Stirling Cooler - Fridge / Freezer project
Posted: Fri Jun 26, 2009 5:35 pm
Hi all
New member here.
I am currently living aboard a 36 foot sailboat in the Caribbean with my wife and cocker spaniel. We run the boat completely off renewable energy with wind and solar. For the past year or so, our fridge has been a Coleman Stirling Cooler which has proven very reliable and power efficient, but rather small. I am now in the process of building a larger fridge / freezer with 6 inches of insulation and wish to use the Stirling engine from the Coleman cooler.
In the Coleman cooler, heat transfer from the box to the cold side of the Stirling engine is by CO2 thermosyphon in copper pipes. However, this will be difficult to replicate in a homemade box, and the thermosyphon has other issues on a heeling sailboat. In our new box we will be using a large heatsink on the cold side of the Stirling engine to absorb heat from the box. One problem with this is that the heatsink will frost up gradually and as it frosts up, efficiency will be reduced. The recommendation from Jesse Edwards at Globalcooling.com is to use 12V heating elements on the heatsink and run a daily (or nightly) defrost cycle.
I need one or two 12V strip heaters to heat the heatsinks to melt away the frost. I'm thinking two strip heaters around 20 - 30 W should do it. They must be flat strip heaters without fins which can be bolted direct to the heat sinks. The object is to heat the heat sinks quickly while heating the freezer compartment as little as possible. Once average run time etc. has been figured out, the strip heaters will be run on a timer which will switch the strip heaters on once per night while switching the fridge off, then turn the fridge back on once the frost has been removed.
Any ideas on a source for the 12V strip heaters would be most welcome. The ones I have found online are all 120 or 240V.
Owen, Donna and Sparky
Yacht Magic
St Maarten
Netherlands Antilles
New member here.
I am currently living aboard a 36 foot sailboat in the Caribbean with my wife and cocker spaniel. We run the boat completely off renewable energy with wind and solar. For the past year or so, our fridge has been a Coleman Stirling Cooler which has proven very reliable and power efficient, but rather small. I am now in the process of building a larger fridge / freezer with 6 inches of insulation and wish to use the Stirling engine from the Coleman cooler.
In the Coleman cooler, heat transfer from the box to the cold side of the Stirling engine is by CO2 thermosyphon in copper pipes. However, this will be difficult to replicate in a homemade box, and the thermosyphon has other issues on a heeling sailboat. In our new box we will be using a large heatsink on the cold side of the Stirling engine to absorb heat from the box. One problem with this is that the heatsink will frost up gradually and as it frosts up, efficiency will be reduced. The recommendation from Jesse Edwards at Globalcooling.com is to use 12V heating elements on the heatsink and run a daily (or nightly) defrost cycle.
I need one or two 12V strip heaters to heat the heatsinks to melt away the frost. I'm thinking two strip heaters around 20 - 30 W should do it. They must be flat strip heaters without fins which can be bolted direct to the heat sinks. The object is to heat the heat sinks quickly while heating the freezer compartment as little as possible. Once average run time etc. has been figured out, the strip heaters will be run on a timer which will switch the strip heaters on once per night while switching the fridge off, then turn the fridge back on once the frost has been removed.
Any ideas on a source for the 12V strip heaters would be most welcome. The ones I have found online are all 120 or 240V.
Owen, Donna and Sparky
Yacht Magic
St Maarten
Netherlands Antilles