Technologies - Wind Turbines

Building integrated wind turbines is a developing market and is providing opportunity for on-site generation to meet demands. Although the urban environment gives rise to a more turbulent and reduced wind flow, turbines are being designed to maximise their potential in these conditions. Building location and size can be utilised to make use of the higher wind speeds above street level; and in addtion the building itself can be designed to augment the wind speed. Since the highest wind resource will often occur in winter months,wind power can be used as complementary generating source for a solar power system. This design opportunity is being exploited by a number of companies.

Wind is an intermittent source of energy, and it is difficult to meet the entire electrical demand of a building such as a hotel, from the total output of the turbines. Hotels in general consume significant amounts of energy and resources. If substantial amounts of power are required, a very large number of wind turbines must be used to generate adequate amounts of power. This is very difficult in an urban environment as the roof area per head is likely to be low.

Examples of wind turbines that can be used in an urban environment are shown below:

At the moment, urban grid connected small scale wind systems do not pose any major problems to the distribution network, as numbers are too small to have a damaging effect. As this technology develops though, and the number of small scale wind turbine installations increases, potential grid connection issues may arise. In the future, as micro-generation, not just small wind, expands, there may need to be changes to the networks to resolve these technical issues; but this next step is still many years away.

Is small scale wind power generation for my hotel?(See our tool to realise if it is feasible)

1. Calculate the total power output by taking into account the below parameters, and see if wind turbines can meet any of your electrical demands.

A= Sweep area of rotor (m2); V= Wind velocity (m/s); CP= Power coefficient (~0.4 in an uban environment); Pi: 3.14;R= Rotor radius (m)

Wind is an unpredictable resource on a day to day basis. The traditional method of calculating an accurate average daily velocity is done using the Weibull Probability Density Distribution.

2. Work out the potential energy and cost savings.
Economic assessment must be carried out separately for each site.
Total installation cost*: 1. Total capital investment: wind turbine, distribution network, 2. Annual wind turbine maintenance cost. Savings will be reflected in the utility bill for electricity.

The average cost of systems is ~£4200/kW, but this varies greatly depending on site factors. The underlying economic driver for determining the feasibility of a wind turbine installation is of course the wind speed at the site. In other cases cable can account for up to half of the installation cost, especially where concrete needs to be excavated at up to £90 per metre.

Manufacturers of small wind turbines (~2.5kW) often recommend an annual maintenance service. This may cost £200+ and will therefore cancel out much of the revenue gained in electricity savings from this type of turbine. However the reliability of a wind turbine is estimated to last up to 20 years.

A Renewable Obligation Certificate (ROC) is issued to accredited generators for every MWh of electricity produced from renewable sources. ROC’s can be freely traded and have a current market value of approximately £46/MWh. For small generators of electricity (<50kW) claims for ROC’s can be made on a yearly basis, whereas for larger generators claims can be made monthly. This makes it infinitely more possible for smaller systems to achieve a generated target of 1MWh; but unfortunately the administration, paperwork and technical knowledge required in gaining the status of an accredited generator is often too arduous for domestic community groups and small organisations to justify completing.

Approximately a quarter of small wind turbine installations are currently claiming the available ROC’s. For ROC’s to be claimed where generators use some of their own electricity (which is the case in most of the UK Small Scale Embedded Generators or SSEG’s) the generator must also have a buy-and-sell back contract with a supplier. This adds further complications to metering procedures and finding the appropriate contract. Existing companies which collect ROC’s and tariffs on your behalf, such as Good Energy, will give you ~4.5p/kWh produced, and then claim the ROC’s for your generation.

Due to the complications of claiming ROC’s, the SSEG industry has not benefited greatly from this incentive. If it were made easier to claim ROC’s for small scale generators, the associated economic benefits would provide the stimulus that the micro-generation market needs.

The Scottish Community Household Renewable's Initiative provides grants for properties in Scotland. For more informaton on the grants available, follow this link: www.energysavingtrust.org.uk