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ResourcesIn collaboration with the National Farmers Union of Scotland a series of information leaflets have been produced to give an introduction to some renewable technologies. The leaflets require a PDF reader (for example Adobe Acrobat). Biogas
Biogas is a methane-rich gas produced from natural sources such as slurry, green waste, and waste food. Biogas can be used to provide heating, to produce electricity, or both (Combined Heat and Power - CHP). Biogas is produced by the anaerobic (without oxygen) digestion
of organic matter by bacteria. It iscomposed mainly of methane and
carbon dioxide. Biogas production has recently been established on a number of farms in southwest Scotland, mainly in response to bathing water quality concerns from untreated slurry runoff from farmland during extreme weather events. These farms use the biogas for space heating and electricity used in the farmhouse. There are also a number of commercial biogas plants in the UK, which process large amounts of slurry from several farms and generate income from the sale of electricity. Further Information
BiomassModern wood burning stoves and boilers are making wood fuel an increasingly efficient and competitive alternative to fossil fuels. Use of woodfuel is widespread in some European countries such as Austria and Finland, and is becoming increasingly popular in Scotland. If it used to replace a heating oil boiler, a modern wood burning boiler can pay for itself in less than 6 years Biomass systems can are usually designed for a particular fuel type, e.g. log, woodchip, straw, pellet or grain. Log
Modern automated log boilers are very robust and efficient, and can be an ideal solution where there is a cheap supply of logs. They are capable of burning any form of clean, dry wood, e.g. old palets, provided it is of suitable size. They typically require loading once per day, then they will burn for 4-5 hours and fill a large and highly insulated accumulator tank to supply hot water and heating 24 hours per day.
Costs vary depending on the individual site and model. Some indicative costs for log boilers, including installation, flue, controllers, valves, and accumulator tanks are given below (excluding VAT):
Pellet
Wood pellets are made from compressed sawdust and are a relatively energy dense and free-flowing fuel. They produce very little ash, and there are a whole range of automated pellet stoves and boilers, from individual stoves suitable for rooms, through to boilers providing central heating and hot water for the entire house.
The typical costs for a automated pellet stove suitable for heating
a room is around £3,500 ex VAT.
WoodchipWoodchip can be produced from any source of clean wood, such as forestry thinnings, recycled pallets, timber offcuts etc. Wood chip systems require less manual handling of fuel, and can be scaled up to much larger applications such as community heating schemes. Woodchips are loaded into a fuel store or hopper and are fed automatically to the boiler. By using a large hopper, the boiler requires less refilling. It is important to use woodchips of the right moisture content, size and consistency to prevent any problems with operation.
GrainGrain can be a good fuel, since poor quality grain has low selling value, but high energy content, and is easily handled. It produces more ash and clinker than wood pellets, but grain burning stoves have been developed successfully in Denmark. Where a cheap supply of grain is available, a grain burning stove may pay back in only a few years, when compared to the cost of replacing an oil-fired system. For more information see:
StrawBailed straw, and other fuels such as cardboard and waste wood can be burned in some boilers. Straw can provide a very economical and readily available fuel source. Some boilers will burn straw, as well as other clean fuels such as waste wood, grain, and cardboard. For more information see Farm2000
Further InformationFor further information see:
Heat PumpsHeat pumps are an efficient way to heat buildings, and are widely used in Scandinavia. They work by moving heat from one place to another, working on the same principle as a fridge. A heat pump moves heat from a natural heat source, such as the ground, or a well, to the inside of a building. Even at low temperatures, air, ground and water can contain useful heat, and heat pumps are about three times more efficient than electric storage heaters. For every one unit of electrical energy used, three to four units of heat are obtained. A heat pump can also easily be be reversed to provide cooling during summer. Ground source heat pumps require coils to laid under the ground. Water source heat pumps require a pond, well or stream. Further Information
Micro HydroWhere there is access to a suitable river or stream, micro-hydro can be a very attractive option for producing electricity. The term 'micro-hydro' is usually used to describe schemes up to 100kW. Micro-hydro is usually run-of-river, meaning that no significant water storage is required, unlike large hydro schemes which require large reservoirs. In most cases, private schemes generate between a few hundred watts and 25kW. Above this level, schemes are usually commercially operated. Hydro systems at the 25 to 100 kW scale can be connected to the main electricity grid or alternatively can be used in an off-grid system where electricity is either used directly by appliances or is stored through the use of batteries. Single households might be able to go completely 'off-grid' where there is a suitable hydro source nearby. In cases where excess power is generated this can also be sold back into the grid. Many farms in Borders of Scotland are situated on the sites of old mills, and therefore maybe suitable for micro-hydro generation. However, costs are quite high and a pre-feasibility study will be needed to assess the situation. Further Information
Photovoltaic Solar CellsPhotovoltaic (PV) cells produce electricity from sunlight. A PV
cell consists of two or more thin layers of semi-conducting material,
most commonly silicon. The electrical output from a single cell is small, so multiple cells are connected together and encapsulated (usually behind glass) to form a module (sometimes referred to as a "panel"). The PV module is the principal building block of a PV system and any number of modules can be connected together to give the desired scale of electrical output. PV equipment has no moving parts and as a result requires minimal maintenance. They generates electricity without producing emissions of greenhouse or any other gases, and its operation is virtually silent. Summary Photovoltaics (PV) require only daylight – not direct sunlight – to convert solar radiation into electricity. These systems are neat, unobtrusive and can be fitted on flat or sloping roofs or even mounted on the ground. Further Information
Solar heatingSolar panels collect heat energy from the sun that is used to heat water via a heat exchanger. These systems supplement conventional water/central heating systems. There are two main types and configurations for solar hot water systems – flat plate and evacuated tubes. Flat plate systems have an efficiency of around 30% and are a cheaper option to install. Evacuated tube systems generally require a smaller area, and have a higher efficiency, but are more expensive to install.
For areas that are prone to freezing temperatures, there are ‘freeze-tolerant’ systems. This means that collectors can be connected directly into existing hot water cylinders without having to use heat exchangers or anti-freeze. Some systems need pump to move the fluid through the systems, whilst others use natural convection. Systems are available that use photovoltaic energy for the pump rather than mains electricity. Ideally, between 2 and 5 meters square of roof space facing south or southwest is required for installation. The roof space needs to be in little shade for the main part of the day. More informationWindThe UK has about 40% of Europe’s total potential wind energy. However, we only meet 0.5% of our electricity requirements from windpower. Scotland has some of the best sites for windpower in the UK, from a production point of view
Designs for wind turbines vary. They can best be described by output:
Small and medium scale turbines have advantages as they are less intrusive, less expensive, and often well matched to loads. However, they generate less income than large turbines. For medium and large scale operations, community ownership can bring income to the wider community, and avoid disputes and confrontations. A number of community owned windfarms have been very successful Further information |
