Cares renewable ENERGY

Transcription

1 Cares renewable ENERGY Solar panel Handbook

2 Renewable Energy Technologies This Handbook aims to help you to: Learn the fundamentals of Solar Photovoltaic Panels. 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 Solar Photovoltaic Panels handbook includes 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) will 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 Solar Photovoltaic panels Technology description Photovoltaic (PV) technology involves the direct conversion of sunlight into electricity. Solar PV technology uses solar cells, which are grouped together in panels, to produce electricity when exposed to sunlight. Because PV relies on solar irradiation, solar PV provides electricity during the day, with maximum output in summer days. Inverters are an essential component for PV system the inverter converts direct current (DC) from the panels to alternate current (AC) compatible with grid standards. The remaining system components are cabling, switches and meters. Solar PV systems can be roof mounted or ground mounted. If roof mounted drilling into roof rafters will be required in order to install rails to support the solar PV panels. Weatherproof membranes can be used to seal areas between the roof/tiles and the mounting kit. In order to maximise the system s efficiency the panels should be installed on south facing elevations with a pitch angle suited to the location, in Scotland this is around 35 degrees above the horizontal. Solar PV electricity generation has seen a remarkable increase in growth in the past years, with many sites, roof- mounted as well as stand- alone, installed recently across Europe, particularly in Germany, Italy, Spain and the UK. This trend is mainly due to Government schemes and support in many European countries, such as Feed in Tariffs (FIT), grants and tax incentives which are generally followed by a rapid increase of the number of installation. Growth in installations has also occurred in Scotland, where solar irradiation is lower, but economic schemes can now be installed due to the additional income from the FIT. System requirements Any PV system requires the following main components: Panels Solar cabling (DC cabling) Inverter Safety isolators Generation meter Panels Crystalline silicon cells are the most common type of panel and are available in different sizes and power outputs. Power output rating per panel varies between 160W and 250W. A junction box is installed on the back of the panel and will be used to connect the panel to the neighbouring panels in order to achieve the configuration and power output required. In terms of configuration there are two key concepts: row and string: A row of panels is a line of panels that you can see installed on the roof. For example, you can have 18 panels on the roof installed in three rows of six.

4 A string of panels is a number of PV panels electrically connected in series to generate the required output voltage. For example, 18 panels (installed as three rows of six) can be connected in two strings of nine panels. Therefore, one string will be equal to one row and a half. Each string is connected to a separate input on the inverter. As the panels are a key element of the system, a separate, more detailed section on the different types and their application follows this section. Cabling Cables are used to transfer the direct current electricity produced by the panel to the inverter. This cable has double- insulation and is generally supplied with easy to assemble connectors. Cables must be sized to match the system power output. Cable runs should be as short as possible to minimise energy losses. Inverter The inverter is an essential part of a PV system because it transforms the direct current (DC) produced by the solar panels into AC which can be used within the property or exported to the grid. Inverter size must be matched well to the system to optimise both safety and efficiency. The AC power is then fed into the consumer unit within the property via a miniature circuit breaker. The most common commercial inverters are known as string inverters as one or more stings of panels can be connected to a single inverter. Domestic installations, where the electricity is supplied on a single phase, use single phase inverters. Non- domestic installations are generally installed on, or close to, large buildings where a three phase supply is available. In this case a three phase inverter (or three single phase inverters) will be installed based on the system size. An example of a large non- domestic system installed on a three phase supply is given in Figure 1. Safety isolators To maximise the safety of the system for both those using the system and those who will work on it over its lifetime, AC and DC isolators must be included in the circuit. These types of isolators can also be incorporated into the inverter. Generation meter The final key component is the generation meter. As a minimum, a kwh energy meter should be installed to measure the electricity produced by a grid connected PV system. Larger systems will also have a separate export meter, to measure the generation that is in excess of on- site electricity use.

5 Figure 1 Example of a PV system installed on a three- phase supply. (Source: Guide to the Installation of Photovoltaic System)

