Hackday - Group Solar Forecasts

Last week, I attended BrumPropHack - a hackathon in Birmingham which looked at problems with retrofitting homes to make them more energy efficient.

There were some great talks about the scale of the problem - both in terms of the number of properties which need improving and the cost of retrofitting. A bunch of teams showed off some impressive demos which aimed to tackle the issues.

My demo was reasonably simple and (I thought) quite effective. It displayed a satellite view of a street in the local area. By clicking on rooftops, virtual solar panels are added to properties. Click a button and it shows your community how much CO₂ they will save, and how much money they will make.

The demo worked (phew!) and received good feedback. For something built in a couple of hours, I'm pretty pleased with it. The way it works is...

• Draw an interactive map using Leaflet.
• Use ESRI's satellite images.
• A bit of JavaScript to detect click and draw a cool solar panel icon.
• The EU has a great and free API for calculating solar irradiance. So this sends a request for each panel giving its latitude and longitude.
  • TODO! At the moment, it assumes all panels face south. A future version should let each icon be rotated to the correct degree.
  • TODO! Each icon represents 4kWp of solar. A future version should let each panel size be defined individually.
• Use CORS Anywhere because making JS requests is hard now.
• Do maths to work out the total installed capacity.
• Do maths to calculate the CO ₂ value.
  • TODO! This is calculated as 0.256 Kg/kWh. I found that figure on a website. Might not be accurate for the UK.
• Do maths to calculate the cost savings.
  • TODO! It assumes 50% export at £0.25/kWh and 50% reduction in use at £0.50/kWh. That should be adjustable.
• Display a link encouraging people to sign up
  • TODO! Make the link go somewhere.
  • TODO! Display the cost to install - with suitable discounts for bulk buy.
  • TODO! Draw some pretty graphs
• Uses Picnic CSS to make it look pretty.

It is a rough and ready demo, but it does work!

The code is freely available on GitHub if you want to build something more useful with it.