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Hydrogen Economy, Geothermal and Ocean Power, and Climate Change
Published in Roy L. Nersesian, Energy Economics, 2016
The Earth’s crust insulates life from the hot interior of the mantle. The normal temperature gradient is about 50°F–87°F per mile or 17°C–30°C per kilometer of depth and higher where the crust is relatively thin or near plate boundaries and volcanoes. Magma trapped beneath the crust heats up lower rock layers. If hot rock is porous and filled with continually replenished subsurface water with access to the surface, then the result is fumaroles of escaping steam and hot gases, geysers of hot water, or pools of boiling mud. As a geothermal source, the Earth becomes a boiler, and escaping hot water and steam, called hydrothermal fluids, are tapped for hot spring baths, heating greenhouses (agriculture), heating water for marine life (aquaculture), as district heating for homes, schools, commercial establishments, streets, and sidewalks to prevent ice formation, and as a source of hot water for industrial use or steam for generating electricity. Nearly all of Reykjavik, Iceland, receives hot water from geothermal sources. A well is being drilled 2 km deep in a suburb of Paris to tap heated geothermal water to expand existing district heating by 25 percent to include another 35,000 homes.12 Boise, Idaho capital district, and Oregon Tech, both heated with geothermal water, are among 18 district heating systems in the western US. An estimated 270 western US cities are located close enough to geothermal sources to take advantage of district heating. Geothermal energy has reduced carbon emissions by 22 million tons plus 200,000 tons of nitrogen oxides and 110,000 tons of particulates annually.
Renewable Energy Resources
Published in Julie Kerr, Introduction to Energy and Climate, 2017
Geothermal power plants use hydrothermal resources that have both water (hydro) and heat (thermal). Geothermal power plants require high-temperature (300°F–700°F) hydrothermal resources that come from either dry steam wells or from hot water wells. People use these resources by drilling wells into the earth and then piping steam or hot water to the surface. The hot water or steam is used to operate a turbine that generates electricity. Some geothermal wells may be as deep as 3.2 kilometers.
Geothermal Energy
Published in Radian Belu, Fundamentals and Source Characteristics of Renewable Energy Systems, 2019
Direct use of geothermal energy includes the hydrothermal resources of low to moderate temperatures, providing direct heating in residential, commercial and industrial sector, include among others: space, water, greenhouse, and aquaculture heating, food dehydration, laundries and textile processes. These applications are commonly used in many countries. Unlike geothermal power generation, direct-use applications use heat directly to accomplish a broad range of purposes. The temperature range of these applications is from 10°C to about 150°C. Given the ubiquity of this temperature range in the shallow subsurface, these types of geothermal applications have the potential to be installed almost everywhere. Geothermal resources are also used for agricultural production, to warm greenhouses, to help in cultivation or for industrial purposes, including drying fish, fruits, vegetables and timber products, washing wool, dying cloth, manufacturing paper and in milk industry. Geothermal heated water can be piped under sidewalks and roads to keep them from icing, during cold weather, extracting gold and silver from ore, and even for refrigeration and ice-making. Geothermal, ground-source heat pumps have the largest energy use and installed capacity worldwide, accounting for 70.95% of the installed capacity and 55.30% of the annual energy use. The installed capacity is 50,000 MWt and the annual energy use is 325,028 TJ/yr, with a capacity factor of 0.21 (in the heating mode). The energy use reported for the heat pumps was deduced from the installed capacity, based on an average coefficient of performance (COP) of 3.5, which allows for one unit of energy input (electricity) to 2.5 units of energy output, for a geothermal component of 71% of the rated capacity. The cooling load was not considered as geothermal effect; however, it has a significant role in the use of fossil fuels and pollutant emission reductions.
