Cares renewable ENERGY

Transcription

1 Cares renewable ENERGY WIND ENERGY Handbook

2 Renewable Energy Technologies This Handbook aims to help you to: Learn the fundamentals of renewable wind energy generation. Explore and discuss the range of technologies and options available to your community. Evaluate which technologies or options may be appropriate for your community. Identify and access valuable online resources for further information and advice. It discusses the variety of technologies that have been employed by community groups across Scotland. The principles of how the technology works is provided along with the key issues regarding installation and operation as well as environmental impacts. The Wind Energy handbook will include the following sections: Technology description. Technologies available on the market. System requirements. Is the renewables technology suitable for your community group? Introduction to available schemes and grants. Tips for project development. Environmental aspects. Case study. This Handbook is intended as an introductory text, covering the main aspects and issues that need to be considered for each of the technologies listed above. A separate set of Toolkits, (available Autumn 2013) provide more detailed guidance and tools to assist community groups and rural businesses to develop a renewable energy project. Like the Handbook the Toolkits will be available on the CARES web site: localenergyscotland.org.uk

3 Wind energy Technology description Wind is one of Scotland s most abundant renewable energy resources. In fact, over 25% of Europe s wind resource is found in Scotland 1. A significant proportion of this UK capacity is installed in Scotland, demonstrating the level of this resource. According to the UK Wind Energy Database (UKWED) 2 Scotland had almost 4,000 MW of onshore wind capacity operational by July Wind energy technology ranges from small wind turbines (rated in the range of 0.05kW (50W) to 50kW), medium scale turbines, (50 kw to 500 kw) and large- scale turbines rated above 500 kw. Large- scale wind turbines are a mature and proven technology, and are one of the most well developed and economically viable forms of renewable energy in the UK. Some types of small wind technology have also matured and newer turbines in the small- to medium- scale range are increasingly being deployed. The majority of turbines are designed to be free- standing structures. However, there are some small (typically 1kW to 6kW) building- mounted wind turbines available that are intended to be situated on the roof of a building. A wind turbine produces electricity by capturing wind energy. The natural power of the wind makes its blades turn and the turning then drives a generator. The energy content of the wind is very dependent on the wind speed. In fact, the energy content is related to the cube of the wind speed (Wind speed A Energy content A 3 ). What this means is that if the wind speed doubles, the energy content of the wind increases by eight (i.e. wind speed 2 = energy content 8). The larger the area swept by the turning blades, the greater the amount of wind energy captured. The electricity generated by a turbine can supply power to a building (electricity system), heat it (connected to electrical storage heaters or wet system storage vessel) or supply the national grid. Due to the relationship between wind speed and energy, changes in wind speed result in large changes in power produced. Hence, at any moment the output for a wind turbine will depend on local wind speed conditions. Therefore, it is very difficult to exactly match the output of a wind turbine to the electricity demand of a specific building. For this reason, the majority of wind turbines are connected to the grid and export some, or all, of the electricity produced to the grid. If the turbine is also connected to a building then the turbine will provide some, but not all, of the electricity needed. For medium and large- scale turbines it is more likely that the turbine will be located at some distance from a building and this may reduce the opportunity for direct use of the electricity. While short- term wind speed, and hence turbine output will vary, the investment decision for a wind turbine will use long- term wind speed data. This allows an assessment of long- term energy production and hence income from the wind turbine investment. Long term Met Office data is used, linked to analysis of wind speed at the location of the proposed turbine. 1 Source: sectors/wind- energy.aspx / 2 Source: UK Wind Energy Database: energy/wind- energy/uk- wind- energy- database/index.cfm (accessed 11/07/2013)

