Geothermal Turbine Cycle Selection
Geothermal Turbine Cycle Selection
(OP)
Hi,
I am assessing the potential of some geothermal resources and am unsure why certain people select binary organic Rankin cycles (ORC) whilst others with similar field properties go for binary steam cycles. I understand the flow and temperature of the brine has an impact along with the overall capital costs but what other technical factors determine the selection of the cycle type.
I would just really like to look at the field and brine conditions and be able to know if it will be ORC or a steam cycle
Any help appreciated
I am assessing the potential of some geothermal resources and am unsure why certain people select binary organic Rankin cycles (ORC) whilst others with similar field properties go for binary steam cycles. I understand the flow and temperature of the brine has an impact along with the overall capital costs but what other technical factors determine the selection of the cycle type.
I would just really like to look at the field and brine conditions and be able to know if it will be ORC or a steam cycle
Any help appreciated





RE: Geothermal Turbine Cycle Selection
You could look through the listings from the GRC ans see if you find any correlation.
I have seen a couple of installations that use a binary organic (butane) to drive a rotary screw expander in stead of a turbine. These look very reliable and have a wider operating envelope. They are based on screw compressor knowledge. They inject a little oil into the butane to seal and lube the screws.
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Plymouth Tube
RE: Geothermal Turbine Cycle Selection
This website contains a good explanation of the ORC.
http://en.wikipedia.org/wiki/Organic_Rankine_Cycle
Reading between the lines, a bit, my understanding is that the fundamental advantage of an ORC application lies in tha ability to utilize a low-temperature source of heat AND the ability to save capital expenses through a low-pressure cycle design.
Steam cycles, as we all know, transmit heat and energy well but only at a (relatively) high pressure. High pressures translate into thicker piping walls, heavier and more expensive turbines etc...
Since waste heat boilers are a reasonable analog for proposed geothermal plants.....and since these plants only seem to make sense for power generation at 450F-500F and up, I would expect that any continuous steam source below about 450-500F would be a better candidate for an ORC.
My opinion only
-MJC
RE: Geothermal Turbine Cycle Selection
While a condensing steam turbine will generate more energy from the same steam (MW/t/h steam)the binary plant has been used becuase of lower capital cost $/MW.