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Blog Solar Energy Harvesting with Epishine Flexible Solar Cell - Pt 1: intro
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EMI-Reduction-Techniques
Engagement
  • Author Author: Jan Cumps
  • Date Created: 29 Jul 2020 4:55 PM Date Created
  • Views 3889 views
  • Likes 12 likes
  • Comments 14 comments
  • epishine
  • energy_harvesting
Related
Recommended

Solar Energy Harvesting with Epishine Flexible Solar Cell - Pt 1: intro

Jan Cumps
Jan Cumps
29 Jul 2020

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
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Top Comments

  • jesni
    jesni over 5 years ago in reply to Jan Cumps +5
    I'm jumping in here for some clarifications, I work at Epishine. Jan Cumps 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…
  • jc2048
    jc2048 over 5 years ago +3
    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…
  • Jan Cumps
    Jan Cumps over 5 years ago in reply to jc2048 +3
    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…
  • Jan Cumps
    Jan Cumps over 3 years ago in reply to Jan Cumps

    It seems to be that at the least, the supercap is in bad shape.

    I charged it up to 5 V. It can have 5.5 V.

    As soon as I disconnect the output, only a DMM connected, it loses its charge.
    After 15 minutes, the voltage over the capacitor dropped from 4.99 to 4.65 V.
    Below the picture at 12 minutes:

    image

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  • Jan Cumps
    Jan Cumps over 3 years ago in reply to Jan Cumps

    It's charging. I'm using 2 mA constant current. A bit much but my supply doesn't go lower.

    image

    As soon as I remove the source, the discharge starts. Without load.

    image
    I haven't tested if this is a small reaction or if it really loses its charge that fast...

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  • Jan Cumps
    Jan Cumps over 3 years ago in reply to dougw

    I did that in the past, and it used to charge according to the manufacturer's specs. The solar cell is giving power but the supercap isn't charging.
    I'm trying to slowly charge it with a power supply and current limit, to see if it needs reviving ...

    image

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  • dougw
    dougw over 3 years ago in reply to Jan Cumps

    With bright indoor lighting it should fully charge the capacitor in a few minutes or maybe 10 minutes, I don't remember exactly, but you can see the charge rate in some of my screen shots (at 60s/div the screen width is 12 minutes):

    /technologies/power-management/b/blog/posts/epishine-leh-solar-cell-evaluation-kit-review

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  • dougw
    dougw over 3 years ago in reply to Jan Cumps

    I had to use Firefox to enter a reply - Chrome doesn't work.

    The boost circuit won't start charging the capacitor until the solar cell voltage exceeds 350 mV. You could try a brighter light source or you could try injecting 0.5 V at the solar cell output to see if solar cell is working or the charging circuit is working.

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