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Module 5 Thermal mass and comfort: the role of time. Plan. Thermal mass and comfort: the role of time An example from India Control temperature based on the Adaptive Model Adaptive in SARA project. The adaptive approach to thermal comfort (1).

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slide2
Plan

Sustainable Architecture Applied to Replicable Public Access Buildings

www.sara-project.net

Contract:TREN/04/FP6EN/S07.31838/503118

  • Thermal mass and comfort: the role of time
  • An example from India
  • Control temperature based on the Adaptive Model
  • Adaptive in SARA project
the adaptive approach to thermal comfort 1
The adaptive approach to thermal comfort (1)

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

  • The adaptive approach assumes an adaptive principle:
  • If a change occurs such as to produce discomfort, people react in ways which tend to restore their comfort.
  • These changes take place over varying time periods and may be changes made to the environment or to the person:
the adaptive approach to thermal comfort 2
The adaptive approach to thermal comfort (2)

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

  • The adaptive approach therefore sees comfort as part of an interaction between buildings and occupants in the context of culture and climate.
  • Comfort temperature changes with changes of clothing and other factors with weather and season
  • The feed-back nature of the system has led to reproducible results
slide5

Generalising from field studies I

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characteristic time periods
Characteristic time periods

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  • Instantaneous – particularly the taking on or off of clothing in response to – or anticipation of – a change in conditions (e.g. going out of doors)
  • Within day - responses to a change in the environment within the day
  • Day to day – e.g. reactions to changes in the weather
  • Longer term – resulting from the changing seasons, often driven by the prevailing culture.
generalising from field studies
Generalising from field studies

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • The indoor temperature in a particular building is not always known
  • But the indoor temperature in buildings without heating or cooling (free-running) generally follows the outdoor temperature
  • In these buildings the comfort temperature will therefore also follow the outdoor temperature:
slide8

Generalisingfrom field studies II

Sustainable Architecture Applied to Replicable Public Access Buildings

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Each point on the graph is the mean from a particular survey

over what time period
Over what time period?

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • Comfort temperature changes with outdoor temperature: this does not happen instantaneously, but over time
  • A full investigation would require time-series analysis, but this is very difficult unless the data are complete and continuous.
  • Most comfort data come from offices and are therefore intermittent and separated by nights and weekends
  • A time series must therefore be assumed
slide10

Exponentially weighted running mean temperature

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

Trm = (1-).{Tod-1 + .Tod-2 +2Tod-3…..}

Trmn = (1-).Todn-1 + .Trmn-1

 is a constant ( < 1),

Trm Running mean temperature

Trmn is Trm on day n

In this database TrmX = Trm for  = X/100

Tod Daily mean temperature

running mean temperature
Running mean temperature

Sustainable Architecture Applied to Replicable Public Access Buildings

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deciding the optimal time constant for the time series
Deciding the optimal time constant for the time series

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

  • The greater the value of  the more slowly the time series changes
  • Data from field surveys in Europe allow us to estimate the best value for 
  • We can calculate the correlation
  • coefficient of comfort temperature (Tc) on different values of Trm
slide13

Correlation of comfort temperature (Tc) and daily mean outdoor temperature (Tod) with Trm for increasing values of . (1)

Sustainable Architecture Applied to Replicable Public Access Buildings

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Maximum correlation with Tc when  is about 0.8 (TR80)

slide14

Correlation of comfort temperature (Tc) and daily mean outdoor temperature (Tod) with Trm for increasing values of . (2)

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • The maximum correlation occurs when the value of  is 0.8
  • This implies that the comfort temperature
  • changes in an exponential manner with a half-life of about 4 days

Graph showing the relative change of Trm80 following a step change of temperature on day 0

buildings
Buildings

Sustainable Architecture Applied to Replicable Public Access Buildings

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How are the needs of thermal comfort reflected in buildings?

