Last week we released our new smartphone app with an event at the House of Lords. The app showcases three important numbers: the carbon intensity of UK electricity; the EU and UK carbon prices; and the global atmospheric CO2 concentration.
We were fortunate enough to have three amazing speakers in Juliet Davenport (CEO, Good Energy), Lord Oxburgh (formerly Chairman of Shell) and Professor Chris Rapley (UCL, and formerly Director of the British Antarctic Survey). 

Professor Chris Rapley, Baroness Worthington, Juliet Davenport and Laurence Watson at the launch of the Sandbag App

Professor Chris Rapley, Baroness Worthington, Juliet Davenport and Laurence Watson at the launch of the Sandbag App – photo credit Phil MacDonald/Sandbag

Lord Oxburgh gave us an analogy, which I will try to paraphrase here:

Our atmosphere is like a bathtub. From the taps, instead of water, CO2 is pouring out. Many different taps are running at different rates, and the bath is filling up. The edges of the bath are not even, and as the bath fills higher, in places the contents begin to spill over and make a mess of the floor.
We can anguish about the uneven sides and the height of the bath, but ultimately the only thing we can do is to turn off the taps!

Our app shows which ‘taps’ are filling the bath when it comes to our electricity. It should be clear that the tap marked ‘coal’ is running fast.

Professor Chris Rapley recounted how as Director of the Science Museum, he put on a large exhibition titled ‘Atmosphere’ which covered climate science. While surveying visitors (already self-selected to be interested), the staff were dismayed to find a fairly patchy understanding of climate change. Professor Rapley remarked that the app ‘extends our senses’  [to carbon dioxide].  While he checks the extent of Arctic sea ice daily, now we can all easily check the UK’s electricity mix.

We include ‘embedded renewables’ like solar power and small wind farms that aren’t directly measured by the National Grid. Solar power on roofs where the energy is used by the building is often treated as demand reduction. Instead of counting it as renewable generation, it is often just taken off the total figure for energy demand. This is partly because the data is quite tricky to get hold of. Solar farms that are connected and feed into parts of the grid are sometimes included, but the National Grid does not directly measure either kind. Wind farms smaller than 50 MW are also not directly measured by the National Grid, and do not have to supply forecasts for their output.

Juliet Davenport, CEO of Good Energy and renewables advocate, approves of the inclusion of 'embedded renewables. She asked us to consider how the energy mix changes the energy price at different times. In particular, while the intermittency of renewable generation is well known and can be forecast in advance, outages from large power plants can cause the energy price to spike unexpectedly. We’ll think about how to show costs in our app in the future!


Someone queried why we were showing CO2 intensity including renewables when the electricity from those renewables was ‘owned’ by particular people.  If someone pays for the Renewable Obligation Certificates (ROCs) generated by renewables, they can then claim to be using exclusively green electricity. Examples include anyone on a ‘green’ tariff from an energy provider that surrenders ROCs equivalent to their usage.

Firstly, it should be noted that ROCs were implemented to incentivise renewables across the UK. Energy suppliers have an obligation to purchase a certain amount of ROCs per unit of energy supplied to customers (hence renewables obligation). This stands currently at 0.29 ROCs / MWh supplied and the buy-out price per ROC is £44.33. The buy-out is paid if the supplier does not have enough ROCs to meet their obligation.

While users supporting renewables by consuming ROCs along with their power can claim they alone are using the electricity generated, this is just one way of thinking about the energy supply. At any one time a mix of energy sources make up the electricity that goes through the grid and out of a power socket. The app shows that breakdown. Regardless of whether or not energy customers have paid a top-up to support (and claim) renewables, they are getting a mixture of energy generation.

Here’s an analogy from me:

Picture yourself sitting on the bank of a broad river, gently but inevitably meandering past you. Alongside, dangling willow trees tickle the surface of the water. Upriver you can see a stream from a fresh mountain spring joining the current, adding bright clean water to the mass.
You know the stream well, because you have a claim on the water that flows from it. You have supported and cherished that stream from the high mountain spring, and you happily dip your cup into the main river, enjoying the prospect of some clean water.
But wait…. you look more closely at the river and see that it is really quite polluted and dirty. It doesn't look so good to drink after all. 

A confluence – a (clean) tributary joins a dirty river. By pushkar v on Flickr

It is totally right to support low-carbon energy as an end-user (I pay a green tariff from Ecotricity, Good Energy and others have them too).  However, this app is showing the energy supply picture for the whole of the UK, and most of the time, we are drinking a lot of pollution!

Change at the margins

I have been a little guilty of talking up the potential of demand-side response with our app's forecasts of grid intensity. You can hear me talking about this on the BBC World Service. How much CO2 could be saved if we used electricity when it is cleanest? How much CO2 could be saved if our demand was smoothed perfectly, so there was no need for peak-time extra generation? Probably quite a lot.

Some of our electricity sources run roughly the same all the time (nuclear, some interconnectors); some run intermittently but regularly (wind, solar), and some fill in the gaps to meet demand (coal and gas). If the clean electricity is fully utilised, extra demand (e.g. your washing) now or later will be met by either using some pumped storage or by adding some fossil fuel generation.The marginal extra carbon intensity of supply to meet the extra demand is largely determined by whether the fossil fuels that come online to help you do your washing are coal or gas. That is an extremely complicated question to work out, one that energy companies put a lot of time into. 

To continue build-up of renewables, we need to make sure that when they run they are fully utilised. Therefore we want to align high demand with times of high renewable generation. Our app is a good way to align energy use with renewable generation because we're including those embedded renewables as well for CO2 intensity. It's definitely a great way to engage with our energy system and to track of the carbon price, and global CO2 concentration.

Find the app download links here and we hope you enjoy using it.