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  • Author Author: Jan Cumps
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Solar Energy Harvesting with Epishine Flexible Solar Cell - Pt 1: intro

Jan Cumps

I got a preview of a light harvesting kit from Epishine and element14. It's a combination of a flexible solar cell and a energy collection circuit.

I haven't used products from Epishine before and I'm not affiliated. I'm going to review the kit with open mind (and high excitement).

I've reviewed microcontroller circuits that are designed to use harvested energy. This is the first time I have a power circuit that specialises in harvesting energy.

 

The Evaluation Kit

 

The kit is named "Evaluation kit for Epishine Light Energy Harvesting".

It's part solar cell, part energy collector.

 

image

image source: me

 

The energy collector is a circuit that will accept very low energy input (in this case, a small solar cell), and collect that energy in a super cap.

Once the collected energy is sufficient, you can use it to power an electronic circuit.

It can - temporarily - provide decent power. Way more than what the lower energy source by itself  can deliver.

This is't unique. There are energy collectors and joule thieves around for a while.

 

The solar cell is rather spectacular though. It's a flexible cell - printed on a sheet that looks like an overhead slide.

The print is organic material (Epishine calls it organic electronics and photovoltaics).

The sheet has the thickness and flex of one side of a paper-laminating shell (my estimate).

image

image source: preview of the kit's product page

 

The PCB is flexible and thin too. Not as flexible as the solar panel, but the two stacked together show how thin the whole package can be.

image

image source: preview of the kit's product page

 

Main specifications:

  • 1.8 to 3.3 V
  • 300 mA max
  • can be backed up by a battery, or can extend main battery life

 

Epishine the Company

 

I have this info from the internet - from the company website. I'm adding it to the intro because they aren't a household name.

Feel free - as reader or as Epishine representative - to correct and refine.

They are a young Swedish company, with a long term goal to manufacture market-competitive sheet-printable flex solar cells (and the machines capable of printing those).

At this moment, they design solutions that use the flexible cell technology in specific lighting conditions - such as indoor and ambient light. With the goal to avoid batteries or prolong battery life.

 

How to Evaluate the Kit?

 

I'm going to focus on the electronic performance.

  • Charging profile
  • How it behaves under load, with and without light
  • Discharging profile
  • an application

 

If you have specific requests, put them in the comments below*

Now off to the real work

image

image source: me

 

*no promises - but if it fits the design's goal and ignites my interest, yes please

 

Related blog
Pt 1: intro
Pt 2: Circuit Analysis
Pt 3: Charge and Discharge
Pt 4: Battery Backup
Pt 5: test points
Parents

  • Looks interesting to experiment with.

     

    I found these patents

     

    https://worldwide.espacenet.com/patent/search?q=epishine

     

    Their IP seems to be in the area of the lamination and printing, rather than the cell material.

     

    They give hints as to the problems with organic polymers for the conversion from light: ageing and degradation are obviously the key ones. Not necessarily a problem - depends a lot on the kind of application and the lifetime required, and what they've done to mitigate the issues. One thing to watch is that it might not be protected too well from UV. Do they say it's suitable for outdoor use? All the applications shown on the website are under artificial light.

     

    There's also a mention of protecting the polymer from mechanical damage, so perhaps don't flex the panel too tightly. It's flexible to go round a printing drum, but that could be large and not too much of a curve at all.

     

    On the cell side of the circuit, you might consider measuring the VI curve directly [is it a diode curve?], without the charging circuit connected, to determine the maximum power point at several different levels of illumination. Then reconnect the charging circuit and see if it manages to get it close to those points. You wouldn't need a calibrated light source; just different distances away from something like a desk lamp, so that it was repeatable between the two sets of tests, would do.

  • in reply to jc2048

    One thing to watch is that it might not be protected too well from UV. Do they say it's suitable for outdoor use? All the applications shown on the website are under artificial light.

    The website indicates they aim for indoor / ambient. I received a draft spec for the evaluation board that doesn't elaborate on this.

