3,6x gain on your mCHP electricity production?

Heat storage Buffers and other systems for CHP, wood stove, solar etc ...
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mCHPjr.
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3,6x gain on your mCHP electricity production?

Beitrag von mCHPjr. »

We exchanged with Pascal a couple of messages over the issue of what to do with the kWel output of your CHP/BHKW, especially in terms of how to properly size your domestic in/out energy needs (large heat buffer/tank needed ~800L is just a fraction of family house needs), and spiking demand for instance in very cold winter days. The general suggestion is to run additional wood/coal burner in heat loop but there is other way as well:

Unsuprisingly there are several existing applications of "best practice" in the world already on this very topic of leveraging your CHP output. One of them is the theme for this post in the area of "water-water" heat pump as an extension and multiplier effect on your mCHP system, there are home sized commercial product versions in Germany and elsewhere working obviously for some time already.

Basically, not necessarily on continuous basis but at given moment of your needed demand such as winter freezing spike you don't sell your generated electricity to the grid but you multiply it by leverage of ~3,6x (or higher) in heat pump addon subsystem to your existing mCHP. Therefor yours 1kWel output of CHP will transform into generation (rather collecting) of roughly additional 3,6kWthermal, which you can again push into your buffer heat tank. I hope Luk eventually takes interest in it since he is supposedly sitting on an old volcano hill.. ;)

Now, this is all existing working and available stuff, pretty dandy, but a bit on the expensive side, for instance the sub 10kWel Buderus/IVT geothermal heat pump units are listed for ~EUR10k, plus you have the crew of contractors digging a bore hole +100m down for the heat exchanging fluid loop in the Earth crust or shallow ground collectors option (not discussed here). What a bummer, you can take a bank loan or perhaps diy workaround is possible?

The things is the geothermal unit is basically a variation on the fridge or chiller system, so this step could be adapted, the drilling crew task can't be skipped let them do it for you anyway (more or that later *).

So one approach could be using the so-called "screw compressor chiller" method, that's either adapting and using already assembled machine, which is used in mining equipment and various industrial processes, the problem here is that this ***invention/or idea of re-purposing existing water-water style mining chiller equipment for domestic heat pump system originated in late 1970s and at that time it was not unusual to have in mining shaft "small portable" > ~15kW units, but nowadays this is being done differently by much larger centralized mine airconditioning. However, with the fall of mining in Europe, this older equipment could be still perhaps obtained for a song in Saxony, Poland, and other regions, after you get it, it's basically plug and play, connecting to your buffer hot water loops and the geo-earth collector/bore holes.

But there is yet another possibility in sourcing the main part the screw compressor item only and in mCHP friendlier power band lets say 5-15kW and building the remaining parts around it.

There are some intro videos (of bigger scale application) but same in conceptual and practical sense:
Schema and Alaska example: https://www.youtube.com/watch?v=3LSxhSrbzPE
Another diagram: https://www.youtube.com/watch?v=1knDrYEClJ4
Overview (screw air not water but some similarities): https://www.youtube.com/watch?v=4DwEWdymeo8

sample what we are looking for (often way bigger than needed home scale but you get the idea):
http://www.thermalcare.com/assets/image ... -large.jpg
http://img.enlightcorp.com/nimg/60/cf/7 ... ontrol.jpg
** http://www.tandemchillers.com/images/wa ... tangle.jpg
http://i01.i.aliimg.com/photo/v17/50223 ... ressor.jpg
http://g02.s.alicdn.com/kf/HTB1DPSLHVXX ... Bitzer.jpg
http://i01.i.aliimg.com/img/pb/067/392/ ... 67_998.jpg
http://i00.i.aliimg.com/img/pb/559/500/ ... 59_694.jpg
(old mining portable) http://www.gascontrol.cz/img/klimatizace_csm1.jpg

Another diy heat pump VERY cheap approach with conventional parts standard refrigeration compressor and readymade automotive heat exchangers (less power/longevity than screw compressor method - but more suitable for smaller-mid mCHP):

It seems totally crazy community there, they are even diy *drilling geothermal bore holes on their own!
http://ecorenovator.org/forum/12179-post603.html
Quick view at the geothermal heat pump unit ("5 Ton GSHP Build" forum project) more further down:
/you can see both the insulated evaporator and expansion parts based on ordinary "autopart" heat exchanger/
http://ecorenovator.org/forum/attachmen ... m_3077-jpg

Both heating/cooling operation (summer/winter) possible via unique single 4way valve switch (or several valves):
http://ecorenovator.org/forum/17565-post994.html http://ecorenovator.org/forum/17566-post995.html
(This "Randen from Ontario" method is even cheaper as the evaporator+condenser are made from copper tubes inside tube and not bought as somewhat pricey plate exchangers!), using Propane as refrigerant, he seems to be doing ~18.5k BTUs per hour from 1kWel, now multiply it by 5-6x for ~6kWel suggested mCHP installation
=> ~100k BTUs/hour (~29kW/h) extra gain from the same burning few kg of raw woodchips/pellets
(with the little help of the Earth's core and Solar irradiation intake)

