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PV in the UK
Solar PV
PV IN THE UK Early results from the UK photovoltaics field trial Whilst the technology to generate power directly from solar energy has been available for many years, it remains largely underused by the UK building sector. To provide the UK's construction industry with more information on the technology, the Department of Trade and Industry (DTI) has funded a six-year field trial* that studies the design, installation and performance of PV in domestic housing. Fran Cowlin, Building Research Establishment, UK looks at the initial findings.
S
everal countries have made great headway in PV technology - Germany, Japan, the Netherlands, Norway and the USA have all initiated government programmes, in collaboration with industry, which have lead to thousands of solar electric homes being built around the world. Germany in particular has become a world leader in the use of PV, having more than quadrupled its installed PV capacity over the past 15 years. It is hoped that installation of PV in the UK will accelerate in the near future and towards this end the field trial aims to help kick start this process. The field trial strategy and initial findings are described below.
Stage one The first stage of the project concerns the gathering of extensive information on the buildability, operating performance, reliability and maintenance of domestic PV installations. It is tracking the design, construction and installation of over 470 PV systems in 217 dwellings across the UK. Interference between neighbouring systems is also being
Installation rates for PV in the UK should accelerate in the near future
36 reFOCUS
January/February 2005
looked at, as this is of particular concern to the electricity supply industry. It is essential that the information gleaned from the study is as wide-ranging as possible, so the sample covers a range of locations, electricity suppliers, house types, module types and integration methods and involves social and private housing, refurbishment and new build. Communication Communication is key, particularly when a new technology is introduced into the construction process. Initial results show that good contractual arrangements will minimise misunderstandings - contracts should be carefully considered and clear so that everybody involved knows what they are responsible for. Similarly, the allocation of responsibilities at an early stage avoids problems with damage and insurance claims should anything go wrong. Late deliveries incur additional costs, so well-planned logistics are critical in minimising costs and maintaining good working relationships. Good coordination between PV installers and other trades - particularly roofers and electricians - will ensure adherence to quality and the building schedule. Maintaining continuity of contract workers will minimise the need for additional training. Good communication should not be confined to those involved in the construction phase. Close liaison with the electricity distribution and supply companies will minimise connection problems, and tenants are more likely to support an installation if they feel that they have been consulted and involved in the process.
Site and location The project has brought to light a number of issues related to both the siting of PV systems and the location of the installations. Firstly, designers must ensure that PV products comply with British Standards. Most PV products are imported and therefore not necessarily certified to UK standards, even though they might comply with EU standards. For example, when Building Control asked for a PV product from Germany to be tested to BS 476, it failed the Spread of Flame test. This meant the product had to be modified to meet British Standards and tested again before it could be installed. Designers and contractors must take account of regional variations in Building Regulations, as differences can result in increased installation time and higher costs. Scottish Building Regulations, for example, require tiles to be nailed to the roof battens, due to the need for greater wind and infiltration resistance. Sarking (ply and felt) is used instead of battens above felt, which means the solar tile hooks have to be made to different dimensions. The study has shown that mounting systems need to be adaptable to allow for onsite modifications where roofs are irregularly shaped or vary from the expected layout. Vandalism was a problem on some sites, and where this might be an issue, measures should be taken to provide protection. Finally, it is important to make sure the electricity meter is compatible with the PV system - some prepayment meters do not Further information Please contact BRE Environment on Tel: +44 (0)1923 664500. www.bre.co.uk *The UK Photovoltaic Domestic Field Trial has been funded under the DTI's New and Renewable Energy Programme. BRE is responsible for co-ordinating the project teams involved.
1471 0846/05 © 2005 Elsevier Ltd. All rights reserved.
