alternate fuel for CHP

[elnav]

One of the things I have become interested in  during my research into alternative power for off-grid applications is methane digesters.
This is probably a technology as old as the original Lister engines.  Methane is created naturally as a byproduct of decaying biological material.  Although  quality and quantity  varies depending on feed stock it is sucessfully used as  both a cooking, heating and engine fuel.  Being naturally renewable  it  is a environmentally  green as using vegetable oil  for fuel.

If you google  Methane digesters  you will find  all manner of hits  ranging from  US goverement funded studies and pilot projects  to You tube videos  showing  sizable generators  powered by  methane. 
If you live off grid  and have a flock of chickens  for eggs or a couple of animals being raised for food  you have the necessary resources  to create your own methane  fuel.  A number of Google hits illustrate home made digesters  ranging from a couple of used drums  to  giant industrial  digesters that can feed generators to supply electricity to the utility grid. 
Several of the government funded pilot projects involve commercial farms that are now totally energy independent and can resell electrical power to the utility. One mid western farm also collects and bottles methane to fuel all their farm vehicles. 
It seems to me this is a very viable option for off-grid  CHP.

[elnav]

As a follow up to the above post  I would like to mention another old technology  that would fit well with  Lister engined CHP.  If you  do  not want or need  to run a generator 24/7  it is desirable to store excess electrical energy in batteries for powering inverters during the silent times when the generator is not running. 
Edison developed a battery  using iron and nikel plates  commonly referred to as NiFe batteries.  The electrolyte is not acid but an alkaline solution of potassium hydride. 
Two notable  features about NiFe batteries  is the fact they  do not wear out since the plates are not consumed the way lead acid batteries do. Secomndly  when a NiFe battery is depleted you only need to flush out the plates  with distilled water then replace the electrolyte, not  the plates or the whole battery.  Life span in service is unknow since the original Edison cells manufactured 75 yers ago are still running. One company located in Montana  is going to be manufacturing  NiFe batteries domestically..  I found another  company advertising  NiFe in australia. 
I also found a videon Youtube showing how you can fabricate your own.  One down side to NiFe batteries is the fact each cell only develops 1.2 volts instead of 2.0V  so you need  10 cells for a 12V battery instead  of 6  but in most off grid applications footprint size is not so critical. 
Admittedly  the battery efficiency is not as great but the discharge  characteristics is better since you can  discharge deeper  with out damage such as you incur with lead acid.

[akghound]

I live in Montana so naturally I would like to visit with them. Where in Montana is the company? How can I contact them?
Thanks .... Ken Gardner

[elnav]

www.zappworks.com/
Guys name is Stephen Ellis.

[mike90045]

.....   Admittedly  the battery efficiency is not as great 

And that's the killer. Who wants to install 20% more generating capacity ?  Solar panels are pretty pricey

[elnav]

"Who wants to install 20% more generating capacity ?  Solar panels are pretty pricey"


REPLY
Who is talking  solar panels as a supplement.
Jens lives down in the canadian banana belt but up  here we have  frost for six months of the year.  I do not think I would be able to get by running a CHP genset for only 2 hours per day.   Based on how long I would need to run a heat producing motor I would be producing  way more electricity than I could store or use.  If I was to use free or nearly so free fuel  does it matter if the battery is  somewhat less  efficient?  It just means I run the genset a bit longer. 
Same thing if I was running a Stirling engine generator from a wood stove heat source.  Even a steady 1kW genset  running 24/7  would produce  more power than I normally use.  My uncle in law  runs his off  grid home  on a single outback inverter.  But he  has now replaced his battery bank twice in 8 years at several thousand $$ each time.   The only way he could get more longevity from his battery bank is to spend much more on  capacity in order to reduce his DoD kevel. 

[elnav]

Mike you raise some interesting points.  I can see your point if  you are generating power by using solar panel and they barely keep up with demand. However  this being a CHP forum I was not thinking in that direction. In climates with very cold winters  -30 Below for example a CHP plant would be running  fairly steady. Under such conditions even with just 1kW of generation  power it would more than cover your power consumption for the day.

[mike90045]

OK, so you are using iron batteries, and you've run your genset 20% longer.  Once your batteries are charged, you will have to kick on your electric heaters (multi hundred gallons of storage) or else your low electrical load, will unload your genset, and your diesel is no longer seeing much of a load, and it will carbon up.  Wood gas or methane may not matter unless you are using spark ignition.   

[akghound]

I do not think I would be able to get by running a CHP genset for only 2 hours per day.   Based on how long I would need to run a heat producing motor I would be producing  way more electricity than I could store or use.  If I was to use free or nearly so free fuel  does it matter if the battery is  somewhat less  efficient?  It just means I run the genset a bit longer. 

