Understanding Wood Pellet Boilers – A simple guide

April 30, 2008

What are wood pellets?

Wood pellets are small pellets of compressed saw dust. Simply put saw dust is a by product of other more lucrative wood processing. This saw dust is dried to a specified moisture content, and compressed by a very high pressure machine. Generally no glue or binding agent is required other than the sap from the timber itself.

The benefits of wood pellets are

  • Its easy to transport
  • It is clean
  • It complies to standards. Things which have standard sizes, shaped and moisture content can easily be designed for

So these pellets, how do they get to the boiler?

No, a shovel is not required. The pellets are blown from a delivery truck up to 20m to a storage unit. In the past there has been a lot of hassle with dust, but this was largely down to the use of agricultural feed trucks being used to deliver the pellets. As dust is not really an issue for agriculture, they did not have dust minimisation technology, and it was a mess. If you use one of the large suppliers these days, there is little problem.

So the pellets are in the storage unit… what now? Well the next stage is getting it to the boiler. The simplest solution here is to use a screw system. These systems turn very slowly and draw the pellets from the storage unit to the boiler.

Understanding Wood Pellet Boilers

And.. Combustion

Combustion… Explain?

Wood pellet boilers are fed into the “burner” where they are burned. The burner in all boilers does much the same job. It’s a place where the fuel is mixed with air to provide the optimal conditions for combustion, and lit. Before you know it the combustion gases are travelling through the heat exchanger where it heats up the water.

Understanding Wood Pellet Boilers

Understanding Wood Pellet Boilers

Heat exchanger

The flame from the burner, and the resultant combustion gases escape into the boiler, transferring their heat to the water circulating through the heat exchanger within the boiler. The heat is then distributed the house using a wet system. In most cases water flows through the heat exchanger in the boiler, absorbing heat from the flam and the combustion gases. This hot water is then circulated around the house to radiators, underfloor heaters and hot water cylinders.

For more infor See  my boilers post

Thanks to





for the pix!

Free wheeling in your car

April 28, 2008

I’m a fan of getting that extra mile out of a tank of petrol (well diesel… but ya know), and as such have been known to allow my car to freewheel up to lights… I mean come on… surely freewheeling (despite the illegalness) has to be the most efficient… right?

Well it turns out… NO…

If you take the car out of gear, the engine needs a little fuel so it doesn’t conk out. If you leave it in fuel the idea is that the engine is kept going by the inertia, and so doesn’t need fuel.

So its like this, if you are going to free wheel for a very long way… then it will make sense. If it’s a shorter distance like up to the lights, then leave the car in gear. The engine will actually take energy out of the wheels to keep going, and so use less fuel. It will also slow the car a bit, and so you’ll need less breaks… do the savings ever end?

Grants for Insulation

April 25, 2008

The post your looking for is here

Today Eamon Ryan announced the launch of the long awaited home insulation grants scheme. Only a pilot at the moment (North Tipp, Clare, Limerick and Dundalk), it should be launched nationally in 2009. The max grant is €2,500. The pilot bit is a bit of disappointment, but probably sensible as it will allow a supply chain to get into shape. Technologies which can be included are attic insulation, interior or exterior wall insulation, low emissions double-glazing, heating control or a range of other energy efficient works. Regular readers of this blog are aware that I belly on about insulation a lot, and I really encourage everyone to take part in this scheme. If you’re unlucky enough to not live in Clare, get ready for the National launch.

Fair play to Eamo for this one, looking forward to seeing the nods of approval his way from quarters that are generally critical of him!

Earth Day – Colbert’s Response

April 23, 2008

Yesterday was Earthday. That means a day to celebrate earth… yes?

Thanks to Colbert

Static Electricity… the future?

April 21, 2008

Options for Domestic Electricity Generation

April 18, 2008

Wednesday saw an announcement by Eamon Ryan that they are working on allowing houses in Ireland to export Electricity (not here yet… but working on it). This has been resisted by the ESB forever, and for not crazy reasons… but anyway… here a quick one on options for generating electricity in your home.

Domestic Wind Power: Wind power is a good option for Ireland. Payback (time when savings pay back the cost) is in the region of 10 years or so, which isn’t really great… considering they don’t last forever… Issues with them are safety of installation. So them actually falling down… And the electrical side… them killing you or an electrician…

Solar Photovoltaic: PV is the great white hope of electricity generation. They convert light from the sun to electricity… and if the sun stops shinning… we’ve got bigger problems… Payback in Ireland is worse than Wind… more like 20 years, but otherwise… they are just so great!!!

Hydro power: Water from rivers. These are great, but you need the perfect fall of water, and at moment damning any river is sooo against the rules, that it is unlikely that anyone will manage make use of them.

Micro CHP: Combined Heat and Power Units are pieces of equipment that combine an electrical generator and a boiler. They are really efficient and good and stuff, but the problem is that you need to require heating and electricity at the same time. People generally need heating and hot water in the morning, before they get up, so the only way they will work here is thanks to the new announcement by Eamo . As for payback, well we’ll see. SEI have a trial going on at the moment.

And that’s it… nothing better than a 10 year payback. Even Tony will agree that the heating systems beat the socks off them. So my advice.. go for a wood chip boiler…

Or insulation…. Always insulation….

