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Technological Status of Shallow Geothermal Energy in Europe

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Shallow geothermal systems are usually combined with heat pumps (ground source heat pumps; GSHP). GSHP are widely spread all over Europe, with a long history in the centre (Austria, Germany, Switzerland) and in Sweden, and a subsequent market development in Benelux, France, Finland, Ireland, UK, and the Eastern countries. The use of GSHP in Southern Europe still is in its infancy. Well d esigned, installed and maintained GSHP systems work over many decades without any problems and do not pose any threat to the environment. A number of technical guidelines of engineer's associations and ground-water protection authorities have established a common state of the art. Underground Thermal Energy Storage (UTES) systems also use shallow geothermal technologies. They may or may not comprise heat pumps, and are used for storing heat or cold either in the solid ground (with borehole heat exchangers) or in aquifers. Large installations of the aquifer storage type (ATES) for cooling purposes can be found e.g. in Southern Sweden and in the Benelux countries. The current situation with a dramatic increase of GSHP installations in many countries (e.g. Germany, fig. 9) has changed the established market, as new players with poor experience and poor training now participate in it. A strong quality assurance and accompanying training and certifica-tion programs are urgently needed to prevent negative envi-ronmental impacts and damage in the public image of the whole GSHP sector.
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Proceedings European Geothermal Congress 2007
Unterhaching, Germany, 30 May-1 June 2007
1
Technological Status of Shallow Geothermal Energy in Europe
Walter J. Eugster1 and Burkhard Sanner2
1Polydynamics Engineering, Malojaweg 19, CH-8048 Zurich, Switzerland
wje@polydynamics.ch
2EGEC asbl, Renewable Energy House, Rue d´Arlon 63-65, B-1040 Brussels, Belgium
b.sanner@egec.org
Keywords: Ground source heat pump, borehole heat ex-
changer, shallow geothermal energy, quality assurance
ABSTRACT
Shallow geothermal systems are usually combined with
heat pumps (ground source heat pumps; GSHP). GSHP are
widely spread all over Europe, with a long history in the
centre (Austria, Germany, Switzerland) and in Sweden, and
a subsequent market development in Benelux, France,
Finland, Ireland, UK, and the Eastern countries. The use of
GSHP in Southern Europe still is in its infancy.
Well designed, installed and maintained GSHP systems
work over many decades without any problems and do not
pose any threat to the environment. A number of technical
guidelines of engineer’s associations and ground-water
protection authorities have established a common state of
the art.
Underground Thermal Energy Storage (UTES) systems also
use shallow geothermal technologies. They may or may not
comprise heat pumps, and are used for storing heat or cold
either in the solid ground (with borehole heat exchangers)
or in aquifers. Large installations of the aquifer storage type
(ATES) for cooling purposes can be found e.g. in Southern
Sweden and in the Benelux countries.
The current situation with a dramatic increase of GSHP
installations in many countries (e.g. Germany, fig. 9) has
changed the established market, as new players with poor
experience and poor training now participate in it. A strong
quality assurance and accompanying training and certifica-
tion programs are urgently needed to prevent negative envi-
ronmental impacts and damage in the public image of the
whole GSHP sector.
1. INTRODUCTION
Shallow geothermal systems typically are combined with
heat pumps (ground source heat pumps, GSHP; for other
options see chapter 4). Solid underground or ground-water
serve as heat source or heat sink. Shallow geothermal sys-
tems use typically the heat of the first 400 m of depth of the
solid earth. A list of the largest installations currently built
with BHE in Europe is given at the end of this paper.
Ground-water is tapped with open circuit systems: there is a
borehole needed to pump up the water to the heat pump and
there is a structure needed to return the used water into the
underground (re-injection well or infiltration structure).
The heat of the solid underground is normally used by a
closed circuit pipe system, which is installed horizontally
(horizontal loops, incl. compact systems with trenches,
spirals etc.) or vertically (borehole heat exchangers; BHE).
A third possibility are so-called “geostructures”: the loops
are installed in foundation piles or foundations walls which
are embedded in a water-saturated underground.
The closed loop systems use normally three circuits: heat
source circuit, heat pump circuit and heating circuit (see
figure 1). The first is filled with a water-antifreeze mixture.
Direct expansion with only two circuits may be used with
horizontal loops (figure 2).
heat pump
circulation
pump
1:
Ground circuit
(water, brine)
2:
Refrigerant
circuit
3:
Heating
circuit
horizontal loop
heat pump
circulation
pump
1:
Ground circuit
(water, brine)
2:
Refrigerant
circuit
3:
Heating
circuit
Figure 1: Basic scheme of a “classical” GSHP with wa-
ter/brine circuit, with BHE or horizontal collector; this
system can be reversed for cooling
horizontal loop
heat pump
1:
Ground and
refrigerant circuit
2:
Heating
circuit
Figure 2: Basic scheme of a direct expansion GSHP with
horizontal collector; this system can only be used for
heating
For the vertical BHE, application of heat pipes (using CO2
or propane), which work without circulation pumps, have
found a new interest during the past few years (figure 3).
Heat pipes can only be used for heating (heat extraction
from the ground), however, combined systems with heat
pipes inside classical BHE circuits have been suggested
recently. Vertical systems may also be used as short-term
and/or seasonal underground storage systems
In middle Europe the GSHP systems are mainly used as
heating systems. Cooling (free cooling and active cooling
with the heat pump) is normally only used in larger com-
mercial installations. Of course, in Northern Europe the
Eugster and Sanner
2
heating demand is higher; however, even in Scandinavia we
find commercial installations with high cooling loads. In
Southern Europe the cooling ability of a GHSP is more
important than heating.
heat pump
2:
Refrigerant
circuit
3:
Heating
circuit
1:
Heat Pipe
circuit
heat
exchanger
Figure 3: Basic scheme of a GSHP with heat pipe BHE;
this system can only be used for heating
Regardless of the wide variety of special shapes and sys-
tems, this paper outlines only the most common systems.
Special attention is given to the BHE systems: they cover
the largest market share, but they still can hold a certain risk
regarding environment and ground-water protection - if
built and used without adequate diligence.
