LENI Control Systems vs LENI Control Techniques

LENI is so complicated it can be easy to confuse control systems with control techniques.

Control Systems (in LENI terminology) are illustrated by this graph:

There are four of them and they are to do with how (intelligent sensor controlled) lighting reacts to the presence and absence of (forgetful) people. 

Fo, occupancy, is a measure of whether the room is occupied or not in a given time period. 

Fo = 1 if the lights are controlled centrally and the controller (human or automatic) does not know or care whether the rooms are occupied or not.

Fo < 1 if the room lights are switched on and off according to whether the room is in use or not. Again it could be a manual human control system (on off switch) or an automatic presence detecting system.

You'd think that...

Fa = 1 - Fo

...and that is true for Manual On/Auto Off, but not for any of the other three. I can only imagine that the curve for Manual On/Auto Off is the best one. A person enters the room, switches on the light, and even if s/he is forgetful, the automatic system will switch off the lights when the person leaves.

The manual on/off switch presumably takes into account the fact that lights can be left on by mistake when a persons leaves and the room becomes empty.

Here's my own personal idea about the graph:

So that was the Control Systems (Occupancy Control Systems would be a better name).

Then there are Control Techniques, there are eight of them, and specify how (intelligent sensor controlled) lighting reacts to the daylight supply of the room. To give them their full name they are Daylight-Responsive Control Techniques. They are summarized in this table:

 

This table needs some explanation. It is a look-up table, given three parameters you can lookup the output. The output is Fdc, used to calculate the Daylight Dependency Factor. 

The first input is type of control, which is basically the first four columns in the above table. There are eight of them (from I to VIII).

The second input is daylight availability, as a simple choice between three options, Low Medium and Strong.

The third input is lux required, maintained illuminance, as an option between 300lx, 500lx and 750lx.

 

Summarizing:

 

...and the output from the table lookup is used in the formula for Fd... 

Overview of the LENI EN 15193-1 formulas.

Lets look a bit more into the top level formulas of LENI...

 ...and this is part of the numerator of the LENI formula...

...but what do all those terms mean?

The simplest term is Pn, the total installed power for lighting, ignoring emergency lighting and charging of emergency lighting batteries. The n stands for "normal" I presume, as opposed to "emergency" or "charging".

Fc (more on this here) can reduce the weight of Pn because constant illuminance control (CIC) can reduce the power used to illuminate the room. This can happen because sunlight enters the room and electronic controllers react to it and reduce the power driving the luminaires.

Fo is the occupancy factor and takes into account that often lights are switched off when  rooms are not occupied. For example a store cupboard may have 50W of lighting installed, but it is only ever switched on when someone goes into it to get a broom. Say 0.1 or 10% of the time. This would make the actual consumption be calculated at 5W (not 50W).

The terms in square brackets are a way of splitting the calculation into day-time and night-time periods.

td is day-time hours. tn is night-time hours.

td x Fd: is a term which can be thought of as: "how much lighting will I need during the day":

• Fd is 0.0 if there is always enough natural light during the daylight hours. 
• Fd is 1.0 if artificial lighting is always required during daylight hours, for example in a room with no windows, no natural light.
• Fd is somewhere between 0 and 1 if, during the day, you sometimes need to switch a light on, but not always.

tn does not have a factor because you know you need lighting at night-time. And if nobody goes into the room at night-time is handled by Fo, the occupancy factor.

So...

 Fo[(td x Fd) + tn]

...handles the energy consumption change because occupancy of the room, requirement for lighting energy during the day and requirement for lighting energy during the night.

The next entry is on constant illuminance control.