This page of Geoflow website provides in-depth knowledge obtained by Geoflow over the last decade about cost effective, reliable and efficient energy resources for mostly heating and cooling. Please have a read and ask us if you have any question and we will be glad to share all our experience with you.

Geothermal Heating and Cooling

Geothermal systems efficiently heat and cool buildings using sustainable geothermal energy accessed via Ground Heat Exchangers (GHEs). In closed loop systems, GHEs comprise pipes embedded in specifically drilled boreholes or trenches or even built into foundations, all within a few tens of metres from the surface. The geothermal systems are just starting to be generally known in Australia with relatively few, but highly varying and diverse installations to date offering a potentially economically viable and environmentally friendly method for heating and cooling of buildings.

However, they require excavation or drilling to bury the GHEs which lead to higher capital costs for installation in comparison with conventional systems. The design of GHEs in Australia is mostly achieved with simple rules of thumb, and simple software that has been developed but not validated for the GHE design.

The high capital cost of GHE installation is one of the main causes preventing wide adoption of direct geothermal systems in Australia. It is therefore imperative that GHEs should be designed as efficiently as possible to minimize the extent and cost of GHE installation.

At GeoFlow Australia, we are using the current design methods together with the design methodology achieved by our head of design team, Dr Amir Kivi through 4 years of research at The University of Melbourne. This is to ensure that the GHE is sized to the needs of the house and to avid under-sizing and over-sizing the heating and cooling system.

Principal Elements of a Geothermal System

The principal elements of a direct geothermal system are shown in figure below

• The heating and cooling demand of the building,
• The Ground Source Heat Pump (GSHP) which causes heat to flow “uphill” from lower temperature to higher temperature,
• The Ground Heat Exchanger (GHE) pipes buried within a few tens of metres of surface as a heat source in winter and heat sink in summer.
A heat transfer fluid (typically water) is circulated through GHE pipes and exchanges heat with the surrounding ground. If the fluid is cooler than the ground, the ground will heat it and if the fluid is hotter than the ground, it will be cooled. GSHPs efficiently upgrade the heat extraction/rejection process. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor heat delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger. Read more

The key to the direct geothermal system is that for each kilowatt of electrical energy put into a direct geothermal system, depending on several parameters, about 4 kilowatts of energy is developed for the purposes of heating and cooling. This means that direct geothermal systems could reduce electricity demand for heating and cooling by 75%.  Furthermore, as much of the electrical power in Victoria is generated with brown coal, replacing 75% of the energy used with a clean and free renewable energy source, these systems will have the potential to significantly cut Australia’s carbon footprint.

It is estimated that there are over 3 million direct geothermal systems installed around the world, with the total installed capacity approximately doubling every 5 years since 2000 (Lund et al., 2010). Figure below shows the growth rate of the installed capacity and annual utilization of all forms of geothermal energy for heating and cooling applications (Lund, 2010). In the following, each of the elements of a direct geothermal system is discussed in more detail.

Types of GHE configuration

Lund (2002), Banks (2008) and Self et al. (2012) provide an excellent overview of different forms of GHEs. Based on their distinctive characteristics, different GHE configurations are classified in Figure ‎below.


Closed loop GHEs comprise pipes placed in the ground or water through which a fluid circulates and the heat exchange occurs by conduction through the walls of the pipes. Therefore, the fluid remains sealed in the pipes and does not come into contact with the energy storage medium. There are several advantages to this system. One of the main advantages is that there is no problem of contamination either from the loop water entering the ground, or perhaps more critically, from the ground water contaminating the workings of the pumps. Read more

Where there is a confined surface area or minimum disruption of the landscape is desired, GHEs in form of vertical boreholes (of varying diameter) comprising one or more “U-loops” of high density polyethylene (HDPE) pipe are installed in a borehole backfilled with cement/bentonite grout.

Horizontal trenches are usually the most cost-effective when adequate area is available around the building and trenches are easy to dig. Figure ‎below shows different configurations of horizontal GHE that can be constructed. The horizontal GHE has become increasingly popular due to its low cost and ease of installation. For instance in Canada, about 55% of direct geothermal installations use horizontal GHEs (CGC, 2011). Nevertheless a horizontal GHE requires a large area of ground to lay the pipe network. This problem can be alleviated to some extent by employing a slinky loop arrangement of the pipes. Slinky arrangements are coils of overlapping piping, which are spread out and laid either horizontally or vertically. The first recorded slinky GHE was developed by Bose (1992). This GHE’s ability to focus the area of heat transfer into small volume reduces the length of the trenches by 20-30% of those for single pipe configuration (Wu et al., 2010). The slinky coils can have different lengths per unit length of trench depending on the pitch spacing of successive coils. The performance of slinky coils is similar to straight pipes with an equivalent total length (IGSHPA 2011).

