4 Energy Use in Buildings （建筑能耗）

use energy for lighting, heating or cooling.

energy use and built environment ?

use the minimum energy to achieve a best comfort built

environment.

To be energy efficient.

this chapter describes:

4.1 Energy use

4.2 Thermal comfort 热舒适4.3 Heat losses 失热量4.4 Heat gains 得热量4.5 Heat balance 热平衡

4.6 Energy consumption 能耗

4.1 Energy use

4.1.1 Energy terms（ 1 ） A fuel

（ 2 ） fossil fuels 化石燃料 coal, crude oil and natural gas

（ 3 ） non-renewable energy 不可再生能源 which can only be used once fossil fuels

（ 4 ） renewable energy 可再生能源 which are replenishable 可补给的 wind power, wave power 潮汐能

（ 5 ） primary energy 一次能源 coal ， oil ， natural gas

（ 6 ） transformation 能源的转化Fuels electricity, crude oil petroleum

（ 7 ） secondary energy 二次能源 which results from a transformation process.

Electricity, manufactured gas 人工燃气 ,

surplus hot water 废热水The secondary energy of electricity is only 30 to 40 per cent of the

primary energy contained in the original fuels

The rest is lost in the conversion and distribution processes.

（ 8 ） delivered energy 输出能源Is energy content as it is received by the consumer.

Pay for money

Some of the energy will be lost by conversion processes within the

building.

（ 9 ） useful energy 有用能Is the energy required to perform a given task.

It is useful energy that is required to balance the heat loss and heat gain

in a typical calculation.

Example:

Coal——electricity ——delivered energy——useful energy

4.1.2 Energy units

Joule 焦耳Megajoules 1MJ=106J

Gigajoules 1GJ=109J

Tonne of oil equivalent 吨石油当量1 tonne of oil equivalent = 41.87 gigajoules

= 107 kilocalcories

= 11630 kWh

= 396.8 therms

它近似地是能当量烧 100 立方英尺天然气.

4.1.3 calorific values 热值

Units: KJ/kg; MJ/kg

KJ/m3; MJ/m3

Some typical calorific values are quoted in table 4.1

Table 4.2 shows national energy consumption

4.2 What is Thermal Comfort?

- That condition of mindwhich expresses satisfactionwith the thermal environment.

ISO 7730

Definition

Thermal Comfort is a matter of many parameters - Not only the air temperature.

4.2.1 Factors affecting thermal comfort

Personal variables 个人因素• Activity • Clothing• Age • Sex

Physical variables 物理因素• Air temperature • Surface temperature• Air movement• humidity

The Six Basic Factors

Body Temperature 体温

• Normal body core temperature: 37 oC.• We have separate Heat- and Cold-sensors.

•Heat sensor 热感受器 is located in hypothalamus 下丘脑 . Signals when temperature is higher than 37 oC.

•Cold sensors 冷感受器 are located in the skin. Send signals when skin temperature is below 34 oC.

• Heating mechanism:•Reduced blood flow 减少血液流动 .•Shivering 发抖 .

• Cooling mechanism:• Increased blood flow 加速血液流动 .• Sweating (Evaporation) 出汗 .Hot Cold

37 oC 34 oC

Perception of Thermal Environment人对热环境的知觉

• Heat sensor in Hypothalamus send impulses when temperature exceeds 37 oC.

• Cold sensors sends impulses when skin temperature below 34 oC.

• The bigger temperature difference, the more impulses.

• If impulses are of same magnitude, you feel thermally neutral 热中性 .

• If not, you feel cold or warm. Warmimpulses

Coldimpulses Activity

感觉热 感觉热 感觉冷感觉冷

thermally neutral and thermal comfortable 中性和舒适之间的关系

冷热刺激的存在 刺激的延续时间 人体原有的状态

Cool & Cool &

Comfort !Comfort !

The Energy Balance 能量平衡

• Thermal Comfort can only be maintained when heat produced by metabolism 代谢 equals the heat lost from body.

HeatLost

HeatProdu-ced

• The transfer of the heat from the body is mainly by the process of convection, radiation and evaporation

The dry heat loss (R+C) represents ~70% at low Clo-values and ~60% at higher Clo-values

Conduction (K) is normally insignificant

compared to the total heat exchange

The Energy Balance 能量平衡

Heat Balance Equation热平衡方程

• General heat balanceS = M - W - E - (R + C)

whereS = rate of heat storage of human body 蓄热率M = metabolic rate 代谢率W = mechanical work done by human body 机械功E = rate of total evaporation loss 人体的蒸发（汗液蒸发和

呼出的水蒸气）散热率R + C = dry heat exchange through radiation & convection

人体外表面通过辐射和对流的散热率

0.8 Met

1 Met

8 Met

4 Met

Metabolic rate, M 代谢率Met Value Examples

1 met = seated quiet person (100 W if body surface area is 1.7 m2);

The output from adult females is about 85% thatis about 85% that of males.