     

    It's flexible to go round a printing drum, but that could be large and not too much of a curve at all.

    On the kit, it's glued (or taped - can't see how it's done) to a flex PCB. No risk of over-flexing it there.

    In the main post above, I pasted a "promo" photo from the kit's spec. The way they bend it there looks like a reasonable maximum.

     

    On the cell side of the circuit, you might consider measuring the VI curve directly [is it a diode curve?] ...

    I want to do that. At the end of everything else though. I'd have to physically intervene" to disconnect the cell from the circuit.

    The nature of the construction makes this a risky exercise. So yes, but when I'm finished with the overall board.

     

    I found these patents...

    That is a great find! I only checked the website, and the draft info I got from Epishine.

    The patents may point out the most exciting part of this kit: the printed solar panel.

     

    The harvesting circuit is more common ground. The most interesting part of that is the miniaturisation.

    It's small footprint, low height, on flex.

    With a mysterious super cap that's constructed a little like a tiny rechargeable battery.

    I haven't checked it yet, but it says: GA230 N1JA41 0.40 F 5.0 V CAP-XX BAL (datasheet).

     

    edit: the harvest IC is from e-peas. A Belgian company, 35 KM from my doorstep <3

  • in reply to Jan Cumps

    I'm jumping in here for some clarifications, I work at Epishine.

      wrote:

     

    One thing to watch is that it might not be protected too well from UV. Do they say it's suitable for outdoor use? All the applications shown on the website are under artificial light.

    The website indicates they aim for indoor / ambient. I received a draft spec for the evaluation board that doesn't elaborate on this.

     

    The cell is designed for maximum performance indoor in low light situation, to be used in low power sensors or the like. It is not suitable for outdoor use.

     

    It's flexible to go round a printing drum, but that could be large and not too much of a curve at all.

    On the kit, it's glued (or taped - can't see how it's done) to a flex PCB. No risk of over-flexing it there.

    In the main post above, I pasted a "promo" photo from the kit's spec. The way they bend it there looks like a reasonable maximum.

    The cell is quite flexible, we guarantee 6mm as the minimum bending radius.

     

    On the cell side of the circuit, you might consider measuring the VI curve directly [is it a diode curve?] ...

    I want to do that. At the end of everything else though. I'd have to physically intervene" to disconnect the cell from the circuit.

    The nature of the construction makes this a risky exercise. So yes, but when I'm finished with the overall board.

     

    You need to desolder the cell's contacting points to measure the I/V curve. Don't try and remove the cell from the PCB though as the adhesive is strong and you'll damage the cell.

Comment
  • in reply to Jan Cumps

    I'm jumping in here for some clarifications, I work at Epishine.

      wrote:

     

    One thing to watch is that it might not be protected too well from UV. Do they say it's suitable for outdoor use? All the applications shown on the website are under artificial light.

    The website indicates they aim for indoor / ambient. I received a draft spec for the evaluation board that doesn't elaborate on this.

     

    The cell is designed for maximum performance indoor in low light situation, to be used in low power sensors or the like. It is not suitable for outdoor use.

     

    It's flexible to go round a printing drum, but that could be large and not too much of a curve at all.

    On the kit, it's glued (or taped - can't see how it's done) to a flex PCB. No risk of over-flexing it there.

    In the main post above, I pasted a "promo" photo from the kit's spec. The way they bend it there looks like a reasonable maximum.

    The cell is quite flexible, we guarantee 6mm as the minimum bending radius.

     

    On the cell side of the circuit, you might consider measuring the VI curve directly [is it a diode curve?] ...

    I want to do that. At the end of everything else though. I'd have to physically intervene" to disconnect the cell from the circuit.

    The nature of the construction makes this a risky exercise. So yes, but when I'm finished with the overall board.

     

    You need to desolder the cell's contacting points to measure the I/V curve. Don't try and remove the cell from the PCB though as the adhesive is strong and you'll damage the cell.

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