Launching Learn: Sustainable Energy

Over the years we have done a fair bit of work that explores sustainable energy documented to a varying degree on the site. The Sustainable Energy section of Learn brings all of this together in one place that’s easier to find and navigate as well as extending it with further improvements to the energy modelling tools, discussion and analysis.

New Front Page

It starts with a brief introduction and energy 101, which outlines the energy consumption of the average UK household and a quick run through the main demand and supply side solutions used by the ZeroCarbonBritain scenario:

There is then a brief write up of an energy study into 17 households in Snowdonia, North Wales that Glyn and I helped run in 2010 that illustrates how different energy consumption can be across a number of household. It uses the energy stack graphics style used by the sadly late David MacKay FRS who wrote Sustainable energy without the hot air, to visualise the different uses of energy from traditional electricity demand to heating and transport:

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New home page and Learn website!

As you may well have noticed we have recently launched a new front page for OpenEnergyMonitor and a common navigation bar theme across all our sites. We have also launched a new website called Learn to replace the Building Blocks section of the old site. All URL’s directed to building blocks should re-direct automatically to the relevant Learn page.


A key aim behind the redesign was to bring our interest and driving motivation of working towards sustainable energy and zero carbon more to the fore of the project. Energy Monitoring is a tool to help us understand our use of energy, and our motivation for starting the project was to understand our use of energy at home in relation to the wider context of what needs to be done if we are to get off fossil fuels and build a zero carbon energy system - We hope this update better reflects this interest.

This website redesign completes the shift away from using Drupal 6 cms that was started with the User Guide website launched April 2016 and a new Community Form using Discource launched May 2016. The old forums are still accessible as a read-only archive.

Alongside the new front page we have also launched a new website called Learn which includes what used to be called Building Blocks, resources for learning about AC Power Theory, CT Sensors, Measurement circuit design through to Timeseries data storage design.

Learn also includes a large updated section on Sustainable Energy which brings together and expands on our work on understanding the wider context, including a web-based 10 year hourly 100% renewable energy model based on ZeroCarbonBritain and resources on building energy modelling.

The new sites are all designed to be responsive for viewing on mobile as well as desktop screen sizes:

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OpenEVSE EV Charge Controller

OpenEVSE (recently renamed to OpenEV) design and build fully open-source EVSE (Electric Vehicle Supply Equipment) charge controllers for electric vehicles.

An EVSE charging station, is a device an electric car (EV) is plugged into to charge. It communicates to the car to agree on a charging rate that is the fastest and safest rate both the car and the power supply can support.

Update March 17: OpenEnergyMonitor and proud to announce that we are now the UK / Europe reseller for OpenEVSE charging stations, see OpenEnergyMonitor Online Shop.

openevse leaf

openevse build9

Note: this review is my account of using the OpenEVSE in the UK (240V single-phase AC), see OpenEVSE website for official build guides


The features that make the OpenEVSE charge controller interesting to us are:

I recently swapped my ageing diesel car for an all-electric Nissan LEAF (it’s fantastic), so it felt like the perfect time to build and test an OpenEVSE charge controller unit!

Nissan LEAF charging from solar PV on a frosty morning:


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Introducing emonTH V2

The emonTH V2 is an open-source, wireless, battery-powered temperature and humidity monitoring node.

The emonTH V2 features a Silicon Labs Si7021 temperature and humidity sensor instead of the DHT22 sensor. The Si7021 is more accurate and significantly (2000 times!) lower power then the DHT22. This will result in an increase in the emonTH battery life; from 10 months to several years (at least two years). The Si7021 is also much smaller than the DHT22.

emonTH V2

The Si7021 sensor can be seen in the top right-hand corner of the PCB. The white film on top of the sensor is a dust film and should not be removed. The dust film is factory fitted and will protect the sensor from dust and air contaminants.

emonTH image

The emonTH V2 is now shipping via our online shop

As with all our hardware units the emonTH V2 is fully open-source and manufactured locally in North Wales, UK using non-conflict materials lead-free processes.

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Summer Placement

Hi! My name is Eben I’ve been working with OpenEnergyMonitor for the past 10 weeks as part of a summer placement organised by Arloesi Gwynedd Wledig; a local project aimed at highlighting the local tech sector employment opportunities on Parc Menai the business park where we are located in North Wales, and the difficulties that they face, as well as the great perks of living in such a beautiful area.


The scheme organised placements for four students in four seperate tech companies in Parc Menai. Here is a video with highlights the whole 10 week scheme:

Working in a small company in a rural area, that has such a large online community has really opened my eyes to the possibilities that the internet and the digital age can offer, in that people are no longer bound to cities. Increasing infrastructure development in terms of roads and internet speeds has increased this mobility further, and I look forward to the growth that this will no doubt provide in Gwynedd. OpenEnergyMonitor is for me the perfect example of a growing business that has been made possible by opensource development, global connections and communities, and new technology.

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EcoHome Lab: From Monitoring to Control

Last night I attended EcoHomeLab meetup in Manchester organised by the CarbonCoop.

EcoHomeLab monthly meetups at MadLab brings householders and green-technologists together to take control of home energy use and generation.

It was great fun to catch up with regular faces as well as meet many new interesting people.

