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In process of combustion, gasification, steam reforming and renewable fuels are converted into a

different fuel , heat or electricity . as the population increases the global consumption of energy risescontinuously. The primary energy used to satisfy this demands are fossile fuels. The conversion of

this energy to useful work by combustion and thermal engines is based on the laws of

thermodynamics. Hence they limit the efficiency inturn results in release of harmful gases, which

increases pollution. Therefore we are in search of an alternative technique which are more efficient in

renewable energy conversion to useful work and they reduces the pollution too.

Our way to increase the efficiency and reduce the pollution problems is by recuperating and utilising

the low grade thermal energy in combustion energies.

Striker made an analysis on the canadian industries and showed approximately 70% of I/P energy is

released to environment through the waste heat streams. They are :

1) Liquid stream (50-300)2) Stack losses3) Low to mediam stream losses4) Process gases and vapours.

So we are going to describe the method which convert low thermal energy to useful work and

electricity.

The one we are describing here is supercritical and transcritical cycles using CO2 as working fluid

due to

1) Non toxic2) Not inflammable3) It is abundant, affoddable inert

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The schematic diagram of super critical and transcritical cycle using CO2 as working fuel.

The CO2 conditions at the turbine inlet are 200 bars, 650C which gives thermal efficiency of 45%.

Reseach work is going on the above mentioned power cycle. They are planning to used then advanced

nuclear reactors.

Zhang analysed solar pordered CO2 transcritical cycle.

In this cycle evacuated solar collector is used to heat CO2. The heating in the collector makes the

supercritical CO2 temperature high. This high temperature supercritical CO2 drives the engines and

the output power is available from the turbine. The low pressure CO2 coming out of the turbine is

cooled in heat recovery system. After cooling the CO2 is pumped by feed pump into the high pressure

conditions and cycle starts again.

They established that the electric power output increses with solar radiation, air temperature collector

area and water inlet temperature but decreases with heat exchange area.

Compare the rankine cycle with organic fluid and with this cycle and showed that under the given

conditions the CO2 transcycle has slightly higher power O/P and is more comfort and ecofriendly

than the older one.