Heat pumping technology consists of thermodynamic techniques for transferring heat from a body that is a heat source to a higher-ternperature body. The transfer of heat by heat pumping cools the heat source, from which heat is absorbed, and adds heat to the body to which the heat is transferred. That is, a heat pump combines the functions of cooling and heating by nature. The proportion of the quantity of heat that can be utilized as heat output against to the quantity of energy (in terms of heat) that is necessary for operation of the heat pump (heat transfer), is called the coefficient of performance (COP) and serves as an index of the heat pump's operating efficiency. Recent technical progress has brought the value of the COP of air heat source heat pumps for residential use to almost 6, making it possible to put to use a quantity of heat equivalent to 6 times the energy that is consumed in the operation of the heat pump. The COP can exceed 10 in systems that allow the output to be evaluated as the sum of the quantities of heat for the cooling effect and the heating effect, which are the basic functions of heat pumping technology. In developing countries, where a great increase in demand for energy is expected, it is considered very effective and important, both economically and for resource conservation and protection of the environment, to build up such energy-saving technology, not just in terms of individual items of equipment but also, in future urban infrastructure, as social systems that make it possible to utilize both the cooling and heating functions Recent progress in electric power generation technology is bringing about a power generation thermal efficiency of 50% or more, and in electrically driven heat pump systems the energy utilization efficiency is improved by the combined effect of an unproved COP with greater power generation thermal efficiency. Heat pumping technology is therefore expected to come into wider use in a broad range of applications worldwide as a means of achieving ever more economical energy utilization.
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