I gave a short presentation overview of our efforts as OpenEnergyMonitor to make it as easy as possible for people to get started with energy monitoring and control (home automation) with a sustainability / energy saving focus.

I presented the recent work we have been doing to integrate platforms such as MQTT, Node-RED and openHAB ready-installed and pre-configured on the emonPi, our RaspberryPi based energy monitoring platform. These additional platforms run alongside Emoncms on the emonPi.

See the Integrations section of our user guide for more info

Here are copy of my slides from the event:

HTU21D / Si72021 Temperature and Humidity Sensor

I have been been evaluating the HTU21D temperature and humidity sensor made by Measurement Specialties as a possible DHT22 replacement for the emonTH. This is quite a new sensor, released in 2013. The Si72021 is also a posiblity with an identical pin-out and specs.


The metrics speak for themselves:

Metric HTU21D Si72021 DHT22 DHT22 vs HTU21D Difference
Cost in 1k off £1.42 (July16) £2.15 £4.57 (July16) 3.2 times cheaper (£3.15 less!)
Vcc 2.1v - 3.6V 1.9V - 3.6V 3.3-6V  
Humidity accuracy ±2% RH ±2% RH ±2%RH n/a
Humidity Range 0-100% RH 0-100% RH 0-100% RH n/a
Temperature accuracy ±0.3°C ±0.4°C ±0.5°C 40% more accurate
Temperature Range -40°C +125°C -40°C +125°C -40°C +80°C 56% more accurate
Sleep Current 0.02uA 0.06uA 15uA 750 times less power
Measurement Current 0.045mA 0.09 mA 0.5mA 11 times less power
Measurement time 0.01s - 0.0026s 0.01s - 0.0026s 2s 200 times faster
Energy consumed per sample 1.5uJ 2.97uJ 3300uJ 2000 times less power
Time sampling per day* 14.4s   2800s  
Time sleeping per day* 86386s   83600s  
Energy consumed per day* 2.36mW [1]   2836mW [2] 1201 times less energy per day!
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Part 3/3: Continuous Deployment (Over-The-Air Update to ESP8266)

This post is part of a series

Following on from my last couple of posts in this series we now have a working continuous cloud-based build & test (firmware compiling) flow using PlatformIO and TravisCI, to quickly recap:

  1. Code change is committed to the EmonESP repo on GitHub
  2. TravisCI triggers a build (compile) using PlatformIO running in a TravisCI container in the cloud.
  3. If build/compilation process fails we get an email alert, if pull-request we get a warning before merging if proposed changes break the build.
  4. If a Git commit is tagged as a release the build process uploads the generated compiled binary (.bin) to the repo GitHub release page.

The next step is to get the compiled binary from GitHub-releases (EmonESP in this example) deployed to a WiFi connected production ESP8266. Here’s the user facing EmonESP web-interface for this firmware update process:


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Emoncms Docker

We have made the first steps towards running Emoncms to run in a Docker container.

Dockerfiles and setup notes are in the emoncms-docker repository:


Docker is an exciting tool to help make development, testing and deployment of web-applications easier.

What is docker? (the short version):

Docker containers wrap a piece of software in a complete filesystem that contains everything needed to run: code, runtime, system tools, system libraries – anything that can be installed on a server. This guarantees that the software will always run the same, regardless of its environment.

What is docker? (the long version):

Docker is an open-source platform for developers and sysadmins to build, ship, and run distributed applications. Consisting of Docker Engine, a portable, lightweight runtime and packaging tool, and Docker Hub, a cloud service for sharing applications and automating workflows, Docker enables apps to be quickly assembled from components and eliminates the friction between development, QA, and production environments. As a result, IT can ship faster and run the same app, unchanged, on laptops, data center VMs, and any cloud.

Quick Start

$ docker pull openenergymonitor/emoncms
$ git clone
$ cd emoncms-docker
$ docker-compose up

That’s it! Emoncms should now be runnning, browse to http://localhost:8080

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ESP8266 WIFI developments

Glyn and I have been doing a bit of development recently on using the ESP8266 WiFi board with OpenEnergyMonitor hardware, we are quite excited about the potential of this little module to both reduce the cost of the system and simplify setup and installation especially for applications that primarily post to a remote emoncms server such as

Note: we have no plans to discontinue developments and support for Raspberry Pi based systems e.g. emonPi / emonBase. Quite the opposite: the local storage and processing of a Raspberry Pi based system has many advantages particularly for systems requiring more flexibility and customisation e.g Local Emoncms storage. MQTT, openHAB & nodeRED integration. The ESP developments will be ran in parallel, in fact ESP could be configured to post to an emonPi / emonBase via MQTT for local on-site storage and integration.

We are at the moment working on three initial uses of the ESP8266:

1. EmonTx V3 + ESP8266 module

We are initially using the Adafruit HUZZAH ESP8266 module as a development platform. For anyone keen to get going with the ESP8266 Huzzah module it is available from a number of places such as adafruit (USA) and Pimoroni (UK). Any ESP8266 with ESP-12 module should work the same. See lower in the post for EmonESP firmware dev.


There will be another post very soon detailing how to use this module with the EmonTx v3.

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