Cooling and heating with ground source energy
| Date | 03 October 2012 |
| DOI | https://doi.org/10.1108/20425941211271496 |
| Published date | 03 October 2012 |
| Pages | 282-300 |
| Author | Abdeen Mustafa Omer |
| Subject Matter | Public policy & environmental management,Environmental technology & innovation |
Cooling and heating with ground
source energy
Abdeen Mustafa Omer
Energy Research Institute (ERI), University of Nottingham, Nottingham, UK
Abstract
Purpose – The purpose of this paper is to describe how, in the recent attempts to stimulate alternative
energy sources for heating and cooling of buildings, emphasis has been put on utilisation of the
ambient energy from ground source heat pump systems (GSHPs) and other renewable energy
sources.
Design/methodology/approach – Exploitation of renewable energy sources and particularly
ground heat in buildings can significantly contribute towards reducing dep endency on fossil fuels.
This paper highlights the potential energy saving that could be achieved through use of ground
energy source. It also focuses on the optimisation and improvement of the operation conditions of the
heat cycles and performances of the direct expansion (DX) GSHP.
Findings – It is concluded that the direct expansion of GSHP are extendable to more comprehensive
applications combined with the ground heat exchanger in foundation piles and the seasonal thermal
energy storage from solar thermal collectors.
Originality/value – The paper highlights the energy problem and the possible saving that can be
achieved through the use of the GSHP systems and discusses the principle of the ground source
energy, varieties of GSHPs, and various developments.
Keywords United Kingdom, Energy supply systems, Geothermal power,
Ground source heat pump systems, Direct expansion GSHPs, Ground source,
Development and evaluation of the system
Paper type Research paper
Introduction
Renewable energy sources have one thing in common; they all existed before man
appeared on this planet. Wind, wave, hydro, solar, geothermal, and tidal power are all
forces of nature and are mostly intermittent energy sources, ge othermal is the only
consistent phenomenon. Geothermal renewable energy sources where probably the
first to be fully utilised by man. Early civilisations tapped this heat to cook, fire clay
pottery, create baths and spas, and even heat their homes. Romanvillas had under floo r
heating from natural hot springs over 2,000 years ago.
Shallow geothermal resources (o400 metres depth by governmental definition
in several countries) are omnipresent. Below 15-20 metres depth, everything is
geothermal. Figure 1 show a summary of the soil thermal properties. The temp erature
difference between determine the ground temperature. The ground and the fluid in
the ground heat exchanger drives the heat transfer so it is important to the temp erature
field is governed by terrestrial heat flow and the local g round thermal conductivity
structure (groundwater flow). In some countries, all energy stored in form of he at
beneath the earth surface is per definition perceived as geother mal energy(VDI, 1998).
The same approach is used in North America. The ubiquitous heat content of shallow
resources can be made accessible either by extraction of g roundwater or, more
frequent, by artificial circulation like the borehole heat exchanger (BH E) system
(Knoblich et al., 1993). This means, the heat extraction occurs – in most cases – by pure
conduction; there is no formation fluids required. The most popular BHE heating
system with one of more boreholes typically 50-200 metres deep is a closed circuit, heat
The current issue and full text archive of this journal is available at
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WorldJour nal of Science, Technology
and Sustainable Development
Vol. 9 No. 4, 2012
pp. 282-300
rEmeraldGroup PublishingLimited
2042-5945
DOI 10.1108/20425941211271496
282
WJSTSD
9,4
pump coupled system, ideally suited to supply heat to smaller, de-central objects like
single family or multifamily dwellings (Figure 2). The heat exchangers (mostly double
U-tube plastic pipes in grouted boreholes) work efficiently in nearly all kinds of
geologic media (except in material with low-thermal conductivity like dry sand o r dry
gravel). This means to tap the ground as a shallow heat source comprise:
.groundwater wells (“open” systems);
.BHEs;
High
pressure
switch
Filter drier
Hot
Cold
Heat exchanger Ground loop
system
Liquid flow
control
Earth loop
liquid
Temperature
sensor
Temperature
sensor
Low pressure
switch
Note: Typical BHE length = 100 m
Figure 2.
Typical application
of a borehole heat
exchanger (BHE) heat
pump system in a central
European home
Thermal
conductivity
(W/m K)
Specific heat
(kJ/kgK)
Diffusivity
(m2/s)x10–7
7
6
5
4
2
3
1
0
Thermal conductivity (W/mK),
diffusivity (m2/s)x10–7
Specific heat (kJ/kgK)
2.0
1.5
1.0
0.5
0.0
Laboratory soil
( = 1,771 kg/m3)
Coarse graveled
( = 2,050 kg/m3)
Limestone
( = 2,500 kg/m3)
Granite
( = 2,640 kg/m3)
Figure 1.
Measured thermal
properties for
different soils
283
Ground source
energy
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