6 Solar Panel technologies Existing Solar PV technologies include different types of technologies such as wafer- based crystalline silicon (c- Si) cells, as well as thin- film cell using rare materials such as copper indium sulphide (CIS), copper indium gallium selenide (CIGS), cadmium telluride (CdTe) and amorphous silicon. To date, crystalline silicon wafer PV has been the dominant technology, with a 2009 market share of about 80%, with thin- film PV panels (primarily CdTe and thin- film Si) making up the remaining 20% 1. Crystalline silicon technology The most efficient, but most expensive, type of solar cell is monocrystalline, meaning one crystal. These panels are characterised by almost no defects and impurities. The other crystalline silicon technology is called polycrystalline, where cells are made up of many small irregular crystals moulded together. These crystals are smaller than the ones used to make monocrystalline cells and therefore are quicker and easier to grow reducing manufacturing costs and silicon waste. In recent years, the efficiency of polycrystalline panel has significantly improved and panels with efficiencies of 15% can be found on the market for both technologies. Thin-film technology There are various types of thin- film technology, but cadmium telluride (CdTe) and thin- film amorphous silicon are the most common. Depending on the technology, thin- film panels have reached efficiencies of between 7 and 13%. In general, thin- film technology is characterised by simpler manufacturing process and therefore by lower prices. In addition, shading and high temperatures have a lower impact on the system s performance and for this reason this technology is suggested for systems having panels facing both east and west. Because the manufacturing process and the materials used are different, these panels are generally characterised by a more appealing visual impact. On the other hand, due to the lower efficiencies, this technology is not suitable for domestic installation because the area needed to produce a certain amount of power output can be doubled the one required by a system using crystalline technology. Amorphous silicon (a-si) Recent innovations have made this technology more attractive for some large- scale applications. Thin- film panels are made of several thin layers of silicon combined with a PV material, and have an efficiency of around 6-8%. Cadmium telluride (CdTe) CdTe panels use cadmium telluride as PV material. Recent innovations have made this technology more convenient than crystalline silicon when considering large systems. The efficiency is between 9% and 11%. 1 Arvizu, D., P. Balaya, L. Cabeza, T. Hollands, A. Jäger- Waldau, M. Kondo, C. Konseibo, V. Melesh ko, W. Stein, Y. Tamaura, H. Xu, R. Zilles, 2011: Direct Solar Energy. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

7 Figure 2: Example of a monocrystalline solar panel (on the left), a polycrystalline solar panels (centre) and an a- Si solar panel (on the right) The following table shows a number of typical situations where solar PV systems may be installed and suggests the most suitable type of solar panel.

8 Application Suggestion Technology suggestion I have limited space on the roof for solar PV My roof is flat My roof is shaded My roof is facing west and east The roof experiences a wide range of temperatures High efficiency panels also are also space efficient (i.e. less area is required to achieve a specific power output). Flat- roof mounting frames are required to achieve the best inclination and highest performance. An advantage is that the frames can be designed to achieve the optimal orientation and elevation for the site. Shade should be always avoided. The design of the system should avoid any shading issues. Careful selection of the inverter and wiring of panels to the inverter can help to maintain good system performance even in shaded situations. If you have a large flat roof a thin- film system facing east and west can be more cost efficient than using crystalline panels. If you have a pitched roof with two suitable elevations (east and west) a good system design and a suitable inverter can help to achieve best performance. A PV panel s performance depends on temperature: voltage output increases at low temperature and decreases at high temperature. Silicon monocrystalline panels have the highest efficiency rates, typically 15-20%. Silicon polycrystalline panels are less expensive but with a slightly lower efficiency (i.e %). Every type of panel can be mounted on a mounting frame, so there is no influence on the type of panel. Shading can have a dramatic impact on output from a PV system. If shade cannot be avoided, thin- film panels performance is less effected by shading. Micro- inverters, multiple tracker inverters or voltage optimiser can be installed. Thin- film technology is suggested for systems having panels facing both east and west. Silicon crystalline panels can be used, but the connection to the inverter is key. Each string of panels must be created only with panels facing east or west, if a string is created mixing panels installed on the two elevations the performance of the entire system will be affected. Two inverters or a double tracker inverter can be installed to track the two elevations separately achieving the best performance. It is important to size the inverter correctly considering the highest and lowest temperature that a panel could reach during the year.

9 Are solar PV panels suitable for my community group or rural business? Your community group or rural business could consider installing solar PV panels if: There is an appropriate section of unobstructed southeast, south or south west facing roof, or a flat roof, with easy access. The building is not in a conservation area (or the panels can be effectively hidden). Introduction to available schemes and grants Communities or rural businesses who decide to install a PV system can take advantage of different financial support schemes. These schemes are subject to significant change, so they are covered in full detail in the accompanying Toolkits. This section is intended to provide a high level over view of the two main support schemes. FITs up to 250kW FITs 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. This incentive has been mainly used to support PV domestic installations but it can be applied to PV systems with a total installed capacity up to 5MW. FIT payments are made for 20 years after installation. The FIT rates are highest for small- scale systems and reduce for larger systems. There is a lower rate for all sizes of ground mounted system. The rate for roof mounted systems may be the same as ground mounted systems if the building does not have an Energy Performance Certificate (EPC) of level D or higher. There are special consideration for community projects in terms of the energy efficiency and other requirements for the FIT, the definition of community projects and the special treatment of these are described in the Tookit. The EU clearance for the FIT scheme prevents a scheme from claiming the FIT if a public- sector grant has been claimed. FIT rates are now revised downwards every three months and the level of adjustment is calculated based on the deployment rates. The full list of tariff rates can be found in the Ofgem website. Renewables Obligation The Renewables Obligation (RO) is the support scheme intended for large- scale renewable energy projects. Most solar PV schemes will use the FIT, as this is a simpler option to register for and the FIT provides higher levels of incentive for smaller schemes. However, it is possible to claim the RO and to claim a public- sector grant. Tips for project development This section provides a selection of top tips for developing a solar PV project, including tips for installing, planning checks, risks of development. It should be noted this is not an exhaustive list and all projects present individual circumstances to consider.