Here Randen recapitulates experience-results after running the system for 5-6 years with improvements, more pictures:
/Best to read the whole thread as the pictures at the end could be at first bit confusing because although he is using water to water heat pump system, the output is directed as demanded by operator towards the floor loop in one room-office, but the heat is also supplied to another room into a garage-shop with ceiling aircon blower unit on low speed ventilator, which he is able to reverse by that valve thingy in summertime for cold operation. Also he is definitely recommending VFD control, especially for the later improved/bigger version of the compressor (helps to adjust power in summer-winter-spring weather). Another hint, don't use the tube in tube method (of early system 1kW small compressors) in larger systems.
For those bigger compressors (~5-6T = <100k BTU) go directly with plate heat exchangers, living in Ontario/Michigan climate he is feeding pretested ~ -25C ready glycol-water mix to the earth collector pipes, so this a tweak for his local conditions, .. Old cheap/free junk fridge/aircon compressor could be a problem, go for quality brand..
http://ecorenovator.org/forum/geotherma ... ld-11.html

Multi bore method doable diy as opposed to single 100m depth bore hole made by profis
(which is still preferable longterm as it's less prone to surface action destruction, longer lasting investment):
https://encrypted-tbn2.gstatic.com/imag ... gQJ7S1l-Uw
* http://ecorenovator.org/diy-ground-sour ... lling-rig/

** perhaps also marriage of both methods is indeed possible, using the Randen method for tube inside tube evaporator/condenser but utilizing a heavy duty yet smallish type of oil bath screw compressor (are there any quality brands sub 10kW?) instead of the cheapo massproduced fridge/aircon type, which especially of today's quality won't last much.. Edit: no, match the powerful screw compressor only with quality plate exchangers

*** credits Dr. Broz/Prague's technical faculty 1978-1982 renewables pilot project in Southern Bohemia
Zuletzt geändert von mCHPjr. am 01.02.2016 20:33, insgesamt 8-mal geändert.
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luk
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Re: 3,6x gain on your mCHP electricity production?

Beitrag von luk »

Michael,

Thank you for your thorough research and information. You are a great asset to our forum. Indeed the heat pump is an obvious solution when designing a slightly underdimensioned cogen system where the priority is heating and where is lesser demand of power. But as you wrote, heat pumps are expensive unless you build one yourself. One should not aim at a high efficiency, a COP of 3 would already be very helpfull. The real problem with a cogen system poses the summertime. Unless you are building a swimmingpool, running a barber shop or any other business that needs a lot of hot water, what would be the options to convert this hot water in something usefull. Maybe you could use your heat pump the other direction for cooling.
Anyway, for me living in an area where is almost absolutely silence during the night, the heat pump with its noice condensor is a no go.

The vulcano is tempting me already for a long time. It is solid basalt some thousend metres deep, so only hot rock drilling comes in play. But a around one million euros per 1000 metres this method lies far behind my finacial possibility`s. Some of my fellow monuments owners have good lobby connections (important in a central european country) and get their drilling almost enterely fianced by public and european funds.

Now I must hit the road, be back in a week.

Luk
mCHPjr.
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Registriert: 30.01.2016 22:14

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

Beitrag von mCHPjr. »

Luk> thanks for the kind words. But the idea of the heat pump system described here is water-two-water NOT air venting-condensing style heat pump, so no soound! As stated in the intro above this is basically just and only replacement of IVT/Buderus/Nibe geothermal units (~Euro10k) and these are quieter than wash machine sitting already in cellars of many households around the world. Hope this explanations helps. The bigger screw compressor method for higher output say 7-15kW could be a bit louder but still nothing comparing against the wild roar of combustion CHP engine even if sound proofed. It's all home "fridge appliance" stuff and water based space heating not air (but possible if somebody prefers)..

