This Small Business Innovation Research (SBIR) Phase I project will build and operate a proof-of-concept unit of a thermally activated heat pump with a higher efficiency than the commercial LiBr absorption chiller. Such heat pumps, which can be used for both cooling and heating, are cheaper to build, easier to operate, has a smaller footprint, and are expected to last longer than the commercial LiBr chillers. They can be driven by low level heat from low cost solar collectors. The materials in the system are basically non-toxic. Currently, commercialization of the less efficient and more costly aqua-ammonia absorption heat pump for heating is being considered by DOE although such systems are not suitable for using heat as low as 70o C.

The broader/commercial impacts of this research are reducing the fuel consumption for heating by more than 45% from the conventional furnaces, enabling utilization of heat from low cost solar collectors, engine cooling-water, or other low level heat as low as 70o C for air conditioning and/or heating with greater than 100% ?thermal efficiency?. Wide use of this technology can potentially save 5-10% of the energy used in this country and greatly reduce the summer electricity demand peaks.

Project Report

From the simulation study we discovered that the thermally activated heat pump as described in our Phase I proposal can be further simplified by eliminating some components in the top half of the generator and its connection with the rest of the system and shorten the height of the generator, which will not only result in lower cost of construction but also makes the efficiency of the system higher. This is enabled by using a specific parameter of the refrigerant in a specific location in the process flowsheet. We also discovered based on simulation that the absorber can also be shortened without having significant impact on the performance of the system, and that the simplified simulation method we used earlier is accurate enough for most purposes. We discovered that two other components in the family of solvents we chose are worth further study since they have certain better features than the one chosen in the proposal, and the thermal efficiency values of the systems with these solvents as the base absorbent are similar. We identified another large, likely multi-billion dollar, application for the technology. We completed the detailed design of the proof-of-concept unit, identified the machine shops capable of making specially designed components and vendors carrying the other components, and made/purchased all the components needed. We put together the proof-of-concept unit. We ran the proof-of-concept unit, successfully demonstrating that such a system works as a thermally activated heat pump. The results seem to fit well with our simulation results. We identified several areas for improvement, which we will incorporate in future modifications. From running the proof-of-concept unit, we developed a control strategy that will allow smoother operation and quick startup of the system, and allow for intermittent heat supply.

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