Decarbonising the West of England

Zero West aims to coordinate and accelerate the transition to zero carbon in the West of England region. To inform its work, Tom Stedall and colleagues explored in detail what zero carbon in the West of England would look like. Here he gives us a whistle-stop tour of his research.

For the purposes of the work the ‘West of England’ comprises four Local Authorities: The City of Bristol, Bath & North East Somerset, South Gloucestershire and North Somerset. It’s a small region, containing the cities of Bristol and Bath, with a population of just over a million people. Outside the cities and town, the region is mostly farmland. Much environmental thinking in Bristol is city-focused but working on a wider area allows us to think in terms of a city and its surrounding country, and in terms of bioregions, and their significance.

Our model encompasses power, heat, and transport, which together cover just over half the emissions for which we are individually responsible. We allow for the requirements of a heat pump and electric car for each household.

We estimated how many renewables the West of England could support, with ambitious uptake of proven technologies such as wind and solar, as well as our ‘share’ of the contracted capacity of offshore wind – 43GW in total by 2030, an encouraging figure but still not enough. We considered energy from waste, biomass and hydro, though the potential for these is much less. We also estimated the existing renewable capacity in the West of England region, to show that the renewable potential was at least around five times current deployment.

We then used the Pathfinder model developed by Wales and West Utilities to model these renewables as an electricity source for the West of England region. Pathfinder is an hourly supply and demand matcher, which can calculate electricity demand against availability for every hour of the year, based on historical data.

Pathfinder provides a good picture of the challenges of an electricity system powered by close to 100% renewables, with current demand reduced by an ambitious third. Renewables aren’t always available when we need them, and we find, predictably, that at times there is a significant excess, while at other times, we would rely on imported electricity.

Key findings

The amount of excess electricity generated in our ambitious renewable scenario is approximately equal to the amount of electricity that needs to be imported to meet demand. If we could store this energy, we could ‘close the loop’, and be self-sufficient. The amount of energy is huge, approximately half a TWh, so storing it is a significant challenge.

However, firstly, utilising the electric vehicle fleet so that it charges when there is excess supply and discharges when there is excess demand can play a significant role in balancing the grid. Secondly, Wales and West Utilities have explored smart heat pumps that run when modest heating is required, but switch to gas when it’s colder outside, and heat pumps are less efficient. Gas can come from biomethane supplies or be manufactured from hydrogen (generated by excess renewables). Such a system can reduce electricity demand when it is hardest to meet (e.g.  on cold winter evenings or the last week, day or hour of demand). The idea of continual power supply may well have to change, according to this model, or be restricted to those with the greatest need.

Our work shows that there are solutions to closing the loop between intermittent renewable energy sources, and household demand. It involves more renewables, and demand reduction, but it also involves being smart about when we use energy, including recognising that at times we may not be able to take it for granted.

It involves smart systems, like smart heat pumps and utilisation of the electric vehicle fleet. It also involves a fundamental component of storage (critically daily and inter-seasonal). Hydrogen has huge potential, as it can integrate with various aspects of the energy system. It can be generated by electrolysis of sea water when there are excess renewables, used directly in fuel cells (for transport), injected directly into the gas grid (currently up to 10%, but likely to increase), stored and converted to methane or liquid fuels (for transport).

Last but not least, when we start thinking about a 100% renewable energy system, it becomes clear that power, heating and transport can make each other work, and need to be thought about as a single challenge. So far, we’ve only really made progress on power, but if we can address all three sectors, then we make substantial progress towards zero carbon.

Many models have shown that zero carbon is achievable, and we simply reiterate this in a local context. It is worth noting that it would be impossible to devise such a model for Bristol alone, and that it was working in the wider West of England region that made it possible.

At this stage, the work isn’t meant to be a detailed policy recommendation but is intended to inform conversation with policy makers and the public, and to contextualise possible developments. It is ultimately a thought experiment; whose lessons need to be enacted everywhere. There needs to be much more debate about the approaches (many in prototype phase) that can close the loop between majority renewable power and meeting demand, and how these require an entirely integrated approach to power, heating and transport.

We hope that the work we have undertaken will be a useful resource in working towards zero carbon and invite you to get in touch with Zero West if you would like to know more.

Blog by Tom Stedall