1. Sustainability in Public Works Conference
27 – 29 July 2014
Low Carbon Pool Heating: Getting the Temperature Right with Geothermal and
Cogeneration
C. Heal
1
1
City of Fremantle, Local Government
Email: craigh@fremantle.wa.gov.au
ABSTRACT: This article details the project approach, technologies used, key lessons learnt and
results, supported by detailed figures in order to provide conference participants with information and
recommendations on how best to conduct similar low carbon pool heating projects.
Councils’ pool leisure centres are typically the biggest source of greenhouse gas, consuming 10% to
30% of Council’s greenhouse profile and are a major expense. When the Fremantle Leisure Centre
was slated for major renovations in June 2013, it was the ideal opportunity to optimise the electrical
and heating demand for a facility that accounts for 15% of Council’s total greenhouse gas profile.
The pool heating project provided an innovative solution to a need for sustainability and energy
conservation by implementing the first of its kind low carbon technology arrangement, primarily led by
a 300kW geothermal heat pump, supported by a 76kW cogeneration unit, electrically led and
operating on peak periods and supplemented by a wing of instantaneous natural gas boilers. These
elements were integrated with new supporting piping and plant room equipment, BMS automation,
flow and temperature monitors and housed in a new custom mechanical plant room.
This is the first time these technologies have been incorporated within an Australian Local
Government.
KEYWORDS: Local Government, geothermal, cogeneration, natural gas boilers, pool, leisure centre.
1 Introduction
The City of Fremantle has a policy to be a
carbon neutral city. As part of this commitment,
abatement measures and energy efficiency
projects are frequently conducted. When
Council decided to upgrade its premier leisure
and swimming centre, the forty year old
Fremantle Leisure Centre (FLC), it naturally
researched low-carbon options. This heating
project was part of a 10 month, $6 million
overhaul of the centre which concluded in April
2014. This project included a geothermal
heating system, cogeneration plant, resurfaced
pools, upgraded change and restrooms,
aquatic playground area and access ramps to
all pools.
2 Objectives
The project’s key objectives were:
 To heat the FLC’s two main pool bodies
independently to different temperatures in
a sustainable, cost effective manner.
 Improve the operation and automation of
pool heating and chemical dosing
equipment.
 Improve the pool amenity, operations,
safety and functionality for all
stakeholders.
 Reduce greenhouse gas emissions at the
FLC, as it is the City’s largest single
source of emissions.
 Implement the project to be consistent
with the City’s Strategic Direction 2010-
2015 report and the Low Carbon City
Plan, which calls for a 40% reduction in
greenhouse gas emissions by 2020.
3 Determining the ideal pool heating
technology mix
The City evaluated the site’s electricity and gas
consumption data to determine the thermal
and electrical energy load requirements. This
was modelled against 12 technologies to
determine the optimal solution against a
number of sustainability and financial criteria
including capital, maintenance and
replacement cost, energy efficiency and
greenhouse gas profile. The technologies were
then deployed on a merit basis, with the best
technology applied first as determined by the
weighted criteria. In this fashion, once a
preferred technology’s capacity was expended
and if energy was still required, the next best
technology was selected until all thermal
energy needs were met and an operating
strategy could be developed [1].

2. This process identified that the ideal
technology mix was a 75kW cogeneration
system electrically led, a 300kW heat pump
extracting heat from a 160m geothermal
borefield supplemented by a wing of
instantaneous natural gas boilers.
Figure 1: View of the plant room showing all
heating units installed. Left to right:
cogeneration unit, geothermal heat pump and
gas boiler wing.
FLC already has a 30 kW solar PV system
installed. This is sizing limit before reverse
power protection is required to protect the grid.
Additional PV’s were not considered as the
cost to comply with this protection requirement
made them non-competitive against the
weighted criteria.
Modelling and determining optimal
solution
Modelling of the FLC’s energy consumption for
heating over 2011 and 2012 was analysed with
respect to predicted future energy
requirements. This informed the request for
tender process, seeking the provision of
geothermal heat pumps, cogeneration and
boiler units. The preferred tender respondent’s
technical characteristics were then modelled to
evaluate if they could be utilised within the
expected operating strategy to meet the
required thermal load.
