How does renewable technology work?
If you have ever wondered how renewable energy works, we have a little note with all of the technologies explained, such as wood pellet stoves, wood gasification and wood burning stoves.
WOOD PELLET STOVE – How it works:
A wood pellet stove looks like a solid fuel stove or wood burner on the outside but inside it is very different. Firstly, it requires electricity to function. Secondly, the fuel that it uses, wood pellets, by their nature require continuous feeding into the burnpot, so that requires an auger. These wood pellets are stored in a fuel hopper of varying sizes, depending on the output of the stove may be 12kg – 40kg, which is filled from the top of the stove, every two to three days.
Operation Pellets are stored in a hopper within the stove. The stove is turned on, and the pellets are automatically fed into the burner by an auger, which are then automatically ignited. As the pellets burn, more pellets are fed into the burnpot. Warm air is fed through an internal heat exchanger and is convected into the room. Combustion air fan blows hot air around the fire to maintain a high temperature and enable the pellets to burn efficiently and evenly.
A flue is installed either through the rear of the wall behind the stove, or into an existing chimney. There is very little ash from the burning of woodpellets, but any ash will fall through the grate to a collector under the burn chamber. This can be cleaned out with a hoover about once a week.
All of this is controlled by a control unit, usually located at the top of the stove. This allows you to set a temperature for the stove, and once this temperature is reached, the stove will reduce the feed to the auger motor, to just enough pellets to keep the stove ‘ticking over’. Some stoves are programmable either by time or temperature, and have a timer function on the control unit, which can set the stove to come on and off on a daily or weekly basis.
There are built-in safety systems that control temperature within the pellet tank and throughout the stove generally, as well as restricting fumes output and controlling chimney pressure.
WOOD BURNING STOVE – How it works:
Wood burns from the top down, and burns best sitting on a bed of ash, with it’s combustion air coming from the top. A wood burning stove needs two things to work efficiently.
Firstly, it needs heat and so it will often be lined with firebricks, but also it is helped by sitting on a bed of ash, as the ash acts as an insulator, directing the heat upwards, into the fire.
Secondly, it needs combustion air from the top, in the form of a good supply of oxygen. There are two types of air intake. Primary Air is the air usually taken in through a control at a low level at the front of the stove to maintain combustion. It is the best way to control a stove burning solid fuels, and is only needed to start a wood burning stove, as once the fire is burning well, it will not need primary air. This control can be adjusted to regulate the air coming into the firebox. Secondary air is a stream of warm air that ignites the unburnt gases, which is known as secondary combustion. This control is typically above the door or to the top of the front of the stove. Secondary air flows downwards along the glass giving a warm air film which helps to keep the glass from blackening. This is known as ‘airwash’. Once the fire is lit a wood burning stove works best by controlling air using the secondary air control.
WOOD GASIFICATION – How it works:
The Principle: Gasification is a method of extracting energy from organic materials such as wood. The process converts the wood into carbon monoxide and hydrogen by reacting the raw material at high temperatures with a controlled amount of oxygen and/or steam. The resulting gas mixture synthesis gas or syngas is then more efficient than direct combustion of the original fuel because it can be combusted at higher temperatures. Gasification itself and subsequent processing neither directly emits nor traps greenhouse gasses such as carbon dioxide.
Components of a boiler 1.Control unit 2.Fuel chamber door 3.Forced draught fan 4.Bottom door 5.Fuel chamber 6.Primary air duct 7.Ceramic nozzle with secondary air duct 8.Combustion chamber 9.Ash chamber 10.Exhaust gas heat exchanger with turbulators 11.Damper 12.Safety heat exchanger 13.Supply line 14.Return line 15.Chimney neck
Operation of a SOLARBAYER Boiler: For heating up, the boiler is equipped with a heating damper which is operated with a connecting rod at the front side of the boiler. The interior of the boiler consists of a fuel chamber where the fuel is dried out and turned to gas. The wood-gas produced will then be lead into the combustion chamber via a nozzle. There it starts burning by adding secondary air. The hot waste gases are cooled down in the heat exchanger.