Four Timely Benefits of Indirect-Direct Evaporative Cooling

December 1, 2008
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Pictured is an indirect-direct evaporative cooling system. This particular system, from United Metal Products, is providing cooling to a large grocery distribution center in Phoenix, Ariz.


As the cost of energy rises, businesses are forced to re-examine their current way of doing things. Not only does the energy crisis have businesses looking for effective ways to reduce overall costs, but they are also faced with the pressure and ethical responsibility of running their operations in tandem with the principles of sustainability.

In light of the current energy and oil crisis, how are businesses to not only cut costs, but also practice greater ecological stewardship? What can a contractor offer?

One of the most practical ways to increase a company’s bottom line and practice sustainability is in the area of cooling. Many companies assume their only option with regards to providing cooling is standard packaged air conditioning. However, indirect-direct evaporative cooling is a method of cooling that can be not only more cost effective, but also more sustainable. Such a method can help companies move towards being climate neutral. At the same time, contractors who offer such a system can have a business edge over competitors.

One company to recognize these benefits is the world’s largest retailer, Wal-Mart. It recently implemented a method of indirect-direct evaporative cooling at a Wal-Mart Supercenter in Las Vegas. When the largest retailer implements a method of cooling to enhance their bottom line, other businesses take notice.

FOUR REASONS

The bottom line is this: There are at least four timely reasons why indirect-direct evaporative cooling should be considered by any business. Contractors can use these reasons when trying to sell this cooling process to commercial business owners.

Reason 1 - Energy efficient.
The first reason indirect-direct evaporative cooling should be considered is because research shows it can be more energy efficient, for instance, than standard packaged air-conditioning. Many power companies - and this includes SRP, Pacific Gas & Electric (PG&E), Pacific Power, Southern California Edison, and PNM - are offering incentives to businesses that implement this effective method of cooling.

And, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) points out that systems that use a proven method for exchanger construction can lower energy consumption by 50 percent or more when compared to standard packaged air conditioning.

These systems work by cooling the air in a two-stage process. The first stage is the indirect stage. During this stage, the hot outside air passes through a heat exchanger where the sensible heat is removed.

Because this first stage cools the air without adding moisture, it has the advantage of lowering the dry-bulb and wet-bulb temperature without the use of compressors. This cooled air then goes through the direct stage where the air is adiabatically cooled by passing through an evaporative media that is designed to be 90 percent efficient.

FIGURE 1: According to the National Renewable Energy Laboratory (NREL TP-550-33905), power plants in Arizona and Nevada require an average of 7.55 gallons of water to produce 1 kWh of electricity. The chart takes the data from the NREL report and uses it to compare the hydro-footprint between packaged air conditioning and an indirect-direct system for a 100,000-square-foot facility that is 24 feet high.

As the indirectly cooled air passes through the evaporative media, the system is designed such that 90 percent of the sensible heat is exchanged for latent heat while simultaneously lowering the leaving air temperature. Once this takes place, the air can now be moved through the facility where it is designed to remove heat and provide a continuous stream of fresh outside air.

One key to remember: Water control is important in order to take advantage of this efficient cooling system. If the water conductivity and mineral content is not properly monitored and maintained by flushing or bleed-type methods, then the system will not work as effectively.

Reason 2 - CFC-free cooling.
A second significant benefit is that these systems are free from environmentally damaging products. The indirect-direct method produces desirable temperatures by taking advantage of the cooling properties of water. Because these systems rely on water, they leave a significantly smaller carbon footprint and therefore offer a sustainable method of cooling.

Reason 3 - Water savings.
The indirect-direct systems use a significantly less amount of water to provide cooling. This may not seem like the case at first glance. However, when the additional electricity needed for standard packaged air conditioning systems is considered, an indirect-direct system can use approximately 50 percent less water. This is because power companies primarily rely on large cooling towers and reservoir water to produce electricity. (See Figure 1.)

Reason 4 - Competitive initial cost.
An indirect-direct evaporative cooling system has a very competitive initial cost. This means that the savings that an indirect-direct system provides - by cutting the operation cost (sometimes in half) and decreasing maintenance costs - leads to real long-term savings at no additional initial cost.

CONCLUSION

Energy efficiency, environmentally friendly CFC-free technology, substantial water savings, and competitive initial cost make indirect-direct evaporative systems an attractive and timely choice for meeting the cooling demands of today’s businesses.

Contractors, on the other hand, can help business owners accordingly. They can tell these owners that not only will this method of cooling increase a company’s bottom line, it will do so without sacrificing the principles of sustainability.

Publication date: 12/01/2008

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