Alcohol as a working fluid?

Question

Alcohols with their lower boiling point and overall non-toxicity, could they be used as a turbine working fluid instead of steam water?

Answer 1

Yes - for certain applications. Low-energy, low-temperature, small installations, possibly 'accessory' power where providing a bit of weak rotary power to some point of machinery would be difficult but a good heat gradient is at hand and can be utilized - generally things where you have a heat source above your alcohol boiling point but not providing nearly enough heat to make sense with a steam turbine.

There are numerous problems associated with possibility of leaks, evaporation, cost, non-negligible toxicity, flammability, and a lot of other headaches simply absent in case of water - and while they don't matter much in case of small to tiny installations, they become significant with anything larger. And then there's the significant problem: latent heat of evaporation of alcohol is vastly smaller than that of water, meaning you're getting much less work out of the Carnot cycle, you're wasting heat, it's simply inefficient comparing to water. And again, if you have some waste heat that would be radiated out anyway, you can tap into it with a simple small alcohol-based engine and it will work just fine providing some meager work which can be used, e.g. for regulation through mechanical circuitry, gentle stirring, slow forced circulation and so on, without need to provide other sources of power - a side-task to whatever the machine is doing. But if you think about employing it as the primary "target" of your thermal power production, in order to e.g. produce electricity, it's a very bad choice of working liquid.