The heat load was examined in greater depth
because it drastically affects the pool’s heating
operating strategy, financial viability and
greenhouse abatement potential. Figure 2
details how each heating element contributes
to the required average monthly thermal load.
Little heat energy is required in summer
months; the heat pump supplies base load
augmented by the cogeneration unit almost
exclusively. The geothermal heat pump
supplies primary heat energy throughout the
year and is designed for steady constant use.
The cogeneration unit supplies a steady supply
during peak times throughout the year; some
heat rejection in summer occurs, a minor
amount in the winter. The boiler supplies top
up during cold weather months, and in peak
use and maintenance events.
Figure 2: Monthly average contribution to
thermal load [1].
Drilling down to average daily profiles for
different months reveals the FLC’s very
different hourly thermal heating requirements
and the specialisation of the different heating
units, and determines the features of the
overall heating operating strategy. Examples
from January and July are provided below in
Figures 3 and 4 for consideration.
January’s high ambient heat means little
thermal load is required to heat the FLCs. The
facility’s high relative HVAC energy
consumption makes it more profitable to run
the cogeneration unit for its electrical
contribution and reject nearly all the heat load
to the atmosphere than heat the pools through
other sources.

3. Figure 3: Daily average contribution to thermal
load in January [1].
In July, the FLC’s heating requirements are
much greater, such that a fully loaded heat
pump cannot supply the full heat required. In
this case, the boiler is preferentially used
during the off-peak period and the
cogeneration unit kicks in at peak periods as it
is now cheaper to produce energy through the
cogeneration unit than by using the boiler. A
much lower amount of heat from the
cogeneration unit is rejected to the atmosphere
as it is required by the pools. Greater
greenhouse gas abatement could be achieved
by running the cogeneration unit all the time,
but the financial cost is excessive compared to
the implemented alternatives.
Figure 4: Daily average contribution to thermal
load in July [1].
4 Heating technologies employed
Each heating technology’s project
characteristics are explained in turn, to detail
how they benefit the FLC’s heating operating
strategy.
Geothermal Heat Pump
A number of pools in Perth have used aquifers
approximately 1,000 metres deep; however,
the City opted for a shallow bore as it greatly
reduces both risk and capital outlay.
A 300 kW closed geothermal heat pump draws
water from the Leederville aquifer 160m below
the ground. The water, which exits the aquifer
at 27°C, is passed through the heat pump and
then re-injected back into the aquifer via a
separate injection bore. The bore water is
passed through a heat plate exchange and is
applied to the FLC’s swimming pool. The water
is reinjected at 22°C into the borefield. Though
the water only transfers 5°C of heat energy to
the pool water, it is significant because it is
being circulated at 12L/s. See figure 5 for a
schematic.
Figure 5: Closed loop shallow geothermal
energy schematic [1] based on [4].
The system is designed to provide primary
heating to the FLC’s pools at all times. It is the
most cost effective and has the lowest
greenhouse gas profile per unit of heat energy
produced. The heat pump operates at an
impressive COP of over 6.0 all year round,
heating the pools efficiently. That is, for every
1 unit of energy applied to the heating
components it generates 6 units of energy.
Although the temperature was greater at the
maximum depth of 264m (27.8-29.9°C) than at
the final bore depth selected of 160m (26.5-
27.2°C), the geology at this depth made it a
more favourable reservoir to obtain the
necessary water flow into the long term [2].

4. Figure 6: Geothermal bore construction
The actual pumped groundwater temperature
is about 0.5°C lower due to heat losses
through the bore casing and headworks.
The City was fortunate in that bore yielded
water that was hotter than preliminary
investigations projected. This increased the
amount of geothermal heat energy recoverable
from the system and improved overall
efficiency. Having a clear understanding of the
borefield geological composition at
construction is vital for determining the
reinjection rate and overall operating strategy
of the geothermal heat pump.
C Murphy’s Hydrogeological Masters thesis
report determined that the FLC’s borefield has
a service life of 50 years before reaching
thermal equilibrium [3]. The localised cone of
depression over time is negligible, as the
system is closed, this positively contributes to
the sustainability of the groundwater resource
use. This means there is projected to be a
viable hot groundwater resource at the
required depth to justify a complete
replacement to the current heat pump at end of
life.
Figure 7: Comparison of temperature
prediction models for the borefield over fifty
years [3].
The City’s strategic plan for another pool at the
FLC in the longer term meant that the diameter
of the hole drilled for the bore was larger than
is currently required to heat the pools. The
bore can produce 18 L/s but will only use 12
L/s for the time being. Once the new pool is
built, the bore will then be fully utilised and
should achieve a coefficient of performance of
around 7.3. This bore design was selected as
an optimisation of the FLC’s long-term heating
needs, flow rate against borefield longevity and
present needs. The cost to drill a larger
diameter hole is not significantly greater.
The heat pump has a projected 25 year
service life and requires just a weekly visual
inspection and annual maintenance.
Cogeneration
The City has decided to deploy cogeneration
to reduce the FLC’s use of grid electricity and
to use waste heat from this process to heat the
swimming pools.
Cogeneration produces two forms of usage
energy, in this case heat and electrical. The
system selected is a reciprocating engine
fuelled by natural gas. It has an efficiency of
85% and has the benefit of on-site power
providing energy security, lower greenhouse
gas and greater cost certainty.

5. Figure 8: Schematic of a typical cogeneration
system [1] based on [5].
The cogeneration unit will generate 75 kW of
electricity for the facility and 120 kW of heat for
the FLCs. The cogeneration system will only
operate in peak electricity times to improve
financial return. Modelling showed operating
the cogeneration system to meet the thermal
demand resulted in the highest greenhouse
gas savings. The system will be slightly
undersized to limit excess electricity created as
export of electricity to the Perth grid is
presently not allowed. In this case, it will pass
through protection resistance or will be
throttled back as required. Figure 9 details the
cogeneration unit’s operating strategy by
month against grid electricity. Using the
cogeneration facility solely during peak
increases the system’s long service life.
Figure 9: Electricity source for pool heating by
type and month [1].
Gas instantaneous boilers
A supplementary wing of gas instantaneous
boilers were also installed to provide heat top-
up during the middle of winter, at peak events
and to supply heat during the heat pump and
cogeneration units maintenance events.
Supporting technologies
All technologies operate through an advanced
Building Management System (BMS) which
can manage fine heating characteristics
including diverting 100% of each unit’s heating
capacity to either the 50m or 25m pools via
three-way valves and a pool piping manifolds.
Figure 10: Heating system manifolds, pumps
and heat exchangers for both pool bodies.
The BMS unit also controls the entire plant
room including main filter pumps, all gas
boilers, bore pumps and monitoring
equipment, heat pump, electricity grid
connection and the CHP system. The BMS
system can be monitored remotely via PC or
smartphone and includes a centralised control
console.
Figure 11: Upgraded electrical motor control
board and BMS.

6. 5 Results
Since commencing operation in April 2014, this
mix of low carbon technologies will save
Council annually, over $100,000 in decreased
operating cost, a facility energy reduction of
around 25%. Abate 250 tonnes of greenhouse
gas and shave 5% off the City’s total
greenhouse gas profile.
While the total amount of energy required to
heat the Centre’s pools will remain the same, it
will now come from cheaper sources, with
lower operating, staffing and maintenance
requirements that also produce fewer
emissions. The pools will now be heated with
greater levels of control and specialisation.
The cost savings are achieved through lower
gas use to power the bore, and onsite
generation of electricity rather than purchasing
off the grid. The cogeneration system is
expected to supply about 273 MWh of
electricity annually and approximately 390
MWh of heat per year.
