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What is the financial payback period for such an investment?

Under current circumstances economic payback for a micro-scale wind turbine - a long term investment - may not be achieved for more than ten years. The

• Capital outlay
• Demand for electricity and the timing of the demand
• Load factor
• Maintenance costs
• Average wind speeds
• Turbine performance
• Cost of alternative sources of power
• Life-time of the turbine and associated equipment
• Value placed by prospective buyer on Building Energy Rating
• Payment or credit for excess electricity exported.

Capital Outlay

Quality turbines of any scale are not cheap. A good quality 5kW - 6kW turbine can cost over €25,000 to purchase, install and connect. A well maintained good quality 6kW unit in an excellent site will produce around 13,000 units of electricity per annum. Depending on the proportion of this power which is consumed onsite, exported for 9-19c/kWh or exported for free it has a value from anywhere between €1300 and €2400 to a domestic customer of ESB Customer Supply.

13,000 kWh would have the value of around €2400 if all of the units produced were consumed onsite and the site was supplied by ESB CS with the 24-hour rate (rather than the night-saver). However a typical house in Ireland might consume around 5,500 units of electricity per annum and not 13,000. The electricity generated would have the value of €1760 if the turbine matched demand for 3,000 kWh of a typical houses demand (at 18.6c/kWh per unit) and exported the balance (3,000 kWh at 19c/kWh and 7,000 kWh at 9c/kWh). The house would then still have to import 2,500 kWh at 18.6c/kWh (or €465 worth of electricity).

Demand for power and the timing of demand

Clearly the proportion of power consumed/exported/imported can vary widely from premises to premises. Customers could monitor their own energy use for a period of months to get an idea of the timing of their demand. A variety of DIY energy monitors are available and the data collected can be uploaded to a computer for analysis.

Well sited consumers who remain high demand customers after employing all appropriate energy efficiency measures may be best placed to benefit most from the addition of microgeneration. Wind microgeneration is suitable to sites where there is a constant 'base-load' demand for electricity. That is where demand rarely drops below a certain level, even at 5 a.m. If a turbine is installed it can displace imported power required to meet the base-load demand. It should however be remembered that 'night-saver' or other economy tariffs are available and these should be included as appropriate when analysing the economics of the site.

Load factor

Every demand customer has a 'load factor. In electrical terms a load factor can be expressed as the ratio of the maximum electrical demand versus the average demand over the same period (peak v. average). A rugby club with floodlights may have a very small demand for 95% of the week. For a few hours every week during 6 months of the year the demand reaches its peak when floodlights are turned on for training. Installing a wind turbine on a site such as this is far from ideal from a demand and cost reduction point of view unless an appropriate export tariff can be availed of.

Maintenance costs

Maintenance costs and contracts should be discussed with a number of prospective suppliers. A routine maintenance schedule should be supplied by the manufacturer as well as estimates for future costs of major parts. The schedule should be sufficient to ensure long and productive operation under local conditions. Some turbines require more maintenance than the manufacturer recommends while others may survive with less. As is the case with all machinery, the more frequent the maintenance and care the longer the turbine is likely to be of use. The ultimate aim is to reach beyond the break-even point. A turbine system which does not reach a break-even point has in effect produced power during its lifetime that has been more expensive than would have otherwise been available from the grid.

Maintenance costs usually include a call out charge as well as costs to cover access to the turbine for greasing and other light maintenance. After a period of years parts such as blades or brushes may need to be replaced. Estimates for the lifespan of such parts and the cost of such non-routine maintenance should be provided by the supplier or manufacturer. Again local conditions, turbulent air flow or storm damage may require replacement of parts outside of any schedule.

The more mechanically and electronically complex the turbine is the more elements there are that can go wrong, therefore the more maintenance which may be required. Simplicity should be a factor in choosing a turbine.

Average wind speeds

The output of a wind turbine is dependent on the energy in the air flowing over the blades and through their swept area. Power output for a given turbine is proportional to the cube of the wind speed i.e. if the wind speed doubles the power output increases by a factor of 8. Another way to look at it is that a doubling of the power output can be achieved by an increase in the wind speed of just 25%. So it is clear that the power output and its value can vary substantially from site to site. Average wind speeds are more important than the occasional high wind speeds which might be available at a site.

