The Solar PV cell has an efficiency of 25-40%.

Now steam turbines run by coal or some other fuel have an efficiency of approximately 60-80%

What is the efficiency of steam turbines run by Solar energy? Are there any energy losses when using solar energy to heat up water instead of using something like coal?

For eg: See this video. What is the efficiency of these solar powered turbines? Efficiency interms of total energy out put vs total solar energy incident. How does it compare to the efficiency of energy generated by Solar PV cells? Would PV panels installed in a similar volume generate more electric power?

  • $\begingroup$ So calculate it: (power in or required) / (power out or wanted). What about 24/7 requirements? Check out Solar Engineering of Thermal Processes by Duffie & Beckman. $\endgroup$
    – Solar Mike
    Commented Aug 9, 2023 at 6:51
  • $\begingroup$ How are you proposing to use the sun to run this turbine? Is your efficiency versus the sunlight falling on an area? Steam doesn’t care how it was made. $\endgroup$
    – Tiger Guy
    Commented Aug 9, 2023 at 7:25
  • $\begingroup$ @SolarMike I'm not sure the how much loss happens while reflecting solar light and converting the heat into steam $\endgroup$
    – Hari Kumar
    Commented Aug 9, 2023 at 7:33
  • $\begingroup$ @TigerGuy yes, I want to know the percent of total solar energy falling on an area which is converted to electricity. $\endgroup$
    – Hari Kumar
    Commented Aug 9, 2023 at 7:34
  • 2
    $\begingroup$ Efficiency by itself isn't important, (but it is of interest). There's no reason to compare the efficiency of PV with solar thermal. What you want to compare is ROI and levelized cost of energy production. $\endgroup$
    – Phil Sweet
    Commented Aug 11, 2023 at 10:30

1 Answer 1


Less than 31.25% when going to electricity per wikipedia. (If you just needed heat for heating a room, it's a different story- 80% is not unheard of, but you'd be doing well to get half that into water to make PRESSURIZED steam because you can't really insulate on the solar collector itself and mechanisms such as reflectors and heat exchangers for collecting to an area with lower thermal losses will incur their own inefficiencies. Followed by your 70% turbine, that multiplies to ~30% at 1 significant digit )

Whether it's better than solar photovoltaic, depends on which panel, per your 25-40%.

Of all of these technologies the solar dish/Stirling engine has the highest energy efficiency. A single solar dish-Stirling engine installed at Sandia National Laboratories National Solar Thermal Test Facility (NSTTF) produces as much as 25 kW of electricity, with a conversion efficiency of 31.25%.[66]

Solar parabolic trough plants have been built with efficiencies of about 20%.[citation needed] Fresnel reflectors have a slightly lower efficiency (but this is compensated by the denser packing).

The gross conversion efficiencies (taking into account that the solar dishes or troughs occupy only a fraction of the total area of the power plant) are determined by net generating capacity over the solar energy that falls on the total area of the solar plant. The 500-megawatt (MW) SCE/SES plant would extract about 2.75% of the radiation (1 kW/m²; see Solar power for a discussion) that falls on its 4,500 acres (18.2 km²).[67] For the 50 MW AndaSol Power Plant[68] that is being built in Spain (total area of 1,300×1,500 m = 1.95 km²) gross conversion efficiency comes out at 2.6%.

Efficiency does not directly relate to cost: total cost includes the cost of construction and maintenance.

From the first web result after google's shenanigans of attempting to provide what people ask and guessed answers.


Efficiency comparisons only make sense when you have the same input and output. It wouldn't be good to have to burn coal to make light to feed a photovoltaic panel to generate electricity, just as it would be bad to have to grow plants, compress the hydrogen out them to make coal to then power something. Pay attention instead to what you need and what you have that you can exchange for it, seeking the most direct path.


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