Alternative Energy Demystified, 2nd edition

Stan Gibilisco

Explanations for Quiz Answers in Chapter 8

1. A single proton-exchange-membrane (PEM) fuel cell provides approximately 0.7 volts DC. When we connect electrical cells of any sort in series (end-to-end or plus-to-minus, like the links of a chain), their voltages add up. Four PEM fuel cells in series will therefore produce 0.7 x 4 = 2.8 volts. The correct choice is B.

2. A regenerative braking system takes some of the energy that would normally heat up an EV's or HEV's brakes during periods of deceleration, and redirects that energy to a generator and AC/DC converter to charge the battery. As a result, the battery lasts longer than it otherwise would before a recharging stop becomes necessary. The additional electrical energy gives the electric motor a better opportunity to offload some work from the internal-combustion engine in an HEV, so indirectly, regenerative braking can improve the gasoline mileage in an HEV. The correct choice is D.

3. In order to to recharge a storage cell or battery, we can connect a source of DC voltage directly to the cell or battery terminals. We must make sure to connect the positive terminal of the external source to the positive terminal of our cell or battery, and the negative terminal of the external source to the negative terminal of our cell or battery. If we accidentally get the connections mixed up, we will in effect short out both the battery and the external DC source. At best, that error will damage the cell or battery. At worst, the cell or battery could rupture, catch on fire, or explode! The correct choice is B.

4. If we burn a mixture of pure hydrogen and pure oxygen, we get energy along with water (H2O) in the form of vapor. We don't get anything else if we use pure gases in the optimum proportion (two hydrogen atoms for every oxygen atom). The correct choice is B.

5. Engineers have suggested all three of the methods noted in choices A, B, and C as possible ways to extract pure hydrogen gas from natural sources. The answer is D, "All of the above."

6. Memory drain can make you think that a nickel-cadmium (NICAD) cell or battery has "died," when in fact you might "revive" it by running it through several charge/discharge cycles. Memory drain will never cause a battery to produce too much voltage, or to generate AC, or to burn, rupture, or explode. The worst thing that memory drain can do is make you discard a cell or battery that still has some useful life. The correct choice is C.

7. In a fuel-cell vehicle (FCV), the fuel cell plays the same role as the storage battery does in an electric vehicle (EV). A fuel cell can't function as an alternator, so choice B won't work. While a fuel cell is in some sense a generator of power, it doesn't play any role in a hybrid electric vehicle (HEV), so choice A is wrong. The correct choice is C.

8. In a series type hybrid electric vehicle (HEV), an electric motor always provides the propulsion. An internal combustion engine does exist, but it serves only to power a generator that keeps the electric motor's battery charged. The internal combustion engine doesn't directly contribute to the vehicle's drive system. The correct choice is A.

9. In cold weather, an air-source heat pump can help keep the interior temperature tolerable in an EV. The correct choice is A. You might think, for a moment, that choice B would make sense; all engines (or motors) produce a certain amount of heat because no such device exhibits 100-percent efficiency. However, the amount of heat generated in that way wouldn't warm up an EV interior by much. The residual-engine-heat scheme works with gasoline- or diesel-fueled vehicles in part because those engines are less efficient than the electric motors in EVs, and in part because the internal-combustion engines are a great deal more powerful than the electric motor in a typical EV. Choice C does not work at all! A space heater would quickly drain the battery. Choice D offers some interesting possibilities, but nobody has taken advantage of that scheme yet. Again (at least as of this writing), the answer is A.

10. If we connect multiple identical electrochemical cells in series, we'll end up with a total voltage equal to the sum of the individual cell voltages. The maximum deliverable current won't get any greater than a single cell would provide. The correct choice is D.