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Blog Article

Extend your natural grass season with Capillary Geothermal

Editorial Team
Extend your natural grass season with Capillary Geothermal
November 17, 2023

Gothenburg, Sweden

Shallow geothermal energy systems, commonly known as ground-source heat pumps, have been in use for various applications since the 1940s, gaining significant popularity, especially since the 1970s. Traditionally, these systems have primarily been utilized to heat and cool buildings. The mechanism behind these systems is based on the sensitivity of the earth's surface layer to the sun and cold weather. As the seasons change, the temperature in the shallow ground gradually increases during summer and decreases during winter. Depending on the location and specific ground conditions, including soil type and shading levels, there can be a temperature difference of 10°C or more between the ground and the air above during different seasons. Ground-source heat pumps capitalize on this temperature differential to efficiently extract heat from the ground for heating during winter. Similarly, in the summer, they use the cooler temperatures deeper in the ground to lower the temperature of the ground just below the surface. This sustainable and energy-efficient solution offers effective climate control for buildings.

But despite having been used for several decades, the potential of harnessing these shallow geothermal systems to regulate grass growth in sports fields, equestrian grounds, and golf courses remained largely unexplored until now.

Introducing Capillary Geothermal

CapillaryFlow’s Capillary Geothermal system moderates the subsurface temperatures of golf greens, sports fields and equestrian arenas using geothermal technology, thus ensuring the robust growth of grass in extreme environments.

Surface-level ground conditions can be harshly affected by the sun and weather, which can cause major temperature fluctuations. However, one metre beneath the ground's surface, these changes occur more gradually. Capillary Geothermal takes advantage of this temperature stability. In the winter, it utilizes the thermal energy stored about one meter deep in the ground to warm the irrigation water, which, in turn, increases the temperature of the growing medium, the sand. And in the summer, it uses the cold stored about 1 meter underground to cool the irrigation water, thereby reducing the temperature of the rootzone, the sand, ensuring both a firmer and drier playing surface but first and foremost optimizing the growing conditions for grass. Importantly, this process relies solely on the moderate temperatures within the subsoil, demanding no additional energy beyond that required for water circulation via an air-lift pump.

Before we proceed to explain how exactly the system works, here’s a caveat: It only makes sense to install Capillary Geothermal in locations where there are large fluctuations in air temperature between the summer and winter. The system will not be as effective in regions with a relatively stable year-round climate where the temperature doesn't vary significantly between summer and winter.

Capillary Geothermal and Capillary Hydroponics

The CapillaryFlow Geothermal system operates in conjunction with Capillary Hydroponics. So, it is necessary to first understand how Capillary Hydroponics works.

Capillary Hydroponics is an innovative irrigation system that uses an oxygenated and fertilized moving underground water table to grow turfgrass. In doing so, it decreases water evaporation and consumption by up to 85% while ensuring that the turfgrass grown is stronger and more durable with significantly less maintenance and environmental impact.

At the core of Capillary Hydroponics is Capillary Material, formerly known as Capillary Concrete. This patented and engineered polymer-based material is the only building material that can rapidly drain water while also moving water up. It ensures a perfectly flat and level base beneath the rootzone, which is crucial for the functioning of a hydroponic system. Invented in 2009, it is also behind one of CapillaryFlow’s most successful solutions, Capillary Bunkers, which has transformed the way the golf industry constructs and maintains bunkers.

The Capillary Hydroponics system comprises several layers: an impermeable liner that sits on a cavity in the soil, drainage pipes, drainage gravel, a layer of Capillary Material, washed sand and finally grass.

The cavity is split into two equal parts. A control basin filled with water is placed on the outside and has pipes that feed into the middle of each cavity. It automatically oxygenates and pumps fertilized water back and forth between the two sections several times a day, watering the roots as it goes. When the water moves and enters or exits the pores of the root-zone material, the gas exchange increases by up to 6,000%.

The level of the moving water table is completely controllable and the water moves between each cavity at a fully adjustable rate too. This system minimizes the amount of water required and promotes strong root growth.

System overview

Win-win with Capillary Geothermal?