In an urban environment, the ground immediately below a city can be used as a low grade energy storage reservoir. Geotechnical structures such as piles, tunnels, sewers, retaining walls and ground slabs can be regarded as thermo-active structures by simply embedding GHE pipes in them. The literature includes several studies of these thermo-active structures (Adam and Markiewicz, 2009; Xia et al., 2012). For example, if the building is a large commercial or industrial building with significant foundations including large diameter piles, then it is almost certain that these elements will provide the location for the GHE. 

Single and stacked multiple pipe
Serpentine type
Slinky (one diameter pitch)
Slinky (half diameter pitch)

Vertical Ground Heat Exchanger

Where there is a confined surface area or minimum disruption of the landscape is desired, Ground Heat Exchangers (GHEs) in form of vertical boreholes (of varying diameter) comprising one or more “U-loops” of high density polyethylene (HDPE) pipe are installed in a borehole backfilled with cement/bentonite grout.

Water Loop Heat Exchanger

Where there is a body of water in the form of a dam or lake within a reasonable distance from a building, these surface water bodies can also be considered as an energy source. Water loops are gaining popularity because they require no drilling or excavation. These systems, due to an efficient heat exchange interface, potentially require less piping than other GHE configurations. In closed water loops, HDPE coils are attached to a frame and submerged in a water body. The coils are typically supported 0.5m above the lake bottom to allow for convective flow around the piping. Normally the coils should have at least 1.8m of water above them (Self et al., 2012). It is necessary to assure sufficient thermal mass is maintained during low water conditions and prolonged draughts. The CGC (2010) also mentions that in cold climates, if a water body depth is less than 3m, lakes and dams destratify and offer no advantage. Due to flooding and draughts as well as hazards due to moving debris that can damage the GHE, rivers are not ideal for this application.


Open Loop Heat Sources

An open water loop system involves water being removed from the ground or body of water and returned after heat is extracted or added. Clearly, considerable care must be directed at the location of the return system so that the discharge water does not affect the intake temperatures. One of the major advantages of these systems is that relatively large volumes of water can be handled leading to large quantities of heat exchange.


Energy Pile Ground Heat Exchanger

In an urban environment, the ground immediately below a city can be used as a low grade energy storage reservoir. Geotechnical structures such as piles, tunnels, sewers, retaining walls and ground slabs can be regarded as thermo-active structures by simply embedding GHE pipes in them. For example, if the building is a large commercial or industrial building with significant foundations including large diameter piles, then it is almost certain that these elements will provide the location for the GHE.

Ground source Heat Pump (GSHP)

According to the Second Law of Thermodynamics, heat cannot by itself move from a lower temperature to a higher temperature (just as water cannot by itself flow uphill). Heat pumps on the other hand, can move heat from lower temperature to higher temperature regions (just as water pumps can move water uphill). Heat pumps are typically used to transfer the ground’s energy to heat or cool buildings. The principle of a heat pump is illustrated in Figure below for the cooling mode of operation of a water to air heat pump.

The operation of a Ground Source Heat Pump (GSHP) in cooling mode of operation (IGSHPA 1988)


As shown in Figure ‎above, in cooling mode of operation, water from the ground loops passes through the primary circuit heat exchanger (the condenser) of the heat pump. Here, this water comes into indirect contact with the warmer gas refrigerant. Heat passes from the warmer gaseous refrigerant to the cooler water. As a result of the removal of heat from the refrigerant, it condenses to a liquid phase at a relatively high temperature. When this liquid then passes through an expansion valve, the temperature drops considerably ready to accept heat from the conditioned space. Heat passes from the warmer air from the conditioned space to the liquid refrigerant to cause it to evaporate. The gaseous refrigerant then passes into a compressor where the gas is compressed to significantly increase not only its pressure but also its temperature. The hot gas then passes through the condenser again and the refrigeration cycle continues. Read more

In the cooling mode of operation, the heat generated by the compressor is not useful and together with the heat extracted from the building, should be rejected to ground. In the heating mode of operation, the waste heat generated by the compressor electricity consumption is useful and is rejected to the building to assist in heating. The heat flux delivered at the condenser of a heat pump to the building is the sum of heat flux extracted from the evaporator/GHE and the electric power consumed by the compressor.

The “efficiency” of a heat pump is expressed as a coefficient of performance (CoP). This is defined as the ratio of heat delivered to the building( Qb in kW )

  to electricity consumption of heat pump(QE in kW) : QE in

Why Geothermal?

