[Radiance-general] Daysim and results

[Christopher Rush]

Do you have the lighting control algorithm set to be dimming? If it was switching on and off for the same hours each year in two simulations, the energy use would be double. If the calculation assumes lights are dimmed, the 8% difference is only due to the interpolation difference between the low end energy use (minimum ballast power) and the upper end of the energy use. In other words, maybe you have many hours that daylight provides nearly all of the specified lux requirement, so your lights are always dimmed to a fraction of only 5W/m² or 10W/m² for most of the year at any times they are set to on.

I’m also not sure if your control algorithm might also assume that if you say the 10W/m² provides 600 lux and the 5W/m² provides 300 lux, but your daylight autonomy threshold is set to 300 lux, the calculation may never use the full 10W/m² load. I’m a bit out of practice with Daysim so I can’t recall for sure if either of these scenarios are likely to occur without knowing it.

-Chris

From: Per Haugaard [mailto:perhaugaard at yahoo.dk]
Sent: Wednesday, September 02, 2015 9:13 AM




The annual energy consumption goes from e.g. 100 kWh/m2 to 108 kWh/m2 when going from an installed lighting power from 5W/m2 to 10 W/m2.
It is the 8% increase I do not quite understand.
Any input is much appreciated.

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