drying wood

[firewood]

Are you sure they will pay you more money the more wood you burn I know the goverment are retarded by surely thats just too stupid even from them. I can't find any definite info on this.

 

 

You could leave the front door open & all the windows & have the boiler going all the time to make loads of money! Have the house at 25C and walk around semi naked lol.

 

I suppose they are reckoning on most people paying alot for there wood so this wouldn't usually be a problem as the cost of the extra wood would be more that the payments.

 

If nick is on the non domestic scheme that is exactly what the govt is doing. I was told that using softwood at £60 a loose cube or equivalent, the scheme pays out double what you burn in wood. You are only limited by the output from your installation. Crazy.

 

http://www.kinnoirwoodfuel.co.uk

[nick channer]

If nick is on the non domestic scheme that is exactly what the govt is doing. I was told that using softwood at £60 a loose cube or equivalent, the scheme pays out double what you burn in wood. You are only limited by the output from your installation. Crazy.

 

kwfhomepage[/QUOyeah its classed as a commercial boiler.. and has to heat more than one property... wood is cut to 900mm long and the bigger diameter the better.. it'll burn for longer... when its plumbed in we're keeping the excisting oil tanks so when the heat for any reason drops below 50 degrees [i think] the boiler in the house autommatically takes heat from that...

[gensetsteve]

That's quite a high starting point for ash, it's notoriously difficult to give a general rule for a species moisture content and it can vary between parts of the tree.

 

Anyway to get where you want from 38% to 23% from an initial tonne you need to lose about 200 litres of water.

 

There's still not enough details but a couple of points, the recirculating air affects how saturated it becomes. Theoretically you maximise use of fan power when the air leaving the wood is saturated. At saturation air holds different amounts of water according to its temperature and it isn't linear. Without going into detail if you draw a graph of absolute humidity verses temperature at saturation you will see there is a point around 25C where the moisture carrying capacity starts kicking off. Below this and you have to pay to circulate a lot of air for no great drying effect.

 

A chap posting here on another forum gave some useful figures which illustrate this:

http://arbtalk.co.uk/forum/milling-forum/38987-kilning-theory-discussion.html#post610301

 

And this sort of chart contains a lot of useful information if you take the time to figure it out.

 

 

http://upload.wikimedia.org/wikipedia/commons/0/05/PsychrometricChart-SeaLevel-SI.jpg

 

 

From this you can see that it your container is uninsulated in a british winter the ~ 20 degree difference is losing you a lot of heat.

 

This has a knock on affect on your dehumidifier, which is really just a heat pump that recovers latent heat from the circulating vapour and dumps it back into the container but the container loses most of this recycled heat because it isn't insulated...

 

Aloso then consider the COP of the heat pump and compare the cost of electricity to drive it with heat from other sources.

 

Would it be better to just use a poly tunnel for 9 months of the year and not bother during the winter. We have a tunnel and it must get up above the 40's in the summer. Even in march it must be late 20's. The tunnel costs nothing to run on a daily basis.

[openspaceman]

Would it be better to just use a poly tunnel for 9 months of the year and not bother during the winter. We have a tunnel and it must get up above the 40's in the summer. Even in march it must be late 20's. The tunnel costs nothing to run on a daily basis.

 

One would need to define "better" there is little doubt in my mind that a polytunnel with mesh sides that can be rolled up, as used for lambing sheds is very energy efficient in making use of the solar drying by radiant heat and ambient air. During the summer it will dry split logs in a few weeks if the airflow through the stack is homogeneous. As I said drying logs to their fibre saturation point can be quick given the right conditions and poking in enough energy. Delivering energy is the key because you always need 0.7kWhr of heat to turn a kilo of water in wood to vapour to be carried away from the surface and in practice you have to be very good to do this with 50% efficiency.

 

Cash flow and profit may dictate something else, consider a large commercial log producer selling into retail stores in bags with a sophisticated production site. He buys in suitable firewood at between £30-40, splits and packs it for £10 and gets £750 for it when the retail chain wants it. He can process fast enough to match demand but that's only really between November and January. Does he process an average amount throughout the year and store material in a large shed or is it worth going "just in time" using casual labour, lots of energy and no cash flow problem.