Attitudes Towards Energy Efficiency

April 10, 2008

The majority of the work I do relates to renewable energy’s less attractive, more financially sensitive brother, energy efficiency. Attitudes towards Energy Efficiency is an interesting topic (well I think). Energy Efficiency is about achieving goals, using less energy… Simple as that. So the ways that can be done is

  • Equipment that uses less energy (a technical solution)CFL bulbs, putting in insulation etc
  • Using Equipment for less time (a control solution)Sensors and timers
  • Reducing the quality of service required from equipment to a more appropriate level (an engineering solution) – Turning down the heating

Now the way people see these things is quite different, but truth is, the type of efficiency that dominates peoples views… is the last one. And people associate a reduction in the quality of service they get… with being poor. People associate having their houses really warm, really well lit, driving big cars, having double size fridges… all that… with affluence. And people like to project affluence.

So… that’s why I’m particularly interested in a proposal I heard the other day. At the moment Irish Cars registrations plates are of the format 07 CE 2344. The 07 refers to the year of the car. CE refers to the county of registration, and the other number… well that’s just a number. Now its been pointed out to me in the past that having the year on the registration encourages people to buy new cars… to show off like… everyone wants to show off their new car. So, this proposal is to change the year number with an energy rating. The idea is that people will want to show off how energy efficient their car is…


Energy Efficiency is at a disadvantage, people think that doing it… makes you look uncool/poor/less attractive to women/men… so using something like this, which makes gas guzzlers wear a dunce hat… is a good idea

Energy Efficiency is a great idea on the merits of the energy/money/CO2 saved, and shouldn’t need to use psychological crap like this.

This is a similar plan what Toyota did with the Prius… It looks different from other cars so green people can show off how green they are.

We could also discuss how Energy Efficiency, encouraging people to consume less… is not the Capitalist/American way…. And so cannot/should not succeed. This is also an interesting discussion (well… again… to me)

So… opinions???

Blue man group

April 4, 2008

My printer… and the electricity it consumes

April 3, 2008

The other day I was trying to get my something that had fallen down behind my printer, and noticed a little hum coming from it. I always switch off my printer so was a bit confused. Anyway long story short… Here are the measurements on how much electricity my printer uses at different times. It is not what I expected


I use a lexmark x2470

Simply by plugging the printer in, it consumes 2.8W. Switch it on… 3.2W. Start printing… 9W. So what does this mean. Well two things. Firstly leaving my printer (and maybe your) switched on is not that big a deal. The important thing… is don’t plug it in…

It also shows that the bulk of the electricity my printer used in the last few months was just by being plugged in… We’re talking 99% or so

I think this is incredible. So if I want to be energy efficient, I need to plug out the printer, or switch off the socket to cut the energy consumption.

Lexmark… I’m shaking my finger…

Understanding Domestic Wind Power

April 2, 2008

Domestic wind power is another renewable energy technology which is gaining popularity. Different systems run in slightly different ways, but the most common systems run like this.


Domestic Wind Turbine

Electricity is generated by the wind turbine. The electricity from it smoothed out by a piece switch gear, and then sent to the main fuse board. The idea behind smaller (and most common) domestic wind turbines is that will displace your “base load” electricity. That is to say the electricity it generates (75-250W) is less than the minimum amount of electricity your house is using. So at all times you will consume all of the electricity it is making, and so none will ever escape out onto the national grid. This is good because the value of the electricity you buy is quite high (probably 16c or so) while the value of electricity supplied to the market is quite low (about 6c).


Domestic Wind System


Some systems use batteries to store electricity for use at peak times, but batteries are expensive and bulky, and adding them to a system adds to inefficiency by a good bit. The bulk of this inefficiency comes from converting the electricity to DC, for storage, and then back to AC, for use in your house (see the inverter bit below).

Turbine blades

The 3 blade wind turbine we see most commonly has been chosen due to a bit of physics showing that it takes the most energy out of the wind possible. Older turbines which have more blades have since been proven to be less effective over a range of wind speeds. The essence of the thing is that trying to block the wind is the wrong way to go about it, the best solution is to “catch” the wind, and be dragged along by it. Hence 3 blades, and also the particular pitch (angle) they are set at. In very large turbines the blades can be adjusted to be at the optimal pitch, but that would be overkill for smaller turbines.


Some more expensive turbines use gearboxes to optimise the energy being extracted from the wind, working no different to the gears on your bike. Cheaper and smaller ones often don’t bother with this however as it adds to the cost and provides more things to break.


Generators and alternators produce electricity from the rotation of the turbine motor. A generator produces Direct Current (DC) power while an alternator produces Alternating Current(AC) power.


In systems where batteries are included, inverters are added. Inverters are pieces of equipment that turn electricity from D/C (like in batteries) to A/C (like grid electricity).


Yaw systems are used to align the turbine to the proper angle of the wind. Most domestic wind systems use a simple tail vane to do this.



But do they work

Well first, you must accept a fact about the wind… it is not always there. So once we’re got that out of the way… then yes… they do.

Because wind is an intermittent resource, you can’t expect it to supply all your electricity needs. The idea with wind is that it will generate electricity when it is windy, and when it is calm, you’ll need to use another energy source. So if you buy a wind turbine, and see that it is rated to generate 100W, then you can hope to get an average 33W from it. If it is rated to 750W, then you’ll get an average of 250W. Average does mean average though… So it might be generating 0W, or might be generating 600W, or any variation.