FAQ's
How much energy do I need?Does it work in the UK?
Isn't solar power expensive?
What maintenance and cleaning do the systems need?
Do you sell hot water systems as well as solar electric (PV) systems?
Do solar installations need batteries?
What happens if there is a power cut?
What are the effects of shade?
What sort of projects are suitable for solar installations?
How can the energy outputs of the different products be estimated?
How is the angle of optimum panel inclination found for different latitudes within the UK?
How do the panels perform at different angles and orientations?
What are the main detailing points to consider?
How can the energy benefits of the pv cells be maximised?
What are the relevant codes of practice and articles of legislation?
What are the Health and Safety issues?
How can PV glass laminates and flexible thin film PV be used architecturally?
How are PV cells affected by soiling?
What are the lifetimes of PV products?
Doesn't the glazed front reflect light away from solar photovoltaic (PV) modules?
How much energy do I need?
According to the Energy Saving Trust, the average 3 bedroom house consumes 3,300 units of electricity (kWh) a year (cooking and heating using non electric supply). However, we always recommend that you look at your last few bills or call your electricity supplier to find out how many units you consume, you can then compare this to the output of the system we recommend.
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Does it work in the UK?
Photovoltaic cells do not need to be in direct sunlight to work, and will generate electricity even on cloudy days. The brighter the day the greater the energy generated. Solar thermal systems will supply hot water on bright days in summer and winter, typically delivering over 60% of hot water demand over the course of a year.
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Isn't solar power expensive?
A solar installation adds as little as 4% to the build cost of an average three bedroom home, but over 10%to its final value when sold. It also helps ?future proof? a home against rising fuel prices making properties doubly attractive to price conscious house buyers; as fuel prices continue to rise, energy efficient renewably powered homes will continue to sell at a premium.
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What maintenance and cleaning do the systems need?
Solar photovoltaic systems are silent in operation, have no moving parts and require no maintenance. Solar thermal systems have a few moving parts (inside the pump) but these are virtually maintenance free, you may need to replace the anti-freeze in a solar thermal system after about five years. Most of the time the rain will keep the modules clean. However, a build up of dirt can affect system performance. The modules can be cleaned with either a hose or, if possible, soapy water and a non abrasive brush.
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Do you sell hot water systems as well as solar electric (PV) systems?
Yes, we sell both types of solar systems: Solar photovoltaic (PV) systems which generates electricity from daylight and solar thermal systems to heat water.
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Do solar installations need batteries?
No local battery storage is required as the systems connect to the local electricity supply; in case of BIPV systems installations.
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What happens if there is a power cut?
Our photovoltaic systems for homes are entirely grid connected. If there is a power cut your system is automatically switched off. This is a safety measure designed to stop electricity leaking on to the national grid and to protect individuals who may be working to restore the power supply.
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What are the effects of shade?
Shading is critical. Minor shading can result in significant loss of energy. This is because the cell with the lowest illumination determines the operating current of the series string in which it is connected. Many modern modules use bypass diodes to minimise shade effects; but these effects must still be considered, preferably in the first stages of building design. Watch for landscaping, trees and even handrails. If shading is unavoidable, or poor light is expected on a regular basis, the best types of PV to use are amorphous thin-film, or hybrid (mixing monocrystalline and amorphous technology).
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What sort of projects are suitable for solar installations?
A project with a brief incorporating social and technical innovation is an ideal candidate for building-integrated PV (BIPV). The most important aspect to consider is the location of the site. The solar installation must receive as much light as possible. Shadows cast by tall trees and neighbouring buildings must be kept in mind during the design process. The best location for solar PV is obviously on the south-facing roof or side of a building.
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How can the energy outputs of the different products be estimated?
The following energy outputs can be used as a rough rule of thumb for the UK (assuming a reasonable tilt, orientation and system efficiency). 1m2 crystalline array will provide a useful output of 90-110 kWh per year.1m2 triple-junction thin film array will provide a useful output of 50-60 kWh per year.
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How is the angle of optimum panel inclination found for different latitudes within the UK?