I suffer from the same problem except I have very cheap fuel so extra run time is not a huge expense, it just wears out the generator and engine. In our setup we pump hot water through the concrete floor to store engine heat. We have found that it takes a long time to fully heat the floor but more importantly, it returns the heat to the rooms long after the engine is shut down. During the winter with longer nights and colder days, in an attempt to get more value from the fuel burned, we use electric heaters to warm the house while the floor is soaking the heat from the engine. At the same time the batteries are charging to power the inverters for use when the generator is down. With proper management, once the floor is heated, we can get by running the generator a few hours in the afternoon and evening and provide almost all our domestic hot water, house heat, as well as all of our electricity.
Where our rub comes is in the summer months. With passive solar heat the house stays warm, even hot. We shut off all engine heat from the generator to the floor, heating only domestic water. Yes we use less lights during the summer months but still have other electrical  demands that require the generator to run. This is when we do not get full value from our fuel. The batteries become charged, the hot water is hot but due to the heavy electrical demands the generator still is required to run and the heat is wasted, the extra available electrical power is not used and the windows on the gen shed are open. This is when I am the most thankful for cheap fuel.
I plan to incorporate solar  and wind power into our setup as time and money permit. I am also looking at a much smaller standby generator for backup power in the winter and primary generator power during the summer.
You mentioned the cost of replacing the battery bank. I too am looking at doing that. The cost is kicking our tail right now. Our batteries don't power the inverters very long so we end up runing the generator just so the kids cam watch a movie. Ouch.
Ken Gardner

[elnav]

Mike  I think you  are jumping to conclusions regarding  what  system I am envisioning . Ken Gardener  is using thermal masss  to store heat  in between  genset runs.  This is prefectly viable.  During  periods of low electrical  demand it is possible  to run a much smaller  genset for Battery charging.  Minor supplemental heat can be derived from  solar heat collector panels for domestic hot water etc.   
My  uncle in-law  normally runs a 25 kW Lister  to power his resort but when its only him and the wife, he only runs a small 4-5 kW  genset .  His brother who is also off-grid  runs his entire house on a 3 kW Outback inverter and only needs the genset running when charging batteries or  to run the well pump on a 350Ft deep well.  He uses a wood burning boiler for heat because wood is  free except for the fuel for the chainsaw.
I got to thinking about methane digesters because a couple of ranchers I know  has begun raising a few hundred chickens  for eggs so the manure is already there as raw feed stock for making methane  gas which in turn can be used to generate  electrical power.   

[Horsepoor]

Last year I started reading about Nickel Iron batteries, and found only China and Europe. As I recall, the big down side was the low efficiency meaning that there were significant losses involved with the charging process. I could mistaken, but I believe I read 30% loss was a norm and higher.

Interesting read on the ZappWorks web site, but are you sure these batteries are actually manufactured here in the US? I would suspect a Chinese import is porbably involve. I would be interested to know more. If I even installed a NiFe battery string, I would certainly drive with trailer to Montana and ship back myself to avoid expenses involved with shipping thousands of pounds. Besides, I love Montana, one the most fantastic places I have even seen I.e. (Glacier National Park, road to sun, etc).

Back to batteries, can anyone provide more information on these batteries or the ZappWorks vendor?

Bruce

[BruceM]

Wet lead acid batteries may not be as efficient as we thought.  Take a look at this eye opening report from Sandia Labs:

http://photovoltaics.sandia.gov/docs/PDF/batpapsteve.pdf

You must keep batteries frequently full to avoid sulphation and loss of capacity, but for the last 90% of charge, you are looking at 45% in the test above, and THAT WAS NOT POWER, just amps in, amps out at 3 amp charge rate. By the time you factor in 2 volt loss on the 12V battery(15%), and Peukert losses (perhaps 15-20% for a higher rate of charge like on a generator), you could likely be under 30% energy efficiency!!! 

Note that at 50% depth of discharge, they got 85% (not counting Peukart and voltage in/out losses).  But only because the first portion of that was 95%.  If you are prolonging the life of your batteries by reducing depth of discharge...you will pay dearly in energy efficiency. 

NIFE may actually have a better overall efficiency for typical off grid operations, since they don't have to be kept full.  Some of the NIFE vendors now say 80% using the nicad nickel pocket forming method, but even 60% is great compared to a shallowly cycled wet lead battery.  Now if only the prices would come down on NIFE or LIFEPO4.  I'd need a boat load of cells for my 120V bank!

BruceM

[mobile_bob]

Bruce:

thanks for the link, it is an important one in that most folks don't consider the true cost of ownership of a battery bank
when they get all caught up in wanting to shallow cycle the set in order to extend their lifespan.

yes you can greatly increase the lifespan of a battery by short cycling them, but generally at a huge cost in fuel consumed to
charge them.

now if that fuel is low cost (waste veggie) or free (solar pv, hydro, wind) maybe that makes sense to short cycle and get a dramatically longer
life out of the batteries.

btw, nice to see you again, you have been missed.

bob g

[mike90045]

Wet lead acid batteries may not be as efficient as we thought.  Take a look at this eye opening report from Sandia Labs:

Well, that's a buzz kill 

[elnav]

Last year I started reading about Nickel Iron batteries, and found only China and Europe.

Interesting read on the ZappWorks web site, but are you sure these batteries are actually manufactured here in the US? I would suspect a Chinese import is porbably involve.

REPLY
I contacted Zapp Works and was informed that at the moment they were busy refurbishing some Edison  cells (olld U.S.  mfg.)  in order to do some testing. I had asked for data curves instead of single data point information. The correspondent  indicated they expected to have this testing done in six months   and be able to post  data curves then.  
He clearly indicated  actual manufacturer would be done domestically.  And why not?  a metal shear  to cut iron and nickel sheet stock into plates  plastic  cases  to hold plates and electrolyte.    The formula for mixing electrolyte  from powder and water is readily available.  the case tops will be removable so you can  open up the cells and flus  the plates  prior to replendishing  the electrolyte.