Geothermal energy: Power plant technology and direct heat applications

Abstract

Geothermal technologies use renewable energy resources to generate electricity and direct use of heat while producing very low levels of greenhousegas (GHG) emissions. Geothermal energy is the thermal energy stored in the underground, including any contained fluid, which is available for extraction and conversion into energy products. Electricity generation, which nowadays produces 73.7 TWh (12.7 GW of capacity) worldwide, usually requires geothermal resources temperatures of over 100 • C. For heating, geothermal resources spanning a wider range of temperatures can be used in applications such as space and district heating (and cooling, with proper technology), spa and swimming pool heating, greenhouse and soil heating, aquaculture pond heating, industrial process heating and snow melting. Produced geothermal heat in the world accounts to 164.6 TWh, with a capacity of 70.9 GW. Geothermal technology, which has focused for decades on extracting naturally heated steam or hot water from natural hydrothermal reservoirs, is developing to more advanced techniques to exploit the heat also where underground fluids are scarce and to use the Earth as a potential energy battery, by storing heat. The success of the research will enable energy recovery and utilization from a much larger fraction of the accessible thermal energy in the Earth's crust. 1.-Introduction Geothermal technologies use the heat contained in the ground. In its broad term the geothermal energy is the thermal energy contained in our planet, the Earth. In this document we will restrict our attention to the practical use for mankind, i.e. the heat that can be extracted from a depth up to about 10 km, which is the maximum depth reached by human drilling. In this thin portion of Earth heat is inexhaustible, since it

Thermo-Fluid Dynamic Effects of the Radial Location of the Baffle Installed in a Solar Updraft Tower

“…Base case Not applicable (without baffle) BL_1.0 1.0 BL_1. 5 1.5 BL_2.0 2.0 BL_2. 5 2.5 BL_3.0 3.0 BL_3.…”

“…Interest in renewable energy is growing around the world as the Paris Agreement was signed in 2015 to reduce global greenhouse gas emissions, the cause of global warming [1]. As this trend develops, various methods of power generation from natural resources with little greenhouse gas emission, such as biomass [2,3], wind power generation [4], and geothermal power generation [5], are being studied. Regarding solar energy, the annual amount of solar radiation reaching Earth's surface is approximately 3,400,000 EJ (exajoule, 1 × 10 18 J), which is more than 7500 times the annual world primary energy consumption of 450 EJ [6].…”

Geothermal power generation in China: Status and prospects

“…27.78 MW, ranking 18th in the world. 23 The cascade utilization of geothermal resource can increase the thermal efficiency of the system and maximize the geofluid usage. 4 China is rich in HDR resources, which can be cost-effectively developed via the EGS technology.…”

“…6 Given the environmental impacts and benefits, an enhanced geothermal system (EGS) is considered as one of the most lucrative technologies for the large-scale generation of electric power. 23 Geothermal resources can also be combined with other energies to form a hybrid power generation system such as (a) solar-geothermal, (b) oil-geothermal, and (c) geothermal mine systems. However, the EGS implementation in China (even as a pilot project) is quite challenging due to pending problems of a proper site selection, land suitability and availability, high investment risks, and induced seismic activity.…”

“…However, DFORC power plants also look very promising for the utilization of low-temperature geothermal resources. 23 The cascade utilization of geothermal resource can increase the thermal efficiency of the system and maximize the geofluid usage. 23 Geothermal resources can also be combined with other energies to form a hybrid power generation system such as (a) solar-geothermal, (b) oil-geothermal, and (c) geothermal mine systems.…”