Sustainable stand alone blast freeze system

New blast freeze concept

Although a new and emerging technology, stand alone solar blast freeze systems are available on the market. A drawback of these systems is that they utilize electrical battery storage to be able to run when there is no sun available. These batteries take up space, limit capacity and are costly due to frequent replacements. TNO and partners have taken a containerized solar powered blast freeze system and modified the design by exchanging the battery storage with phase change materials (PCM). The buffer is therefore not electrical energy but cold energy stored in the PCM materials, eliminating a large percentage of batteries required as well as reducing the need for back up generators.

PCM storage design

The PCM system is used to store excess cold energy at very low temperature (-40 degrees C). During the day the blast freeze unit is fully powered by the sun and operated. The cooling engine provides energy for the blast freeze operation as well as excess to charge the PCM materials. At night or during times of low solar availability energy for the blast freeze operation is taken from these PCM buffers. In addition the PCM buffers are used for storing (cooling) the blast freezed product.

System characteristics

The current design is based on a single 20 ft container and has a capacity of 1-2 ton of product. Our idea is that the system is transported to the farm location, where the solar panels are folded out or placed to the sides. The product is harvested and processed directly in the system. More capacity can be added due to the modularity of the containers. An additional storage container can also be provided depending on the amount of harvested product. This container can be a completely insulated container for storage only with a small cooling engine/PCM storage buffer to keep the product at -20 degrees C. The current calculated return on investment for a base case in Kenya for fish farming is around 7 years.

Current status

We have done extensive modelling and design for this system with an industrial partner. For further development and commercialisation we are looking for other industrial partners to join, preferably active in the commercial food chain in developing countries on processing and cooling/freezing.