[Len Brennan]

All these 'green' subsidies simply take money from the poor and give it to the rich. I can't afford £10000 for solar panels (I can't even afford a house to put them on) why should I subsidise someone who can?

[treedom]

This one:

 

 

Digital Moisture Meter Wood Timber Damp Tester Detector | eBay

 

Got it. It's great. Looking forward to testing my log stack on monday!

 

sent from my Defy so apologies for poor spelling and grammar

[NI Tree]

if the goverment were being smart they should impose that every New house has hot water panles and pv cells on a new build as the cost is only a few % of the total cost

[farmer rod]

One would need to define "better" there is little doubt in my mind that a polytunnel with mesh sides that can be rolled up, as used for lambing sheds is very energy efficient in making use of the solar drying by radiant heat and ambient air. During the summer it will dry split logs in a few weeks if the airflow through the stack is homogeneous. As I said drying logs to their fibre saturation point can be quick given the right conditions and poking in enough energy. Delivering energy is the key because you always need 0.7kWhr of heat to turn a kilo of water in wood to vapour to be carried away from the surface and in practice you have to be very good to do this with 50% efficiency.

 

Cash flow and profit may dictate something else, consider a large commercial log producer selling into retail stores in bags with a sophisticated production site. He buys in suitable firewood at between £30-40, splits and packs it for £10 and gets £750 for it when the retail chain wants it. He can process fast enough to match demand but that's only really between November and January. Does he process an average amount throughout the year and store material in a large shed or is it worth going "just in time" using casual labour, lots of energy and no cash flow problem.

 

Catweazel has hit it on the head, the economics of it depend on how much of a hurry you are in.

 

Looking at the equilibrium moisture table for wood, air at 90% relative humidity will dry wood to about 20% mc, almost irrespective of temperature. However raising the air temperature by one degree reduces the rh by about 4% so a little heat improves your air quality immensely.

 

One strategy could be to blow air all the time that the logs are over say 25%, then dont blow in the evening when the dew is falling, dont blow in so much cold air that it cools your logs over night, but if the humidity inside your container got to 85% then time for an air change, if the sun is shining blow like crazy.

 

The dehumidifier will not have much effect all the while you have fresh air being introduced and they work much better at higher temperatures. Running one will help, but it may not be the cheapest per litre of water removed.

[gensetsteve]

Get two years in front of the job and stay there let nature dry it for free. Unless you have a huge grant subsidised operation I think you may be wasting your time. With the profit on a bulk bag around £10 you will spend this on heat.

[openspaceman]

 

Looking at the equilibrium moisture table for wood, air at 90% relative humidity will dry wood to about 20% mc, almost irrespective of temperature.

 

Yes but how much air does one need to carry that moisture away?

 

 

However raising the air temperature by one degree reduces the rh by about 4% so a little heat improves your air quality immensely.

 

Agreed but it's the balance between the power to move the gases, both air and vapour, against the cost of heat. A hot dry breezy summer's day beats all else

 

 

One strategy could be to blow air all the time that the logs are over say 25%, then dont blow in the evening when the dew is falling, dont blow in so much cold air that it cools your logs over night, but if the humidity inside your container got to 85% then time for an air change, if the sun is shining blow like crazy.

 

 

The algorithm still depends on knowing the cost of electricity to blow. As blowing costs go up and heat stays cheap it pays to raise the temperature.

 

 

The dehumidifier will not have much effect all the while you have fresh air being introduced and they work much better at higher temperatures. Running one will help, but it may not be the cheapest per litre of water removed.

 

All agreed, it's pointless having a dehumidifier in an open system, they only pay in a recirculating system.

 

How many of you have a drying room with dehumidifier rather than a tumble dryer, I find it much cheaper to run. The same is true of a timber dryer, a small amount of cheap heat in equilibrium with the losses from the chamber and the dehumidifier recycles all the latent heat of the water evaporated back into the chamber. You still have the cost of moving all that air through the wood surface area and then over the evaporator of the dehumidifier and the lower Delta T between vapour and condenser the less work to pump the heat.

 

Take this to the ultimate and that's the dryer we never built because the capital cost didn't appeal to our client when gasoil prices were low.