Micro wind

Description
A small ground or building-mounted turbine that charge batteries or, more normally for domestic situations, deliver grid-connected mains voltage power via an inverter. Rotors for domestic scale turbines are typically the order 1.75 - 2m in diameter and should be mounted as high as is practical, normally at roof level for building-mounted turbines.

Unit cost of installation
A 1kW generator will cost around £1700 for a basic installation but other costs such as structural surveys and scaffolding etc. may push the total price to ~£3000. Larger systems in the region of 1.5kW to 6kW would cost between £4,000 - £18,000 installed. These costs are inclusive of the turbine, mast, inverters, battery storage (if required) and installation.

Bulk cost of installation
Some manufacturers may offer a discount but each case will need to be negotiated.

Indicative energy cost and carbon emissions

Maintenance
Service checks are required every few years to ensure turbine(s) is working efficiently. Checks should also be made on the mountings and the adjacent masonry to ensure that the unit remains firmly fixed to the building.

Lifetime
There is little definitive data on service life because the technology is relatively new. The expectation is that turbines will last a minimum of 10 years and up to 20 years depending on the local conditions. For example, life expectancy may be shorter in coastal environments. For battery storage systems, typical battery life is around 6-10 years, depending on the type, so batteries may have to be replaced at some point in the system's life.

Technical suitability

In principle any dwelling can benefit from wind energy but not all structures will be suitable for building-mounted turbines. The units are heavy and need to be mounted as high as possible, ideally above ridge height. Large forces will be generated due to wind loading and vibration. The units will therefore require firm fixing. Lightweight or weak backgrounds may not be suitable; advice should be taken from a structural engineer. Older cavity walls may also be suffering corrosion of the wall ties which may make them unsuitable.

Ground-mounted turbines may be more suited to rural environments where there is sufficient space to mount the turbines away from wind shadow from buildings.

It is important that the proposed site will have sufficient wind to generate a useful amount of electricity during the year. The average wind speed for a site can be obtained from the DTI Wind Speed Database at http://www.berr.gov.uk/energy/sources/renewables/explained/wind/windspeed-database/page27708.html - the database can also be accessed via the British Wind Energy Association website (www.bwea.com).

In addition to determining the average wind speed the site assessment should also consider the proximity of trees and other buildings which may shelter the turbine from the prevailing wind. The energy generated is calculated using the method that can be found on the GreenSpec website http://www.greenspec.co.uk/html/energy/windturbines.html) with the wind speed as calculated using the standard that has been developed for the Microgeneration Certification Scheme. This guidance can be found in document MIS3003 (Appendix B) and can be accessed via the website www.ukmicrogeneration.org.

Non-technical constraints
Installation of wind turbines may require planning permission and local consultation with relevant stakeholders, such as neighbours. It is necessary to consider environmental considerations, access to site, noise and visual effect. National planning polices support the development of small scale wind energy.

Potential concerns with fuel poor
No specific issues.

Trigger points for work
Repairs to roof.

Performance Limitations

Technical Guidance Available
» CADDET Renewable Energy - 01235 436806: www.caddet-re.org
» British Wind Energy Association - 020 7679 1960: www.bwea.com