Water to Water & Ground Sourced Heat Pumps

Using the Ground as
a Heat Source

When looking at being “Green” and managing our “Energy Usage” we turn to heat pumps due to their overriding benefits over gas and other heating options.

Heat pumps come in a couple of formats:

  • Air-Sourced – Draws energy from, or rejects energy into the air.
  • Ground-Sourced – Draws energy from or rejects energy into the ground
  • Geo-Hybrid – A duel system that monitors both air and ground temperatures and draws or rejects energy into the best option at he time of need.

Geothermal Heat Pumps Versus Air-Sourced Heat Pumps

Geothermal Heat pumps and Air-Source Heat Pumps are quickly gaining popularity for efficient, eco-friendly heating. Their efficiencies and cost savings of traditional Gas and Oil furnaces are well documented and recognised. With savings from 40% to 70% over the traditional methods allows for relatively short pay-back periods.

Heat Transfer Theory

Heat Transfer theory rests on the principle that heat will move from a higher temperature to a lower temperature. Hence, if a heat transfer coil can be kept at a lower temperature than its surrounds, it will absorb heat

Air-Sourced Heat Pumps Explained

Toyesi air-source heat pumps captures heat from the surrounding air by drawing it through a refrigerant cooled lower temperature finned tube type heat exchanger.

The ambient heat absorbed by the low temperature refrigerant gas circulating in the system, where its temperature is increased by a vapour-compression process and by absorbing the motor winding’s heat of the compressor.

air sourced heat pump - Product Information - Geothermal

The heat of the high temperature refrigerant gas is them transferred to the circulating pool water (or other water body) via a tube-in-tube “refrigerant to water” heat exchanger.

The performance of an Air Heat Pump is directly relational to the ambient air temperature during its operating period and will vary from day to night as well can be seasonal.  In-door units are more favourable in cooler climate locations.

Geothermal Heat Pumps Explained

The principle of a geothermal or ground heat pump is based on the working methodology of an air sourced heat pump. However, rather than using air as the source for heat exchange the geothermal system the heat-energy stored within the earth via the use of horizontal or vertical ground loops. These loops can require extensive excavation for their installation.

The solar energy reaching the ground is the renewable energy source of geothermal systems. Usually in depths greater that 2 to 3 meters provide a stable temperature environment that is the approximate equivalent of the average annual air temperature for that location. In general, the performance of a geothermal system is directly relational to the ground temperatures.

The approximate ground temperature in Sydney and Perth is approximately 16-18oC, Adelaide, Melbourne and Canberra is approximately 15-17oC, whilst in Brisbane it is 22-23oC.  In contrast, Darwin has a ground temperature of approximately 31oC and Hobart approximately 14oC.  (Source Australian Bureau of Meteorology)

installing a gerothermal system - Product Information - Geothermal
Installing a Toyesi Water to Water Geothermal System

Geothermal & Air-Source System Considerations:

air to geo considerations - Product Information - Geothermal

Sample Project Considerations

The following project summaries are based on a Sydney located, standard Indoor Pool 20m x 5.5m x 1.3m @ 28oC requiring 50kW of heating at peak use in midwinter.  Pricing are only estimated based on potential options and set ups and nominal conditions, they will vary project to project, depending on exact project requirements.

This following example is an extract from a report presented to a major client.

Geothermal & Air-Source System Cost Comparisons

cost comparison - Product Information - Geothermal

Geothermal & Air-Source System Estimated Running Cost Comparisons

running cost comparison - Product Information - Geothermal

Geothermal & Air-Source System Performance Charts

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performace chart 2 - Product Information - Geothermal
performace chart 3 - Product Information - Geothermal

Conclusion & Summary

Geothermal systems if designed correctly can produce effective and predictable heating and cooling solutions all year round, 24 hours and 7 day a week.  They do not suffer huge changes in efficiency and do offer greatly reduce running cost potential.

However, care must be taken to correctly analyse the soil and ground to ensure correct sizing of the ground loops to prevent super freezing and collateral damage of structural substrates and building.

If ground super-freezing does occur then the performance of the geothermal system will significantly drop off. With little way to warm the ground either by reversing the system or just waiting for nature to replenish the ground heat. Underwater aquafers and moving water tables can help alleviate this issue as they help balance the heat load of the ground.

Therefore, it is recommended to use geothermal alternate between heating and cooling on a seasonal basis, rather in a constant single use system.

geo set up - Product Information - Geothermal
Image Source Unknown

Air-sourced heat pumps also run efficiently all year round, however are very prone to changes in air temperature. To alleviate these issues indoor units are recommended (especially in very cold areas). Insulated rooms assist greatly in this process.

The cold air discharge must be ducted away to prevent cold air recirculating and causing unit freeze ups. If the rooms are designed well enough they can have the same consistent performance of a geothermal installation, but without the huge ground loop expense.  If an air-source heat pump is sized for the coldest use period, it should not fall over and provide heating all year round.

Either of the systems can provide significant running cost savings and help free up valuable cash flow for other projects.

Hybrid Geothermal Heat Pumps

Many Hybrid Geothermal Systems use cooling towers, water storage, and other systems to eject heat into the ground over summer, like an energy bank, for use over winter. Thus using very cleaver design is to reduce the amount of holes or geothermal circuits required for a given project. This greatly reduces set up costs of geothermal systems.

However, Toyesi is working on a very cleaver Hybrid Geothermal Heat Pump. This system will use our developed Smart Transthermal technologies to hand shake between a Water to water geothermal heat pump and an air sourced heat pump in a single unit.

Using the Transthermal technology will allow for not only temperature monitoring to draw on either the ambient or geothermal source for maximum efficiencies, but also energy handshaking between the two to allow for standard geothermal energy boosting and storage of excess heat.

This system should provide far greater efficiency and improved environmentally green solution for the more astute builder or pool owner.

For more on this system either contact us direct or Peter Buck (details below)

Contact an industry expert.

geotec logo red 600x163 - Product Information - Geothermal

Geoexchange Technologies Pty Ltd (Geo-Tec) provides a range of services to the ground sourced energy heating and cooling market, specialising in the heat exchanger component constructed outside of the building. We can offer advice and services to individual developers or building services engineers considering geothermal technology. Our services range from initial feasibility desk-top studies for ground heat exchanger installations to complete design-construct projects. Geo-Tec are heat pump manufacturer independent, that is, we focus on the single most important factor affecting the heat pump performance; the earth.

With the trends in environmental legislation designed to encourage developers to incorporate new “green” technologies and innovative sources of energy into their projects, ground source heating and cooling is at the forefront of these technologies. Ground heat exchange (geoexchange) technology is not new. While the basic technology has been around for more than fifty years, many improvements recently have been made including types of materials used, design and installation methods, and the efficiencies of compressors, pumps and associated Toyesi Geothermal Heat Pumps & equipment.

Peter Buck
Geoexchange Technologies (Geotec Drilling)
PO Box 609, COMO 6952 Perth Western Australia
Tel: +618 93679454
Mob: 0409367945

Want to know more Contact us.

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Toyesi Pty Ltd. Services & Solutions

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