District heating systems

Figure 4-25. Nitric acid plant at Fredericia (Denmark) with a four-machine turbogroup and generator. Power output to district heating system = 0-27 MW Power output to electric grid = 0-5.8 MW Steam turbine = 10.8 MW Axial compressor = 8.2 MW Centrifugal compressor = 4.1 MW Expander = 7.4 MW Nitric acid production = 650 t/d.

Figure 250. Open sorption storage for heating connected to a district heating system...

The development of district heating systems is linked with the development of other systems such as combined heat and power systems, which generate waste heat, together with power. These increase the fuel use efficiency [35]. Also heat pumps should be introduced in residential heating systems [18]. In some countries like Norway, district heating system s GHG emissions have been compared with those of individual heating systems and it has been found that the first have lower C02 emissions. 

Units that produce 50 to 100 kilowatts can heat multi-dwelling apartment buildings. They are fueled by natural gas or diesel fuel. Units of 200 to 2,000 kilowatts that operate on fuel oil or diesel fuel are suitable for large apartment buildings or small district heating systems. The heat from... 

District heating systems can use the waste heat from electric generation and industrial plants that would be released to the air or to nearby water supplies. Some estimates suggest that district heating could save as much as one billion barrels of oil per year in the United States. 

In some European cities, waste heat from fossil fuel electric power plants is used for district heating with an overall energy efficiency of 85%. These plants were not originally constructed as cogenerating units. Waste heat from industrial process plants can also be used. Geothermal sources are used to provide heat for district heating systems in Iceland and Boise, Idaho. 

District heating systems are often financed by municipal bonds at low interest rates, to be repaid over a 30- to 40-year period. This makes the annual cost per home competitive with or less than that of conventional heating systems. 

ICES have several advantages over conventional district heating systems or individual building heating systems. An ICES will often serve business, commercial and residential districts. Since the peak heating and... 

Conventional heating systems burn fossil fuels at high temperatures to heat water to 120°F. Most district heating systems operate in the same way. In these cases, when the hot water cools to 90°F or less, it is no longer warm enough to supply heating. This remaining heat is eventually lost to the environment. An ICES can recover this low-temperature heat that would otherwise be wasted. This helps to increase system efficiency. 

ACESs and ICESs rely on heat pumps and storage systems, and need notable amounts of energy to operate. An annual storage solar district heating system could supply most of a community s annual space heating requirements with a minimum of nonrenewable energy. 

An annual storage solar district heating system is capable of supplying 90% of the annual heating requirements for the homes in a community. Depending upon the climate zone, the required collector area per house can range from 70 to 300 square feet. This can be reduced if residential heat loads are lessened through increased weatherization and the addition of passive solar features. 

Four complete extrusion lines for the manufacture of PE pipes are described which are to be supplied by Battenfeld for Moscow s district heating system. The heating system utilises freely layable steel pipes the conveying the superheated steam, the steel pipes being protected and insulated by means of the PE pipes. The cavity is filled with an insulating layer of PU foam. 

Hauksson, T., Thorhallsson, S., Gunnlaugsson, E. Albertsson, A. 1995. Control of magnesium silicate scaling in district heating systems. In Proceedings World Geothermal Congress, Florence, 18-31 May, 2487 -2490. 

Thorhallsson, S., Ragnars, K., Arnorsson, S. Kristmannsdottir, H. 1975. Rapid scaling of silica in two district heating systems. In Proceedings Second United Nations Symposium on the Development and Use of Geothermal Resources, San Francisco, 20-29 May, 1445-1449. 

The economics of power generation can be highly improved if the heat, which otherwise would be wasted, can be sold. Therefore the combined heat-power systems ( co-generation ) provide a solution with maximum economic benefits. The best way of waste heat utilization is the use of heat in a district heating system, which can take up the substantial heat load. 

Fig. 8. Apartment buildings in Oberwald (canton Valais, Switzerland) connected to the cold district heating system of the Furka railway tunnel (for details see text). Photograph by J. Wilhelm.

Pernecker, G. Uhlig, S. 2002. Altheim Geothermal Project District heating system in Upper Austria pays for injection well with power generated by a low-enthalpy ORC turbogenerator. Geothermal Resources Council Bulletin, 31, 33-36. 

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