The THEAC-25 convert solar heat or industrial waste heat directly into cold for building, utility or process cooling based on thermoacoustic energy conversion as underlying technology.
Market introduction of the THEAC-25 will be performed by Soundenergy B.V. (soundenergy.nl an award winning start-up established in 2015. Aster is co-founder and shareholder and is taking care of the R&D activities for Soundenergy B.V. This year focus was on the build and test of de pre-production prototype, providing up to 25kW of cooling power when solar or waste heat with a temperature the range 100-200°C is applied.
The THEAC-25 is based on Aster’s multi-stage traveling wave technology and is assembled from two thermoacoustic heat engine stages and two thermoacoustic heat pump stages sharing an common acoustic traveling wave resonance and feedback loop.
From the application point of view, the THEAC is a waste or solar heat driven heat pump, requiring three external circuits to be connected to the application. For one of the possible applications, which is solar heat powered cooling of a building in combination with vacuum tube solar collectors as heat source, this is depicted schematically below.
The dashed box represent the hardware and functionality of the THEAC-25. The actual prototype of a heat driven 25kW cooling system currently under test is shown below.
In this test rig all pressure vessels, containing the thermoacoustic core (heat exchangers and regenerator), are equipped with flanges and vessels are positioned vertically for reason of simple access and experimenting.
In the commercial version these flanges are obsolete and removed for saving weight and cost. Furthermore all vessels will be positioned horizontally by default to reduce system height. Finally the THEAC-25 will fit into a box of 3.5m x 3.5m x 0.6m.
This commercial version will be pre-assembled in a frame, including all internal piping and subsystems, providing the customer with the three connections for heat supply, heat sink and cold.
The first tests showed an onset input temperature less than 50°C. Above this onset temperature, acoustic loop power and cooling power rise proportional with input temperature difference applied to the heat engine stages.
However, within the design and test temperature of 160°C applied, a cooling power of 25kW is not reached yet due to the under performance of the heat exchangers (aluminium brazed finned tube) exchangers in combination with thermal oil, causing the TA process effectively runs at less than 120°C.
For that reason the commercial versions will make use of 2-phase heat transfer (looped heat pipe) reducing the temperature loss between heat source and thermoacoustic process drastically.
Production of the THEAC-25 by Soundenergy B.V. is planned to start mid 2017 for industrial waste heat recovery applications in industry, followed by solar heat driven cooling in 2018 for more southern countries.