04 - clima
TRANSCRIPT
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Clima Characterization
Characterization of clima and clima types
Variation of temperature and humidity
Data sources for Portugal and models
ro ect con t ons an egree‐ aysInformation included in RCCTE including
solar radiation energy incident in surfaces
Clima Types
• The clima may be classified in five main types:
– Cold weather with minimum temperatures below ‐15oC down to ‐40oC with large relative humidity.
– Tempered with minimum temperatures down to ‐15oC and
higher temperatures
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Climatization Needs• The requirements depend on the clima to achieve
conditions within the thermal comfort zone
Hot and Humid
Clima ‐ Cooling and
dehumidification
Hot and Dry Clima
Desumidification
(Cooling/Heating)
Moderate clima
Heating
vapora ve
oo ng(humidification
with water)
Dry Clima and moderate
(Is not usually observed)
Humidification with vapour
or with water and heating
Cold Clima Heating
and humidification
Climatisation Requirements
• In the occupied space in general there are humidity sources while sensible heat may be added or taken out.
• Therefore the air inlet has to be with lower humidity ω and higher or lower temperature to allow for the evolution in the room.
E
S
Sala (S)IF Q L Ar In‐suflado
Ar Novo
RM
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Weather Stations• In Portugal there are values of temperature, humidity, wind
intensity, precipitation and pressure in 112 weather stations.
• Information from Instituto Metereologia.
• Radiation only available from 8 stations ?
Temperature variation• The temperature variation along the year and the day are
considered on dynamic model simulations (used in RSECE).
• e programs ave mo e s o pro uce e empera ure or they can be imported from climate models (e.g. Meteonorm).
• A very simple model consists of a sinusoidal fit along time
based on the minimum/maximum and when they occur (e.g.*)
106cos22)( hT T T hT Max Ar 6
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Statistical
Information• IM defined averaged values since 1971 in publications:
– Temperaturas exteriores de projecto e números de graus‐dias (1ªEd. 89; 2ª Ed. 95)
– On the internet site there is information since 2003 http://www.meteo.pt/pt/
• The values in the written publications are for: – Maximum and minimum temperature for given probabilities of being
exceeded duringa given season:(summer – 4 month)(winter – 8 month)
– Temperature amplitude in the hotter days (10.5oC in Lisbon)
Probability 1 % 2.5 % 5 % 10 %Minimum temperature (oC) 4.3 5.5 6.4 7.6Maximum temperature (oC) 32.9 31.2 29.7 27.9Wet bulb T when max. TAir (
oC) 20.8 20.3 19.9 19.5Maximum wet bulb temp. (oC) 21.9 21.2 20.6 19.9
– GD is the sum of the temperature deviation from a reference temperature T
b during either winter or summer, accounting only for
values lower or higher, respectively:
– Tb from 12 to 20oC (winter)
– Tb from 16 to 30oC (summer)
final
initial
d
d d h
hb T T MaxGD24
1 24
0;
Example for winter
Temperature extremesMaps of minimum and maximum temperautre that are exceeded with 1% probability . For all weather stations the average and absolute
temperature
extremes
are given:
Example for Lisbon (IM) Maps taken from Rogério Duarte
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Temperature increase
• In Portugal the average growth onaverage temperature is 0.0074oC/year
• IM produces maps of deviations from the 30 years average (Example for the maximum value ~3oC)
• A study indicated in ASHRAE comparing the values of 1274 weatherstations from 1977‐1986 with 1997‐2006 leads to average values:
• The 99.6% annual dry‐bulb temperature increased 1.52°C
• The 0.4% annual dry‐bulb increased 0.79°C• °
IM, 2010
.• Heating‐degree days (base 18.3°C) decreased
by 237°C‐days• Cooling degree‐days (base 10°C) increased by
136°C‐daysThis study however does not correct for the urban
effect that increased values in some stations.
Daily changes in humidity• Although temperature has significatively large variations during
day, absolute humidity has small variations but it may condense in winter.
• For Lisbon typical values are 64 g/kg in August and 81 g/kg in January.
10
20
30
p e r a t u r a ( º C )
i i
0
0 6 12 18 24
Horas
T e m
i i Abril Maio JunhoJul ho Agost o SetembroOutubro Novembro Dezembro
Hora da temperatura mínima e máxima assumidas 2/14h
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Cloud formation and wind• While direct solar radiation is easily calculated, wind, cloud
formation and precipitation are much harder to predict.
•
important for nebulosity and wind speed and direction. These may depend on local orography and other conditions.
– In general wind velocity increases with height.
– In urban environment the wind intensity is smaller and channelling effects can be important as well as in valleys in nature.
– Near sea wind is inland during day and in sea direction at night.
– The presence of clouds obstruct solar radiation during day and at night avoids the heat loss from the earth to the space.
• Statistical information has to be considered with typical values.
Regulations• In RSECE and in HVAC project it is usual to consider a clima model.
• In RCCTE to calculate energy consumption (but not power) the country is divided in three levels for summer/winter. (Exceptions in some zones depending on distance from coast and altitude)
Azores and Madeira are V1 and winter depend on the
height (Z) above sea level.
Região Açores Madeira
I1 Z
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Mainland PortugalCombined
climate
regions
for winter and summer Wind
speed
and
intensity
at 80m from ground level
From Quercus From INETI
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Information included and use
• For winter the objective is to calculate the total energy needed to heat the spaces so the Degree‐Day (GD) is used based on 20oC
demand on energy consumption (correction for both regulations)
• For summer the maximum temperature and temperature amplitude are used for project and of little use to RCCTE.
• For energy consumption the important information (assuming a regular utilization of the spaces e.g. houses) is the average
during cooling period taken as four month (June to September).
• The summer regions are further divided North and South of the Tagus river (with exceptions to be written down in RCCTE)
Incident solar radiation (kWh/m2 year)In summer the radiation energy is indicated in kWh/m2
for the intensity is
Atenção que indica‐se ser Intensidade da radiação Energia solar média incidente
In winter the intensity is indicated per month and is considered for heat gains.
summer period (June‐Sept. 122 days)
so ar para a estação convenciona e arre ecimento mas é a energia total incidente e ainda por cima quando se apresenta o quadro não tem unidades.
numa superfície vertical orientada
a sul na estação de aquecimento
Gsul (kWh/m2 mês)
Regiões I1 I2 I3
Continente 108 93 90
Açores 70 50 50
Madeira 100 80 80
How to calculate radiation incident in other orientations? (Solar geometry for direct irradiation but also account to diffuse radiation and nebulosity that affects the totals.)