Energy in South Australia and trap in the deeper heat. Due to the low permeability of granite, the hot rocks must undergo hydraulic fracturing and be stimulated to allow a flow of water through the system to produce energy. This heat is slowly conducted to shallower rocks near the surface. Petratherm propose developing the geothermal energy in the more permeable sedimentary rocks that overlay the hot granite, a process called Heat Exchange Within Insulator (HEWI). While somewhat cooler, in many cases they do not require hydraulic fracturing. It is estimated that one percent of geothermal energy shallower than five kilometres below the earth's surface
Net energy gain of gasoline, and the combustion of coal is converted from thermal to mechanical, and then to electrical energy. Examples of energy sources include: The term net energy gain can be used in slightly different ways: The usual definition of net energy gain compares the energy required to extract energy (that is, to find it, remove it from the ground, refine it, and ship it to the energy user) with the amount of energy produced and transmitted to a user from some (typically underground) energy resource. To better understand this, assume an economy has a certain amount of finite oil reserves