Sound of water heat pump (compressor) for BBC Radio here:
https://youtu.be/1KzW1cedk0E?t=67

ps summer time surplus, it should not be a problem, seems solved for decades already as CHP people of high output do it by enlarging or cascading their buffer/heating storage volumes.. roughly family house needs few thousand liters bunker-buffer tank, smaller condominium housing and or villa-mansion ~10-25k liters, and country estate such as yours with several separate buildings-floors to heat could well eat into low hundreds of m3 tank total, now the depression is closing in, steel is cheap and you have lot of barn space under roof, perhaps hire bunch of good welders and you are set for such a tank/array of tanks, spray/wrap insulation, cover the box with shaved planks, voilà historic monument friendly.. At that forum they provide energy plan calculation before starting the project, but CHP and big buffer heat tank should be included into the equation extra, as they don't have that..

ps heating/cooling reversing, yes that should be possible as well by reversing that 4way valve, perhaps you could dedicate a cold room in summer for this purpose, make an tourist attraction of it, I can see the adverts
"Frigo Chateaux Rooms and Cellar - World's One and Only Sensation for Your European Summer Holidays" :Strom:

ps basalt rocks, well then you could do a pond system and submerged collector at the bottom, needed some paper work for new pond excavation as well (could be shallow because of the basalt layer), but at fraction of budget you mentioned, would be nicely heating up from bellow in winter time
mCHPjr.
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Re: 3,6x gain on your mCHP electricity production?

Beitrag von mCHPjr. »

Since the first reference-overview post can't be longer edited..

- For the "Randen method from 5T pump thread" ; when operating 3phase compressor via 3phase VFD control, it's important to install basic safeties such as pressure switches into the "copper" refridg. loop., especially when VFD is used and programmed to intraday temperature fast/slow ramps (night-day, and or summer/winter), as happened to those guys, the unit in fail mode for whatever reason could freeze solid over in minutes if something brakes and nobody's around etc.

- They've got in that same thread nice graphs about the geo-earth collector depth/temperatures through the year/seasons, it seems the diy vertical drilling for an array of multiple bore holes (if attempted diy) should be made at least in ~3.5-4m depth as this seems to be the sweat spot of relatively good yearly temp performance and also not excessive depths to drill..

(sorry for being preliminary against the "easiest" traditional way of doing ground collectors with plastic pipe loops and bulldozing/trenching the whole garden like crazy, firstly it's a huge mess, and simply the other method of either multiple shallow drilled bores diy (4m) or profi-contracted job of 2x50m or 1x100m seems to last much more (and it's somewhat serviceable at one place) - possibly with the exception of pond ground loop collector but that's huge topic on its own)

Also, from the forums of diy drilling for vertical collector seems you need to drill 16-20x (4meters) bore holes per each Ton (~1kW of compressor), so lets say more than 50x for ~5kWel mCHP output, which sounds kind of crazy amount of diy work in comparison to professionals crews with equipment but the diy savings are huge..
mCHPjr.
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Registriert: 30.01.2016 22:14

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

Beitrag von mCHPjr. »

Last comment for now on diy drilling, it seems the practical upper limit before getting semi-profi ("Vlad") equipment and budget (several specialized profi drill bits for depth needed for rock, gravel etc.) is something like this "simple" rig by "marke" - it's good for upto ~25m (soil type?), basic surplus parts and metal, all bellow $1k pricetag.. seems as the way for mid sized or even bigger mCHP 5-10-15kW water-2-water heat pump collector array..

video: https://www.youtube.com/watch?feature=p ... lvaI8mMD4s
discussion goes few pages back and forward:
http://ecorenovator.org/forum/geotherma ... hp-17.html
mCHPjr.
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Re: 3,6x gain on your mCHP electricity production?

Beitrag von mCHPjr. »

Link to animated and interactive model of heat pump, you can click on various parts of the system for explanation.
http://www.dimplex.de/animationen/kreislauf.php

Luckily enough, they also show the reversible heat pump in the second example, that's basically the same function what previously linked user Randen from that heat pump forum has been diy-ing and running for past 6years. You just select on top heating or cooling and watch that 4way valve in the diagram number (5) changing the flow.
http://www.dimplex.de/animationen/kreislauf2.php
http://www.dimplex.de/professional/tech ... pumpe.html

You see it's just all almost silent water - to - water, that aircon fan loop is only optional (and you can run it on slow)..

ps so far failed to locate any "water screw chiller compressors" bellow ~30kW, so as assumed, sadly it's likely no longer manufactured anywhere, that old mining ~16kW system was possibly pretty rare, they offer now only something 2-3x bigger for starters. Anyway, so lets stick with that diy forum examples and largely available "fridge" scroll type 3phase VFD controlled compressors (4-7ton/~6kW max) be it from Danfoss, LG, chinese nonames, scrap/used etc.
mCHPjr.
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Re: 3,6x gain on your mCHP electricity production?

Beitrag von mCHPjr. »

Little update: sorry for the above-previous incorrect description, screw compressor of our desired specifications, lets say 3-12-30kW electricity input range do exist, for example you can look at new or used brands such as "Bitzer, Dorin, .." and others, but obviously the larger units are/were more commonly used.. New datasheets as well as surplus/used units are googlable.