The key to the geothermal system is that for each kilowatt of electrical energy put into a geothermal system, depending on several parameters, about 4 to 5 kilowatts of energy is developed for the purposes of heating and cooling. This means that geothermal systems could reduce electricity demand for heating and cooling by 75%. Furthermore, as much of the electrical power in Victoria is generated with brown coal, replacing 75% of the energy used with a clean and free renewable energy source, these systems will have the potential to significantly cut Australia’s carbon footprint.

Solar Thermal Energy

Solar thermal heating uses direct heat from sunlight, without the need to convert the energy into electricity. Solar thermal water heating is the most developed solar technology and is very cost-effective when

you consider the life-cycle costs. For this reason the adoption of solar water heating worldwide is growing at an average rate of more than 25 % per year (Source[1]). The simplest form of solar water heating system is achieved by pumping water through pipes exposed to solar radiation. Heat is absorbed by pipes to heat the water flowing within the pipes.

Read more

There are different types of solar thermal collectors that are used to produce temperatures of about 100C or less which is applicable for many uses such as building heating and cooling, domestic hot water and industrial process heat. Solar thermal energy is well-suited for any energy intensive commercial applications including horticulture and greenhouses, Swimming pools and diary processing factories.

Large scale solar thermal (hot water collector system) can provide the lowest cost option for energy access. Using the solar thermal renewable energy resources can help to improve energy access, diversify farm revenues, avoid disposal of waste products, reduce dependence on fossil fuels and GHG emissions, and help achieve sustainable development goals. As of 2017-2018, there are range of subsidies available to assist dropping the capital cost of solar thermal system and make it the most feasible energy solution for high demanding agriculture/industrial/entertainment process.

Solar thermal panels which are mostly known as solar hot water panels comprise of set of water flow passes by which solar heat is conducted to the water flow and stored as thermal energy. Different types of solar hot water collectors are discussed and compared in the following sections.

Evacuated tubes collectors

Evacuated tubes perform best in cold climates with temperature well below zero degrees Like in Northern Europe. Evacuated tubes consist of a sunlight absorbing metal tubes, inside two concentric transparent glass tubes. The space between the two glass tubes is evacuated to prevent losses due to convection. Evacuated tubes have lower heat losses when generating high temperature hot water. However they cost almost twice the flat plate collectors and according to statistics by Sustainability Victoria, they are not the cost effective solution for Australian climate where outdoor ambient temperature seldom gets below zero degrees. Please see the comparison of collectors for further technical discussion.

Typical cross section through a evacuated tube solar array

Flat plate collectors with copper pipes and fins

These collectors are more widespread systems in the market. They use an array of 8-10 parallel copper pipes (risers) welded on both ends to a larger diameter copper collector pipes called headers. An absorber copper plate (fins), is welded to the riser pipes. The solar energy incident on the absorber plate is transferred to the fluid flowing through the riser tubes. Cool water enters at the bottom header and warmed water exits from the top header. The absorber is usually contained in an insulated box with a transparent glass.

Typical cross section through a conventional flat plate solar collector

Flat plate collectors with aluminium MPE section

Flat plate collectors with aluminium MPE section are mainly used in large area collectors for commercial and district heating and industrial applications. These collectors achieve the highest efficiency in flat plate collectors by using direct flow approach for heat. The fins are eliminated and water is touch with absorber in the full face of collector. In these collectors, the average distance for the energy to travel from absorber surface to circulation fluid is much shorter and heat distribution is much more even on the absorber. This leads to a fin efficiency of over 99% and practically no heat losses in the absorber.

The higher efficiency of solar hot water collector means collector will either supply more energy from an equal amount of installed collectors – or allow the required amount of energy to be harvested by using fewer collectors and requiring less land or roof space.

 Aluminium MPE absorber for flat plate collectors and water flow path

Comparison of efficiency of different solar collectors

Figure below shows the comparison between evacuated tube and flat plate solar collectors that has been averaged from the collectors available in Victorian solar market by Sustainability Victoria (SV). There is also unglazed collectors included in the comparison by SV which is not mentioned here clearly due to its low efficiency that can be seen from the comparison below. The horizontal axis in figure below shows the difference between solar hot water temperature inside the collector and ambient air temperature over irradiation intensity in W//m2. As the temperature difference rises (Due to colder ambient air temperature or very hot water generation by collector), the heat loss from collect increases which mean reduction in efficiency of the collector.

