What are the main benefits of small scale wind power?

Environmental and Financial Benefits

A domestic or small business wind system should be viewed as a long-term environmentally beneficial investment, as it may be number of years into its life cycle before it gives payback in financial terms. The value of electricity produced will depend on the corresponding cost of mains electricity during the life of the turbine. While prices for electricity are currently decreasing, the cost of electricity to the consumer has risen substantially in the previous 5 years (by over 50%). While the price of oil has now fallen sharply, from its record highs during the summer of 2008, there are no guarantees about future prices. The price of electricity in Ireland is heavily dependent on the price of fossil fuels (more than 80% of electricity generated in 2007 was fossil fuel sourced) and it is expected that the long term trends in fuel prices will continue upward.

Why does the price of oil matter to an electricity customer? Because the cost of other fuels, such as natural gas, tracks the price of oil and as a result so too does the price of electricity in Ireland. In 2007, nearly 60% of our electricity was generated by burning natural gas. So a wind turbine can provide some stability to a portion of electricity costs and is likely to become more competitive if electricity prices increase again or if there is a carbon tax introduced which is applied to mains electricity.

Many users of small scale wind turbines are not motivated solely by financial concerns. Many are attracted by having an independent, local source for a portion of their energy needs. Others are concerned with the environmental impact of conventional electricity generation. Conventional thermal power generation inefficiently consumes valuable finite resources- for good. Other than carbon dioxide, by-products of the generation process, depending on the fuel used and mitigating measures employed, can include acid rain causing compounds, irritant particulate emissions, mercury emissions and ash. Wind generated electricity displaces energy from the grid when it is consumed on-site. Power generation is one of the biggest sources of greenhouse gas emissions in Ireland.

In 2007 Ireland produced more than 80% of its electricity by consuming fossil fuel resources, (gas 55%, oil 6%, CHP 4% and coal 18%) the vast majority of which had to be imported. On average in 2007, each unit (kWh) of grid electricity consumed had an associated carbon dioxide production of approximately 538g. The associated carbon production varies depending on the time of day and the suite of generation plant which is brought onto the system by the system operator. But in simplistic terms, for every 2 units of electricity produced by the domestic wind turbine over 1 kg of CO2 emissions could be avoided.

There are of course emissions associated with the manufacture, transportation and erection of a wind turbine but a correctly sited quality unit will be able to repay these in a reasonable time. Equally an ill-suited, badly sited, poor quality turbine may never produce the energy which has gone into its production, not to mention paying back in economical terms. For instance roof mounted turbines in built up areas can prove to be purely ornamental rather than productive or beneficial to the environment or the owner. They can in fact increase energy consumption as the occupant is misguided into thinking they are producing electricity at a rate which allows them to increase their own consumption without impact on the environment or on their bill.

A portion of the electricity produced by power stations is lost during transmission and distribution over long distances. The losses occur in transformers and in the wires. Energy generated closer to where it is consumed will reduce the total energy losses on the system.

Wind turbines are often the most cost effective energy option in remote off-grid areas where it may be very expensive to connect to the grid. Battery storage can be added to the off-grid system so that power may be available on demand.

Energy Security

Replacing electricity produced from imported fossil fuels with wind energy generated on site at your home or business could make a significant contribution to Ireland's energy security and reduce the carbon intensity of Ireland's electricity needs. As an island with very limited fossil fuel resources, Ireland is heavily dependent on imported energy supplies. Ireland currently imports over 90% of its consumed energy including petroleum products, coal and natural gas. While an individual installation will not improve security of energy supply or reduce emissions on a national level, the cumulative effect of a large number of installations will be positive.

Ireland has access to huge inexhaustible energy resources, such as wind, which happen to be renewable and clean. Wave energy devices are still in development and are expected to be useful only for commercial electricity production on a larger scale. Wind power is a mature technology and can be harnessed by the individual for personal or business use.

