Tag Archives: log boiler

What is biomass fuel – wood pellet boilers


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Biomass boilers are well recognised, but what do they burn?

In the UK the introduction of the Renewable Heat Incentive has meant that the definition of biomass fuel has become more difficult to understand. The main driver for this are the emissions that the boilers have in addition to CO2 being of acceptable levels.

These limits are 30 grams per gigajoule (g/GJ) net heat input for particulate matter and 150g/GJ for NOx.

Each boiler range has to be tested with the fuel that is going to be used within it. Each fuel has a definition.

Wood Pellets

Pellets are the most straightforward for a homeowner as there is an ENPlus quality standard market on bagged pellets or on the website of the pellet producer.

http://www.enplus-pellets.eu/

All accredited wood pellet boilers have been tested to a European Standard EN303-5, met the standards of the UK Microgeneration Certification Scheme, and have a valid emissions certificate. Key to this is that the boilers were tested on ENplus pellets. So these are the only pellets that you can buy and use. To claim your RHI you will have to keep records and be able to show that you are burning ENplus pellets.

Wood Pellet Boiler Product Example

Pelleburn 15kW wood pellet boiler  will burn ENplus pellets only. When it does this it has been tested to show 9g/GJ for Particulate Matter and 81g/MJ for Nox. You can find a copy of the emissions certificate here. http://rhieclist.org.uk/wp-content/uploads/2014/04/NES_PLB_RHI.pdf

Wood logs

Logs are measured by moisture and by whether they are “virgin” or used. This potentially creates 4 categories.

Virgin timber – Very dry or kiln dried logs or logs with less than 25% moisture

Used timber – waste wood with no contaminants e.g. Pallets, or waste wood with contaminants e.g. MDF, Plywood, Chipboard

Wood Logs product Example

Pyroburn 30kW gasification boiler can burn wood with up to 25% as it was tested on wood with a moisture content of 12.01 percent. Had the wood in testing been much drier, e.g. 6% then there would be a limit of 12 percent dry wood in the boiler. http://rhieclist.org.uk/wp-content/uploads/2014/05/NES_PB_RHI.pdf

Wood burns much better and cleaner when the wood is dry. The testing process and regulations ensures that if you buy and use a log boiler you take care of what you put in it. For instance the following are attractive, but not allowable

  • Newly cut timber in excess of 25% moisture.  Fuel that you “find” in woods, or offcuts from timber merchants, or branches from a tree surgeon. This fuel will not burn well. You do not get the heat but your neighbours get the smoke.
  • MDF, Chip board or painted wood may burn, but it gives off lots of fumes. Unless there are very specific cleaning processes within the boiler to deal with paints and glues then the fumes produced will be toxic. This category of fuel (B2) cannot be burnt in the majority of boilers, and certainly no domestic or small boilers.

Logs can transformed into wood chip and sawdust and is subject to the same categories as above. Wood chip is generally quite bulky, so produced in local areas rather than pellets at one or two places. It varies in quality and next year (2015) suppliers will need to state that their fuel meets both a moisture standard and has no contaminants. We are excited about our new boiler The CB 160 which will shortly be released into the UK market.

Sawdust does not burn well and can cause back burning (fire can go back through the fuel delivery mechanism) boilers will specifically state whether they can burn sawdust or not. For instance the Catfire range of chip boilers can burn sawdust and has a mechanism to prevent backburning of sawdust.

Sawdust or shavings can also be made into briquettes easily (and pellets, but not so easily) that can burn very well and burn in most boilers.

As part of understanding the moisture content of the wood you would need to have an adequate storage and inspection process. For instance with pellets you need to check that there is not too much sawdust. For wood you will need to store so that the wood can mature. For chip you will need to keep it for a short period to ensure that it does not compost. Other than pellets, you will need to get a moisture meter to make sure that your wood is less than 25%.

Summary

If you want to install a biomass boiler you can only burn the fuel or fuels that it has been tested with. You will have to buy these fuels from accredited suppliers of biomass products from http://biomass-suppliers-list.service.gov.uk/find-a-fuel .

If you want to use your own stock of fuel you will have to self-certify and keep more detailed records. Again the fuel must relate exactly to the fuel tested on the boiler.

If you have questions about any of the above then please get in touch as we would be happy to help.


Domestic Renewable Heat Incentive – update


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The domestic Renewable Heat Incentive is currently waiting for its final details from the government. These are expected during the summer of this year with the scheme going live early in 2014.

Further details can be gained from here

Among the key points are that the government is reconsidering the tariffs. This includes a possibility of increased tariffs for some technologies.

Currently the domestic tariff for biomass is projected to be between 5.2 and 8.7p per kWh over 7 years. For a 20kW installation this could mean £16000 over 7 years.