2. LEGISLATION
Every GSHP installation needs a license from the relevant
authority for ground-water protection, water management
or mining. Depending on the local laws a building permit is
also sometimes needed. All licences must be applied for in
advance. Closed circuit installations may allow implicit and
simplified proceedings.
Usually the licensing authorities impose special conditions
for the construction and the operation of GSHP. These spe-
cial conditions vary depending on the risk potential of the
installation.
Within the countries with a developed GSHP market (e.g.
Austria, Germany, Sweden, Switzerland) national or re-
gional water management and/or ground-water protection
authorities have published guidelines for the licence pro-
ceedings, as well as for the construction and operation of
GSHP installations. Many authorities provide maps and
web-based GIS-applications with indication of which type
of GSHP is allowed or recommended at which location
(figure 4).
Figure 4: Example of map for BHE licensing from state
of Hessen, Germany; green areas allow for simplified
license for GSHP <30 kW heating output, red areas
show inner water protection zones (no license possible),
all other areas individual decisions (www.hlug.de).
3. GSHP SYSTEMS
The following three GSHP systems are mainly used in
Europe: Ground-water heat pumps, BHE, and horizontal
loops with three circuits. The market shares of these sys-
tems change from country to country even from region to
region.
3.1 Borehole Heat Exchangers (BHE)
BHE (see figure 5) are typically made of two U-shaped
pipes of polyethylene (PE100, or PE-X in high temperature
applications). The complete BHE is usually pre-fabricated
and tested in the factory. The BHE is installed carefully into
the borehole by the drilling contractor. Immediately after
insertion of the BHE into the borehole, the annulus is
grouted diligently and densely through an injection tube
(“tremie pipe”) from to bottom to the top. The grouting has
two purposes; (1) to establish a good and dense contact to
the underground and (2) to prevent any vertical water
movement along the borehole.
In Scandinavian countries the practice in hard, crystalline
rock allows for keeping the borehole open and the annulus
filled with water; however, a sealing to the surface is re-
quired. Single-U-tubes are the standard for Scandinavian
BHE.
Figure 5: Basic scheme of a borehole heat exchanger
installation. System and underground temperatures are
given (www.fws.ch).
The BHE have a typical depth between 80 and 350 m
(changing from country to country). The single tubes have
diameters of 32 or 40mm (25mm with very short BHE’s).
On the technology front, the improvements described at the
last EGC (Sanner et al., 2003) took on.
- Thermally enhanced grouting now is available in dif-
ferent brands and is used routinely.
- Thermal Response Tests are a standard practice in the
design of larger installations, and test rigs are available
for use in most European countries by now.
- While direct expansion (e.g. with ammonia) in BHE
did not catch on, as already hinted in 2003, the use of
heat pipes as BHE (cf. fig. 3) meanwhile grew out of
the stage of R&D and pilot plants (Kruse & Rüssmann,
2005; Mittermayr, 2005). These systems are commer-
cially built and a good alternative in small to medium
Eugster and Sanner
3
plants with heating demand only, however, they can-
not replace the BHE with water/antifreeze in all appli-
cations.
BHE need a ground-water protection license and sometimes
depending on the local laws a mining license. The used
geothermal heat is free of charge (at least for the time be-
ing). However, licenses carry a fee to be paid to the authori-
ties, which in some regions can be quite substantial and can
be a barrier to GSHP market development.
From the point of view of the ground-water protection au-
thorities, the primary risk potential of a BHE are uncon-
trolled water flows into and along the borehole. In some
countries the heat carrier fluid (antifreeze) is no longer
considered as an important threat. Therefore no BHE are
allowed in ground-water protection areas, in areas with
several ground-water storeys, with confined or heavily min-
eralised ground-water (cf. figure 4).
Ground-water authorities impose usually special conditions
to installers and/or house owners, e.g.:
Correct dimensioning (e.g. after VDI 4640, SIA, …),
adequate BHE, piping and joint material,
adequate drilling equipment,
correct drilling mud disposal,
minimal quality of grouting,
immediate communication of special incidents,
final testing and commissioning of the BHE’s,
leakage prevention, and
precepts for final shut-down of BHE’s
If correctly dimensioned and built, the risk potential during
operation is minimal.
3.2 Horizontal Loops
Horizontal loops (see figure 6) are installed at a depth be-
tween 1.0 and 1.5m. The tubes are usually made of Poly-
ethylene (PE100) and have a size of up to 25 mm. From the
point of view of ground-water protection these systems do
not pose a threat to ground-water if installed above the
maximum water level.
Authorities impose usually special conditions to installers
and/or house owners, e.g.:
Correct dimensioning (e.g. after VDI 4640, …),
adequate piping and joint material,
final testing and commissioning,
leakage prevention, and
precepts for final shut-down.
Figure 6: Basic scheme of a GSHP installation with
horizontal loops.
If correctly dimensioned and built, the risk potential of such
a installation during operation is minimal.
Horizontal loops need a ground-water protection licence.
The used geothermal heat is free of charge.
3.3 Ground-Water Heat Pumps
The heat source circuit of a ground-water heat pump instal-
lation is open: The production well reaches down to the
ground-water layer; the water return structure (return well
or infiltration structure) forms also a direct link to the
ground-water.
From the point of view of ground-water protection, this
system has the highest risk of all GSHP types. Harmful
substances can pollute the ground-water layer. Authorities
usually impose strong conditions to the construction and the
operation of ground-water heat pumps.
A hydrogeological preliminary study is always neces-
sary, including:
- natural thermal condition of the ground-water,
- thermal as-is state of the ground-water,
- estimation of thermal potential,
- hydrograph of yearly ground-water table and
temperature sequence,
- ground-water chemistry,
- estimated impact of ground-water cooling,
- impact on other (present and future) utilisations
- evaluation of conformity with actual laws.
Only professionally built and maintained installations
are allowed.
Strong requirements for the wells or infiltration struc-
tures (see figure 7).
The used water has normally to be completely returned
to the ground-water layer.
No direct discharging of any waste or rain water into
the ground-water.
No well on roads, gateways or parking areas.
