Products - Solar Panels
Solar Photovoltaics (PV)
Photovoltaic panels allow the conversion of light into electricity.
Generating electricity from the sun - Photovoltaics (PV)
Photovoltaic cells use light to generate electricity. There are a number of PV panel technologies, including polycrystalline, monocrystalline and thin-film. Solar PV cells can be arranged in panels on a building's roof or walls, and can often directly feed electricity into the building. With the latest PV technology, cells can also be integrated into the roof tiles themselves. Groups of solar PV cells can be added together to provide increasing levels of power. This can range from small, kilowatt-sized solar panels for use in domestic households, to larger arrays, which function as separate solar power plants feeding power directly into the electricity grid.
PV panels are particularly suitable where a grid connection is difficult and the popular combination of a micro-wind turbine and PV panel uses the fact that there is more wind in the winter when the sun is weak and vice versa to provide a more reliable energy supply. You may have seen this technology on temporary signage on the motorway; a typical combined solar and wind application.
There are currently thousands of very small scale PV powered systems in use in the UK, for applications such as phone booths, traffic monitoring, street lighting, road signage. In the leisure industry there has been a significant take-up of PV technology for battery charging on boats, caravans and motorhomes and in garden applications such as lighting and powering aquatic features.
PV modules are connected together to form an array, and the array supplies electricity to a battery store or, more commonly nowadays, to the local electricity grid.
Grants of up to 50% have made PV systems more affordable and domestic electricity generation is becoming a widespread reality.
It is now possible to generate clean, green electricity from an array of solar panels mounted on your roof, and sell it to your supplier. Alternatively, if you do not live near the grid, then the grant scheme also covers off-grid applications.
Solar Photovoltaics (PV) - Introduction
The choice of system depends upon the following criteria:
System size
This is generally dictated by one of 3 factors: demand matching, available space, and budget. Where space and budget allow, it is nice to able to match the demand of a property.
System size is given as the kilowatt peak (kWp) value which is the maximum output under ideal conditions. Typically domestic systems range from 1kWp - 5 kWp.
Each 1kWp of installed capacity will produce between 750 - 900 kilowatt hours (kWh or units as they are referred to on your electricity bill) annually and will take up about 8 square metres of space. The average UK household consumes 3,200 kWh annually.
PV heating systems are generally significantly more expensive than solar heating systems, but they do have the advantages that there are no moving parts so are simpler and more reliable to maintain and waterproof PV panels can be incorporated into a roof as part of the structure replacing tiles.
A typical domestic 1 kilowatt (1kW) system will cover about 10 square metres, and produce about 750kWh (units of electricity) over a year - mostly in the summer. At that level the payback on £5000+ system is very long even with the grants available, and it is not yet a viable technology where one might consider selling any excess to the grid unless one installs a large array.
The cost of PV systems is falling as the efficiency of solar panels increases and the cost of manufacturing declines due to the introduction of new technologies, such as thin-film solar PV. The DTI's Renewables Innovation Review estimated that solar PV could become cost-competitive with other forms of electricity generation by 2020-30.
System location
PV systems can be roof mounted, ground mounted or tracker mounted. The choice is often made to meet practical needs, but in the case of the tracker (which follows the arc of the sun) the choice is made to maximise the output.
Roof system type
PV systems are either mounted over the roof on a proprietary frame system or can be integrated into the roof to form part of the watertight roof covering. Roof integrated systems are generally more expensive.
Grid Connection
To install a grid-connected system, you will need permission from the local Distribution Network Operator (DNO). This is the company who operates the distribution network in your area, and may not be your electricity supplier. DNOs have different policies when it comes connecting small scale renewable generation systems to their networks. To find out who your local DNO is visit the www.pv-uk.org.uk British Photovoltaic Association website, from where you can also download application forms for DNO permission.
The Distribution Code of Licensed Network Operators: www.dcode.org.uk
You will need an inverter to transform the low-voltage DC power produced by a PV roof or wind turbine into high-voltage AC power that meets the quality requirements of the electricity network.
Look for inverters that meet the Engineering Recommendations G83/1 - 'connection of small-scale embedded generators in parallel with public low-voltage distribution networks', which sets out technical requirements that small-scale generators need to meet in order to connect to the mains network. These are only recommendations, but as they have been agreed by the DNOs, applications that conform are usually processed more quickly.
Planning
The government's Planning Portal website gives guidance on planning for domestic renewable projects. A link to it can be found in government departments.
Grants
Solar photovoltaics is one of the supported technologies within the DTI's Low Carbon Building Programme providing grants for microgeneration technologies for householders, community organisations, schools, the public sector and businesses.
Useful Links
British Photovoltaic Association: www.pv-uk.org.uk
Solar Heating/Hot Water
Solar hot water systems will typically heat about half the average household's annual hot water requirements, thereby saving about one tonne of C02 per year.
