XPRIZE Off-Grid Refrigeration

In remote locations, stand-alone systems can be more cost-effective than extending a power line to the electricity grid. But these systems are also used by people who live near the grid and wish to obtain independence from the power provider or demonstrate a commitment to non-polluting energy sources.

This prize would challenge teams to produce low cost, self-powered clean appliances accessible to remote, off-grid communities. For example, appliances that work well on storable power or a solar refrigerator.

We would like to learn from you:

  • Is this an audacious prize competition?
  • What are the innovation gaps in this area?
  • What would the winning team need to do?
  • What would be audacious but achievable targets?
  • What is the expected impact of this prize?

Hi @gyyang and @adventureashr - In your views is this an audacious prize idea? If yes, what should be an audacious and achievable targets for this prize and what the wining team should demonstrate?

Hi @danfortin, @nemet and @josephjjames - In your views what are the innovations gaps in self-powered clean appliances space? If we launch a prize in this space would it be audacious enough? If so, what would be the Impact of such a prize?

We’re wordsmithing what we call the “winning-team-will statement” for this prize: a succinct description of what a competing team would need to do to win.

Here’s the current version, and I’d appreciate your thoughts:
Demonstrate the week-long, uninterrupted function of an off-grid, clean, autonomous/easy-to-use, and affordable refrigerators.

The next step are drafting the testing and judging criteria for the prize. Here’s what we have so far:

  • Target user: remote, energy-starved communities
  • Develop a household/community refrigerator and/or community icemakers
  • Demonstrate variable length scales, scalability, throughout the competition?
    • E.g., from 100 families (semifinals) to 300 families (finals); from 1 household (semifinals) to community-scale (finals)
  • Low-cost and cheap to maintain
    • If household refrigerator: lifecycle cost to own and operate less than $5/month
    • If icemaker: 1000 kg/day at a cost of less than $0.03/kg
  • Works reliably off-grid
  • Using renewable energy resources
  • High efficiency: must meet the requirements of aspirational middle class consumers in target countries and not seen as a poor and cheap alternative.
  • Autonomous, functional 24/7, demonstrate a week-long activity.
  • Avoid the use of HFC’s (hydrofluorocarbons)
  • Robust, simple to use, maintain, and transport: transportable in Toyota HiLux Pickup
  • Lifetime: 10 years

@danmiller, @zhangx, @wxn07, @Brad, @oren - We would love to have your feedback on the wining team will statement and testing and judging criteria mentioned above.

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Hi @AAM_AAU, @ikuzle. @Poshgero, @gyyang - Given your knowledge and expertise in this area, we feel you might be able to advise us on this prize design. It would be nice to have your feedback on the above-mentioned prize parameters. Thanks.

Hi @akb, @b0bbybaldi, @agval and @carlbozzuto - We would like to have your inputs and feedback on this prize design and metrics.

@Shashi in my experience this is too niche of a market right now outside of people interested in energy or electricity. Therefore, mostly a business problem, as such I don’t think a prize for it is worth it yet, the impact would be quite limited.

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The scale seems too large (100 - 300 families / installations). That would potentially exclude a small team with a great idea.

The week long testing duration might be too short. For example, a solar powered solution might work in the peak of summer, but how will it perform in the darkest days of winter? Such a solution probably needs to demonstrate its seasonal energy storage. We could extend the duration to a year to cover all seasons and a range of environmental conditions; or have multiple shorter durations throughout the year to catch all typical weather conditions. (Or run in a controlled environment that simulates all conditions.)

[I’m assuming the costs have been set at a challenging level, far below conventional costs - to make it worthy of an XPRIZE.]

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Hi @Eti - Any thoughts on the above two comments?

Based on the advice of our founder and chairman, Peter Diamandis and other experts, we have revised the prize metrics.

Following is the revised wining-team-will-statement:
Demonstrate the week-long, reliable operation of off-grid, clean (GWP = 0) household and community-scale refrigerators, reaching temperatures of 0ºF and 40°F (-18ºC-4°C), operating on ≤5 kW/month and for ≤$5/month.

Prize Purse: $7M

Timeline: 3 Years

Following is a draft testing and judging criteria for this prize:

  • For an off-grid, energy-starved community in sub-Saharan Africa or Southeast Asia. Defining:

    • Hours of light available: 12 hours
    • High ambient temperatures: 32ºC
    • Humidity 75%
  • Develop a 100L, off-grid, self-sufficient, solar-powered refrigerator module

    • Must use climate-friendly alternatives to HFC
  • Capable of reaching temperatures of: refrigeration ≤40°F (4°C), freezer: 0°F (-18°C)

  • Transport the system 5 miles, using a standard pickup truck: 174-193″ L x 67″ W x 61-67″ H, and then install.

  • Demonstrate a week-long, 24/7 function, including a demonstration of spontaneous 8h disruption to service.

  • Scalability: demonstrate connectivity between two units

  • Low-cost and cheap to maintain, a module (household scale) cost:

    • Upfront cost: Cheaper than a solar DC refrigerator, ≤$2000.
    • Lifecycle cost to own and operate less than $5/month
  • Lifetime: 15 years

@akb, @marz62, @Sev - We would love to have your feedback on the revised wining-team-will statement, prize purse, timeline and the testing and judging criteria.


Now that’s a considerable set of criteria! I guess there’s a reason they call it an ‘innovation challenge’.

A solution/system that can meet both the refrigeration and freezing criteria (temperatures) will be tricky…but probably doable (with some very clever low-tech design/engineering).

I have one question/issue with the freezer temperature criterium: “0°F (-18°C)” this seems extreme to me (note: ‘freezing’ in Fahrenheit = 32°, which is 0° C)…is that freezing temperature correct? If so, how was this determined?