Following unprecedented prices for oil during 2008 the price has dropped significantly in the first quarter of 2009. OPEC have indicated that $70 to $80 may be a more realistic medium term price for production from ever more challenging reserves to be viable. The long term trend in oil prices is expected to continue upward. It is worth remembering that throughout the 1990's the price of a barrel of oil hovered around $20 and as recent as 2005 $70 was seen as a threat to fossil fuel dependent economies all over the world. Now that the price has returned to a seemingly low price in comparison with the record prices seen during 2008 we may have been desensitised to high prices. This should not discourage us from looking for energy supplies which are local, sustainable and not affected by global events far removed, geographically and politically, from Ireland.

Education and Awareness

The installation of a turbine or other renewable technology can be a focus for educational purposes and increase awareness of energy efficiency in a school and in student's homes. Many schools are involved in An Taisce's green schools initiative which includes energy as one of the main themes. As with any installation the load profile will need to be considered. Schools may have an unusual load profile due to the hours they are open during the day and due to the fact that they may be closed for longer than they are occupied i.e. evenings, weekends and during holidays. A thorough feasibility study by a competent supplier should examine the implications of each customer's demand profile and the payment available for exports.

The addition of microgeneration to a home can increase energy awareness and make an already efficient home even more so as the occupants modify their consumption behaviour as much as possible to minimise imports and consumption to maximise exports where payment is available.

'Green marketing'

A firm may wish to demonstrate to customers that they are aware of environmental issues and the environmental impact of the energy consumption of their business. An appropriately sited, well maintained and fully operational wind turbine is probably the most visible means by which this commitment can be demonstrated. As consumers become increasingly aware of environmental issues companies which are proactive in minimising the impact of their business on the environment may have the edge in a competitive marketplace.

Employment

Local jobs are supported by the microgeneration sector. As the industry grows from a small base it is hoped that more jobs will be created in site assessment, installation and maintenance. A number of Irish companies are also in advanced stages of developing of their own turbines which will be manufactured in Ireland.

SEAI will be over-seeing a comprehensive field study throughout 2009 and into 2010. Following this study we will be in a better position to detail the benefits of the technology to the domestic and small commercial user. The benefits of large scale wind are widely known.

The goals of the study include:

• Monitor and assess turbine and equipment technical performance in Ireland;
• Assess the reliability of a range of technologies and manufacturers;
• Assess economic performance in the context of the Irish market;
• Inform the design of intelligent tariffs for smart metering; and
• Develop best practice guidelines for installers and suppliers.

What will a site assessor look for during an assessment?

Altitude

As distance above sea level increases the speed and the power of the wind also increases. Although affected by local conditions a general rule is that the higher the site is above sea level the more likely it is to have a good wind resource. Altitudes of 200m or more above sea level are most desirable. Furthermore the higher the site is above the immediate surrounding area the better the wind exposure is likely to be at that location.

Aspect

In Ireland the prevailing winds arrive from a south westerly direction. If there are obstructions in this direction the productivity of the turbine will be reduced. The obstructions, depending on their nature, will either slow down or cause turbulence in the air flow. If a large proportion of the wind during a year is coming from this direction it is clear that the turbine will not be exposed to ideal conditions. If there are similar obstructions in other directions (other than the prevailing wind direction) they would not have as great an impact on the output of the turbine. However it is preferable to have no obstructions close to the turbine in any direction.

The prevailing wind is categorised as a global wind. There may be conditions which create local winds such as sea/land breezes and mountain winds, which may be as important as the prevailing wind in terms of turbine output. Local winds are created by temperature differences between sea and land or highlands and lowlands at different times of the day and night.

Obstructions

It should be clear that the more exposed a site is to the wind the cleaner the air flow over the blades and the more productive the turbine will be. The turbine will also demand less maintenance if the air flow is less turbulent. The least desirable location for obstructions is close to the turbine in the direction of the prevailing wind.