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For countries like Sweden with winter ambient temperatures of -20C, there are few benefits to evacuated tube collector over flat plat collector as it loses less heat in colder ambient temperatures. However, Australian climate is different and we seldom get any temperatures below zero degrees which mean the cheaper flat plate collectors even perform better that the expensive evacuated tubes. For demonstration, let’s compare the efficiency of flat plat collector and evacuated tubes for the worst case scenario in Australia which takes place in Melbourne climate (Zone 4 of Clean Energy Regulator). Melbourne is the main city in zone 4 of subsidy divisions and receives the least subsidies for renewables due to its less solar irradiation intensity and its lower ambient air temperature.

Instantaneous efficiency curves for various types of solar collectors (Source: after Sustainability Victoria with some changes)

In the above graph, parameters are defined by Sustainability Victoria as below:

Tm: Mean solar hot water temperature inside the collector

Ta: Ambient average air temperature

G: Solar irradiation intensity in W/m2

For Melbourne climate, the above parameters are quantified as below:

Tm: Mean solar hot water temperature inside the collector; 35C

[Water enters collectors at 15C from mains and exits at 65C from collectors, average= (15+60)/2=35C]

Ta: Ambient average air temperature: 15C

G: Solar irradiation intensity in W/m2: 400

[Referring to discussion under Solar Irradiation Resources from 8AM to 5PM we receive in average 400W/m2]

The value for horizontal axis: (tm-ta)/G = (35-15)/400=0.05 (m2C/W) or (m2K/W)

Figure below shows the value of 0.05 on horizontal axis extend vertically to calculate typical efficiency for flat plat collector and evacuated tubes. Evacuated tube achieves efficiency of 55% while the cheaper flat plate collector achieves efficiency of 62%.

Instantaneous efficiency comparison for flat plate collector and evacuated tubes in Zone 4 of Clean Energy Regulator, Melbourne (Geoflow Australia)

Apparently for climates like Sydney and Brisbane (zone3), Alice Springs (zone 2) and Rockhampton (Zone 1) there is more solar irradiation available and ambient temperature is closer to the mean solar hot water temperature which makes the value for the horizontal axis even smaller than 0.05 in the above picture which means flat plat collector are even more efficient in warmer climates in rest of Australia.

Savosolar flat plate collectors

Our Savosolar collectors are flat plate collectors and have Aluminium MPE absorbers which makes the most efficient flat plate collectors in Europe. Considering the comparison made between flat plate collectors and evacuated tubes, Savosolar collectors become the most efficient solar collector for Australian climate.

Large scale solar thermal farm
Savosolar actual absorber size compared to a person

Solar Radiation Resources

The amount of solar radiant energy incident on a surface per unit area and per unit time is called irradiance or insolation. The energy delivered by the sun is both intermittent and changes during the day and with the seasons.

The solar irradiation flux changes from place to place and some parts of globe receive much higher solar irradiance. Australia has one of the highest average solar radiation per square meter in the volrd (Geoscience Australia and ABARE, 2010). In Australia, about 200W/m2 solar irradiation is received on ground surface. When 200W/m2 is integrated over 1 year, the resulting 1500kWh/m2 that is incident on 1m2 at ground level is approximately the energy that can be extracted from 1.2 barrel of oil, 230kg of coal, 160m3 of natural gas.

C:\Users\Antec\Dropbox\GEOFLOW WEBSITE\Yearly sum of global horizontal irradiation, 1986-2005.png

 yearly sum of total solar irradiation o horizontal surface, Source [2]

 Figure below shows total solar irradiation on horizontal surface in some of Australian Cities during a year. Read more

Figure 14: Monthly total solar irradiation on horizontal surface for Australia (Melbourne, Sydney, Brisbane, Rockhampton and Darwin) – Source [3]

Figure below shows total solar irradiation on horizontal surface in some of New Zealand’ Cities during a year.

C:\Users\Antec\Dropbox\GEOFLOW WEBSITE\Monthly Solar Irradiation in New Zealand - Geoflow Australia.png

 Monthly total solar irradiation on horizontal surface for new Zealand (Auckland, Wellington, Christchurch, Invercargill)- Source iii

For Melbourne, hourly average for month data from “solar radiation data handbook” is presented in figure below and average irradiation in day time (just the figures presented below) shows that Melbourne gets in average 313W/m2 solar radiation from 5AM to 8PM when it is daytime and it gets in average 400W/m2 between 8AM and 5PM during the year.

 Average global hourly irradiance (W/m2) and daily irradiation (MJ/m2) on a horizontal surface in Melbourne

Optimum separation of solar collectors rows

While it is best to maximize the separation of rows of solar thermal collectors, Geoflow would like to minimize valuable land foot print of solar thermal system. Figure below shows the effect of solar collectors’ rows separation on amount of energy delivered by the solar thermal system with panel that are 2m tall at full standing position.

