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This report provides an analysis and evaluation of the current and prospective installation/construction of a particular renewable energy. Methods for this evaluation for the installation of a logwood gasification boiler include the current construction type for this private dwelling, its current heating requirements and their current heating efficiencies. Other calculations included are total area in Meters squared (M2) for this private dwelling, the new wood gasification boiler sizing in kiloWatts (kW), recommended buffer tank in Litres (L) and the wood fuel supply required for this residence in Tonnes (T) per year.
All calculations can be found throughout this report in the sections Sizing of the technology, Resources needed and Additional infrastructure. Results of this report and further enquires to wood gasification installers/distributers shows the lack of data in relation to the uptake of this particular instillation and product. Further research has shown a bigger uptake and product push toward wood pellet boilers and consumers decisions where based on price of the product and limitation in space required for wood gasification boilers.
This report finds the prospects for this installation of the chosen product (wood gasification boiler) very positive. The major decision for the chosen product was that the home owner has access to a sustainable supply of wood logs. Also a major factor is this premise has the capacity to house the new logwood gasification boiler, buffer tank and the existing fire logs without any compromise for space. This report also takes into account the fact that this evaluation that was conducted has limitations. Some of the limitations include:
The current sale of wood gasification boiler to the domestic markets in Ireland is limited compared to Europe. While conduction this research a report was located that was carried out in Europe. Its focus was on small scale biomass use which included stoves, inserts, burners, boilers and boiler houses. On their web site they had a calculator to rate the various boilers manufactures and their boiler products CO2 emissions.
Wood gasification boilers have been highlighted on varies product web site as having high energy ratings when they are still in the process of getting certification.
This technology is still been improved and the costs in relation to wood gasification boilers, instillations and rising oil price may see this technology become more popular and may reduce in price.
Introduction of site been investigated
A retrofit for this private residence is for an installation of a renewable energy source. The chosen renewable energy source is a logwood gasification boiler. This heating system will be installed at Bengurragh Square, Cahir, Co Tipperary. This home was constructed pre 1960 and is mass concrete, 2 storey end terraced construction. As of 28th June 2011 this residence has a building energy rating D2 which is equivalent to 286.42 kiloWatt hour per meter squared per year (kWh/m2/yr). The heating energy source for this dwelling is a duel system which is oil and solid fuel. Oil is rarely used, as the boiler its-self is over 15 years old and due to wear and tear it is anticipated to be less than "70%" efficiency today (Sustainable Energy Authority of Ireland (SEAI), 2012a). This boiler is fitted with a thermostat and is set at 27oC.
The main heating source for domestic hot water, space heating and central heating is a back boiler. This back boiler was installed the same time as the oil burner. This high output back boiler has an efficiency rating of "approximately 40-50%" compared to an open fire which operates at around "20%" efficiency (SEAI, 2012b). A room thermostat is fitted located in the hall. This thermostat works in conjunction with the oil heating. Once the room reaches the desired heat this turns of the oil burner.
As this homeowner has a steady and readily available wood source it was decided to invest in a logwood gasification boiler. A logwood gasification boiler is capable of much more higher efficiencies than other types of boiler meaning it will burn less fuel to heat this dwelling. Boilers with an efficiency award of over 90% are available on the market. Under current building regulations it is a mandatory requirement that when replacing boilers they must have a minimum efficiency of 86% (Sustainable Energy Ireland (SEI), 2008). As the existing old boiler is 15 years replacing it with a wood gasification boiler would be more cost-effective. Renewable or low carbon heat sources should also be considered as a replacement for the oil burner. Biomass boiler burns renewable fuel such as firewood, wood pellets and therefore is less damaging to the environment than fossil fuel. Biomass boilers usually require more fuel storage space than oil boilers.
Overview of the current status of logwood gasification boilers in Ireland and Europe
Solid biomass is mainly used in Ireland for thermal energy purposes only (SEAI, 2012c). From 1990 to 2011 there has been a 9.5% increase in the Irish residential biomass energy markets. This relates to 0.5% average annual growth. The largest growth rate increase of 18% was between 2005 and 2010. Table 1 gives a summary in the trends for renewable heat in the Irish residential market.
Table Trends in the Irish residential renewable heat markets (SEAI, 2012c)
% average annual growth rates
The use of stoves as the main or secondary heating system is common in Europe. In 2009 the European Communities (EC) Published results on Sustainable, comfortable and competitive biomass based heating of private houses. This study focused on small scale biomass use which included stoves, inserts, burners, boilers and boiler houses. The study included equipment for producing fuels (splitters, chippers). The aim of this project called BioHousing was to promote and manufacture sustainable BioEnergy systems for the use in private homes. Furthermore the BioHousing project was to highlight that biomass based heating systems are appropriate alternative for heating private houses.
With the aid of a multilingual Heating Tool it is possible for the user to compare the energy and investment costs of the heating forms in several European countries. This makes it possible to estimate the heating costs of different kinds of houses and calculates the average CO2 emissions for the different heating system. Woody biomass contributed 1,334 Petajoules (PJ) of energy in households in the European Union 27 member states in 2006, of which more than half was traditional firewood (Jyväskylä Innovation Oy, 2009). Table shows the consumption of wood as a fuel source in the domestic sector within the European Union.
