grk more expensive than nuclear, page-29

In response to your question, Dexterbland, the Massachusetts Institute of Technology has a designed a program to calaculate the conversion of MW thermal to MW electric. This is the tool to predict the differences in extraction capacity.

The reason for the exponential difference has to do with the amount of vapour produced in the Rankine/Kalina Cycles, and the concept can be explained quite simply.

Only about 15-20% of the working fluid in a
Rankine/Kalina circuit is turned into vapour at 220C. A large portion of heat is expended getting the fluid to the point of vaporisation. Any extra heat energy added to the fluid allows an exponentially larger amount of vapour to be produced, as the energy is not reduced by heating the liquid further. This process varies in efficiency according to the heat capacity of both the working fluid and the geothermal fluid, and the flow rate.

For anyone finding the concept hard to grasp, imagine you had 1000 units of heat, and it took 800 units of heat to get the working fluid up to boiling point. There are 200 units of heat left over, and these cause the liquid to vaporise. If you changed the initial amount of heat to 1500 units, it still only takes 800 to get the fluid to boiling point, so there are now 700 units vaporising the fluid. This is, roughly speaking, a 350% increase in vapour produced, and demonstrates the concept that additional heat provides exponential vapour creation. It is the creation of vapour that defines the cost/MWh.

This very rough analogy does not take into account energy it takes to turn a liquid into a vapour, but this is minimal.

Also, obviously with geothermal there are no fuel costs (unlike coal), so we're only dealing with production costs and operating costs. Dexterbland, the production costs for geothermal will be almost entirely capital costs (wells, construction, plants). This is why companies with lower thermal resources will be uncompetitive. The price of a power plant is fairly fixed. A 300MW plant will cost the same for GDY as for GRK. But if one company produces twice as much electricity, then there will be half the operating costs per MW.

As such, GDY will produce power for $45-$55/MWh ($40/MWh capex, $5/MWh opex, $8/MWh transmission)

GRK, by current targets, will produce at $90-$95/MWh ($90/MWh capex, $5/MW opex, $0/MWh transmission.)

When and if GRK upgrade to higher temperatures, their costs may reduce dramatically. These figures assume GRK proves a high quality reservoir with flow rate at least equal to GDY's project.

Also, $8/MWh includes the cost of all line construction and transmission losses.