Alternative Energy Demystified, 2nd edition

Stan Gibilisco

Explanations for Quiz Answers in Chapter 1

1. According to the chapter text, one British thermal unit per hour (Btu/h) represents 0.293 watts (W) of power. Therefore, 40,000 Btu/h represents 0.293 x 40,000 = 11,720 W. That's 11.72 kilowatts (kW). The correct choice is C.

2. By definition, one calorie (1 cal) of heat energy warms up one gram (1 g) of pure liquid water by one degree Celsius (1ºC) if none of it vaporizes in the process. Conversely, if 1 g of pure liquid water cools down by 1ºC without any of it freezing in the process, it gives up 1 cal of heat energy. The correct choice is A.

3. When we want to quantify the rate of energy expenditure at any particular moment in time, or averaged over a period of time, we must use units of power. Of the options given here, only the kilowatt expresses power. The answer is D.

4. Corn stoves are designed to burn only shelled dry corn. Any other form of corn, or any other fuel type whatsoever, won't burn well in a corn stove. The correct choice is B.

5. The sensitive electronic systems in a pellet stove (and also in a corn stove or a high-end coal stove) can malfunction or even fail outright in the event of a voltage "spike" on the utility power line. Such "spikes," called transients, can be blocked (in most cases) by the installation of a transient suppressor in the AC power cord leading from the utility outlet to the stove. The correct choice is B. You might think that choice A, a rechargeable backup battery, would work. In fact, A does represent a valid option if you never directly operate the stove from the AC power source, but only from the battery when it's not connected to the charging unit (which gets its power from the AC utility line). However, few if any stove users would do that, unless they got all their electricity from an off-grid source such as a solar panel or wind turbine. Choice B is the best answer to this question.

6. An old-fashioned wood stove, designed to burn cut wood logs, offers a home heating option that doesn't need any source of power other than its own fuel. Wood pellet stoves or corn stoves have blowers and augurs (motor-driven feeding devices) that need electricity to work. The correct choice is A.

7. You can vent a gas furnace and a wood stove into the same chimney only if the chimney has two flues. You'd use one flue for the gas furnace and the other flue for the wood stove. The correct choice is B.

8. As power is expended, disspated, or transferred over a period of time, we end up with energy. Remember, energy equals power multiplied by time; power equals energy per unit time. Of the four choices given here, only joules quantify energy, so the answer is C.

9. A catalytic converter improves the efficiency of a wood stove by deriving some extra energy from the particulate matter (that is, from the smoke). In so doing, the catalytic converter reduces the amount of particulate matter that gets into the air. The correct choice is D.

10. Coal stoves are normally designed to burn deep-mined anthracite only. You shouldn't try to burn anything else in one of these things, unless the instruction manual specifically says that you can. The answer is A.