, number of cloudy days vs. sunny days (tilt plays a minor role when it's cloudy). Based on my experience, most solar ebike builders will be better served by getting a slightly larger solar panel and skipping the weight and hassle of a motorized tilt.

Me? I like a challenge and the cool factor of having a tracker was too tempting to pass up.

I used a linear actuator (this one). It's a 12V DC motor connected to a lead screw. They typically include limit switches which shut off the motor when the bar is fully extended or retracted. Some come with a built-in potentiometer which you can use to read the current position, although this isn't strictly necessary depending on how you plan to control the panel position. The one I used is not waterproof so that would be a problem on a long tour. It's also bigger and heavier than is strictly needed for a panel of my size. If I was doing it over again, I would consider using this one.
Bullet_1.jpeg

Finding the right anchor points for the two ends of the actuator was tricky. The way I did it in the video above works but the lower mount hits the ground during aggressive cornering. A shorter actuator would have allowed me to mount the upper end closer to the panel pivot axis. Also, the closer you can place your panel pivot axis to the center of mass of the moving panel the lower the forces on the actuator throughout its range of motion. I modeled this in CAD but ended up doing much trial and error with the physical hardware before finding the right mounting points.

Once you have your linear actuator mounted, you can simply control it manually with a DPDT toggle switch (double-pole, double-throw) like this. With the help of a handlebar mounted watt meter to measure solar output, you can make adjustments on the fly with the flick of a switch.
5322587f348316b35a1518cbcf0608ad.png
5322587f348316b35a1518cbcf0608ad.png (169.82 KiB) Viewed 312 times

I took several test rides with this semi-manual setup but quickly got tired of making tilt adjustments by flipping this switch while trying to keep an eye on the road and the watt meter. Don't get me wrong. It can certainly be done. I'm just pointing out that this is a perfectly valid project end point for some. You have something that works and not having to stop and get off the bike to adjust the panel tilt angle is rewarding enough to justify the trouble you've gone to thus far.

The next upgrade step involves connecting sensors to an Arduino microcontroller and writing some code. If this sounds intimidating or you have no idea what I'm talking about, don't worry. I had never attempted something like this before and picked up everything I needed to know by watching YouTube videos and reading tutorials. However, I had quite a bit of experiencing writing code in JavaScript and Ruby before I attempted this so learning to write a "sketch" (programming instructions) in the Arduino language wasn't a big leap. If you've never written a line of code you're probably going to want to recruit some help for this part.

The automated tracking algorithm is very simple. Two light sensors are mounted at 45° angles to the solar panel. The Arduino reads the light input from the two sensors. If one sensor is getting more light than the other, the motor moves the panel toward the light until the sensor values are the same. Here's how I mounted the sensors. There are two pairs shown. The embedded ones in the panel are nicely protected from water and physical damage but I made the window a little too small so I'm trying a second set (with black heat shrink tubing).
sensors.jpg


The Arduino looks like this. The white breadboard is temporary. Once I get everything dialed it, I'll move it to a perf board and pot the whole thing.
Arduino Metro Mini, motor controller, sensors, BLE.jpg

I got most of the parts for my automated controller from Adafruit.com because they have great tutorials and I like the way they support the Arduino open source platform.

Parts list:
This is the part where I cross my fingers and hope that you got enough from this to finish on your own. I muddled my way through by reading the product descriptions above and then following all the tutorials on each page until I got light activated solar panel positioning. My code is an ugly mess so I'm reluctant to share it and the panel occasionally gets stuck facing away from the sun but it mostly works.

UPDATE:

I just remembered that you can add automatic sun tracking without an Arduino or any coding. There are several ready-made solar tracking controllers available. They're designed for stationary PV systems with single axis tracking via a linear actuator so they should just be plug and play. The light sensors are all a little too big and clunky for my liking so I build my own but I imagine these should work just fine on an ebike.

single-axis-trackers.jpg

Here are some links I found. If these have expired by the time you're reading this just try a search for "solar tracker controller" on your favorite shopping site.
There's even a complete kit with linear actuator on AliExpress right now for $110 US including shipping. Will it stand up to thousands of miles of dust, rain and vibrations on a solar ebike? Probably not. Will it get you up and running quickly so you can figure out if sun tracking is worth pursuing further? Possibly... assuming it doesn't arrive incomplete, broken or totally different from the specs and photos. (Sorry, AliExpress hasn't worked out for me in the past...)

Screen Shot 2018-11-15 at 10.29.41 AM.jpg

PS: I just watched a YouTube video for one of these products and found a potential show-stopper: there's a 3 minute delay between position updates. That's reasonable for a stationary system but way too long for a mobile system. Check with the vendor before ordering. On my own solution, I use a 3 second delay. (Also, I need to add some additional checks to ensure I don't exceed the actuator's duty cycle.)
Last edited by solarEbike on Nov 15 2018 2:49pm, edited 2 times in total.
SWB recumbent, Grin all-axle hub (5T in 20" wheel), Phaserunner, 6x LiGo battery, 330 watt sun-tracking solar trailer with 3 Genasun MPPT boost controllers (in progress), CA3 (SolarAnalyst firmware), GPS Analogger, Rohloff IGH. Solar ebike build, Website, Instagram, YouTube

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wturber   100 kW

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Re: Around the world on a solar ebike

Post by wturber » Nov 15 2018 12:43pm

Cool. Thanks for detail all of this out.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Around the world on a solar ebike

Post by amberwolf » Nov 15 2018 9:22pm

FWIW, you can recycle old Lazy-boy chairs / etc for their actuators. I have a few of them from one here, though I don't know offhand if they're long enough throw to do what's necessary in this application.

