Indirect-Direct Stand Alone Evaporative Cooler

Summary

Indirect-Direct Stand Alone Evaporative Cooler

Cooling Systems in Dry Climates: Indirect-Direct Evaporative Cooling vs. Mechanical Cooling

A device that employs both indirect and direct evaporative cooling instead of using the vapor-compression/refrigeration cycle. This maximizes evaporative cooling while increasing humidity less than direct evaporative cooling alone.

Synopsis:

Traditional evaporative coolers use only a fraction of the energy of vapor-compression or absorption air conditioning systems. Unfortunately, except in very dry climates, they increase humidity to a level that makes occupants uncomfortable. Two-stage indirect-direct evaporative coolers do not produce humidity at levels as high as those produced by traditional single-stage evaporative coolers, and so may be useful in a wider range of applications.

According to the Emerging Technologies Coordinating Council, “The existing two-stage evaporative cooler on the market does not achieve the full potential of this technology. Previous lab testing has shown an achieved evaporative effectiveness of 88 to 98%. The OASys product, the result of a CEC PIER Program, appears to be able to achieve the technology potential. Lab and field monitoring has indicated that the OASys technology can achieve evaporative effectiveness from 104 to 111%. "In addition to their widespread use in dry climates, there are many cost-effective applications for evaporative cooling in locations with moderate humidity, including industrial plants, commercial kitchens, laundries, dry cleaners, greenhouses, spot cooling (loading docks, warehouses, factories, construction sites, athletic events, workshops, garages, and kennels) and confinement farming (poultry ranches, hog, and dairy). In western Washington and Oregon, it is surprisingly dry during warm summer days, and indirect-direct evaporative cooling is practical in almost every instance in most locations.

These units do not provide the same comfort as a DX chiller. Because of the added humidity, any cooling cycle that includes direct evaporation, including indirect-direct evaporative cooling, may have little thermal comfort benefit.

Energy Savings: 30%

Energy Savings Rating: Comprehensive Analysis What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

TAG Technical Score: 2.4

Details

Indirect-Direct Stand Alone Evaporative Cooler

Cooling Systems in Dry Climates: Indirect-Direct Evaporative Cooling vs. Mechanical Cooling

Item ID: 23

Sector: Commercial

Energy System: HVAC--Other HVAC Systems

Technical Advisory Group: 2009 HVAC TAG (#2)

Synopsis:

Baseline Example:

Baseline Description: Mechanical DX cooling
Baseline Energy Use: 7.4 kWh per year per square foot

Comments:

The baseline uses DX cooling for an commercial building. The 2009 Commercial Building Stock Assessment gives the actual electrical building energy use index(EUI) for various types of heating and cooling systems (Table D-EA5). Office buildings with electric heating and cooling have an EUI of 20.1 kWh/sf/year. Office buildings with no electric heating or cooling use only 8.2 kWh/sf/year, indicating that the combined HVAC heating and cooling energy use is 11.9 kWh/sf/year. For all commercial buildings, the corresponding numbers are 19.9 and 9.4 kWh/sf/year, respectively for a heating and cooling use of 10.5 kWh/sf-year.

Commercial buildings with electric cooling and with no electric heating have an electrical EUI of 16.8 kWh/sf-year (14.8 for office buildings). This indicates that the heating load for all categories of commercial buildings is about 3.1 kWh/sf-year (19.9-16.8) with a cooling load of about 7.4 kWh/sf-year (10.5-3.1). The corresponding electrical EUI for office buildings with electric cooling with no electrical heating is14.8 kWh/sf-year which indicates a space heating load of 5.3 kWh/sf-year with a corresponding cooling load of 6.6 kWh/sf-year (11.9-5.3).

Since this technology can be applied to many types of commercial buildings, a baseline cooling energy use of 7.4 kWh/sf/year is assumed (NEEA,12/21/2009).

Manufacturer's Energy Savings Claims:

"Typical" Savings: 50%
Savings Range: From 30% to 60%

Comments:

(Munters, 3013) claims 50% less energy than mechanical cooling, baseline unknown
(Westaire, 2013) claims over 70% less energy than mechanical cooling, baseline unknown

Best Estimate of Energy Savings:

"Typical" Savings: 30%
Low and High Energy Savings: 10% to 70%
Energy Savings Reliability: 5 - Comprehensive Analysis

Comments:

Energy savings depend on the climate. Psychometric analysis in the BPA territory shows about 30% savings in cooling energy per Davis Group study.(Davis Energy Group, 1995)

Energy Use of Emerging Technology:

5.2 kWh per square foot per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: square foot
Potential number of units replaced by this technology: 166,151,600
Comments:

