How do ground source heat pumps work?

Looking to reduce your business’ carbon footprint? Increase your energy efficiency? Lower your energy bills?

A heat pump is a no-brainer. But it can be tricky to know what kind is right for your business.

Here, we’ll explore everything you need to know about ground source heat pumps – but remember to head over to our dedicated guides on air source and water source heat pumps too, to get the full picture.

What is a ground source heat pump?

A ground source heat pump is a device that uses electricity to heat or cool a building.

In the winter, it collects low-temperature solar energy that is stored in the ground or water outdoors and converts it to a higher temperature using a compressor. In this way, it’s able to heat buildings and hot water in a way that feels similar to a normal boiler.

Meanwhile, in summer, it can work in the same way as an air conditioning unit, moving heat from inside a building to outdoors in order to cool it down.

If you’re looking for a heating system for your home or business that uses renewable energy, this is one of the most effective systems that you can install.

A ground source heat pump will provide the building with 100% of its heating and hot water needs throughout an entire year. It’s a genuine, effective alternative to traditional fossil fuel heating systems.

Should you switch to a ground source heat pump?

Umming and ahhing about whether your should switch to a ground source heat pump? Here are the pros and cons to help you decide.

Ground source heat pump advantages

Switching your power source to a ground source heat pump comes with tons of benefits, including:

• Lower carbon emissions
• Highly efficient
• Lower energy bills
• Improved quality of air
• Compatible with other renewable technologies like wind and solar power
• Low maintenance
• Long lifespan
• Visually unobtrusive (as it’s located below ground)
• Quiet

Ground source heat pump disadvantages

There aren’t many disadvantages to a ground source heat pump. However, they tend to be less popular than air source heat pumps for both residential and commercial buildings.

Here are a few reasons why:

• More expensive
• Harder to install
• Installation can be disruptive
• Requires more space

Air source heat pumps work in a similar way to ground source heat pumps except that they extract warmth from the air instead of the ground – meaning there’s no need for groundwork.

At Clade, we offer commercial air source heat pumps as we believe they’re the best option for the majority of businesses. Get in touch with our team to learn more.

What applications can a ground source heat pump be used for?

You might be under the impression that a renewable energy source like a heat pump is only available for installation in new build properties. But this isn’t true at all.

A ground source heat pump can be used for a variety of applications and in both new and existing buildings.

This could include new build homes, existing homes, schools, swimming pools, libraries, office buildings, industrial units, listed buildings and more – in both rural and urban locations.

As you can see, most properties can reap the benefits of affordable, efficient, low-carbon, future-proof options for heating.

How does a ground source heat pump work?

A ground source heat pump works through a process of absorbing the natural heat from the ground and transferring it into a higher temperature that can be used to provide heat and hot water to a building.

But how exactly does it do this?

Well, the system consists of the pump itself which is installed indoors and connected to a series of pipes underground, known as ground collectors.

Cold fluid circulates throughout this pipe network. As it does so, it absorbs the surrounding energy that can be found in rock, soil, lakes and streams.

A compressor within the heat pump then takes the fluid and increases the temperature before passing it through the heat exchanger to heat hot water cylinders, radiators, and other heating systems within the building.

Open-loop versus closed-loop systems

When you’re choosing a ground source heat pump, there’ll be several options to choose from – although your system designer can help you to select the best type for you.

The first consideration is whether you want an open-loop or a closed-loop system.

Closed-loop systems

In a closed loop system, a heat transfer solution is circulated through a loop pipe called a ground loop, which is buried in a garden or – in the case of water source heat pumps – a lake.

This solution absorbs heat that is being stored in the earth or water, before passing it through an intelligent heat exchanger into the heat pump.

The key here is that the ground loop is only filled once, and the solution is then used again and again – hence why it’s called a closed loop system.

These tried and true ground source heat pumps are an established technology. In fact, they’ve been around for over 50 years!

The ground loop length can be tailored to accommodate the size of your home and the heat load you require.

Typically, longer loops can draw more heat from the ground. However, these need more space to be buried in. In circumstances where there’s not enough space, a vertical borehole can be drilled as an alternative – more on that later.

Open-loop systems

Instead of circulating a heat transfer solution, an open-loop system circulates clean ground water.

Essentially, this ground water is pumped directly from a nearby aquifer to your indoor ground source heat pump.

As the water flows through the pump, the heat is extracted and the water is then discharged back to its source, a discharge well or an approved drainage ditch depending on local codes.

Because the water is only used once, these systems are often referred to as ‘pump and dump.’

They’re even more efficient than closed-loop pumps, making them ideal for buildings that have a lake, river or steam nearby.

