u/Working_Cap4097

This question stems from three assumptions

1. In a rankine cycle typically the majority of heat input occurs when taking a condensed liquid back to gas state.

2. Solar thermal systems can be designed to collect heat economically at low temperatures.

3. Rankine cycle efficiency is proportional to the absolute temp difference

From those 3 assumptions i started to wonder if its possible to construct a working rankine cycle where low temp solar heat provides heat of vaporization and majority of cycle heat input (60%-70%)at 180 deg F and slightly subatmospheric pressures and a combustible fuel source then superheats this saturated steam to 1000 deg F to get a decent overall cycle efficiency for modest addition of energy.

The obvious challenge i see is with a good condenser the cycle would only have \~10 psi of differential pressure to drive a heat engine. The engine would have to be very high volume to work with the reduced energy density. That would be a challenge but perhaps not a show stopper. Working with such low differential pressures would provide the cycle an advantage of being inherently safe.

Anyways maybe im missing something else, what do the experts say is this cycle even possible?

This question stems from three assumptions

1. In a rankine cycle typically the majority of heat input occurs when taking a condensed liquid back to gas state.

2. Solar thermal systems can be designed to collect heat economically at low temperatures.

3. Rankine cycle efficiency is proportional to the absolute temp difference

From those 3 assumptions i started to wonder if its possible to construct a working rankine cycle where low temp solar heat provides heat of vaporization and majority of cycle heat input (60%-70%)at 180 deg F and slightly subatmospheric pressures and a combustible fuel source then superheats this saturated steam to 1000 deg F to get a decent overall cycle efficiency for modest addition of energy.

The obvious challenge i see is with a good condenser the cycle would only have ~10 psi of differential pressure to drive a heat engine. The engine would have to be very high volume to work with the reduced energy density. That would be a challenge but perhaps not a show stopper. Working with such low differential pressures would provide the cycle an advantage of being inherently safe.

Anyways maybe im missing something else, what do the experts say is this cycle even possible?