Turbine performance

Manufacturers and suppliers should supply all of the technical specifications and expected performance figures for the turbine and system. Each turbine has a power curve which will give an indication of the turbines output at different wind speeds. A power curve which an accredited third party test or independent test facility has developed is more reliable than a manufacturer supplied one. Customers should always check the accreditation of test facilities providing certification. A power curve will show information such as cut-in wind speed, peak power, rated power, rated wind speed and cut-out wind speed.
A low cut-in wind speed is desirable to capture as much available energy as possible. At cut-in the turbine will produce little power but it is better to be producing something rather than nothing. Before cut-in turbines may be rotating but the generator is not producing any power. A typical cut-in wind speed for small turbines is 3m/s.

Peak power is the maximum the turbine will produce in infrequent circumstances such as exceptionally high winds or momentary gusts. Over-speed controls should prevent too much power being conducted through the electronics but peak power could cause damage if the turbine is not designed or prepared to respond quickly or if the mechanism fails. The electronic controller and inverter are designed to cope with currents and voltages within a range and a momentary breach of upper limits will damage or burn out components, if not the entire unit. The inverter must be sized appropriately to cope with peak power production.

The key performance indicator for a wind turbine is the amount of energy it produces over its lifetime and not the rated power/nameplate rating.

Cost of alternative sources of power

The power produced will replace imported electricity at the retail rate available at the moment it is produced. At present domestic customers generally have access to just two types of tariffs. One account has a flat tariff throughout the day and night. The other option is a day/night tariff with the meter differentiating between units consumed at night and during the day (ESB's 'Nightsaver' product for example). The day-time tariff in the day/night option is slightly more (6.8% more) than the standard 24 hour tariff but the night-time tariff is significantly less (47% less). The day/night tariff option is suited to homes with electrical storage heating.

Commercial and residential commercial customers have a range of tariff suites available from a choice of suppliers. Anyone, commercial or domestic customers, considering their tariff options need to consider carefully their consumption patterns and factor in extra standing charges applicable for the required metering. There is also a charge for the required meter.

Some microgeneration sites may chose to use the power produced onsite to heat water, be it for washing or for space heating -direct water heating. In this case the fuel cost comparison is carried out against available heat fuel sources such as oil, natural gas and biomass boilers or stoves. For situations where just the excess electricity is used to heat water it is just that portion which is compared to other heat sources with the remainder compared to electricity imports as before.

Life-time of the turbine and associated equipment

By definition a turbine that lasts beyond its break even point or payback period has paid for itself. It is also clear that a turbine that only lasts a small few years is a wasted investment. Turbines need maintenance and it is in the interest of the owner to keep the turbine generating for as long and as efficiently as possible to get to a point where the turbine has paid for itself and it is producing clean energy at a cost less than the retail price of electricity.

Value placed by prospective buyer on Building Energy Rating

Adding microgeneration to a property will improve its rating under the Building Energy Rating (BER) requirements. The output from electricity producing photo-voltaic (PV) panels will be estimated as per a prescribed formula. For wind turbines there must be at least one year's output data before it can be factored into the buildings performance. This is to account for a wide variation in performance of turbines- from good sites to poor sites and from maintained turbines to defective ones.

Prospective buyers, leasers of a premises or tenants will place a value on the energy rating of a building. Running costs can be a key consideration when valuing, purchasing or renting a new property.

Payment or credit for excess electricity

Payment by electricity suppliers willing to buy excess electricity will reduce the payback period and improve the viability of the technology. With a payment of between 9c and 19c/kWh being offered by some of the ESB Group every unit of electricity produced has a value and units will no longer be exported to the grid for free.

To give a simplified example: A house in an excellent site for availing of wind has a 3kW turbine installed. The turbine produces around 6,300 units of electricity (kWh). The house has an annual demand of 5,000 kWh but the turbine only matches this demand for 40% of the time i.e. 2,000 kWh of the house demand comes from the turbine. The remaining 3,000 kWh comes from the grid.

If no export tariff was available the turbine output would have the value of €372 (retail price of electricity (e.g. 18.6c) x 2,000) as the amount exported (4,300 kWh) would have no value. With payment for export available to domestic customers each of the 4,300 units now has a value. The first 3,000 kWh has a value of 19c/kWh (equal to €570) and the remaining 1,300 kWh has a value of 9c/kWh (equal to €117). Thus the payback period is reduced by earning €687 from exports annually. This export payment is on top of the payback accruing from displaced imports (the 2,000 kWh mentioned above).