Solar PV
allow electricity export and can be damaged if this is attempted. Good practice Standards and regulations need to be adhered to for installation, labelling, and health and safety. This is important from a technical point of view, but also improves customer perception. Handover documentation must be well-prepared and cover all of the necessary points, particularly safety aspects. It is likely that each dwelling will change occupier several times within the lifetime of the PV system, so documentation must meet the needs of future occupiers. Cost Cost varied considerably between sites. Most of the retrofit sites had above-average installation costs, due to the systems being add-ons, rather than integrated processes. More effort and more man-days are required to add a system into an existing building than for a new build, where it can be included at the design stage. Tile-integrated installations were the most expensive, mainly due
www.re-focus.net
to the high cost of the tile PV system. The majority of other installations were much cheaper, with new-build frame-mounted installations coming in as the cheapest option. Significant savings can be achieved when integrating frame-mounted systems into new build, as the costs of site works, storage and scaffolding are shared by other construction works. Figures show that module and installation costs are falling year by year. This is thought to be a result of the introduction of capital grants, which not only increase demand, but also give positive signals to the PV industry. Reduced costs also indicate that the UK's PV market is moving towards a more streamlined process.
Stage two The second stage of the project monitors the day-to-day performance of each PV system. Data is being collected and analysed over a period of two years, which will allow the system designs and climatic conditions to be compared both on a short-term and long-term basis. One of the main concerns about PV is that the UK does not get enough sunshine for it
to be viable. This would not seem to be the case. The findings so far show that, even with a moderately sized system, a significant proportion of a dwelling's electricity requirements can be obtained in the UK climate over 40% on average. And whilst almost all of the sites had systems where outputs were lower than expected, this was usually caused by shading from other buildings or trees, and occasionally from the home itself. In all cases, the PV systems have been easily accommodated on the roofs, and larger installations could have been fitted for most sites had it not been for cost restrictions. As only a few systems are providing regular data at present, the results of the analysis are preliminary. Most remaining projects are expected to start providing data this year and, at this point, the monitoring process will be extended to consider issues such as inverter sizing, array efficiencies and fluctuation in export and load levels. Overall there is still a considerable amount of important information to be gained. The next Annual Technical Report will be available early in 2005 and the final results will follow early in 2006.
January/February 2005
reFOCUS 37
PV IN THE UK Early results from the UK photovoltaics field trial Whilst the technology to generate power directly from solar energy has been available for many years, it remains largely underused by the UK building sector. To provide the UK's construction industry with more information on the technology, the Department of Trade and Industry (DTI) has funded a six-year field trial* that studies the design, installation and performance of PV in domestic housing. Fran Cowlin, Building Research Establishment, UK looks at the initial findings.
S
everal countries have made great headway in PV technology - Germany, Japan, the Netherlands, Norway and the USA have all initiated government programmes, in collaboration with industry, which have lead to thousands of solar electric homes being built around the world. Germany in particular has become a world leader in the use of PV, having more than quadrupled its installed PV capacity over the past 15 years. It is hoped that installation of PV in the UK will accelerate in the near future and towards this end the field trial aims to help kick start this process. The field trial strategy and initial findings are described below.
Stage one The first stage of the project concerns the gathering of extensive information on the buildability, operating performance, reliability and maintenance of domestic PV installations. It is tracking the design, construction and installation of over 470 PV systems in 217 dwellings across the UK. Interference between neighbouring systems is also being
Installation rates for PV in the UK should accelerate in the near future
36 reFOCUS
January/February 2005
looked at, as this is of particular concern to the electricity supply industry. It is essential that the information gleaned from the study is as wide-ranging as possible, so the sample covers a range of locations, electricity suppliers, house types, module types and integration methods and involves social and private housing, refurbishment and new build. Communication Communication is key, particularly when a new technology is introduced into the construction process. Initial results show that good contractual arrangements will minimise misunderstandings - contracts should be carefully considered and clear so that everybody involved knows what they are responsible for. Similarly, the allocation of responsibilities at an early stage avoids problems with damage and insurance claims should anything go wrong. Late deliveries incur additional costs, so well-planned logistics are critical in minimising costs and maintaining good working relationships. Good coordination between PV installers and other trades - particularly roofers and electricians - will ensure adherence to quality and the building schedule. Maintaining continuity of contract workers will minimise the need for additional training. Good communication should not be confined to those involved in the construction phase. Close liaison with the electricity distribution and supply companies will minimise connection problems, and tenants are more likely to support an installation if they feel that they have been consulted and involved in the process.
