Driving on Sunshine

Posted by Chris Tuppen on 26th May 2016


Recently, I spent a couple of nights in London attending Ovum’s Smart to Future Cities conference and had pre-programmed my house to suspend all heating. My wife, who was also away, unexpectedly had to return home in an un-seasonally cold spell. It was therefore quite fun, and very pertinent, to be sitting in a ‘Smart’ audience, get out my smart phone, remotely log in to my home computer and re-programme the heating schedule.

Having dabbled in electronics and computing all my life, it has been very rewarding to experience how information communication technologies (ICT) can deliver carbon reductions on the ground. I also like to walk the talk and over the years have wired up my house to be a ‘living lab’ of Internet of Things (IoT) sensors. The latest innovation has been to store solar electricity in my Nissan Leaf.

With over 7kW of photovoltaic panels on the roof of the house there is always more than enough electricity to cover the minimum base load. So, as soon as any surplus PV electricity finds its way onto the grid, it gets redirected into the hot water tank. In fact, it’s only on the most dismal of winter days that we burn any gas to heat the water. But on a reasonably sunny day, the hot water will be up to temperature by 10.30 and until recently, all that surplus solar electricity was going into the grid. Not that that is a bad thing of course; in fact quite the contrary, as it would most likely be displacing fossil fuel generation. 

However, it is always most efficient to use electricity as close to the point of generation as possible. So now, after the water has been heated, any surplus PV electricity gets redirected into my Nissan Leaf electric car. It only takes four to five hours of constant sunshine to charge the car and provide about 60 miles of driving range. 

This all provides a triple pleasure. First, is the pleasure of gliding along the road in near silence, second is that it’s amazingly cost effective and third is the satisfaction that driving on sunshine is truly emissions free.

elv graph

This chart shows a day with intermittent sunny intervals. Until 09.30, surplus PV power was being diverted to the hot water heater. During the remainder of the morning, the washing machine was on and there was insufficient consistent surplus power to charge the car. However, after midday the sun shone more consistently and there was more than enough surplus PV power to charge the car. After just three hours, the 35 miles worth of charge that had been used the day before had been replaced and the car was fully charged. After this point, all surplus PV power was exported.

In addition to the grid-connected PV, there are a further two panels that charge a 2kWhr battery storage system. This feeds a low voltage DC network that runs the computer and IoT technology, security lighting, and charges up our i-Phones, i-Pads and Kindles.

In effect, my house is a smart micro-grid and demonstrates, at a very small scale, what could be achieved at a macro level. A smart grid will make the most effective use of renewables and enable the decarbonisation of the transport sector, both of which will be essential if the UK is to meet its carbon reduction objectives and help deliver the objectives of the Government’s Modern Transport Bill announced in the 2016 Queen’s Speech.

Chris Tuppen is a Director of the Aldersgate Group, Managing Director of Advancing Sustainability Ltd and in 2008 initiated and co-edited the seminal report ‘SMART 2020 – Enabling the Low Carbon Economy in the Information Age’.