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Section 6: Technologies
Introduction
The range of renewable heat technologies available for use today is extremely diverse. The principal technologies considered are:
- Biomass combustion (burning biological material)
- Heat pumps (using a small amount of energy to extract a larger amount of energy from the air, water or the earth)
- Solar heating (using energy from the sun to heat water or air)
- Geothermal aquifers (using heat pumps to extract energy from waters deep underground, for example, disused mine workings)
- Renewable energy from waste (a subset of biomass; using biomass which would otherwise be discarded. The technology options here include anaerobic digestion, gasification and standard open kiln incineration)
- Anaerobic digestion (producing combustible methane gas from biomass for direct combustion or the option to use fuel cells)
- Landfill gas (harvesting the methane gas produced by natural biomass decomposition in landfill sites)
- Wind-to-heat (using devices to turn wind energy to heat, e.g. via mechanical forces and friction or electricity)
Some of the key factors which differentiate these technologies are:
Descriptor | Fuel | Fuel Capture | Fuel Process | Output Energy |
|---|
Biomass Combustion | Biomass | Harvest Crop | Combustion of gas or solid phase fuel. Gas conversion in fuel cells | Heat or Heat and/or electricity |
|---|
Renewable Energy from Waste | Waste (EfW) biomass | Municipal/ Commercial/Industrial Procedure |
|---|
Anaerobic Digestion | Biomass | Biological | Gas combustion or fuel cells | Heat and/or electricity |
|---|
Air Source Heat Pump | Heat in Air | Heat Exchange to Water/Coolant | Heat Pump | Heat |
|---|
Ground Source Heat Pump | Heat in Ground |
|---|
Water Source Heat Pump | Heat in Water |
|---|
Solar Thermal | Solar Heat | n/a | Heat |
|---|
Wind to Heat | Wind | Wind Turbine | Generator | Heat and/or electricity |
|---|
Applications
Some technology types may be suitable for domestic, commercial and industrial uses at a range of scales from individual homes or facilities to whole towns, industrial estates or districts. Others may have more restricted applications. The table above shows some of the factors influencing which technology may suit particular applications. For example, anaerobic digestion and landfill can produce relatively large amounts of biogas, but the equipment which is readily available requires considerable space and regular maintenance, limiting its suitability. In contrast, heat pump technologies are unable to supply the high temperature heat required for combined heat and power or district heating systems and are more suited to residential applications.
Whereas a detailed analysis of the various technologies and the roles each can play is beyond the scope of this report, the group sees value in developing an information pack for members of the public.
Barriers
The barriers to the deployment of individual technologies vary, but can be categorised broadly as follows:
Lack of trained installers and maintenance personnel | Installers may only have a good technical understanding of specific models. They may also lack experience in the range of interactions with the building envelope which can be crucial. |
Consumer confidence | Consumer confidence could easily be eroded through media coverage of bad examples - e.g. exaggerated claims for performance, poor quality installation work, damage to building fabric or injuries sustained. |
High up-front capital costs | Renewable heating technologies may have considerably higher capital costs than comparable fossil-fuel equipment with a well established market - e.g. gas. |
Maintenance charges | To sustain good performance, some technologies may require regular maintenance that end users are unable or unwilling to carry out - e.g. cleaning flues, lubricating automated fuel supply systems etc. |
Consumer time required | Consumers can quickly and easily locate information and advice on fossil fuel technology - e.g. go to a gas showroom. Renewable technologies are less familiar and consumers may have to spend more time tracking down additional information. |
Availability of fuel | Some technologies are constrained by the availability of fuel. For example, landfill gas needs a landfill site. Local woodfuel supply chains may not exist in some areas. |
Procurement | Procurement processes may be closely focused on direct capital costs with less consideration given to the wider social and environmental costs of carbon emissions from "cheap" fossil fuels such as coal or gas. Investor confidence on the reliability of technologies and stability of fuel supply chains in the longer term can also be an issue. |
Section 8 examines the various mechanisms that can address these barriers.
Technologies
That Scottish Renewables:
- Produces a consumer information pack outlining what the key renewable heat technologies are as well as explaining the important factors to bear in mind when considering which may be appropriate for specific applications.
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