Just bear in mind that you’ll need consent from the Environment Agency for England and Wales or the Scottish Environment Protection Agency (SEPA) to install and use one of these systems – and there’ll be additional regulations to account for.

This is because these systems actively pull water into the system for operation. The water needs to be clean, safe and sufficient for the system to draw and filter the water to and from the main water source.

Bore holes versus slinkies for ground source heat pumps

Another consideration when you’re selecting a ground source heat pump is whether to use horizontal or vertical ground loops – AKA slinkies or boreholes.

Slinkies

Slinkies, also known as slinky pipes, collect heat from surface soil, roughly 1.2m below the ground.

This pipework is buried in trenches between fine layers of sand to ensure optimal contact with the ground for maximum heat extraction.

Meanwhile, in another trench, header pipework connects the slinkies to the ground source heat pump by a manifold.

A heat transfer solution is then pumped around the pipework, which absorbs energy stored in the ground and effectively transfers this energy back to the heat pump.

Soil was the first heat source used to work with ground source heat pumps, and continues to be a reliable source today. In fact, slinkies are the most common method of all ground array collectors used for individual property projects.

Why? Well, the soil continuously gains and replenishes most of its heat from solar energy. In this way, the pipe is able to extract heat from the earth year-round and can last for a lifetime — up to 100 years!

Not only that, but slinkies are very effective and easy to install. The ground array required is sized appropriately to meet the building’s required heat load – for every 60m of pipe, about 1 kW of energy is typically absorbed from the ground.

Boreholes

Boreholes are vertical ground arrays or collectors that collect heat energy stored in the surface soil that dissipates through rock layers. They can be anywhere from around 60m to 200m deep.

During installation, a U-shaped straight pipe is inserted into the borehole and connected through a trench to the ground source heat pump. The surrounding space is backfilled with a thermal grout to ensure thermal conductivity from the ground to the borehole pipe.

The ground source heat pump circulates heat transfer fluid through the U-pipe, to provide a stable and sustainable heat source.

Boreholes are often used for large commercial projects and district heating schemes. However, they can also be a great solution for smaller sites where space saving is a priority or where there’s insufficient space for horizontal arrays such as slinky pipes in trenches.

This is because only 150mm width of garden space is required per borehole.

Boreholes are significantly more expensive than slinkies due to additional preparation and drilling costs. But it’s worth noting that just one borehole is typically required per property.

They’re also becoming more economically viable through Shared Group Loop Array schemes for multiple residential properties, large commercial projects and any site with heat loads above 100 kW. Reduced mobilisation costs for the drilling rig, on-site scalable efficiency and the degree of diversification can lead to savings in the long run.

Ground source heat pump emissions

Ground source heat pumps boast high efficiency due to the fact that they emit no emissions.

As a genuine, effective, low-carbon alternative to fossil fuel heating systems, there are few better options open to property owners.

Poor air quality accounts for many deaths each year. With the help of a low-carbon heating system, you could reduce the emissions linked to your property.

A ground source heat pump doesn’t create particulates, Sulphur Oxide (SOx) or Nitrogen Oxide (NOx). On top of that, the greater the contribution of solar and wind power systems to the electrical grid, the lower the carbon content of electricity.

This should mean that over time, ground source heat pumps become even less carbon intensive.

Refrigerant choice

Although heat pumps don’t release emissions, they do require the use of a refrigerant.

Unfortunately, most refrigerants used in heat pumps today are synthetic – by which we’re mainly referring to HFOs (hydrofluoro-olefins) and HFCs (hydrofluorocarbons), often branded ‘climate killer refrigerants.’

These typically have a very high global warming potential (GWP). Plus, they contain toxic ‘forever chemicals’ known as PFAS. These don’t break down naturally and instead show up in many watercourses where they poison wildlife and, in some areas, even endanger human health.

But it doesn’t have to be this way!

In recent years, F-gas regulations have led to a rise in heat pump manufacturers using natural refrigerants like CO2 and propane.

Natural refrigerants are clean, have a low GWP and don’t contain environmental toxins like PFAS. Plus, they’re highly efficient. In fact, in heat pumps, natural refrigerants achieve higher coefficient of performance (COP) at low ambients and high flow temperatures.

As a certified B Corp, we only use natural refrigerants here at Clade. After all, we believe they’re a no-brainer for both people and the planet.

Talk to our team about heat pumps

Keen to invest in a heat pump for your business premises? We’re here to help.

Our talented team of designers, manufacturers and installation experts will be able to listen to your business’ requirements and create a solution bespoke to your needs.

Get in touch to learn more.