In case it is decided to install ground mount collectors, here the effect of separation on energy delivery and shading loss is assessed. Figure 17 shows variation of shaded solar irradiation and shading loss with change in separation of the solar collector rows. This is case study for 50 rows of collectors with 30 collectors per row and solar collector is 2.0m tall.

 Shading loss variation with change in collector row separation (2.0m tall solar collector)

Read more

More detail is presented in Table 1. With 3m separation loss is 11% and increasing separation to 4m, loss drops by 5%. Further increases drops the loss by less than 2%. Hence 4m spacing is ideal for this case. For 2.5m2 collector (2×1.25m), 4×1.25=5m2 land is required or for 1m2 collector, 2m2 land is required.

Table 1: Shading loss of solar hot water collector with change in separation of rows

Row separationQirr shaded (2m panel) kWh/annumPercentage of loss of solar irradiation

Pipework and flow rate

For copper piping, the pipe sizes and flow rate used should ensure that the maximum velocity is 3 m/sec. Refer to ‘AS/NZS 3500’ for flow rates and performance charts for pipe sizing.

Maximum benefit will be achieved in a low-flow system if the following load-matching principles are

incorporated (Gordon, 2001):

Flow in the collector loop in the range 0.2 to 0.4 L/(min ·m2 aperture area) or 0.0033 to 0.0066L/sm2 The lower margin is achieved to minimise heat loss in distribution pipes.

Flow into the storage tank is controlled to minimise mixing

We take the 14L/s as the design parameter for pipe sizing and design the pump for 20 L/s with VSD.

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Large Scale solar thermal design handbook by Sustainability Victoria, defines the minimum insulation for the solar hot water distribution pipes:

and thickness of insulation is defined as follows:

It is proposed that the flow and return line to be bundled to save on installation costs:

Hybrid geothermal and solar thermal

Most of the Victorian and Tasmanian houses and houses with swimming pool in other states are heating dominant. Almost 60% of Victorian energy bill covers high heating demands of the house and a small swimming pool operated only a few months a year can demand 2-5 times the house heating load. For heating dominant houses like above, Geoflow has implemented a new type of system to further increase efficiency and cost saving and reduce the capital cost of geothermal systems thanks to the federal subsidy on solar thermal panels.

While geothermal systems are the most efficient form of air conditioning [1], they require extra ground works to install ground loops which make them quite an expensive option. In order to make geothermal heating and cooling systems more affordable and more efficient, Geoflow has come up with a solution to minimize groundwork and ground loop total length. This is achieved via combining solar thermal collectors (Solar hot water collector) and geothermal ground loops

Read more


In a hybrid of geothermal and solar thermal system, solar heat is absorbed via hot water collectors and stored in a hot water tank (>700L) for diurnal use. The excess generated solar heat can then be transferred to the geothermal system to be stored in the ground for winter usage. Heat moves by temperature gradient and if water temperature inside the geothermal pipes is more than ambient ground temperature, heat will flow through geothermal pipes to the ground and stored in the ground thermal mass. The stored heat is extracted for night time use and directly fed to the building to satisfy heating demands when it is hotter than 40°C. During the winter season, the ground surrounding the geothermal pipes is warmer than natural ground which allows boosting the efficiency of the geothermal system to maximum possible levels allowed by current heat pump technology. Geoflow designs the hybrid of geothermal and solar thermal system with TRNSYS software which allows hourly modelling of both systems in a single model for accurately modelling the interaction of both systems for each hour of the year.

Depending on the geology and ground thermal properties of your building site, the ground can store 2000-3000 kJ/m3.°C. In Melbourne area, the top 50m ground temperature is 18.5°C[2] and ground temperature can be increased up to 50C safely. For Melbourne with moderately weathered mudstone bedrock, the maximum amount of energy that can be stored in a single 50m borehole is estimated to be 8500 kWh. [See calculation here]

2700kJ/m3C*(50-18.5)C*(3.14/4*3^2*50)m3/3600(kJ to kWh conversion) = 8500kWh.

Clicking on this line will allow the formulae to appear.

Note that a typical 200m2 new build 6-star house in Melbourne requires 6300kWh for annual heating and cooling requirements. [See calculation here]

200[m2]*31.5[kWh/m2]* = 6300kWh

Figure 19: Ground Mount Solar Thermal and Geothermal Hybrid

Figure 20: Roof Mount Solar Thermal and Geothermal Hybrid


  1. Space Conditioning: The Next Frontier, EPA 430-R-93-004
  2. Dr Amir Kivi, Ph.D. Thesis, 2015, University of Melbourne

Get an instant quote for the services that Geoflow Australia might be able to assist you with its range of consultation and installation services.