How long should the turbine last and how much maintenance is required?

Once installed, the source of the power produced is free. However, it should be remembered that the turbine is not free and the actual unit cost of the electricity produced is equal to the total costs of the turbine over its life-time divided by the amount of useful units it supplies (neglecting any payment for export to the grid).

Clearly it is important to keep a turbine running for as long and as well as possible if the financial and environmental benefits are to be accrued. Maintenance costs are an important factor to remember. In principle, the best quality turbines have a working life of up to 20 years but their actual life expectancy depends very much on design, materials, the quality of the installation and maintenance as well as local wind and atmospheric conditions (e.g. coastal air, turbulence). Poor quality turbines may be destroyed in the first high gust of wind or after 2 - 3 winter storms. Equally, a good quality turbine which is poorly or incorrectly installed could be destroyed or damaged within a short period.

A supplier may offer a maintenance agreement or contract for a set period after the installation. Alternatively they may give an indication of what they might charge for a call out or regular service. Some turbines may not need to be serviced until a number of years (2-3) have passed since the installation. Manufacturer's guidelines should clearly state the maintenance schedule which will be in compliance with a warranty. Routine maintenance may simply be a case of greasing wearing surfaces and checking fasteners. Major maintenance may be required less frequently, for example a blade may need to be replaced after a number of years.

Because wind turbines are erected during the weather and wind conditions existing on the day they may need some fine tuning in the days or weeks following. For obvious safety reasons a turbine may be erected during a period of no wind and the installer or electrician may have to return to commission the system on a windy day to ensure everything is operating as designed. Furthermore some teething problems may be experienced in the weeks after commissioning. You need to be sure that you have chosen an installer that will respond to your requests for a site visit under these circumstances. Getting the view of existing customers is one way of gauging a supplier's customer service.

What should I expect of a turbine supplier/installer?

A comprehensive site assessment during a site visit by a competent, trained representative is a basic necessity. Buying a turbine in a DIY store or online, regardless of site suitability, could turn out to be a mistake. The key elements of a site assessment are covered elsewhere in these FAQs.

Feasibility study

The site assessment will feed into a report which will indicate if the site is technically and economically viable. If the site is not economically viable or is borderline the customer may wish to go ahead to capture other benefits such as clean and independent energy. Site demand and the timing of that demand will be crucial to the viability of the site. More detailed information on site assessment and viability is available elsewhere in these FAQs.

Certification

At present the key applicable standard associated with microgeneration in Ireland is EN 50438. This standard's scope is limited to the point at which the turbine connects to the grid. Therefore the standard applies to the inverter. ESB Networks must be furnished with evidence of compliance with EN 50438 for the grid connection to be approved. ESB Networks' main concerns are that the turbine will not export power to a de-energised grid and that the power produced under normal operation will not reduce the quality of the supply to other customers in the area. A de-energised grid, during a power outage (planned or otherwise), will be worked on by technicians. If the inverter allows electricity to be exported to the grid at this time it is a danger to the technicians.

The turbine itself should be certified to perform in accordance with EN 61400-12 and designed safely to be compliant with EN 61400-2. EN 61400-2 includes the classification of small wind turbines with regard the wind speeds and conditions for which the turbine is designed. Class I winds are common in Ireland and many turbines are not designed to withstand the high gusts or average wind speeds experienced in our climate.

Class	I	I	II	II	III	III	IV	IV
	m/s	mph	m/s	mph	m/s	mph	m/s	mph
Vref	50	112	42.5	95	37.5	84	30	67
Vave	10	22	8.5	19	7.5	17	6	13

Table 3 shows the classification of small wind turbines as prescribed in EN 61400-2. V_ref is the reference wind speed for each turbine. A turbine designed with a V_ref of 112 mph is designed to withstand climates for which the extreme 10 minute average wind speed with a recurrence period of 50 years at the turbine hub height is lower than or equal to 112 mph. V_ave is the annual average wind speed at hub height.

The performance of the turbine in relation to noise should be in line with EN 61400-11. These are international standards. A manufacturer can self-declare compliance with the safety standard EN 61400-2. Proof of compliance with EN 61400-12 and EN 61400-11 is achieved by putting the turbine through rigorous tests. The test must be carried out by an accredited test facility and not the manufacturer or a non-accredited facility. Customers should check the accreditation of the test facilities appearing on the test reports because they may not be as professional as the document may portray.