Accessibility for well control
Any chemical regeneration of old wells needs an
ground-water protection allowance.
Dense cover
min. Ø60cm
Bank
min. 30cm Ground line
Carefully placed cover sealing:
Backfilling with (nearly) unpermeable
excavation material (>1m) or
clayey material (50cm)
Excavation
Rubble 30 80 cm
(Possibly) basement
Underground with
infiltration capacity
Variable
(depending on
the infiltration
Capacity)
min. 100cm
Variable
(depending on the
infiltration capacity)
Figure 7: Basic scheme of a infiltration structure (BAFU
2007).
If correctly dimensioned and built, the risk potential during
operation is minimal. Ground-water heat pumps need a
ground-water protection licence as well as a water man-
agement licence. The used ground-water heat is chargeable.
4. UNDERGROUND THERMAL ENERGY STORAGE
In Underground Thermal Energy Storage (UTES) systems
the temperature of a body of groundwater or solid soil/rock
Eugster and Sanner
4
is changed, e.g. by injection cold groundwater in wintertime
for cooling in summer. This technology only works with
large installations, where the volume of the warm or cold
part of the underground is large compared to the envelope.
Since the first commercial seasonal cold storage application
for a printing company in the Netherlands in 1987 (Kooi-
man & van Loon, 1991), the market has developed rapidly
in particular in The Netherlands and the Northern part of
Belgium (Flanders), and in Scandinavia.
Heat storage in the underground is done up to relatively
high temperatures. Experiments in the 1980s in France and
USA with temperatures >100 °C have not been successful,
and the high temperature aquifer storage system at Utrecht
University in the Netherlands (operational for up to 90 °C
since 1991) was abandoned after several years, when the
combined heat and power plant used for supplying the heat
in summertime was changed. However, heat storage with
temperatures up to 70 °C in the shallow geothermal realm
could be demonstrated in several installations successfully,
using both BHE or aquifer storage technologies (fig. 8.). A
very interesting combination of a shallow (ca. 60 m) aquifer
cold storage system with a deeper (ca. 300 m) aquifer heat
storage system is in operation since 1999 for the German
Parliament in Berlin (Sanner et al., 2005).
A study within an IEA-project (Sanner, 1999) had shown
that technical problems related with higher temperatures in
UTES systems may be overcome. One main issue still are
the changes in water chemistry with drastically changing
temperatures in aquifer storage systems, resulting in clog-
ging, scaling, corrosion and leaching. It is possible to de-
sign and build reliable High Temperature UTES plants
today, but caution is necessary when working with ground-
water. The investigation of promising system concepts re-
vealed a number of opportunities to make use of UTES for
saving energy and reducing emissions. For more informa-
tion on UTES, see http://iea-eces.org .
Figure 8: Basic methods for Underground Thermal
Energy Storage (UTES)
5. EXPERIENCE, DESIGN
Since the early 1980s GSHP installations have been moni-
tored and studied (e.g. Sanner, 1987; Eugster, 1991). The
first design tools that actually could be used for simple
calculations have been developed in Sweden (Claesson &
Eskilson, 1988); other computer methods (like numerical
model with FD-method, e.g. Brehm, 1989) could at that
time only be used for research purposes. Originally only
empiric values were known, the omnipresent rules of thumb
for BHE in the 1980s were:
- 55 W/m in Switzerland, cf. the first issue of guideline
T1 (AWP, 1996)
- 50-80 W/m in Germany (Sanner, 1992); even the val-
ues given in the tables of the current version of VDI
4640 are based on the empirical values, and will be re-
placed by values determined by calculation in the revi-
sion which will be published soon.
Meanwhile the easy design tools have been optimised and
adapted: A program used frequently us the Earth Energy
Designer V2.0, published in 2000 (Hellström et al., 1997;
EED, 2000).
Some newer design tools, based on the same g-function
idea (Eskilson, 1986) as in EED, were developed in Europe.
Other design tools have their origin in the USA and Can-
ada. Especially the US tools were used often in GB. An-
other trend is to combine building load calculation / heat
pump / underground design into integrated packages
(Koenigsdoerff & Sedlak, 2006), however, with the under-
ground design part somewhat limited.
The publication of VDI guideline 4640, part 1 and 2 in
German and English represented until today a broad de-
scription of the central European state of the art in planning,
dimensioning and constructing the geothermal part of a
GSHP. At the moment, the VDI guideline 4640, sheet 1 and
2, are revised. More guidelines are listed in the references.
Currently a DIN-standard is under development, for BHE
drilling and installation. Also in Switzerland there is a
Swiss standard about BHE and BHE-fields in preparation
(SIA 384/6). The Swiss norm should be published in early
2008. New standards for drilling (incl. geothermal are pre-
pared e.g. in UK (HVCA TR330) and France (NF X 10/999
”Réalisation, suivi et abandon d´ouvrage de captage ou de
surveillance des eaux souterraines”).
Today the dimensioning of BHE and horizontal loops is
more conservative than it was 15 years ago. Also the new
Swiss standard will show the same trend. The old rules of
thumb should definitely no longer be used. A large number
of planners and engineers have to change their way of di-
mensioning. It’s an information challenge as well as a for-
mation challenge.
The new lower design values are based on a longer and
broader experience. They reflect also the actual trend to-
wards a higher density of GSHP installations in the central
European countries.
5. CURRENT MARKET AND QUALITY SITUATION
During the pas few years the GSHP market has shown a
dramatic increase (e.g. Switzerland: around 20% per year
over 5 years, Germany: more than 100% in 2006; cf.fig. 9).
Beside the heat pump and the pipe manufacturer the estab-
lished experienced players of the GSHP branch can no
longer control this situation by its own means. The queue
time for a new borehole for example is since 2005 around
half a year. Existing companies grow very fast. New play-
ers (planner, engineers, installer, driller) push on the mar-
ket. Many of these new players (new companies, grown
existing companies) only have a very poor experience in the
GSHP techniques; and some do not have any appropriate
experience. This fact makes the GSHP situation very criti-
cal and even dangerous.
The share of qualitatively poor work increases:
planners without appropriate training or experience,
installers without experience,
new drilling teams without appropriate training or
experience.