Solar thermal VS Solar Electricity

Solar is 80% and solar PV is 15%. This means the available roof area if used with Solar PV ca only provide

Your roof top area is a valuable asset that can be used to harness solar energy that can be up to 1kW per square meter of your roof top area. Solar energy can be harnessed in two major ways. As solar thermal heat that can be install solar electricity panels or solar thermal panels. Which one is most cost effective and suits Victorian demand

Solar Thermal and Geothermal storage VS Solar PV and battery storage

Solar thermal and geothermal works like solar PV and battery system except that battery dies in 10 years and geothermal has an indefinite life expectancy. Also, solar PV can take up to 180 Watts of power and solar thermal can absorb 600 Watts of heat. Solar thermal and geothermal also costs a fraction of solar PV and battery. Below is a comparison of solar PV and battery and Solar thermal and geothermal.

Solar PV / Solar Electricity

Solar thermal collectors are used to heat water for domestic hot water production and space heating and cooling applications while Solar PV panels or solar electricity panels are used to convert sunlight to electricity. Solar PV panels based on crystalline and polycrystalline silicon solar cells are the most common. Most panels available in the market have efficiencies of the order of 15%. The price of PV panels came down from about US$ 30/W about 30 years ago to about US$ 1/W now. Efficiency of solar PV panels are evaluated based on a standard flux of about 1000 W/m2, which is approximately the solar radiation incident on a surface directly facing the sun on a clear day around noon. Consequently, solar systems are rated in terms of peak watts (output under a 1 kW/m2 illumination)

Fossil Fuels

Energy content and emission factor from different types of fuels.

The Australian National Greenhouse Accounts (August 2016) is published by the Australian Government and provides the energy content and emission intensity of different fuels. Savosolar has used this data to compare different sources of fuel used commonly for heating in industrial process and greenhouses.

Read more

Energy and emission intensities vary significantly for different types of energy and fuel sources. For instance, for the same heat output, the GHG emissions from natural gas may be only 55% of coal. The GHG emissions from electricity generation can also vary from location to location, depending on the fuel sources being used to generate electricity.

By switching energy source, it is possible to significantly reduce both the energy cost and environmental pollution.

Discussion on Specifics of Energy Demand

In this section of website, the demand pattern from different energy users from residential to different types of commercial are discussed.


Average household energy bill beak down

Note that based on a report by Energy Consult July 2015 (energy, 23% of average household energy bill is for hot water heating and this option of geothermal system can save considerable amount of energy consumption and the associated costs.


For cost effective and efficient geothermal heating and cooling design and installation and other sustainable domestic and residential energies, please check out our services website and contact us.

Swimming Pool Spa Heat Demand

Heat losses from swimming pools occur mainly from the water surface and various types of cover are available to reduce these losses in both indoor and outdoor pools. Solar pool covers should be regarded as a useful energy conservation measure with any type of pool and most will enable pools to function more efficiently as natural collectors of solar radiation, provided evaporation from the surface is minimized.

Various types of floating pool cover can be used including the following types:

  • Double-skin plastics film with encapsulated air bubbles.
  • Single-skin plastics film.
  • Closed-cell plastics foam, laminated to a reinforcing sheet of film or fabric.

Read more

Covers are moved on and off the pool many times each season. Any pool cover should be sufficiently tough to allow necessary handling. Materials used for covers for open air pools should be adequately resistant to both ultraviolet radiation and to chemicals normally present in swimming pools.

The main function of a cover is to reduce or eliminate evaporation from the surface of the pool. Floating covers of the types mentioned above are effective in this respect since they form a vapour barrier across the top surface of the pool. Any water lying on the top of the cover will reduce its effectiveness. The thermal benefits of using a floating cover may be significantly reduced during periods of high rainfall. With covers that are suspended above the water it is important to ensure that the edges are reasonably airtight since otherwise water vapour will escape.

Another function of the cover is to reduce heat loss by convection. Sunlight that passes through the cover is largely absorbed by the pool water itself. The water can thus be heated naturally in the same way as with an uncovered pool but with the great advantage that the heat losses from the top surface are substantially reduced. It has generally been found that the use of a translucent pool cover is a cost effective option for an outdoor pool either in its own right or in conjunction with a solar pool heating system.

