Showing papers on "Geothermal desalination published in 1998"

Direct use of geothermal energy around the world

Abstract: SUMMARY Geothermal energy has been produced commercially for nearly a century, and on the scale of hundreds of MW for over four decades both for electricity generation and direct use. The world direct-use energy production is about 37 TWh/ a (installed capacity of 10,000 MWt in nearly forty countries), and is, with the exception of China, mainly in the industrialized, and central and eastern European countries. Fourteen countries have installed capacities over 100 MWt. The main uses are space heating (33%), heat pumps (12%) for heating and cooling, bathing (19%), greenhouses (14%), aquaculture (11%) and industry (10%). The application of the groundsource heat pump opens a new dimension in the scope for using the earthis heat, as heat pumps can be used basically everywhere and are not site specific as conventional geothermal resources. Geothermal energy, with its proven technology and abundant resources, can make a very significant contribution towards reducing the emission of greenhouse gases worldwide. It is necessary, however, that governments implement a legal and institutional framework and fiscal instruments allowing geothermal resources to compete with conventional energy systems and securing economic support in consideration of the significant environmental benefits of this energy source.

Chapter 11. Heat Exchangers

Abstract: Most geothermal fluids, because of their elevated temperature, contain a variety of dissolved chemicals. These chemicals are frequently corrosive toward standard materials of construction. As a result, it is advisable in most cases to isolate the geothermal fluid from the process to which heat is being transferred. The task of heat transfer from the geothermal fluid to a closed process loop is most often handled by a plate heat exchanger. The two most common types used in geothermal applications are: bolted and brazed. For smaller systems, in geothermal resource areas of a specific character, downhole heat exchangers (DHEs) provide a unique means of heat extraction. These devices eliminate the requirement for physical removal of fluid from the well. For this reason, DHE-based systems avoid entirely the environmental and practical problems associated with fluid disposal. Shell and tube heat exchangers play only a minor role in low-temperature, direct-use systems. These units have been in common use in industrial applications for many years and, as a result, are well understood. For these reasons, shell and tube heat exchangers will not be covered in this chapter.

Island sea water desalination plant sub-divided for discrete operation of each stage using only limited wind-generated power

Abstract: A sea water desalination and multi-stage reverse osmosis (19) unit is powered by electrical energy supplied by a wind generator. Each stage of the process is sub-divided and separable from the preceding process or stage, such that in times of low wind and power shortage, the desalination and osmosis (16) proceed in discrete steps matched to the available power supply (5).

Development of new RO seawater desalination technologies for cost and energy saving.

Abstract: The new RO seawater desalination system for cost and energy saving has been developed. The newly developed “Brine Conversion Two-stage RO Seawater Desalination System” uses less energy than the conventional system to produce the same amount of fresh water. This system produces more fresh water from the concentrated water (salt concentration 5.8%, produced under 6.5 MPa pressure), which was exhausted to the sea in the conventional system.The new type membrane, which can be operated in conditions of high-pressure (9.0 MPa) and high concentration (5.8%), was developed and its performance of seawater desalination have been proved to be in good conditions.

Solar powered reverse osmosis desalination

Abstract: If a bore intended for domestic supplies yields only brackish water, the intending users must either sink another bore, move to another location, drink the water as is, or employ some form of desalination technology. All options are either expensive, socially disruptive or pose serious health risks. With recent advances in reverse osmosis technology, the last option has become a realistic and viable one. To apply this normally high-tech option to remote locations however, a change in priorities becomes essential. For any technology to be successful in these regions it must satisfy the criteria for 'appropriate technology.

Thermocline driven desalination: status for Cape Verde

Abstract: The natural ocean thermal gradients in many areas of the world can be used to efficiently produce desalinated water for consumption and other uses, and the cold seawater constitutes a valuable resource for other applications such as air conditioning and aquaculture. A thermocline driven desalination (TDD) system is being developed for the Republic of Cape Verde, which has the key attributes of warm surface water and nearby deep cold water. The system uses an advanced multistage-flash (MSF) evaporator for the distillation process and large diameter polyethylene pipes for warm and cold seawater supplies. Although the initial capital costs are higher than for conventional desalination facilities, the lower power requirements for the TDD system result in much lower operating costs that make it an attractive economic option. Another important advantage is that dependence on imported fuel is significantly reduced.