Site and location The project has brought to light a number of issues related to both the siting of PV systems and the location of the installations. Firstly, designers must ensure that PV products comply with British Standards. Most PV products are imported and therefore not necessarily certified to UK standards, even though they might comply with EU standards. For example, when Building Control asked for a PV product from Germany to be tested to BS 476, it failed the Spread of Flame test. This meant the product had to be modified to meet British Standards and tested again before it could be installed. Designers and contractors must take account of regional variations in Building Regulations, as differences can result in increased installation time and higher costs. Scottish Building Regulations, for example, require tiles to be nailed to the roof battens, due to the need for greater wind and infiltration resistance. Sarking (ply and felt) is used instead of battens above felt, which means the solar tile hooks have to be made to different dimensions. The study has shown that mounting systems need to be adaptable to allow for onsite modifications where roofs are irregularly shaped or vary from the expected layout. Vandalism was a problem on some sites, and where this might be an issue, measures should be taken to provide protection. Finally, it is important to make sure the electricity meter is compatible with the PV system - some prepayment meters do not Further information Please contact BRE Environment on Tel: +44 (0)1923 664500. www.bre.co.uk *The UK Photovoltaic Domestic Field Trial has been funded under the DTI's New and Renewable Energy Programme. BRE is responsible for co-ordinating the project teams involved.
1471 0846/05 © 2005 Elsevier Ltd. All rights reserved.
Solar PV
allow electricity export and can be damaged if this is attempted. Good practice Standards and regulations need to be adhered to for installation, labelling, and health and safety. This is important from a technical point of view, but also improves customer perception. Handover documentation must be well-prepared and cover all of the necessary points, particularly safety aspects. It is likely that each dwelling will change occupier several times within the lifetime of the PV system, so documentation must meet the needs of future occupiers. Cost Cost varied considerably between sites. Most of the retrofit sites had above-average installation costs, due to the systems being add-ons, rather than integrated processes. More effort and more man-days are required to add a system into an existing building than for a new build, where it can be included at the design stage. Tile-integrated installations were the most expensive, mainly due
www.re-focus.net
to the high cost of the tile PV system. The majority of other installations were much cheaper, with new-build frame-mounted installations coming in as the cheapest option. Significant savings can be achieved when integrating frame-mounted systems into new build, as the costs of site works, storage and scaffolding are shared by other construction works. Figures show that module and installation costs are falling year by year. This is thought to be a result of the introduction of capital grants, which not only increase demand, but also give positive signals to the PV industry. Reduced costs also indicate that the UK's PV market is moving towards a more streamlined process.
Stage two The second stage of the project monitors the day-to-day performance of each PV system. Data is being collected and analysed over a period of two years, which will allow the system designs and climatic conditions to be compared both on a short-term and long-term basis. One of the main concerns about PV is that the UK does not get enough sunshine for it
to be viable. This would not seem to be the case. The findings so far show that, even with a moderately sized system, a significant proportion of a dwelling's electricity requirements can be obtained in the UK climate over 40% on average. And whilst almost all of the sites had systems where outputs were lower than expected, this was usually caused by shading from other buildings or trees, and occasionally from the home itself. In all cases, the PV systems have been easily accommodated on the roofs, and larger installations could have been fitted for most sites had it not been for cost restrictions. As only a few systems are providing regular data at present, the results of the analysis are preliminary. Most remaining projects are expected to start providing data this year and, at this point, the monitoring process will be extended to consider issues such as inverter sizing, array efficiencies and fluctuation in export and load levels. Overall there is still a considerable amount of important information to be gained. The next Annual Technical Report will be available early in 2005 and the final results will follow early in 2006.
January/February 2005
reFOCUS 37