slide16
Sustainable Architecture Applied to Replicable Public Access Buildings

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Time Lag = tL

Decrement Factor = AI /AO

External Temperature modulation

Internal Temperature modulation

slide17
Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

T-Tc

Increasing

Discomfort

conclusions
Conclusions

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • People can adapt to a range of temperatures
  • However they take time to adjust to changes in the temperature
  • A heavyweight construction helps in two ways:

1. the mean temperature changes more slowly

2. the daily range of temperature is reduced

  • Free-running heavy-weight buildings are therefore more likely to be comfortable.
2 an example from india

2. An example from India

Hotel Suraj in Jaisalmer in the Thar desert of Rajistan

With acknowledgements to: Dr Jane Matthews BA, MSc, PhD

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slide20
Sustainable Architecture Applied to Replicable Public Access Buildings

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The design of the building allows for a variety of forms with varying thermal mass characteristics

slide21
Sustainable Architecture Applied to Replicable Public Access Buildings

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The massive but airy principal reception room

slide22
Sustainable Architecture Applied to Replicable Public Access Buildings

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The heavy-weight staircase

slide23
Sustainable Architecture Applied to Replicable Public Access Buildings

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The structure with thick mud floors and plenty of air penetration

slide24
Sustainable Architecture Applied to Replicable Public Access Buildings

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Lightweight character of the upper floor

thermal mass is exploited to provide variety throughout the building
Thermal mass is exploited to provide variety throughout the building

Sustainable Architecture Applied to Replicable Public Access Buildings

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slide26

Increasing Time lag

Sustainable Architecture Applied to Replicable Public Access Buildings

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Increasing Time lag

slide27
Sustainable Architecture Applied to Replicable Public Access Buildings

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slide28

Daily mean temperatures outdoors and in the basement over one year, illustrating an annual decrement factor and time-lag

Sustainable Architecture Applied to Replicable Public Access Buildings

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slide30

State of the art review

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  • The International Standard for indoor temperatures favours the provision of constant temperatures in buildings.
  • Research analysing field work throughout the world has shown that the temperature which people find comfortable varies with season and climate.
  • Recent work has suggests that the comfort temperature indoors can be defined by a time-series of the outdoor temperature.
slide31

State of the art review (1)

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  • This means that comfort can be achieved using less energy because the indoor temperature follows that outdoors.
  • It also means that well designed buildings can fall within the range of temperatures which are comfortable without the use of air conditioning.
slide32

State of the art review (2)

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  • An algorithm was developed for the prediction of comfort temperatures in buildings using the outdoor temperature.
  • This algorithm has been tested for UK and EC conditions using dynamic thermal simulations and was also tested in actual buildings.
  • The use of such an algorithm can be shown to produce energy savings of up to 25% when it is used to define the set temperature in air conditioned and partially mechanically ventilated buildings.
state of the art review 3
State of the art review (3)

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • In air conditioned (AC) buildings this is used as the set-point temperature.
  • In NV buildings the same input information will be used to assess whether the building is likely to provide indoor comfort.
  • This means that it is more dependent on the exact nature of the building and the controls over indoor conditions which it affords.
developing the adaptive mechanism 1
Developing the adaptive mechanism (1)

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Main assumption

  • The approach is based on the assumption that the comfort temperature is changing with time in a way which is related to the outdoor temperature.
developing the adaptive mechanism 2
Developing the adaptive mechanism (2)

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  • The comfort temperature (Tc) can be calculated from the value of the globe temperature (Tg) and the thermal comfort vote (TF) using the equations:

TF = a Tg + b

The globe temperature is used as an approximation to the operative temperature.

developing the adaptive mechanism 3
Developing the adaptive mechanism (3)

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • One problem for the adaptive approach to thermal comfort, which relates the comfort temperature inside buildings to the outdoor temperature is to characterise the rate at which the comfort temperature changes.
  • A common measure of outdoor temperature used as a predictor for indoor comfort temperature is the exponentially-weighted running mean of the daily mean outdoor temperature.

