1. Preliminary Calculation
2. Measuring setup
   1. Flows
   2. Temp
3. Controller / Relay

Intro

I live in an area with quite high solar input (globalsolaratlas). My domestic hot water is electric, leading to the DHW to probably account for 80% of my electricity consumption.

This is an attempt to pre-heat the mains intput into my water heater

Preliminary Calculation

There are some devices on amazon, such as a dome panel, and flat panels.

Considering the Global tilted irradiation at optimum angle of about 6.8 kWh/m/m/day at my location, the following energy should be gainable with the dome panel, the flat panel, and a 30 ft 1/8 inch hose.

	Unit	Panel	Dome Panel	Hose
Width	m	0.60	0.57	0.0127
Length	m	3.00	0.57	30.48
Area	m*m	1.86	0.33	0.39
GTI	kWh/m/m/day	6.80	6.80	6.8
Daily Energy	kWh/day	12.63	2.22	2.63

Measuring setup

Flows

• https://tutorials-raspberrypi.com/reading-out-the-flow-meter-water-flow-sensor-on-the-raspberry-pi/#google_vignette
• https://www.bentasker.co.uk/posts/blog/house-stuff/monitoring-a-fishtank-with-influxdb-and-grafana.html
• https://www.amazon.com/dp/B07QQW7JZL?psc=1&ref=ppx_yo2ov_dt_b_product_details

Pins:

• Red (3.3 V Power): pin 1
• Black (ground): pin 6
• Yellow (signal): pin 7; GPIO 4

#!/usr/bin/python
import RPi.GPIO as GPIO
import time, sys

flow_sensor_gpio = 4

GPIO.setmode(GPIO.BCM)
GPIO.setup(flow_sensor_gpio, GPIO.IN, pull_up_down=GPIO.PUD_UP)

global count
count = 0

def countPulse(channel):
   global count
   if start_counter == 1:
      count = count+1

GPIO.add_event_detect(flow_sensor_gpio, GPIO.FALLING, callback=countPulse)

while True:
    try:
        start_counter = 1
        time.sleep(1)
        start_counter = 0
        flow = (count / 7.5) # Pulse frequency (Hz) = 7.5Q, Q is flow rate in L/min.
        print("The flow is: %.3f Liter/min" % (flow))
        count = 0
        time.sleep(1)
    except KeyboardInterrupt:
        print('\nkeyboard interrupt!')
        GPIO.cleanup()
        sys.exit()

Temp

• https://pinout.xyz/pinout/1_wire
• https://www.amazon.com/dp/B012C597T0?psc=1&ref=ppx_yo2ov_dt_b_product_details
• https://www.circuitbasics.com/raspberry-pi-ds18b20-temperature-sensor-tutorial/

Pins:

• Red: 5V (pin 2 or pin 4)
• black: ground (8 or 14)
• Yellow: Pin 11 (GPIO 17) and Pin 12 (GPIO 18)

Not sure if we have to do the following:

1. sudo modprobe w1-gpio
2. sudo modprobe w1-therm

Configuring the One-Wire interface on a Raspberry Pi, using GPIO pin 7 without a pull-up resistor.

sudo dtoverlay w1-gpio gpiopin=17 pullup=0
sudo dtoverlay w1-gpio gpiopin=18 pullup=0
sudo dtoverlay w1-gpio gpiopin=27 pullup=0

Make permanent:

1. sudo nano /boot/config.txt dtoverlay=w1-gpio,gpiopin=17,pullup=0 dtoverlay=w1-gpio,gpiopin=18,pullup=0 dtoverlay=w1-gpio,gpiopin=27,pullup=0
2. Reboot

For my system:

• GPIO 17: 28-3ce1d44312b4 Flow
• GPIO 18: 28-3ce1d4438ff7 Return
• GPIO 17: 28-3ce1d4432b6f Ambient

Verify

ls /sys/bus/w1/devices

Controller / Relay

Connecting the pins