3,6x gain on your mCHP electricity production?

Heat storage Buffers and other systems for CHP, wood stove, solar etc ...
Pufferspeicher und andere Systeme für BHKW, Holzofen, Solar etc...
mCHPjr.
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Joined: 30.01.2016 22:14

Re: 3,6x gain on your mCHP electricity production?

Post by mCHPjr. »

Luk,

as the editing of older articles is disallowed I tried to clean the text a bit in the post above,
basically the efficiency depends on the type-technology of the expander used as well as the overall application goals as biomass needs higher steam temps while solar/geothermal ought to be run in sub 100C (expander working fluid medium)..

The most common types are low rpm micro turbine (newest development), or twin screw expander (basically upgraded standard chiller unit linked few months ago), or it could be high rpm turbine, among other approaches..

I doubt we can get our hands on micro turbines in the next few years, also the electronics/control is more complex. But hopefully the twin screw expanders method could be applied to DIY if sourced out somewhere, check out the link of that Spanish company, it's not entirely clear as to whether their twin screw expander is in-house product or taken from other supplier, but it's exceptionally tiny (good)! The rest of the ORC unit is relatively straightforward, diagrams, and information is plentiful, this is basic industrial standard, the only difference is to have the proper temperature/pressure setup components e.g. if burning wood directly, differently tweaked for solar/water-water/geotherm..
http://enerbasque.com/en/index.php/products/
http://enerbasque.com/en/index.php/screw-expander/

ORC is the same steam stuff as found in the majority of big thermal power grid plants, now there is the quest to make it way smaller. This is on the larger side of things, but for instance if you watch the ElectraTherm video, they have got huge biomass boiler container for burning entire solid chunks of timber wood, so inside the walls of the boiler container are hot water loop pipes connected with the outside/standalone CHP unit, where the twin screw expander and condenser+evaporator, other bits are located. Obviously you need the hot water/hydrion loop to dump or rather store such heat output somewhere, most likely in some huge m3 volume to accumulate the heat, like water tank, cavern, old pool, glass chips/bricks bunker, or earth register etc.
how does it work videos https://www.youtube.com/watch?v=Gsob6o6WP1g
(biogas plant so disregard the additional circuits cooling tower and biogas genset)
https://www.youtube.com/watch?v=eIDitPjxgis

https://www.youtube.com/watch?v=IsE9-_YhFsg


For the application of wood chips The DriZzler Pyrotouch would have to be in similar fashion connected via hot water heat exchanger loop to the intake of outside/standalone CHP unit.

mCHPjr.
Posts: 34
Joined: 30.01.2016 22:14

Re: 3,6x gain on your mCHP electricity production?

Post by mCHPjr. »

Addendum about external wood/biomass burners as seen in that ElectraTherm example/vid:
it's popular mainly in Canada and usually called "log burner" or "stump burner" or "top loading wood burner" or "outdoor furnance" and so on.. it could be commissioned and build from plans, the top loading version with water circuit even inside the top lid is the most efficient, needs pneumatic valves though to lift it, so apart from electric pneumatic operation when needed it could be perhaps also hooked to PTO on smallish tractor..

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luk
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Re: 3,6x gain on your mCHP electricity production?

Post by luk »

Michael,

I agree the stirling. with its long term stability isues, is death . This because the simplicity of an ORC unit (appart from the, not in DIY reach, turbine or screw for the expander) . Also no future any more for a clasical woodgas unit coupled to an Internal combustion engine. There the the problems to achieve clean gas: This of course if ORC comes readely and cheap available.
The only doubt I have is the Steam principle. Traditional steam engines are know for their low eficiency. Intiutively and because always there is the talk - ORC is ideal for wasted heat, makes me a little supicious how economicly this low heat steam systems is, if one has no waste heat and has to buy the needed fuel at full price.

mCHPjr.
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Re: 3,6x gain on your mCHP electricity production?

Post by mCHPjr. »

Those are very good points for discussion.

But for now I'd offer yet another link of thought or diversion if you will..
It seems in terms of mature technology for the relatively best price/quality/longevity ratio one has to go back and rethink the application of the "solid fuel cast-iron boiler" - afterall there is +100years of know-how and perfection behind it, unit efficiency is good ~90% so relatively minimal-low pollution, nowadays it's based on this "jet like effect" of burning chamber inside a burning chamber of the boiler, in terms of fuels it burns black and brown coal (low Sulphur varieties <1%), solid wood, pellets, and various ad hoc coal+wood/biomass mixes.., operation manual or automatic (feeders), pricing around EUR<2k per boiler installed (without accu and ORC).

