Why Pre-Cooling?

Air conditioners are working harder these days because many that were adequate 10 or 20 years ago are now overloaded. Increased loads caused by increased personnel, increased electronics use, and obviously global warming. Because of this the condenser units are required to run for a longer time to attempt to provide the cooling that is desired. This technology allows the condensers to operate more efficiently providing a significant energy savings as well as extending the life of the condensing units because of the lower load.

The Problem

Air temperature used to carry away heat from air-cooled condensers greatly impact the performance of the system. As the temperature rises, so does the head pressure. As a result, cooling capacity falls while electrical demand (kW) and energy usage (kWh) increase. These problems are exacerbated when condensers are installed on rooftops where temperatures regularly exceed design conditions by 30-50 degrees. In response to insufficient cooling capacity issues, building owners are forced to purchase larger, much more expensive units or wet the coils with a garden hose. Larger units are very expensive especially when capacity problems only arise when the ambient temperature exceeds the original design. Using a garden hose does cool the units, but since no controls are used, it leads to wasted water, damage to the units, and leaks through the roof. The New England area has a higher electricity rate than any other area in the country. But the important part to pay attention to is the demand charge (kW). The great aspect of pre-cooling is that it is in use exactly when needed-no energy or water is wasted during ramp-up or ramp-down times.

The Solution

A condenser misting system is a cost-effective, sensible solution to capacity and energy usage issues that occur during upper ambient temperatures. By injecting a fine mist into the condenser air, the temperature is reduced immediately and the condenser is able to reject significantly more heat. As a result, this reduces the head pressure and compression ratio, so electrical demand (kW) and usage (kWh) are reduced and cooling capacity is increased. Furthermore, the benefits are realized exactly when they are needed--when the load on the system created by high ambient temperatures exceed the systems cooling capacity. The higher the ambient air temperatures, the better the system performs. The condenser misting system is a simple, measurable solution. With no moving parts to malfunction, it is safe, dependable, and requires little maintenance. Furthermore, the cost of the condenser misting system is quickly recovered through reduced demand charges, energy usage, and the ability to participate in electric utility company load curtailment programs. When condensers are undersized, particularly on design days, condenser misting systems can add capacity and eliminate the need to replace or supplement existing systems-allowing the units to cycle off.

How Does It Work?

Pre-cooling works on the concept of thermodynamics. By lowering the intake air temperature to the inlet of the condenser, the condenser is able to operate at a lower load thus increasing kWh and kW providing a savings on energy consumption as well as demand consumption. A 1000 PSI pump drives U/V filtered water through a series of tubes that has nozzles installed at engineered intervals. These nozzles provide a fine mist (typically the water droplets measure 8-10 microns). This mist is injected into the intake of the condenser. The mist flash evaporates and instantly provides a heat exchange that drastically lowers the air temperature at the intake. This lower temperature allows the condenser to operate much more efficiently. Photo is from www.microcool.com

Benefits

  • Increases system cooling capacity
  • Reduces kW (demand) and kWh (usage)
  • Extends compressor life
  • Reduces system downtime
  • Minimizes product losses
  • Requires minimal maintenance
  • Improves occupant comfort levels

What is Involved?

The first thing that happens is a pre-audit that determines any rebates that may be possible from any state or local governments. Many times these audits are fully paid by the state. After the energy savings determinations are made, we install the pump, tubing and fittings and enable it to run on its own, or tie it into the energy management system. Other components include filters, including a U/V filter to make sure that no impurities enter the system. A test is done to make sure the system is functioning properly. Once everything is functional, a post-audit is performed and that is the basis that determines the amount of the rebate provided to the customer.

What About Maintenance?

Yes, the system does require maintenance, although very little. Several times a year the filters will need to be cleaned and/or changed. In the winter, we will need to winterize the lines (evacuate the water from the lines) and store some of the components indoors. We come back in the spring to energize the system and ensure that it will operate efficiently for the coming hot weather conditions.

Why is This Important?

According to Department of Energy data, New Jersey and New York had the highest kWh rates in the contigious United States. Because electricity costs more on the east coast than any other area of the country, the main focus is reducing peak demand (those times where the most stress is put on the electricity providers). By reducing kW(demand), we can significantly reduce the electricity costs during these times, thus providing substantial savings. Furthermore, data from scientists across the globe points to warming trends to continue. As the warming trends continue coupled with rising energy rates, the time to save is now.