When looking for new energy savings opportunities in an HVAC system, one has to look deeper than the system itself. HVAC units can be complicated to operate, especially when they are coupled to each other and connected to one or more cooling towers.
The energy consumptions are closely linked to the efficiency of their subsystems like compressor, pumps, exchangers, evaporators, etc. These subsystems are also heavily dependent on other equipment such as cooling towers, distributor pumps and chillers, which in turn has a nominal efficiency and an optimum efficiency.
The chiller may have the largest load of any component, it may not be the largest contributor to total annual energy consumption. Therefore, it’s more important to ensure that all the components work together throughout the year for improving your system’s energy performance to achieve the greatest savings.
There are various equipment and low- or no-cost operational changes that can be investigated to greatly reduce the energy use of an existing system, without risk to proper plant operation or occupant comfort. Let’s review some of those options to achieve maximum savings.
Install systems to measure the overall Coefficient of Performance:
Before you do anything, the first and foremost step towards energy saving is to monitor the consumption in chiller units and cooling towers. This will help you establish the COP for each unit and tower by measuring the flow rate, the inlet and outlet temperature and the electricity consumption. More importantly, it can help you to construct an overall COP that includes the distributor pumps, the auxiliary pumps and the consumption of the cooling towers, and factors in the climatic conditions.
Energy Monitoring System (EMOS) from CET-Enviro is the most effective and reliable system that automatically records specific power consumption of chillers in the most accurate way 24×7. It continuously collects, analyzes and reports on chiller operating data through the internet facility integrated into the system and connected to a cloud-based server. Ideally, you would be able to compile a data history for an entire year to cover all of the seasons and as many production conditions as possible.
This critical information collected at the server can be used to manage energy and operating costs on a routine basis and this significantly helps in improving the performance potential of the chiller that saves up to 15% in chiller energy consumption.
Invest in a new refrigeration technology:
The latest HVAC units are particularly efficient, thus achieving a COP of at least 7 or 8. These refrigeration units are highly modular and do not become less efficient, because they contain several small compressors that start-up in a staggered sequence. They are, however, very expensive and not very easy to maintain. If your budget doesn’t stretch that far, similar improvements in energy consumption can be achieved by adding variable power control units such as EMOS to your existing HVAC system.
Ignore peak load for chiller efficiency:
Many engineers and facility managers compare chiller efficiency based on a single number — peak load kW/ton. However, the typical chiller plant in a commercial building will never operate at these peak conditions. For office buildings, it would be better to ignore the peak kW/ton and instead compare the IPLV (integrated part-load value) or NPLV (non-standard part-load value) ratings.
Even though each building’s load profile is unique, these numbers are meant to be a better metric for comparison since they attempt to simulate a more typical load and operational profile for an office building in a moderate climate. These small differentials can help you achieve huge energy savings in the long run.
Take advantage of cool outdoor temperatures:
Most chillers can benefit from condenser water temperature reduction during cooler weather. A chiller and cooling towers are needed for the very few very hot and humid hours of the year. For the rest of the year, the towers can easily and efficiently provide cooler water.
When the climatic conditions allow, adding passive outside-air heat exchangers can reduce the need for cooling towers and the associated consumptions. However, these savings may depend on climate, load profile, and equipment sizing, so analysis must be present to determine the proper control strategy.
As we have cleared, there are a variety of solutions for optimizing your energy consumption. However, the most crucial solution might be the Energy Information System. So the more your Energy Monitoring System is well-documented, the more effective these solutions will be.