Met Value Examples

Walking 3.5 km/h2.5 MET

Jogging8 MET

After 10 MET

Met Value Examples

Table 4.3 lists typical heat outputs from an adult male

• 1 Clo = Insulation value of 0,155 m2 oC/Wrange form 0clo to 4clo.• table 4.4 shows the value of different types of clothing

0,15 Clo0.5 Clo

1.0 Clo

1.2 Clo

Clothing : act as a thermal insulator for the body

Calculation of Clo-value (Clo)

Clothing : act as a thermal insulator for the body

• 服装的蒸发换热热阻 ( 干燥服装 ) ：

Ie,cl = Icl / LR = Icl / 16.5 (kPa·m2/W)

• 服装被汗湿润后热阻会下降，显热换热加强，又增加了潜热换热，故总传热系数增加。

Evaporative heat loss, E 人体蒸发散热量 (a) Respired Vapour Loss, Eres (a) Respired Vapour Loss, Eres 呼吸散热散湿量(i) Latent Respiration Heat Loss, Erel 呼吸时的潜热散热量(ii) Convective or Sensible Respiration Heat Loss, Erec

(b) Evaporative Heat Loss from Skin Surface, Esk(b) Evaporative Heat Loss from Skin Surface, Esk

皮肤蒸发散热量(i) Evaporative Heat Loss by Skin Diffusion, Edif 皮肤湿扩散散热量(ii) Heat Loss due to Regulatory Sweating, Ersw 汗液蒸发散热量 E = Eres + Esk = Erel + Erec + Edif + Ersw

• Dry heat exchange, R + C 干热交换

• C= fcl hc (tcl ta )

• R=3.96 10-8 fcl [ (tcl + 273)4 ( ？？ + 273)4 ]}

• mean radiant temperature (tr) is that uniform temp. of an imaginary black enclosure which result in the same heat loss by radiation as the actual enclosure

Mean radiant temperature 平均辐射温度平均辐射温度

The mean radiant temperature should be kept near the The mean radiant temperature should be kept near the air temperature but not more than 3 ℃ below it, air temperature but not more than 3 ℃ below it, otherwise conditions are sensed as “stuffy”otherwise conditions are sensed as “stuffy”

.....AA

.....tAtAt

21

2211r

M-W-C-R-E=0 （ S=0 ）• developed by Prof. P. O. Fanger (Denmark)• Fanger’s comfort equation:

f (M, Icl, V, tr, tdb, Ps) = 0

where M = metabolic rate (met)

Icl = cloth index (clo)

V = air velocity (m/s)

tr = mean radiant temp. (oC)

tdb = dry-bulb temp. (oC)

Ps = water vapour pressure (kPa)

Predication of Thermal Comfort热舒适的预测

Predication of Thermal Comfort热舒适的预测

• Fanger’s equation is complex• but it may be transformed to comfort diagrams• it can also be used to yield three indices:

• predicted mean vote (PMV) 预测平均评价预测平均评价• predicted percentage of dissatisfied (PPD)

预测不满意百分比预测不满意百分比

Predicted Mean Vote scale

- +3 Hot

- +2 Warm

- +1 Slightly warm

- +0 Neutral

- - 1 Slightly cool

- -2 Cool

- -3 Cold

The PMV index is used to quantify the degree of discomfort

Calculation of PMV index

PMV = (0,303e-2,100*M + 0,028)*[58,15*(M-W)-3,05*10-3*[5733-406,7*(M-W)-pa]-24,21*[(M-W)-1]-10-3*M*(5867-pa)-0,0814*M*(34-ta)-3,96*10-8*fcl*[(tcl+273)4 - (teq+273) 4] - fcl*hc,eq*(tcl-teq)]

hc,eq = 2,38*(tcl - teq )0,25 fcl

M [MET)] Icl [CLO]

1,00+0,2*Icl for Icl <0,5 clo

1,05+0,1*Icl for Icl >0,5 clo

PMV = (0,303e-2,100*M + 0,028)*[(M-W)- H - Ec - Cres - Eres]

PMV ?

PMV and PPD

• PMV-index (Predicted Mean Vote) predicts the subjective ratings of the environment in a group of people.

• PPD-index predicts the number of dissatisfied people.

http://www.healthyheating.com/solutions.htm

Predication of Thermal Comfort热舒适预测

•express thermal comfort in a single number by combining 2 or more comfort parameters

• operative temperature, 操作温度 to

• weighted sum of tdb and tr:

cr

dbcrro hh

ththt

• effective temperature, ET 有效温度• 干球温度、湿度、空气流速对人体温暖感或冷感影响

的综合数值，该数值等于产生相同感觉的静止饱和空气的温度

• 请你描述一下 ET=26℃ 的热感觉

Standard effective temperature 标准有效温度• 身穿标准热阻服装的人，在相对湿度为 50% ，空气静

止不动，空气温度等于平均辐射温度的等温环境下，若与他在实际环境和实际服装热阻条件下的感觉相同，则该温度就是上述实际环境的标准有效温度。

Comfort Temperature

1,7 CLO2,5 METRH=50%tco=6oC.

0,8 CLO2,2 METRH=50%tco=18oC.

0,5 CLO1,2 METRH=50%

tco=24,5oC.

What should be measured?

•Parameters to measure are:

- ta Air Temperature

- tr Mean Radiant Temperature

- va Air Velocity

- pa Humidity

Local Thermal Discomfort局部热不舒适

• Draught• 吹风感

• Radiation Asymmetry• 不均匀辐射

• Vertical Air Temperature Differences.

• 垂直温差

• Floor temperature• 地板温度

Vertical Air Temperature Difference

• Vertical Air Temperature Difference is the difference between Air Temperature at ankle and neck level.

Vertical Air Temperature Difference

Dis

satis

fied

25 oC

19 oC

Floor Temperature

• Acceptable floor temperatures ranging from 19 to 29 oC.

• The graph is made on the assumption that people wear “normal indoor footwear”.

Floor Temperature

Dis

satis

fied

Workplace Measurements

- 1.1 m

- 0.1 m

- 0.6 m

- 0.1 m

- 1.1 m

- 1.7 m

• Measurements of Vertical Temp. difference and Draught at ankle and neck.• Other measurements should be performed at persons centre of gravity.