Good quality work starts with a correct plan-
ning/dimensioning of the installation. The selection of
material and equipment is very important; and last but not
least the construction itself and the commissioning of the
complete installation.
Borehole Storage (BTES)
Aquifer Storage (ATES)
Eugster and Sanner
5
1792 2889 3720 3945 4744 6653 6799 7349 9249
13250
28605
0
5000
10000
15000
20000
25000
30000
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Number of units
Water
Ground
after values from
BWP, Munich
Figure 9: Annual number of new ground source heat
pump units in Germany since 1996 (after data from
BWP 2007).
Small and large installations need in principle the same
proceeding. With large plants the planning work is more
intensely. The final layout of BHE is often made after a first
test drilling and additional studies and tests (thermal re-
sponse test, temperature logs, testing of cuttings).
Mistakes may happen in every part of the work. Mistakes in
planning may yield to a failure of the whole GSHP installa-
tion. Bad drilling work may also cause a failure of the BHE
Unprofessional drilling work may pose a dangerous threat
to the environment and may cause large damages in the
neighbourhood of the borehole (artesian ground-water, gas
blows, ground liquefaction).
Quality assurance is urgently necessary in the GSHP
branch. Some actions are already implemented: There is a
quality label for heat pumps, realised first in Germany,
Austria and Switzerland. This label will be adopted by the
European Heat Pump Association (EHPA). There are train-
ing courses for planners and installers in different countries
(e.g. Austria, Switzerland).
A quality label for BHE-drilling companies exists in Swit-
zerland since 2001 (see figure 10). In Germany, BHE drill-
ing companies are invited to acquire a technical certifica-
tion (e.g. DVGW W120 G1, G2). A quality label like the
Swiss one exists since 2006. Also the large association of
the construction sector in Germany, ZDB, started an own
quality label in the frame of the RAL-labels; it will be con-
trolled by the “Gütegemeinschaft Geothermische Anlagen”,
founded in Dec. 2006. In Austria a quality label for BHE
drilling companies will be launched soon.
Figure 10: The Swiss quality Label for BHE drilling
companies.
6. EXAMPLE: QUALITY ASSURANCE OF BHE
Recommended features of a quality assurance shall be
shown at the example of a small BHE installation. These
actions base on the yet unpublished new SIA and VDI pre-
scriptions:
Exploratory enquiry for a BHE licence at the ground-
water protection authority (map, GIS, e-mail, tele-
phone call),
Selection of an appropriate heat pump on the basis of a
calculated heat demand, dimensioning of the BHE ac-
cording to VDI, SIA or similar technical prescription,.
Apply for a BHE and drilling licence,
Apply for a building licence (according to local laws).
Order a specialised drilling company. Quality features:
- Drilling rig for rotary drilling or down hole ham-
mer/airlift drilling,
- Compressor (if applicable),
- Preventer with different dense joints (figure 6),
- Dense water/mud management,
- Appropriate cutting transport hose,
- Safe pneumatic hose,
- Injection equipment (pump, mixer, material),
- Material to handle incidents (gas, artesian water),
- Barrier and signalisation material,
- Trained drilling staff who knows all immediate
measures in case of incidents,
- Drilling staff knows the limits of the used drilling
method
Figure 11: Drilling equipment with preventer and dense
water/mud management
Figure 12: drain off the cuttings into a hutch using a
safe transportation hose
On site work (drilling company):
- Report start of drilling work to author-
ity/geologist,
Germany
Eugster and Sanner
6
- Indication of the exact drilling points through the
client,
- Drilling work according to the state of the art:
§ e.g. pneumatic down hole hammer / airlift,
§ casing through unconsolidated layers down
into the solid rock (1-2m),
§ drain off the cuttings into a hutch (figure 7),
§ write the drilling report,
§ report critical incidents (gas, artesian water,
pollution, damages),
§ In case of incidents: perform correct immedi-
ate measures to prevent damages; call for ex-
perts to save the bore hole/BHE,
§ Correct disposal of the drilling mud,
§ Remove drill poles at final depth.
- Check BHE for damages,
- Affix an injection tube at the bottom of the BHE
or prepare the injection rods,
- Prepare the prefabricated and factory-tested BHE
on a decoiler with a hydraulic brake (figure 8),
- Install the BHE slowly and carefully into the bore
hole Pay attention to a pressure balance in-
side/outside the BHE,
- Immediate backfilling of the borehole from the
bottom to the top of the hole using the injection
tube or the injection rods. Use only approved ma-
terial in an approved mixture. Take care, that the
BHE’s are filled with water and sealed densely.
- Remove the borehole casing,
- Perform a flow test,
- Perform pressure testing according to DIN EN
805. Commissioning of the BHE to the client
with the test logs,
- Mark, seal and protect the BHE against any dam-
ages (see figures 9 and 10),
- Hand out the drilling report to the authorities and
the client.
Final work (installer)
- Connect the BHE’s to the heat source circuit and
the heat pump,
- Installation and commissioning of the heat pump
- Final testing of the GSHP installation,
- Hand out a complete documentation of the GSHP
installation to the client.
Warranty according to the technical and/or legal pre-
scriptions.
7. EUROPEAN NETWORKS
There has been an technical network in middle Europe
called D-A-CH for the 3 countries Germany (D) Austria
(A) Switzerland (CH). The heat pump part of the network
was integrated in the European Heat Pump Association
(EHPA). The drilling part (quality label) is still remaining
in D-A-CH for the moment. An open question is, if there
will be once an European quality label for BHE drilling
companies.
EHPA forms a technical and marketing network for heat
pump manufacturer in Europe. Many national heat pump
associations exist already.
From the geothermal point of view there exist many na-
tional geothermal organisations (e.g. GtV, SVG). These
organisations provide information and technical support.
On the European level there is the European Geothermal
Energy Council (EGEC), which mainly acts an information
provider.
Figure 13: Preparing the BHE on a decoiler with
hydraulic brake
Figure 14: Sealing the BHE’s
Figure 15: Mark and protect the BHE against damages.
