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Introduction Bit
Electricity is one of those
things which is pretty much compulsory these days. However, creating
it with coal, oil, gas or uranium involves using a resource which
will a) run out and b) produces various useless wastes, plus
some carbon dioxide - although certain bodies wish to inform
everybody that plants will be extinct before long so the carbon
dioxide will be useless too.
As this webpage is detailing
how to produce energy with minimal upset to these people we will
assume that their claims are entirely correct - although we may
upset them a bit by building things in order to generate electricity
and killing some plants in the process. We may also upset anyone
who is about to have, is in the process of having or has just
had a meal.
This is a case study, so it
is concentrating on one particular requirement. This webpage
is connected to the Wye Valley Railway feature. The case involved
is therefore on how to electrify the Wye Valley Railway without
using one of the four bad fuels.
Definitions:
- Wye Valley Railway (WVR):
the former railway along the Wye Valley between Monmouth and
Chepstow in South-East Wales, UK;
- Wye Valley: an area of
Outstanding Natural Beauty, filled with ruined industries, with
the River Wye running along it;
- River Wye: A long, fast-flowing
river running from Plynlimon (Mid-Wales) to Chepstow (South-west
Wales), via Builth Wells, Hereford and Monmouth. Noted for its
salmon and popular with canoeists. Also known as "the deceitful
stream". Journey from Ross-on-Wye to Chepstow is covered
on this page;
- Electrification: the process
of fitting a railway with the necessary equipment to provide
a train with electricity as it moves along the track;
- Bad fuels: the four fuels
which all modern children are taught to despise: coal, oil, gas
and uranium;
- Non-renewable fuel: a fuel
which will run out (generally before we become extinct): coal,
oil, gas and uranium;
- Renewable fuel: a fuel
which will be available forever or of which more can be created:
wind, tides, the sun, biofuels, hydrogen, water and geothermal;
- Pointless fuel: a fuel
which it takes more energy to create than it will produce: hydrogen
(unless created with a renewable fuel);
- Third rail: a cheap system
of electrification suited to low-speed stopping trains where
an additional rail is laid next to the two present on a standard
railway. Electricity is run through this rail at a relatively
low voltage (normally 750V) and trains pick it up through bits
of metal hung off the bogies called shoes. Minimal visual pollution;
- Overhead line (OLE): a
more expensive system suited to high-speed express trains where
wires are hung off supports about 16 feet above the rails. Electricity
is run through these wires at a high voltage and trains pick
it up through a complicated piece of metalwork on the roof called
a pantograph. The OLE is also called "the knitting"
and can be regarded as visual pollution.
So the Wye Valley Railway is
looking at a system of power which will produce minimal noise
and atmospheric pollution while in the valley. Trains tend to
be powered using steam, diesel or electric power. Steam and diesel
power are out, since they will indisputably produce noise and
atmospheric pollution in the valley. Steam power will also attract
tourists, which apparently damage the local area. Both have an
added inefficiency because they have to carry their fuel around
with them, while an electric train has its fuel generated somewhere
else. Theoretically, a coal-fired power station could be used
for this as long as it's outside the valley. However, this may
upset people who produce various computer models and demonstrate
that a cardboard computer does not withstand fire as well as
a real one, before producing a weather map which shows that,
in certain weather conditions, the waste from this power station
will drift over the Wye Valley, causing the trees to suffocate
in the carbon dioxide. Nuclear power is possible, but people
may wish to remember that this will then produce a large pile
of nuclear waste which will be put in a container which will
then be towed to Sellafield in Cumbria by a pair of diesel locomotives
built in the 1950s. Once at Sellafield this pile of nuclear waste
will sit in its box until somebody finds something that they
can do with it or in becomes inert. So we're looking at electricity
generated by a renewable fuel.
Electrification can be carried
out with batteries, third rail or OLE. Batteries need re-charging
at every stop (a lengthy process which will add at least an hour
to the journey time) and also add extra weight to the train which
needs to be carried around. Third rail is a "tried and tested"
technology which does not impose on the view but can have an
effect on the local population of people and animals. OLE is
a slightly younger technology (1880 rather than 1870) which can
be seen as unsightly and tends to be adversely affected by the
weather. The wires are harder to maintain and are not always
where you want them to be (though they tend to be sixteen feet
up in the air), while the supports are a hazard in the event
of a derailment. The third rail is always two inches from the
running rail and can be partially sheathed between wooden panels,
with gaps being provided for crossings and animal runs. Since
humans and animals tend to wander around a bit, however, it is
widely reckoned to be better to put the electricity supply sixteen
feet up in the air and assume it will stay there. |
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Theory bit
The next point is which system
to use to generate this electricity. Possibly the best place
to start is by laying out the vital statistics:
- Units: The measure of electricity
used on bills. This is worked out using a simple formula: kilowatts
x hours = units
- Our train will require 1,200kW
of energy for it to run on full power (1600hp).
