Western Cooling Challenge Field Test - Advanced Indirect Evaporative Technologies

Energy used for air conditioning in buildings necessitates massive investments in electric generation and distribution capacity, draws on a substantial portion of our global fuel extraction, and subsequently contributes to a host of environmental, political, and economic challenges. There is a monumental need to improve efficiency for air-conditioning. This report explores one technology opportunity that has previously demonstrated 40% on-peak demand savings for cooling in California climate conditions. The objective of this study is to conduct field evaluations of Indirect Evaporative Coolers (IECs) in California Climate Zone 8. IECs were installed at two different cellular sites in the cities of Cudahy, CA and Placentia, CA during the summer of 2014. The evaluation studied real-world equipment operation and developed characterizations of the overall system performance and energy efficiency across a range of operating conditions. The study is designed to investigate performance characteristics that cannot be captured by steady-state laboratory testing. This evaluation carefully disaggregates performance in each mode of operation to consider efficiency of each system state, and to investigate the implications of the control strategies and field-selected settings that were applied. Characteristic performance metrics for the IECs were calculated from data collected over the month of September 2014. During September 2014, both field test sites experienced typical cooling season conditions with average outside air temperatures above 75°F. Tables 1 and 2 summarize the results for the IECs in five degree temperature bins ranging from 80 – 105°F. The IECs tested use 100% Outside Air (OA) which makes it difficult to determine the true value of the room cooling metrics. For this study, the research team used an ideal room temperature of 80°F. The research team recognizes that 80°F is not always representative of the return air temperature seen by the baseline, but for comparison between the systems positive room cooling credit for the difference between the supply air temperature and 80°F. The results only focus on sensible cooling metrics. The company running the cell site has alarms for high humidity situations, but none of the Heating, Ventilating, and Air Conditioning (HVAC) equipment is set up to control the humidity in the space. It is important to remember that with IECs, the room cooling capacity decreases with an increase in outside air temperature. Therefore, in certain applications, IECs are not suited for a one-to-one replacement with conventional direct expansion (DX) equipment. However, IECs will still provide substantial savings if used to partially replace or offset DX cooling. The research team recommends IECs as an impactful measure to reduce energy consumption and peak demand for cooling in commercial buildings. However, we also recommend that utility efficiency programs, and other efforts to advance the technology, should remain cognizant of some of the challenges that can hinder performance and limit the persistence of savings. It is especially important that any installation of this measure be paired with a quality service agreement. In our observation, the current lack of industry familiarity with the technology can result in untimely failure or abandonment of the measure. For example, IECs use 100% outside air which typical results in filter changes on a shorter interval than conventional systems. If possible, the research team suggests that new systems be installed with a guaranteed system performance for set period of time. This might necessitate a different type of capital and incentive structure but will address some of the challenges that currently plague performance for HVAC equipment in commercial buildings. In addition, IEC equipment needs to be drained to prevent freezing of water pipes in the winter. California Climate Zone 8 rarely frosts or freezes which negated the need for a seasonal service in this field test. The research team also recommends the development of utility programs and other efforts that can support the broader adoption of these technologies. Such programs should give significant weight to the value of peak demand reduction, and the fact that demand reduction for cooling offsets the need for increased electric generation capacity. The market penetration for IECs is still small and the benefits of such an incentive or rebate program will help end-users with the larger up-front costs. Finally, the research team recommends that further research be conducted to translate the characteristic measurements from this study into a calibrated model for an indirect evaporative system. The results presented in this report stand as particular examples, but the characteristic observations allow for development and validation of a general map for the technology that can be applied to other scenarios through building energy modeling. This model can be used to simulate savings across an array of climates and applications. It can also help programs target strategic savings opportunities, identify approaches to optimize control of IECs, and inform the development of design guidelines to support broad and successful application of the measure.