This does not compare as well as the non domestic Renewable Heat Incentive where the same installation could get a similar tariff over 20 years ie in excess of £40,000. However you would probably pay for your installation and financing as per the government report depending on the boiler and facilities that you want from your boiler.

Whilst we are waiting for the government to announce what they want to do we are finding that customers are changing or tailoring their installations to suit the delay.

In discussion with customers have found that a key difference between commercial and domestic is the issue of a pellet store. On smaller installations it is easier to poor pellets more frequently into a boiler that has an internal hopper or a smallish hopper that sits next door to it. If you want to build a hopper or buy a larger hopper the hoppers can be reasonably priced. For instance an 8 tonne external hopper can be about £2000. You then have to consider how to feed the pellets from the store to the auger. This can be a further £950 for a flexible auger of 3 or 4 meters. Alternatively you can use a vacuum system, where prices can start at £2000.

The payback of a boiler without a large hopper is much greater, but you have to poor in pellets on a more regular basis. It is possible to do this in the short term with a view to putting in a larger hopper as and when the RHI is confirmed.

The other trend we have seen is that wood boilers are being more carefully considered. For instance logs can be purchased in the South West from Longleat

Log Type Price
Hardwood Logs from £130.00 per tonne Delivered
from £116.00 per tonne Collected
Softwood Logs from £101.00 per tonne Delivered
from £87.00 per tonne Collected

These prices are considerably less than wood pellets and affect the payback of an installation project.

Mass produced fuels have gone up in price over the winter with oil reaching 65p a liter as the cheapest alternative to gas.

Our WBS boiler can accept a wood pellet burner. You can start with a log boiler and upgrade to a pellet boiler at a later date.

Both the above ideas are a move to keep costs down as te main driver for everyone is cost.

At Ecobuild this year we exhibited our Pyroburn product that gives an alternative to a straight log burner.

Log gasifying boilerIt is available as an 18, 25 and 40 kW boiler. It is attractively priced and can be an alternative to the WBS active range.

The other development is the “Duo”, now a live product, we visited the factory 12 months ago to see the product in the final stages of development.

duel chamber burning boiler

 

You can see a Dual chamber boiler video by following the link.

So we are finding that fuel prices are increasing – and this makes biomass more attractive, and logs or alternative fuels even more so. Well priced boilers and installations are met with approval, however we would all like to see a final version of the Domestic Renewable Heat Incentive confirmed soon!


Log Burning Boilers or Wood Pellet Boilers?


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If you are considering “biomass” as a heating system the most obvious choices are between log burning boilers and wood pellet boilers.

For some the clear advantages of log boilers are:

  1. Cost of installation
  2. Cost of fuel
  3. Sustainable use of wood

For others the clear advantages of pellets are:

  1. Automation of heating
  2. Higher efficiency
  3. Pellets are a waste product
  4. Space saving

Cost of Boiler

Log boilers such as the WBS active are MCS accredited and burn wood up to 90% efficiency. The boilers start at at a little over £1000 (20kW WBS) and this is a lot cheaper than the Pelleburn wood pellet boiler that starts at £3500.

Cost of Extra Water Heating

Wood pellet boilers modulate. This means that they can adjust to produce the  amount of hot water that you need to store for heating. Log boilers need to heat water when they are burning otherwise there is nowhere for the heat to go. This is often in the range of 30-50l per kW.

For instance a 20kW log boiler will need to heat 600-1000l of hot water.

You could choose an accumulation tank or a thermal store to do this.

An accumulation tank or “buffer store” can used to store the heat. They are well insulated and once heated can distribute the heat without the need for the boiler to be “on”. A 1000l buffer store is nearly 1 meter diameter by 2 meters tall. This does mean that you need to find space for this. The buffer store will be an extra £1000+ and there are extra plumbing costs in installation.

A thermal store can incorporate a hot water tank and heating hot water in one tank. A “tank in tank”. Assuming you need hot water for baths and showers, then you will need a hot water tank. Some houses already have these, some do not. Others are old and need replacing. A thermal store is a good solution if there is a need for a new hot water tank.

Wood pellet boilers do also benefit from the use of accumulation however they can burn efficiently for shorter periods of time and so need less water to heat. On smaller systems it is possible to work without one, however your boiler may need to come on more often. Using an accumulation tank may prolong the life of your parts.

In summary – log boilers need more accumulation than pellet boilers, and this will increase costs of installation. This will vary depending on the installation.

Space Needs

Wood pellet boilers that are completely automated generally infers a large pellet store that can be filled. This can take up a lot of space e.g. 10m3. This has to be dry and purpose built. Whilst there are pellet stores that can be outside for most homes the choice is between a top loading boiler (ie no storage) e.g. an MCZ Musa , an indoor pellet hopper e.g. Pelleburn or a purpose built hopper. This means that the storage needed varies in size depending on the location and budget. For those tight on space a 1.5m by 1m space is generally more than enough.

