# Daysim and results

-Greg

···

Begin forwarded message:

From: Per Haugaard <perhaugaard@yahoo.dk>
Date: September 2, 2015 4:05:35 AM PDT

Dear user
Sorry to post my question in this forum, but since it deals with daylight I think that it's ok.

A brief question about Daysim and results.
I have made an analysis of a room where I compare the energy savings for artificial lighting by changing the ceiling reflectance. I look at two types of installed effect - 5 W/m2 and 10 W/m2. which is the only difference between the two calculations. There is no solar shading in the model.

I use the same model for both analyzes. This means that I only make a one calculation of daylight coefficients.
The light is controlled in both analyzes via photo sensors with dimming (photo-sensor control).

The for my question. Why is there a smaller increase in energy consumption of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power? Here I compare 2 x the energy consumption for 5 W/m2 with the energy consumption of 10 W/m2

I look forward to hearing from you

Best regards

Per Haugaard
_______________________________________________

Begin forwarded message:

From: Germán Molina Larrain <germolinal@gmail.com>
Subject: Re: [Radiance-general] Daysim and results
Date: September 2, 2015 6:01:00 AM PDT

Hello,

I think that might make sense. Imagine a room that is perfectly well daylit, where you never need to turn the lights on. It will not matter weather you installed 1W/m2 or 100W/m2, the energy consumption will always be 0kWh/m2.

I would expect that, since you doubled the Lighting Power in the room, the energy consumption also doubled. Does that make sense?

Otherwise... I am not quite sure how Daysim works.

Best,

Germán

2015-09-02 8:05 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:
Dear user
Sorry to post my question in this forum, but since it deals with daylight I think that it's ok.

A brief question about Daysim and results.
I have made an analysis of a room where I compare the energy savings for artificial lighting by changing the ceiling reflectance. I look at two types of installed effect - 5 W/m2 and 10 W/m2. which is the only difference between the two calculations. There is no solar shading in the model.

I use the same model for both analyzes. This means that I only make a one calculation of daylight coefficients.
The light is controlled in both analyzes via photo sensors with dimming (photo-sensor control).

The for my question. Why is there a smaller increase in energy consumption of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power? Here I compare 2 x the energy consumption for 5 W/m2 with the energy consumption of 10 W/m2

I look forward to hearing from you

Best regards

Per Haugaard

_______________________________________________

_______________________________________________

Begin forwarded message:

From: Per Haugaard <perhaugaard@yahoo.dk>
Subject: Re: [Radiance-general] Daysim and results
Date: September 2, 2015 6:12:43 AM PDT

Hi Germán,

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.

Best regards

Per Haugaard

Den 15:01 onsdag den 2. september 2015 skrev Germán Molina Larrain <germolinal@gmail.com>:

Hello,

I think that might make sense. Imagine a room that is perfectly well daylit, where you never need to turn the lights on. It will not matter weather you installed 1W/m2 or 100W/m2, the energy consumption will always be 0kWh/m2.

I would expect that, since you doubled the Lighting Power in the room, the energy consumption also doubled. Does that make sense?

Otherwise... I am not quite sure how Daysim works.

Best,

Germán

2015-09-02 8:05 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:
Dear user
Sorry to post my question in this forum, but since it deals with daylight I think that it's ok.

A brief question about Daysim and results.
I have made an analysis of a room where I compare the energy savings for artificial lighting by changing the ceiling reflectance. I look at two types of installed effect - 5 W/m2 and 10 W/m2. which is the only difference between the two calculations. There is no solar shading in the model.

I use the same model for both analyzes. This means that I only make a one calculation of daylight coefficients.
The light is controlled in both analyzes via photo sensors with dimming (photo-sensor control).

The for my question. Why is there a smaller increase in energy consumption of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power? Here I compare 2 x the energy consumption for 5 W/m2 with the energy consumption of 10 W/m2

I look forward to hearing from you

Best regards

Per Haugaard

_______________________________________________

_______________________________________________

Begin forwarded message:

From: Germán Molina Larrain <germolinal@gmail.com>
Subject: Re: [Radiance-general] Daysim and results
Date: September 2, 2015 6:21:02 AM PDT
To: Per Haugaard <perhaugaard@yahoo.dk>

mmm... Is one set of luminaires more efficient? or does one of them actually illuminates more?

2015-09-02 10:12 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:
Hi Germán,

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.

Best regards

Per Haugaard

Den 15:01 onsdag den 2. september 2015 skrev Germán Molina Larrain <germolinal@gmail.com>:

Hello,

I think that might make sense. Imagine a room that is perfectly well daylit, where you never need to turn the lights on. It will not matter weather you installed 1W/m2 or 100W/m2, the energy consumption will always be 0kWh/m2.

I would expect that, since you doubled the Lighting Power in the room, the energy consumption also doubled. Does that make sense?

Otherwise... I am not quite sure how Daysim works.

Best,

Germán

2015-09-02 8:05 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:
Dear user
Sorry to post my question in this forum, but since it deals with daylight I think that it's ok.

A brief question about Daysim and results.
I have made an analysis of a room where I compare the energy savings for artificial lighting by changing the ceiling reflectance. I look at two types of installed effect - 5 W/m2 and 10 W/m2. which is the only difference between the two calculations. There is no solar shading in the model.

I use the same model for both analyzes. This means that I only make a one calculation of daylight coefficients.
The light is controlled in both analyzes via photo sensors with dimming (photo-sensor control).

