Abstract
It is well known that when electricity is used for heating by radiators or otherwise, approximately 3,415 B.Th.U. are given out for each unit of electricity consumed, and as the efficiency of the apparatus is 100 per cent, this represents the limit of the heat available from electricity with present-day methods.
If therefore, someone confronts us with a statement that in fact many times this amount of heat can be delivered per unit of electricity consumed, he is likely to be looked upon as one who has not heard of the principle of the conservation of energy.
Nevertheless this statement is perfectly correct, and many practical examples on a large scale are now in successful operation. The mechanism by which this result is achieved is known as the heat pump. The possibility of running a heat engine in reverse and producing not only refrigeration but warming as well, was pointed out by Kelvin as long ago as 1852.†
The object of this paper is to show (a) that with a proper theoretical approach there is nothing revolutionary in the principle, (b) to describe plants of this character and give examples, (c) to show that while the British Thermal Unit is in one sense a measure of heat, it is in no sense a measure of the value of heat, since a British Thermal Unit of lower-temperature heat has little value while a British Thermal Unit of high-temperature heat has a great value, and (d) to show that electricity may be looked upon as equivalent to heat of the highest temperature and value and capable of producing, with the heat pump, many times its direct equivalent of heat.
Get full access to this article
View all access options for this article.