Reply To: Mind, Spirit, Science connection?

[zapkitty]

Brian H wrote:
Waste is not represented in your formula. w(t) is total energy, ¼ + 3/4 = 1.

Ah. I understand what you want to do now and it can be applicable to a problem with more given parameters… but in this case you’ve made an erroneous assumption regarding the basic data.

Viewed from outside, as a black box, the plant actually has only two factors that would concern us: its thermal output and its electrical output. w(t) and w(e)… and that’s all. What happens inside the plant is not a concern from an external point of view.

Of course the plant may be generating electricity at less than capacity and may be running cooler than it needs to… but for our example it’s close enough and in real life plant owners don’t tend to run plants at half power or build in much more cooling than they need.

And that would be why the comparison of the Dai-ichi units nominal ratings for w(t) and w(e) happens to hew fairly closely to the expected efficiency of those types of reactors.

Does it represent an actual reading of the efficiency of the plant? Within limits, a varying set of parameters, the answer is that it does if it is stipulated that the purpose of the plant is to provide power, not heat.

If one claims that one is using some of the heat produced by the plant for useful work in addition to the electrical output then certainly one can legitimately claim higher efficiencies than straight w(e)/w(t)… dividing w(t) into useful and rejected heat might get you eff = w(e)+w(tu)/w(tr) or something like that… but in our example here we are assuming that the heat is unwanted and is thus rejected.

So, from an external point of view you must assume that the w(t) accounts for all the losses in getting the w(e) to the grid. You need not make, and actually can not make, any other assumptions with the data that is given.

So the efficiency given by 3 w(e) and 9 w(t) in the example is indeed .33