The heat balance equation does not require lux as parameter, but watt. At the same time the energy usage is not lux dependant. A light will produce lux dependant on its type. It uses a set amount of energy. The lux/W ratio is a measure of how well it turns input energy into usable light.
If you are designing a project, you need to meet certain lighting requirements. Which lights you decide use to meet that need deturmines the energy use.
Dimming or switching individual or groups of lights off to meet the same lighting level (lux) requirements, is a stradegy that can be used to reduce the total input power. If the daylight through windows covers 50% of the lighting level requirements, then you can switch off 50% of the lights that would normally be needed to produce that lighting level without daylight. Again which lights were used in your design does not care what the lighting levels are.
EnergyPlus models your design, it does not design your lighting for you.
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Jean Marais
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On 19.06.2014, at 18:35, "vincent lacour vlacour@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Thanks Rahul, but this does not address the issue. Everything in Daylighting:controls is inLUX whereas everything in Lights is in Watts. What is missing is the efficiency of the lights, i.e. how much LUMEN you can get with 1W. With a led you get 50 lumen; with an incandescent light bulb you get only 10 lumen. There must be a lumen/watt ratio under the energyplus hood, but where????On Thu, Jun 19, 2014 at 6:09 PM, rahula7@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
If you look at the Daylighting:Controls object, there are a number of fields:
- Lighting control type- Minimum input power fraction for continuous dimming control- Minimum input power fraction for continuous dimming control- Number of control stepsThese fields combine to determine how much lighting power will be supplied after subtracting the daylight contribution. It's all there in the I/O Reference.Rahul
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