Drying Firewood when RHI payments stop.

[openspaceman]

24 minutes ago, ash_smith123 said:

In less than a week and for less than £10 a cubic metre? 

Is that the target?

 

Is the cubic metre related to solid wood or loose wood bulk density?

 

What start moisture content and finish?

[openspaceman]

On 2/2/2018 at 14:18, donnk said:

Power correction is quite easy option, you get a specialist in they measure the loads work out how big a capacitor bank is and you just do the math.

supplies less than 75kVA tend to have whole current meters which measure real power so power factor doesn't come into it unless the run from the meter is long enough for I2R losses to be significant.

[gdh]

It would be interesting to do some costings for electric and oil drying, I suspect they would be cheaper than logs and around the same as chip.

 

I think realistic running costs for chip, including electric for fans, for us are £8 a cube 45% - 15%.

[HertsWood]

In less than a week and for less than £10 a cubic metre? 

Yes, I’m looking at a design to compliment my Pressvess retort. Make 2 products from one heat source

[Chalgravesteve]

I’m not sure I would want the downstream heat from my kiln heating a “normal” building. Once it’s passed over the logs to dry them it has become laden with moisture so it needs to be vented in my opinion. 

 

Taking heat off the boiler to the building as a separate draw is a different issue. 

 

 

[ash_smith123]

1 hour ago, Chalgravesteve said:

I’m not sure I would want the downstream heat from my kiln heating a “normal” building. Once it’s passed over the logs to dry them it has become laden with moisture so it needs to be vented in my opinion. 

 

Taking heat off the boiler to the building as a separate draw is a different issue. 

 

 

You could do it with a heat exchanger.only about 50% efficient but better than wasting the heat

[FJMatt]

33 minutes ago, ash_smith123 said:

You could do it with a heat exchanger.only about 50% efficient but better than wasting the heat

Could a heat exchanger be fitted to the exhaust ducting from a wood drying kiln, without risk any risk from RHi rules? 

Edited February 4, 2018 by FJMatt

[Woodwanter]

26 minutes ago, FJMatt said:

Could a heat exchanger be fitted to the exshaust ducting from a wood drying kiln, without risk any risk from RHi rules? 

I would say so as the first use is (currently) eligible heat.

 

what may work is recycling heat from a certain eligible use to dry logs as a heat by product.

[FJMatt]

It's a pity you couldn't use the heat from the boiler chimney 

[openspaceman]

2 hours ago, FJMatt said:

It's a pity you couldn't use the heat from the boiler chimney 

Chalgravesteve isn't looking at the whole system, now it won't be applicable to most applications but you're getting there.

 

With wood burners you cannot cool the flue below about 110C without creating problems, but if you have a high temperature recirculating  kiln then your flue gases  have also to be hotter as there has to be a temperature drop from the boiler to the kiln. So there is usable heat after the flue leaves the boiler but it's low grade heat.

 

If the kiln is operating at high temperature and there is no heat recuperation between the kiln exhaust and the fresh air replacing it then there is also a lot of low grade heat in the now saturated exhaust at kiln temperature.

 

Hertswood's scheme is even better because the flare from the charcoal making is around the same temperature as burning wood outright so running a pyrolysis unit in series with a drying kiln and then a use for low grade heat e.g. underfloor heating slab makes good use of all the heat and saves the complication of recycling kiln heat.

 

The challenge is to do it all cheaply enough to justify the fuel saving.