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Electricity Generation

Renewable electricity is most commonly generated using Photovoltaic panels, Wind turbines or Hydro electric turbines. Hybrid panels are solar panels which can generate electricity and heat within the same panel. The easiest and most common technology for smaller generating systems is Photovoltaic.

Photovoltaic

Photovoltaic (PV) panels or PV solar panels as they are more commonly known, use the energy from the sun to generate electricity with almost no waste and no emissions. This can then be used to run household appliances and lighting. The system is installed and connected to the property’s mains power system.

PV panels can come in a wide variety of shapes and sizes and certain colours of frames and cells. It is important to ensure that they are well positioned to get the maximum radiation and that the roof condition is properly checked to ensure it can take the load. Any roof that is likely to require recovering in the next 20 years is most sensibly refurbished as part of the installation work and the careful fitting and weatherproofing of the bracketry is critical to ensure that you don’t suffer from leaks in the future.

Many people prefer the look of black framed and backed panels for fitting on their roofs in visible area in which case we will also specify black fittings and, if required, fascias.

Particularly on new build projects, we can also specify integrated panels which can have a very low profile when compared to the more usual on-roof systems which are typically 150mm (6 inches) above the roof.

Flat roofs can be very suitable for PV panels and in this case they are normally mounted on special triangular frames. Panels can also be very cost effectively mounted on metal sheeted farm buildings and industrial style roofs.

Most, but not all PV installations, do not require planning permission because they are covered by a Planning Development Right (PDR).

It is always important to inform your insurance and mortgage companies of any planned PV installation.

Description of a typical photovoltaic system

The two key components in the system are the photovoltaic panels and the inverter.

The panels converts light from the sun into DC electricity which varies in strength according to the intensity of sunlight. Photovoltaics is a well established solid state electronics technology which requires little maintenance over a long lifetime with only slow but gradual deterioration of performance over many years.

This varying DC current is then fed to the inverter which is a sophisticated and critically important electronic unit which converts the DC current into standard grid compatible AC current which is suitable for use in your home or for feeding back into the main electricity grid for sale to your electricity company. It is of particular concern to specify the correct inverter for the design of your system and configure it in the correct way.

These two components need to be carefully matched, with reference to the intensity of sunlight that is expected to fall on the panels, and any possible shading of the panels in order to ensure the optimum cost and efficiency of operation.

We always calculate the predicted performances of a system as part of any quotation that we submit.

Quality and Warranties.

While there are different characteristics between photovoltaic cell technologies (eg monocrystalline, polycrystalline, HIT, glass on glass etc), the differences are not significant enough to describe here, in this introductory note. One should be wary of any claims that one is better than the other. We would however explain our recommendations once we have understood the details of the site and the customer’s requirements. The more important consideration for most applications is the quality of ancillary components and the build quality of the panel.

There are a large number of PV panel manufacturers. These manufacturers give product warranties of typically 10 years on the physical build quality and warranties on the electrical output over typically 10 & 20 or 25 years. When considering a long term quality and reliability it is important to consider the a companiescompany’s reputation in the industry, and the length and experience of its manufacturing operation and the importance of its brand. We only recommend panels from well established manufacturers. We also give particular weight to the few well established companies which have their warranties backed up by third party insurance companies.

The inverter is a highly advanced piece of electronics and we only specify manufacturers with strong experience of making inverters and with products that can operate through a wide range of expected light conditions as well as having a high Euro efficiency (a standard test method which tests its efficiency throughout its operating range). Inverters have a lower expected life of up maybe 10-12 year due to the nature of electronic components. Most manufacturers offer a 5 year guarantee as standard and extended warranties can be purchased at an additional cost.

Wind Turbines

Whilst large scale industrial wind turbines are a well developed product that are commonly seen around the countryside, smaller turbines for use in domestic and small industrial situations are a more recent development with relatively few approved products available in the market. However in the last year more have come onto the market and there is a reasonable selection.

There are two important reasons why there are not so many small wind turbines: firstly because they are very dependent on having a good site with very little wind interruption and secondly because planning permission has often been difficult. Local authorities are however becoming more used to allowing such installations. A rule of thumb is that if there is an obstacle nearby then the turbine mast should be 2 x the height of the obstacle in height and 10 times that distance away from it - eg. a 7 m obstacle suggests a tower of 14m and the obstacle should be 70m away from the turbine.

We do not recommend very small systems for cost/benefit reasons and it is more usual to specify 6kW as a minimum size. The cost of the foundations and mast on which the turbine is placed can bear normally over half of the total costs.

However if you have a good site which is close to a suitable electricity supply point then these can be very effective and financially attractive investments.

Small Hydro Generators

Hydro generators use the water flow of a stream or river to turn a generator. Their financial return on investment is obviously very dependent on having a suitable site with adequate height and volume of running water and with an economically close connection to the electricity grid. An adequate flow rate throughout the year can often be a problem in order to ensure consistent generation. As the characteristics of the site ischaracteristics of the site are so important this makes this the most unusual of the microgeneration technologies.

The water can either be a low head (eg. height difference or fall of water) with a high volume or the more conventional arrangement of a reasonable volume and a good head. Depending on the site characteristics there are a range of different hydro generators that can be used including Archimedian screws, slow horizontal turbines and traditional impulse turbines.

If you have a good site then this is arguably the most reliable and long lasting type of electricity generation. The initial installation costs can often be high due to suitable sites not often having convenient access, but if you have a situation that might be suitable please get in touch.

Why not give us a call to see how you can benefit?