For logs the space is larger for the smallest boilers. The boiler is larger, needs more space for a larger flue, and accumulation tank. This is typically 2.5m2

Cost of Fuel

Often the most immediately available fuel is more expensive on the internet. Pellets do range in price, but are frequently £200 per tonne or 4.5p per kWh. (Oil prices were 65p per liter (6.5p per kwh in March and are currently 53p per liter, 5.3p per kWh)

Logs vary more in price and this also varies considerably regionally. For those with a ready supply there is the cost of cutting logs ie your time, or alternatively you can get fuel delivered often at £90-100 per tonne 

This makes the cost of logs about half the price of pellets.

Efficiency and Sustainability

A WBS log boiler can be 90% efficient and a pelleburn pellet boiler can be 94% efficient. Some of the efficiency difference can be put down to pellets being dryer and only pulp, ie no bark.

If your logs are from your immediate surroundings then there is no transport or significant processing costs. In addition some pellets have been artificially dried. Whilst not significant, pellets are transported and there is a manufacturing cost that involves drying wood pulp.

If your logs are the result of forestry or woodland management and the wood is offcuts ie cannot be used for other things, then it is sustainable. This is also true for pellets e.g. if as part of making paper there is sawdust and pulp left over then this waste product can make pellets.

There is a strong argument for logs in terms of sustainability and transport. Unfortunately this does not work for many people due to the availability of local woodland management for our homes and logs are not economic to transport.

Renewable Heat Incentive

Currently the non domestic Renewable Heat Incentive pays the same incentive for log boilers as pellet boilers.

A 30kW log boiler May get RHI payments of  30 (Size of boiler) X 8.3 (higher tariff) X 1314 hours = £3271 per annum.

For an installation of logs or pellets costing between £7-10,000 this would payback in under 3 years before you take into consideration the lower cost of fuel.

A Possible Compromise

If you are finding it difficult to decide whether you want logs or pellets. For many the logs do appeal but there is the extra work involved and will you be happy doing this?

The WBS range of log boilers all come ready to fit a pellet burner ie you can convert your boiler over at a later stage. The pp and pelle ranges of burner are easy to fit and with some minor adjustments to your settings you can be burning pellets.

For more information do get in touch with us using the form on the right hand side or by phoning 01225 580 401


Renewable Heat Incentive – Farms


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Renewable Heat Incentive eligibility is not clear for farms and similar organisations. However we believe that it is possible for a farm to qualify for the non domestic Renewable Heat Incentive to heat their home and an acceptable farm building as part of a district heating system.

Ofgem provide a detailed guide Ofgem Website and helpline support 0845 200 2122 to clarify questions and the information here is a guide. Each scheme would have to be approved by Ofgem.

Difficulty 1 – Business rates

Farmers do not pay business rates and this is the way that Ofgem defines a “building”. Therefore applications will have to show that the building is indeed a building that is exempt from business rates and used for agricultural use e.g. farm office. This could be a letter from the local council.

Difficulty 2 – Complex heating systems

If a farm house and office are 2 buildings then they are almost certainly separated and will need some form of well insulated underground heating pipe. There is a small heat loss from this, and as such the payments need to be based on the delivered heat. In order to make this happen meters need to be placed inside the relevant buildings where the pipe has to travel between one building an another.

If there is a back up heating source, such as an oil boiler, then then the heat produced from this will also have to be measured, as will the heat produced from the renewable source e.g. log boiler.

Therefore is is possible for 3 or 4 class 2 heat meters to be needed as part of an installation. This will increase costs accordingly.

For instance a 20kW log boiler in a “complex” system may cost between £8-12k to supply and install.

If a farm used 1314 hours of heat during a year they could gain over £43,000 (1314*8.3*20)

If you consider a farm may be in an off gas area and be making significant gains by burning biomass rather than oil or LPG then this is an excellent investment.


Renewable Heat Incentive Tariff – Non Domestic Adjustment


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Here’s a quick rundown of the renewable heat incentive tariff adjustment for non domestic heating.

Small commercial biomass tariffs have been adjusted as of 1/4/12.

From the previous rate of 7.9p the new rate is 8.3p for the first 1314 hours.

For instance if you installed a district heating scheme for an agricultural building and a farm house needing a 20 kW log boiler then your payments could be:

20 * 8.3 * 1314 (hours used) = £2181 per annum for 20 years or £43625 in total

The log boiler would need to be MCS accredited, along with the installation.

A standard log boiler installation tends to be between £7 and 10k.

If the installation is “complex” then there would be extra metering costs that would have to be taken into consideration.