4 Typically the choice of both site and size of turbine will be dictated by the average wind speed over the year at the predicted hub height (the height above the ground that the turbine hub is located). The proposed location for the wind turbine should be open to the direction of the prevailing wind. Locations with trees, buildings or other features that will block the wind are less suitable. System requirements The main system components are: The turbine comprising the tower, blades and generator The foundations often concrete The grid connection the electricity connection to the local electricity grid and on site electricity use Access tracks for installation and maintenance The majority of wind turbines installed are horizontal axis designs. Typically these have two or three blades rotate in a vertical plane perpendicular to the wind. The blades are attached to a horizontal shaft which drives a gearbox and hence the electricity generator. The hub and blades are mounted on masts or towers and are able to rotate (yaw) around the mast so that they are aligned with the wind direction. This is in order to maximise output. At higher wind speeds the energy in the wind will be too great for the turbine. Hence the power output from the turbine will need to be reduced to protect the machinery. The output of horizontal axis turbines can be controlled by two methods. These are pitch control, where the angle of the rotor blades can be actively adjusted by the turbine s control system, or stall control, which is a passive system that relies on the design characteristics of the blades to exercise control. The design and scale of foundations will depend on the size of the turbine. Larger turbines will need reinforced concrete foundations, and hence access for the construction vehicles for the foundation. For a wind turbine project to be viable, it is likely to require connection to the grid. Therefore, a suitable nearby grid connection is required. Connecting to the grid over a long distance can be prohibitively expensive. Therefore, it is important to ensure a suitable nearby grid connection is available during the early stages of a wind turbine project. Large renewable energy projects in particular will need to be connected to the grid. This could be either to the local distribution network (11kV, 33kV in Scotland) or to the transmission network (above 132kV). Alternatively, if there is sufficient demand in the locality, a private wire (private grid system) network could be developed to directly supply electricity to large consumers. Most wind projects will be directly connected to their local distribution network operated by the Distribution Network Operator (DNO), with 100% export of electricity. The two DNOs in Scotland are Scottish Hydro Electric Power Distribution (SHEPD) and Scottish Power Distribution. Both offer guidance on their websites Scottish Power Energy Networks, and SSE Power Distribution. Gaining a grid connection can be a costly process, and applicants should have as much information and technical detail as possible before requesting a connection. Currently many parts of the Scottish grid infrastructure are at full capacity, and connections for new generation can incur a very lengthy lead in time before they become operational.

5 The requirement for access tracks will be strongly influenced by the scale of the turbine and hence the dimensions and weight of the main components. Small turbines and most medium turbines can be installed without use of specialist vehicles or access roads. Large turbines may need a crane for assembly of the tower and the lift of the blades and generator assembly to the top of the tower. Hence large turbines need tracks that the crane can negotiate and also require laydown areas for the main turbine components. Available technologies There are two main types of wind turbine design horizontal axis wind turbines and vertical axis wind turbines. Horizontal axis turbines are the most commonly available type of wind turbine, and these are generally the only turbine designs available in the larger- scale range. These types of turbine have turbine blades spinning perpendicular to the ground with the turbine shaft horizontal to the ground. Horizontal axis turbines are available in models from a few kw to several MW. Vertical axis turbines spin horizontal to the ground with the turbine shaft perpendicular to the ground. The vertical axis wind turbines that are available are small scale. Horizontal axis turbines Source: Community Energy Vertical axis turbine Source: Community Energy Figure 1: Types of wind turbine There are many examples of large- scale horizontal axis wind turbines installed across Scotland. Turbine sizes used in projects for community groups and rural businesses range from 5 kw to 3MW, with rotor diameters that span from 6m to 100m. With horizontal axis wind turbines, the circular area defined by the tips of the blades is called the swept area. The swept area is proportional to the rotor diameter squared, so by doubling the rotor diameter, the swept area is four times larger (i.e. rotor diameter 2 = swept area 4). This means that the power output from the turbine is also increased, as mentioned above the larger the swept area, the more power can be captured from the wind. For these simple reasons, larger wind turbines are typically more cost effective as they capture more energy from the wind for proportionally less cost of the turbine. However, consideration needs to be given to a variety of other issues, such as the project purpose, costs, timescales and public acceptability of larger scale turbines.