Most of the benefit is in the summer months when there is the maximum solar gain, although the system does not require direct sunshine to operate as long as the sky is bright. Solar hot water systems work very well in conjunction with biomass heating systems.
For customers with Agas and an alternative method of cooking, fitting a solar water system will mean you can turn off your Aga for the summer months, as a solar hot water system will provide your hot water. It is important to choose the system that best meets your needs and the following sections are designed to demystify the technology for you.
Over 70% of the average household's energy use goes into space and water heating, so a source of free hot water to use instead of commercial energy can make a dramatic financial saving. Solar Water Heating is the renewable technology of choice for most UK households as it offers a quicker payback (7-15 years for an average household) than Photovoltaics (20-30 years) and the advantage that there is already an established network of installers. More immediate financial impact on your energy budget can achieved through energy saving measures such as loft and cavity wall insulation that typically pay for themselves in 1- 3 years.
However solar water heating does require plumbing and heating expertise to size, install and balance effectively, not typically suitable for the average DIYer. When choosing an installer look for companies with recognised plumbing and heating certification such as CORGI, IPHE or APHC and experience in installing solar systems.
Solar Water Heating uses the radiation from the sun to heat water in a panel often sited on the roof which in turn can supply that heat as hot water or to a central heating system. Unfortunately the demands on your central heating system are at their highest when the sun is weakest so a solar heating system will only contribute to part of your heating energy requirements.
The positive side to the strength of the sun in summer is that it is the peak demand for swimming pools, static caravans and holiday lets.
If the system has been sized correctly, it can provide at least 40-60% of all your hot water requirements throughout the year. The average domestic system reduces carbon dioxide emissions by around 400kg per year.
Solar Water Heating should not be confused with generating electricity from the sun or Photovoltaics (PV) in which solar power is used to directly generate electricity which can be used in the home or fed into the National Grid. Some suppliers are now offering to site a PV panel next to a solar panel. This will generate electricity that can be used to power the solar heating pump.
Solar panels should be sited on a south-facing pitched roof, free of shade, at an angle of between 20 and 50 degrees, or may be mounted on an angled frame on the ground or on a flat roof. The typical domestic installation requires 2 - 5 square metres of roof area and you may also need space to locate an additional water cylinder if required.
Solar hot water - introduction
The principle of operation of a solar hot water system is quite simple.
A heat transfer liquid, usually a water/glycol mix, passes through a solar panel (or collector) and is heated by the sun; to give you an idea of how hot the heat transfer liquid gets, it is pressurised to 4 times atmospheric pressure to prevent it boiling (i.e. 100°C)!!.
If the temperature in the panel is above that in the hot water cylinder, the pump switches on to transfer the heat into one of the coils with the twin-coil hot water cylinder. If the solar hot water system has heated the water, then when the alternative heating source is timed to come on it will automatically sense that the water is already hot enough and not switch on.
Conversely, if there hasn't been enough solar heating then the alternative water heating system will switch on automatically as programmed.
Solar Collectors - Flat Plate or Evacuated Tube?
Solar collectors are currently available in two types; Flat Plate Collectors and Evacuated Tube Collectors.
Evacuated tube collectors have evacuated tubes each with a liquid filled copper conductor inside. As the liquid heats up it rises to the top of the tube where the heat is transferred in a manifold to the water from the cylinder.
In flat plate collectors the water passes through the whole plate where it is heated before returning to the cylinder. Flat plate collectors can more easily be integrated into the roof fabric and tend to have a lower profile than evacuated tubes.
Each system has its advantages in terms of price, efficiency and aesthetics. In general, evacuated tube collectors are more efficient and more expensive. A qualified heating installer may supply both plate types but will be able to advise on the appropriate technology for your project.
Planning
In July 2006 the Housing Minister, Yvette Cooper announced that from next year, changes to planning laws will allow householders to convert garages, build extensions, install solar panels and wind turbines - as long as they do not impact on neighbours.
At the moment planning consent is required if the work exceeds the 15% rule or if the building is listed or in a conservation area, National Park, AONB etc.
The government's Planning Portal website gives guidance on planning for domestic renewable projects. A link to it can be found in government departments.
Grants
Grants are available locally and nationally to offset part of the £2000 - £5000 typical cost of a domestic solar heating system.
The government's Low Carbon Buildings Programme will provide a grant of up to £400 for a new domestic solar heating system , (in Scotland the grant rate is 30% of the system price up to a maximum of £4,000), but before awarding a grant, as a householder, you must demonstrate that you are not wasting energy elsewhere in your home and have taken measures such as installing loft insulation, cavity wall insulation, low energy light bulbs and room thermostat/timer controls for your central heating.
Local grants are often also available. For example, in London the Solar for London programme provides discounts on solar heating components of up to £1500 provided that the installation is undertaken by an approved supplier. Your system installer will be able to advise of grants available in your area.