Hi guys. (Fla._Deadheader)here. Had to re-register. My acct info would not let me reply.
Looks like new info and a working system. Going to get interesting, now.
Thanks for all the new project info, Stu.
I finally solved my troubles with the A/C scroll compressor and I've built the system expander-coupling-generator.
I've also dimensioned the brazed plates heat exchangers (condenser and evaporator) and the pump. I'm going to buy them (that is, my firm...).
My ORC plant is intended to have a evaporator heat exchanger, in which a 90°C water from a hot side boiler flows and exchanges enthalpy with a R134 fluid (so the high side is about 82-84 °C at 30 bar) Then the refrigerant fluid expands in the scroll expander, condenses (tap water on the cold side of the condenser, low side is therefore about 7.7 bar at 30 °C) and finally pumped to close the cycle.
Now I would like to know from who has already built the whole plant, which are the main piping elements, instrumentation, valves etc. to consider??
I've surfed the internet but I've found nothing but piping handbooks...
I've thought about using copper piping and putting a thermocouple before and after every device, a pressure control device after the expander and after the pump, and check valves before and after the heat exchangers. What about the piping/devices in and out coupling?? Something to add?
Since it's the first time I'm managing to build a power plant, sorry if I have forgotten something important.
Thank you very much for the help.
Hi everyone, I'm making plans to embark on a project to build an 20 HP ORC unit, but instead of using reverse flow scroll or screw expanders, I am looking to use simpler piston technology similar to what Tim Cook has done previously using reciprocating pistons. However, I will be using commonly available hydraulic cylinders (2 stage) as pistons. I'm aiming to use a 1 piston system to generate 20hp (to attach to a 10 kwh generator), so I imagine a high torque/low rpm unit (similar to a one cylinder steam engine). I've done some extensive research on how to calculate various parameters for this unit, but still need help on some components. Here are some questions, and I really appreciate any help given
1) What is the recommended RPM to target? If I target 900 rpm (at 150 psi), is this a reasonable speed or too high for one cylinder high torque system? This way I can attach a 900 rpm generator directly to the shaft without reduction/increment pulleys. Or should I target lower rpms, and use a pulley system to drive the generator up to speed?
2) For the 20 HP orc unit (pls correct me if I'm wrong), I've calculated that 120 lbs of R245fa refrigerant working fluid needs to be used at a flow rate of 30.5 CFM (based on Power(HP)=Pressure(psi) x Flow (cfm)/229). Hot water flow rate to warm up the working fluid is calculated to be about 30 GPM based on <100C temp. I would like to use plate heat exchanger type evaporator. Can anyone tell what is the size of the plate type evaporator that I would need i.e. physical size and also size of the various inlet/outlet ports?
3) I also need to match a plate type condenser and perhaps a regenerator too. What are the sizes for these components too?
That is one hell of a project to attempt. All i can say is its going to be big, real big and big i like.
What sort of application are you building for if you don't mind me asking?
With an Organic Rankine Cycle efficiency of 10% you would need 147kW (501920.6 BTU/hr) of thermal heat input to generate 14.7kW (20 H/P) Shaft power? does that sound right or have i made a mistake?
So, you'd need a vapouriser which could handle 30 GPM (136 L/min or 8.18 m^3/h) so probably something like this type:
or 3 of these in parallel:
Not sure how many plates you would need for 147kW
I'm guessing 1 1/2" or 2" pipework?
Stuart, in response to your question, we deal with recycling of wood waste and therefore close to an in-house source of waste heat. We're looking for innovate ways to harness our waste heat into energy and selling it back to the grid as part of our recently launched feed-in-tariff initiatives. That's where I see a single or double piston cylinder system would suffice as we are not dealing with heavy machinery loads. Popular Orc technologies like reverse flow screw expanders or expensive turbines are out of our reach and budget at the moment. Using piston systems would, first and foremost be cost effective since hydraulic piston cylinders are widespread in use. They are simple enough for us to use and are designed to handle huge amounts of pressure, which may be good to accommodate various types of refrigerants. And I figured if we would be spending time and effort developing a prototype, we might as well make a slightly bigger one.
I think you are right also in predicting 147kw of energy needed to power a 20hp shaft based on 10% efficiency. I guess that would be equivalent to burning 30+ kg of wood chip fuel (based on 4kw per kg of wood fuel). But I tried another way to calculate. Based on existing ORC system of this size, we can expect a difference of hot water temperature at the inlet/outlet port to be between 15-20C. We need to continually supply X amount of energy to replenish the lost energy in order to maintain the required water temperature. So if the rated GPM for this system is 30 GPM, that equates to 1800 Gallons per hour (or 6813 litres or 6813 kg of water per hour). Hence you need to heat 6813 kg of water by 20C. And it takes 4.18 Kj to heat 1 Kg of water by 1 degree. To heat up 6813 kg of water by 20C would take 6813 Kg x 4.18 Kj x 20C = 569566 Kj or 158 Kwh. Which is very close the 147 kw of energy you stated.