At first glance, the scalability criterium (linking of 2 units) is unclear to me – does this mean either two freezers or two fridges, or, one freezer and one fridge? This criterium may prove to be the most challenging (due to the temperature differential) of all.

The duration/time factor (week long, 24/7, with demo of 8 hour disruption to service) will add to the difficulty factor; I think some clarification of the ‘8 hour disruption to service’ is needed: disruption to what/which service? The existing grid’s electrical power feed? Why 8 hours (is this the time for fresh meat or dairy to spoil?). CLARIFY PLEASE.

How was the ‘100 liter’ storage capacity determined? Is that the total capacity (freeze and fridge) or for one module (freezer OR fridge)? Is this the estimated cold food storage space needed for a family of a given size? Just one person?

The foregoing being said, I understand most all of the criteria and their (probable) rationales for inclusion (though the ‘life time’ benchmark of 15 years will need to be hypothetical [extrapolated from the prototype demo] and/or modeled by computer simulation using the demo’s parameters).


Hi @Shashi - that looks good: quantified objectives to aim for.

There might be a typo in “operating on ≤5 kW/month” - the h is missing for units of energy per month. It should probably be ≤5 kWh/month [?].

(The energy demand of a fridge is partly influenced by how often the door is opened and how long it is left open. So that should be controlled / replicated for each participant’s evaluation.)

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Thank you @akb. Indeed it’s ≤5kWh/month. Or rather, was, the current advice is to remove this criterion for that we will get different results for the different use cases. Also, and related to it, the efficiency of this self-sufficient refrigeration module was deemed redundant due to the cost criteria.

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Thank you @marz62, I’ll give some detail that can hopefully clarify.

  • Yes, the refrigerator is to provide both functions; the temperatures are the recommended temperatures by FDA for perishable products; as well as the fall in the range of temperature required for Pfizer vaccines.

  • Connectivity of the modules is going to be assessed for scalability; aka scaling up to community-scale is via connectivity of modules, rather than expanding them. It was also determined as more effective in the protection of food items (minimize exposure to ambient air by having many smaller units)

  • Module size; 100L is total capacity determined by the required size of the target user, which is a household (family of 5); it’s based on an evaluation that can be found in this paper (see fig. 7)

  • Re disruption to service. This is a self-sufficient module, so not the power grid; disruption to service means disruption to cooling functions (any failure that may cause this). 8h is overnight, however, we’re also considering 2h, as this is the max time recommended (by FDA) to leave perishable outside of refrigeration.

  • Lifetime 15 years: this is the standard avg. lifetime of appliances indicating the upper limit lifetime in lab conditions.


@Eti - thanks for the clarifications/explanations…it seems this XPrize candidate has been well researched!

Thank you for the opportunity to provide feedback. Here are my thoughts - I hope they’re useful:

  1. For “climate-friendly alternatives to HFC” - is it possible to quantify the improvement needed over current HFCs? For example, the coolant must create X amount or percentage less harmful emissions compared to HFCs.

  2. Does the refrigeration need to achieve both 40 degrees for refrigeration AND 0 degrees for freezer or either. You might specify that the unit must do both just to be very clear.

  3. The durability target might be too ambitious considering the need it is filling. Consumer reports state that consumer fridges in the US have a median life of 10 years: Most and Least Reliable Refrigerator Brands - Consumer Reports
    Using that metric as a benchmark, maybe have a durability target of 5 or 10 years instead of 15?

I’m hesitant to advocate for lowering the bar, but another alternative might be to stick with the 15 year lifetime criteria unless the solver can demonstrate that at least 80 percent of the materials used in the unit can have a sustainable end of product lifecycle (e.g: recyclable, compostable, etc.) If that criteria is met, then the bar can be lowered to a life of 7.5 years or something like that.

  1. The “scalability” criteria sounds more like a compatibility criteria if the need is to demonstrate connectivity between devices/units.

  2. Go with the clear and objective upfront cost of $2,000 and take out cheaper than solar DC fridge in case someone wants to point to a DC fridge that costs $3,000 and claims it meets the criteria as worded/interpreted.

Thank you for reading.

Kind Regards,


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The number of issues off-grid refrigeration can address, from safe water, public health, nutrition and food insecurity underscores the value here. Targets should take account of state-of-play of research in India, especially that undertaken with, by, or for the Tata organization. An X-Prize targeted here, should be additive to current research targets.

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Thank you for all your inputs and feedback. Based on your and Brain Trust members inputs and feedback following is the final version of this prize sketch:

Winning Team Will Statement: Demonstrate the week-long reliable operation of an off-grid, standalone, climate-friendly 100L refrigerator, capable of cooling between -18ºC and 4°C, for ≤$6.5/month.

Prize Purse: $7M

Timeline: 3 years

Testing & Judging:

  • For an off-grid environment with 12 hours/d of light, 32ºC, and 75% humidity
  • Develop a 100L, off-grid, standalone, renewably-powered refrigerator, using climate-friendly alternatives to HFC
  • Cooling to temperatures of ≤-18ºC (freezer) and ≤4°C (refrigerator)
  • Transport it 10km safely, using a standard pickup truck, and install
  • Reliably operate 24/7 for a week, including through a spontaneous 4h disruption to service, keeping temperature ≤4°C
  • At the cost of ≤$6.5/month and a 10-year lifetime.
  • At the highest scalability and safety scores

Hi @b0bbybaldi, @akb, @marz62, @lancemcneill, @SpacePlaceCanada - Thank you for your inputs and feedback. Above is the final version of this prize sketch.