Micro CoGen.

Hello, I have a 90 tube (evacuated tube) hot water solar system.  It has an 80gal storage tank.  I want to increase the heat capacity for storing large amount of hot water.  I use the hot water to heat my floor (hydronic heating).  I see that a lot of people built wooden square tanks with a rubber lining, others collect old water tanks.  I was wondering if anyone has seen or built thermo storage,tanks of water? or sand? Wooden tanks? any ideas will be greatlhy appreicated.

The oil cooled method seams very interesting.  I believe you would be able to capture most of the heat, but with fluid there is a thermostat, how about with oil?
The exhaust might be easier.  You can use a simple controller and a pump, but how woud you consider controlling oil temp?

I was planning on using the heat to heat water for my hydronic system heating my home.  Any additional ideas are welcomed.

Hello, I am new to the forum so excuse my lack of knowledge.  I was wondering if there is an easy way to capture heat from a small diesel engine, but at the same time, still enclose it tight enough to lower the noise level.  A water cooled engine will be ideal, but finding a cheap small water cooled diesel engine doen't seem easy.  Thank you.