Now for our purposes of integration with ORC it would have be to chained as follows:
cast iron boiler (on full output for highest efficiency) -> big accumulation -> ORC (on demand) electricity + remaining heat/cold ouput

For all the parameters listed above we are limited by what is proven and available on the market though, which is somewhat limited around the top ~15-45kWthermic output of these modern cast iron boilers and their respective sizing of output, let say 15-25-35-45kWthermic output for respective models.

So, for smaller sized application it would follow something like this:
25/35kWt boiler -> low x 1.000 L of accumulation ->
-> small ~5kWe ORC (on demand electricity) + heat/cold

For larger application a small cluster of these burners would have to be assembled:
x 45kWt boilers -> mid xy 1.000 L of accumulation ->
-> midsized ~25-50kWe ORC (on demand electricity) + heat/cold

All of the above assumes sort of planned on demand regime of electricity production for specific timeline throughout the working day, i.e. not trying to replace baseload like 24/365 grid service, basically the accumulation is always sized as way bigger than ORC capacity to allow for several continuous hours of operation. After that the accu could be recharged with the boilers again. In the cluster boiler setting, it could be piped in the boiler room in such fashion that serial/parallel/dedicated setup is possible with respect to only heating priority instead of always charging the big accu for the ORC loop..

Advantages: longevity +20yrs (many components several times longer), fuel could be stored at the site, dependency on hi-tech components minimal, .. , friendly to operate and service


---

Example of such combustion:
https://www.youtube.com/watch?v=PcixVF6QSxI
(video shows DIY adapted U26, very recently there is full commercial version with these properties U32, but it's not scalable to 45kWt yet only at 20kWt, you have to DIY for the "jet effect" - not expensive or complex task those older models for higher output)

Note: Luk, regarding your location, I'm not sure the geology is there for ultra low sulfur content coal natively found/mined in Silesia/PL, but they probably have it there on the market from other countries, plus you can try quality small fraction anthracite (selected black coal) from Russia, which is the best energy bang per unit cost

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luk
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Re: 3,6x gain on your mCHP electricity production?

Post by luk »

Michael,

Indeed what you describe . coal burner, Buffer Orc and a batery bank for overbridging the nights, Yes or not connected to solar harvesting heat, would be an ideal system. But as you said in the beginning. All depends on the availability of a small and relatively cheap ORC system. As prices now are, even for very small 1Kw unit I do not see many households intrested.

mCHPjr.
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Joined: 30.01.2016 22:14

Re: 3,6x gain on your mCHP electricity production?

Post by mCHPjr. »

Yes, as always the "first adopters" will have to lead the way on the unbeaten track.
In a way I posted that rough plan as an antidote to previously mentioned "Canadian furnace" idea, because apart from the import disadvantage(complexity to build one correctly), the pricing level is still much better for a cascade of smaller and domestic made boilers, however when using wood/biomass there remains this pesky old problem of chopping corded wood, there are many clever tricks how to ease the burden of this process step by step (drying, storage, transport, ..), but in the end it's a drag on the overall efficiency anyhow. And coal has its own set of issues for instance like selecting the proper chemistry content and grade of particular coal brand/type for later environmental friendly in situ disposal, like mixing the finer grade leftover ashes with biomass into composts and depositing the unusable rest etc.

Speaking about the small sized category ORC availability/pricing, hopefully I'll get soon some more specific info. By the way, few weeks ago there was an auction for one of those old mining shaft portable chillers/ORC ~30kW ?, unfortunately it was gone by the time I saw it.., and likely too big for me anyway.. ;)

mCHPjr.
Posts: 34
Joined: 30.01.2016 22:14

Re: 3,6x gain on your mCHP electricity production?

Post by mCHPjr. »

Addendum to our list of mCHP ORC systems out there:

"Flow" 1kWe/14kWt - made in Scotland by Jabil, scroll expander style
unit application tailored for natgas, loaned/prepaid system but price seems ~2,000 ?
http://www.flowenergy.uk.com/flow-boiler-tech-zone/

mCHPjr.
Posts: 34
Joined: 30.01.2016 22:14

Re: 3,6x gain on your mCHP electricity production?

Post by mCHPjr. »

Correction:

"Flow Freedom involves paying £3,675 upfront for your new boiler (inclusive of VAT).
Under this offer, you are required to sign up to Flow’s energy tariff, which is actually very competitively priced (e.g. 10/11 p/kWh of electricity and 3/3.5p/kWh of gas depending where in the country you are)." http://www.thegreenage.co.uk/flow-boiler-worth/
http://www.thegreenage.co.uk/tech/chp-boilers/

So, who knows how much is the actual price of the unit, given the contract perhaps slightly subsidized by the utility company.., but it nevertheless seems to indicate it must be competitive to previously listed models.

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