Grantee Research Project Results
Final Report: Waste-Heat Driven Absorption Transport Refrigerator
EPA Contract Number: 68D98131Title: Waste-Heat Driven Absorption Transport Refrigerator
Investigators: Garrabrant, Michael A.
Small Business: NRG Solutions Inc.
EPA Contact: Richards, April
Phase: I
Project Period: September 1, 1998 through March 1, 1999
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1998) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Summary/Accomplishments (Outputs/Outcomes):
An exhaust energy powered Absorption Transport Refrigerator (ATR) is proposed that can provide a controlled, below ambient environment to a refrigerated trailer using significantly less fuel than current technology. An ATR utilizes an absorption refrigeration cycle that is powered primarily by waste heat from the transport vehicle (truck) engine. Supplemental fuel is required only during periods of no or reduced truck engine load. Current technology utilizes a vapor-compression refrigeration system consisting of a trailer mounted refrigeration unit with the compressor driven by a small combustion engine (typically diesel). Capacities of these systems range from 20,000 - 50,000 Btu/hr (5.9 - 14.6 kW). Primary disadvantages of diesel/gas engine driven systems include:1. Low combustion engine operating efficiencies of approximately 35%.
2.
Combustion of gasoline or diesel fuel, contributing to air pollution, greenhouse
effects, and the national trade imbalance. Over 350,000 refrigerated trailers
are in use in the U.S. today, consuming more than 245 million gallons of fuel
per year.
3. Use of environmentally unfriendly CFC or HCFC refrigerants.
4. High number of moving parts requiring extensive maintenance and
environmentally unfriendly lubricants and coolants.
Research Objectives: The focus of the Phase I research centered on two aspects of the proposed system with the most technical risk:
1. Removing the waste energy from the truck engine exhaust stream and
transferring to the ATR with a reasonably sized, reasonably priced, low pressure
loss heat exchanger.
2. Transferring the collected energy to the
refrigeration cycle in a manner that provides high concentration refrigerant
vapor to the refrigeration cycle.
Proof-of-concept testing on an exhaust gas heat exchanger (EGHX) and a novel plate-fin, hydronically heated ammonia vapor generator was competed. These two components constitute the majority of the technical risk involved in the development of the proposed system. The EGHX must remove a large amount of energy from a gas stream without a large pressure loss penalty (which would reduce the efficiency of the truck engine), and be easily installed in the exhaust system of a large semi-truck. The generator must be able to generate as much vapor as possible using the available waste energy stream in order to minimize the amount of auxiliary heat required and do so while maintaining the solution temperature and concentration profiles required for good cycle performance.
Results: The conceptual exhaust gas heat exchanger (EGHX) and hydronically heated generator designs were constructed, installed into an absorption cycle test loop, and tested over a range of flue gas flow rates and inlet temperatures. Data collected during the testing was used to validate and calibrate the design models. Both were tested as an integrated pair that provided the energy input to an actual absorption cycle in which a refrigerated load was obtained.
Refrigeration capacities up to 38,000 Btu/hr (11.1 kW) and 60% efficiencies were produced by the prototype EGHX-Generator pair driving a full scale absorption cycle test loop. Performance of the prototype EGHX matched the predicted performance within 3%. Flue gas side pressure loss was 2" H2O at the tested conditions and predicted to be well less than 3" at the targeted ATR cycle conditions. The prototype EGHX was 52" long (48" of active fin) and 9.5" in diameter, a size approximating current mufflers for large trucks. No design changes or re-work will be required for Phase II research activities. The compact generator (3.5" x 5.5" x 30") effectively converted the inlet energy into high purity refrigerant vapor. Overall generator effectiveness was 10-15% lower than originally predicted and two minor fluid dynamics problems were noted. A slightly longer generator, with a modified fluid routing will be fabricated for Phase II research activities.
Commercialization Potential: The total U.S. market for large trailer transport refrigeration units (approximately 1/2 of the worldwide market) is over 35,000 units ($700 million @ $20,000 average price). ATR technology will result in per trailer annual fuel savings up to $2,000 per year (depending upon miles driven and the cost of fuel) with initial investment costs equal to or less than current technology. ATRs, with few moving parts, require less maintenance, run quieter, and do not require CFC or HCFC refrigerants. The trucking industry, while conservative, is also very price competitive, and cost reduction technologies more readily accepted.
Other Applications: While designed specifically for transport refrigeration, the technology developed during this project can be applied to any application requiring refrigeration in which a high temperature waste heat stream is available such as:
1. stationary engines driving chillers in refrigerated warehouses.
2.
stationary engines providing electrical power production in hospitals or large
industries.
3. industrial processes where waste heat is available at one end
and cooling required at the other.
4. remote areas using engine power to
generate electricity.
The EGHX could be applied as a stand-alone heat recovery device for any number of applications and the hydronically heated generator is ideal for solar powered refrigeration systems.
Supplemental Keywords:
Scientific Discipline, Air, Sustainable Industry/Business, cleaner production/pollution prevention, Technology for Sustainable Environment, New/Innovative technologies, Engineering, Chemistry, & Physics, refrigeration, waste to fuel conversion, Adsorption Transport Refrigerator, air pollution, emissions, energy efficiency, energy technology, alternative energy source, innovative technology, alternative refrigerants, innovative technologies, air emissionsThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.