Degree day
Encyclopedia
A degree day is a measure of heat
ing or cooling. Totalized degree days from an appropriate starting date are used to plan the planting of crop
s and management of pest
s and pest control
timing. Weekly or monthly degree-day figures may also be used within an energy monitoring and targeting
scheme to monitor the heating and cooling costs of climate controlled buildings, while annual figures can be used for estimating future costs.
A degree day is computed as the integral
of a function of time
that generally varies with temperature
. The function is truncated to upper and lower limits that vary by organism, or to limits that are appropriate for climate control. The function can be estimated or measured by one of the following methods, in each case by reference to a chosen base temperature:
A zero degree-day in energy monitoring and targeting
is when either heating or cooling consumption is at a minimum, which is useful with power utility companies in predicting seasonal low points in energy demand.
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
ing or cooling. Totalized degree days from an appropriate starting date are used to plan the planting of crop
Crop (agriculture)
A crop is a non-animal species or variety that is grown to be harvested as food, livestock fodder, fuel or for any other economic purpose. Major world crops include maize , wheat, rice, soybeans, hay, potatoes and cotton. While the term "crop" most commonly refers to plants, it can also include...
s and management of pest
Pest (animal)
A pest is an animal which is detrimental to humans or human concerns. It is a loosely defined term, often overlapping with the related terms vermin, weeds, parasites and pathogens...
s and pest control
Pest control
Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy.-History:...
timing. Weekly or monthly degree-day figures may also be used within an energy monitoring and targeting
Energy monitoring and targeting
Energy monitoring and targeting is an energy efficiency technique based on the standard management axiom stating that “you cannot manage what you cannot measure”...
scheme to monitor the heating and cooling costs of climate controlled buildings, while annual figures can be used for estimating future costs.
A degree day is computed as the integral
Integral
Integration is an important concept in mathematics and, together with its inverse, differentiation, is one of the two main operations in calculus...
of a function of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
that generally varies with temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
. The function is truncated to upper and lower limits that vary by organism, or to limits that are appropriate for climate control. The function can be estimated or measured by one of the following methods, in each case by reference to a chosen base temperature:
- frequent measurements and continuously integrating the temperature deficit or excess;
- Treating each day's temperature profile as a sine waveSine waveThe sine wave or sinusoid is a mathematical function that describes a smooth repetitive oscillation. It occurs often in pure mathematics, as well as physics, signal processing, electrical engineering and many other fields...
with amplitudeAmplitudeAmplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
equal to the day's temperature variation, measured from max and min, and totalling the daily results; - As above, but calculating the daily difference between mean temperature and base temperature;
- As previous, but with modified formulae on days when the max and min straddle the base temperature.
A zero degree-day in energy monitoring and targeting
Energy monitoring and targeting
Energy monitoring and targeting is an energy efficiency technique based on the standard management axiom stating that “you cannot manage what you cannot measure”...
is when either heating or cooling consumption is at a minimum, which is useful with power utility companies in predicting seasonal low points in energy demand.
External links
- Free heating and cooling degree days for locations worldwide
- Free degree day downloads for 77 UK weather stations and various building base temperatures
- How to use degree-day data for energy management
- Information relating to plant and pest growth
- Inaccuracies in degree-day-based energy calculations, and how to reduce them