What is Geothermal: Definition and 27 Discussions

Geothermal gradient is the rate of temperature change with respect to increasing depth in Earth's interior. As a general rule, the crust temperature is rising with depth due to the heat flow from the much hotter mantle; away from tectonic plate boundaries, temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in most of the world. However, in some cases the temperature may drop with increasing depth, especially near the surface, a phenomenon known as inverse or negative geothermal gradient. Strictly speaking, geo-thermal necessarily refers to Earth but the concept may be applied to other planets.
Earth's internal heat comes from a combination of residual heat from planetary accretion, heat produced through radioactive decay, latent heat from core crystallization, and possibly heat from other sources. The major heat-producing isotopes in Earth are potassium-40, uranium-238, uranium-235, and thorium-232. At the center of the planet, the temperature may be up to 7,000 K (6,730 °C; 12,140 °F) and the pressure could reach 360 GPa (3.6 million atm). Because much of the heat is provided for by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher. Heat production was twice that of present-day at approximately 3 billion years ago, resulting in larger temperature gradients within the Earth, larger rates of mantle convection and plate tectonics, allowing the production of igneous rocks such as komatiites that are no longer formed.The top of the geothermal gradient is influenced by atmospheric temperature. The uppermost layers of the solid planet are at the temperature produced by the local weather, decaying to approximately the annual mean-average temperature (MATT) at a shallow depth; it is this depth which is used for many ground-source heat pumps, sometimes loosely referred to as "geothermal heat pumps" by laypeople. The top hundreds of meters reflect past climate change; descending further, warmth increases steadily as interior heat sources begin to dominate.

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  1. AhmedAB

    I am trying to design an axial turbine for my project

    TL;DR Summary: I have a problem designing an axial turbine, there is a lot I don't understand hey, how are you all doing, I am a chemical engineering student working on designing a geothermal power plant, weirdly I have been told that I must design an n-pentane turbine for our Plant, it's so...
  2. Oldman too

    A new technique for imaging underground geothermal features

    Last night, (3/23) I read this article, alas, today it has disappeared behind the inevitable paywall. (this means it's a good piece) If you have access to Nature articles, this is a fascinating read. A huge advance in Geophysics that will see a lot of attention in future geothermal studies...
  3. chemisthypnos

    Trying to build a miniature binary geothermal plant for education

    I am trying to build a miniature (it should fit on a desk) binary geothermal power plant for educational purposes. I obviously do not expect to drill into the ground with this power plant, but I hope to be able to demonstrate new design principles with it. I have many questions as to how to do...
  4. BillTre

    5.5 Earthquake Associated with S. Korean Geothermal Plant

    Science magazine news article here.
  5. C

    Which Type of Geothermal Power System is the Best?

    There are three geothermal systems that are commonly used: sry steam, flash steam, and binary cycle https://www.eia.gov/energyexplained/index.cfm?page=geothermal_power_plants . What are the efficiencies of the plants from best to least effecient on average?
  6. J

    A What is the method for calculating the dampening of thermal oscillations?

    Hello, I am attempting to solve the 1 d heat equation using separation of variables. 1d heat equation: ##\frac{\partial T}{\partial t} = \alpha \frac{\partial^2 T}{\partial x^2}## I used the standard separation of variables to get a solution. Without including boundary conditions right now...
  7. N

    Whatever happened to geothermal energy production?

    I've become nauseated with the recent obsession with colonizing Mars, mining the moon or asteroids, and spending resources on intermittent power production from wind, solar, and batteries. I've looked at numerous sources of energy production and have come to the conclusion that instead of...
  8. L

    Geothermal Power Installation for Home Heating & Cooling

    Hi, i looking for install in my home geothermal system for heat/cool my house with lower electricity. Here is the spec of my heat pump. If i understand my heat pump extract energy from the earth. so with this pump, the total energy is 7 kWh input and output 21 kWh heating or 17 kWh for cooling...
  9. P

    Viability of closed loop deep geothermal plants?

    Hello everyone, Just posting this because I was wondering if it's possible to build 5-10km deep closed loop geothermal power plants from microgrid sizes of 1-5MWe to commercial power plant sizes of 0.5-1GWe that can have construction costs in the $3,000,000 per MWe range (similar to solar and...
  10. D

    How can I calculate the power delivered using geothermal energy and an aquifer?

