Domestic Geothermal Stirling Power Unit

Description

This is an idea for starting a project for 2015HackadayPrize so anyone can inspire from it...

Nowadays most land has been categorized regarding hydrological and geological layers, and we are able to tap fresh water near surface as well as deep hot water sources.
That makes convenient to find two depths where a colder zone and a hotter zone are found with a stable differential between.
Drilling a hole which would contain two heat exchangers at each of those cold and hot layers would allow a permanent and reliable heat exchange system where a closed loop heat exchanger mix would circulate by convection after it has been kick started by some mean.
Such a closed loop heat exchanger would easily power a stirling engine based power generator like can be found already for powering a regular house.
If made widespread, that technique would allow even smaller costs than regular heat pump systems and provide off-grid ability to remote locations...

Details

Anyone would be able to book a geothermal drilling company and in place of a water/air heat pump, use two heat exchangers with a convection circulation for feeding a stirling engine

Components

2 × heat exchanger typical tubular heat exchanger for geothermal use

1 × circulator for kickstarting the convection circulation of the closed loop

1 × Stirling engine for generating motion out of the heat of the closed loop

1 × Mechanical power generator coupled to the stirling engine

1 × a damn quantity of tubing because it would not fit without some

Discussions

simon wrote 08/12/2017 at 20:20

Hi all, is this project still active? I really would like to work on it, there are tons of applications, how hot can be the water generated by a geothermal heat pump?

Are you sure? yes | no

simon wrote 08/12/2017 at 20:20

Hi all, is this project still active? I really would like to work on it, there are tons of applications, how hot can be the water generated by a geothermal heat pump?

Are you sure? yes | no

Scott Horn wrote 06/13/2015 at 01:43

How common and deep are these hot water sources, and how do you get enough thermally conductive tubing into one to generate enough heat transfer to the cold side?

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Shrad wrote 06/13/2015 at 08:05

Hi, in that case we are not speaking of usual 90°C hot sources from at least 100m depth, but a constant temperature differential of between 5°C and 10°C to allow convection of a propylene based heat exchange fluid for direct stirling coupling

If we account that common soil-air heatpumps usually rely on ~15°C for a drilling depth of 20~30m, drilling 50m~100m more for the 5~10°C differential would cost less than the equivalent photovoltaic setup... added bonus if you have a hot water vein under your property

As those heat exchangers are already widely spread for common soil heatpumps the components should be readily available, and only mid-scale installations (more than 15kW) would require larger heat exchangers in my opinion

I currently have no means of testing or whatsoever so I cannot give more arguments, but discussions with a friend whose field is geothermy and geology gave me the few pointers that let me say it should be viable in many places

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Shrad wrote 04/05/2015 at 21:05

Currently looking for pointers on which existing stirling engine or model scale 2 stroke explosion engine would cope with propylene glycol as moving fluid... I would like, if possible and lower enough costs, to construct a hundred watt stirling engine to test heat exchanger topologies (series or parallels)

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Shrad wrote 04/01/2015 at 06:19

Next steps: draw figures, think numbers and delta T

Once that done, designing two constant temperature water cabins, and feed a scale model stirling engine for feasability!

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John Boyd wrote 04/01/2015 at 03:35

Seriously great project idea. I would bet this has potential to place in the contest

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Shrad wrote 03/25/2015 at 11:03

This project is for inspiring other people,

This is evident that I do not have a giant drill in my attic nor enough spare plumbing to make fancy heat exchangers, so please be free to inspire of this project as long as you credit the idea ;)

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Domestic Geothermal Stirling Power Unit

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