This stand alone technology is best suited as an alternative to DX chillers. It would be an appropriate selection for virtually any small commercial office building. The commercial building stock in the Northwest is quantified in the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014 (before the update was completed -- from early January, 2014). The small building portion of the region's stock is multiplied times the percentage of commercial space that is conditioned based on the 2009 CBSA. The 2009 CBSA also indicates that office space accounts for 19% of the total floor space or square footage of the building stock (Table 16) and that 33% of the total square footage is accounted for by buildings with less than 20,000 sf of floor space (Figure 9). The conditioned space (given below) of 2,649,946,000 sf is multiplied by 0.33 x 0.19 to provide a total of 166,151,600 sf of floor space that could potentially be retrofitted to this technology. Note that this technology may not provide the same level of comfort as the DX cooling being replaced.

	Total Commercial Floor space	% Conditioned	Conditioned space
Source, units	(NEEA, 2014) (s.f.)	(NEEA, 2009 App C)	(s.f.)
	3,118,000,000	84.7%	2,640,946,000

Regional Technical Potential:
0.37 TWh per year
42 aMW
What's this?

Regional Technical Potential of an Emerging Technology is calculated as follows:

Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)

First Cost:

Installed first cost per: square foot

Comments:

The installed cost is approximately $1,000 more than traditional air conditioners for the 5-ton capacity.

Cost Effectiveness:

Simple payback, new construction (years): N/A

Simple payback, retrofit (years): N/A

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Comments:

Each location is different, depending on annual cooling hours and local electric rates. Conservatively, we can expect payback in less than 5 years.

Detailed Description:

Evaporative cooling is the process of evaporating water into the surrounding air to cool the air. The heat that is moved from the air and into the water is called latent heat. Latent heat is the amount of heat that is needed to evaporate the water. The heat is drawn from the air. When considering water evaporating into air, the wet-bulb temperature compared to the air's dry-bulb temperature is a technology of the potential for evaporative cooling. The greater the difference between the two temperatures, the greater the evaporative cooling effect. When the temperatures are the same (i.e., at 100% relative humidity), no net evaporation of water in air occurs, thus there is no cooling effect.

In the first stage of an indirect-direct evaporative cooler, warm air is pre-cooled indirectly without adding humidity by passing it through a heat exchanger that is cooled by evaporation on the outside. In the direct stage, the pre-cooled air passes through a water-soaked pad and picks up humidity as it cools, thereby achieving the coldest air possible without the use of CFCs or compressors. Since the air supply is pre-cooled in the first stage, less humidity is needed in the direct stage to reach the desired cooling temperatures.

Commercial examples (from the Western Cooling Efficiency Center, http://wcec.ucdavis.edu/content/view/88/106/ ):

• Alter-Air Corporation Model: ACE 4049: www.alter-air.com

• Des Champs Technologies Model: Oasis: www.deschamps.com

• Essick Air Products, Inc. Model: IM70 (indirect add-on module):
www.essickair.com

• KR Products, Inc. Model: The Penquin 4444: www.krproductsinc.com

• Speakman CRS Model: OASys (residential): www.oasysairconditioner.com

• Spec-Air Model: Acer (commercial) 6850: www.specair.net

Product Information:
Westaire, Direct/Indirect Evaporative Cooling Munters, Direct/Indirect Evaporative Cooling

Standard Practice:

Cooling in standard practice is accomplished with either:

• Direct only evaporative cooling with limited results, which is fine for make-up air on a large exhaust system, or

• Direct expansion (DX) refrigeration cycle systems with compressors that have relatively high energy use compared to evaporative cooling equipment. This technology provides two stages of evaporative cooling.

Development Status:

The equipment is available for use in modular classrooms, post offices, residences of approximately 1600 square feet, and other applications at about this scale. The 5-ton capacity unit is a normally-stocked item. Units of up to 20-ton capacity are available with a 20-week lead time.

Non-Energy Benefits:

Provides back-up power in case of grid power failure

End User Drawbacks:

• People tend to associate this technology with a “swamp cooler,” which is a barrier.

• Maintenance associated with evaporative cooling equipment is relatively high compared to refrigeration cycle equipment.

• The automatic water quality management system must be properly serviced for proper operation and health considerations.

Operations and Maintenance Costs:

No information available.

Effective Life:

Comments:

12-15 years, with proper maintenance.

Competing Technologies:

DXcooling using compressors and refrigerant.

Reference and Citations:

Richard Bourne, 04/04/2004. Development of an Improved Two-Stage Evaporative Cooling System
California Energy Commission

Premier Industries, 09/19/2013. Indirect/Direct Cooling Unit
Premier Industries, Inc.

