There is non-linear nature of electricity load and temperature. Many researcher use piecewise linear specifications is used to find the different temperature ranges. For example- 9 to 15 degree Celcius for heating degree during summer, however 9-20 degree for winter season. Similar knots can get for cooling degree as well. I will be very happy if can get some easy way to understand it.
Dear Kamal,
Climate change is a factor that affects electricity consumption behavior and also influences for changes in load of the network. One parameter is temperature and which is the most important factor because of the use of heating and cooling devices in loads.
This effect of air temperature can understand by identifying the fluctuations in electricity consumption with the help of temperature coefficient and Weighted-population index takes places. In this situations, network load dependency from air temperature changes could be analyzed.
Hope this would give a brief idea.
All the best Kamal sir
The relationship between dry bulb temperature and building heating and cooling demand is linear unless you're operating near the heating and cooling degree day base temperatures for a specific building. In this zone, the acclimatisation may impact utility utilisation rate.Factors which are not linear are
Factors which are not linear are acclimatisation, latent loads and operational loads driven by seasonal occupant behavior (hot water usage rates etc).
Here's how to understand the use of heating-degree days (HDD):
When the weather is very warm, energy/electricity consumers do not need heating. So below a cut-off temperature (usually around 18 degrees C), one would simply say that consumption of energy for heating purposes is insignificant, or rather, we count 0 HDD.
When the temperature falls below the cut-off temperature, consumers start needing heating. So if the cut-off temperature is 18 degrees and the actual average temperature one day is 17 degrees, we count 1 HDD, since the consumers would have to heat for 1 degree C to reach their cut-off temperature. If the actual temperature one day is 16 degrees C, we count 2 HDDs, because consumers would have to heat "twice as much" (approximately) to reach the comfortable temperature of 18 degrees C.
It turns out that this measure (HDD) correlates very well with energy consumption. And also, it is possible to accumulate HDDs over days: one day with 16 degC (considering a cut-off of 18 degC) has approximately the same effect on consumption as two days with 17 degC. So we can aggregate this measure across days, which we could not do with raw temperatures in degC.
And for Cooling-Degree-Days (CDD) there is an analogous explanation, although cooling and heating affect the consumption differently, so you must treat them separately.
Given average temperature avgT and a cut-off temperature cutT, heating degree days would be calculated: HDD = min(0, cutT - avgT).
In some cases, the average temperature avgT is calculated as the daily maximum plus the daily minimum divided by two, (Tmax+Tmin)/2, but essentially this functions as an approximation to the average temperature.
Hope that explanation makes sense...
Dear Kamal,
Researches above provided a very informative and well structured answer to your question. If you are interested please take a look at a part of my analysis (attached fig2) which I've conducted for the capital city of Poland. I have considered hourly: load , temperature and irradiation (since I was investigating those relations from the perspective of photovoltaics) all covering period 2010-2016.
Please note that Poland lays in norther hemisphere (mostly temperate climate) therefore, we have usually heating degree days from November to April and cooling degree days from June to August. Currently we observe a change in load/temperature relation - the highest demand is not only observed when the temperatures are low but also when they are significantly greater than 20 degrees (increase in installed capacity in air conditioning) - to see those changes take a look at Rys. 2 (Paper.pdf) in the attached paper (unfortunately it is in polish but figures are self explanatory.
I hope that helps.
Dear Kamal,
Also to complete information about this subject i suggest to you links, attach publications in topics.
- Power Quality in Power Systems and Electrical Machines
https://books.google.dz/books?isbn=0080559174
- 1999 European Wind Energy Conference: Wind Energy for the Next ...
https://books.google.dz/books?isbn=1134273584
Best regards
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I am really happy to read all the answers and it really help me for my work. Thank you so much once again.
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