Table Calculations in Petajoules (PJ) for wood as a fuel source in the domestic sector within the European Union.
Technical principles and components
Logwood gasification boilers can burn firewood in the form of (logs) and briquettes which can be either (turf or recycled woodchip compressed in to briquettes). The gasification boiler burns the wood in a very slow and efficient manner. Through the gasification process and the application of heat which draws moisture from the wood, then breaks up the components of wood into gas. These gases burn off in a controlled and regulated chamber.
Figure Cross section of a logwood gasification boiler (google.com, 2012).Within the fuel chamber a gasification fire is maintained and controlled by a primary air intake. The boiler is regulated by electronics which is on the top panel and this also regulates the gasification rate by the primary air intake with the aid of a fan. The wood gas is then drawing downwards into the ignition chamber. This prevents the wood stacking in the fuel chamber from igniting gases in an uncontrolled manner. Therefore it is possible to have a log wood gasification boiler which has the capacity to hold large amounts of wood burn up from the bottom slowly and for long period. The Eco Angus (2012) 25 kW boiler has a log chamber large enough to burn wood for up to 12 hours. http://t0.gstatic.com/images?q=tbn:ANd9GcQTq7hm-oS20JWZdIcFf-cn8cGBTlEgr8tBGT9NqPe723lAz8PNKg
To calculate the boiler size required for this 300 m2 residence, we need to take 50 watts to heat every square metre of this domestic residence and add 3 kilowatts for domestic water use. 350 m2 x 50 = 17,500 watts (divide this by 1000 to get kilowatts) = 17.5 kW and add 3 kW for water will give an approximate boiler size of 20.5 kW. A boiler that is been considered for this dwelling is an Angus Super Gasification Log Boiler. The nearest model range is a 25 kW and its heat efficiency is rated 92% (Eco Angus, 2012).
The new boiler size is related to this dwelling's individual heating requirement. It is required that a log gasification boiler be connected to a buffer tank. The volume of the buffer tank will depend on the capacity of the boiler. For every kiloWatt (kW) of boiler power output you should have 55 litres of buffer tank storage (SEAI, 2010).
For a 25kW wood log gasification boiler, the recommended buffer tank size would be approximately: 25 kW x 55 litres = 1375 litres. A 1500 litre tank will be installed on this premises as this tank size is readily available.
To calculate the wood fuel supply required for this residence we need to divide the kW output of the boiler, by the boiler efficiency to get the actual fuel input energy required.
Eco Angus logwood gasification boiler = 25 KW output, 92% efficiency, running for 4,380 hours per year (approx) kWh required = 25 / 0.92 x 4,380 = energy input of 113529.6 kWh per year. Sustainable energy authority of Irelands (no date) best practice guide Wood Burning Technologies for Irish Consumers has calculated (approx) Wood log energy content 4.0 kWh/kg with 20% moisture content.
This residence Annual wood log requirement can be calculate. Energy input = 113529.6 kWh/yr divided by 4 kWh/kg energy content for wood logs = 454118.4 kg/yr, now divide by 1000 as there is 1000 kg in a tonne = 454.1184 tonnes/yr.
Use of energy produced
The energy that will be produced will be utilised as the main heating source for domestic hot water, space heating and central heating for this private residence.
The housing for this instillation is an existing premise that is been used as storage for the oil burner and seasoned fire logs. This premise has the capacity to house the new logwood gasification boiler, buffer tank and the existing fire logs without any compromise for space. For this installation of a logwood gasification boiler there will be the requirements for the following extra materials and connections.
Eco Angus 25 kW boiler x 1
Mixing Valve Unit x 1
Accumulation Tank 1500 Litre x 1
Expansion Tank 150 Litre x 1
Thermal Discharge Safety Valve x 1
Safety Unit x 1
Cap Valve x 1
1, 5 meter x 250 mm diameter double walled flue lengths connections x 2
4 lengths of ¾ inch copper piping.
Note: most of the fittings can be reused from the old oil boiler and incorporated in to the wood gasification boiler. New fittings will be purchased while the instillation is been fitted.
With increasing fuel prices home heating costs have fluctuated. As a retrofit this choice of the heating systems formed one of the most important and long-term decisions this home owner had to make. We must try to use energy in a sustainable and cost-effectively manner without compromising the comfort of our homes. In addition home owner's choice their heating systems based on costs and comfortableness of living. Oil related heating systems are compact and easily installed including storage tanks for heating oil.
Burning fossil fuels releases carbon dioxide (CO2) into the atmosphere which contributes to climate change. Unlike biomass heating systems that use renewable sources and are carbon neutral can be bulky due to extra requirement e.g. buffer tanks and wood storage facilities. In addition some biomass heating systems may need to manually filled with wood logs or briquettes they may also require manual cleaning e.g. ash removal. It is also recommended during summer months that the gasification boiler be ignited every 2nd or 3rd day in order not to lose the stored heat energy in the buffer tanks.
Biomass heating systems also have higher instillation and purchase costs over oil heating boilers. Wood gasification boilers have higher purchase costs over pellet boilers. The reason for purchasing wood gasification was that the home owner had space for the instillation but also had a sustainable supply of seasoned timber which will reduce costs on timber purchasing.