Solar PV roof tile installation at Herne Hill School

Solar power's contribution to electricity in the UK is still relatively small. But with growing pressure to cut carbon emissions from buildings, along with rising electricity prices and the Feed in Tariff, solar solutions are at last taking off.

Solarcentury has been at the forefront in showing the practical and effective ways that solar systems can be used in buildings across the UK - even in crowded urban locations. The company has developed a range of top quality solar products for integrating solar systems into a wide variety of buildings. These include solar PV panels and tiles, solar water heating and mounting systems.

New home buyers are pleased with the aesthetics and particularly impressed that solar tiles can save them money. We're doing this not just because it makes commercial sense, but because we believe it makes sense for the future. It will help to shape the homes we'll build for the future

David Pretty, Chief Executive of Barratt Homes

Context

Despite the geographical location of the UK, there is considerable potential for supplying a significant amount of energy from solar systems on buildings, both electricity from solar photovoltaics (PV) and heat from solar thermal systems. Such systems do not require additional space for installation, provide electricity and heat at the point where it is used, and have low maintenance requirements and running costs. For all these reasons they can be effective in urban areas where using other types of renewable energy can be difficult. 

The current contribution of solar to UK energy use is small, partly due to the high initial cost of the technology, and very limited government support compared to that in other European countries. However, with increasing requirements to reduce the energy demand and carbon emissions from buildings, together with rising electricity prices and commercial corporate social responsibility commitments, integrated solar solutions will become increasingly important. Solarcentury has been a leader in showing the practical, innovative and effective ways in which solar systems can be used in buildings.

The organisation

Solarcentury is a business which designs and installs solar systems for buildings in the UK and continental Europe, and provides wholesale solar products. Most of the work of Solarcentury is in solar photovoltaics (PV) for which it is the UK market leader, but solar thermal systems are also provided. The company was founded in 1998 by Jeremy Leggett, the CEO, and is based in central London. It currently employs over 80 staff and has a turnover of over £14 million/year.

Staff and students at Herne Hill School with their solar power meter.

Technology and use

Photovoltaic (PV) modules generate electricity directly from solar energy and work in both direct sunlight and diffuse skylight. The electrical output from a PV module is dc but can be converted to ac using an electronic inverter. Most of the PV installed by Solarcentury is in grid-connected ac systems. In these, the output from the inverter is connected to the electric mains supply of a building so that, whenever available, the PV electricity is used instead of mains.

Solarcentury buys PV modules and inverters from different international manufactures. Its key aim is to develop suitable mounting systems and installation procedures to make solar systems that fit a wide range of buildings. This means that appearance, ease of installation and cost of the system are all important factors. Local Authority planning requirements can be demanding in the urban and rural environments where many PV systems are installed, and Solarcentury has worked closely with planners and building developers to provide acceptable designs. Because of this, Solarcentury has a wide range of products, each designed for a particular type of building.

The product with the largest installed capacity (over 2 MWp to date) is the Energy Roof, which has a mounting system designed for retrofitting onto large roof areas, including warehouses, factories and offices. A recent development of this product is designed to integrate with the rapid building processes used for new commercial buildings. The product uses 1 kWp of modules and a preassembled framed unit attached to a single beam. The frame can be lowered directly onto any flat or gently sloping roof and quickly adjusted to the optimum angle for maximum solar gain, after which the modules are slotted in.

The Sunstation is also a popular solution, similar to the Energy Roof but targeted at the domestic market. Because the available area of roof is often a limitation in domestic installations, the Sunstation uses high efficiency Sanyo modules so that the 1 kWp output can be supplied from as small an area as possible, currently about 6 m2 of modules. It is usually retrofitted onto an existing roof, although it is also possible to integrate as part of a new roof. The Sunstation is also available in a solar thermal version, for providing hot water.

