The ground array system is one of the most important aspects of ground source heat pump installation. It is crucial that the ground array system is sized and installed correctly. They are typically the most expensive element to install when installing ground source heat pumps. In the UK, the ground array system is either a horizontal array that uses straight pipes in trenches or a vertical array that uses U-tubes inserted into boreholes.
The design and installation of the ground array system are crucial to the success of the operation of the ground source heat pump. In fact, the ground array supplies the required energy to heat the building. You may invest in the latest ground source heat pump on the market, but if the ground array system isn’t installed properly, you won’t get any heat. This article provides information on the effective ground array installation.
Ground source heat pumps use renewable energy from the ground in order to provide a low-cost as well as a low-carbon form of heat to heat your buildings. The heat pump would absorb energy from the ground via ground arrays or buried heat exchange devices. The temperature of the ground is almost constant all year round. In fact, the ground temperature is at around 8-12C throughout the year. It’s a great energy source for ground heat pumps. The ground will absorb solar energy by means of sunlight and rain. The energy isn’t infinite because the ground acts like a battery that needs to be recharged by the sun and rain. That’s why incorrectly sized and designed ground array systems lead to much lower outputs from ground source heat pumps. That’s why a water antifreeze is usually circulated around the ground array system to transfer the energy from the ground to the heat pump. Ground array systems come in a wide variety of designs and types.
Contents
Key Takeaways:
- The ground array system is a crucial component of ground source heat pump installation and significantly impacts its efficiency and effectiveness.
- There are various types of ground array systems, including slinky pipes, straight pipes, boreholes, and water systems, each with advantages and cost considerations.
- The sizing of ground array systems varies based on the type, with slinkies requiring approximately 10 meters of trench per 1 kW of heat, boreholes offering higher energy yield per meter, and water sources providing around 7 kW per pond mat.
Types Of Ground Arrays
Slinky Pipes
Slinkies significantly reduce the amount of digging involved when installing ground arrays. Hence, they are one of the most cost-effective types of ground arrays. Slinky pipes were developed by the University Of Oklahoma. They are some of the best heat sources for heat pumps in the United Kingdom today. A slinky pipe is a length of plastic coiled pipe buried in the ground with the use of a digger. They are installed horizontally or vertically. Due to the efficiency and low-cost, slinky pipe ground arrays are some of the most recommended in the United Kingdom.
Straight Pipes
Straight pipe ground array systems are also popular in the United Kingdom. But this system will increase the amount of digging by up to 5 times when compared to slinky pipes. The cost of installation is much higher than slinky pipes. In fact, slinky pipes and straight pipes have the same level of performance. Heat pumps can operate with both these ground array installation systems. But due to the lower cost, slinky pipes are recommended for a ground source heat pump.
Boreholes
Boreholes are the alternative to both slinkies and straight pipes. When there isn’t enough space to install slinkies and straight pipes on the ground, boreholes are the solution. Boreholes are installed by digging vertically down. They tend to be 60-100m deep and consist of a single looped pipe within the borehole. The borehole is normally filled with thermal grout. The number of boreholes required and their depth will depend on the condition of the ground where the digging is done. Borehole installation should be done by a professional installer. Hence, it is considered an expensive alternative.
Water Systems
If your property is located near a lake, lake water can be used as an energy source. The digging is kept to a minimum when installing this system. Hence, it is cost-effective and viable compared to most of the other systems. Water systems can be open source or closed source. The closed-loop system is the most popular in this regard.
Sizing Of Ground Array Systems
Slinky Array
The amount of sunlight that lands on the ground (per square metre) is almost similar anywhere in the United Kingdom. The amount of energy available for heat absorption doesn’t depend on the soil type. In fact, wet soil is ideal compared to well-drained soil in this regard. The sizing of slinkies doesn’t consider the soil type. The moisture content of the soil can affect heat transfer rates. The formula is to use 10 metres of trench to provide 1 kW of heat from the heat pump.
Boreholes Array
Boreholes arrays offer a higher energy yield per metre of array compared to other systems. A borehole can provide between 30W/m and 50W/m of energy to operate the heat pump.
Water Source Array
Water is an ideal source of energy for heat pumps. It has a higher conductivity compared to other systems. The energy extraction rate is usually about 7kW per pond mat.
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Conclusion
Properly designing and installing a ground array system is pivotal to successfully operating ground source heat pumps. Choosing the right ground array type and sizing it correctly can significantly impact energy efficiency and cost-effectiveness. Whether opting for slinky pipes, straight pipes, boreholes, or water systems, understanding their advantages and considering the unique characteristics of each system is essential. By making informed choices in ground array installation, you can effectively harness renewable energy from the ground and enjoy the benefits of a low-cost, low-carbon heating solution for your buildings.
About the Author
At Heat Pump Source, our articles are the product of a collaborative effort among a team of highly skilled HVAC experts. Our dedicated professionals, hailing from diverse backgrounds in heating, ventilation, air conditioning, and refrigeration, contribute their extensive knowledge and experience to every piece of content. This multidisciplinary approach ensures comprehensive coverage. Our commitment is to deliver authoritative, reliable, and tailored advice to meet the unique needs of every household and business across the UK.