There are some other benefits of covers also worthy of note, namely reduced chemical consumption on all pools, reduced fouling by leaves, etc on outdoor pools and reduced condensation and odour problems on indoor pools. Safety is an important consideration as pool covers generally cannot support the weight of a child or pet animal. Due to the risk of drowning, no one should swim beneath a cover. This is particularly important with floating covers.

Calculation monthly heat loss from different mechanisms are presented in Figure 26 together with solar heat gain. As it can be seen in this picture heat solar heat gain is a major source of energy for the pool. Daily new heat losses are presented

Monthly heat loss/gain from different mechanisms for total Spa surface area

Figure shows the frequency of heat loss values which is used for peak load selection and sizing heat source to math 99% of the loads requirement.

Heat demand for green houses

Globally, agriculture is a major source of energy consumption and therefore greenhouse gas (GHG)

emissions. Nurseries/green houses are one of the most energy intensive froms of agricultrue. Australia is currently the highest per-capita greenhouse gas (GHG) emitting country (24.3t CO2e/person) in the world. The Australian agricultural sector accounts for 15% of our national GHG emissions and is

the second largest source of emissions (DCCEE, 2012). Based on a study by (Smith et al. 2008), this proportion is significantly higher than Central and Eastern Europe (3%), the former Soviet Union (3%), and the USA (5.5%).

In order to reduce GHG emissions, the Australian Government in 2010 implemented the

carbon trading scheme, entitled a “Carbon Pollution Reduction Scheme” (Department of Climate

Change, 2008). This was abolished by the Government in 2014, which instead proposed a

Direct Action Plan and allocated $2.55 billion for this purpose (Australian Government, 2014). With

this plan, the government expects agriculture to contribute to Australia’s unconditional national target

of a 5% reduction in GHG emissions by 2020 (Department of Environment, 2014).

Savosolar collects large data base of energy performance from different nurseries around the globe with crop and climate close to Australia. Although these data cannot be used directly to compare with your greenhouse energy use, it can provide indicative data as energy performance benchmark. Here in this article some of this data is presented in tables below.

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Horticulture energy performance data from global published literature

CropDirect Energy intensity (MJ/m2)SourceCountry
Greenhouse Flowers20000Vox (2010)[4]Italy
Greenhouse Tomato10000-20000CAE (1996)[5]NZ
Greenhouse Tomato25.2Albright & de Villiers (2008)[6]USA
Greenhouse Tomato53.4Hatirli et al. (2006)[7]Turkey
Greenhouse Flowers1237 MJ/m2Geolflow Australia (2017)Victoria, Australia
Greenhouse Flowers1,210 MJ/m2Barber, 2004[8]North Island, New Zealand
Greenhouse Flowers1,830 MJ/m2Barber, 2004[9]South Island, New Zealand

Barber, 2004[10] surveyed 133 heated greenhouses in North Island New Zealand and 63 heated greenhouse in South Island New Zealand and reported energy intensity by region and crop type which Savosolar has summarised in the below table. It is concluded that roses are consistently the most energy intensive crop. Energy use is very strongly influenced by management practice, regional location, the type and age of greenhouse and type of crop being grown. Generally, smaller operations were less energy intensive, possibly due to capital constraints.

Table 2: Energy intensity (MJ/m2) by Region and Crop type

New Zealand North Island is almost at the same latitude of site location (north Island 39.2378° S vs Melbourne 37.8° S) and has a mean annual average temperature of 15C which is close to 14C in Melbourne. Energy performance data from flower growers in North Island can be used to compare the energy performance of the green houses in Victoria and Tasmania with high energy intensity.

Residential passive house modelling

Passive Solar Design

We defines passive house as a house that requires cost effectively, minimum amount of mechanical heating or cooling. Homes that are passively designed take advantage of natural climate to maintain thermal comfort. 


With passive solar design we try to limit the heat gains in summer and heat losses in winter through climate sensitive design of building envelope. A house built using passive solar design principles will generally be much less reliant on artificial heating and cooling and will therefore use less energy and cost less to run. Passive house design is essential for houses that are planned to be off grid. Lowering building demand allowing to lower the capital investment on solar electricity and battery and solar thermal heating/cooling and hot water storage tanks. 


The key principles of passive solar design (with the correct order) are as follows: 

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1- Orientation and siting

2- Zoning and layout

3- Thermal mass

4- Common building elements, such as walls, floors and roofs

5- Floor type and materials

6- Windows and glazing

7- Shading, including use of eaves

8- Convection and ventilation

9- Insulation

10- Landscaping and vegetation.


Note for the order of different principles above as it is the key for a cost effective passive house design. Home owners don’t need to invest several tens of thousands on excessive and unnecessary insulation where a proper modelling and design can reveal cheaper options to better take advantage of natural climate at lower installation costs. 