Obstructions can be individual trees, houses, out-buildings, ditches, forests, or hills. It should of course be remembered that trees grow so obstructions can develop over time after the turbine is installed.

Obstructions affect the airflow in a number of ways. Firstly the airflow is disturbed leading up to the obstruction. This disturbed flow zone stretches outwards for twice the height of the obstruction before the obstruction. Imagine water flowing in a river and hitting a rock. The water is backed up and disturbed before it even hits the rock as the fluid (air is a fluid too) moves against, up and around or over the obstruction. For this reason it is undesirable to have a turbine within twice the height of an obstruction in any direction.

Downwind from an obstruction the zone of disturbed airflow stretches outward for up to 20 times the height of the obstruction before the wake settles.
The industry norm is to try to site the turbine at least 10m above any obstruction within 100m. However achieving this is quite difficult in reality.
Obstructions not only create disturbed flow before and after their position but also above. The disturbed airflow hits the obstruction and part of it is thrown up and over. This area of disturbed flow can stretch upwards to twice the height of the obstruction. One of the key reasons why roof mounted turbines perform poorly.

It is worth noting that when they are assessing a possible site for a wind farm, developers consider all obstructions and land use within 100's of metres of a development, even though they might be installing turbines with hub heights of 80m. Micro-scale turbines might only be 10m above ground level.

Space

The more space there is in a site the more options there are for constructing the turbine tower away from obstructions. Planning regulations state the distances the turbines must be from party boundaries and the noise levels allowable at premises. One of the requirements for a turbine in a domestic setting to be exempt from planning requirements is that it must be the total height of the turbine (uppermost point of blade tip) plus 1m from a boundary.

In order for a commercial application to be eligible for exemptions from planning requirements the turbine must be its total height plus 5m from the nearest party boundary.

In an agricultural setting the regulation states that the distance required is one and a half times the total height of the turbine plus 1m.

So a turbine which is 13m in total height must be 14m from the boundary in a domestic setting, 18m from the boundary in a commercial or industrial setting and 20.5m from a boundary in an agricultural application. You should contact your local authority to ensure that the exemptions apply in your situation.

Ample space is also required for the tower structure depending on the type recommended or supplied by the manufacturer. Guyed poles require a large area to accommodate the anchor points for the guy wires. Lattice towers and tubular steel poles can require considerable space in two directions in order to be hoisted up or tilted down either by a winch or crane. Guyed tower wires need to be protected from larger livestock and so may require a parcel of land which should be put to other safe use if currently used for grazing. Once free standing lattice towers or tubular steel towers are erected the land immediately around it can be used safely as normal.

During the site assessment it may be discovered by a competent trained assessor that the options for siting the wind turbine are limited by planning exemptions, safety considerations, obstructions and cost of cabling back to the premises. So a substantial parcel of land might just provide one or two small viable areas for construction.

Vegetation

Trees, shrubs and ditches can have an effect on small scale wind turbines. A field which one year is used for grazing, and so has short grass, and the next year grows maize, and so has tall planting, will affect airflow to varying degrees.

Vegetation can be used during a site assessment to point the direction of the prevailing winds as branches and even whole trees can be permanently deformed by the wind as it prevails in one direction. It is easier to see this effect during the winter when the leaves reveal the deformed limbs and branches.

Proximity to dwellings, neighbours, power lines, airports and other wind turbines

Careful consideration must be given to the location of the turbine for safety and planning reasons. The planning requirements outline the limitations with regard distances from dwellings, noise levels, siting near airports and power lines.

A balance must be found between siting the turbine as far away as possible from the house and minimising cabling costs and line losses in connecting to the house. The site assessment should encapsulate all of these considerations when choosing an optimal turbine location.

While the site might appear to have ample space for a turbine it may be discovered following the application of the various planning requirements that only a small area of the space remains eligible for an exemption from planning within reasonable distance from the property.

