Technical Information

Comparing Hotties Heatlogs with other firewood

 
Total Heat Output
4,900 kw/h/t

Total Heat Output
3,980 kw/h/t

Total Heat Output
3,400 kw/h/t
  KILN-DRIED WOOD LOGS SEASONED WOOD LOGS
    Hardwood Softwood Hardwood Softwood
Price £395 (£395/m3) £385 (£141/m3) £575 (£141/m3) £300 (£120/m3) £443 (£120/m3)
Quantity 1 tonne (1m3) 1 tonne (2.73m3) 1 tonne (4.08m3) 1 tonne (£2.5m3) 1 tonne (3.69m3)

Moisture Content

around 5% 20% 20% 30% 30%
Heat Output 4.90 kw/h/t 3.98 kw/h/t 3.98 kw/h/t 3.40 kw/h/t 3.40 kw/h/t
 
Cost £395 £458 £682 £356 £526

Hotties Heat Logs compare favourably with other household fuels. If you compare them directly with fresh seasoned wood, you will see you get far more energy density for your money. Why pay for water when you can buy dried wood with a uniform moisture content of around 5%.


Comparing Hotties Heatlogs with other fuels

  Fresh Wood Seasoned Wood Coal Heating Oil
Water Content % 50 15-20 5** 6? Negligible
Energy Density by 2.23       3.98 4.90 7.70 11.80
Ash Residue % 1.15 - 2.0 1.0 0.4 - 1.0 6.75? 0
Volume of One Tonne (m3) 3.5 - 5.0* 3.0 - 4.0* 1.4 1.13 1.0
Origin/Enviro.impact Woodlands Woodlands Reycled Mining Drilling/Refining

* Varies with species
** moisture content is indicative, normally between 4% and 6%
? indicative averages for bitumous coal


Hotties Heatlogs Heat Output Charts

The following chart compares the average radiant heat output of Hotties heatlogs, with a regular bag of coal, in controlled burn tests carried out over a period of 150 minutes.


Average Radiant Output

Source: Jetmaster Fires

Increasingly, traditional wood logs are being sold with a great variation in their moisture content, which in turn has a significant effect on heat output.

For example, fresh cut wood logs can have a moisture content in excess of 60%, seasoned wood logs would typically be between 25-35%, kiln dried logs are under 20%.

In order for the Hotties manufacturing process to work effectively, the initial moisture content of the wood must be around 10% so that post manufacture the Hotties Heatlogs are always around 5% moisture.


Heat output (NCV) relative to moisture content of wood

Source: European Wood Fuels Handbook


Hotties Heatlogs - better value than ordinary wood logs?

Questions you need to ask about your wood fuel:

  • How is your 'load' of wood logs measured?
  • Is its moisture level known (and verifiable)?
  • Is it hardwood or softwood, and what species?

Increasingly, traditional wood logs are being sold by the 'cubic metre' because it is difficult to compare weight due to the great variation in their moisture content, which in turn has a significant effect on heat output.

  • Fresh cut wood logs can have a moisture content in excess of 60%
  • Seasoned wood logs would typically be between 25-35%
  • Kiln dried logs are under 20%.
  • Hotties Heatlogs are around 5%

It is possible to plan out the cost/heat output comparison of wood logs to Hotties Heat Logs. The resulting tables below show that wood logs need to be very low in both cost and moisture to compete.


Softwood

  Price per m3 Moisture Content Heat Output per Kw/h Heat Cost Pence-Kw/h
£395/tonne 5% 4.90 8.06
Woodlogs at £75
equiv. £300/tonne     
20%
30%
40%
50%
3.98
3.39
2.81
2.23
7.54
8.85
10.68
13.45
Woodlogs at £100
equiv. £400/tonne
20%
30%
40%
50%
3.98
3.39
2.81
2.23
10.05
11.80
14.23
17.94
Woodlogs at £125
equiv. £500/tonne
20%
30%
40%
50%
3.98
3.39
2.81
2.23
12.56
14.75
17.79
22.42

1. Assumes 1m3 roundwood = 2m3 bulk chopped logs.
2. Assumes 13% moisture content - much drier than most wood log deliveries
3. Assumes softwood density at its average of 500kg/m3
4. To calculate tonnage of woodlogs we have multiplied the cost by 4.0.
5. Heat output varies with species.


Hardwood

  Price per m3 Moisture Content Heat Output per Kw/h Heat Cost Pence-Kw/h
£395/tonne 5% 4.90 8.06
Woodlogs at £75
equiv. £300/tonne     
20%
30%
40%
50%
3.98
3.39
2.81
2.23
6.08
7.14
8.61
10.85
Woodlogs at £100
equiv. £400/tonne
20%
30%
40%
50%
3.98
3.39
2.81
2.23
8.09
9.50
11.46
14.44
Woodlogs at £125
equiv. £500/tonne
20%
30%
40%
50%
3.98
3.39
2.81
2.23
10.13
11.89
14.34
18.07

1. Assumes 1m3 roundwood = 2m3 bulk chopped logs.
2. Assumes 13% moisture content - much drier than most wood log deliveries
3. Assumes softwood density at its average of 620kg/m3
4. To calculate tonnage of woodlogs we have multiplied the cost by 3.22.
5. Heat output varies with species.

These tables are a guide only and provided in good faith.

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