How to choose a shallow geothermal chiller for larger buildings?
Chiller units are often the largest energy consumer among HVAC devices (heating, ventilation and air conditioning). They are present in most buildings as they ensure a suitable and comfortable working environment throughout increasingly hot summers. During these hot months chillers often consume more than 50% of the electricity a building needs. Therefore, choosing the right standard or geothermal chiller for your building is extremely important.
In this post, we will try to answer the following questions:
How do chillers and shallow geothermal chillers work?
In order to cool a room, you need sufficient cooling energy. This energy is delivered by a cooling medium – such as cooling water. Cooling water circulates through the cooling system and devices and thus cools the rooms. In the process of cooling a room or a building, the cooling medium loses its cooling energy and heats up. The medium goes back into the chiller which cools it down again and sends it to the cooling system to repeat the process of cooling the desired place.
An internal circulation flow is constantly going on in the chiller unit. There, water or another cooling medium circles through the evaporator, compressor and condenser. In each of these components, a thermodynamic process occurs and changes the pressure, temperature, the volume and the physical state of the cooling medium.
During this whole process, the heat from the cooling medium is “removed” from the chiller, and the cooling water is once again ready to cool the premises.
The chiller needs electricity to do its job. You should strive to find an efficient chiller unit where as little electricity as possible gets you as much cooling energy as possible. A chiller’s efficiency is reflected in the Energy efficiency ratio (EER). It indicates the performance of the system in relation to the energy consumed.
These coefficients and ratios are very unfavourable when it comes to air-cooled chillers during the hottest months due to the hot summer air. That’s why cooling energy is generally the most expensive during this time.
Conversely, the coefficient can be increased by the use of renewable energy sources, such as shallow geothermal energy. A shallow geothermal chiller can use lower groundwater temperatures to passively cool buildings or to help with active cooling, thus reducing electricity consumption.
The difference between air and water-cooled chillers
Chillers can use air-cooled or water-cooled condensers.
Air-cooled condensers resemble the “radiators” that cool car engines and push air across a grid of refrigerant lines. Because they rely on air for cooling, the ambient temperature must be 35 °C or lower, otherwise such chillers get very inefficient (unless they are made specifically for higher air temperatures).
Air-cooled chillers are suitable for small and medium-sized buildings and are generally much less energy efficient. Their installation is cheaper, but they have a shorter service life, as they are installed outside buildings and operate in adverse temperature conditions.
Water-cooled condensers transfer heat from the cooling medium into condenser’s water. The heated water from the condenser can be then pumped to a shallow geothermal energy source if you are using a shallow geothermal chiller.
Water-cooled chillers, e.g. geothermal chillers like Menerga Rewatemp, are often the only option for larger buildings, as they are more powerful and consistent. Their installation is more expensive, often takes up more space and requires access to water, but they have a longer service life, as they are installed inside buildings and operate in favourable temperature conditions.
What’s important when choosing a standard or geothermal chiller?
The purpose of the geothermal chiller
What will you use the chiller for? If it is intended for cooling buildings on hot days, it will be used mainly in summer, when the air heats up considerably, so it must be as efficient as possible during those few months. If you are going to use it to cool a room with servers and IT equipment, it will work all year round, which requires a different approach, as you want constant efficiency, reliability and consistency.
The heat load of the building
The chiller must be powerful enough to cool the intended space. That’s why you need to determine the amount of heat the chiller has to remove from a building or a room. We recommend you involve an expert when determining the heat load.
The heat load is usually expressed in kBTU/h or in KW (kilowatts) and when you know it, you can compare it to a chiller’s capacity and determine if it’s powerful enough to cool your building.
Determine the type of cooling medium, temperature, flow and pressure
Once you know the heat load, you should determine the cooling medium, its target temperature, and the flow rate and pressure that the chiller must provide during the cooling process. If the flow rate or pressure is too low, heat removal won’t be sufficient. If the flow rate or pressure is too high, they can damage your equipment.
Where is your building located? In an industrial area, in a city, in the countryside or near the sea? Is the chiller going to be inside or outside the building? Remember, the environment can affect the exposed parts of the chiller and affect it’s service time.
The environment can also dictate the size of the unit and any accessories such as air filters.
Noise generated by the generator is also important. What level is still acceptable in your environment?
The location of the chiller in relation to the cooling devices is another important factor. The closer the unit is to the cooling device, the more efficient the cooling, as the temperature of the refrigerant will not rise on the way to the device. The optimum coolant temperature must also be ensured by proper cooling line insulation.
The size of the unit is generally dictated by the cooling needs and the environment of the building, especially if cooling towers are needed.
However, state-of-the-art compressor technology and optimally coordinated device components result in very powerful compact chillers, which should also be considered and can often be the right choice.
Air or water-cooled geothermal chiller
We already compared the two types above, but we’re going to iterate that if you have the chance, you should seriously consider a shallow geothermal chiller as it is usually the most efficient choice.
Alright, after geothermal heat pumps, we also took a closer look at the chillers. Now you know what’s important to consider in order to efficiently heat and cool your building. What is the next step? Energy source preparation and energy production! We will check it out in our next article in this series on shallow geothermal energy.
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