ACKNOWLEDGEMENT
The Swiss quality label for BHE drilling companies was
launched by the Fördergemeinschaft Wärmepumpen
Schweiz (FWS) (www.fws.ch) and is partly financed by
SwissEnergy, a programme of the Swiss Federal Office of
Energy.
The German quality label for BHE drilling companies is
launched by an number of technical organisations of the
GSHP branch (BWP, GtV, FIGAWA, DVGW).
Eugster and Sanner
7
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Sanner, B.: Research on ground-coupled systems with ver-
tical heat exchangers. Proc. WS on GSHP, Albany, Re-
port IEA-HPC WR-2, 113-117, 1987
Sanner, B.: Erdgekoppelte Wärmepumpen, Geschichte,
Systeme, Auslegung, Installation. IZW-Bericht 2/92, 1-
328, 1992
Sanner, B. (ed.): High Temperature Underground Thermal
Energy Storage, State-of-the-art and Prospects. iesse-
ner Geologische Schriften 67, 1-158, 1999
Sanner, B., Karytsas, C., Mendrinos, D. and Rybach, L.:
Current status of ground source heat pumps and un-
derground thermal energy storage in Europe. Geo-
thermics 32, 579-588, 2003
Sanner, B., Kabus, F., Seibt, P. and Bartels, J.: Under-
ground Thermal Energy Storage for the German Par-
liament in Berlin, system concept and operational ex-
periences. Proc. WGC 2005 Antalya, paper #1438, 1-8,
2005
Guidelines:
AWP: Merkblatt T1: Wärmepumpen-Heizungsanlagen mit
Erdwärmesonden. Arbeitsgemeinschaft Wärmepum-
pen (AWP), 1991/1996. Download: www.fws.ch
BAFU: Wärmenutzung aus Boden und Untergrund. Bun-
desamt für Umwelt, Bern, work in progress; publicati-
on planned in 2007/2008, in German and French.
Normbrunn-97: Energibrunnsnorm. Geotec Borrentreprenö-
rerna, 1997. www.geotec.se
ÖWAV RB 207: Anlagen zur Gewinnung von Erdwärme
(AGE). ÖWAV, 1993. www.oewav.at/
SIA D0136: Grundlagen zur Nutzung der untiefen Erdwär-
me für Heizsysteme. SIA/BfE, 1-142, 1996
VDI 4640: Thermal Use of the Underground,
Part 1: Fundamentals, Approvals, Environmental As-
pects, Beuth Verlag Berlin, 2000, revision in progress
Part 2: Ground Source Heat Pump Systems, Beuth
Verlag, Berlin, 2001, revision in progress.
Information on GSHP and quality improvement, e.g.:
www.egec.org
www.geothermie.ch
www.geothermie.de
www.ehpa.org
www.fws.ch
www.waermepumpe-bwp.de
Eugster and Sanner
8
Country City / project name No. BHE depth BHE total BHE length
NO Loerenskog, SiA hospital * ca. 300 150 m ca. 45’000 m
NO Oslo, Nydalen district 180 200 m 36’000 m
SE Lund, IKDC 153 230 m 35'190 m
SE Stockholm, Vällingby Centr.* 133 200 m 26’600m
SE Kista, Kista Galleria * 125 200 m 25’000 m
TR Istanbul, Metro market 168 107 m 18’000 m
DE Golm near Potsdam, MPI 160 100 m 16’000 m
SE Stockholm, Blackeberg area 90 150 m 13’500 m
SE Örebro, Musikhögskolan 60 200 m 12’000 m
DE Langen, DFS 154 70 m 10’780 m
CH Zürich, Grand Hotel Dolder 70 150 m 10’500 m
BHE: Borehole Heat Exchanger * under construction
Appendix: Very large European BHE plants with more than 10 km drilling, status end of 2006 (own data and additional
information provided by Göran Hellström and Tunc Korun). The authors ask to notify if large or even larger - installa-
tions of these type exist or are built elsewhere in Europe.
There are also very large installations using groundwater wells (e.g. for the new Oslo airport at Gardemoen in Norway);
with these plants normally the boundaries between pure GHSP and UTES are vanishing.
... The storage of heat or cold artificially changes the stored temperature through the UTES system. On the other hand, the Heat pump system is the dominant figure in applying shallow geothermal energy (Eugster & Sanner, 2007;Sanner et al., 2003). ...
... Besides, the climate has become a matter of factors. Arid weather is wanted conditions; otherwise, the heat pump has to perform as a chiller, or supplementary de-humidification should be applied to cool (Eugster & Sanner, 2007;Öngen & Ergüler, 2021). ...
... Furthermore, an open system is unsuitable for smaller installations, and a more extensive installation is fitted with an open system. The most powerful open heat-up system supplied ca. 10 MW has been operated in Louisville, Kentucky, USA, to heat and cold hotels and offices (Eugster & Sanner, 2007). ...
Chapter
Full-text available
Energy is a vital need for a country. Therefore, it is essential for countries to be independent in terms of energy. One of the most appropriate ways to do this is to increase the use of renewable energy. However, there are some barriers to this process, such as high costs. Shallow geothermal systems are also energy types that will reduce the energy dependence of countries in this process. Nevertheless, the negative aspects of renewable energy projects also apply to shallow geothermal systems. In parallel, in this study, it is aimed to determine the issues that are important for increasing shallow geothermal energy investments. In this framework, balanced scorecard-based criteria were analyzed with the DEMATEL method. As a result, it has been determined that the issues related to research and development have the most importance in this process. Therefore, in order to develop these systems, it would be appropriate for countries to primarily conduct research on new technologies.
... The thermal conductivity of unsaturated geomaterials plays a fundamental role in a broad range of engineering, geophysical and geoenvironmental applications such as (a) the storage and recovery of heat from shallow geothermal reservoirs [1][2][3][4]; (b) the thermal performance of bentonitic clay used for the storage of highly radioactive nuclear waste [5][6][7]; (c) the indoor thermal comfort inside earth dwellings [8,9]; (d) management of crops and cultivations in agricultural applications [10,11]. ...
