Energy recycling system for urban waste heat

Abstract

Today, energy is indispensable to daily life all over the globe. Nevertheless, it is clear that energy cannot be consumed without limit given the finite nature of resources and environments. The consumption of abundant amounts of energy today unavoidably releases huge amounts of waste energy to the surrounding environment from houses, offices, shops, factories, subways sand other facilities. Heat pumps can raise the temperature of waste heat to a usable temperature range with the use of a small quantity of driving energy. In this way heat pumps act like water pumps, which can lift river water to a higher elevation by using a small amount of driving energy. Thus if a piping network for gathering and transporting waste heat is available, heat pumps can efficiently supply useful heat to customers by recovering energy from waste heat. If the waste heat of cities can be recovered, a kind of energy recycling system can be constructed using heat pump technology. This will result in the efficient use of energy and the conservation of our precious natural environment. For individual use, a heat source network might be too expensive. But waterworks and sewer systems in cities can be used for this purpose with slight modifications. In many cities, maintaining a sufficient water supply is becoming a real problem, leading to the promotion of water recycling and separate networks for the provision of drinking and non-drinking water. Sewers are one of the main repositories of waste heat, and sometimes waste heat is then diffused to rivers and lakes which are water supply sources. A heat source network would distribute waste heat and protect the environment at the same time. A heat distribution network using heat pumps also has advantages over conventional district heating systems: little heat loss, economical district piping, easy expandibility, and the ability to make use of a variety of waste heat sources. Such a system can efficiently meet the complex needs of modern cities where heating and cooling demands coexist in a variety of areas. A heat pump can heat and cool both simultaneously and alternatively, and works best in balancing heating and cooling demands. In this way energy recycling systems using heat pumps can play an important role in daily life through energy and environmental conservation. Consequently, energy recycling systems should be introduced as part of our social system from the viewpoint of urban planning, energy policy and environmental protection. A model project will be introduced with actual operational experiences.