Prototype Thermoelectric Heat Pump

[EatenByLimestone]

Replace the AC compressor with a DC compressor. I didn't mean to imply it is a DIY project but it is SOTS.
Generally done on boats but makes sense for off grid too. On boats the "box" is custom made, the goal being much thicker insulation and a top opening to reduce energy input.
The same rational applies for off grid usage as well.

There are lots of people using chest freezers as refrigerators. They run them off an external thermostat on a probe. If I remember correctly it's really popular with the home brewing guys. You probably don't even have to run it off a dc compressor to see big gains.

 

[Corey]

Given the electricity and power constraints of this project, a TEC is probably the absolute worst solution. As mentioned, they are among the lowest efficiency, highest cost per unit of cooling, and hardest to integrate into a 'home cooling' type scenario as the hot side is generally only ~1/8" away from the cold side...very hard to reject heat 'outdoors' and keep cool 'in'. A DC compressor might be a bit better, but you're still limited by efficiency of gas-compression refrigeration and the need to supply a large amount of relatively high grade power as 'electricity'.

A much better solution would be an absorption chiller - these have already been used for decades as 'gas refrigerators' in RVs, camps, or any place where electricity is in short supply, but the ability to make low grade 'heat' is available. A step up would be an adsorption chiller - which generally represent newer technology. This could run on items as simple as silica gel and water, and use a solar concentrator to generate heat. I've seen quotes putting power consumption at 0.4KW / 180 tons of refrigeration, though on the downside, the 0.4KW is running vacuum and circulation pumps, so it most likely doesn't scale linearly...you'd probably still need a few hundred watts, even if only generating a few dozen tons of cooling. Conversely, the reject heat of the system is coming out as hot water, so your DHW needs should be satisfied, too.

 

[DBoon]

Battery power storage is self defeating, but is the cheapest way to go at present- capacitor storage ( what power companies use) is where development and new tech will be eventually - at this time, unless you have dang near unlimited funds, it is out of reach cost wise of Mr.Avg. I do not have lifetime # for capacitors but efficiency and # cycles far exceed any battery currently available or in design.

Utility use of capacitors is for power factor correction, not energy storage - completely different. While capacitors have become much more energy dense in the last 25 years, a battery is still more energy dense. Supercapacitors are used primarily for loads that need high peak currents, and the fast discharge/re-charge is a good application for them. The premium version of the new Mazda3 uses a supercap for this purpose.