The for my question. Why is there a smaller increase in energy consumption of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power? Here I compare 2 x the energy consumption for 5 W/m2 with the energy consumption of 10 W/m2

I look forward to hearing from you

Best regards

Per Haugaard

_______________________________________________

_______________________________________________

Begin forwarded message:

From: Christopher Rush <Christopher.Rush@arup.com>
Subject: Re: [Radiance-general] Daysim and results
Date: September 2, 2015 6:44:27 AM PDT

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@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.

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

_______________________________________________

Dear userSorry to post my question in this forum, but since it deals with daylight I think that it's ok.
A brief question about Daysim and results.I have made an analysis of a room where I compare the energy savings for artificial lighting by changing the ceiling reflectance. I look at two types of installed effect - 5 W/m2 and 10 W/m2. which is the only difference between the two calculations. There is no solar shading in the model.
I use the same model for both analyzes. This means that I only make a one calculation of daylight coefficients. The light is controlled in both analyzes via photo sensors with dimming (photo-sensor control).
The for my question. Why is there a smaller increase in energy consumption of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power? Here I compare 2 x the energy consumption for 5 W/m2 with the energy consumption of 10 W/m2

I look forward to hearing from you

Best regards
Per Haugaard

Hello,

I think that might make sense. Imagine a room that is perfectly well
daylit, where you never need to turn the lights on. It will not matter
weather you installed 1W/m2 or 100W/m2, the energy consumption will always
be 0kWh/m2.

I would expect that, since you doubled the Lighting Power in the room, the
energy consumption also doubled. Does that make sense?

Otherwise... I am not quite sure how Daysim works.

Best,

Germán

···

2015-09-02 8:05 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:

Dear user
Sorry to post my question in this forum, but since it deals with daylight
I think that it's ok.

A brief question about Daysim and results.
I have made an analysis of a room where I compare the energy savings for
artificial lighting by changing the ceiling reflectance. I look at two
types of installed effect - 5 W/m2 and 10 W/m2. which is the only
difference between the two calculations. There is no solar shading in the
model.

I use the same model for both analyzes. This means that I only make a one
calculation of daylight coefficients.
The light is controlled in both analyzes via photo sensors with dimming
(photo-sensor control).

The for my question. Why is there a smaller increase in energy consumption
of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power?
Here I compare 2 x the energy consumption for 5 W/m2 with the energy
consumption of 10 W/m2

I look forward to hearing from you

Best regards

Per Haugaard

_______________________________________________

Hi Germán,
Thank you for your reply.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.

Best regards
Per Haugaard

···

Den 15:01 onsdag den 2. september 2015 skrev Germán Molina Larrain <germolinal@gmail.com>:

Hello,

I think that might make sense. Imagine a room that is perfectly well daylit, where you never need to turn the lights on. It will not matter weather you installed 1W/m2 or 100W/m2, the energy consumption will always be 0kWh/m2.

I would expect that, since you doubled the Lighting Power in the room, the energy consumption also doubled. Does that make sense?

Otherwise... I am not quite sure how Daysim works.

Best,

Germán

2015-09-02 8:05 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:

Dear userSorry to post my question in this forum, but since it deals with daylight I think that it's ok.
A brief question about Daysim and results.I have made an analysis of a room where I compare the energy savings for artificial lighting by changing the ceiling reflectance. I look at two types of installed effect - 5 W/m2 and 10 W/m2. which is the only difference between the two calculations. There is no solar shading in the model.
I use the same model for both analyzes. This means that I only make a one calculation of daylight coefficients. The light is controlled in both analyzes via photo sensors with dimming (photo-sensor control).
The for my question. Why is there a smaller increase in energy consumption of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power? Here I compare 2 x the energy consumption for 5 W/m2 with the energy consumption of 10 W/m2

I look forward to hearing from you

Best regards
Per Haugaard
_______________________________________________

mmm... Is one set of luminaires more efficient? or does one of them
actually illuminates more?

···

2015-09-02 10:12 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:

Hi Germán,

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.

Best regards

Per Haugaard

Den 15:01 onsdag den 2. september 2015 skrev Germán Molina Larrain <
germolinal@gmail.com>:

Hello,

I think that might make sense. Imagine a room that is perfectly well
daylit, where you never need to turn the lights on. It will not matter
weather you installed 1W/m2 or 100W/m2, the energy consumption will always
be 0kWh/m2.

I would expect that, since you doubled the Lighting Power in the room, the
energy consumption also doubled. Does that make sense?

Otherwise... I am not quite sure how Daysim works.

Best,

Germán

2015-09-02 8:05 GMT-03:00 Per Haugaard <perhaugaard@yahoo.dk>:

Dear user
Sorry to post my question in this forum, but since it deals with daylight
I think that it's ok.

A brief question about Daysim and results.
I have made an analysis of a room where I compare the energy savings for
artificial lighting by changing the ceiling reflectance. I look at two
types of installed effect - 5 W/m2 and 10 W/m2. which is the only
difference between the two calculations. There is no solar shading in the
model.

I use the same model for both analyzes. This means that I only make a one
calculation of daylight coefficients.
The light is controlled in both analyzes via photo sensors with dimming
(photo-sensor control).

The for my question. Why is there a smaller increase in energy consumption
of approximately 1 W/m2 by going from 5 W/m2 to 10 W/m2 installed power?
Here I compare 2 x the energy consumption for 5 W/m2 with the energy
consumption of 10 W/m2

I look forward to hearing from you

Best regards

Per Haugaard

_______________________________________________

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

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.

···

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

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

I sent this discussion to the daysim mailing list, which I think it was intended for originally. Please add responses there.

Also, we might think about posting the question to Unmet Hours.

Cheers,
-Greg