BUILDING A BACKYARD POWERPLANT

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108 Garfield Avenue, Madison, New Jersey 07940

One of the first things that I do when my copy of 'The Iron-Men Album' arrives is to read Soot in the Flues. In that way I get a good idea of just what it is that the readers are thinking about. Almost every issue in the past year or so has had letters that deal directly or indirectly with the reader's concern with the high cost of things and usually end up with, 'Why can't we..........'

Well, usually there is a good reason. A specific case in point was a letter from David W. Jones (IMA November, 1980, pg. 12) on small power generators in the energy crisis.

I've put together a piece that should answer that and allied questions.

Skyrocketing prices of everything we buy only serves to increase our frustration as we cast about for ways to stop the flow of our money. As ardent steam engine enthusiasts it is only natural that we look to our hobby for answers. All of us have given at least a little thought as to how we might generate our own electric power. There is that old 6 horsepower Case that has seen many shows but could it be put to use in making the lights burn in the house? Let's take a look at what is involved and see if we really could save some money.

Naturally, in doing such a general inquiry as this is going to be, there have to be some assumptions made. We can start out by assuming that we have a traction engine boiler and a reciprocating steam engine to drive an electric generator. Maybe we will have to buy a second-hand generator but then that would be something to tinker with. And, if we are careful, our nose shouldn't light up if we get the wires crossed. We will need fuel and quite a bit of it. That is going to be a key item so we had better think about that quite thoroughly. There is the wood lot up on the hill. But maybe we had better figure on coal. Government 'experts' down in Foggy Bottom say that a good grade of eastern low sulfur steam coal is going to cost around $42.25 in the year 1985. That is a good starting point. Since it is a good coal it should have about 13,000 Btu per pound.

The old boiler has been hydro-tested at 225 pounds pressure so we'll figure on running it at 150# safety setting. Dry and saturated steam at that pressure contains 1192 Btu per pound and we can figure that the steam engine at that pressure and exhausting to atmosphere will run at 31.7 pounds of steam for every killowatt-hour of power that it makes. So that says that we need 37786 Btus in the steam. But, unfortunately, that firetube boiler without air heaters or economisers isn't so very efficient, maybe, say 75% efficient. That means that we are going to fire 50,380 Btu of coal for each unit of power. Taking the price of coal into account means that our power is going to cost us about 8 f per kilowatt-hour for just the fuel alone. Most homes use from 500 to 1000 kilowatt-hours per month. But it is the unit cost that we have to look at.

Around the country the cost of power to the homeowner varies quite a bit. But most of us live in areas that run between a low of 4C and a high of 8 f so it doesn't look too encouraging for the 'backyard power plant' operator.

If we have to dig down and spend some hard cash for some items, that is going to hurt the project too. To make it simple let us say that we need to spend $1000. Now that $1000 could have been in the bank drawing 10% in a certificate of deposit so we better charge ourselves for that. Here is how we do it.

A good figure for the demand that a home puts on a power plant is 5 kilowatts or 6% horsepower. But a home doesn't use that demand all of the time, only about 20% of the time on average. So if we multiply our $1000 by 10% interest and divide by the 5 kw demand and the 8760 hours in a year and also divide by our 20% load factor and keep our cents and decimals straight we see that that comes out to be about W/kilowatt-hour. That is, for every $1000 spent to make the project work, we should add If to our cost of power. And, somebody has to fire the boiler any time that we need power, like the next time that the refrigerator starts up.

Maybe now we have come to the point where we conclude that perhaps we should let the power company do the work. We will still rig up the old outfit to generate power but just for the fun of it.

The next time that the electric company sends you a bill take a good look at it. There will be a figure for how much you owe them. Now that figure you are accustomed to looking at, but also look at the number of kilowatt-hours that you have used. Take an old envelope and a stub of a pencil and divide one by the other and see how much you are paying per kilowatt-hour. Most likely half of that will be for just the fuel alone. Thirty percent will be to pay back the people that provided the equipment and to pay the interest on the money the company borrowed and just a modest amount to the people that put up the risk capital. Don't forget Uncle Sam, he gets his cut. In fact, he gets about as much as the risk taker and Uncle doesn't take any risks. The people who toil at honest labor and who provide all of the supplies and services get the remaining 20%.

We are frustrated and angry and tend to strike out in all directions to vent our rath, but doing the job ourselves is really not the answer. The answer lies in more fundamental things about our economy. I am an engineer, not an economist or a politician, so I will let you pursue that angle on your own.