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 LENI: Lighting Energy Numeric Indicator


LENI values have been with US for approximately 10 years now, however with more and more planning specifications today demanding the computation of LENI ideals, they're starting to become essential for most good lighting designs. In this guidebook, we shall try to clarify just what the LENI is, the factors that go into computing the worth and ways to compute it yourself using both easy and comprehensive processes.

As we might want to assist if all that fails and you still need some help with you LENI computations please do contact us.

What is LENI (Lighting Power Numerical Indicator)?

The LENI (Lights Vitality Numeric Index) system provides an alternative way of computing the lighting energy performance of a structure. Where as each luminaire is normally assessed because of its energy efficiency (for example a luminaire without any controls should have the absolute minimum efficiency of 60 luminaire lumens per circuit watt), the LENI procedure computes the specific energy used in KWh per square meter per year. This amount is subsequently evaluated against an optimum standard worth determined by the illuminance (lux) required within a space.

Having of demonstrating the compliance of the lighting systems, an alternative method provides engineers with significantly greater flexibility in their own style, allowing to get a wider collection of methods light types, and controls to be utilized.

Just how to Calculate the LENI Value?

There are just two main types of computing the LENI worth of a space. The first is the straightforward method put down within the 2013 Non-Domestic Building Services Compliance Guide. The second is the more in-depth and exact procedure put down within the BSI British Standard BS EN 15193:2007 Energy Performance of Buildings – Energy Requirements for Lighting.

For the many exact results, whichever approach you decide to utilize, the LENI calculations should really be completed on a per space basis (as different rooms like offices and circulation areas will likely possess very different luminaire types and control-systems).

No real matter what procedure you prefer to work with, there are some variants which are typical to both that before undertaking the computations, you will need to know. These are defined below:

Complete Installed Lights Power (Pn) – The complete strength in watts for all of the luminaires inside a room/place.

Absolute Installed Get A Grip On Parasitic Power (Ppc) – The total power in watts of each of the get a grip on techniques inside a room/area when the lamps aren't in use.

Complete Installed Emergency Lighting Charging Power (Pem) – The complete getting power in watts of all emergency luminaires in a room/area.

Conventional Yr Period (ty) – Moment in hours in 12 months, taken as 8760 hours.

Sunlight Using Hours (td) – Operating Hrs of the lighting when daylight exists.

Low-Sunlight Operating Hrs (tenn.) – Operating Hours of the lighting when day isn't present.

Emergency Lighting Charging Hours (te) – How many hours during which the emergency light batteries are billed.

The next management variables are used within both the Easy and Comprehensive calculation techniques, however their beliefs can change according to the approach utilized. To determine your constant and sunlight illuminance factors please notice either the 2013 Non-Domestic Constructing Providers Compliance Information for the BS EN 15193:2007 or the simple process regular for the in-depth procedure that is.

Occupancy Factor (Fo) – When occupancy controls, the variable that relates to the lighting ability are in spot. With respect to the sort of occupancy control this value will fluctuate between ONE and 0, when there is no occupancy control the factor is taken as 1.

Daylight Variable (Fd) – The factor that relates to the lighting strength when daylight controls come in place. Determined by the sort of daylight manage and amount of sunlight received this may differ between 1 and 0, if there are not any daylight controls the factor is obtained as 1.

Constant Illuminance Variable (Fc) – The factor that is related to the lighting energy when continuous illuminance control is in location. With respect to the maintenance element of the luminaires this value can differ between ONE and 0, if there isn't any persistent illuminance get a grip on the factor is taken as 1.

The Straightforward Process

As stated previously, the approach that was straightforward is taken from your 2013 Low-Domestic Creating Solutions Conformity guide and consists of these equations.

First calculate the entire parasitic energy use (If controls are employed the parasitic power worth may be presumed to be 0.3 W/m2).

Ep=0.3 × Area × ty

Then calculate the daytime energy use.

Ed=(Pn × Fo × Fd × Fc × td)/1000

And the night-time energy use.

En=(Pn × Fo × Fc × tn)/1000

Finally calculate the overall energy per-square metre (which is per year). That is your LENI value.


Along with your LENI value finally calculated it can be compared by you against the advised maximum values inside the Low-Domestic Constructing Solutions Compliance Manual to eventually discover if your lighting design will honor.


The Detailed Procedure

The detailed method is required from the BSI British Regular baloney EN 15193:2007 Energy Performance of Properties – Energy Requirements for Lighting. For calculating the vitality usage that is last, the computations is pretty just like the straightforward approach, just how these are calculated and the greatest big difference together with the method that is detailed is the values for the control variables.

First compute the lights electricity that is used to illuminate the building.

Wl=(Pn × Fc)  × [(td × Fo × Fd)+(tn × Fo)]┤┤/1000

Then calculate the parasitic vitality necessary for the control-systems and emergency lights charging.

Wp=(Ppc × [ty-(td+tn)]+(Pem × te)┤)/1000

Eventually calculate the overall vitality per square metre per (that will be per year). This really is your LENI worth.


The LENI worth may subsequently be compared against the Standard Beliefs inside the British Standard.


Exactly how we are able to help?

We’ve attempted to explain LENI calculations in the most easy to understand way possible, nevertheless we know that equations such as for example those above may perhaps not be everyone’s thought of a good moment. This is where we might help. At Ecodraw Sustainability Consultants and Energy Assessors we love nothing more than carrying out complicated calculations, so if you demand the LENI values to your illumination design please con-Tact us today.

Creation date: Mar 29, 2017 2:06 am     Last modified date: Mar 29, 2017 2:06 am   Last visit date: Jun 3, 2017 10:13 am     link & embed ?...
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