Renewable Energy Solar Panels and Wind Turbines

The “feed-in tariff” or “clean energy cashback” for renewable electricity started in April 2010. It is the new support mechanism for renewable energy technologies.

There are three elements to the new feed-in-tariff:

• A Generation tariff: a payment for every unit of electricity (kWh) generated by the system
• An Export tariff: an additional payment for every kWh exported to the grid
• Free on-site use of any electricity generated by the system which will reduce electricity bills

Details of the tariff levels can be found here.

In April 2011, the “Renewable Heat Incentive” will be introduced for solar water heating and air-source heat pumps and other heat producing renewable energy technologies. The RHI is currently under consultation – the consultation document can be found here.

Government grants are no longer available for renewable energy technologies.  For electricity generating technologies (solar PV and wind) grants have now been superseded by the feed-in-tariff.

Some other organisations do still provide grants for schools, charities and community groups.

For non-domestic properties, planning permission is generally required for all the technologies we offer. For larger systems, we do offer a planning service.

For domestic properties, a solar PV or solar water heating system will generally not require planning permission, unless you are in a conservation area, AONB or National Park, or the system is to be installed on a listed building. However, it is always advisable to check with your local planning authority before proceeding.

A wind turbine or an air-source heat pump will usually need planning permission. We can provide a ‘planning pack’ which will provide all the information required by the planning authority in order to progress a planning application.

We generally only out carry a site visit once we have provided initial advice and budget prices and concluded that it is likely that an installation will be feasible and you are keen to proceed.

Generally for domestic customers, we will ask you to complete our site assessment form which will give us some basic information about what you are looking for. We are often able to provide quotations for domestic solar PV systems on the basis of the information you provide.

For larger solar PV systems and for wind turbines a site visit is usually necessary, unless we are quoting from architects drawings.

We will advise you whether or not your site is suitable for a solar PV system. We will explain where we would propose to site the system, the electricity output and the likely revenues under the Feed-in-Tariff.

If your site is not suitable for a PV system, we will advise you of this: we would never try to sell a system that is inappropriate. We do not believe it is in our interests to do this, as we need satisfied customers in order to stay in business.

In order to give additional reassurance to domestic customers regarding our professional conduct, we are members of the Renewable Energy Association’s consumer assurance scheme ‘REAL’ – please see the Real Assurance Scheme for more details.

Most PV systems are mounted on a roof, although they can also be ground-mounted. South facing is the optimum orientation, but a system can be mounted facing anywhere from East to West. The optimum angle for a system is 30 to 45 degrees from the horizontal in order to maximise output; however an angle from 5 to 60 degrees is possible, with a small reduction in output.

Shading of only a small part of a solar PV system will significantly reduce its output. This is due to the electrical connections being in series so that shading of a small part can reduce the output from the whole system.

If you are a domestic customer, we will ask you to complete a site assessment form which will enable us to advise you on the best location for a PV system. Our smallest Suntricity system (1.3 kWp) generally requires at least 10m² of un-shaded, southerly facing roof area.

Solar PV systems can be mounted on almost all roof types e.g. tiled, slates, flat roofs, metal roofs. We will complete a structural assessment of the roof to ensure it can take the weight of the PV system. On new-build projects, we will provide full details of the weight and fixings of the system to the structural engineers.

Where the installation is on a flat roof we will usually supply a mounting system which ensures that the solar PV modules are mounted at an angle to maximise their energy production. We will generally require full details of the roof so that we can design a means of attaching the solar PV system.

Loading can sometimes be an issue with flat roofs or metal roofs – our structural engineers will undertake a full structural assessment if necessary.

A solar PV system facing due south, installed at an angle of 30 degrees from the horizontal and unshaded, can be expected to produce between 700 and 950 kWh/ kWp/year in the UK. Under the Micro-generation Certification Scheme, we are required to estimate performance using an average of figure of 800 kWh/ kWp/year. This means that a 1 kWp solar PV system will produce 800 units (kWh) of electricity each year and a 2 kWp system will produce 1,600 units (kWh).

A typical, 3 bedroom, UK house built to 2006 Building Regulations will use 3000-4000 units of electricity per year. A 2 kWp PV system will produce roughly half of this. However, electricity consumption can be reduced via energy saving methods so that a 2 kWp PV system should supply a higher proportion of your electricity.

A budget fully-installed price for our Suntricity 2.1 kWp PV system (suitable for a domestic property) is £8,500 ex VAT. Costs per kW can reduce substantially for larger systems or for multiple installations. However, prices are continuing to fall, so it is always worth asking for a quote.