Article
Full-text available
This paper proposes a simple thermal conductivity model for geomaterials accounting for the combined effect of both degrees of saturation and dry density. The model only requires the determination of the thermal conductivity under dry conditions (i.e., at a degree of saturation equal to zero) and as little as two additional measurements of thermal conductivity performed at different levels of degree of saturation and dry density. The model is a function of only two fitting parameters, namely the moisture factor mf and the density factor md. Despite its simplicity, the model can correctly predict the thermal conductivity of geomaterials and this has been validated against five sets of experimental data obtained on a very broad range of materials ranging from fine (e.g., bentonite) to coarser soils (e.g., a mix of gravel, coarse sand and silt) tested at different levels of degree of saturation and dry density. The paper also shows that the model can be applied to different engineering contexts such as (a) the thermal behaviour of earth materials used for building construction, (b) the thermal performance of bentonites employed for the storage of nuclear waste and (c) the estimation of the heat exchange in shallow geothermal reservoirs. Finally, the proposed model can be easily implemented in a finite element code to perform numerical simulations to study the heat transfer in unsaturated geomaterials.
... Therefore, it is recommended that BTES should make dual use of engineering structures of newly built projects, e.g., piled foundations, retaining diaphragm walls, and tunnel linings. Otherwise, geothermal drills should be restricted (Eugster and Sanner, 2007) within the areas of massive UUS development or the protected groundwater zones. ...
Article
Full-text available
Underground space has been widely used in densely populated cities across the globe, and is attracting increasing attention among academics and practitioners toward further alleviating land use pressure, improving urban resilience and the quality of life. However, few attempts have been made to probe the potential threats posed by underground space use to urban sustainability. Disregarding these threats and the socio-environmental losses accruing to unreasonable underground space use will lead to failure in the decision-making process, particularly the cost-benefit analysis, of underground space development and may to some extent compromise the urban sustainability. This research intends to investigate the potential socio-environmental losses caused by underground space use for urban sustainability from the perspectives of underground assets, including geothermal energy, groundwater, geomaterials, historical heritage, space continuum and organisms, based on their contributions to sustainable development goals (SDGs), and sets up a framework for the monetary valuation of these losses. It is anticipated that the findings of this study will assist the future planning and decision-making process in developing the sustainable urban underground space.
... APROVECHAMIENTO DE LA ENERGÍA GEOTÉRMICA SUPERFICIAL EN LA OBRA PÚBLICA TABLA 2. Almacenamiento térmico subterráneo en acuíferos y en sondeos. Basado enEugster & Sanner, 2007. ...
Article
Full-text available
Geothermal resources represent a great potential of directly usable energy, especially in connection with foundations and heat pumps. Since the beginning of the 1980s geothermal energy has also been increasingly obtained through foundation elements in some countries as Austria and Switzerland. This innovation makes use of the high thermal storage capacity of concrete. Energy foundations and other thermo-active ground structures mainly consist of earth-contact concrete elements (diaphragm walls, basement slabs or walls, tunnel linings) that are already required for structural reasons, but which simultaneously work as heat exchangers after the installation of absorber pipes filled with a heat carrier fluid. This paper focuses in the current state of geothermal energy applications related to transport infrastructure and public works in general. Real cases on geothermal installations for heating systems in railway stations and tunnels, snow melting systems for roads, bridges, railways platforms and runways at airports are presented in this review. Finally, two additional possibilities are briefly explained: Underground Thermal Energy Storage systems (UTES) and geothermal desalinization systems.
... Although much of the early ATES research has focused on storage at high temperatures (Molz et al., 1983(Molz et al., , 1978Nagano et al., 2002;Réveillère et al., 2013;Tsang, 1978 ), most practical experience with seasonal ATES systems has in recent years been gained in particularly several European countries (Eugster and Sanner, 2007;Fry, 2009;Haehnlein et al., 2010;Willemsen, 2016). These ATES systems seasonally store thermal energy at relatively low temperatures (< 25°C) alternating between cooling and, assisted by a heat pump, heating mode ( Fig. 1). ...
Article
Full-text available
Aquifer thermal energy storage (ATES) is a technology with worldwide potential to provide sustainable space heating and cooling using groundwater stored at different temperatures. The thermal recovery efficiency is one of the main parameters that determines the overall energy savings of ATES systems and is affected by storage specifics and site-specific hydrogeological conditions. Although beneficial for the optimization of ATES design, thus far a systematic analysis of how different principal factors affect thermal recovery efficiency is lacking. Therefore, analytical approaches were developed, extended and tested numerically to evaluate how the loss of stored thermal energy by conduction, dispersion and displacement by ambient groundwater flow affect thermal recovery efficiency under different storage conditions. The practical framework provided in this study is valid for the wide range of practical conditions as derived from 331 low-temperature (<25 °C) ATES systems in practice. Results show that thermal energy losses from the stored volume by conduction across the boundaries of the stored volume dominate those by dispersion for all practical storage conditions evaluated. In addition to conduction, the displacement of stored thermal volumes by ambient groundwater flow is also an important process controlling the thermal recovery efficiencies of ATES systems. An analytical expression was derived to describe the thermal recovery efficiency as a function of the ratio of the thermal radius of the stored volume over ambient groundwater flow velocity (Rth/u). For the heat losses by conduction, simulation results showed that the thermal recovery efficiency decreases linearly with increasing surface area over volume ratios for the stored volume (A/V), as was confirmed by the derivation of A/V-ratios for previous ATES studies. In the presence of ambient groundwater flow, the simulations showed that for Rth/u <1 year, displacement losses dominated conduction losses. Finally, for the optimization of overall thermal recovery efficiency as affected by these two main processes, the optimal design value for the ratio of well screen length over thermal radius (L/Rth) was shown to decrease with increasing ambient flow velocities while the sensitivity for this value increased. While in the absence of ambient flow a relatively broad optimum exists around an L/Rth-ratio of 0.5–3, at 40 m/year of ambient groundwater flow the optimal L/Rth-value ranges from 0.25 to 0.75. With the insights from this study, the consideration of storage volumes, the selection of suitable aquifer sections and well screen lengths can be supported in the optimization of ATES systems world-wide.