Other solutions developed by Solarcentury are designed to replace conventional building elements in new-build developments, or major building refurbishments. For homes, Solarcentury has developed solar PV tiles that are sized to replace four UK standard concrete roof tiles. This allows a roof to be built with the PV tiles integrated into its structure, and results in a very unobtrusive installation that does not require planning permission. The tiles are easy to fit, and can be installed and plugged together by a non-specialist roofer, with a qualified electrician needed only to make the final connections to the inverter and mains. The PV modules for the tiles, rated at 52 Wp each, are custom made for Solarcentury, and the tiles are assembled in the UK. A recent development is a tile of the same size that incorporates a solar water-heating panel rather than a PV module. These solar thermal tiles are designed with simple interconnecting plumbing fittings, so that a Complete Solar Roof can be provided to contribute significantly to both the electricity and hot water needs of a home.

The company has developed a range of top quality solar products for integrating solar systems into a wide variety of buildings. 

Training, support and quality control 

Users of solar PV and solar thermal systems require very little training, as the systems are largely automatic: this is one of the major benefits of solar systems compared with other renewable energy supplies. 

Training is given to installers of solar PV, who are either Solarcentury staff or contractors, or independent wholesale customers. The PV and thermal roof tiles were designed specifically so that they could be installed and interconnected by experienced roofers with only a half-day training. 

For quality control, Solarcentury follows up all customers by telephone to ensure they are satisfied with the system and its operation. The majority of modules are supplied with a 25-year warranty, but should last much longer. Inverters are expected to last for at least seven years. 

Solarcentury provides information and training about solar and other renewable energy systems to a wide range of interest groups and individuals. This includes seminars for local authority planners, continuous professional development courses for architects, and specific advice services for customers.

Benefits

Environmental benefits

Solarcentury has shown how solar PV and thermal systems can be used effectively and attractively in a wide range of buildings in the UK. PV is simple to use, even in crowded urban areas, and can be installed rapidly. Owners, users and Local Authority planners like the appearance of the systems and how well they integrate with buildings. In fact some owners have said that they would have liked their PV systems to be more obvious, to emphasise their environmental commitment! Feedback through many different channels confirms that PV is a popular renewable energy technology. As legislation puts increasing requirements on the reduction of carbon emissions from buildings, and use of on-site renewable energies, this clear evidence about the suitability and adaptability of PV will be invaluable.

The 3 MWp of PV installed to date by Solarcentury is generating an estimated 2,370 MWh/year of electricity, mostly directly to the buildings of users so avoiding distribution losses. By replacing grid electricity, this prevents the emission of about 1,350 tonnes of CO2 a year. (Note that modern PV production, the energy used in the system manufacture is recouped within about three years of operation even in the UK climate.) To date Solarcentury has installed solar thermal systems on about 40 houses, but there is significant potential for future growth in this area.

Economic and social benefits

PV customers benefit from the very low maintenance costs of PV, so that once the capital cost has been paid, the PV electricity is virtually free, and they are insulated from future price rises. The buildings where Solarcentury installs are often used during the daytime, so a considerable proportion of the PV electricity generated is used directly, saving electricity purchased at around 10p/kWh. In many installations any PV electricity can be sold back to the supply company. Some Solarcentury customers have found that seeing how much energy is being generated is a powerful incentive to reduce electricity consumption as well. 

Developers have found that purchasers are enthusiastic about houses with PV installed. In one development, homes with PV roof tiles sold faster and for an average of 8.6% more (£12,000 in this case) than identical homes without. Individual homeowners who had their houses valued have seen similar increases. This shows that people are willing to pay for the benefits of PV when it is simple to get (already on the house) and the cost can be included in a mortgage. 

The work of Solarcentury has created approximately 80 jobs within the company itself. In the wider market, it has helped create about 30 further jobs in the UK by building the demand for solar PV, employing contractors to perform installations, and supporting independent installers through the wholesale business.

Potential for growth and replication

Solarcentury is a fast-growing company which intends to maintain a high rate of growth over the coming years, and it has also helped the UK solar PV market as a whole to grow, through its contractors and independent installer network. Solarcentury is currently the dominant company in the UK PV market, and also works in continental Europe, in particular Spain and France.There is sufficient interest in PV in the UK for Solarcentury and other businesses to grow, if the UK government gave the level and continuity of support that has occurred in other countries, such as Germany and Spain.