very interesting lesson.
Yeah i like this topic.
very good lesson
Direct heat method involves the heating of turbine which turns generator on for electricity generation that is the most geothermal turbine method.
What is single or double turbine?
In the same way that waste heat from conventional power stations can be used for direct heating of buildings, and in industrial production and horticulture, low-grade geothermal energy has considerable potential.
Many existing developments, such as those in Iceland, use spent fluids from geothermal electricity generation. Areas of natural hot springs are an obvious target, but it is also relatively simple to exploit normal heat flow using either natural groundwater or a variety of heat-exchange systems.
Between 1992 and 2000 the global capacity of direct geothermal heating increased fourfold from 4 GW to 16 GW. Compared with heating that uses fossil fuels, supplied very efficiently either by gas pipelines or electricity grids, direct geothermal heating is economic only when fossil fuel prices are high.
The capital outlay on wells and distribution systems is the main financial burden, making direct geothermal heating unattractive for small-scale development. However, there is an approach that may become viable for a great many more individual consumers or small housing schemes.
In soil, even at shallow depths, geothermal heat flow and heat retained from summer solar warming ensures that subsurface temperatures are higher than winter air temperatures.
This very-low enthalpy source can be exploited using a heat exchanger, known as a ground-source heat pump that uses upward and downward pipes about 100-150 m long set into the ground.
A heat transfer fluid, usually water, circulates within the loop to transfer heat from the ground to the properties above. When demand is low during summer the underlying soil and rock reheat, ready once again for winter use.
A variant on this approach is to use heat pumps - effectively reversible air conditioners - to pump excess heat downwards in summer and upwards in winter. At least some of the high energy cost of air conditioning is recycled.
Ground-source heat pumps can be deployed almost anywhere, and there has been a recent explosion in their popularity. The approach was developed simultaneously in the USA and in Europe, particularly Switzerland and Sweden. Installations in Switzerland are growing by 10% a year, and at an even higher rate in the USA, where there are already over half a million units.
If 1000 residential units at the latitude of the UK were to have such geothermal heat pumps for winter heating and summer cooling, peak demand for electricity could be reduced by 1.7 MW, or gas demand by 0.7 TJ per year. The UK is a latecomer to this technology, but a new health centre in the Isles of Scilly now uses a 25 kW reversible ground-source heat pump to supply hot water, heating and cooling.