- The train can return up to
20% of its power to the electricity supply when it puts on the
brakes.
- It is a second-hand train
and so the only on-board services are lighting, basic air conditioning,
automatic doors and a buffet serving warm tea.
- 400kW will be adequate to
maintain the schedule which allows 50 minutes for the journey
from Chepstow to Monmouth.
- During any given 1 hour period
there will be two trains drawing power from the system.
Any system which is used, therefore,
will need to provide 800kW per hour at a minimum, otherwise known
as 800 units - each train will consume nearly 7 units per minute.
Wind energy has a rotten press and is therefore probably worth
avoiding, whatever the benefits might be. Tidal energy is due
to be generated in vast quantities by the Severn Barrage, allowing
all local power stations to close, but there's no point in basing
a business plan around it since it isn't going to built - mostly
due to environmental opposition from environmentalists who prefer
coal-fired power stations to asking some birds to move. Hydroelectric
power can be generated either by building dams across the river
or (in faster rivers like the Wye) by sticking a turbine in the
middle of it, but this might interfere with the salmon and canoeists
(both of which are worth keeping happy as they might like to
use the WVR at some point), besides being too reminiscent of
the former industry. Geothermal energy is downright expensive
- if we could afford two holes through the Earth to suitably
hot rocks (one up, one down) we'd spend the money on re-opening
the railway from Monmouth to Hereford and compensating everybody
for using diesel trains on it. Hydrogen is a very bulky and flammable
gas or a very cold liquid; it is very common in universal terms
but is rarely found on Earth without an oxygen atom keeping it
company. The difficulty is getting the hydrogen out of this compound
(also known as water) without using four times as much energy
as you will get out when you burn it. The sun has a nasty tendency
to hide behind a raincloud and has not been tested on such a
scale as running a real railway yet.
That leaves biofuels, which
come in two forms, which we'll call waste and growth. Growth
is when you grow lots of plants and then mince them up into a
fuel which can be used to replace coal, oil or gas, depending
on how you do it. This takes up space which then cannot be used
for growing crops. Not much land is used for growing crops in
the Wye Valley anyway, but the other way of doing it is by growing
trees, chopping them down and burning them in place of coal -
which is supposed to be carbon neutral because all the carbon
in the tree has been taken out of the atmosphere. Burning, however,
produces other chemicals which are still produced whether you
burn coal or trees. Furthermore, the recently-felled areas can
be more unsightly than a carefully-hidden open-cast mine or demolishing
a colliery slag-heap.
Waste is much more efficient
- you take what is left over after everyone else has finished
with it - food waste, the contents of chip-fat-friers, garden
cuttings, excretement - and turn it into a fuel. For replacing
oil it has to be turned into a liquid, but this waste is at its
best when replacing coal, because you just dump it in a ten-metre
tall silo and leave it to rot. The resultant heat (which can
be experienced on a small basis by taking the lid off a ½m³
compost bin) can be used to boil water and generate electricity,
while the methane given off can be burnt to produce the rather
less potent carbon dioxide, as well as some more electricity.
Meanwhile, the sludge left over will either rot away altogether
if given long enough or can be used as compost and fertiliser
if it is of sufficient quality. There is also a small quantity
of water produced which would pay a visit to the sewage works.
The scientific name for this method of was disposal is anaerobic
digestion and it allows power to be produced until shortly after
people stop eating anything or going to the toilet - after which
electricity would not be required anyway, so there's no problem
with that.
If you wish to accelerate this
process slightly you replace the silo with an industrial incincerator.
Landfill produces methane, while burning produces carbon dioxide.
The incinerator leaves minimal waste, destroys everything immediately
(rather than slowly collapsing over the next 200 years) and does
not attract seagulls, rats or urban foxes. It is therefore already
more environmentally friendly than landfill. It is also more
desirable than the widely accepted process of cremation, which
has certain issues such as the mercury in tooth fillings and
the nasty toxins in the body. The incinerator can also consume
more stuff than the silo - pretty much all household waste apart
from glass and metal, which can be recycled in the UK. Paper
has been developing a habit of going to China for recycling -
burning it here is more efficient than burning oil to power the
ship to China.