Solar PV systems are extremely reliable. PV modules come with a 25 year warranty and have no moving parts so that failures are extremely rare. The inverters for solar PV systems are supplied with a 5 year warranty.

Photon Energy also provides a 5 year workmanship warranty on all solar PV our installations.

There are three main types of solar PV module:

• Mono-crystalline silicon technology is the most efficient and most expensive type of module. Module efficiency is typically around 14.5%. These are generally used if there are space restrictions and a given energy production is required.
• Multi-crystalline silicon has a slightly lower efficiency, typically around 13.5%, than mono-crystalline silicon and is slightly cheaper. The technologies are essentially the same, but the photovoltaic cells are made in a different way. Most PV modules installed in the UK are of multi-crystalline silicon technology. Generally the difference in efficiency of these technologies is too small to affect prices, it just means that multi-crystalline silicon systems occupy the same area, use the same components but have a very slightly lower power rating.
• Thin film technology – the most common being amorphous silicon. It is of a much lower efficiency that the crystalline silicon technologies, typically around 8%, although the PV modules are cheaper. However, because of the much lower efficiency, the price for a given system size is often higher than for one using crystalline silicon, as more mounting structures, cabling, and labour are required for installation. There are other thin film technologies, such as Cadmium Telluride and Copper Indium Disellenide, but these are also of lower efficiency, are not produced in any significant quantity and there are potential environmental implications associated with their disposal or re-cycling.

Some PV modules combine a thin-film of amorphous silicon with mono-crystalline cells. These modules are of a slightly higher efficiency (16%) and again require less area for a given power output, but cost considerably more than conventional multi- or mono-crystalline silicon.

For all the module technologies above, the energy output per unit power is the same. This means that a 10 kWp system will generate approximately 8 MWh/year, no matter what the module technology. The difference between the systems is the amount of space they occupy.

There is much talk of the next generation of PV technology and most of it is media hype. All the technologies manufactured today will remain dominant for years to come. Most improvements are incremental – small improvements to existing manufacturing processes. 

There is a great deal of laboratory based research into alternative technologies such as photoelectro-chemical cells, photo-synthetic cells, organic polymers, quantum well devices. Whilst these are interesting areas of academic research, they are decades away from large-scale, volume production.

Photon Energy will supply and install a complete system that can be linked into the existing electricity supply in your building, no additional work will be required to provide a fully operational system. Generally, no modification of the existing electrical system is required, we simply need a spare way in your fusebox to connect into (and if this is not available, we will install the necessary additional equipment).

Permission is required from the local Distribution Network Operator (DNO) to connect the solar PV to the electrical network. Photon Energy will take care of this application and permission to connect is automatic for small-scale, domestic sized systems.

Connecting larger systems to the electricity networks is an application process and may require a network study to be carried out by the DNO. We will advise if we think there may be an issue with connection, and liaise with the DNO early on in a project to resolve any issues that arise.

Most systems that we install are grid connected. This means that if the PV system is not generating sufficient electricity for your needs, the additional requirement is automatically drawn from the grid. If you generate more electricity than you are using, this is automatically exported to the electricity grid.

For off-grid systems, the system will be designed with batteries to store any excess electricity generated. The batteries will be sized to provide sufficient storage to ensure that there should always be electricity when needed (or a diesel back-up may be used).

When there is a power cut, a solar PV system will immediately disconnect from the electricity system and cease to provide power. This is a safety requirement so that injuries do not occur to those working on the networks. Unfortunately, due to safety regulations, a solar PV or wind system cannot provide power during a power cut.

Solar PV modules generally have a 25-year warranty and maintenance requirements are very low. Inverters carry a 5-year warranty and manufacturers state a 20-year lifetime.

Cleaning of the modules is not normally necessary as they will generally be cleaned by rainfall. However, if they are mounted at a shallow pitch or in a dirty location, cleaning may be required. The remainder of a PV system, including the inverter, is usually located in the loft of a house or in a plant room and therefore can be accessed in case of a fault. We generally recommend a 5-year check for domestic solar PV systems. Larger systems should either be continuously monitored and/or checked annually.

Solar PV systems generate electricity, not hot water. Electricity can be used to heat water e.g. via an immersion heater. However, if you want a system that heats water directly you need a solar water heating system, not a solar PV system.

A small wind turbine should be at least 50 metres from any obstruction or buildings, a large wind turbine up to 500 metres. As the prevailing wind direction is generally from the south west, it is important that the land is open to this side of the wind turbine.

Most of the wind turbines Photon Energy installs are ground mounted. Ground mounted small wind turbines are a straightforward, well proven technology which we are confident to recommend to any customer with a suitable site. Building mounting of wind turbines is far more complex, and will only be suitable in certain situations.

