Capturing Solar Generation Data from the GoodWe Portal.

We recently had a solar PV system installed on our roof and I wanted to capture the amount of energy being generated into our Domoticz console. Now Domoticz has a hardware option to capture such data from the Solaredge system. I personally cannot vouch for how well that works as unfortunately we have a GoodWe inverter so our generation data goes into the http://www.goodwe-power.com/ portal and not the Solaredge system. Am I jealous? Well maybe a little, the solaredge portal looks rather slick compared to the GoodWe system.

Anyway if the data is online somewhere it can be captured so that is what I set out to do. It didn't take much work in the end. I poked around on the website for a little while and looked for any clues that may indicate an API of some description but these searches turned up very little.

What I did find was that GoodWe have their own android app (com.goodwe.EzManage.apk) for monitoring the generation data. I managed to download the .apk, extract it a and began to poke around inside. Within that apk I managed to find a list of strings;

http://goodwe-power.com

http://www.goodwe-power.com

http://www.goodwe-power.com/goodwe/Mobile

http://www.goodwe-power.com/goodwe/Mobile/GetAddress

http://www.goodwe-power.com/goodwe/Mobile/GetInventerDetail?inventerSN=

http://www.goodwe-power.com/goodwe/Mobile/GetMyPowerStationById?stationId=

http://www.goodwe-power.com/goodwe/Mobile/GetMyPowerStationByUser?userName=

http://www.goodwe-power.com/goodwe/Mobile/GetMyPowerStationByUserForES?username=

http://www.goodwe-power.com/goodwe/Mobile/GetPacLineChart?stationId=

http://www.goodwe-power.com/goodwe/Mobile/GetPowerBarChart?stationId=

http://www.goodwe-power.com/goodwe/Mobile/GetPowerBarChartForES?stationId=

http://www.goodwe-power.com/goodwe/Mobile/GetSOCLineChart?stationId=

http://www.goodwe-power.com/goodwe/Mobile/Login?username=

These strings were instantly recognisable as REST endpoints so I logged into the portal and grabbed my station ID from the url and gave the GetMyPowerStationById endpoint a try using the following format.

www.goodwe-power.com/Mobile/GetMyPowerStationById?stationID=63cd46b8--9999-99aa-188b5690238b

This is what I got back;

{
    "curpower": "0.000kW",
    "capacity": "3.000kW",
    "percent": "0",
    "status": "Offline",
    "createdate": "2015-05-28",
    "eday": "0.0kWh",
    "etotal": "26.6kWh",
    "income": "£0.00",
    "totalincome": "£3.46",
    "co2reduce": "0.000",
    "totalco2reduce": "0.010",
    "treesaved": "0.000",
    "totaltreesaved": "0.080"
}

Now those people that know me will know I am no Java programmer but even I recognised that as a JSON object. Just to check I fed it into the JSON validator at http://jsonlint.com/ and my suspicion was confirmed. 

Now I was a little disconcerted that I was able to pull the information so easily without even having to authenticate in any way with the GoodWe portal but at least it would make this a lot easier. I now had a way of getting the data I needed from the portal. Now I just needed to get it into my Domoticz system.

Domoticz has an events system that is powered by Lua scripts. I won't go into the pains I worked through learning how to put together my first Lua script. Lua is fairly well documented elsewhere but what it boiled down to was this. 

1. I needed to make a call to the URL and capture the string returned.

2. I then needed to cast this string into a JSON object for easier access.

3. Next I need to pull the information I want to capture from the JSON object.

4. Finally I needed to put that information into Domoticz.

Suffice it to say that every step was painful for the inexperienced Lua scriptwriter that I am. However with the help of my good friend google. This is what I came up with I hope it is of some help to someone else out there.

-- Script to pull GoodWe power generation data into Domoticz

-- Written by M Grimwade 2015

-- Function to update a Domoticz sensor object

function update(device, id, power, energy)

      commandArray[1] = {['UpdateDevice'] = id .. "|0|" .. energy}

   return

end

-- Command array to populate with Domoticz instructions

commandArray = {}

-- The switch ID of my device in Domoticz

switchIdx = 50

-- Load the JSON Lua module

JSON = (loadfile "/home/pi/domoticz/scripts/lua/JSON.lua")()

-- Reference the HTTP module enabling web calls

http = require 'socket.http'

-- Perform an HTTP request to get the raw string from the REST endpoint

html = http.request 'http://www.goodwe-power.com/Mobile/GetMyPowerStationByUser?username=mGrimwade'

-- Decode the JSON formatted string to a Lua table

local t = JSON:decode(html)

-- Pull out the sub table containing the data from the main table

local t2 = t[1]

-- Get the currentPower value from the sub table into a string

local currentPowerStr = t2.currentPower

-- Check the length of that string

local currentPowerLen = string.len(currentPowerStr)

-- Trim off the Kwh from the string and cast it to an integer

local currentPowerKwVal = tonumber(string.sub(currentPowerStr,1,currentPowerLen-2))

-- Multiply the Kwh value to get the wh value

local currentPowerWVal = currentPowerKwVal * 1000

-- Call the update function to add the data to Domoticz

update("Usage", switchIdx, currentPowerWVal, currentPowerWVal)

return commandArray