pv-hot-water

Control software for a custom photovoltaic solar hot water setup.
The system consists of an array of solar panels providing two circuits. There is an exterior GFCI panel, an interior panel, and a pair of electric hot water heater tanks converted to DC.
This repository is solely for the software component of this system.

Initially, the software consisted of a large Java program (written in 2020) running on the Raspberry Pi in the interior panel with a corresponding Android application that connected with a custom protocol over UDP.
The old system, while having proven itself to be stable, has numerous inefficiencies and slow performance.
This software redesign has similar goals and priorities, being developed for the same system. The specific improvements over the previous system will not be documented further than they are above.

Priorities and Considerations

1. Safety

   While the hardware provides numerous shutoffs and such, the software should also continuously monitor the state and conditions of the hardware and detect and appropriately respond to as many forseeably possible (though generally unlikely) unfavorable circumstances.

2. Stability

   Safety being a priority, as well as operability being important, the value of stability can be immediately derived. Due to the nature of the system, updates are extremely infrequent. Meanwhile, regardless of technical know-how of potential users, the system needs to "just work."
   The system should be well isolated from potential cyber threats and designed to require as little maintenance as possible. Maintenance, such as monitoring database size, etc, should be extremely straightforward if required.

3. Ease of use

   As previously mentioned, the system needs to "just work." General usage, monitoring, statistics, etc. should be able to be understood and used by the layman and engineer alike (as much as possible).
   There should be an easy user interface to immediately identify potential issues, as well as to see and understand handy or interesting statistics about the operation of the system.

4. Data collection

   Data should be collected by the physical sensors of the system to evaluate saved energy, performance of the solar panels, efficiency of the storage within the two tanks, etc. This should be easily accessible as previously mentioned and there should be a calibration mechanism for most measurements as well.

Interior Control Panel

The primary control electronics are in the interior panel.

• Raspberry Pi, running the main control software

  This will act as a thermostat, monitor hardware conditions, provide basic information on the panel LCD screen, collect data to store in the database, host a Flask web app for a user interface, a Flask RESTful API for the web app to use and for an Android app to potentially use.

• Arduino Nano, used for its cheap a/d converters and as an i/o buffer

  This will be used as an intermidiary between the raspberry pi and some of the hardware.

• ESP32, maintaining a communication link to the exterior GFCI panel

  This will allow communication between the raspberry pi and the GFCI panel to allow for turning off the circuits externally and controlling/overseeing the ground fault detection.

External GFCI Panel Hardware

The exterior panel with a circuit breaker and current sensors.

• Arduino Nano, running GFCI polling loop

  This monitors the current on both sides of each circuit in order to detect ground faults and turn off the circuits.

• ESP32, maintaining a communication link to the interior panel

  This will allow communication between the raspberry pi and the GFCI panel to allow for turning off the circuits externally and controlling/overseeing the ground fault detection.