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solarEbike   10 W

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solar roof

Post by solarEbike » Nov 18 2018 10:28pm

A little progress update. After ten years of stubbornly refusing to explore overhead mounting options, I finally decided that having a small roof over my head would have enough value in keeping the sun and rain off my head to offset the perceived downsides: high center of gravity, aero drag, cross wind problems and obstructed view of the road and scenery. Here's what I came up with:

IMG_1821.jpg

I made it just big enough to fit one of my four solar panels (4x6 SunPower cells). The other three are still going on the trailer. The tilting mechanism can do a full 90° tilt for charging while parked and about 25° while riding. Yes, that Ferrari totally photobombed my perfectly composed shot.

IMG_1824.jpg

I can reach the indexing plunger and make adjustments single-handed while riding. The 8" aluminum ring is a turntable bearing (table-top lazy susan). The rest is custom machined aluminum, carbon fiber tubing and stainless steel fasteners.

IMG_1828.jpg

Welcome to California. Weather today: Smoke. Blue masking tape is temporary while I dial in the optimal tube lengths. The aluminum end caps will be held in place with 3M Scotch-Weld 2216 Epoxy. Stainless steel hinges on top to allow flat packing for air transport.

selfie-with-weather.jpg

It's a little more bouncy than I hoped but tolerable, I think. I plan to route the wires inside the carbon tubes and add some slim profile LED lights to the roof to increase my visibility on the road.
Last edited by solarEbike on Nov 19 2018 3:49pm, edited 1 time in total.
SWB recumbent, Grin all-axle hub (5T in 20" wheel), Phaserunner, 6x LiGo battery, 330 watt sun-tracking solar trailer with 3 Genasun MPPT boost controllers (in progress), CA3 (SolarAnalyst firmware), GPS Analogger, Rohloff IGH. Solar ebike build, Website, Instagram, YouTube

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thundercamel   1 W

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Re: Around the world on a solar ebike

Post by thundercamel » Nov 19 2018 11:48am

I like the Lazy Susan as a starting point. Nice work :)
My Ebike builds - Existing bikes, affordable motor kits, self built 14s6p batteries

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Re: Around the world on a solar ebike

Post by Tolt » Nov 19 2018 12:12pm

You've got a lot of nice, custom aluminum parts on your builds -- and a tiny shop (as do I). Are you doing the machining yourself? What machine tools do you have?

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solarEbike   10 W

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Re: Around the world on a solar ebike

Post by solarEbike » Nov 19 2018 2:31pm

thundercamel wrote:
Nov 19 2018 11:48am
I like the Lazy Susan as a starting point. Nice work :)
That was a fortuitous discovery. I started out trying to design a pivot mechanism from scratch, went browsing on McMaster-Carr for bearing ideas, saw a bunch of very expensive and heavy slewing bearings and then stumbled across this $20 solution on Amazon. It makes these weirdly brittle chips when I drill it so it's not the 6061 alloy I'm used to. I'm rolling the dice here that it will hold up over time.

Tolt wrote:
Nov 19 2018 12:12pm
You've got a lot of nice, custom aluminum parts on your builds -- and a tiny shop (as do I). Are you doing the machining yourself? What machine tools do you have?
Good question. My workshop is a one car garage. I watch a lot of YouTube machining videos but I've never used a lathe, mill or anything CNC. I've looked into becoming a member at one of my local maker spaces to get access to some fun toys but never quite got around to it. I've been able to drill, cut, shape and polish aluminum mostly using a few low-tech low-budget woodworking tools and a lot of pig-headed perseverance.

IMG_5813.jpg

Right to left:
  • Drill press (donated) with a 6" cross-slide vise ($75 at Harbor Freight*). You can do a lot with a drill press and a wide assortment of drilling and cutting bits. Step bits are your friend.
  • Band saw ($130 at Home Depot). This is a woodworking tool but it cuts aluminum with ease.
  • 4" disc sander ($75 at Harbor Freight*)
  • 1" belt sander ($53 at Harbor Freight*)
  • 8" (200mm) digital calipers ($54 on Amazon)
  • The purple rectangle in the center is a sheet of sand paper glued to a piece of MDF with spray adhesive. Very effective for polishing and shaping small parts.
  • The perforated white tabletop under that is a home-made downdraft table. Attach the shop vac to the box under the table and sanding particles go down instead of covering the entire shop. Pretty sweet for nasty fine particles like carbon fiber.
* Harbor Freight has huge sales and crazy coupons so I actually paid significantly less for most of these. Also, I got these years ago.

I usually start by taking a few measurements, make a rough drawing in SketchUp, print out a 1:1 scale paper copy, stick that to some aluminum stock with spray adhesive and start removing material. A lot of my problem solving happens during the machining phase so it's nice to be able to make changes on the fly which might not be so easy in a CAD/CAM workflow without starting over.

62192CEA-E331-43DB-AC6A-EE589F5C5D12.jpg

Pro tip: You can import McMaster-Carr 3D components directly into Fusion 360 right within the interface. If you use Fusion 360 and haven't used this feature it will change your life.
SWB recumbent, Grin all-axle hub (5T in 20" wheel), Phaserunner, 6x LiGo battery, 330 watt sun-tracking solar trailer with 3 Genasun MPPT boost controllers (in progress), CA3 (SolarAnalyst firmware), GPS Analogger, Rohloff IGH. Solar ebike build, Website, Instagram, YouTube

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wturber   100 kW

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Re: Around the world on a solar ebike

Post by wturber » Nov 19 2018 4:05pm

Years ago I made a 72 tooth chainring out of 6061 T6 aluminum using a bandsaw, drill press, a wooden jig, and hand tools. You can do a lot with a basic woodworking setup and some aluminum. :^)

Image
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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