Heating and cooling degree day prediction within the London urban heat island area

Abstract

This paper describes the London Site Specific Air Temperature prediction model, which comprises of a suite of artificial neural network (ANN) models to predict site-specific hourly air temperature within the Greater London Area (GLA). The model was developed using a back-propagation ANN model based on hourly air temperature measurements at 77 fixed temperature stations (FTS) and hourly meteorological data (off-site variables) from Heathrow; it also includes six on-site variables calculated for each FTS. The temporal and spatial validity of the model was tested using data measured 7 years later from the original dataset, which include new FTS locations. It was found that site-specific hourly air temperature prediction is within accepted range and improves considerably for average daily and monthly values. Therefore, the model can be used with confidence to predict daily and seasonal variations of air temperature within the GLA and in particular for the calculation of monthly and annual heating degree days (HDD) and cooling degree hours (CDH). It was found that as expected HDD increase and CDH decrease with distance from the urban heat island centre point; however, all variations cannot be explained with distance and six key on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass have been identified to explain the remaining variation.

Practical applications: Research studies have confirmed the extent of Urban Heat Island (UHI) within many cities in Europe. Studies have also confirmed the impact of the UHI on energy demand by buildings. There is therefore need to consider this in the design of building by using site-specific external temperatures in the energy calculations for urban buildings. This paper describes the development of a model, which can generate site-specific air temperature in a large number of locations in London. The model's predictions can be used for the calculation of HDD and CDH for any base temperature across London using any Heathrow weather file for a specific year, design years or future climate years; such values can be used for the calculation of site specific building heating and cooling loads.

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