3,6x gain on your mCHP electricity production?
Verfasst: 01.02.2016 01:44
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
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