# Infinia’s free-piston Stirling generator



## Prepadoodle

I've been following the development of Infinia's free-piston Stirling generator for awhile now. These units create grid quality AC electricity from heat, and are reliable, quiet, and versatile. They can run on almost any heat source, including wood fires, gasoline, diesel, natural gas, and solar.

As it stands, Infinia seems to be concentrating on larger, utility sized arrays, but they do have plans on introducing products aimed more at the consumer level. I will take a hard look at them when they do.

Infinia Stirling Technology

The product I am most interested in is the PowerDish. This uses a parabolic reflector to concentrate sunlight onto the heat end of their Stirling generator to produce 3500 Watts of AC... directly from sunlight. The PowerDish will be cheaper, smaller, and more efficient than any existing photovoltaic solution. Right now, the smallest arrays they market consist of 64 of these dishes, but the site announces plans to market single dishes soon.

The Tooele Army Depot in Utah just finished an installation of PowerDishes in June 2013, and they are operational at several other sites around the world.






I think these devices have a lot of potential for preppers. They are small, relatively inexpensive, simple, quiet, and require little or no maintenance. Infinia has been running a test engine for over 11 years with no loss of output power and no maintenance at all. You gotta love that!


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## PalmettoTree

Ok where do we get one and how much will it cost. I doubt the claims.


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## retired guard

To me it sounds intriguing lets see how it works for the Army and what the price point is. Imagine the possibilities reliable affordable electricity and the chance to outrage the Al Gore elitists who want the rest of us to live like Third World peasants while the ride their SUV's and private jets.


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## HuntingHawk

Though the Powerdish is new, they have been doing commercial installations for several years. This is the first mention by infinia of anything for the home owner.


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## HuntingHawk

Its all going to come down to the price. To start with, if they do 3500watts at 120VAC that is roughly 30amps. If they can sync two together for 240VAC at 30amps that would run most major appliances including well pumps & central heat/air conditioning.

But even with just one powerdish, still going to need to run excess power to be converted to charge batteries for night time use. Going to be easier I believe with AC from the power source then the DC from solar panels.

But I'm sure Infinina will experiment locally around Utah with home use before doing anything commercially for home use.


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## HuntingHawk

Looks like $20,000 plus delivery & installation.


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## Ripon

For what? One 3500 watt dish? That won't fly economically.



HuntingHawk said:


> Looks like $20,000 plus delivery & installation.


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## HuntingHawk

Well, I agree. But on the other hand, if you do a grid tie setup then you can get the federal & state credits which can easily cover 50% of the cost. 

With the auto tracking of both north-south as well as east-west I would say it would easily be equal to 5KW in fixed panels.


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## Ripon

That well could be, but 5k in panels is only going to run you about $4k in total cost after the rebates and such - maybe a little more for building permits which are stupid high out here.



HuntingHawk said:


> Well, I agree. But on the other hand, if you do a grid tie setup then you can get the federal & state credits which can easily cover 50% of the cost.
> 
> With the auto tracking of both north-south as well as east-west I would say it would easily be equal to 5KW in fixed panels.


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## Prepadoodle

A system that has $5k in panels will probably end up costing $10k once you add the inverter, combiner box, breakers, and all the other BOS stuff, even if it's grid tie and without batteries. The PowerDish doesn't require a most of these additional components.

Infinia isn't quite at the point where their systems are less expensive, but that's a goal. As I read it, they will ramp up to "automotive" scales once the market matures. 

Early adopters always pay a premium with any technology. A realistic projection would be $1.50/watt (and few balance of system extras) once they reach production numbers that allow them to maximize economies of scale.

I bought a Pioneer Laser Disk in 1980 and paid almost $900 for it. I can get a more capable system today for $150. I'll wait n watch and see what happens, but am super interested in this technology.


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## HuntingHawk

There are other countries with the same type system with reflector running a stirling engine. And there is a company in Az doing it also.


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## Prepadoodle

Actually, the really interesting part of this isn't so much the PowerDish, it's the Stirling engine connected to their linear alternator. The dish is just one of many ways to provide the heat it needs to run. Since it's an external combustion device, it should run on just about anything that burns.

I would love to have a silent generator that could run on gasoline, diesel, methane, ethanol, methanol, propane, oil, grease, jet fuel, or whatever else you can throw at it, probably including wood or coal. You put heat in at one end, it spews out electricity at the other, Sweet!


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## PaulS

The Stirling engine is a closed system heat engine. Yes you can use heat derived from any source to make it run but the actuality is that where that heat is placed and its definition really makes a big difference. You have to heat a specific area enough to expand whatever gas you are using as the medium but then after expending it has to cool enough to contract so it can be heated again. There are usually two pistons that are connected in a Stirling engine. A smaller piston that is heated and the larger piston that allows the mixture to cool and contract. The medium is exchanged between the two cylinders much like a refrigeration unit cycles the coolant in a heat pump or air conditioner. The gaseous medium never leaves the system. That is one of the reasons for it very low maintenance requirements. No foreign material is ever introduced so you have very little wear. The speeds are generally very low and there is little torque. 
A 10cc two cycle can make a small chain saw able to cut through 14" of green wood but a 10cc Stirling cycle would produce much less power.


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## Prepadoodle

Yes, their free-piston Stirling engine and linear alternator are permanently joined and sealed as a single unit.

The animated image HERE gives a good idea of how they are coupled (by pressure only) and how the thing works.

They also have a hybrid version which incorporates a burner so it can generate power at night. A picture of one in operations is HERE Although they provide little in the way of details, these 2 images kind of tell the basic story: You apply heat to one end and suck electricity out of the other. The hybrid unit has an integral burner, so yes, it applies the heat in a specific location. I'm sure I could make the non-hybrid version work by applying heat (from almost any source) to this same location.

The PowerDish is expensive at this time. I wonder if that 2 axis tracking is really necessary? Seems to me that's a big part of the system's cost right there. Would a simple single axis tracker work in a home application? I dunno.

Another thing I am wondering about is the mirrored dish itself. How picky is that gonna be? What if it gets covered with dust? Would I have to go wash it once a week to maintain peak efficiency? Would it be easy to scratch or etch over in a sandstorm? I dunno.

So yeah, lots of unresolved questions remain, but it's still something I intend to track as it develops. Maybe I'll volunteer to use my house as a residential test bed and get them to give me one free.


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