Configurable Array of 3D-Printed Lubrication-Free Turbocompressors for High Temperature Industrial Heat Pump Applications

This proposal is for the development of a new class of configurable, modular, maintenance-free and cost-effective Industrial Heat Pump (IHP) technology to transfer heat from a source at well below 20°C to above a target sink temperature of 200°C. The concept is based on the grouping of standardized heat pump modules assembled into compact arrays of independent skid-mounted units that are thermally coupled and operate in unison to achieve the desired temperature lift and heating requirement. A typical IHP array will consist of three different temperature tier modules (low, mid, and high temperatures), thermally coupled via heat exchangers, and with each tier potentially operating with a different refrigerant (like R1336mzz(Z) on the side coupled to the cool source, R601 in the mid region, and steam on the side coupled to the hot sink). At the core of these modules will be state of the art single-shaft one- or two-stage turbocompressor designs, using lubrication-free compliant foil bearings, enabling robust and hermetic operation at all temperatures. Since compliant foil bearings undergo practically no wear during their operation, a minimum preventative mean time between maintenance (MTBM) of 40,000 hours and an overall life well in excess of 120,000 hours are expected, easily meeting or surpassing the life of current IHPs. By standardizing the interchangeable turbocompressor units, it is expected that the high configurability of the proposed compression system will provide IHP integrators with freedom to explore multi-stage cycle optimizations without compromises due to compressor availability or other design constraints. Design configurability for different capacities, refrigerants, and operating conditions will be achieved through use of an optimization algorithm to determine the minimum electrical power and number of individual units required for an array to satisfy a given IHP’s heat load. It is envisioned that a small number of building block turbocompressors of fixed nominal capacities (e.g., 3 kW, 10 kW, 50 kW, and 100 kW) should suffice to power IHP arrays in support a broad range of IHP requirements. For example, assuming a COP of 4, an array of three modular IHPs, each with three low cost 50 kW modules would be capable of supplying a 510 TR (ton of refrigeration) system. A minimal level of compressor component customization around standardized systems is expected and will be enabled by the use of recently implemented state of the art low cost additive manufacturing (or 3D printing) methods. The most significant benefit of the proposed technology is its potential to reduce the economic cost of heating by approximately 50% and the environmental cost of CO2 release by 38% with respect to heating with natural gas, while assuming that the electricity used to power the system is still produced by natural gas combustion. Greater reduction would be achieved if the system were powered with a fraction of energy from clean/green sources. The Phase I effort will deliver all analysis/modeling required for a complete preliminary design of a three-module IHP 8.5 to 9 tons of refrigeration demonstration prototype with a COP of 4 and capable of delivering heat from 20°C to 200°C. The effort will include the design of three individual IHP modules for operation in series, powered by 3 kW one- or two-stage turbocompressor units using low GWP/ODP refrigerants like R1336mzz(Z), R601, steam, or similar. All balance of plant and supporting components will be designed or selected, including heat exchangers, expansion valves, tanks, and ancillary hardware to integrate the individual IHP modules. The Phase I design will also include the configuration of the module skids and their means of interconnection. The scalability (and potential limitations) of the concept to achieve MW-class IHP capacities will be explored. Based on the Phase I effort, integration of a three module IHP would be conducted during an eventual Phase II program. During Phase II, laboratory testing of the system would also be conducted, with the goal of demonstrating that the proposed technology can reach a TRL-6.