Parasitic power of heliostat drives

For a power tower case with 9868 heliostats and 0.025 kW-hr start-up and 0.055 kW per heliostat, the hourly data is showing 0.000219 MWe during the start-up hour and 0.000151 MWe during tracking hours. These results appear to be off by a factor of 1000 or more. Can you tell me how the heliostat parasitic power is calculated at each time step and whether or not you believe there is an error in these numbers?

Hello,

There is a bug in the power tower's calculation of heliostat drives calculation. SAM reports the value in the incorrect units. These losses are small compared to the system's total annual output, so the bug should not have a big impact on techno-economic metrics.

That will be fixed in the next version of SAM that we plan to release in early 2016.

Thank you for pointing out the problem.

Best regards,
Paul.