6 Are wind turbines suitable for my community group or rural business? Your community group or rural business could consider installing a wind turbine or becoming involved with a wind turbine project if: You have a building which you would like to provide with renewable electricity? Is there a developer locally who has recently received planning consent for a wind farm and would your community group be interested in investing in this wind farm? Do you have a site where the average wind speed is at least 5m/s at 45m above ground level? Do you have a suitable site which is relatively open and exposed to the prevailing winds? If you are considering large- scale turbines, is there good access to the proposed wind turbine site? Further information is available by contacting Local Energy Scotland on Introduction to available schemes and grants Communities or rural businesses who decide to install a wind energy system can take advantage of different supporting schemes. These schemes are subject to significant change, so the full details are covered in full detail in the accompanying CARES toolkit. This section is intended to provide a high level over view of the two main support schemes. Feed-in Tariff (FIT) Feed- in Tariffs were introduced on 1 April 2010 and replaced UK Government grants as the main financial incentive to encourage uptake of small- scale renewable electricity- generating technologies. Under the scheme, developers in England, Scotland and Wales have been eligible to receive FITs for electricity generated from renewable sources, including wind. Systems up to 5MW capacity are eligible, meaning that many community and rural business scale projects can benefit from the scheme. The FIT consists of a generation tariff, which is a payment for each unit of electricity generated, and an export tariff, for each unit exported to the grid. For wind turbines, tariffs are paid for 20 years. Tariffs are index- linked to RPI. The FIT rates are highest for small- scale systems and reduce for larger systems. The full list of tariff rates can be found in the Ofgem website 3. All systems installed after July 2009 are eligible to claim FITs. In order to be eligible, installations need to comply with planning, regulatory and legal obligations. Systems below 50kW need to be certified by the Microgeneration Certification Scheme 4 (MCS) and be installed by a company accredited under the MCS. There is a separate accreditation process for systems above 50kW (the Renewables Obligation Order Feed- In Tariff (ROO- FIT). The EU clearance for the FIT scheme prevents a scheme from claiming the FIT if a public- sector grant has been received in support of the purchase and/or installation of the generating equipment. Renewables Obligation The Renewables Obligation (RO) is the main support scheme for larger scale renewable energy projects in the UK. The RO requires UK electricity suppliers to source an increasing proportion of the electricity they supply from renewable sources. Renewables Obligation Certificates (ROCs) are green certificates that are issued to operators of accredited renewable energy generating stations for the eligible renewable electricity they tables/pages/index.aspx

7 generate. The required electrical energy (MWh) generated for a ROC to be issued depends on a combination of factors, including technology, location, accreditation date, installed capacity, fuel mix and any statutory grants claimed. Operators trade their ROCs with other parties and the ROCs are used by electricity suppliers to demonstrate that they have met their obligation. To be eligible to claim ROCs, a generating station must have obtained accreditation. ROCs cannot be claimed by installations claiming FITs. Where a grant might be received by a site, the developer should check with the grant provider whether it is also possible to claim ROCs, as rules vary depending on the grant and level of ROC claimed. Tips for project development A community group or rural business looking at a potential wind energy project should first assess the site (or sites) under consideration for wind resource. Some key points to consider while carrying out this assessment are: Resource availability Site suitability What is the average wind speed at the site? The economic viability of a project depends on the average wind speed at the site (as this influences the energy available to capture). Therefore, the average wind speed on site needs to be high enough to make a project financially viable. Site wind speeds (and levels of turbulence) can also influence the decision on the size or type of turbine to be installed. These decisions all impact on the costs of getting the turbine(s) installed and operational. Average wind speeds can be checked using the national wind speed database 5. Site monitoring mast can be installed to obtain more details on site wind speeds. The best sites will be free of obstructions that might alter the wind energy available to the turbine. Obstructions create two effects, reducing wind speed and hence energy output and creating turbulence that will add wear to the turbine, increasing maintenance costs and reducing technical viability. Typical obstructions include tall buildings, hills or trees. These can have a significant impact, over a significant distance from the obstruction as shown in figure 2. The impact will be more pronounced of the obstruction is in the direction of the prevailing wind. Prevailing wind direction is typically from the southwest in the UK, though this varies by site. 5

