Tuning the power output of a reactor using fluid temperature

[half a cat]

I'm changing a solar thermal power mod to use a fluid power source internally. I'm trying to make its power output match the original power output, and I don't understand the result that I'm seeing.

I changed solar thermal collectors to be a reactor with a fluid energy source. The fluid is internal, players don't interact with it. A script changes the power output by changing the fluid temperature. For my test, I am using solar thermal power with a heat exchanger, a turbine, and a load that consumes all the power:

solar_thermal_setup.jpg (104.72 KiB) Viewed 164 times

Here is the power production for solar panels and 3 tiers of solar thermal (highest power on top). Solar thermal power output should follow the same curve as solar panels, but all the curves have a different shape in the morning and evening. I don't know why.

power-curves.png (30.4 KiB) Viewed 164 times

Based on the documentation, solar thermal should produce 60 * fluid_usage_per_tick * (fluid_temperature - fluid_default_temperature) * fluid_heat_capacity * effectivity watts. I follow this formula and I set effectivity to produce the peak power that I want. I also set the reactor's consumption to the peak power that I want. I only vary effectivity and consumption in the 3 tiers of solar thermal.

The script adjusts the fluid temperature on a curve matching the solar panel curve. Since that's the only variable in the formula, it should give me the right curve over the course of a day. Even if it doesn't, it should give me the same shape of curve for all 3 tiers. What could give me these different results? Any suggestions on how to fix it?

[half a cat]

I had put effectivity in the wrong part of the prototype, so it was being ignored.