Both options could theorectically
destroy your sewage, rather than needing it to rot until it looks
clean in a tank and then pumping it back into the river. The
Wye Valley Railway is lucky enough to run past two sewage works
(at Wyesham and Tintern) and these could either be joined by
a few silos sunk into an eight-metre-deep hole or replaced by
such a silo or an incinerator. Your body does not removed more
than a fifth of the available energy in your food, but a properly
built incinerator should manage about half. The electricity thus
generated would be very convenient for the railway without need
for it to zap along miles of pylons and could boost the local
power supplies. In return the railway could help transport waste
to the site. The presence of the sewage works eliminates claims
about smells or unsightliness and facilities to deal with the
sludge are already present if necessary. Any meat waste put into
a silo has to be fit for human consumption so it won't be a case
of leaving diseased meat rotting in a dark hole. The Wyesham
site, being very convenient for a large population and associated
shops, pubs and supermarket, could be useful for disposing of
large amounts of food which would otherwise have to go for landfill.
As any surplus electricity could be sold (and there will be savings
from not buying so much electricity if there isn't anything left
over) there could be a case for paying people for their rubbish. |
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Maths bit
Now the important figures.
For anaerobic digestion 1 tonne of waste will produce 250 units
of electricity; the system is already proven for taking food
to produce electricity in Ludlow, Shropshire. Therefore, for
general padding to the 800 units required per hour by the railway,
4 tonnes of waste will be needed per hour (1000 units - the remaining
200 can power the rest of the Wye Valley). For 18 hours of service
per day (06:00 to 00:00) some 72 tonnes of rubbish will be needed.
There are around 30,000 people in the area (10,000 in Monmouth,
10,000 in Chepstow, 5,000 in the Parish of Tidenham and around
5,000 in nearby villages) - if everyone in the area threw away
300 grammes of fruit, vegetable and meat waste each day this
would result in 9 tonnes of rubbish - about an eighth of the
required amount. Another three tonnes might come from pubs, restaurants,
industrial units, the schools and the supermarkets at Monmouth
and Chepstow; that would bring it up to a sixth of the total.
If the local authorities could
be persuaded to augment local landfill sites with a few of these
things, however, the populations of Monmouthshire and the Forest
of Dean plus associated shops, food places and industries would
provide 160,000 people (48 tonnes) with enough other developments
to bring the total up to somewhere closer to 55 tonnes.
If we could include grass cuttings,
pruned bushes, dead flowers, rotting sticks, decomposing leaves
and rotten logs then the totals for the Wye Valley and adjacent
parts of the Forest of Dean might get 20 tonnes. Adding sewage
might offer the equivalent of 30 tonnes. That's still nowhere
near the 72 tonnes, although all of Monmouthshire and the Forest
of Dean with sewage and garden rubbish might scrape up to that
figure.
The incinerator option will
take more waste, so we can allow one plastic bag, one newspaper,
100g of food waste, one plastic bottle, 200g of toilet stuff
and 100g of junk mail per person per day - about 500g. If 1 tonne
now produces about 300 units of electricity, 3.333 tonnes are
needed per hour are needed for the 1000 units per day. 18 hours
service now requires 60 tonnes per day and our population of
30,000 is producing about a quarter of that. Adding in the pubs,
restaurants, industrial units etc. might knock that up to a quarter
of the required figure. Monmouthshire and the Forest of Dean
brings it up to 80 tonnes, providing 20 tonnes (6000 units of
electricity) for the local community once the railway has taken
its cut, and including everything else might offer 95 tonnes
of waste.
Meanwhile scrapping the local
coal-fired power station (in East Newport) and replacing it with
a set of industrial incinerators adds another 150,000 people
in and provides an output of 45,000 units of electricity. Unfortunately
this is only 45 megawatts and the current power station produces
360 megawatts.
The problem with this idea
is that people really don't throw enough stuff away. |
Featuring information
from the BBC Radio 4 programme A Load of Rubbish (Episode
3 - broadcast on Wednesday 26th November 2008).
- >>>A Times comment
article on the subject>>>
- (written about a month
after this article, but we doubt he got it from here)
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