8 Figure 2: Impact of obstructions on wind turbines Planning Rural sites in gentle terrain, with few obstacles nearby, are more likely to be open and exposed, with less turbulent wind speeds. Is there suitable land available to install a turbine? This includes suitable space to accommodate delivery and installation of the main turbine components. Ground characteristics, such as rock strata close to surface of soil, can influence the ability to lay foundations for a turbine. Is there a possible grid connection point nearby? Wind supplies electricity intermittently, so a grid connection is likely to be required on site, particularly if the site requires a continuous electricity supply. In addition, a connection would also be required for export of electricity to the grid. The majority of wind turbines will need planning permission. Micro wind turbines within the boundaries of a home can, in some cases, be installed as permitted development. For community groups and rural businesses it is almost certain that planning permission will be required. To prepare a planning application takes time and hence money and the application may not be successful. Hence the identification of potential planning issues is an important step in the search for suitable sites. Planning issues are complex and covered in more detail in the Toolkit.

9 Installation Checklist Some of the planning issues are proximity to buildings and land designations. Are there buildings nearby that could be affected by noise or shadow flicker? If buildings nearby, particularly housing, are likely to be impacted by noise or flicker from the turbine, this may reduce the likelihood to obtaining planning permission for a wind turbine. Is the site in an area of land that is designated, e.g. in a national park or site of special scientific interest? Obtain planning consent can be more onerous in some types of designated area. Is there suitable access to the site? Large turbines can sometimes be problematic if access to a site is difficult. For example, narrow roads or low bridges on routes leading to the site can be restrict terms of the size of vehicles (and hence turbine parts) that can be brought to the site. Prior to installing a wind turbine, there are several points that should be considered. Some of these considerations are listed below. It should be noted this is not an exhaustive list and all projects present individual circumstances to consider. 1. When you have chosen your turbine, consult with other owners who can vouch for its reliability and effectiveness. 2. You will need planning permission and agreement with the landowner to erect a turbine. 3. You need to decide how your generated electricity is to be used (e.g. grid connected, standalone or direct heating). 4. Check if the system you choose allows you to claim FITs or ROCs. If the turbine is to be connected to the grid you will need an agreement with the local electricity Distribution Network Operator (DNO) and an agreement with an electricity supplier to purchase your export electricity. Ensure you check the warranty on any machine and that there will be a post installation maintenance service. Check with the manufacturer that spare parts will be available for your turbine in the future. Remember to calculate a payback time for the turbine using typical wind data for the area to make sure it is a viable option. Wind turbines operate the most effectively in large open areas with minimal tall buildings, hills or trees which cause turbulence. Make sure you receive all information about the system from your installer, including how to shut down the turbine in excessive winds. Organisations such as RSPB and Scottish Natural Heritage should be consulted and can give advice on how to avoid harm to wildlife.

10 Environmental aspects When scoping and designing a wind turbine project, particularly on the larger scale, developers should always consider the impacts of the proposed development on both the natural and historic environments. Local authorities also consider these when determining planning applications for projects, including the impact of a development on the wider landscape setting and visual amenity. A developer should particularly consider any impact on designated and significant undesignated sites and areas, including the implications of development on their setting or on local flora and fauna. Considerations should embrace the direct physical impact of developments, any indirect impacts and potential cumulative impacts (particularly if other wind turbines or farms are sited locally). Local authorities will often require environmental impacts to be adequately considered as part of the process of preparing any Environmental Statement or EIA. Case studies Uig Community shop invested in two 5kW wind turbines to meet the shop s high electrical demands and to provide a revenue stream through FIT income. The Dundee Heritage Trust used a 6 kw wind turbine to reduce running costs of the Discovery Point Museum.

11 Commissioned by the Scottish Government and Energy Saving Trust. Produced by Community Energy Scotland Limited and Ricardo- AEA Ltd Queen s Printer for Scotland 2009, 2010, 2011, 2012 This document was last updated July 2013