Thx for pointing out the plate evaporator. In the first one your showed me, their max flow is rated at 14 m3/h. So this would be a good match for our required hot water flow rate of 8.18 m3/h? As for the no of plates would the expected temperature drop of 15-20C be any help in determining the number of plates needed?
As for the pipework, I've seen similar setups using turbines, and they use 1 1/4". Is there a big impact between using 1 1/4 or 1 1/2?
Probably best to call a supplier up and get heat exchanger sized by them.
There is a big difference in flow rates for 1 1/2" and 1 1/4" probably best you go with what you have seen.
Make sure to post some photo's of this beast when you start. It'll be epic.
Mello Tango - I would surely like to follow the development of an ORC genset system like you have described but I feel that I should at least mention another type genset system that might fit your needs and resources (wood) better - WOOD GAS - also known as PRODUCER GAS or WATER GAS. Woodgas powered gensets are a proven item and have been around for well over a hundred years, the efficiency is also much higher than an ORC system. Even the large commercial ORC systems in operation indicate an efficiency of only about 5% at best, wood gas systems are more like 20% efficient depending on how well everything is optimized.
You would be at the front of development working on a BIG piston based ORC genset, I have not read of any other large piston system such as you describe so there will be a lot of time, cost, and experimentation needed that might not pan out for a LONG time - BUT - BIG WOOD GAS systems are running in many third world out-back situations, some are large enough to power complete sawmill operations. The concept is to burn green wood or wood chips in a restricted air atmosphere producing flammable gasses, these gasses are then used as fuel for either gasoline or diesel engined gensets that are more or less stock units (SORTA). This is a low energy fuel so any engine running on it will produce about half the normal horsepower as on gasoline or diesel.
THIS LINKS TO a past discussion on wood gas, the posts by DUELFUEL describe a 1600 CC auto engine he is running on it. I am part of a small group that has also bult a small woodgas generator that feeds a 4-cylinder air cooled 1800 RPM Wisconsin engined 10K genset.
There is also a YAHOO WOODGAS DISCUSSION FORUM that has lots of info and pictures of gasifiers being built by individuals.
A web search for WOODGAS or WOOD GAS will also find an enormous amount of info, there are also many videos on youtube.
I also post to an Australian alternate energy forum, it is mostly about wind power but has a "solar" section. DON B there has converted three single cylinder Briggs-&-Stratton engines to operate there exhaust valves in a 2-stroke engine cycle (NOT uniflo) and has chained them into a 3-cylinder engine. He is using compressed air injected through the spark plug holes by electrically powered solenoid valves for testing, eventually he intends to use either water steam or ORC refrigerant.
He has developed an extensive electronic system to control the solenoids, it applies pre-opening bias to the solenoids and has variable timing based on engine RPM and more, he describes it's function in detail. The best practical research info I have read concerning using solenoid valves as input valves for a steam type engine.
Mello Tango could also use a Gasifier to power an internal combustion Gen Set and use a smaller ORC to convert the heat from the coolant.
So many options open if you have a decent supply of waste wood, you should be able to make huge savings.
Hope you're well
Found a source of diaphragm pumps which may be an option as circulators in ORC applications.
They are often used to supply water in RV's, i just ordered a 160PSI 1 GPM version to test.
At 49 pounds they are cheap enough to be viable. They draw a fair bit of power though which is a drawback, the benefit being they will pump across large pressure differentials. This model consumes 10 amps at 12V (so that is 120 watts) to pump across 10 PSI. based on the testing i've done so far i reckon i should be able to achieve an output at the expander of 500 watts by vapourising 8 l/min. That means running two of these pumps which may consume a lot of that power but it will be a step in the right direction.
Also found this which could be useful down the line:
I have finally got my new system up and running after a few problems with alternator and pumps.
It is still only running on one pump, however that has allowed it to charge itself.
Go here to see some photo's: http://www.navitron.org.uk/for.../topic,13688.75.html
This links to my other thread in a UK forum.
Boiler flow temp: 82 Degrees C
Heat In: 4.18kW
Cycle Efficiency is at: 5.76%
Electrical Efficiency is at: 2.12%
Expander Shaft power: 360 Watts
The alternator is only 55% efficient so it wastes almost half the expander shaft power but at least it's a start.
