Digester to run a AGA cooker

timbo · Post by **timbo** » Tue Mar 27, 2007 2:45 am

Hi Bo,

just posting to say thanks for the site and the great online calculator.

I am planning on building a digester to run my AGA cooker like this one:
http://www.aga-web.co.uk/57_70.htm
These cookers are very popular in the UK with a very high number in smallholdings of just a few acres and enough animals to be self sufficient.

They are terrible for the environment usually being oil or gas powered!

I was going to try using bio- fuel oil but thats not the answer.....but I think biogas might be.

It takes a nice steady flow of gas too so should match the nice steady output from a digester.

Any comments about how to proceed would be welcome. I was going to heat it with a solar panel so I guess the temperature will drop a few degrees at night...should I manage this with a gas reservoir or use some electrical heating to supplement the solar do you think???

Timbo.

Post by **Bob** » Thu Apr 05, 2007 5:19 pm

Hi Timbo,

I think the short answer to your questions is "It depends".

Hot water solar panels can be a good solution, but it all depends on things like climate, latitude, cloud cover, size of tank, amount of insulation on your tank, etc.

timbo · Post by **timbo** » Sat Apr 14, 2007 4:02 am

Hi Bob,

Thanks for the reply, I am still planning and working it all out in my head, whilst trying to get the parts together. I will try and be more specific with my questions:

I read on your diagram the line "and as close to the operating temperature (95 degF) of the digester as possible", I wondered just how critical this temperature is? maybe there is a graph somewhere.

If the temperature were 10 degF high or low would that affect production by 25%? 50% maybe?

Perhaps I should use a solar panel to heat a tank of water and then use that as a heat reservoir to switch heat the digester when it is needed, the control circuit would be easy and I could control the digester temperature to within couple of degrees.

The ambient temperature can get up to 85degrees in the summer, if it is well insulated, can the digester overheat itself? I assume that the digestion process generates some heat.....I would probably use a lot of insulation ... 6" sheep's wool or more (we have plenty of sheep!)

Thanks again in advance for any guidance you can give me.

Timbo.

Post by **Bob** » Thu Apr 26, 2007 4:57 pm

Hi Timbo,

I'm currently out of the country, will respond in more detail on retunr.

timbo · Post by **timbo** » Sun Apr 29, 2007 9:02 am

Hi Bob, no immediate urgency. I expect to be starting this project later this year, any guidance welcome.

Thanks.

Timbo