Geothermal the other sustainable option
01 March 2019
When most people hear the term
Geothermal,
they usually think of large-scale
power generation. But Geothermal is a
viable, clean heat source that can provide substantial operational
cost
savings for many
precinct level developments – even in the middle of a
busy city..
Geothermal has long been considered a viable way of generating power,
for individual
building or small precincts. However, the start-up
investment for a facility capable of powering a city is considerably
greater than other
clean energy sources, such as solar or wind. A key
difference is that Geothermal also offers a reliable, cost effective and
unobtrusive solution to the heating needs of precinct developments and
public facilities.
NDY Associate Director Jeff Dusting has worked on several Geothermal
heating projects, and believes that there can be significant operational
cost benefits as well as improved occupant experience with a localised
geothermal system. “In the right project, Geothermal can lower
operational costs, as well as providing a near-neutral carbon footprint
for the precinct,” he says. “This operational saving improves cash flow
for the owners, as well as lowering the expenditures of tenants and
users of the facility. One recent example is Scarborough Pool in
Perth. The Geothermal system is so efficient that there is no
requirement to use solar blankets or boilers for the outdoor pool. This
also saves on staff time, keeping costs down even further.”
What exactly is geothermal?
Geothermal is essentially using the natural heat found deep underground
to power or heat a building above ground. This can be ambient heat from
over a kilometre underground, or tapping in to
water sources that are heated by underground activity, such as
geysers or hot springs.
This same heat can be used to generate electricity by boiling water (or
a specialised liquid such as pentane) so that it generates steam and
turns a turbine on a dynamo, generating power. Geothermal power
generation can be a sophisticated process, but as a source of heat, the
process is much simpler.
Geothermal heating
Geothermal power generation requires temperatures high enough to boil
water, requiring very deep wells and pipes. This increases the initial
cost considerably, however, the temperatures for heating a building to
comfortable levels are substantially lower. This means that the depth
and complexity of the system can be reduced, making it viable for much
smaller scale projects.
Direct Vs indirect heat transfer
Geothermal heat transfer comes in two main types, Direct and Indirect.
Indirect uses heat from deep below the surface to heat a refrigerant,
which is then used to warm up the environmental systems. The Scarborough
Pool in Perth uses this type of system, providing with a constant supply
of warm water to keep the pool heated and comfortable all year round.
Direct geothermal energy uses pipes that are sunk just a few metres into
the ground to extract heat in winter for heating (through direct heat
transfer through the metal, or via a refrigerant pumped through the
pipes) and to sink the heat in summer, cooling the building.
Some buildings can utilise both systems simultaneously. NDY designed one
of the first geothermal projects in Manchester. The First Street Site is
a 250,000 sq m mixed use development that utilises a ground source heat
pump that taps into the heat capacity of the ground, which at 12m below
the surface remains fairly constant. This improves the efficiency of the
building’s heating and cooling plant. Closed loop boreholes effectively
use the ground as a heat “sink” throughout the year whereby energy from
the ground is either rejected (cooling) or absorbed (heating) into the
system.
The borehole array can then be connected to a series of water-cooled
variable refrigerant flow (VRF) units, which provide both the heating
and cooling for the building. This complements the other boreholes that
were installed at a depth of 150m. These boreholes have the potential to
provide up to 300kW of peak heat rejection, representing over 20 per
cent of the cooling demand for the building. In heating mode, it has the
ability to deliver 188kW of heat absorption, as well as keeping the
“ramp up” costs down when heating or cooling is turned on for the day.
“These geothermal systems don’t generate electricity, but they save a
lot of it in the building,” says Jeff. “Energy use in buildings accounts
for about one quarter of Australia’s greenhouse emissions, and over half
of this is for heating and cooling. With a geothermal system, we can
slash the carbon output to basically nothing, and minimise the ongoing
heating and cooling costs for the project,” he adds.
NDY has worked on several other geothermal projects around the world.
Including one of the first geothermal projects in Manchester, England.
Number One First Street is a mixed use building, with tenants that
include Manchester arts organisations, Cornerhouse and Library Theatre
Company, a four star Melia hotel, 700 space multi storey car park, nine
new restaurant/café units, student accommodation and a new public
square.
The project used ground source heat pump systems to access the heat
capacity of the ground, which at 12m below the surface remains fairly
constant to improve the efficiency of a buildings heating and cooling
plant. Closed loop boreholes effectively use the ground as an energy
“sink” throughout the year whereby energy from the ground is either
rejected (cooling) or absorbed (heating) into the system.
The ground source heat pump and borehole solution takes advantage of the
moderate temperatures in the ground to boost the efficiency of the
mechanical systems and reduce the running costs of heating and cooling
plant.
The biggest advantage of such systems is gained when heating and cooling
is carried out throughout the year, as the heat rejected in summer is
stored in the ground and used for heating in winter.
Retrofitting Geothermal
“There’s this school of thought that geothermal is only for new
buildings,” Jeff says. “That’s just not the case. There are many ways to
integrate a cost-effective geothermal solution into an existing
building, even in a major metropolitan area.”
NDY has refitted several buildings with geothermal systems, including X
Y and Z.
Geothermal for Pools
“Pools and aquatic centres represent a large number of our geothermal
projects,” says Jeff. “The heat requirements of these facilities make
geothermal a very attractive option, with a very short payback period.”
By using renewable energy to heat the water, rather than traditional gas
boilers, hundreds of tonnes of Carbon are saved, as well as significant
operational costs. At the Scarborough pool, the City of Sterling
estimates that the geothermal system saves them around half a million
dollars in heating costs per year, a saving that allows the council to
put funds to much more practical use.
As precinct level power generation and services sharing becomes more
popular, geothermal will also form an integral part of providing
precinct level sustainable solutions.
The Benefits of Geothermal
It’s always available.
Unlike other renewables such as solar and wind, geothermal is always
operational. The temperature of the rock deep underground is reasonably
constant, making the system predictable and efficient.
Low maintenance costs.
The simplicity of the system means it’s cheap to operate. Initial setup
can be expensive, but this can be rapidly offset by operation savings.
A renewable heating solution
Even if the system is taking advantage of a natural reservoir of water
underground, with proper management, the water taken can be less than
the water that feeds into the system. A closed loop system takes nothing
from the environment except heat, making it a very low impact method of
heating.
A simple solution, even at a small scale
The system essentially has just a few basic components: Underground
pipes, some pumps, and a heat exchanger. By keeping it simple,
maintenance costs are reduced.
SOME OF NDY’S GEOTHERMAL PROJECTS INCLUDE:
-
ST HILDA’S SCHOOL FOR GIRLS – 50 M OUTDOOR POOL
-
SCARBOROUGH OUTDOOR POOL
-
RIVERTON LEISUREPLEX INDOOR AQUATIC CENTRE – CONVERSION TO GEOTHERMAL HEATING
-
MANDURAH AQUATIC RECREATION CENTRE
-
HALE SCHOOL – OUTDOOR 50M AND LTS POOL
Read the latest Lifecycle Magazine here: http://www.ndy.com/wp-content/uploads/2018/08/LifeCycle24web.pdf
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Source: Norman Disney & Young - www.ndy.com
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