ARTICLE

Free cooling

27 May 2021

Achieving the full potential of a process cooling system opens opportunities to save money and improve operational efficiency, but requires a whole lifecycle approach. Richard Payne looks at the issues

THE CONCEPT of free cooling is nothing new. In the old days, we cooled down our cars heated up by the sun by opening the windows, as the outside was colder than the inside. To some it may come as a surprise, but the same principle applies to free cooling in an industrial environment.

Any company or organisation using an externally sited chiller to cool their process can benefit from free cooling. Whenever the outside temperature is low enough to cool down the process fluid without the intervention of a chiller (mechanical cooling), we can implement a free cooling solution. This can be in the form of partial free cooling (where the chiller’s compressors are still doing some of the work to cool) to full free cooling (where the full load on the chiller is offset). In contrast, an externally sited chiller’s compressors with no free cooling capabilities will be working flat out to achieve the same.

At 5˚C below the process supply fluid temperature, all the process heat is removed by the ambient air in the free cooler – providing full free cooling

Depending on the time of the year, as the ambient air temperature continues to fall, the amount of process heat taken out of the process fluid by the air increases, progressively reducing the load on the chiller. At 5˚C below the process supply fluid temperature, all the process heat is removed by the ambient air in the free cooler – providing full free cooling. This makes free cooling the cheapest and greenest way to provide cooling.

Cool climate

In the UK, Ireland and much of Western Europe, the relatively cool climate and ambient temperatures allow for partial or full free cooling for much of the year. This means that substantial energy savings can be achieved particularly between the months of October and April, in some cases reaching up to 80% electricity savings.

When the ambient air temperature drops just 1˚C below the process fluid return temperature, a 3-way valve diverts the returning process fluid through the free cooling coil in which the cooler ambient air removes process heat and cools the returning fluid (partial free cooling), it then flows through the chiller’s evaporator where the required set point temperatures are achieved – easing the demand on your chiller’s components and extending their operational life. Full free cooling is achieved when the ambient air temperature continues to fall, and the returning fluid from the free cooler meets the required process temperature.

Free cooling works with either a chiller with a built-in free cooling coil or a free cooler working in series with a chiller. The latter is more efficient, due to the larger surface area provided by the air cooler. A remote free cooler is designed to do nothing but provide free cooling and has its own purpose built control system and 3-way valve and bypass system and therefore is a simple and reliable way to give maximum savings and quick payback.

As the system is fully packaged, complete with integral controls, 3-way valve and actuator, and bypass pipe work, they can be easily installed on existing systems as well as new builds. Additionally, no communication between the free cooler and chiller is necessary, which in typical process cooling systems, allows to offload chillers for up to 90% of the year.

You can choose from solutions with multiple fixed fan speeds, inverter speed control and Electronically Commutated (EC) fans for varying noise applications. The units control panels are designed to offer ease of use with a ‘plug and play’ solution and 4G connectivity. They can be configured to meet your individual project requirements such as low noise, space restrictions and aesthetics and integrate with BMS.

Bottom line benefits

Free cooling is a concrete solution that will reduce mechanical energy consumption, lower the carbon footprint, reduce load on mechanical parts and therefore reduce maintenance cost and extend life of your cooling equipment. In case of a chiller, smaller load demands can also lessen the depreciation value of the unit over its lifetime. It is a solution that is easy to retrofit (space permitting) and can deliver a real quick payback for the new equipment.

Additionally, manufacturers looking to add free cooling into their systems, but trying to avoid capital investments, have the opportunity to benefit from programs like the ICS Cool Energy Flex. The equipment- as-a-service offer comprising a monthly package provides customers with running cost reductions versus the existing plant running costs. This type of a long-term solution is a fixed, hard-piped install to the customer’s process, offering energy savings, maintenance and annual cooling circuit fluid analysis and the option to upgrade as technologies improve. The flexibility of this business model can be a significant ingredient to the decision process and making a step into a more sustainable cooling.

Case study

Savings for speciality chemical manufacturer

Three air cooled chillers and a 360kW free cooler system resulting in 42% annual energy savings for a chemical manufacturer. This means a return on investment in 6-9 months and prolonged chiller lifetime as a result of reduction in use and a comprehensive planned preventive maintenance (PPM) contract

The customer, a leading manufacturer of speciality chemicals, was planning to move their existing bead mill process (comprising 7 mills) to a new manufacturing site that would be suitable for expansion to 16 mills. In the previous set up, they had been cooling each bead mill with individual chillers but wanted to increase the energy efficiency of the system through a new chilled water ring served by larger chillers.

The solution

A site visit determined the process required a maximum design load of 358kW of cooling and pressure independent control valves at each bead mill connection to allow for precise flow control. To achieve the overall aim of improving efficiency and saving energy, detailed and comprehensive design brief recommended three iC 660 air cooled i-Chillers (capable of managing the total load on a Duty/Duty/Assist operation) with a 360KW free cooler system.

The result

Thanks to the cooling system upgrade and the addition of the free cooler, the customer is using less power during lower ambient conditions, which translates to over 210,000 kWh of energy and £21,000 saved annually. Further benefits include far lower plant running costs, lower carbon footprint of their production facility, higher coefficient of performance, large long term savings, return on investment within 6-9 months and prolonged chiller lifetime as a result of 1) reduction in use and 2) planned preventative maintenance contract taken out at point of purchase.

Richard Payne is marketing director at ICS Cool Energy Group

https://www.icscoolenergy.com/

 
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