At GeoFlow Australia, we use TRNSYS software to model all building’s thermal details in 3D. TRNSYS is the most advanced thermal modelling software that is used in industry and research for implementation of new innovative energy systems. Modelling in 3D allows to consider almost all the details for the building thermal modelling. It also minimizes errors in modelling as you can see the building in 3D and compare it with architect’s plans. Neighbouring buildings and objects can be exactly modelled and shading effects can be assessed for any time of the year. Internal heat gains by occupants and schedule of operation can be modelled as requested by home owners every details. The most important final output of modelling is hourly building heating and cooling demand and electricity/gas/hot water consumption. 


At Geoflow we want to achieve lowest building energy demand with cheapest energy efficiency options. For instance we won’t consider triple glazing with aluminium frame and thermal break where a double glazed UPVC window can deliver similar saving at half the cost. We model different energy efficiency options and assess annual hourly building loads and savings for each option and let the architects/builders/home owners decide based on annual cost saving which options they want to take. 


Because the climate varies so much across Australia, passive design is not a single set of strategies all of which are applied equally in every house and climate. For instance higher shading is desirable in warmer climate where it can lead up to increased annual demand in mild and cool temperate. Same applies on different types of glazing. Warm climates should minimize heat gain from glazing where in cool temperate different type of glazing are used to increase solar heat gain during the day. At Geoflow, we use appropriate strategies in our modelling to take into account the climate and specifics of the site to minimize the heating and cooling requirements of the building, cost of running the building and consequently the carbon footprints of the building.


In the following summary of key points for different passive house design principles are discussed. 


Co-benefit of hourly energy modelling

The co-benefit of GeoFlow’s passive solar modelling is to use data from passive house modelling to design your renewable energy system. Sometimes, for some people this co-benefit becomes the major focus. One of the key outputs of GeoFlow’s energy modelling is hourly energy outputs. These hourly outputs can be used to find peak demand, annual total heating/cooling demand, annual total electricity to run appliances and annual total hot water demand. The software can also show any heat loss/gain from any part of building envelope like window, walls, etc., for any time of the year which comes handy when comparing options like different glazing from different manufacturers. 

Output of building thermal modelling – hourly heating and cooling for the building

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These hourly outputs are the key for proper design of renewable energy system as source of energy. With conventional energy sources like grid electricity, split heating, gas heating, etc, annual demand is not a design factor as they are unlimitedly available as long as you pay for the bills. However, with renewable energy generation for yourself, it is important to know hourly and annual demand for energy to be generated to cost-effectively spend the available capital. Renewable energy generation system for your house includes but not limited to solar electricity, battery storage, geothermal and solar thermal heating/cooling. Oversizing and wrong design, could cost a lot of capital investment which could have been used more cost effectively. 


TRNSYS software allows to model almost any energy source system like geothermal, solar electricity and solar hot water to be designed for best satisfaction of the building demand for every hour of the year. In other word, our passive solar design enables us to use data from passive house modelling to use for your solar hot water and electricity generation and storage design. 



Geoflow Modeling Software

Here description of modelling tools used by Geoflow are presented so our clients can rest assured that we don’t use rules of thumb at cost of our clients.

TRNSYS Software for 3D building thermal modelling

We use TRNSYS 3D building modelling which allows to draw multizone building with considering thermal mass, self-shading, external shading and internal view factors for radiation exchange. The data we need for modelling is the building plans, elevations and specifications if they are available.

TRNSYS is the most comprehensive suite of tools that allows modelling the building, geothermal heating and cooling, solar electricity, solar thermal and any other thermal phenomena in a single model and assess interaction of different systems on each other.

 3D simulation with TRNSYS

6-Star Energy Bands

According to the NatHERS star rating protocol, star bands are introduced for NatHERS building modelling approach to assign star rating for residential buildings. Figure below represents the star bands for 67 different cities in Australia. For instance Melbourne is called climate region 21 and to achieve 6 star rating, building must not consume more than 114 MJ/m2 or 31.6kWh/m2. In other words, theoretically, a 200m2 6-star building in Melbourne annual heating and cooling energy demand shall be about 200*31.6kWh/m2= 6320 kWh.

The below star bands (hyperlink to star band figure) are valid for a house of 200m2. For smaller or bigger houses, the star rating is adjusted to consider surface area of the house. For bigger houses, this adjustment is like a fixed penalty for house star rating regardless of quality of building thermal fabric.

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NatHERS Star bands (Source: FirstRate5 Software manual, page 16, published Jan 2015)

 Star rating adjustment with building foot print area