From Coal to Control: Flexibility Powers the Green Transition

As the UK’s last coal power station, Ratcliffe-on-Soar, closes, and the National Energy System Operator (NESO) opens, we’re at a profound turning point in our energy story.?But energy has always been a cascade of revolutions.?In particular, we’ve been trying to clean up coal since the day we started burning it.

The chimney was invented to draw smoke out of a building and pull air into the base of a fire. More air means better combustion which means less soot, and dispersing the smoke outside means the occupants aren’t choking on it.?The surviving blackhouses on the Hebrides are cherished, but no-one would choose to run those open, chimney-less fireplaces now.

The stove was the next enhancement. Combustion is a complex chemical reaction; enclosing it gives better control and higher efficiency, and better isolation from the nastier aspects of it.? You can also stick a cooking pot on the stove without turning it black.?

Fundamentally, however, the stuff coming out the top of the stack is the problem.?The very idea of an “east end” in a city is a product of coal, as prevailing winds sent the blight of pollution across the districts which, inevitably, would grow up as the poorer ones.?And so, as the industrial revolution matured, chimneys got taller and taller, seeking to disperse the smoke higher up and further away from the people who mined the coal, worked in the factories and bought industry’s outputs.?

When I first became involved in power generation, the big question was: how can we clean up that smoke? Climate change was known about but not talked about, and energy security was still about big power. The target here was acid rain.

Acids form in combustion gases from both sulphur and nitrogen, but sulphur is worse because it contributes to both reactions.?Logically, then, governments told generators to buy coal with less sulphur in it.?We would be na?ve to imagine that high-sulphur coal stayed in the ground thereafter.? Sometimes anti-pollution measures just move things around.?On the plus side, where a coal station was thought to have a decent number of years left in it, serious money was invested in taking the sulphur out of the flue gas. Ratcliffe was one of these.? Flue-gas desulphurisation (FGD) allowed, to an extent, the cheaper, higher sulphur coals to be used while pollution was reduced.

But nitrogen is in the air.? Preventing small amounts of it from oxidising in a flame means messing with the chemistry.? The trick is to leave the centre of the flame slightly short of air, so that the carbon and hydrogen atoms grab hold of the available oxygen, leaving none for the nitrogen. Then, the remaining air enters in stages, hopefully completing the combustion without giving the terrible trio of nitric oxide (NO), nitrogen dioxide (NO?) and nitrous oxide (N?O, or laughing gas) much chance to form.

This works to an extent, but it’s trouble.?The harder you push it, the more soot forms in the heart of the flame, and the less chance there is that it will all be oxidised at the end.?The first generation of low-NOx burners fitted to one (unnamed) coal power station “grew beards”, in the words of the (also unnamed) chemical engineer tasked with fixing the problem – car-sized lumps of partially-combusted matter formed in the furnace just under the burner mouths.? Low-NOx combustion did improve, and in fact it entered other realms such as diesel engines and gas turbines. But the fundamental compromise soon became clear: you can cut down on the health-affecting, smog-creating and acid-forming pollutants, but you will always pay a price in efficiency.?NOx goes down, CO? goes up.

Carbon dioxide is a weird pollutant.?We’ve always breathed it in and out.?In modest quantities, it does us no harm at all.?It can reach planet-killing concentrations long before it has any noticeable local effect. Coal is mostly made of carbon: the cleanest of all coals, anthracite, has virtually nothing else in it.?This paradox has bedevilled many energy discussions: is a gas boiler clean or not?? Is petrol better or worse than diesel? It always depends on what you are talking about (and don’t even start on biomass).?NOx comes back round to complicate things further: it’s locally harmful, but all flavours of it are also greenhouse gases.

This is why the well-known electric vehicle enthusiasts Robert Llewelyn and Quentin Wilson founded #StopBurningStuff.?No matter what the fuel, no matter how clever the combustion or how efficient the boiler, engine or turbine, the only way to truly clean up combustion is to stop doing it.? Hydrogen comes very close – but you have to make that. As a part-time boat-dweller and rural highlander, I am still burning stuff. So is the production of most cement, ceramics and primary steel.?Where there’s methane, its ability to cause climate change is many times greater before you burn it than after, which is why landfill gas, sewage gas and coal mine methane merit special treatment.?We may have stopped burning one particular kind of stuff in Nottinghamshire, but we are a long way from solving the whole problem.

Ratcliffe is major news.?If that’s where you live, its closure will change everything from the skyline to career prospects. But the NESO story is bigger still. There has never been a single organisation tasked with looking at energy across its breadth, responsible for everything from national and regional strategy to second-by-second operations.?The inclusion of heat in NESO’s remit may turn out to be the single biggest decision in national decarbonisation. Heat policy has had a wheel in the ditch for decades; consequently, the potential to make an impact is huge.? While National Grid ESO was responsible only for the 20% of energy that we consume as electricity, taking on board heat and the electrification of transport will ultimately give NESO’s responsibility for 100% of our energy. No pressure, eh?

Heat and electric vehicles have two things in common with Ratcliffe: storage, and flexibility.? Ratcliffe was one of those stations that would be ramped up and down by NESO’s Electricity National Control Centre (ENCC) to follow demand.?The mountains of coal sitting outside power stations once provided our biggest store of energy. Electricity cannot be stored in its native form, and the problem of balancing supply and demand in a largely renewable system has vexed engineers, inventors and politicians for a long time.?The formation of NESO puts a big part of the answer right into ENCC’s hands: heat is – mostly – easy to store, and electric cars are just batteries on wheels.?This is how green power can succeed as coal once did: by flexible consumers responding to weather, prices and events, right around the clock.

We’ve stopped burning coal, but while gas is still a baseload fuel, we haven’t finished.? To enable wind and solar to fill the huge gap that fossil power will ultimately leave, flexibility is going to be needed right across the demand side, with businesses of all scales joining householders in putting green energy to work. NESO has to co-ordinate that, and at Flexitricity, we’re determined to deliver it.

You can read the blog article here for more insights!