Understanding And Modelling Thermal Energy Demand And Emissions In Urban Environments

PhD Thesis


Cowan, D (2017). Understanding And Modelling Thermal Energy Demand And Emissions In Urban Environments. PhD Thesis London South Bank University School of Built Environment and Architecture
AuthorsCowan, D
TypePhD Thesis
Abstract

Refrigeration, air conditioning and heat pump (RACHP) systems currently account for nearly
20% of UK grid electricity use and over 7% of all UK greenhouse gas emissions. This research
project has investigated the sources and levels of emissions from RACHP systems and how the
cooling (and heating) energy and emissions from buildings might be reduced by optimizing the
building’s design, construction and operation.
Analysis of data from site surveys and maintenance logs confirmed that leakage of refrigerant
can be a significant contributor to total RACHP emissions. TEWI (total equivalent warming
impact) analyses showed that for RACHP systems with high GWP (global warming potential)
refrigerants and annual leak rates of 10% or more, direct emissions from refrigerant leakage
can exceed the indirect emissions associated with energy use. However, for heat pump and air
conditioning systems, with typical leak rates of below 3%, using low GWP refrigerants (GWP =
500 or less), the direct emissions do not make a significant contribution to building emissions.
A new dynamic energy balance model and Excel based tool were developed to help improve
the understanding of building energy use and emissions. The tool can be used to predict the
sensitivity to different building design concepts, features and operation and the parameters of
the installed RACHP plant. Results for an office building suggest that the building fabric (with
the exception of the glazing) is not necessarily a key factor influencing the total energy use and
emissions. However, relatively simple measures to reduce electricity use and to reduce solar
gain could each reduce building emissions by 10% or more. Results for a dwelling built to 2006
Building Regulations demonstrated an overheating risk in summer, even with mechanical
ventilation, but adding a 2 kW air conditioning unit could prevent overheating, with lower
energy use and emissions than a similar dwelling incorporating mechanical ventilation.
Climate change simulations for the year 2080 predicted a net increase in energy demand and
emissions of about 5% for the office building (mainly associated with the use of grid
electricity), implying that the grid carbon factor is likely to be a key determinant of future
emissions from such buildings. For dwellings without mechanical ventilation or air
conditioning, internal temperatures might rise as high as 40°C in summer months, but a small
air conditioning unit could maintain temperatures below 25°C with no increase in total energy
use and emissions compared with the present day. For a grid electricity carbon factor
reduction of 80%, total emissions for the simulated office building would fall by about 70% and
for the dwelling by about 50%.

Year2017
PublisherLondon South Bank University
Publication dates
Print01 Feb 2017
Publication process dates
Deposited23 Feb 2018
FunderEngineering and Physical Science Research Council
London Development Agency
UK Institute of Refrigeration
Publisher's version
License
CC BY 4.0
Publisher's version
License
CC BY 4.0
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https://openresearch.lsbu.ac.uk/item/87091

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