Geothermal heating & Heat Pumps has become a growing trend as we chase for more and more efficient heating systems.

The move away from Gas boilers towards different heat pump technologies is becoming more and more common. however, many pool owners are still seeking even more efficient systems in the aim to reduce the almost unstoppable running cost and rise in power pricing.

Heat pumps literally save hundreds or even thousands in running costs and reduced greenhouse gasses over their gas counterparts. And with a 1 to 3 year payback, they are becoming systems that pay for themselves.

However, since heat pumps rely on ambient temperatures for their efficiency, and some climates lack the warm for an all year long successful air sourced heat pumps efficient use. Many people are looking at successful European heat pump technologies. “Geothermal heating”.

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The heat energy air- sourced heat pumps use comes from the ambient air temperature, which is dictated by the amount of solar heat it gains on a daily and seasonal basis. However, this heat is fleeting as seasons change and the day becomes night.

The same heating occurs within the ground. Solar heat is also absorbed by the ground. But the ground holds onto this heat for a much longer time. And at depths of 2 to 3 metres this heat becomes quite stable all year long.

Geothermal heating heat pumps tap into this heat by the use of circulating water loops. This abundant heat will remain constant for most of the year and will vary from 14 degrees in Tasmania to over 18 degrees in Sydney right up to 23 degrees in Darwin.

Many systems also take on the advantage that the ground absorbs heat, and they can use the earth as a heat sink for air-conditions in summer and heaters in winter. A natural storage, energy capture and reuse solution. Thus you create a heating and cooling system.

Places like Tasmania and Canberra where summers can be warm, but winter more like European climate conditions, it is easy to see that operating at 18 degrees Celsius would well out perform any air source heat pump operating at 5 degrees Celsius or lower.

Geothermal systems require either vertical or horizontal laying of water pipes. Horizontal pipe systems are usually lower cost to establish, but only suitable for properties with large exposed areas of ground.  I have seen these system built under tennis courts.

Where space is lacking vertical pipes are used. A large drilling machine is used to dig holes straight down and can be for 10 to 20 meter deep. The number of holes all depends on the heat requirement required. So accurate system sizing is required, to prevent requiring additional holes dug later.

Images from Oldhouse Online: An article on Geothermal systems for older houses.

Australia is unique in that it has a very wide variety of climate zones. From the hot and humid northern regions to the  alpine temperate areas of the south. Because of this diversity in Australian climates geothermal heating is not ideal across all of Australia, and geothermal cooling is likewise not suitable across all of Australia.  Some areas only suit one or the other, but there are areas that suit both.

Geothermal heating use for home, pool and spa use, although can be used right across Australia, is generally only suitable where there are a significant quantity of cold months as compared to warmer months. Thus selected zones for low grade geothermal use are restricted to the Southern part of Australia, and more along the coastal regions (In blue and green in image below).

Australian energy companies consider that most of Australia has Low-Grade Geothermal potential, with a few “Hot” Spots. These hot spots are used for electricity generation and can provide significant energy for the process.  They are normally up to 5km under the ground.

Most residential zones are located in poorer low grade locations, and digging is restricted to a few meters to 100 meters under the ground. This means the average ground temperatures available are approximately an average between summer and winter ambient temperatures.

• Locations where winter temperatures can drop below 5C over 4 to 6 months or more. I.e. in the mountains, Canberra etc. This may bring geothermal as a real option for consideration as the need for sustained efficiency is required.
• Implant or indoor heat pumps can provide similar ambient conditions to a Geothermal system, if installed correctly.

In Australia where the ambient does not go below 20 degrees, for most of the year, will actually gain little advantage of a Geothermal heating system so care should be taken to prevent excess unnecessary cost.

This means that you have to significantly look at your local ambient conditions verses your ground temperatures available.

• For Example in Sydney we would have 6 months warmer ambient than the ground, about 2 months the same and only 4 months lower than the ground temperature.
• Toyesi Heat Pump are designed with a target COP of around 5 at 15 C to 18 C. This means for around 8 months of the year they will be equal to or better than a Geothermal sourced heat pump.
• A decision has to be made if the 4 winter months are worth the added expense of installing Geothermal pipes under the ground.

Apart from potential ground temperatures to be considered, you must also do a soil survey prior to digging for geothermal loops. The main reason is the thermal conductivity of the soil is critical to success of a geothermal system. Dense clay, moist soil, wet sand and underground aquifers work best for geothermal heating and cooling. However dry soils, rocks, and dry clay or sandy beds can be very poor for heat transfer.

Other areas that need considering:

1. Depth to bedrock – A real limiting factor for geothermal heat pumps
2. Digging past bedrock – very expensive process.
3. Depth of and to Desnic Material – A layer that restricts water movement through the soil. However these areas are ideal for surface geothermal pipe laying.
4. Depth to water table –  The closer to the water table you can be the better a geothermal heat transfer will be.
5. Soil moisture content – moist soils are a far better heat transfer medium.

Horizontal pipe work is a far more cost effective system, but sometimes you have no choice but to dig vertically.

You must do your due diligence and do your ambient verse ground temperature analysis, Soil survey, and have decided for a surface (horizontal) or a vertical drop hole system. You have also looked at both open loop and closed loop options and benefits for your area.

I know it is a lot to do, sounds complicated, but these steps are essential for a successful greener solution and to ensure positive outcomes.

Geothermal heating and cooling systems form a very green option for consideration. With winter savings for heating projects, and summer savings for cooling projects, or even all year heating or cooling, geothermal systems offer a unique and consistent energy levels and balanced heat loads and running costs.

Geothermal systems because of the increased stability in running costs also allows for better budgeting and will usually have a 5 to 10 year payback period. the installation costs will be the big determining factor on the payback period. However once you see the reduced monthly running costs you will soon be  happy with your Green energy choice and on going savings.

Geothermal heating systems are extremely efficient during the winter months and significantly improves the COP of a heat pump during a time where air-based heat pumps may struggle to compete. However as you have learnt in warmer months air-source heat pumps will out perform a geothermal system for heating COP and efficiency.

We have seen in many projects where people have tried to be energy efficient all year round  have considered purchasing both an Air-sourced heat pump for summer use, and a Geothermal system for winter use.

The two systems working hand in hand produce a far greener solution and significantly reduces running costs all year round.

Purchasing two systems adds more capital equipment expense, and often requires either manual switching or BMS systems to swap between systems at the right time or they end up competing with each other..

To over come these additional costs and control systems we developed the Geo-Hybrid. A system that combines both geo-ground source heat pump with an air-sourced heap pump in a single unit.

The Toyesi Geothermal Transthermal system or Geo-Hybrid is a system that combines both geo-ground source heat pump with an air-sourced heap pump in a single unit.

Utilising our Smart Transthermal technology we monitor both the ground water temperature and ambient temperatures and switch between them. This Smart technology means that you gain the most efficient system possible at any given time of the year.

Rather than buying two independent systems that require either manual operation or a BMS system to operate, the Geo-Hybrid performs minute by minute calculations to determine the most efficient heat source available. It can also be set to do quiet Geo by night and air-source by day. The control is yours. The Green & Greener solution all in one system.

– Increased Efficiency, Lower Running Costs, Flexibility, Transthermal  – The greener choice.

Sample collection of Toyesi & Trident Heat Pumps and Chillers..

If you want to now how Toyesi can help you and your water or pool heating project increase energy efficiency, reduce running costs or minimise your waste energy then give us a call.

Contact us on Facebook, phone: 02  9679 9400 or by email info@toyesi.com.au and we can discuss how we can best assist you in your projects. Alternatively download a company brochure