Although Photon Energy has substantial experience of installing wind turbines on buildings, we generally do not encourage this type of installation.

We do not offer small, domestic sized wind turbines for building mounting. Independent tests have questioned the viability of this technology (see Warwick Wind Trials)

The output from a wind turbine is hard to predict and is very dependent on local climatic conditions and topography.  We will always provide an estimate of the annual generation of a turbine with our quotation as required under the Micro-generation Certification Scheme. In order to estimate the output, we use data from the NOABL wind speed database. As a general guide, if the database estimates your wind speed to be lower than 5 m/s, you should consider an alternative technology.

We will never be able to guarantee the output from a wind turbine, and will not be able to give an accurate estimate if wind monitoring is not undertaken prior to installation of the turbine.  However, we will advise whether your site is suitable.

A budget installed cost for a 6 kW wind turbine is £24,000 ex VAT.  (Note that this cost excludes the ground works as these will vary substantially between sites, depending on ground conditions.)

Wind turbines are a reliable technology and come with a 5-year warranty, and the expected lifetime of most turbines is 20 years.  The inverters for wind turbines are supplied with a 5-year warranty.

Photon Energy also provide a 5-year workmanship warranty on our installations.

Most conventional wind turbines are horizontal axis turbines (HAWT) and are a well proven, reliable technology. Their main disadvantage is that have to “yaw” into the wind to maximise their output and they generally perform better in constant, smooth, non-turbulent wind.

The attraction of vertical axis wind turbines (VAWT) is that they should perfume better in turbulent, gusty winds. Early VAWTs of the Savonius and Darrieus types have become fashionable recently, as they were in the 1980s. However, the problems with them are still the same as they were 30 years ago and prior to that. Many VAWTs are not self –starting, and they tend be of very heavy design in order to withstand the stresses imposed on them. More recent designs, such as the “egg-whisk” type, have reduced the stresses but still require electric starting and regulating. Some types will actually consume more electricity in starting/regulating themselves than they actually generate. They also tend to be around twice the 50% more expensive than a similarly rated HAWT.

Photon Energy will supply and install a complete system that can be linked into the existing electricity supply; no additional work will be required to provide a fully functioning system. Generally, no modification of the existing electrical system is required, - we simply need a spare way in the distribution board to connect into (and if this is not available, we will install the necessary additional equipment).

Permission is required from the local Distribution Network Operator (DNO) to connect a wind turbine to the electrical network. However, Photon Energy will take care of this application and permission to connect is automatic for small-scale systems. For larger scale systems we will advise if we think there may be an issue with connection, and liaise with the DNO early on in a project to resolve any issues that arise.

Most systems that we install are grid connected. This means that if the wind turbine is not generating sufficient electricity, the additional requirement is automatically drawn from the grid electricity system. If the turbine generates excess electricity, this is automatically exported to the electricity grid.

For off-grid systems, the system will be designed with batteries to store any excess electricity generated.  The batteries will be sized to provide sufficient storage to ensure that there should always be electricity when needed (or a diesel back-up may be used).

When there is a power cut, your wind turbine will immediately disconnect from the electricity network to provide power. This is a safety requirement so that injuries do not occur to those working on the grid.  Unfortunately, due to safety regulations, a wind turbine cannot provide power during a power cut, unless it is installed with specialist equipment.

Wind turbines have moving parts and therefore do require annual maintenance in order to keep them in good working order. Photon Energy can carry out the maintenance, either on a one-off basis or as part of a maintenance contract.

Maintenance must be carried out by an authorised company. Failure to carry out regular maintenance by an approved company will invalidate any warranty.

Inverters carry a 5-year warranty and manufacturers’ state a 20-year lifetime, therefore very occasional replacement / maintenance can be expected.

When there is a power cut, fluid in the collector circuit will not circulate. This is not usually a problem for a day or two.

We will advise you whether or not your site is suitable for solar water heating system. We will explain where we would propose to site the system and the annual energy output.

If your site is not suitable, we will advise you of this: we would never try to sell a system that is inappropriate.

Most solar water heating systems are roof mounted, although they can also be ground-mounted.

South-facing is the optimum orientation, but a system can be mounted facing anywhere from East to West. The optimum angle for a system is 30 to 45 degrees from the horizontal in order to maximise output, however an angle from 5 to 60 degrees is possible, with a small reduction in output. Systems should be unshaded as much as possible, although performance is not as drastically affected by shading as for a solar PV system.

