RES-chains training material:

The aim was to identify sustainable renewable energy source chains (RES-Chains) to encourage sustainable development within the South Baltic Region. The training material aimed to describe the connections between renewable energy sources and customers.

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Your choices:
1 Process cooling (< 0 °C);   Electricity;   2 Biomass (digestible sludge)

What is your resource? What do you want to deliver? What is the service the customer wants?
2 Biomass (digestible sludge) District cooling Comfortable indoor climate
Biomass (fermentable sludge) District heating Electricity
Biomass (solid) Electricity 1 Process cooling (< 0 °C)
Geothermal Fuel: Gaseous Process heat/steam (50 - 150 °C)
Sunshine Fuel: Liquid Process heat (150 - 1000 °C)
Water Fuel: Solid Process heat (> 1000 °C)
Wind Local cooling (ind. house) Transport
Residual oils/fats etc Local heating (ind. house)

 

Unless for example a municipal-sized digester is used for local electricity production in a CHP-plant, large-scale electricity production from digestible sludge can be accomplished in different ways:

There are a few differences between these two ways:

So the cost distribution between gas production and electricity production becomes different and the total cost associated with the two solutions will have to be carefully investigated before any decisions are taken.

For large-scale production plants, biogas of sng-quality is available from the gas grid.

For local use, such as a farm dairy or butchery, raw biogas can be used used in an internal combustion engine – basically a modified car or ship engine – with a generator connected to it. The cooling water from the engine is used for district heating, maybe with an extra temperature boost for cold winter days. Such an extra temperature boost can be achieved in an external combustion chamber again fired with the raw biogas and maybe with a pilot flame. A system like this will exhibit a limited flexibility with respect to the ratio between produced electricity and produced heat. Electricity production may amount to at the most 20-30% of the biogas input and down to 5-15% in small-scale applications and the total efficiency can be up to about 80%.

The electricity will then be locally produced and can be used for cooling purposes.