Pellet costs and efficiencies

rayh

Recently started up Pellet Roomheater (Wodtke Smart). Have been using Canadian product packaged in Limerick and yesterday bought 2 bags packaged by Semi State peat company.
Limerick product cost me 6 Euro for 18kg or 33 cent per kg
Semi State products cost 13.95 Euro for 2 by 15kg or 46.5 cent per kg.
I have done a rough calc of the output of the Limerick product by setting unit at 3KW and I reckon 18 hours or 3KW per kg and I only starting other product. So cannot comment.
According to SEI October fuel comparision figures, bagged pellet were 32cent per kg and a Gross Calorific value of 4.8kWh/unit.
Has anybody looked into this matter?

10-10-20

It's a little unclear as to what you are asking.
There are two possible methods of calculating the heat output of a heating system - 1 is to measure the difference between the incoming air and the outgoing air at a known rate of flow - 2 is to deliver a known quantity of fuel over time, and subtract the known losses (efficiency of the burn, heat lost up the chimney...).
Assuming the heater can only use method 2 (which seems likely to me as method 1 is difficult as there may be more than one method of heat delivery - radiated & forced cooling), the inbuilt control-unit will have to assume that the calorific value of the fuel is standardised, it will not be able to measure and compensate for variance.

So, what you'll have to do is get the official energy content (calorific value) for each of your sources and work out which is most efficient for the €/Kg.

As per Wikipedia "The energy content of wood pellets is approximately 4.7-4.9 MWh/tonne".
http://en.wikipedia.org/wiki/Wood_pellets

rayh

10-10-20 wrote: »

It's a little unclear as to what you are asking.
There are two possible methods of calculating the heat output of a heating system - 1 is to measure the difference between the incoming air and the outgoing air at a known rate of flow - 2 is to deliver a known quantity of fuel over time, and subtract the known losses (efficiency of the burn, heat lost up the chimney...).
Assuming the heater can only use method 2 (which seems likely to me as method 1 is difficult as there may be more than one method of heat delivery - radiated & forced cooling), the inbuilt control-unit will have to assume that the calorific value of the fuel is standardised, it will not be able to measure and compensate for variance.

So, what you'll have to do is get the official energy content (calorific value) for each of your sources and work out which is most efficient for the €/Kg.

As per Wikipedia "The energy content of wood pellets is approximately 4.7-4.9 MWh/tonne".
http://en.wikipedia.org/wiki/Wood_pellets

Thanks 10-10-20 for your response.
Yes and its not easy on a form like this to explain all the details, but can I put the problem this way;
I have a WODTKE Smart Room Heater with water heating capacity - 80% to the water & 20% to space heating. It is possible the set the output on this device in increments of 0.5kW from 2kW up to 8kW.
I have found that an 18kg bag of pellets will last about 18 hours when the unit is set to 3.5kW and I have found 2 supplies to cost between 33 and 46.5 cents.
Two questions;
1. Either the output setting on the pellet stove or the calorific value of the product are not to specification?
2. Where are SEI getting the product costs or are we been fleeced?
Hope this is clearer

10-10-20

So, what you are saying is that 1x 18Kg bag burns at a rate of 1Kg per hour when the stove is set for 3.5kW, where you would expect 24 hours of burn-time from the bag (at 3.5kW). This is 25% lower than the expected value.

A couple of items to check - Is the fuel burning completely? You should only have a light grey ash left over. If it's dark, can you check whether the air inlet is not blocked? See if the manual talks about checking the efficiency of the burn.
There is a chance that the heater is somewhat more inefficient at a low heat output setting than it would be if it was mid or high-range. Is this discussed in the manual?

rayh

Yes, I am saying 2 things;
1. Efficiency is about 25% below expected and I am getting a dark burn - I have checked inlet and no restriction, but I intend to take some measurement on the flue. The unit does not have much literature in english and or the website www.wodtke.com , plus the Irish rep has gone to ground.

2. The prices I am getting do not reflect the average figures SEI are producing