Raw Heat to Refined Heat
In previous columns, I have looked at how to compare energy costs and touched only too briefly on the stages of refinement that energy can undergo to improve its application.
The subject of this column was prompted by a book: The Bottomless Well: The Twilight of Fuel, the Virtue of Waste and Why We Will Never Run Out of Energy, by Peter W Huber and Mark P Wills. Although this is not a book review, I must say this is a fascinating book: In some chapters, it is an undisciplined ragbag of rich and heavy reading; in others, a model of clarity and realistic analysis.
The authors bring credibility in the energy field to ideas that our green activists perceive as heresies and attacks on sustainability (whatever that means). To their credit, the authors make good use of the kilowatt hour (KWH) as the easily grasped unit of energy. If you use a 1-kW toaster or hair dryer, you've got the feel and look of the kilowatt. Leaving it on for one hour consumes 1 KWH and (at 2005 prices) you've spent typically 10 cents.
It's all the same stuff, but the authors jump around to the British thermal unit (BTU); then the quad, being a quadrillion (1015) BTU; then, the MMBTU, using the antique M, or 1,000 from Roman times. But look out! In this context in North America, these two Ms are reckoned to make a million, not 2,000 as in Rome. Look out again! M makes a million in the current usage of MW (megawatt) for 106 W. On other pages, the authors favor 10,000 Pontiac automobiles as a unit of power. While we are tossing these terms around, beware of confusing power (kW) with energy (KWH).
Biomass, oil, natural gas, propane and hydrogen all have their place. That's for another day. Here I will focus on electricity.
Heat usage ranges vary widely, from coal in a 2,000 MW power station boiler to a few watts or milliwatts of highly refined needle-sharp coherent electromagnetic radiation (light) as in laser eye surgery.
Raw heat is very cheap but can be useless until it is refined to some degree. The price of coal converts to about $0.0048 per KWH at the generating station. Very tempting at the price but you would be hard pressed to put it to use in your process.
It takes a lot of plant, equipment and manpower to convert coal to electricity, and more yet to deliver it to you. If you are an industrial user, you could pay anything from $0.03 to $0.11 per KWH, depending on your location.
But what a deal! It comes hundreds of miles at the speed of light, entering your plant through a 0.5" or less copper cable, and it is highly usable, controllable and versatile. Its voltage stays close enough to its nominal value for lights, motors and most other uses.
Further RefinementIf you want a different voltage, use a transformer. Want tighter voltage tolerance? Use a voltage stabilizer -- or a true-power controller. This is often built into temperature controllers so that the controller’s power-output signal is obeyed precisely in the face of line-voltage or load-resistance variations. This is just one of the many energy-refining jobs that the silicon controlled rectifier (SCR) can do for you.
When you want to deliver heat into a product, apply your imagination to the variety of technologies in figure 1.
The diagram here comes Foundations of Electroheat by A.C. Metaxas. (I’ve reviewed this book in a previous Heating Highlights column; see archive link at bottom of page.) It shows a range of brilliant and inventive refinements of raw heat that enable it to perform miracles of application.
In the words of the author Metaxas: “The mechanisms supporting these processes are as diverse as the processes themselves: the flow of displacement and skin currents, dipolar reorientation, thermal radiation and convection and the conversion of kinetic energy of high-velocity particles to heat by collision with processed material.”
Refinement always comes at the cost of losing some of the energy on the way. 60 to 90 percent of the power you put into a laser system never gets to that blinding sharp beam of light that cuts cleanly through steel. Is it worth the cost per KWH plus the cost of the equipment? You bet.
If you are into power-hungry processing such as electrolytic metal refining, look hard at location. Your ore may be in an area -- even offshore -- where it may coincide with surplus and cheap energy because that location cannot demand world prices. Instead of asking for local subsidies in your area, you would release your electricity supplier to obtain market prices from willing buyers at home. PH