Log + Pellet Bivalence: Securing Energy Autonomy for Rural Projects

Why choose a bivalent boiler for a rural project?

Rural sites often have easy access to log wood but lack the time for constant manual feeding. A bivalent boiler lets you burn logs when convenient and switch automatically to pellets during absence or peak demand. This secures supply regardless of fuel market volatility.

Tatano boilers are natively engineered for this dual-fuel concept: a single heat exchanger, two loading doors, one control platform. This architecture cuts footprint and capex compared to two separate generators.

How to design the plant room for bivalence from sketch stage?

Plan volumes early: the pellet silo (3–4× oil volume per kWh) and the seasoned log store must appear on the layout from APS. HGV access for bulk delivery is a hard constraint.

Hydraulics: a buffer tank ≥ 30 l/kW nominal is mandatory to smooth output, protect the heat exchanger, and secure the +15 % Klimabonus uplift. It acts as hydraulic separator between boiler, solar thermal, and distribution loops. The flue must be sized and certified for both combustion regimes (natural/forced draft).

• Reserve dual fuel storage footprint (silo + log store) on master plan
• Buffer tank ≥ 30 l/kW for efficiency, comfort and grant bonus
• Validate flue sizing for both manual and automatic firing modes
• Allow space for pellet extraction auger/suction and ash removal

What financial leverage with Klimabonus 2026 on a bivalent unit?

Critical: the state grant only covers the pellet function (automatic feed/ignition/control, dust ≤ 8 mg/m³, NOx ≤ 200 mg/m³, efficiency ≥ 90 %). Manual log mode is not eligible.

Single-family home: up to €8,000 base (€4,000 without old boiler replacement). Buffer tank (30 l/kW) = +15 %. Solar thermal = +€1,000 flat. Municipal top-ups: variable, stackable (simulate at Klima-Agence). Application within 4 years of invoice year-end via Guichet.lu.

• Grant only on pellet mode (automatic, certified emissions)
• Up to €8,000 base + 15 % buffer (30 l/kW) + €1,000 solar
• Municipal aids variable, stackable, simulate on klima-agence.lu
• Filing deadline: 4 years after 31 Dec of invoice year

How to lock in long-term performance and fuel quality?

Pellets: require ENplus A1 (moisture ≤ 10 %, ash ≤ 0.7 %, durability ≥ 98 %, NCV ≥ 4.6 kWh/kg). Inferior grade fouls the auger, raises ash, and drifts emissions out of grant compliance.

Logs: residual moisture ≤ 20 % (meter at delivery). Covered, ventilated, off-ground storage. A maintenance contract with a certified installer (commissioning, annual check, traceable log) safeguards warranty and seasonal efficiency.

• Pellets ENplus A1 mandatory (moisture ≤ 10 %, ash ≤ 0.7 %)
• Logs: moisture ≤ 20 %, dry ventilated off-ground storage
• Maintenance contract: commissioning, annual visit, traceability
• Your Tatano Beroder provides the Offer, Energiestudie and project simulation