Simple payback cost recovery will occur in
year 12. Complex payback including ongoing
costs will occur around year 15. The project’s
return on investment rapidly improves in years
20 to 30 as maintenance costs are lower and
life of the equipment is much greater than the
previous boiler system.
6 Recommendations
Recommendations for other parties
considering undertaking a similar project are
listed by order of where they appear in a
heating project’s progression:
1. To ensure the long term operation of
heating elements it is vital to have at least
two years of detailed time of use
electricity and energy data for the facility
and have it interpolated by energy
engineering experts to define renewable
energy needs. The Australian Local
Government pool cogeneration
experience could be reasonably
summarised as being oversized, leading
to overheating and suboptimal usage and
performance issues.
2. Business cases for these projects are
more favourable when including nett
present value, discount or internal rate of
review calculations rather than just simple
payback due to the long product life of
equipment and improved financial return
in later years against higher initial capital
outlay. This will allow decision makers to
more completely evaluate the full financial
worth of a proposed project.
3. Determine all costs and project particulars
prior to commencement. Costs to repair
underground services or rehabilitate grass
are expensive and often unexpected.
Other costs like equipment ventilation and
detailed piping design cannot be
reasonably anticipated at the planning
stage and costs must be sourced from an
allocated contingency budget. Keeping a
close eye on project creep is required.
4. Consider whether an equipment
performance contract or acquiring an
Owners Engineer will achieve the City’s
quality assurance and project expertise
needs.
5. Clearly define performance levels
expected, redundancy in design,
equipment calibre and operating schedule
to ensure a tailored response from
tenderers.
6. Take time to develop tender and contract
documentation for supply and
implementation of capital equipment.
Conduct detailed quality assurance,
change control register and signoff to
ensure promised outcomes are achieved.
7. Obtain integration approvals with
electricity network provider as soon as
equipment specifics are known and
advise as changes occur as this process
is lengthy. The requirements in Western
Australia are particularly lengthy
compared to the eastern states.
8. Pay special attention to all stakeholders.
Like all Local Government projects,
community consultation and information
was vital. It was important to manage
community’s perception and expectations
against the larger pool upgrade. A
detailed communication plan is advisable.

7. 7 Conclusion
The City is pleased with the outcome of the
project. It has achieved all project objectives
and an overall operational efficiency of around
5.5 coefficient of performance for all pool
heating components [1]. This is an especially
favourable result compared to a typical pool
heating system utilising a gas boiler and prior
base case which has a coefficient of
performance of less than 2.
Figure 12: Final operational mechanical plant
room.
Acknowledgements
The project received $356,048 in Community
Energy Efficiency Program funding under the
Commonwealth Government’s Clean Energy
Future program, Improving Australia’s Energy
Efficiency.
The City of Fremantle would like to
acknowledge the following principal
contractors listed by contract size for their
invaluable contribution to the project.
 WellDrill
 EvoHeat
 Shenton Aquatics
 Energy Made Clean
 Rockwater
 WESCO
Figure 13: City of Fremantle Project
Councillors, Staff and drilling contractors at
borefield commencement.
Figure 14: Principal heating technology
contractors and Project Manager on site pre-
construction.
References
1. Energy Made Clean, 2014, “Fremantle Leisure
Centre Heating Design Review”, Perth.
2. Rockwater, 2013, “H2 Level Hydrogeological
assessment and bore completion report for the
Fremantle Leisure Centre Geothermal
Borefield”, Perth, pp 20.
3. C Murphy, 2014, “Evaluation of the effect of
different analytical, conceptual and numerical
models on predictions of impact of a
geothermal doublet system in the Perth Basin”,
Masters of Hydrogeology Research Thesis,
University of Western Australia, pp. 1-37.
4. Sonic Samp Drill Company referenced in
Energy Made Clean, 2014, “Fremantle Leisure
Centre Heating Design Review”, Perth, pp 6.
5. Gandras Energy Company referenced in
Energy Made Clean, 2014, “Fremantle Leisure
Centre Heating Design Review”, Perth, pp 5.