I've had the system charging itself and putting out over 85 watts electrical which is enough to run the heat transfer pump so it is self sufficient on one pump.
I have yet to add insulation, so i may still see an increase in efficiency and the addition of a second pump with hopefully get efficiency up into 6 or 7% regions.
I'll be putting a video out soon.
Here the latest on my project guys:
We have succeeded in generating power using ORC turbine. At present we have 3 kw to 250 kw units using fuel of your choice. We design heater using solid / gas or oil as fuel. The fuel consumption is so low that you run the equipment for 7 hours using one liter of diesel to generate 3 kw power. You may contact me by email to orc at mizun dotin to discuss further.
Mohan have you got a website or some youtube clips of your machines?
Can you give us some general specs for your smaller units please.
That sounds good Mohan, a link to your website would be great.
I have managed to get 150 watts net output from my system. I swapped the alternator for a 12v motor with a belt drive to the expander shaft. I then wired up the power analyser to give accurate figures.
It will be simple to scale up.
I will soon try R134A and a larger pump, hope to be able to get a 1kWe unit finished this summer.
Outstanding, keep the info coming, it will save the rest of us a lot of time and trouble.
I have built a system with a TRS090 scroll compressor but my main problem is the correct pump. I have tryed Haskel m21 a air power hydrlic pump that could over come the psi between the two sides but not enough flow, max compressor rpm 1000@ 200F , I just tryed a hot water pump "taco wet rotor" but it cant over come the psi of the high side and the system runs in spurts "check valves close till psi balances". any one think using another scroll compressor run off the "expander compressor" could work as the pump from low to high side? May need to be geared down as 1:1 with liquid pumped and gas turning the expander would build too much psi.
Thanks for any ideas and I would like to hear more about others progress, I'll post pics soon.This message has been edited. Last edited by: Imagex,
Good to see another system is being tested, keep us posted. Glad to see you are getting 1000 rpm from the expander when it runs, also good to hear that a hydraulic pump works as the boiler feed pump, now just need to increase the flow til it runs continuously. Are you sure you have enough frig fluid in the system so that the boiler can always have liquid in it, is there vacuum or pressure on the input to the hydraulic feed pump, can you change the RPM driving the pump to change it's flow?
Not surprised the low pressure water pump did not produce enough pressure, it apparently works at very low differential pressures but these low pressures are not going to make much mechanical power unless the system is LARGE and has a high flow rate (As was done with VERY LARGE low torque Stirling type industrial engines that were used over a hundred years ago to draw work from the waste heat left in steam engine exhaust). this is the reason I intend to test either a small piston pump made up of a couple of hydraulic check valves and a small aluminum air cylinder (read about hobby steam engine boiler water feed pumps), or maybe a small rotary hydraulic gear pump (also used as steam boiler water feed pumps), either one should produce enough pressure and can be sized to whatever flow is needed (read my comments on this earlier in this discussion). Air pistons and hydraulic pumps of many sizes are available at Surpluscenter.com , both new and surplus, at about the most reasonable prices.
The ratio between vaporized frig fluid and liquid fluid is something like 5-600 to 1 so the pump for the condensed liquid can be fairly small. The scroll compressor is designed for vapor so won't pump a condensed liquid, if you placed the second scroll pump after the expander but before the condenser you run the chance of some of the expanded vapor cooling enough through the expander that is becomes liquid (likely) and jambs up the scroll pump due to hydraulic locking.
You are correct another scroll as a pump wont work, I found it has a compression of 3:1 and the liquid wont compress. Maybe a power stearing pump?
The m21 pump is air driven and at max output, I start most of my test runs with the system almost full of 134a, I can tell becuase the compressor will tick around very slowly from the pump pushing liquid to it and bleed off freon as I go so im sure I've had plenty of working fulid at some point.
I also added a regenerator made from about 3 feet of 1" copper with 1/2" running through it "tube in tube exchanger" That gave the system a boost and it can run at lower temps than without.
A little trick I have found is to remove the check valve from a 30 lb tank by cutting the crimped over lip that holds the plastic valve in, then setting the tank in a 5 gal bucket with ice. This works very well to drain the system when making changes also.
Im looking at stu's idea of a double holding tank with check valves then a cap line equaling the psi to one at a time, I have a 24 volt valve from a heat pump that has small cap lines that normaly are used to move a shuttle valve that may work well for this so I may be able to use the small taco pump.
So far it seems the feed pump is the hardest part to get right.
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