The CE mark should also be in evidence on the major elements of the microgeneration system (turbine, inverter and controller). The CE mark is not a symbol of quality but does show that certain standards have been satisfied by the manufacturer.

Training

Action Renewables in Northern Ireland has developed a training course for wind and hydro micro-turbines and PV panel installers. At present there is no legal requirement for installers to have undergone this training in order to operate in the Republic of Ireland. There will be a compulsory training requirement in place for any equipment and installer registration in the future- similar to current arrangements for wood pellet boilers and solar thermal panels. The training is run by the Renewable Energy Installers Academy (REIA) in Northern Ireland and it is open to electricians from the republic. The awarding body is City & Guilds.

Some of the established turbine manufacturers offer training courses for installers of their equipment. In an effort to protect their brand some manufacturers will only supply turbines to installers who have undergone this training. A combination of the training provided by the REIA and the practical training provided by a quality turbine manufacturer should equip a supplier well to provide a good service to its clients.

A number of private training providers are offering wind turbine training courses in the Republic but many of these are not recognised by City & Guilds, FETAC or the SEAI field trials at present. For a list of recognized training sites please refer to the list on the SEAI website: Microgeneration Training Providers. SEAI is developing training and certification requirements with a view to having a FETAC qualification in place as soon as possible. For the purposes of eligibility for the small scale field trials the REIA training and manufacturer training will be required. Prospective customers should aim for this standard when choosing a supplier or installer whether they intend to apply for inclusion in the trials or not.

The final wiring and sign-off of a grid connected turbine must be completed to ETCI standards. The electrician should be a member of a certified trade body such as RECI and ECSSA. Ask your prospective supplier for evidence of training or experience within the company.

Health and Safety

The Safety, Health and Welfare at Work (Construction) Regulations 2006 prescribe the duties and responsibilities of all parties (client and provider) engaged in construction activities with regard health and safety. One of the main duties of a client is the appointment of project supervisors for the design and construction stages of a construction project (PSDS and PSCS). Domestic works are exempt from this requirement unless a trade or business is undertaken on the premises. Turbine suppliers and installers should provide an undertaking that the works will be carried out in line with the requirements of the 2006 regulations. Clients should make themselves familiar with their duties under the regulations.

Warranty

Some manufacturers and suppliers offer warranties with major equipment and parts. Ask a selection of suppliers what warranty they offer. Some offer warranties of up to 5 years.

After sales service

Turbines may not always operate to desired performance levels following initial installation. Certain issues may not become apparent until certain wind speeds are reached or certain actions are required (braking for example). The response of the installer to a request for a call-out from a customer can be a key factor in determining if the customer has a good experience. If at all possible, customers should make contact with existing customers to gauge their opinion on a supplier or equipment. It is vital for the turbine to be kept operating so that the energy in the wind is not wasted while electricity is imported from the grid.

The availability of after sales service is an advantage local or national suppliers and installers have over cheaper, international online suppliers.

Maintenance

Most turbines require some level of maintenance and a schedule for routine maintenance will be recommended by the manufacturer. Some claim to be maintenance free and some turbines require more maintenance than others.

The required maintenance of a turbine can depend on local conditions such as the amount of turbulence experienced by the turbine and the corrosiveness of the air (sea air contains salts for example). A good quality turbine will have key mechanical and electrical components constructed out of marine grade or corrosion resistant materials such as stainless steel and brass.

Turbulent airflow will demand more of a turbine. The loading and unloading of blades and bearings and the extra movement associated will increase wear and tear. An analogy with cars can be used. The shocks of a car which travels with light loads on smooth roads will last much longer than the same model car on rough roads with heavy loads.

Suppliers may offer a period maintenance contract or offer a per-visit charge. Annual maintenance may be as simple as re-greasing wearing surfaces. Ask prospective suppliers what maintenance is required by their turbine manufacturer and ask for an estimate for call-out charges beyond the period covered by the warranty.

Turbines have potential to be dangerous so maintenance should only be carried out by trained individuals. Especially as the turbine will have to be accessed by lowering with a crane or winch or accessed via a raised platform.