Chiller efficiency represents a critical factor in assessing a cooling system’s performance as well as every chiller plant’s overall sustainability in both environmental and economic terms.
The choice of chiller system plays a critical role in cooling large buildings and infrastructures. As such, achieving chiller efficiency is able to not only minimize operating costs but also generate energy efficiency, thus accessing environmental benefits and guaranteeing compliance with current environmental regulations. Let’s look at some key strategies to achieve it.
What is chiller efficiency
Chiller efficiency can be defined as the effectiveness of this type of system in generating cooling while cutting back on energy consumption.
The path towards achieving chiller efficiency is better understood in the current context of sustainability and rising energy costs. As such, the projects to accomplish chiller efficiency are often paired up with other environmental and cost-efficiency actions, such as achieving savings in water consumption in chillers.
As we’ll see below, there are various factors that can have an influence on chiller efficiency. These include the choice of chiller technology, the actual operating conditions, the maintenance practices and protocols, and the chiller plant’s load variability.
Measuring chiller efficiency
Chiller efficiency is typically measured using the following two parameters that relate the cooling output to the electrical energy input.
- Coefficient of Performance (COP): it measures the ratio of the heat removed (cooling capacity) to the electrical power consumed by the chiller. Mathematically, it's expressed as: COP = Cooling Capacity (watts) / Electrical Power Input (watts). A higher COP indicates better efficiency, so that more cooling is provided per unit of electricity consumed.
- Energy Efficiency Ratio (EER): EER is a similar measurement to COP but is often used in the United States (while also present in other regions). It measures the ratio of cooling capacity (in BTUs or British Thermal Units) to the electrical power input (in watts), so that EER = Cooling Capacity (in BTUs) / Electrical Power Input (in watts). Again, a higher EER signifies better chiller efficiency.
How to achieve chiller efficiency
Proper chiller selection
Operators must ensure they choose the most efficient chiller type and size for their specific cooling needs. Factors such as the load profile, climate, and system requirements must all be considered in the choice between air-cooled chillers, water-cooled chillers or absorption chillers, among others.
Operators must pay close attention to choose a chiller plant that is properly sized for the building, so that it operates at its most-efficient capacity. This is because some chiller systems typically present better performance at 40% and 60% of their peak capacity, while some may peak at approximately 70-75% load. This means they use less energy per unit of cooling capacity when operating at part-load conditions.
Additionally, the chiller plant must be designed with efficiency in mind. This includes properly sizing pipes, pumps, and controls to minimize energy losses and optimize system performance.
A comprehensive maintenance program must be implemented so that it includes cleaning and inspecting key components like coils, tubes, and heat exchangers. Otherwise, dirty or malfunctioning components can significantly reduce efficiency.
As part of regular maintenance operations, conduct periodic energy audits and efficiency assessments to identify areas for improvement and track chiller efficiency over time.
Optimal water treatment
Water quality in the chiller system must be monitored and maintained in order to prevent scale, corrosion, and biological growth. Microbes, scale or iron deposits (among other problems) that are not properly controlled can reduce chiller efficiency significantly. On the contrary, an appropriate water treatment chemicals and practices to ensure clean and efficient heat transfer.
Match output to actual cooling load
Operators must ensure chiller operating parameters (such as temperature and flow rates) are adjusted to match the actual cooling load. This is because overcooling or excessive flow rates can waste energy.
Implementing advanced chiller controls and monitoring systems will also be a winning strategy, as they allow to continuously optimize chiller operation based on real-time conditions and load variations.
Additionally, these operations can be automated to operate based on set temperatures, which can help reduce energy consumption.
Implement smart load management strategies
Implementing load-shedding strategies during partial load conditions can be beneficial for maximizing chiller efficiency. If a chiller system presents multiple chillers, this can be achieved by running them at partial capacity. As such, running multiple parallel devices will optimize energy and economic savings, allowing equipment to run at lower speeds.
Similarly, the implementation of adequate Energy Management Systems (EMS) can help operators monitor and control your chiller system in real-time, while also optimizing operations based on factors like outdoor temperature and building occupancy.
h3. Guarantee consistent, reliable data
Additionally, operators must establish a strategy to document operational data, so that efficiency and performance values can be recorded in chiller logs. It’s preferable if this is an automatic process, guaranteeing values are consistently recorded.
Chiller performance values should be recorded both at full and partial loads, thus effectively calculating chiller efficiency and being able to measure and diagnose the potential causes of inefficiency.
This is particularly important considering how a chiller plant represents an extremely dynamic piece of equipment. Chiller flows are not constant or rigid. In fact, chillers expand and contract from their original design, and are subjected to processes such as wear, tear and age. As such, accurate, continuous verification of their performance is crucial when striving for chiller efficiency.
Heat recovery systems
Current opportunities for chiller heat recovery are crucial for achieving chiller efficiency. Recovered heat can be used for space heating, domestic hot water, or other purposes, reducing the need for additional heating systems.
At the same time, Thermal Storage Tanks (TES tanks) can significantly improve chiller efficiency by allowing you to shift the cooling load to off-peak hours, reduce chiller cycling, and take advantage of lower electricity rates during non-peak times.
As such, during periods of low electricity demand or lower electricity rates (usually at night), the chiller system can produce chilled water and freeze it in the thermal storage tank. This chilled water is then used to cool the building during peak demand periods, reducing the load on the chiller during the day when electricity rates are higher.
Upgrading or Retrofitting
Modern chillers often have improved efficiency and control capabilities, compared to old and inefficient chiller systems. This is why it’s often important to consider upgrading or retrofitting older chillers with newer, more energy-efficient models.
Modern, high-efficiency chillers typically have a higher COP, indicating better energy efficiency. Additionally, they incorporate improvements such as variable speed compressors or advanced control systems, which can adapt to varying operating conditions and optimize the chiller's performance in real-time. They are also designed to perform exceptionally well at partial load conditions, resulting in significant energy savings in real-world applications where loads vary.
This is precisely where, at Araner, we can help. As part of our commitment to develop cutting-edge heating and cooling engineering, we’re able to design custom solutions to achieve maximum energy savings and chiller efficiency.
Take a look at our district cooling initiatives, designed with cost-efficiency and sustainability as principles, or get in touch with our team to learn more about how we can help you achieve maximum chiller efficiency.