Demand profile

The assessment should also consider the dwelling or premises' consumption and the nature and timing of that consumption. Over-sizing a turbine may mean payback is affected in the long term and under-sizing a turbine may mean an opportunity is missed to maximize the potential of the site for reducing the customer's bill. Under-sizing a unit is preferable to over-sizing an installation however as it prevents an inefficient system being installed.

The installation should be looking to meet a steady demand for electricity throughout the day and night rather than peak demand for small periods. Ideally the site will have demand throughout the day and night so that the power generated has a use on-site, especially if it is not possible to avail of an export tariff equal to or greater than the import tariff. While 19c/kWh is currently available to ESB Customer Supply customers it is only for the first 3,000kWh exported per annum. The export value falls to 9c/kWh thereafter.

Refrigeration systems, heat pumps, existing storage heating, heat lamps and other appliances which require demand throughout the day and night improve the viability of the site with regard microgeneration. The demand should also be throughout the year and not just seasonal. Some sites may have demand for cooling in the summer and heating in the winter.

In their guided tour, www.windpower.org has free online tools which a site assessor or customer can use to try and put some numbers on the effect of various characteristics of the site.

What permissions do I need before erecting or connecting a turbine?

Planning permission is required if the characteristics of the system to be installed are outside those described in Statutory Instrument No. 83 of 2007 or Statutory Instrument No. 235 of 2008. You should contact your local authority to ensure that the exemptions apply at your location and you are not subject to the restrictions on exemptions as outlined in SI No. 600 of 2001. (Refer also to the FAQ covering planning requirements).

ESB Networks operate an 'inform and consent' system of registering a grid connected system. The interface with the grid must be of a type compliant with EN 50438. ESB Networks maintains a list of 'type tests' for grid interfaces or inverters which comply with European standard EN50438.

The conditions governing the connection of a microgenerator, including the important points of EN 50438, can be viewed on the ESB Networks website.
The standard ensures quality of output if exporting or connected to the grid. The turbine must stop producing in times of grid outage. While it would be useful to have your own source of power during a network outage the automatic shutdown of a grid connected turbine is necessary to minimise the risk of injury to line technicians repairing or working on a line.

The Commission for Energy Regulation directed that individuals planning installations below 1 MW in capacity (includes all microgenerators) will no longer be required to apply for an Authorisation to Construct or a Licence to Generate. Each installation will stand duly authorised by order. All generators must comply with the requirements of the orders so it is each generator's interest to review the conditions of the authorisation and licence.

Can I put a small turbine on my roof or on a pole fixed to the building?

Current planning regulations state that roof or building mounted turbines are not exempt from the planning requirements. Therefore an application to your local authority through the normal planning mechanisms is required. Only mast mounted turbines of a certain size may be exempt from planning requirements under certain conditions.

Building mounted turbines have a history of poor performance. The building itself affects the flow of air around it. Even if the turbine is fitted in a position well above the uppermost part of the pitch or flat of the roof the airflow is still negatively impacted. Thus the output from the turbine is often very low and the return on the investment non-existent.

The ideal air flow over the blades of a turbine is smooth, constant and unidirectional over a period. In aerodynamics this kind of air flow is known as laminar flow. When air flow meets an obstruction currents, or 'eddies', are induced, creating turbulent flow. Visualise the wake caused by a rock in a fast flowing river or rapids.

Turbulent flow is not only undesirable for efficient electricity generation it is also undesirable from a mechanical point of view. The turbulent flow causes the turbine to yaw excessively in an attempt to always face into the wind. This excessive yawing causes cycling forces and premature wear on the unit and may significantly reduce its life span and increase maintenance costs.

If you choose to go ahead and apply for planning permission to mount a turbine on an inhabited building it should be remembered that there will be some vibration and noise transmitted into and through the fabric of the building. The transmitted vibrations and noise may not be fully counteracted by damping or sound proofing of the mounting. For that reason if you are choosing to mount a turbine on a structure it is advisable to seek planning to mount it on an adjacent non-inhabited building or solid separate structure.