Environmental and human health impacts of geothermal exploitation in China and mitigation strategies
Published in Critical Reviews in Environmental Science and Technology, 2023
Yuanan Hu, Hefa Cheng, Shu Tao
With enormous potential, which is much more than that contained in all fossil and uranium reserves on Earth, geothermal energy can be used to partially substitute the fossil fuels and thus contribute to reduction in greenhouse gas (GHG) emissions (Wright, 1998). Geothermal energy is primarily extracted from the hydrothermal systems, which are relatively shallow (<1,000 m) and have high permeability for the natural flow of geothermal fluids (Zhang & Hu, 2018). Hydrothermal resources are primarily located in volcanic or tectonically active regions, where the fluid is heated by volcanic activity or the energy released from the movement of tectonic plates (Zhang & Hu, 2018). Geothermal energy was harnessed historically in the form of direct use, primarily hot water for bathing, swimming, and district heating, while harnessing it for power generation has attracted attention over the past several decades (Huang, 2012; Matek, 2016). Economic power generation requires high-temperature geothermal systems (typically >150 °C), although the units based on binary cycles can operate with fluids having temperatures down to around 90 °C. Geothermal fluids with temperatures ranging from 25 to 90 °C are suitable for uses in agriculture and aquaculture, fluids of 50–100 °C are good for space heating, while those >100 °C can be applied in industrial processes (Lund, 2013; Lund & Boyd, 2016).
Synergistic effect of ZnO nanoparticles and hesperidin on the antibacterial properties of chitosan
Published in Journal of Biomaterials Science, Polymer Edition, 2022
Ibrahim Erol, Ömer Hazman, Mecit Aksu, Emine Bulut
Keeping the amount of CS constant, three different CS/ZnO-HSP nanocomposites were produced by the hydrothermal method by obtaining mixtures containing 2, 4 and 6 wt% ZnO-HSP. The typical experimental procedure for nanocomposite containing 4% ZnO-HSP is as follows: 2 g of CS, 80 mg of ZnO-HSP, and 40 mL of water were added to a 100 mL Teflon-coated autoclave, and mixed with a magnetic stirrer for 20 min. To ensure the dispersion of ZnO-HSP nanoparticles in the CS, the mixture was homogenized with an ultrasonic probe for 20 min. Then, the Teflon container was placed in the hydrothermal synthesis system, and the hydrothermal process was continued at 150 °C for 24 h. The hydrothermal system allows temperatures above the boiling point of water to be used. Thus, a substance reacts above its soluble decomposition point at high temperatures and pressures. The obtained CS/ZnO-HSP nanocomposites were separated from the mixture by filtration and washed three times with distilled water. It was then dried in a vacuum oven at 90 °C for 8 h. All production steps of CS/ZnO-HSP nanocomposites are shown in Scheme 1.
Facile preparation of wear-resistant and anti-corrosion films on magnesium alloy
Published in Surface Engineering, 2022
Limei Ren, Shan Gao, Zhaoxiang Chen, Dongxiao Jiang, Huameng Huang
In recent years, surface modification has received growing attention as a means to improve the wear and corrosion resistance of Mg alloys. Such techniques include hydrothermal treatment [5], micro arc oxidation [6,7], vapour deposition [8], sol–gel processing [9], and ion implantation [10]. Among them, hydrothermal treatment is advantageous in that it is simple to operate, has low energy consumption, and is environmentally friendly. It has also been reported that hydrothermal treatment has been employed to successfully form a uniform and compact film primarily composed of magnesium hydroxide (Mg(OH)2) on the surface of the AZ31 magnesium alloy [11,12]. The compact Mg(OH)2 film with an adequate thickness can therefore act as a physical barrier to inhibit penetration of a corrosive solution to the film/substrate interface. However, Mg(OH)2 can be easily destroyed by some deleterious anions in solution (especially Cl−), and so it cannot provide long-term effective protection [13]. In contrast, the layered double hydroxide (LDH) film possesses a significantly higher corrosion resistance than the Mg(OH)2 film [14,15] due to the fact that the ion-exchange capacity of the LDH film can effectively reduce the concentration of Cl− around the film [16,17]. However, unlike the hydrothermally synthesised Mg(OH)2 film, which has a relatively compact growth structure, the LDH film is composed of nano-sheets grown vertically on the substrate, which results in the formation of numerous micro voids in the film [18].