Manufacturers’ Commitment to Net Zero and Energy Efficiency
If you are a manufacturer, which many of our clients are, energy usage and the associated tariffs are a constant battle. It is one of the key areas of concern highlighted by Make UK, the leading trade body for UK Manufactures. In their report “Tackling Electricity Prices for Manufacturers1, Make UK notes that UK industrial electricity prices are 46% above the global average and four times higher than in the US. They advocate for measures such as removing policy levies from electricity bills and introducing a fixed electricity price for manufacturers to enhance competitiveness.
Make UK highlight that 92% of manufacturers consider net zero a priority, with 68% having already invested in energy efficiency measures.
Cooling Systems & Scope 2 Emissions
Cooling tower energy efficiency is crucial to managing energy usage and reducing Scope 2 emissions in manufacturing. Cooling systems which contribute to Scope 2 Emissions as defined by the GHG Protocol2; emissions derived from indirect greenhouse gas emissions from purchased electricity, steam, heat, can play a pivotal role in the consumption of energy across a manufacturing site. In some industries such as food and beverage, pharmaceutical and plastic moulding, this can contribute to as much as 40% of the energy usage across the site.
Control What You Can Control: Cooling Towers
I’m a strong believer in control what you can control. What I mean by this is that, although there is great and admirable work being done by lobbyists such as Make UK which I strongly support, if you don’t need to use the power in the first instance then don’t. There are many sites that are using outdated and inefficient control philosophies where tower fans are either on or off and control is not based on cooling demand. This goes for the pumps across the rest of the system as well but that’s a conversation for another day.
75% Energy Savings with Temperature-Based VSD Control
When the opportunity arises to replace a cooling tower and businesses consider their cooling tower’s energy efficiency, it presents a perfect time to consider the cooling tower control and type of tower. The cooling tower fan is the key contributor to energy consumption on the tower and is essential in regulating the cold-water temperature. Without it, you would lose 90% of your cooling capability but controlling this using a variable speed drive governed by the cold-water temperature set point will typically save 75% on energy consumption.
Fan Control & Axial vs Centrifugal Fans: Which Is Cheaper to Run?
The type of fan is also important, with axial fans being 50% more efficient than their centrifugal equivalents. Fixed drive motors add further energy efficiency and remove the maintenance worries of belt tensioning and replacement. With development in larger EC motors, the future looks bright for reducing energy consumption further still.
All of this is within your control when considering a new cooling tower and moves the needle towards how much energy will we need to consume as opposed to what is the best rate I can get on my tariff. Reduction in total energy is not a new topic and there are many energy savings companies and consultancies out there supporting the manufacturing sector with identifying areas of savings, however the cooling process, for all the energy it consumes, is often little understood as an area of significant savings and replacing like for like with higher efficiency motors adds little benefit.
Materials Matter: 316 Stainless vs Galvanised Steel vs GRP
Sustainability doesn’t just cover energy, and designing for longevity is equally important. As we’ve discussed earlier, the material of construction can have an impact on how long the cooling tower will last. Typically, you should be looking for a 20–25-year life out of a cooling tower that has been well maintained. Consumables within the tower such as packing, and drift eliminators will need to be replaced 2-3 times during this period however frequency can vary dependent on the water quality and maintenance regimes.
Opting for a longer life material such as 316 stainless steel or GRP will mean that replacement of the tower will be at the upper end of the 25-year period and will also reduce the total cost of ownership (TCO), as maintenance costs will be less than in a lower grade steel equivalent. Leak repairs and lining due to corrosion issues are common on galvanised and coated steel towers as well as a higher consumption of corrosion-controlling water treatment chemicals.
Where did all the water go? – Water Scarcity & Alternative Cooling Options
Needless to say, water is an essential factor in a water-cooling system and water scarcity is becoming a serious issue. According to BBC News, England will require an extra 5bn litres of water a day by 20503 and the Telegraph reported that Scotland is seeing the highest levels of water scarcity since 19644, a factor that will hit the manufacturing sector hard. With this in mind, serious consideration should be given to methods to reduce water consumption in water cooling systems, but you don’t necessarily need to throw the baby out with the bath water…pardon the pun. There is a balance to be met between energy and water consumption depending on the cooling load and cold-water temperatures that the process requires. Evaporative cooling is highly efficient, and you can reach temperatures close to the wet bulb temperature, but you are evaporating and losing a percentage of water to atmosphere through evaporation and drift and to drain in the form of blowdown. Typically, this is between 3-5% of the circulating flow. To put this into numbers, if you are circulating 100m3/hr you are losing between 3-5 m3 every hour. That’s the equivalent of 5 bathtubs or 20,000 pints every hour. I know which one I’d prefer to lose. This sounds like a lot but in comparison to what would once have been once through system this is highly efficient.
As water scarcity grows, clients are looking for alternatives that use less water. Dry air coolers (also known as air blast radiators / dry coolers or dry fluid coolers) can be considered but much depends on the target cold water temperature. A dry air cooler is cooling using sensible heat exchange so cold-water temperatures of the circulating fluid is governed by the ambient air temperature. The cooler can only cool to within a few degrees of this temperature so the resultant cold-water temperature would be far higher than that of a cooling tower. In environments where the cold-water temperature is less critical, or the ambient air temperature is relatively low compared to the desired cold-water temperature this could be a sensible alternative. Footprint should also be considered as they are less efficient than a cooling tower so will need at least double the space for installation. Additionally, energy costs will be higher in a like for like load comparison due to the less efficient nature of cooling.
The most viable alternative that should be considered when there is an opportunity for replacement is adiabatic coolers. These have the advantage of achieving the same cold-water temperatures as an equivalent cooling tower by pre-cooling the air through evaporation, but as the ambient air temperature decreases the cooler can work as a dry air cooler thus saving significant amounts of water (in the region of 90%) compared to an equivalent cooling tower.
There are multiple options of adiabatic coolers from spray systems to evaporative panel systems that I have covered in other articles but as this article has assumed you want a cooling tower, I have not gone into the detail of them here.
Like air coolers, adiabatic coolers also need more space than a cooling tower, approximately 1.5 times the installation area. There lifespan is not usually as long and they are more expensive than cooling towers due to the expensive coil, controls and multiple fans. Depending on the type of adiabatic, you can also eliminate the legionella risk and the requirement to register the unit with the local authority or HSE under the Notification of Cooling Towers and Evaporative Condensers (NCTEC) legislation. Calculate your ROI now →