In recent years considerable attention has been focused on the issue of the depletion of petroleum and other energy resources, resulting from industrialization, rising standards of living, growth of the world’s growing population and other factors. Moreover, the consumption of enormous amounts of fossil fuels leads to environmental problems on a worldwide scale, including air pollution, acid rain, global warming triggered by carbon dioxide, and destruction of the ozone layer caused by CFCs. As the twenty-first century dawns, we must confront the challenge of finding solutions to these problems. By recovering urban waste heat and using it to heat and cool buildings throughout the district, for example, DHC systems can utilize untapped energy sources to help decrease our dependence on fossil fuels. For this reason district heating and cooling has been identified as a key component of the urban infrastructure for the new century, one that is both effective and friendly to the global environment. District heating and cooling systems make use of the following Unutilized energy resources:
Waste heat from systems that generate electricity by powering engines or turbines using gas or oil (co-generation systems) serve as an efficient energy source for buildings in the district.
Energy is supplied by making use of the temperature differential between the air and intermediate water, wastewater from households and water from treated sewage.
Thermal energy is supplied to buildings in the district by harnessing the abundant waste heat generated when trash and other waste materials are incinerated. An excellent source of energy in terms of both quality and quantity, this type of thermal energy has been used effectively throughout the world for many years.
The use of thermal energy obtained by burning refuse derived fuel (RDF) is made from discarded wood, paper, plastic and other materials is the basis of a heating and cooling system. Not only is the fuel is highly transportable, there are fewer limitations on the locations where this source of energy can be used compared to waste incineration facilities.
Seawater is an excellent source of thermal energy because it freezes at a lower temperature than fresh water. Another advantage of this energy source is its virtually inexhaustible supply.
River water and groundwater provide a stable source of thermal energy because of their relative lack of fluctuation in temperature throughout the year and at different times of the day.
Waste heat from electrical transformers, subways, underground shopping arcades and factories can be reused as a source of thermal energy for those living and working nearby.