Geothermal systems are usually closed. But the Capillary Geothermal system is integrated with the Capillary Hydroponic system. And as water is pumped from one side of the turfgrass area to the other via the hydroponic system, it is routed through a network of 40-mm thin-walled geothermal pipes buried at a depth of 1 meter beneath the surface, optimizing temperature control. The speed of this circulation influences the heat exchange, and is easily controlled through the app that also governs the hydroponic system.

In the winter, Capillary Geothermal reduces winter damage and extends the grass season with geothermal heating. This integration of the hydroponic subsurface irrigation system with the geothermal system promotes rapid grass germination and year-round growth, ensuring robust grass performance and vibrant winter color. Similarly, in the summer, it prevents heat stress on the grass by cooling the rootzone through subsurface irrigation.

Capillary Geothermal offers adaptability, with the option to extend pipe lengths, allowing for tailored heat exchange. The integrated app simplifies operation for straightforward control while the system’s mechanical components ensure hassle-free maintenance and reliability. From an energy perspective, Capillary Geothermal is incredibly efficient, consuming only approximately 50-75 kWh per watering cycle. This efficiency reduces operational costs and environmental impact.

Key advantages

To recap, Capillary Hydroponics and Capillary Geothermal enhance sports ground performance, ensuring optimal playing conditions, and year-round grass growth. Their key advantages are:

  • Robust grass growth even in cooler seasons: The combination of a hydroponic system with subsurface irrigation and heating accelerates germination and growth. This means that your sports grounds can achieve rapid and year-round grass growth. Even in the cooler months of autumn and winter, the system maintains a robust performance and enhances the grass's winter color.
  • Optimized year-round performance: The Capillary Hydroponics and Capillary Geothermal system delivers a firmer and drier playing surface, ensuring consistent performance for athletes. Players are protected from risks of playing on frozen, slippery, or waterlogged pitches. The result is an optimized performance experience all year round.
  • Energy-efficient and sustainable: Capillary Geothermal is an energy-efficient solution that makes the most of natural temperature differentials within the subsoil. It minimizes water consumption and maximizes grass growth while reducing operational costs. It is practical and versatile, working effectively across various climates and areas.
  • Low maintenance: Both the hydroponic and geothermal systems have few mechanical moving parts, reducing the risk of breakdowns. Centralized app-based control simplifies operation and maintenance, making it user-friendly for caretakers and maintenance crews. 

On the ground with Capillary Hydroponics and Geothermal

The first-ever Capillary Hydroponics green with a geothermal system in Sweden was installed in August 2023, at the Gothenburg Golf Club, the country’s oldest golf facility. Two months earlier, a Capillary Hydroponics tee with a geothermal system was installed at the Silver Spring Golf Club in Connecticut, USA.

The Gothenburg Golf Club was looking for a way to putt on natural greens that held PGA tour speeds and performance all year long and identified the CapillaryFlow solution as the only system in the world that offered a geothermal solution to warm the root zone, enabling grass to grow year-round in colder climates and withstand frozen ground conditions.

“This is a game-changer for our elite players and members alike, to be able to use natural greens 1-2 months longer in fall and 1-2 months earlier in the spring is fantastic!” said Ola Lindgren, head coach for the men's Swedish Golf Federation National Team. “The added advantage of a hydroponic system to keep greens speeds and uniformity at tour level is amazing.”

Hydroponic tee at Göteborgs GK (Hovås GK) in Gothenburg, Sweden

Hydroponic tee at Silver Springs CC in Ridgefield, Connecticut


All CapillaryFlow products are designed to be easy to install and decrease your maintenance efforts and costs. With +1000 installed venues worldwide, we know how to manage small to large scale projects effectively and all our products work perfectly in tandem with each other and the environment.

Importantly, we offer a year-round installation option, which sets us apart from other solutions, especially in regions prone to drought. Our approach eliminates the need for constant watering every 15 minutes during grass grow-in, thanks to efficient hydroponic irrigation. This flexibility allows us to work during the off-season for construction when labor costs are more favorable. Remarkably, our system promotes grass root development within just three days.


Want to know more about our products?

Would you like to know more about how we can help you build tees and greens with an extended season, improved wear tolerance, reduced water consumption and significantly less maintenance? Contact us!


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