10 Installation Once a suitable location has been identified, the PV system can be designed. This is a task for qualified and experienced electricians and installer companies. There are two International Standards to which solar PV panels must be tested to guarantee quality, safe design and good manufacturing. These are: BS EN 61215: Crystalline silicon terrestrial photovoltaic panels Design qualification and type approval. BS EN 61646: Thin film terrestrial PV panels Design qualification and type approval. All manufacturers and suppliers should be able to provide copies of their approval to these standards. To access financial support systems in the UK, the solar panel must be certified to the relevant standards. For systems of 50kW and less, the installer and the system need to be accredited by the MCS to claim the FIT. The MCS standards for installation include standards for the assessment of system output a key part of the evaluation process before a decision to invest is made. Before putting a panel on the roof is good practice, and part of the MCS process, to assess the expected output and the ability of the roof to carry the weight of the solar system. Grid connection For smaller systems grid connection is a simpler process, where the local Distribution Network Operator (DNO) needs to be notified that a system complying with grid standard G83 has been connection to their system. It is almost certain that the inverter will comply with the G83 standard, but this should be checked. The simpler route can be used for systems up to 3.6kW (single- phase connection) and 11kW (three phase connection). For larger systems, the DNO must be contacted to get approval under grid standard G59/2. This process will probably require a visit to the site and will incur a fee. Inverters used in domestic installations (up to 3.6kW) must be compliant with BS7671 and adhere to the rules of Engineering Recommendation G83/1, larger inverters must comply with G59/2. Multiple domestic installations Where customers, developers or installers wish to install more than one unit either in a single installation or as part of a development, an application pro- forma (G83/1-1 Stage 2 Application Form) must be submitted to the DNO, in advance. This is an obligation under the Electricity, Safety, Quality and Continuity Regulations The DNO will assess the impact of the connection and will then approve or reject the application. A second and final G83/1-1 application is required within 30 days of commissioning.

11 Checklist 1. PV technology uses energy from the sun to produce electricity, therefore a south facing unobstructed location is ideal for a PV system. Almost all systems in Scotland are installed on roofs. A simple check of orientation using a compass should be made of the orientation of the roof. The inclination can also be measured (e.g. using building plans or from the inside of the roof space (if this is safe to do)). The Toolkit shows how this information can be used to make a ranging short estimate of the suitability of the roof. 2. To gain the highest yield for a PV system, it is important check the shading. While this should be done as part of the installer s survey, a simple check is to view the roof at mid- day in the summer months, is all or part of the roof area under shade? 3. In Scotland, you do not need planning permission for most solar PV systems, as they fall within the criteria for permitted development rights. One of the conditions is that the system would be 50kW or less, almost all non- domestic systems in Scotland are under this level. The Toolkit provides more details on the conditions to fall within permitted development rights. 4. For systems under 50kW, the most likely form of support is under the FIT. For these systems the installer and the system components need to be certified under the MCS. Hence at least three quotations from MCS- accredited suppliers should be obtained. 5. For grid connection, smaller systems can use the simple system of informing the DNO after the system has been installed, the MCS installer will normally undertake this, or prepare the documentation. For larger systems, over 11 kw on a three- phase connection, a more complex process is involved, which will require pre connection approval from the DNO. More details are given in the Toolkit. 6. Your system must comply with Building Regulations: i. Strength of supporting structure and fixing method for panels. Each PV panel weighs about 12kg and assessment of the building structure should be carried out by an approved certifier of design, chartered engineer or other appropriately qualified person. Building Regulations approval may be specifically requested for roof- integrated systems and new building projects. ii. Fire Regulations. Using the BS 476 External Fire Exposure test will give a rating to a type of PV system/mounting for roof coverings, relating to spread of flame between buildings and how close a roof covering can be installed relative to other buildings. This may be necessary as part of planning permission or for larger/commercial buildings. PV panels must not increase the risk of external spread of fire. iii. Ventilation. All roofs must have sufficient ventilation in roof spaces to meet Building Regulations standard BS This is usually done by including ventilation tiles, vents or pipes. These must not be blocked with a PV system. iv. Weatherproofing of panels. Some form of weatherproof membrane, like roofing felt, should be installed underneath panels which are integrated into the roof. 7. Once installed, ensure the panel surface is kept clean.

12 Environmental aspects There are very few environmental concerns about the installation or operation of solar PV systems. Being situated on roofs they will be visible. Hence, on listed buildings and in conservation areas there may be constraints over use. Biodiversity and land use impacts could be important for ground mounted solar park installations. Responsible management of land use and minimising environmental and biodiversity impacts must be considered. Case studies Kirkhill District Amenities Association installed a 4 kw solar PV system on the community hall to generate electricity that is used onsite, with some also exported, the income of which is used to support the maintenance and development of the facility.

13 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