So, I hope Luk and others with favorable local conditions can plan on using water-water or earth-water heat pumps to leverage the e-output of their DríZzler to achieve more thermal gain. Apart from DIY approach to build such specific type of heat pump (+earth collectors howtos are linked already), I've found commercial supplier of the completed units as well, so far their reference model fitting our descriptions was ~15kW el. and 56kW thermal, but this is not very typical application anyways (as sales are mostly air heat pump units), I'll try to ask them about ~5-12kW range, if that's possible to arrange..
mCHPjr.
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Re: 3,6x gain on your mCHP electricity production?

Beitrag von mCHPjr. »

Update: on ORC - Organic Rankine Cyle heat exchangers

I've not seen mentioned here so far, but commercial world of micro CHP is most likely going in the direction of small low rpm (and low/mid steam temp) expander/turbines, instead of scroll/screw compressors linked above. The prices for these new micro turbines are relatively high, however the rest of the CHP module is just basic setup of cheap industrial chiller as I linked previously, another advantage being the m-turbine is directly mounted to low rpm electric generator (or combined with the turbine casing) without need of gearbox, also obviously achieving much higher efficiency, smaller formfactor, not attended operation, lower noise in comparison to auto engine etc.

There are several companies on this <50kW market, not exclusive list:
(most of them are googlable/ytube)

- Wave <10/30kWe units
(advanced pre production testing, micro turbine supposedly of new concept so good price, made in .cz)

- ElectraTherm ~50kWe units / not exactly microturbine (twin screw) but good ideas for biomass (not sure they are interested in <<50kWe market now, US made?)
https://electratherm.com/products/power ... -to-35kwe/
https://www.youtube.com/watch?v=IsE9-_YhFsg

- Enogia <10kWe and bigger units
(large testing uni/industrial programme with variety of heat sources, made in .fr)
http://www.enogia.com/references.html

- Valiant <10kWe units
(this is so far on natgas input only and expensive 'EUR10k?' but made in .de)


Now, this is only a beginning, should only the element of the micro turbine be mass produced (eventually in Asia?), the affordability of these heat exchange devices would be somewhere completely different lower levels, as the rest of the unit is just run of the mill parts..

hint: for biomass burning we prefer the mid temp steam setup (silicon fluids), while solar and geothermal application are often ok with the basic low temp steam setup..

hint2: the advancement of Drizzler's Pyrotouch research is still applicable here for the microturbine approach as most of those companies have limited experience in feeding biomass chips and/or they apply different bigger burners for big chunks of raw biomass

Additional quick overview here: http://www.infinityturbine.com/index.html
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luk
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Re: 3,6x gain on your mCHP electricity production?

Beitrag von luk »

Michael,

That is realy an intresting article you wrote. I am wondering what might be the efficiency of an ORC unit.

As I understand your sugestion then The DriZzler should only need to deliver heat. Cooling, Filtering, producing tar free engine grade gas, It would all be obsolete. Merely the DriZleR would be stripped down to an automatic biomass burner?

Can one say the ORC is similar to a heat pump, but then one designed for high temperature. Wonder if it would be doable to build one ORC system as a "do it yourslef" project.

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

Beitrag von mCHPjr. »

... editing the above post...


For ORC there are several approaches/solutions and companies/products on this <50kW target market of interest, not exclusive list (most of them are googlable/ytube) >>


Low rpm-pressures/alternative turbines:
-----------------------------------------------------

- Wave <5kWe
(advanced pre production testing stage/commercial 2017?, micro turbine supposedly of novel cost effective concept - fluid medium 280C silicone oil, multi fuel, made in .cz)
http://inspiredbyrankine.com/?lang=en

- Enogia <10kWe and bigger units
(large testing uni/industrial programme with variety of heat sources, made in .fr)
http://www.enogia.com/references.html

- EnerTwin 3-30kWe units (2016-17 market ready?, made in .eu/.nl)
http://www.enertwin.com/faq-s-en
http://www.mtt-eu.com/applications/micro-chp/

- Infinity 6/10/15/24kWe turbines, seems to be small custom shop, expensive
http://www.infinityturbine.com/index.html


Classic/high rpm "jet" turbines:
----------------------------------------

- Capstone C30kWe (air gap bearing = no oil) US made, expensive, burns lot of fuel types
www.capstoneturbine.com



Twin Screw expander (new gen of screw expanders):
-------------------------------------------------------------------

- ElectraTherm ~50kWe units / good ideas for larger biomass
(not sure they are interested in <<50kWe market now, US made?)
https://electratherm.com/products/power ... -to-35kwe/
https://www.youtube.com/watch?v=IsE9-_YhFsg

- EnerBasque 5/25kWe screws /offer complete ORC units or possibly selling only screw expanders? made in EU or imported?
http://enerbasque.com/en/index.php/products/


---
Stirling engine based mCHPs - expensive seems like dead end now, so not listed..
- Cleanenergy, Viessman and others
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