Wood chip drying in connection with combined heat and power or solar energy in Finland Samuli Rinne Henrik Holmberg Tiina Järvinen Kaisa Kontu Sanna Syri Aalto University

Source: bing.com/maps

Condensing power

Combined heat and power District heating Replaces mainly conventional condensing power

Photo: Mika Karppinen A state of the art-CHP-system

The Finnish electricity production, hourly averages in , MW

Electricity production in EU27 in 2010 and 2020, TWh Nuclear Coal, peat Natural gas Solar

The targets of the wood fuel drying in this concept: 1. Better energy efficiency 2. More flexible CHP production 3. Profitable operation

Lower heating value of wood chips per loose m 3 Bark Sawdust Forest residues

Lower heating value of wood chips per loose m 3

Combined heat and power + fuel drying with CHP heat District heating More electricity production with the same amount of fuel

The studied CHP system

The targets of the wood fuel drying in this concept: 1. Better energy efficiency 2. More flexible CHP production 3. Profitable operation

Simulated power production in Finland in a week on March, MW. Nuclear and industrial CHP omitted. The nominal effect of wind power is 8000 MW in this future scenario (about 50% of the total Finnish power production capacity).

Flexibility in the district heating networks with CHP 1. A lot of wind/solar (+nuclear) production → low electricity price. CHP production is decreased: - heat storages are discharged - demand side management: the heating of buildings is decreased if possible 2. A little of wind/solar (+nuclear) production → high electricity price. CHP production is increased: - heat storages are charged - condensing turbines (which are connected to the CHP turbines) and even auxiliary coolers are used - demand side management: the heating of buildings is increased if possible - snow melting is put in operation - fuel dryers using CHP heat are used

The targets of the wood fuel drying in this concept: 1. Better energy efficiency 2. More flexible CHP production 3. Profitable operation

To make CHP production more profitable, it should be concentrated more to the moments when the electricity price is high

Net production cost of heat (NPC) pf CHP heat = Fuel cost + variable O&M cost – income from electricity sales amount of heat 20 e/MWh fuel + 1 e/MWh fuel – 49 e/MWh electricity * 0,33 = 0,55 = (in average, in this case) 9 e/MWh heat

Dryer properties 100% 80 o C 60%40% Evaporation Losses

The Nordpool electricity price in Finland in 2011, e/MWh and the marginal cost limit for the drying NPC < 12 e/MWh NPC > 12 e/MWh

The optimisation of the dryer use

The net production cost of heat in the different alternatives, 1000 e/a The maximum input heat effect of the dryer, MW

The net production cost of heat in the different alternatives, also with solar heat, 1000 e/a D = The maximum input heat effect of the dryer, MW S = The aperture area of the solar collectors, hectares

Dryer performance: 6% more energy in m GWh 80 o C 34 GWh Evaporation Losses MC 45% 556 GWh MC 28% 590 GWh 22 GWh

The next steps in the research -more dryer investment data -more test years and a future scenario -better consideration of power plant ramping rates - maintenance costs of the dryer? - effects to the system level emissions?