Biogas engine for rural East Africa 1

[sallycinnamon]

Hi,

I am looking at the feasibility putting in a biogas engine to power a dairy cooling centre in rural East Africa.

I have two questions:

1. The start up power of the refrigerator is 26kW but the normal running power is 20kW. Should I be looking at engines of 20kW or 26kW?
2. I am thinking I need to look at a compression ignition/dual fuel engine. Does anyone have any advice as to whether this the best idea? My reasoning is that if the biogas is off we can still use power the fridge with emergency diesel supplies.

Thanks a lot for your help, please let me know if you need any more info.

Sally

 

[Lou Scannon]

Have you studied what is available in the marketplace to fit your requirements? I believe that Kohler has developed small spark-ignited industrial engines for propane and natural gas, but I'm not aware of any biogas or dual fuel variants.
In the compression ignition (diesel) category, Kubota has a good range of strictly diesel offerings. It might be possible, if a well designed dual fuel conversion kit exists, or if you have resources to do your own developent, to convert such an engine to obtain 50% or more substition of biogas for diesel at high loads, but don't set your hopes on anything near 100% substitution.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[sallycinnamon]

Hi, thanks for the reply. I am in the process at looking in the marketplace but want to be sure I am asking for the right thing.

We're not looking at doing our own development - we don't have the resources. I am hoping to just buy a generator that is designed for biogas. Are you saying that doesn't exist? What would you recommend as the best option to convert biogas to electricity?

 

[catserveng]

There are a number of ways to approach this, likely some of your best resources will be in Europe, there are a couple of companies in Denmark and Germany that make diary digester power systems with a number of different engines.

FG Wilson has packaged small biogas units, I'm not sure with what prime mover or exact details.

I have done a couple of small projects that went into Mexico with Yanmar diesel engines and Altronic/GTI bi fuel systems that ran off landfill gas. That was several years ago and I'm not sure what became of them. We had to make a number of modifications to the bi-fuel package to get the needed fuel volume into the engine, our best substitution rate with landfill gas at 44% methane was 60%, and that was likely not sustainable, we felt 45-50% long term would likely work best. Those units were rated at 45 ekW.

To start a 26kW compressor, depending on starting method and compressor characteristics you could need as much as 65kW.

There was a company doing work in India, Prometheus Power I think that was doing milk chilling plants in rural India, try a Google search on dairy power systems might get more info on that and similar systems.

On the Kubota engines, they have a line of industrial gas engines that I have heard have been run on low BTU fuels with some fuel system modifications, but these are around 15-20 kW and may be too small to start your refrigeration unit.

Just about any spark ignited engine can be made to run off biogas if you can cram enough fuel into it and get it lit. How you treat the biogas has a big impact on how successful you'll be. At minimum you will have to dry it, and likely it will have some H2S, but animal sourced digesters don't seem to have many siloxane problems. Pick any engine with a fairly high compression ratio, a robust ignition system, and avoid a turbocharged engine.

The biggest problem finding a relatively small unit "off the shelf" is the amount of work required getting a unit to perform reliably on biofuels. Once you get to above 200 ekW there seem to be more choices. Gauscor is a company that seems to provide production dual fuel units, and may be able to help. Also companies like Deutz and Hatz make small industrial engines and likely have customer who have worked in the areas you are trying to find a unit for. You can also try EGSA.org and look at their buying guide and membership directory to see if you can someone to meet your specific need.

Hope that helps, Mike L.

 

[RossABQ]

Seems like an ammonia absorption system (possibly with solar system for electrical needs) would be a possibility?

 

[catserveng]

Here is a link to a milk chilling system being used in India, I have heard of the process while working there, but have not had an up close look at it.

http://www.coolectrica.com/index.php

Mike L.

 

[Lou Scannon]

The problem you are facing is that you have quite a niche application, at a pretty low power rating. There is plenty of interest in biogas engines at higher power ratings, since all of the incentive [for developing biogas compatible engines] comes from the fuel cost diffential between biogas [almost free, on site] and pipeline gas [market price, not cheap].

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz