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**[SOLVED] Thermal efficiency of a coal powered power station**

## Homework Statement

A company plans to build a coal powered plant for eletricity generation. The coal is to be burnt ina heat engine designed to maintain a hot resovoir temp Th, and a cold resovoir of 120 degs celcius. What is the minimum Th for the company to break even, if domestic users are charged 15p kWh? Company buys coal at 6p kWh. 10% of electrical energy is lost in distribution system. Ignore capital costs.

## Homework Equations

n = 1 - Tc/Th

## The Attempt at a Solution

Well n = 0.9*6/15 = 0.36

So rearranging the equation i get:

Th = Tc/0.64

So remebering to change the units to Kelvins:

Th = 392.4 K

Problem is the anwer should be: 703K so where am I going wrong? thanks