    Homework Statement See attachment Homework Equations I guess I need to do something with this equation: P= cmρJΔT ρ is then the density of water 1000m3/kg J is given Cm is given But what to do with the temperatures... ΔT= Th-Ta? But then you get a negative number and the ask for the power...
  11. C

    Geothermal heat extraction math problem

    Homework Statement The actual efficiency of a geothermal power plant using a 200 C geothermal resource is only about 7%. Take this value as typical of California's Geysers geothermal field, which produces 900 MW of electric power. a) Find the actual rate of geothermal heat extraction at...
  12. B

    Geothermal heat pump or heat engine power requirements

    Homework Statement In winter, you like to keep your house interior at 21.0 degrees C. Your geothermal heating system, which was advertised as being reversible, draws thermal energy from an underground reservoir at 347 K. In a cold winter, with the average outdoor temperature being 0.0...
  13. M

    Thermodynamics: Vertical pipe flow of geothermal water

    1. Water at T1=240 C and P1=16 MPa is at 2 km depth. A drilling hole with diameter 0.2 m has the water flowing up with mass flow rate at 2 kg/s. The hole is considered adiabatic(no heat transfer). I need to find the following values at the top of the hole: Enthalpy(h), temperature(T2)...
  14. S

    Thermodynamics for a geothermal heat pump

    I'm going a bit off the reservation to try something experimental when I attempt my own HVAC installation and I'm having some trouble determining a few things. I want to transfer heat from water flowing in a 3/4" copper tube that is submersed in a larger body of water. The copper pipe has a...
  15. C

    Can Geothermal Energy Power Our Planet?

    hello to every one my name is nomi..glad to be here
  16. C

    Programs What engineering degree for Geothermal energy?

    Does anyone have any recommendations for an undergraduate degree that would prepare one for a career in geothermal energy production. Petroleum engineering deals with the injection and recovery of fluids from the earth, but strong arguments can be made for the value of an ME or CE path. Any...
  17. D

    What are the other types of geothermal cycles aside from dry, binary

    What are the other types of geothermal cycles aside from dry, binary and flash?
  18. S

    Geothermal power harnessing improvement

    If I undestend it right, one of the main problems of geothermal power plants (especially hot rocks power) is low power density under current technologies.It means we need to drill lot of very deep holes to exact enough energy and drilling constitute main cost of it.I thought on possibility to...
  19. G

    Geothermal heat pump water heater

    I am about to pour a concrete floor in an addition to my basement (about 13' x 24'). This room is adjacent to my electric water heater. I have bought a 9500 btu R-22 compressor which I plan to use to replace the electric element in my 50 gallon water heater. The condenser is the water heater...
  20. G

    Gravity & Geothermal: Why is Earth's Core so Hot?

    Why is the center of the Earth so hot so that we can use geothermal? Will the Earth deep down always be hot because of the pressure of all the mass on top all the way to the surface? In that sense, can we always draw on the geothermal heat?
  21. A

    Help with Geothermal Electric Generator from a hot spring

    Hi, I have access to a hot spring. I was thinking it may be ideal to construct a small geothermal electric generation unit using the steam. Question is, if I have access to the hot spring, is this enough as a source to go ahead with a geothermal generating unit of say 100 kw - 200 kw, which is...
  22. J

    Geothermal power entering atmosphere?

    Hello, I am hoping someone on here can help me find a source for a science question I have. How much power enters the Earth's atmosphere from the Earth itself [Geothermal power]? I was reading a discussion on another website, where someone was asking about the Global Warming effect of...
  23. wolram

    Geothermal Energy: Helium Isotopes Reveal Hotspots

    http://www.eurekalert.org/pubnews.php Helium isotopes point to the best sources of geothermal energy Unknown to most, the US has enough geothermal energy below its surface to supply three times the amount of energy that the US consumes annually. Up until this point no one has tapped this...
  24. Pythagorean

    Design Geothermal Power Generator: Ideas, Physics & Experimentation

    I'm looking to make a geothermal power generator out of something like a refrigerator or a small air conditioning unit (or even a car AC unit) Is there anybody here who as experience with these thing and would like to discuss design ideas and the physics behind them here? I really have no...
  25. E

    News Geothermal Power: Clean Energy or Climate Risk?

    Well most ppl thing this is a clean energy, but I'm skeptical about it. What we are doing here is that we are using the heat from the depth of the Earth to cool our water for powerplants. If we build thousands of those to use this energy, wouldn't we be cooling our planet? cause otherwise those...
  26. A

    Geothermal Well charachteristics

    Does anybody know where one could get a full data set from an existing geothermal well for a project? Im attempting to propose design of a stirling prime-mover power plant and I can't seem to find the complete information.
  27. L

    Exploring the Potential of Offshore Geothermal Energy Production

    I was wondering how feasible it would be to drill through the thinner ocean crust to create artificial geothermal spots for energy production. The crust is only about 10km thick, and drills have gone that deep but only on continental crust which is much thicker. I guess drilling and maintaining...