Alternative Energy Demystified, 2nd edition

Stan Gibilisco

Explanations for Quiz Answers in Chapter 4

1. Any of the three options described in choices A, B, and C will minimize or eliminate color-fading problems that go along with passive solar heating. Double-pane or triple-pane windows, cheap rugs, and "couch throws" can all minimize color fading. So, of course, can opting out of passive solar heating altogether! The answer is D, "Any of the above."

2. All three of the choices A, B, and C make true statements with regard to passive solar heating. Some rooms can overheat if they get too much sunlight for too long a time near midday; you needn't spend a fortune to derive some benefit from the sun as a supplemental source of heat energy; the same windows that let in thermal energy during the daytime can also lose it at night (if you don't cover them with closed curtains or blinds). The correct choice is D, "All of the above."

3. In the winter, water can freeze inside flat-plate collectors at night or on cloudy days, damaging the panels and possibly also the system as a whole. The use of heat-transfer fluid in parts of the system exposed to the cold can prevent this trouble, because the fluid acts as antifreeze. The correct choice is A.

4. South Dakota (a state in the United States) lies entirely in the Northern Hemisphere at midlatitudes (approximately 45º north). If you want to build a passive-solar house in the Northern Hemisphere, you should orient the side with the most window area toward the south (equator-facing). The correct choice is B.

5. In South Dakota, a passive solar house should have the least window area on the northern side, because that's the side that faces toward the pole. The answer is A.

6. Even if the winter temperatures drop far below freezing, a passive solar heating system can function effectively if the midday sun gets intense enough, and if most days offer plenty of sunshine. The answer is C. Choice A is not only wrong, but impossible; no place on earth has days that remain two or more hours longer than the nights all year round. Choice B is wrong; snow on the ground improves the performance of a passive solar heating system by increasing the amount of solar energy that hits the windows. Again, the answer is C.

7. Because a significant part of a sidehill home lies below ground, radon gas can accumulate in the interior air in some locations unless the home has adequate ventilation. Long-term exposure to radon gas can cause serious health problems such as lung cancer. The correct choice is C.

8. Materials with high density (weight per unit volume) make the best thermal masses. Of the four choices given here, concrete has by far the highest density. A cubic meter of solid concrete weighs a lot more than a cubic meter of wood, plastic, or air! The answer is D.

9. In a system designed for home heating and that has a thermal-mass floor, that floor should be well insulated from the earth below to minimize the loss of thermal energy to the ground by conduction. You want the stored thermal energy to dissipate into the interior air, not into the earth under the house! The correct choice is B.

10. Ultraviolet (UV) radiation does most of the "damage" in the color-fading process. Glass is relatively opaque to UV rays. That's why, if you opt for passive solar heating, you can minimize color fading problems by installing double-pane or triple-pane windows. Incidentally, multiple-pane windows also help to keep your home warm at night, because they minimize conductive thermal-energy loss to cold outdoor air. The correct choice is B.