Item ID: 88
Residential Water-Cooled Condenser
Residential HVAC Condensing Unit: Water-Cooled vs. Air-Cooled
Residential sized water cooled condenser air conditioning technology has been available for several years. Laboratory and field testing of several generations documented the efficiency potential of this technology. Water Cooled condenser technology offers significant electric demand reduction potential.
Compressor-driven air conditioners are commonly used for residential cooling in inland Pacific Northwest locations like Boise, Idaho and the Tri Cities area of Washington. Almost all of them are air cooled and work inefficiently to push heat into hot, outside air. There are several approaches to reducing this problem in hot, dry climates. One is to use evaporative pre-cooling to reduce the compressor load. Evaporatively cooled condensers spray water on the condenser to sensibly cool the coil and remove additional heat as the water boils off of the coils. The evaporated water exhausts from the condenser fan with a resulting water consumption of 1 to 3 gallons per hour per ton of cooling (Navigant, for the US DOE Building Technologies Office) (Navigant Consulting, 2012). Additional water treatment may be necessary to maintain performance, depending upon local water purity and treatment processes.
Another approach is to use water to absorb heat from the evaporator coil. This latter approach - “residential cooling tower” technology - is an option for energy and peak demand reduction in hot, dry interior climates. Benefits include enhanced cooling capacity in addition to increased cooling efficiency--especially at higher temperatures.
McQuay markets packaged equipment with evaporative cooled condensers and claims a 27% to 40% cooling energy savings for various U.S. climates (Navigant Consulting, 2012).
Energy Savings: 30%
Energy Savings Rating:
Concept validated: What's this?
|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.|
Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:
Simple Payback = Incremental First Cost / Annual Savings
The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.
For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.
For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.
Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.
The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.