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# System prepended metadata

title: Acraea

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# Process control for Acraea

## Project description

**Process control for Acraea using an ESP32**

**Shantnav Agarwal**

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**Brief description of your project:**

Acraea is a an open source small scale solar desalination and water purification prototype. This plant takes heat as input on one side of the device and uses it to evaporate sea water. This water is then collected on the other side through condensation and allowed to flow out of the system as potable water.

![Acraea](https://codeberg.org/LibreWater/Acraea-Prototype/media/branch/main/res/assets/media/img/white_background.jpg)
*Image reproduced from LibreWater's render of the prototype*
### In Detail
#### Heat
Currently, the prototype uses Thermo silicon pads as a source of heat. The prototype can be powered by solar energy as well. 

![VMED](https://codeberg.org/LibreWater/Acraea-Prototype/media/branch/main/res/assets/media/img/VMED_Process_Drops.jpg)
*Image reproduced from LibreWater's render of the prototype*
![Process](https://hackmd.io/_uploads/BJDvEcgUp.png)

#### Water purification
Water enters the system through cotton cloth wicks made out of bedsheet. Through heat it evaporates. This water vapour then comes in contact with a cold aluminium plate and condenses. The droplets on this plate eventually trickle down and are collected as potable water. A "chamber" is defined as one cycle of evaporation and condensation. The prototype has multiple chambers stacked horizontally to increase efficiency and performance. Such a device is also called a vertical multiple-effect diffusion solar distiller (VMED).

#### Control process
The moisture level of cotton wicks is maintained by estabilishing a head of water above them. The water gradually trickles down through the cotton wicks due to the effect of gravity and capillary action.

We have to maintain a certain head of water which is correlated with the amount of input power that we have. i.e, This head coupled with the percolation rate should replace the amount of water being evaporated.

The challenge is to regulate the flow of input sea water as the amount of solar power changes during the day.

* Too much sea water input for the energy input: there will be no evaporation, just lukewarm sea water coming back out - and no fresh water.

* Too little sea water input for the energy input will lead to dry spots and a thick salt crust will form all over the evaporation surfaces, reducing performance and ultimately quality.

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**Current status of your project and documentation**:
https://github.com/shantnavagarwal/Acraea_Controller
Additional information and design decision can be found on the HackMD page below:
https://hackmd.io/@zd8-NQQSRIi_4XrtoXbukQ/r107-LpxT

### Share a link to the peer review you did before
https://hackmd.io/o3AYBDMAQIaH_W0L6NqNbg
### Share link to the peer review you have received


## Share general feedback to the academy
### What did you learn and/or experienced that was useful to progress in your project
This academy provided me with a very "complete" knowledge of what open source hardware is all about. The weekly lessons covered various aspects that are important through the lifecycle of any project and are a great resource to learn what "open" truly means. 

I appreciate being able to work on an actual opensource project by Librewater and contribute to it. Working on the project has allowed me to develop both my soft and hard skills. Simon has been a great mentor throughout providing guidance and helping me find an overall direction to work towards!

Overall, this has been a fullfilling experience for me and I will continue contributing to Acraea by completing the development of the control process on the ESP32.

I sincerely thank all the organisers for creating this Academy and introducing us, students, to open source hardware.

### Do you find that the estimation of 4 hours per week is fair to be able to perform the exercises? 
Yes, 4 hours per week is enough for the lecutres and exercises.

### What things can we improve for next rounds
One thing I struggled with is the time at which the academy is held. I have experienced that many courses at TU Delft have their practicum sessions from 13:45 on Friday which clashes with the Academy's schedule. 
For me personally, it would be better if it was scheduled later in the evening. 

Also, it was really difficult for me to participate during the exam weeks of the quarter. A break in between would have helped me.