Today, exhaustion of fossil fuel and serious environmental pollution earnestly require active use of renewable energy resources such as wind, geothermal and solar energies for power generation.
Particularly, geothermal resources with low temperature heat source have been developed extensively for power generation all over the world by using the Organic Rankine Cycle.
A research group led by Ri Hung Nam, a section head at the Faculty of Heat Engineering, has developed a 50kW geothermal power generation system that harnesses hot spring water.
The system consists of an evaporator, a steam turbine, a condenser, a preheater, a hot spring water pump, a working fluid pump and a cooling water pump and so on. NH3 (R717) is used as working fluid.
In the evaporator, the hot spring water from the intake well by the pump produces steam by heating working fluid with low boiling point from the preheater. The high pressure saturated vapor from the evaporator expands through the steam turbine to the pressure of condenser. At the same time, it drives the turbo-generator to generate electricity. In the condenser, the working fluid is condensed with the help of the cooling water.
The condensed working fluid is fed to the preheater by the pump.
In the preheater the working fluid from the condenser is heated to be saturated liquid with an evaporating temperature by the hot spring water from the evaporator. Hot spring water from the preheater is used for heating of a building. And the heated working fluid in the preheater enters into the evaporator and then the above cycle is repeated.
This system has horizontal bundle heat exchangers (evaporator, condenser and preheater) and a single impulse stage steam turbine.
In the evaporator hot spring water flows into the tube and working fluid evaporates outside. In the preheater, working fluid flows into the tube and hot spring water flows out of it.
In the condenser, cooling water flows into the tube and working fluid vapor is condensed outside.
The system saves 120~180t/h of coal a year and it can contribute to the prevention of global warming. It is available in all areas with over 70℃ of heat sources such as hot spring and wasted heat.
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