On Saturday, local farmer Russell Price opened the doors of his farm to the people of Cropwell Bishop.
Not so many years ago that would have meant holding lambs, milking cows and watching a tractor ploughing. However, in the 21st century, if a farm is going to survive as a business it has to make the most of every opportunity to use its assets in new and enterprising ways.
So now, as well as supplying the general public with crops, Russell is supplying it with electricity. The big domes and buildings sited by the A46 are linked by pipes, ducts and wires and it is continuously feeding electricity into the National Grid—a bit like those people with solar panels on their roof, only on a much bigger scale.
Its output is 1 Megawatt, 24 hours a day. That is enough to power 300 electric kettles continuously, day and night.
Other aspects of the site are still under development but the goal is to make use of every joule of energy that enters its gates in the most productive way.
I was at the site for only an hour or so on Saturday but while there I saw at least 50 people being taken around the site by knowledgeable guides. Mick was the guide for our group and I have to confess that I didn’t grasp all the science of the system, but hopefully I learnt enough to pass on to you some understanding of how it all works. First, a bit of history.
Allesandro Volta was an Italian Physicist who was born in 1745. His fame lives on because the unit of electrical potential difference was named after him, i.e. Volts.
In the year 1776, while Americans were having a party and dumping tea into the docks at Boston and declaring they wanted to be independent of England (no time for referendums in those days), Volta was on holiday on Lake Maggiore in Italy, and his boat went alongside some reeds.
He began to poke the muddy bottom of the marsh beds with a stick and saw lots of gassy bubbles floating up to burst on the surface. He collected some of this gas and discovered it was inflammable. He called it “marsh gas”: nowadays we call it methane.
The bubbles of methane from the bed of Lake Maggiore were produced by decaying plants. Micro-organisms (bacteria) feed on the plants and produce methane as a waste product. These particular bacteria are able to feed on the decaying plants without needing oxygen. For this reason, we call them, ‘anaerobic’ bacteria (‘anaerobic’ means ‘living in the absence of oxygen’).
Russell’s site is based on the same principle. Everything is geared up to getting the maximum methane from dead plants (well any organic matter) using the least amount of energy. He has to use some energy to operate electrical machinery and to keep his tanks warm but he still has enough surplus energy to power the two giant electric generators.
This is how the system works:
Raw material (plant stuff, etc) is stored under covers for several weeks
Then it is loaded into a giant mashing machine
The resulting mush is then pumped into a tank where it is stirred up and warmed until it is ready to be pumped into the first digester.
There, the temperature is made just right (50 deg C) for the bacteria to get to work and release methane for several days.
This is all very useful but it is possible to get additional methane from the material by following up with a second kind of bacteria. However, these secondary bacteria live at a higher temperature so the mush is then pumped into an even bigger digester at 80 deg C where yet more methane is released.
Eventually, the methane gas is fed to the engines that turn the generators that feed electricity into the National Grid.
For everything to run smoothly, it is essential that timings, temperatures and other settings are carefully controlled and they are all displayed on the computer screen in the site office.
If something needs adjusting when there is no one on site, that is not a problem; the managar gets an alert on his iPhone and can make any changes from his phone.
The principle on which the plant is based is relatively simple but then, so is the principle behind a nuclear power station. Making the whole thing work smoothly has taken years of development by the companies that supply the equipment.
Below are a few photos from the open day. Many thanks to Russell for the free coffee and cakes at the end.