... Although much of the early ATES research has focused on storage at high temperatures (Molz et al., 1983(Molz et al., , 1978Nagano et al., 2002;Réveillère et al., 2013;Tsang, 1978 ), most practical experience with seasonal ATES systems has in recent years been gained in particularly several European countries (Eugster and Sanner, 2007;Fry, 2009;Haehnlein et al., 2010;Willemsen, 2016). These ATES systems seasonally store thermal energy at relatively low temperatures (< 25°C) alternating between cooling and, assisted by a heat pump, heating mode ( Fig. 1). ...
Article
Full-text available
Aquifer thermal energy storage (ATES) is a technology with worldwide potential to provide sustainable space heating and cooling using groundwater stored at different temperatures. The thermal recovery efficiency is one of the main parameters that determines the overall energy savings of ATES systems and is affected by storage specifics and site-specific hydrogeological conditions. Although beneficial for the optimization of ATES design, thus far a systematic analysis of how different principal factors affect thermal recovery efficiency is lacking. Therefore, analytical approaches were developed, extended and tested numerically to evaluate how the loss of stored thermal energy by conduction, dispersion and displacement by ambient groundwater flow affect thermal recovery efficiency under different storage conditions. The practical framework provided in this study is valid for the wide range of practical conditions as derived from 331 low-temperature (< 25 °C) ATES systems in practice. Results show that thermal energy losses from the stored volume by conduction across the boundaries of the stored volume dominate those by dispersion for all practical storage conditions evaluated. In addition to conduction, the displacement of stored thermal volumes by ambient groundwater flow is also an important process controlling the thermal recovery efficiencies of ATES systems. An analytical expression was derived to describe the thermal recovery efficiency as a function of the ratio of the thermal radius of the stored volume over ambient groundwater flow velocity (Rth/u). For the heat losses by conduction, simulation results showed that the thermal recovery efficiency decreases linearly with increasing surface area over volume ratios for the stored volume (A/ V), as was confirmed by the derivation of A/V-ratios for previous ATES studies. In the presence of ambient groundwater flow, the simulations showed that for Rth/u <1 year, displacement losses dominated conduction losses. Finally, for the optimization of overall thermal recovery efficiency as affected by these two main processes, the optimal design value for the ratio of well screen length over thermal radius (L/Rth) was shown to decrease with increasing ambient flow velocities while the sensitivity for this value increased. While in the absence of ambient flow a relatively broad optimum exists around an L/Rth-ratio of 0.5–3, at 40 m/year of ambient groundwater flow the optimal L/Rth-value ranges from 0.25 to 0.75. With the insights from this study, the consideration of storage volumes, the selection of suitable aquifer sections and well screen lengths can be supported in the optimization of ATES systems world-wide.
... The potential for using ATES systems depends both on climatic and hydrogeological conditions; combining these two conditions showed that the application of ATES has potential in many areas over the world [1], and is therefore expected to rise in the future. Although the potential of ATES systems is largely not yet deployed in many parts of the world, practical experience with ATES systems has been developed in several European countries and elsewhere [2][3][4][5]. ...
Conference Paper
Full-text available
The application of seasonal Aquifer Thermal Energy Storage (ATES) contributes to meet goals for energy savings and greenhouse gas (GHG) emission reductions. Heat pumps have a crucial position in ATES systems because they dictate the operation scheme of the ATES wells and therefore play an important role in utilizing the storage potential of the subsurface. In the Netherlands, suitable climatic and geohydrological conditions in combination with progressive building energy efficiency regulation have caused the adoption of ATES to take off, resulting in a situation where demand for ATES exceeds the available subsurface space in many urban areas. The most important aspects in this problem are A) the permanent and often unused claim resulting from static permits for ATES operation, and B) excessive safety zones around wells to prevent interaction between wells. Both aspects result in an artificial reduction of subsurface space for potential new ATES systems. Recent research has shown that ATES systems could be placed much closer to each other, and that a controlled/limited degree of interaction between them can actually benefit the overall energy savings of an entire area. Two different simulation experiments were carried out to evaluate the effect of an adaptive permit capacity policy, as well as revised layout guidelines for ATES wells. Our solution provides a framework in which smaller distances between wells and adaptability of the permit volume plays a key role, to allow for optimal utilization of subsurface space for ATES and maximize GHG emission reduction. This paper shows how the total GHG emission reduction of an area can be increased by intensifying the use of the aquifer by allowing (some) interaction between ATES wells, which opens up unused but claimed subsurface space, and increase the number of heat pumps and ATES systems installed.
... Underground thermal energy storage in shallow aquifers (aquifer thermal energy storage, ATES; borehole thermal energy storage, BTES) has become an important opportunity to support a sustainable energy supply (Eugster and Sanner 2007;Kabuth et al. this issue). ATES systems are operated at temperature levels below 30°C (low-temperature [LT-] ATES), between 30 and 50°C (mediumtemperature [MT-] ATES), and above 50°C (high-temperature [HT-] ATES) . ...
Article
Full-text available
The temperature affects the availability of organic carbon and terminal electron acceptors (TEA) as well as the microbial community composition of the subsurface. To investigate the impact of thermal energy storage on the indigenous microbial communities and the fluid geochemistry, lignite aquifer sediments were flowed through with acetate-enriched water at temperatures of 10, 25, 40, and 70 °C in sediment column experiments. Genetic fingerprinting revealed significant differences in the microbial community compositions with respect to the different temperatures. The highest bacterial diversity was found at 70 °C. Carbon and TEA mass balances showed that the aerobic degradation of organic matter and sulfate reduction were the primary processes that occurred in all the columns, whereas methanogenesis only played a major role at 25 °C. The methanogenic activity corresponded to the highest abundance of an acetoclastic Methanosaeta concilii-like archaeon and the most efficient degradation of acetate. This study suggests a significant impact of geothermal energy storage on the natural microbial community and various metabolic activities because of increased temperatures in sediments with a temperature-related sediment organic matter release.