Trm = (1-).{Tod-1 + .Tod-2 + 2Tod-3…..}

developing the adaptive mechanism 4
Developing the adaptive mechanism (4)

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  • The way in which the running mean temperature changes is equivalent to the decay of a radioactive source with a characteristic half-life.
  • The use of an infinite series would be very time consuming but it can easily be reduced to
  • The values of and a, b,  can be determined by using statistical analysis.

Trmn = (1-).Todn-1 + .Trmn-1

thermal comfort surveys scat project 1
Thermal Comfort Surveys-SCAT project (1)

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • 25 buildings were surveyed across the UK, France, Sweden, Greece and Portugal by members of the SCATs consortium.
  • This data formed 3 distinct databases of thermal comfort
  • The data collected included indoor and outdoor temperatures, thermal comfort responses, occupant use of controls, demographic data of building occupants, clothing insulation and metabolic rate.
  • Approximately 25000 responses are available for analysis
thermal comfort surveys scat project 2
Thermal Comfort Surveys-SCAT project (2)

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • Temperature - comfort vote (7 point scale) and preference (5 point scale)
  • Air movement - comfort vote (7 point scale) and preference (5 point scale)
  • Humidity -comfort vote (7 point scale) and preference (5 point scale)
  • Lighting - comfort vote (7 point scale) and preference (5 point scale)
  • Noise - comfort vote (7 point scale) and preference (5 point scale)
  • Air quality vote (7 point scale)
  • Overall comfort (6 point scale)
  • Perceived productivity (5 point scale)
the adaptive algorithm
The adaptive algorithm

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=0.2

developing controls 1
Developing Controls (1)

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What has to be implemented at BMS level is the following:

  • The actual outdoor temperature is measured once every hour, added up, and the average outdoor temperature.
  • The Running mean temperature is calculated as:

TRMn =  * TDMn-1 + (1- ) * TRMn-1

      • TRM = Running mean temperature
      • TDM = Actual average temperature
      •  is set default to 0.2.
developing controls 2
Developing Controls (2)

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The Control temperature is calculated as

  • If the running mean temperature is below 10 °C, the Control temperature is set to a fixed value of 22.88 °C.
  • In other cases, the Control temperature is calculated as:

Tc = a * TRM + b

Where : - a = 0.302

- b = 19.39

adaptative control in the sara project 1
Adaptative Control in the SARA project (1)

Sustainable Architecture Applied to Replicable Public Access Buildings

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  • The control algorithm is used to calculate the comfort temperature setpoint at the BMS level depending on the historical outdoor temperature in a very specific way explained elsewhere. The comfort temperature setpoint is then used to control the indoor temperature. What has to be implemented at BMS level is the following:

The actual outdoor temperature is measured once every hour, added up, and the average outdoor temperature is calculated once every day at 7 o’clock (no adjustment for daylight saving time).

adaptative control in the sara project 2
Adaptative Control in the SARA project (2)

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

  • The Running mean temperature is calculated as:
        • TRM = Running mean temperature
        • TDM = Actual average temperature
        • TRMn = c * TDMn-1 + (1-c) * TRMn-1where the constant c is set default to 0.2.
adaptative control in the sara project 3
Adaptative Control in the SARA project (3)

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

  • The Running mean temperature is calculated as:
        • TRM = Running mean temperature
        • TDM = Actual average temperature
        • TRMn = c * TDMn-1 + (1-c) * TRMn-1where the constant c is set default to 0.2.
adaptative control in the sara project 4
Adaptative Control in the SARA project (4)

Sustainable Architecture Applied to Replicable Public Access Buildings

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Contract:TREN/04/FP6EN/S07.31838/503118

  • The Control temperature is calculated as
      • If the running mean temperature is below 10 °C, the Control temperature is set to a fixed value of 22.88 °C.
      • In other cases, the Control temperature is:

- Tc = a * TRM + b

- where a = 0.302 and b = 19.39

adaptative control in the sara project 5
Adaptative Control in the SARA project (5)

Sustainable Architecture Applied to Replicable Public Access Buildings

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This algorithm was implemented at the BMS level in December 2007 and it is running in part of the building.