If, as the man says in the article below, this is a proven concept,
then it will surely be a boon to all those who have studied the
Rankine Cycle and attempted to design a closed-loop incorporating
it's principles. I am including an excerpt from an article
describing possibly using the Copeland Scroll Compressor, not as a
compressor, but as a Propane vapor-driven motor that will also
(without further modification) drive it's internal induction electric
motor as a 3 phase electric generator. So far, I have not been able
to verify independently that this concept is viable and that anyone
has any long-term experience with the scroll compressors used in this
manner.

QUESTION: Is there anyone out there who knows or knows anyone else
who has personal experience with using a Copeland Scroll Compressor
as part of a Solar/Propane Rankine Cycle Electric Generating
System? If so, please contact me directly at Noble Faubion,
nfaubion@netzero.com because this is all that I am waiting for before
putting my system together (I have a 10 foot parabolic fiberglass
satellite dish and other parts that are just waiting for me to
begin).

BTW, there are several New complete Copeland Scroll Compressors on
EBAY that go for between $200 and $400, which would make this project
feasible without a machine shop. After the excerpt, I have added a
ROUGH outline of how to proceed with this project.
____________________________________________________
The following is a quote from an InterNet article at:
http://www.redrok.com/engine.htm
"Scroll Expander.
Rankine rotary expansion generator.
David Wells and I have discussed the use of these expanders for use
in Rankine engines. Here is my concept. Take a Copeland Scroll
Compressor complete with its 3-phase induction motor almost off the
shelf. This complete assembly is in a sealed metal container. If high-
pressure gas is connected to the expander it rotates and applies
torque to the induction motor. The induction generator can be
directly connected to the power grid.
One disadvantage of using the Copeland unit is the inability to use
steam. The induction generator and bearings are exposed to the
working fluid. Steam will destroy these components. This requires
fluids other than steam.
propane
I have chosen propane as it is low in cost and has about the right
working pressure. Butane or pentane are also candidates. These fuel
gases are a much better choice than the standard refrigerants
primarily because of cost but also because they are non-ozone
depleting gases. The total system must be completely sealed to retain
the gases.
These gases are compatible with refrigeration oils which are used for
scroll and bearing lubrication. The oil is pumped from the low-
pressure sump to the inlet where it passes through the scroll. This
pump operates continuously whenever the expander is turning to
provide lubrication. Some of the oil will pass through the boiler as
dissolved oil in the fluid and return as a mist, which also passes
through the scroll. The boiler must be designed properly to prevent
oil accumulation. One method could be the use of float type oil
separators in low trap sections that let the oil pass through to the
boiler outlet.
A second pump pressurizes the condensate and injects it into the
solar boiler. The quantity of fluid injected is regulated by the
quantity of fluid in the boiler. The objective is to make sure that
the boiler is not so full as to let liquid pass out of the boiler and
into the expander. This would be called liquid slugging and is
detrimental to the expander.
The oil used in the system must be capable of sustained operating
temperatures in excess of 600 F. without deterioration."
__________________________________________________

Rough Outline of a Plan to Build a Solar/Propane Rankine Cycle
Electric Generating System

This plan describes a system that is the closest that one could get
to a turnkey solution as far as I have found. And, the scroll
compressors are cheap enough that one could replace them every 6
months, and still be ahead.
New Copeland Scroll Compressors are offered on ebay and the current
prices are low.

If this is a feasible concept, then here is what I see.

1) One will have a Copeland Scroll Motor/Generator setup ready to
plumb into the system.
2) One would have to have to have a satellite dish probably bigger
than necessary (up to 12 feet diameter) ready to be lined with
aluminized mylar as the reelecting surface and mounted on a pole in
cement in a suitable location---unblocked view of the sun in all
seasons. .
3) Use, as shown in the article above, Propane as the motive medium.
4) Decide how to build a heavily insulated tank, hopefully on a
concrete pad with concrete walls/top in the ground, (this tank does
not have to be pressurized, but if the heat causes any pressure
buildup, it must be vented to atmosphere) to contain the storage
medium and decide whether to use molten salt or mineral oil, or some
other recommended storage medium. I say use molten salt in the
storage tank, and use a mineral oil loop between the solar satellite
dish concentrator and the storage tank as the transferring medium.
5) Then, use another closed loop of liquid Propane passing through a
flash heat exchanger within the molten salt tank to convert the
relatively low-pressure propane into the motive high-pressure propane
gas to power the scroll compressor.
6) Route the pressurized Propane Gas to the inlet (the original
outlet) of the Copeland Scroll Compressor and route the outlet (the
original inlet) to another heat exchanger acting as a
radiator/cooling condenser to cool the propane back into the liquid
state.
7) Add a pump that will force the liquid propane into the propane-
holding tank ready to be fed into the flash heat exchanger within the
high temperature storage tank and the process begins all over again.
8) Use a valve to limit the flow of propane through the Copeland
Scroll Compressor based upon maintaining the desired speed that the
compressor is rotating.
9) A lubricating oil must be found that will withstand the expected
high temperatures (maybe not so high since we will have a much lower
temperature relative to water-to-steam temperatures), then we will
have a viable solution to the lubrication problem.
10) A fairly simple oil trap is all that will be needed, since the
propane vapor can still ingest oil droplets into the scroll
compressor inlet as long as it is a small quantity and does not
become too large. A simple separator trap will minimize the
lubricating oil that would be fed back into the scroll compressor
11) Fabricate the dish tracking system according to the information
we already have.
12) Specify the control valves and fabricate the heat exchangers
using stainless tubing and plumbing techniques.
13) Hook the AC electrical power to an AC-to-AC converter and then
to a Grid Tie Box.

NOTE: Did you notice that machine shop has NOT been mentioned here?
That is all taken care of by this concept. Purchasing plans is not
needed and no machine shop is needed. Just standard shop hand
tools, a drill press and a workbench. And, the rest is just
plumbing in the tubes/pipe/hoses and and wiring the electrical
outputs. Wire up the sensors and controls required, and get a
licensed electrician to wire the AC output to its destination. This
has become the SIMPLEIST SYSTEM WE HAVE FOUND, YET!
Finally, if you know anyone who has experience with converting
Copeland Scroll Refrigeration Compressors to a Copeland Scroll
Propane Motor/Generator, get them in contact with me at
nfaubion@netzero.com