Objective:

Air conditioning is the single largest contributor to peak demand on electric grids and is the primary cause of grid failure resulting in blackouts. Power generators and electric air conditioners are least efficient at high ambient temperatures when cooling demand is highest, straining regional water resources and leading to increased pollution, excessive investment in standby generation capacity, and poor utilization of peaking assets. Evaporative cooling can help meet Department of Defense energy policy goals by eliminating energy waste and reducing electric demand. However, common experience is that evaporative coolers do not provide sufficient comfort, largely because of their inability to dehumidify and their poor performance during humid weather. Heat-powered dehumidifiers can extend the benefits of evaporative cooling to humid climates. The objective of this project is to demonstrate the capabilities of new high-performance liquid desiccant-dedicated outdoor air technology to enhance cooling efficiency and comfort in wet climates while substantially reducing peak demand on the power grid. This new approach is more efficient and maintainable than traditional "flooded packing" designs. The project will quantify energy and water consumption, as well as cost savings relative to air conditioners.

Technology Description:

Low-flow, direct-contact liquid-desiccant technology is a completely new dedicated outdoor air conditioning approach that provides superior dehumidification. One 3,000-cfm unit provides more than 10 tons of latent cooling (approximately 15 gal/hr), freeing up sensible capacity in other air conditioners or chillers and letting them run more efficiently with higher evaporator or chilled water temperatures. The only electrical input to the system runs fans and small pumps resulting in cooling energy efficiency ratios (EER) over 65. EER is the generally accepted metric for comparison of cooling equipment performance. It is the ratio of cooling capacity (Btu/h) to electrical input (kW). As a reference, the current Department of Energy standard for seasonal EER is 13, and its long-term goal is 20. Thermal energy for the liquid-desiccant air conditioner can be recovered from engine gensets, microturbines, turbines, fuel cells, solar collectors, or other processes with recoverable heat between 150°F and 300°F. Dehumidification energy is converted to heat, which can be rejected to a cooling tower, drycooler, or groundwater loop.

Expected Benefits:

Peak power demand reductions in excess of 20% are possible with proportionate reductions in demand charges. This is expected to reduce strain on the grid, increase electric delivery reliability, and reduce projected service expansion costs. Air conditioning energy reductions of 25% are expected for liquid-dessicant technology when using solar or recovered waste heat as the primary energy input. (Anticipated Project Completion - 2011)

Principal Investigator:
Dr. Eric Kozubal
National Renewable Energy Laboratory
1617 Cole Boulevard
Golden, CO 80401
Telephone: (303) 384-6155
Fax: (303) 384-7540
E-mail: eric.kozubal@nrel.gov

DoD Liaison:

Mr. Bruce Nielsen
U.S. Air Force Research Laboratory
139 Barnes Drive
Suite 2, MS 3D
Tyndall Air Force Base, FL 32403-5323
Telephone: (850) 283-6227
Fax: (850) 283-6064
E-mail: bruce.nielsen@tyndall.af.mil