Davis Energy Group, 01/01/1993. Indirect/Direct Evaporative Cooler Monitoring Report
Sacramento Municipal Utility District

Davis Energy Group, 01/01/1995. Indirect/Direct Evaporative Cooler Monitoring Report - 1995
Pacific Gas & Electric Company

Davis Energy Group , 01/01/1995. Indirect-Direct Evaporative Cooler (IDEC) Development Project Final Report
California Energy Commission

Davis Energy Group , 01/01/1998. Field Evaluation of Residential Indirect-Direct Evaporative Cooling in PG&E’s Transitional Climates
Pacific Gas & Electric Company

Dick Bourne, 01/01/1998. Evaporative Cooling, Natural Cooling for Dry Climates
E Source Tech Update

Davis Energy Group , 10/09/2013. Evaporative Cooling Market Study
ACMA Technologies Pte. Ltd.

Davis Energy Group , 01/01/2002. Advanced Evaporative Cooling White Paper
Heschong Mahone Group

Howard Reichmuth, 11/06/2006. Assessment of Market-Ready Evaporative Technologies for HVAC Applications
New Buildings Institute

SWEEP, 09/14/2007. SWEEP/WCEC Workshop on Modern Evaporative Cooling Technologies
Southwest Energy Efficiency Project

ASHRAE, 10/01/2009. Standard Benchmark Energy Utilization Index
ASHRAE

Munters, 1/1/3013. Indirect and Direct Evaporative Cooling
Munters

Westaire, 1/1/2013. Two Stage Indirect/Direct Cooling
Westaire

NEEA, 01/01/2014. Total Pacific Northwest Building Stock Based on Preliminary Numbers from the 2013 Update to the CBSA
Northwest Energy Efficiency Alliance
Special Notes: Preliminary Building stock square footages from the database for the 2013 update to NEEA's Commercial Building Stock Assessment.

CADMUS, 12/21/2009. Northwest Commercial Building Stock Assessment (CBSA): Final Report
Prepared by the CADMUS Group for the Northwest Energy Efficiency Alliance

Rank & Scores

Indirect-Direct Stand Alone Evaporative Cooler

2009 HVAC TAG (#2)

Technical Advisory Group: 2009 HVAC TAG (#2)
TAG Ranking:
Average TAG Rating:
TAG Ranking Date:
TAG Rating Commentary:

Technical Score Details

TAG Technical Score: 2.4 out of 5

How significant and reliable are the energy savings?
Energy Savings Score: 2.6 Comments:
Jan 2010 Comments: 1. AC savings, but increased fan use. 2. Only in suitable locations. 3. In theory it should have good energy savings. 4. Again, cooling energy use is too low in many parts of the Northwest. How great are the non-energy advantages for adopting this technology?
Non-Energy Benefits Score: 2.1
Comments:
Jan 2010 Comments: 1. Very few non-energy benefits 2. Increased humidity levels in the space can be a problem. 3. In a proper location, the saving could be excellent. but only if it is in a proper location. 4. Depends whether you have direct or indirect system. Commercially available indirect systems may not be better than conventional systems. 5. I do not see any non-energy benefits. 6. ECER rating is interesting, especially that indirect systems are equivalent to compressor-based systems. I was not aware of that. I used to be a proponent of these systems, but not so sure anymore. 7. Higher humidity and lower control of temperature are issues. How ready are product and provider to scale up for widespread use in the Pacific Northwest?
Technology Readiness Score: 3.3
Comments:
Jan 2010 Comments: 1. Not a lot of non-energy drivers 2. Not sure 3. Some packaged products available now. Components for built-up systems are available. 4. I don't see this as a technology that will yield a lot of potential savings for BPA. Theoretically, it should, but realistically, there seems to be very low market penetration anywhere, even in areas that are dry and hot. I have been contacted by several different companies over the past two decades with products that provide indirect/direct cooling, but apparently, they are no longer in business; that's a sign! 5. Only 1 market ready direct-indirect unit exists currently. How easy is it to change to the proposed technology?
Ease of Adoption Score: 2.4
Comments:
Jan 2010 Comments: 1. 2-stage is not a simple concept and not easy to commission. 2. It has some complexities with respect to control and maintenance, but it should be easy to use. 3. Little understanding out there. 4. Indirect-direct process is not simple, but the end result is fairly straightforward. Considering all costs and all benefits, how good a purchase is this technology for the owner?
Value Score: 1.6
Comments:
Jan 2010 Comments: 1. AC savings, but increased fan use and high costs. 2. I'm guessing 10-15 or more years from what I remember of past studies we have done. 3. Not sure. 4. Depends on where installed and loads. 5. Cooling energy use in the NW is too low to yield reasonable paybacks.

Completed:
5/28/2010 12:44:57 PM
Last Edited:
3/31/2011 1:40:26 PM