Solar water heating systems can be mounted on almost all roof types e.g. tiled, slates, flat roofs, metal roofs.  We will complete a structural assessment of the roof to ensure it can take the weight of the collector. On new-build projects, we will provide full details of the weight and fixings of the system to the structural engineers. Where the installation is to be on a flat roof we will usually supply a mounting system which ensures that the solar collectors are mounted at an angle to maximise their energy production.  We will generally require full details of the roof so that we can design a means of attaching the solar collectors.

Loading can sometimes be an issue with flat roofs or metal roofs – our structural engineers will undertake a full structural assessment if necessary.

A solar thermal system (i.e., facing south, installed at an angle of 30 degrees) should be sized to provide between 60% and 70% of the annual hot water requirement for a home. Installing a larger system will mean that it “over produces” in summer. As a rule of thumb, you should install 1m² to 1.5m² of collector area per person.

A budget price for a fully installed solar water heating system with a 2.2m² flat plate collector (including a replacement hot water cylinder) is in the order of £3,800 (excluding VAT and scaffolding). 

An equivalent system using 20 evacuated tubes and a new cylinder would cost in the order of £4,400 (excluding VAT and scaffolding).

Prices reduce significantly for multiple installations or larger systems.

Running costs are very low – just the cost of running a circulating pump, although some direct systems provide a small PV panel to operate the pump.

Annual savings are currently in the order of £50 - £90 per year depending on the fuel (gas or electricity) being displaced. The forthcoming Renewable Heat Incentive will significantly increase savings.

Solar thermal systems are extremely reliable.  The collectors typically come with a 5 year warranty, and cylinders with a 25 year warranty.

Photon Energy also provides a 2 year workmanship warranty on all our solar water heating installations.

There are two main types of solar thermal collector – evacuated tubes and flat plate collectors.

• Flat plate collectors consist of a black absorber plate to which a copper pipe is bonded to transfer heat into the fluid in the collector circuit. The absorber is usually framed in a box with a glass or perspex cover to reduce convective heat losses. The absorber is usually framed in a box with a glass or Perspex cover to reduce convective heat losses. The fluid in the collector circuit is then used to heat the water in a hot water cylinder. Generally flat plate collectors are slightly cheaper than evacuated tube systems.
• Evacuated tubes consist of a narrow strip of black coated copper bonded to a copper tube. In the tube, a fluid is evaporated and transfers the heat it absorbs to the collector circuit, before condensing again in a continuous cycle. The absorber assembly is then enclosed in an evacuated glass tube. Evacuated tubes are possibly slightly more efficient than flat plate collectors but are slightly more expensive.

A study undertaken by an independent monitoring company on behalf of the former Department of Trade and Industry found that in side-by-side tests, with identical (controlled) draw off patterns, there was no significant difference in the performance of flat plate collectors and evacuated tubes. A copy of the study is available here.

A direct system takes the water from the hot water cylinder and runs it through the solar collector and heats it directly. These systems are less common than indirect systems and can suffer from calcification in hard water areas. They can suffer from damage if the water in the collector freezes in very cold weather, although some systems drain the water from the collector at night (drain-back systems). The main advantage with a direct system is that they can mean that a new HW cylinder is not required.

An indirect system has a separate circuit for the collector fluid, which is a mixture of water and antifreeze. Indirect systems are the most commonly installed in the UK, but they do need a new HW cylinder to be installed.

We only install indirect systems.

Most solar water heating systems can be used with either a gas boiler or an electric immersion heater as a back-up supply in winter.  Immersion heaters should be set such that they do not heat the hot water in preference to the solar water heater.

If the solar water heater is not providing enough hot water (at night or in winter), this is topped up by the back-up supply which should always be installed. The back-up can be a gas boiler, immersion heater or even an air source heat pump. Back-up heaters should operate only when the hot water needs cannot be met by the solar system.

In summer, or when the property is empty, water will still be heated, but will cool slightly overnight. It is important to ensure the electricity supply is not switched off so that the collector fluid still circulates in the system allowing heat to be taken from the collector and “dumped” in the cylinder. In very extreme cases, the collector fluid may boil and escape through a pressure relief valve. The system may need re-pressurising if this is allowed to happen regularly.

When there is a power cut, fluid in the collector circuit will not circulate. This is not usually a problem for a day or two.

Maintenance requirements are very low – the pressure gauge should be checked periodically, and direct systems may suffer from calcification in hard water areas.  

Cleaning of the collectors is not normally necessary as they will generally be cleaned by rainfall. However, if they are mounted at a shallow pitch or in a dirty location, cleaning may be required.

We generally recommend an annual check for solar water heating systems. Larger systems should certainly be checked annually.

Solar thermal systems heat water and do not generate electricity. If you want a system that generates electricity you want a solar PV system, not a solar water heating system.