LECTURER: Thanks, Leila. OK, can anyone tell me what advantages fuel cells might have for vehicles?
MAJED: I’d like to make two points. First, traditional internal combustion engines have a maximum efficiency called the Carnot efficiency. This limit is governed by fundamental thermodynamics.
EVIE: So?
MAJED: Well, the point is, fuel cells are not limited by the Carnot efficiency, so they might be able to achieve higher efficiencies than heat engines.
LECTURER: What’s your second point, Majed?
MAJED: My second point is that fuel cells produce electricity direct. Electricity is a very versatile form of energy, and that means that fuel cells have a wide variety of potential applications.
EVIE: Yes, but it’s a disadvantage in a car application. The cell can’t drive the wheels direct, so you have to put in an electric motor!
MAJED: I don’t agree with that, Evie, because electric motors are a great way of producing shaft power.
JACK: Sorry, but what are we talking about exactly?
MAJED: OK, look at it this way. Electric motors have a very high power and high torque at a wide range of speeds. Plus, they give the designer a lot of flexibility.
JACK: Can you give me an example?
MAJED: Sure. You may not need to include a gearbox with an electric car, because of the excellent torque-speed characteristics of the motor.
LECTURER: You’re all making good points about motors. But let’s focus on fuel cells. We need to be clear here that fuel cells are only just beginning to be commercially available.
LEILA: Yes. One big issue is that the fuel cell stack requires a lot of additional equipment around it, just to make it work and keep it going.
EVIE: In what way?
LEILA: I mean pumps, control systems, management systems … What I’m trying to say is, although a fuel cell appears in essence to be a beautifully simple device, making a small practical one is difficult.
JACK: I’d just like to say that they are also quite expensive for certain applications.
LECTURER: Why is this?
JACK: Because the catalyst used in the chemical reaction is usually platinum, which is a rare and expensive element.
124
LECTURER: Absolutely. There’s still work to be done. But durability and reliability targets have begun to be met, so the possibility for mass production may soon become a reality.
Unit 9, Lesson 9.2, Exercise B ≤2.9
Part 1 Good morning, everyone. This is the first of a series of lectures on health and safety in the workplace. So, first of all, we’re going to look at some of the most important principles of health and safety in an engineering context.
All managers have a duty under the law to protect their employees’ health and safety. But what does that entail? Well, manufacturing is a business and its legitimate purpose is to make a profit. But there will always be some risk associated with manufacturing. So it should be clear that it also makes good business sense, in the end, for managers to assess and manage risk in a responsible way. Not everyone is aware of this, but employees also have a duty of ‘reasonable care’ – towards themselves and others.
Now, it could be argued that health and safety principles are sometimes applied without common sense. So, for example – for people who are allergic to nuts – food manufacturers put statements such as ‘may contain nuts’ not only on the side of any products that may contain traces of nuts, but even on packets of peanuts themselves! But extreme examples like this can hide the real importance of health and safety.
Anyway, to get back to the main topic, there are seven primary duties for managers responsible for workplace safety.
Firstly, there should be a clear risk assessment policy that is applied consistently. The purpose of this is to identify all the safety implications of a particular procedure before the procedure is put into operation. Many accidents in the workplace are the result of inadequate risk assessment.
Secondly, all facilities – I mean machinery, structures, procedures, etc. – should be designed for safety. For example, a machine that automatically stops if the control box is opened. Then there’s maintenance of the plant and machinery. An example we can all understand is car brake pads – they wear down with use and need to be checked periodically to make sure they’re safe. Maintenance means repairing or replacing things when they are too worn.
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