The Sutton Bridge power station, on the River Nene and the far boundary of the East Midlands, was interesting, and I wish I could have taken more photos. The tour guide, one of the few members of staff at the power station, said I needed to be sure my digital camera was “intrinsically safe”, which seemed to mean being rock solid certain that it would not make any sparks that could have ignited a cloud of gas that could have escaped. They were highly safety concious – as visitors, we were equipped with hard hats, safety goggles and steel-capped boots to change into, and as we were going round, many of the areas had sweet-dispensers near the door giving out ear plugs to safeguard our hearing.
The power station has two gas turbines, and the waste heat from each of them is collected, turns water into steam, and this steam drives a third turbine. Each of the turbines produces about 250MW, and whilst we were there the whole plant was producing about 740MW. Compared to nearby small town Kings Lynn, which has energy requirements of about 10MW that’s rather a lot of power!
Some fascinating facts:
- the plant uses in a second the amount of gas the average home uses in a year – 2% of the nation’s entire gas supply
- steam is 17,000 times greater by volume than water
- they use natural gas from the gas grid, but they take it out before the artificial smell is added
- the plant was about 54% efficient, which is apparently good
- They get through 100 tonnes of ordinary drinking water every day
The tour took us through through a demineralisation plant (ordinary drinking water has too much impurities in it to go straight into the process – when you boil it off to steam, what’s left behind would damage the boiler). We then followed various huge pipes around the plant to understand what was going on.
The whole system had various sizes of pipe from massive 5m diameter pipes containing all the steam to tiny pipes ferrying around compressed hydrogen. Every pipe in the place was colour coded, labelled (eg: STEAM, CONDENSATE (blue), FIRE WATER (red), OIL (sort of salmon coloured) COOLANT (green)) and had periodic arrows to show the direction of flow. Arranged against the bright red steel frame of the building, the whole thing was very colourful. Apparently, most tour groups are primary school children.
Our path through the plant took us around the outside to see where the gas was coming in (most interesting for the wildlife – hares and rabbits lolloping around the taps and pipework), around the back to see the cooling arrangements – square fans on stilts replacing the cooling towers you see at eg Ratcliffe on Soar.
Then we entered the main turbine hall – noisy, and hot, and getting hotter as we climbed through the levels. It was explained that each of the various parts – the turbines, the gas boilers, the generators, the control rooms – were modular units about the size of a container lorry. You build a shell of a hangar, 5 storeys high with 100ton cranes, and the modular units arrive, and you winch them into place and hook them up to your pipe infrastructure bringing in gas and water, and taking out power and steam. Exactly the same units are in use across the world. Presumably, should anything major fail, you could just switch out a faulty unit and replace it.
We were shown a basic control room where they showed us how the whole plant is started, by clicking on one button one monitor labelled “start turbine” – rather worryingly, the password for that terminal was stuck onto the top of the monitor with a sticky label!
The whole power station, which covered several hectares, and felt physically enormous, is routinely run by just three people. My sense of power stations from the previous tours I have been on as a child (I have toured a coal fired station and a nuclear one, but only have the vaguest recollections of either) was that there were lots of people involved. This one, with the fuel arriving by pipes with little intervention needed, was practically automatic.
Our tour took us through four different levels of the turbine hall, then out onto the steel frame around the HPSRGs (high pressure steam recovery… gubbins). Then we were allowed to climb up still further to the base of the chimneys, and I get the impression that if we’d asked (and if we hadn’t been beat!), we’d have been allowed to climb the chimneys themselves too. At this point we were tens of meters off the ground, standing on see-through steel walkways with the ground plainly visible below. We had a fabulous view over miles of flat, Lincs fields, could trace the route of the power cables from the station to the rest of the grid (just three cables out to carry those 800MW at 40,000V)
If you look at this picture, we were at the height of the highest red bars just under the thin parts of the chimneys.
When we were at the top, our guide noticed some concerning corrosion. And at other points around the tour, leaks and steam vents had also caused her to stop and write things in her notebook. I asked how you could make notes that said exactly where the problem was without sending engineers on a wild goose chase, and she pointed to metal tags fixed to pretty much everything of note. Every component, every tap, pipe, box, monitor, gauge etc has its own reference code, so recording those means you can send someone back to exactly the same point to check up.
The final thing we looked at at the top was a monitoring cabinet recording the flue emissions. There was no visible steam or smoke coming out of the stack, but the digital monitoring kit gave a reading to show just what was being pumped into the air. Practically no carbon monoxide. A staggering amount of carbon dioxide. Various amounts of NO and NO2 – isn’t that laughing gas (ah, no, that would be N2O not NO2)
Then back down the stairs to call in at the main control room – a large array of TFT monitors arranged in an arc – the visitors’ centre – brightly coloured kid-friendly information boards, then back to our cars, first changing back into our own shoes and leaving behind the hard hats and safety specs.
The day wasn’t over then, as we went on to Boston to meet a chaplain to discuss issues concerning migrant workers. But I will type that up another day!