The maximum total annual solar radiation is usually at an orientation due south and at a tilt from the horizontal equal to the latitude of the site minus approximately 20 degrees. For example 30 degrees is an optimal tilt in Southern England, increasing to almost 40 degrees in Northern Scotland.
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How do the panels perform at different angles and orientations?
If the optimum angle is not achievable, over 90% of the maximum annual energy can still be achieved at 10 degree and 50 degree tilts.South-facing vertical fs generate around 70% of the maximum.
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What are the main detailing points to consider?
The main points to remember are:
- Method of fixing/ integration into the fabric must be detailed.
- Ensure that the fixing does not cover or shade any part of the PV cells.
- PV laminates are often constructed with only a narrow border.
- The fixing must allow for thermal expansion without breaking the glass.
- Weather sealing involves standard construction practices but all materials must be suitable for the temperatures likely to be met (i.e. temperatures at the back of the modules can rise to 80? if they are poorly ventilated or higher if they are directly insulated).
- The mounting option must allow for safe maintenance and possible replacement of individual modules. The life of the support structure must be at least that of the PV array. The preferred materials are aluminium, stainless steel or glass-fibre. Protection from corrosion is important especially as residual currents may be present.
- Wind loading
- Any extra weight
- How and where to run electrical wiring ( this may penetrate the waterproof skin)
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How can the energy benefits of the PV cells be maximised?
Orientation, shading and the temperature of the PV elements all impact on their output and must be considered at the design stage. Of course, the more energy efficient the building, the greater the overall benefit of the PV cells. Some PV products have now been designed to provide thermal insulation as well as electricity - eg flat roof systems and solar metal roofing systems that include insulation lass.
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What are the relevant codes of practice and articles of legislation?
- British Standards
- BS EN 61215
- BS EN 61646
- The Electric Supply Regulations 1988
- The Building Regulations 1991 (and amendments)
- The Construction (Design and Management) Regulations 1994
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What are the Health and Safety issues?
- The main issues to be aware of when appraising PV for CDM are:
- Weight: Modules may be heavy with some exceeding 50kg.
- Toxicity: No PV module releases sufficient toxic materials to cause any harm during installation or maintenance. A small proportion of PV contains cadmium, the oxides of which are toxic in very small doses. Some of these may release toxic dust if crushed during disposal. None of the PV products supplied by TDH Visions contain any cadmium.
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How can PV glass laminates and flexible thin film PV be used architecturally?
PV glass laminates are attractive and well suited to facades and transparent roof tops. They can be fitted to standard curtain walling structures and are suitable for any application where glass is used, as long as there is a reasonable level of light present. Low emissivity glass can be used to give additional thermal insulation benefits, or a PVB laminate can be used for the extra strength required by a roof top. Thin-film PV is durable and flexible and is encased in a water-proof, self-cleaning polymer. It can be used in shingle form for roofing or in more unusual designs that exploit its flexibility.
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How are PV cells affected by soiling?
The degree of soiling will depend on the location but usually dust accumulation and self-cleaning reach a steady state after a few weeks if the array tilt is at least 15 degrees. In extreme cases dust may cause a power reduction of about 10%. At low tilts horizontal glazing bars can trap debris which could lead to shading of part of the array. The design of the system should aim to minimise uneven soiling.
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What are the lifetimes of PV products?
Solar modules have a manufacturers warranty of 25 years and a working lifetime of 40 years and beyond. Modules of all types usually have a twenty year warranty, as do most thin-film integrated products. Crystalline PV slates and PV glass laminates usually have a ten year warranty. These times are only a rough guide and should be checked for each specific product. l a solar system.
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Doesn't the glazed front reflect light away from solar photovoltaic (PV) modules?
Solar PV modules constructed with a glass front have two characteristics that reduce light reflection. In order to optimise electrical yield the glass is treated with an anti-reflective coating which greatly increases the transmittance through the glass so to maximise the amount of light reaching the solar cells. Secondly the outer face of the glass has a slight granular textured. The result is a matt like finish rather than a mirrored, again this is actually intended to maximise yield. These two characteristics greatly reduce reflection from the glazed front face of solar PV modules when compared with conventional glazing.
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