Question

Write  a  brief  note  on  geothermal  energy.

DSERT Class 10 Science Ch 1 Alternate Sources of Energy

Answer 1

Geothermal Energy is energy derived from the heat of earth. Heat from the center of the Earth conducts outwards and heats up the outer layers of rock called mantle. When this type of rock melts and becomes molten then it is called as magma. Magma can reach just below the earth's surface.
Rainwater sometimes seeks down through fault lines and cracks becoming super heated by the hot rocks below ( geothermal energy is the heat from the earth). It is clean and sustainable . 

Answer 2

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines thetemperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet and fromradioactive decay of materials (in currently uncertain[1] but possibly roughly equal[2] proportions). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots γη (ge), meaning earth, andθερμος (thermos), meaning hot.

Earth's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth's formation.[3]Temperatures at the core–mantle boundary may reach over 4000 °C (7,200 °F).[4] The high temperature and pressure in Earth's interior cause some rock to melt and solid mantle to behave plastically, resulting in portions of mantle convecting upward since it is lighter than the surrounding rock. Rock and water is heated in the crust, sometimes up to 370 °C (700 °F).[5]

From hot springs, geothermal energy has been used for bathing since Paleolithic times and for space heating since ancient Roman times, but it is now better known for electricity generation. Worldwide, 11,700 megawatts (MW) of geothermal power is online in 2013.[6] An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications in 2010.[7]

Geothermal power is cost effective, reliable, sustainable, and environmentally friendly,[8] but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.

The Earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited. Drilling and exploration for deep resources is very expensive. Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, and interest rates. Pilot programs like EWEB's customer opt in Green Power Program [9] show that customers would be willing to pay a little more for a renewable energy source like geothermal. But as a result of government assisted research and industry experience, the cost of generating geothermal power has decreased by 25% over the past two decades.[10] In 2001, geothermal energy costs between two and ten US cents per kWh