1 00:00:00,160 --> 00:00:03,440 Speaker 1: Audible dot com is the leading provider of downloadable digital 2 00:00:03,480 --> 00:00:07,160 Speaker 1: audio books and spoken word entertainment. Audible has over one 3 00:00:07,200 --> 00:00:10,080 Speaker 1: hundred thousand titles to choose from to be downloaded to 4 00:00:10,119 --> 00:00:13,640 Speaker 1: your iPod or MP three player. Go to audible podcast 5 00:00:13,760 --> 00:00:16,080 Speaker 1: dot com slash brain stuff to get a free audio 6 00:00:16,160 --> 00:00:18,560 Speaker 1: book download of your choice when you sign up today. 7 00:00:19,480 --> 00:00:22,759 Speaker 1: Welcome to Brainstuff from how stuff works dot com where 8 00:00:22,800 --> 00:00:33,880 Speaker 1: smart Happens. Hi. I'm Marshall Brain with today's question, how 9 00:00:33,920 --> 00:00:37,640 Speaker 1: does a hybrid car work? We're all familiar with gasoline 10 00:00:37,640 --> 00:00:40,120 Speaker 1: powered cars, and most people have heard about our scene 11 00:00:40,159 --> 00:00:43,920 Speaker 1: electric cars. A hybrid car is a combination of the two. 12 00:00:44,560 --> 00:00:48,159 Speaker 1: Hybrid vehicle contains both a gasoline engine and an electric 13 00:00:48,240 --> 00:00:51,279 Speaker 1: motor in an attempt to get the best of both worlds. 14 00:00:51,800 --> 00:00:54,440 Speaker 1: The best way to understand the advantages of a hybrid 15 00:00:54,520 --> 00:00:56,840 Speaker 1: vehicle is to think about a car traveling down a 16 00:00:56,920 --> 00:01:00,800 Speaker 1: highway at the postage speed on level ground. In this case, 17 00:01:00,880 --> 00:01:05,160 Speaker 1: the engine is doing three things. First, it's overcoming rolling 18 00:01:05,160 --> 00:01:09,240 Speaker 1: resistance in the drivetrain. Second, it's overcoming air resistance, and 19 00:01:09,360 --> 00:01:13,160 Speaker 1: third it's powering accessories like the alternator and the air conditioner. 20 00:01:13,800 --> 00:01:16,200 Speaker 1: The engine might need to produce no more than twenty 21 00:01:16,200 --> 00:01:19,319 Speaker 1: horse power to carry this load. The reason why cars 22 00:01:19,360 --> 00:01:21,920 Speaker 1: have a hundred or two hundred or three hundred horsepower 23 00:01:21,959 --> 00:01:25,840 Speaker 1: engines is to handle acceleration from a standing stop, as 24 00:01:25,840 --> 00:01:29,039 Speaker 1: well as for passing and hill climbing. We only use 25 00:01:29,120 --> 00:01:32,679 Speaker 1: the maximum horsepower rating for one percent of the driving time. 26 00:01:33,160 --> 00:01:35,440 Speaker 1: The rest of the time we are carrying around the 27 00:01:35,480 --> 00:01:38,400 Speaker 1: weight and friction of that much larger engine, and that 28 00:01:38,440 --> 00:01:41,840 Speaker 1: wastes a lot of energy. In a pure hybrid vehicle, 29 00:01:42,200 --> 00:01:45,679 Speaker 1: you have a complete electric car. It includes an electric 30 00:01:45,720 --> 00:01:48,520 Speaker 1: motor to provide power to the wheels, as well as 31 00:01:48,560 --> 00:01:52,280 Speaker 1: batteries to supply the motor with electricity. Then you have 32 00:01:52,360 --> 00:01:56,840 Speaker 1: a completely separate gasoline engine powering a generator. The engine 33 00:01:56,880 --> 00:02:00,560 Speaker 1: is small, perhaps only twenty horsepower, and it's designed to 34 00:02:00,640 --> 00:02:04,800 Speaker 1: run it just one speed for maximum efficiency. The purpose 35 00:02:04,880 --> 00:02:08,400 Speaker 1: of this small, efficient engine is to provide enough power 36 00:02:08,520 --> 00:02:12,720 Speaker 1: for the car at its cruising speed. During times of acceleration, 37 00:02:12,800 --> 00:02:16,280 Speaker 1: the batteries provide the extra power necessary. When the car 38 00:02:16,360 --> 00:02:20,720 Speaker 1: is decelerating or standing still, the batteries recharge. This sort 39 00:02:20,720 --> 00:02:23,880 Speaker 1: of hybrid car is essentially an electric car with a 40 00:02:23,960 --> 00:02:27,960 Speaker 1: built in recharger for longer range. The advantage is that 41 00:02:28,000 --> 00:02:32,239 Speaker 1: the small, efficient gasoline engine gets great mileage. The only 42 00:02:32,320 --> 00:02:35,800 Speaker 1: problem with this traditional hybrid car is the weight. The 43 00:02:35,880 --> 00:02:38,680 Speaker 1: car has to carry the weight of the electric motor, 44 00:02:38,720 --> 00:02:42,600 Speaker 1: the generator, the gasoline engine, and the batteries. You don't 45 00:02:42,639 --> 00:02:45,240 Speaker 1: need as many batteries as a pure electric car, so 46 00:02:45,280 --> 00:02:48,600 Speaker 1: that saves some weight, but a full size electric motor 47 00:02:48,720 --> 00:02:52,520 Speaker 1: plus a ten kilowatt generator can weigh several hundred pounds. 48 00:02:53,000 --> 00:02:56,680 Speaker 1: Most hybrid vehicles, therefore, try to strike a compromise. They 49 00:02:56,800 --> 00:02:59,960 Speaker 1: use a larger gasoline engine that's connected directly to the 50 00:03:00,080 --> 00:03:03,480 Speaker 1: drive train, along with a smaller electric motor attached to 51 00:03:03,480 --> 00:03:07,440 Speaker 1: the engine or the transmission. The gasoline engine provides most 52 00:03:07,480 --> 00:03:10,840 Speaker 1: of the car's power, with the electric motor adding extra 53 00:03:10,880 --> 00:03:14,840 Speaker 1: power is needed for acceleration. Because the electric motor can 54 00:03:14,919 --> 00:03:17,880 Speaker 1: double as a generator during breaking and only has to 55 00:03:17,960 --> 00:03:20,560 Speaker 1: run part of the time, it can be extremely light. 56 00:03:21,080 --> 00:03:24,520 Speaker 1: The disadvantage of this approach is that the gasoline engine 57 00:03:24,600 --> 00:03:30,000 Speaker 1: must run at varying speeds, which reduces its efficiency. 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