Article
The purpose of this paper is to present a new tool developed for the calculation and design of shallow closed-loop geothermal systems. Most of the available geothermal computer programs only allow to consider vertical heat exchangers configurations (i.e. single or double-U tubes), being the horizontal and helical designs excluded. As an attempt to fill this gap, GES–CAL tool, presented here, is capable of providing the complete design of all the most common configurations used in low enthalpy geothermal systems. This software was initially developed for its implementation in the region of Ávila (Spain), including the most relevant results of previous author’s researches in this area. Throughout this work, the new software is deeply described and implemented in the calculation of three different study cases. Results of GES–CAL are complementary compared with the ones obtained from the most used geothermal software, EED (Earth Energy Designer). From the analysis of these results, it was possible to conclude that GES–CAL tool constitutes an optimal solution for planning a shallow geothermal system, but especially for those installations placed in the region of Ávila. In this area, the well field can be designed in more precise way which results in lower drilling lengths and, hence, lower initial investments. The conclusions of this work indicate that GES–CAL offers remarkable advantages such as the automatic calculation of the space energy demand, the inclusion of all the heat exchanger configurations and an economic and environmental evaluation of the final geothermal solution.
Thesis
Full-text available
Article
Full-text available
After the German re-unification in 1990, the Reichstag building in Berlin was completely refurbished to house again the German Parliament, the "Bundestag". The design of this work was in the hands of the British architect Sir Norman Foster, and since the first presentation of his plans in 1992 the energy concept included a geothermal component, i.e. the storage of thermal energy in the underground. Two aquifers at different depth are used to store cold (ca. 60 m) and heat (ca. 300 m). The paper explains the system concept and the realised installation and presents first results of a monitoring campaign. The underground storage is operational since 1999, however, the full capacity of the total system and the final operational strategy could not be tested before completion of the energy network and all buildings involved in 2003. Both storage systems, after minor teething problems, performed to satisfaction. The monitoring was of great importance to detect and solve some operational inaccuracies and to optimise the system hardware as well as the operational strategies.
Article
EED, the "Earth Energy Designer", has been tested and used since summer 1995. Validation runs against measured data from existing plants show a rather good prediction of fluid temperatures. At a workshop in early 1996 the test users could present their experiences with EED. EED proved to be a useful tool for design of borehole heat exchangers for UTES and GSHP. One example shown here is a cold storage plant in Wetzlar, where EED was tested against measured data and simulations with the FD-model TRADIKON-3D.
Article
Geothermal Heat Pumps, or Ground Coupled Heat Pumps (GCHP), are systems combining a heat pump with a ground heat exchanger (closed loop systems), or fed by ground water from a well (open loop systems). They use the earth as a heat source when operating in heating mode, with a fluid (usually water or a water–antifreeze mixture) as the medium that transfers the heat from the earth to the evaporator of the heat pump, thus utilising geothermal energy. In cooling mode, they use the earth as a heat sink. With Borehole Heat Exchangers (BHE), geothermal heat pumps can offer both heating and cooling at virtually any location, with great flexibility to meet any demands. More than 20 years of R&D focusing on BHE in Europe has resulted in a well-established concept of sustainability for this technology, as well as sound design and installation criteria. Recent developments are the Thermal Response Test, which allows in-situ-determination of ground thermal properties for design purposes, and thermally enhanced grouting materials to reduce borehole thermal resistance. For cooling purposes, but also for the storage of solar or waste heat, the concept of underground thermal energy storage (UTES) could prove successful. Systems can be either open (aquifer storage) or can use BHE (borehole storage). Whereas cold storage is already established on the market, heat storage, and, in particular, high temperature heat storage (> 50 °C) is still in the demonstration phase. Despite the fact that geothermal heat pumps have been in use for over 50 years now (the first were in the USA), market penetration of this technology is still in its infancy, with fossil fuels dominating the space heating market and air-to-air heat pumps that of space cooling. In Germany, Switzerland, Austria, Sweden, Denmark, Norway, France and the USA, large numbers of geothermal heat pumps are already operational, and installation guidelines, quality control and contractor certification are now major issues of debate.
Langzeitverhalten der Erdwärmesonden-Anlage in Elgg/ZH Experiences with the borehole heat exchanger software EED
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  • Zürich
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Dissertation ETH Zürich, 1-139, 1991 Eugster, W.J.: Langzeitverhalten der Erdwärmesonden-Anlage in Elgg/ZH. Schlussbericht PSEL-Projekt 102, 1-38, 1998 Hellström, G. Sanner, B., Klugescheid, M., Gonka, T. and Mårtensson, S.: Experiences with the borehole heat exchanger software EED. Proc. Proc. 7th int. Conf
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AWP: Merkblatt T1: Wärmepumpen-Heizungsanlagen mit Erdwärmesonden. Arbeitsgemeinschaft Wärmepumpen (AWP), 1991/1996. Download: www.fws.ch BAFU: Wärmenutzung aus Boden und Untergrund. Bundesamt für Umwelt, Bern, work in progress; publication planned in 2007/2008, in German and French.
Erdwärmesonden -Funktionsweise und Wechselwirkung mit dem geologischen Untergrund
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Eugster, W.J.: Erdwärmesonden -Funktionsweise und Wechselwirkung mit dem geologischen Untergrund. Dissertation ETH Zürich, 1-139, 1991
Entwicklung, Validierung und Anwendung eines dreidimensionalen, strömungsgekoppelten finite Differenzen Wärmetransportmodells
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Brehm, D.R.: Entwicklung, Validierung und Anwendung eines dreidimensionalen, strömungsgekoppelten finite Differenzen Wärmetransportmodells. Giessener Geologische Schriften 43, 1-120, 1989
Market experience of four years of CO 2 thermosyphon heat source for heat pumps
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Mittermayr, K.: Market experience of four years of CO 2 thermosyphon heat source for heat pumps. Proc. 8th IEA Heat Pump Conf. Las Vegas, 2005
Novel CO 2 Heat pipe as earth probe for heat pumps without auxiliary pumping energy
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Kruse, H. and Rüssmann, H.: Novel CO 2 Heat pipe as earth probe for heat pumps without auxiliary pumping energy. Proc. 8th IEA Heat Pump Conf. Las Vegas, 2005