ᐅ Water-bearing wood stove and domestic hot water heat pump

According to the heat load calculation, I have a heat demand of 4789 watts for a single-story new build with approximately 100m² (1076 sq ft) of living space. Hot water demand is about 120 liters (32 gallons) per day.

What do you think about using a water-bearing wood stove as the central heating system (fuel freely available) combined with a hot water heat pump?

Best regards, Portoalegre

Nothing, but that’s because I wouldn’t want to heat with the fireplace every day. Throughout the entire heating season, year after year.

I’m not sure if there even is a suitable fireplace for such a low heating output.

You have to understand that the heating load represents the extreme demand, meaning the heat requirement at around -14°C (7°F) depending on the region. At +5°C (41°F) you also need heating energy, but it is significantly less than 4.8 kW. I can’t imagine a stove that heats water for the heating system being able to adequately cover such a low heating demand.

I think it’s a good approach and I’ve done it the same way. My heating demand is higher, though. What you definitely need is a buffer tank, ideally a hygienic storage tank (stainless steel coil for the domestic hot water). This allows the stove to fully charge the buffer. You’ll need about 1 kWh per degree and 1000 liters (264 gallons). So, if I install a 1000-liter (264 gallons) buffer and operate it between 40-60 degrees Celsius (104-140°F), one cycle (from 40 to 60 degrees Celsius) requires 20 kW of heating power. That translates to roughly 5 kg (11 lbs) of wood.

Please don’t take the watt and gram values too literally. I’ve used approximate values here (water actually requires around 1.16 Wh per liter per degree, wood varies between 3.8-4.4 kW per kg depending on dryness, efficiency varies by stove between 60-90%, etc.)

Hello

Almost correct, instead of the WWWP it’s better to have a thermal solar system work on the buffer tank during summer and transitional periods.


Olli

Nothing. Too expensive for too little savings. We currently have 5-6€ (euros) per month for hot water costs with just a brine-to-water heat pump and nothing else.