Kyoto – A Perspective (Part 6)

Posted on Sat 04/05/2008 by

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CURRENT POWER USAGE (Part One.)

In this piece and also in the following pieces, I’ll be introducing some things that are technical by nature, and some of you will probably not read on because of that. However, what I hope to be able to do is to keep that technical ‘stuff’ understandable, because I’d like you to have an idea of what actually happens in the production and distribution of electricity.

First, those of you in Pennsylvania, look at a picture of the Philadelphia skyline, and for you other readers, look at any picture of the New York skyline. See those tall buildings, hundreds (upon hundreds) of them. Those buildings are mainly where people work. Inside those buildings, there has to be bright lighting and there are work stations at most desks in nearly every room. There are elevators, rest rooms where the water and waste needs to pumped into and out of, rooms where people gather for lunch where there are refrigerators and microwave cookers. There are water coolers. Everywhere you look electricity is used inside those huge complexes. But try and open a window for some fresh air. You can’t. All the air in every one of those structures is conditioned, kept at the same temperature all year round for efficiency’s sake, the temperature varying in small increments only, as turn around time for the whole area of the building would be quite long indeed, and because of that, the compressors would be working overtime and that is where the expense mounts up in the cost of the electricity. So, on the top of every one of those tall buildings are cooling towers with huge compressors driving air conditioners and fans. Each one of those buildings consumes huge amounts of electrical power.

Everywhere you look as you drive to work, no matter where you work, be it on the ground or inside a building similar to one of those buildings, everything you see is powered by electricity. To run all of that, large power plants are required.

The electricity is produced in those large power plants something like this.

High pressure steam drives huge turbines that in turn, then drive huge generators that produce the electricity. That steam is heated in different ways. Coal is burned to heat the water, or with nuclear reactors, heat generated from that reaction boils water. That’s why when you see those huge power plants, they’re always close to rivers, so not too much of the generated power is used in pumping water long distances. The water is heated to steam, then pressurised to drive the turbine, that steam then going into ponds where it cools back to water and is then diverted back into the river. Those large round stacks you see at power plants dissipate steam, and the taller thinner stacks you see at coal fired plants are the smoke stacks from the burning of the coal.

When you think turbines, you think of a 747 engine. With power plants, those large turbines might be three times that size and even larger, and generators being driven by the those turbines even larger again. Keeping that size in mind, you can imagine the inertia they build up while in motion, and just how difficult it would be to make them go faster, or even to slow them down. So these really large plants supply what is called ‘Base Load’ power, and what I mean by that is this.

See those tall buildings. The air has to keep flowing in them all the time, so those conditioned air plants on the roof run all the time, as does nearly every electrical item in those buildings, and virtually every other building in every city or town, every building. Hence a large amount of electricity is required to keep all of that ‘humming’ along. This is what is called base load power. Power that is always required at a set level, plus or minus a small amount. The large turbines and generators run as close as possible to maximum virtually all the time, excepting regulated and carefully planned down time for servicing, when other plants take up the slack. To get those turbines running at a faster speed to generate more electricity requires a long lead time period, so they just hum along at virtually a set speed for most of the time, because that is how they are most efficient, and use less fuel in doing so.

When you all get in your cars to drive home each evening, you all get in the door, fire up the air conditioner or heater, turn on computers, or sound systems, TV’s, cooktops, ovens, microwaves, and for houses where both partners work, clothes washers and dryers. This sudden power surge when everyone arrives home around the same time provides what is called a ‘spike’ to the power usage. This period of time is called ‘Peak Power’.

Because those huge power plants take time to run up speed to generate more electricity, what is needed are smaller plants that can run up relatively quickly to provide this extra power, and that’s why there’s a lot of much smaller plants, and all plants are connected onto the huge overall power grid. These smaller plants, (and just for Pennsylvania alone, that’s nigh on 85% of the total number of the plants) can run up to higher speeds more quickly, and supply that extra amount of power to the grid to provide the extra for this peak power.

The rated output of each of the plants is given in Megawatts. (MW)

Base load power is provided by plants that are rated at 1000 MW or more. Those large single turbines can drive generators that produce 700 MW or more, and these are the ones considered to be base load plants. That’s why those larger plants that produce the big number power totals have two and three generators, whereas smaller plants have much smaller generators that can be quickly run up to higher speeds producing more electricity into the grid as those peak power times arise.

In the next piece I’ll go into further detail of power plants in Pennsylvania, but to keep your interest, it’s probably hard to believe that just in Pennsylvania alone, there are 177 electrical power plants.

KPPSTony