Photovoltaic Panels

The simple truth is that large-scale solar electric generation is still two to three times more expensive than burning fossil fuels. On the other hand, this argument is too simplistic to leave it at that. The cost of photovoltaic electricity generation is not reason enough to not do it but, you have to be careful about technology that double or triples the cost of electricity to end consumers.

Research and technology advances continue to lower the costs whilst the discovery, extraction and refinement costs of fossil fuels continute to rise. Tariffs on emissions of greenhouse gases will essentially level the playing field in the not so distant future.

Solar panels are essentially a case containing a number of solar cells.

Solar cells have a limited lifetime and their output gradually fades over time. The life span is measured to the poiint at which the output has dropped to 75% of their rated output.

This is a good video for an overview of solar PV power generation:

Estimating Power Output

There are a number of sites that help you estimate the likely power output for your location:

Purchase

The best way to install solar panels is by purchasing them outright and realising all the benefits yourself. This requires a large up-front investment though.

There are a lot of companies currently offering deals, where you rent out your roof and they own and install the panels for you, sharing the savings with the house owner. There are downsides to this approach though. The main one is that you have to enter into a long (typically 25 year) contract and pay for the removal of the panels if you back out before the contract period is up. As shown by this Guardian article, this can be a problem when selling a property or getting a mortgage.

Costs

With the Government reducing the 'feed in tariff' (FIT) in 2012, the cost of solar panel installations has dropped, to match the longer 'return times'. It is possible to an installation that will produce more than 22KWh on a good sunny day in England for about £7000 (July 2012).

Installation

To gain the most benefit from your solar panels, it is essential that they are installed at the optiumum angle for your latitude and face in the right direction. The links above can help provide guidance on this.

If your house is on a flat, open location, then conventional wisdom suggests aligning the panels north and inclining them at a tilt equal to your latitude. This roughly provides the best year-round collection.

If your house has a hill or building blocking the morning sunlight, then it makes more sense to align the panels in a more westerly direction, to improve the energy conversion. You would do the opposite to allow for any obstruction to the west.

With the government planning to reduce the 'feed in' tariff in 2012, there have been a lot of people rushing to fit panels with little consideration for the location and efficiency. In our local area, there are lots on panels installed on west facing roofs.

It is important that the installed panels are not subject to shade from chimney stacks and other objects. Even partial shade will have an impact on the whole PV array.

"The reduction in power from shading half of one cell is equivalent to removing a cell active area 36 times the shadow's actual size."

"One bird, one truck of dirt, one flowering tree can destroy your solar production, and you would not know for a long time."

"Welcome to the Christmas Tree Effect: Hurt the panel a little, hurt production a lot. It is amazing how many people put up solar for great reasons, but really do not watch their systems. As a result, a lot of people lose a lot of money because many, many systems are not producing the power its owners were promised. And few know."

There is a good guide on http://www.beenergysmart.co.uk/783/questions-to-ask-your-solar-pv-supplier/ by http://www.beenergysmart.co.uk.

Maintenance

Most panels have self-cleaning glass but, PV panels do benefit from being cleaned as Google have shown.

Solar panels are attached via frames that are solidly fixed to the roof trusses. This provides a good degree of protection from high winds. The site survey should include an inspection of the roof structure to see if it is suitable for the fitting of solar panels.

Snow covered solar panels
AllEarth Renewables produce the NOT DEFINEDhttp://homeenergypros.lbl.gov/m/blogpost?id=6069565%3ABlogPost%3A99170" rel="nofollow" class="link" target="_blank">What happens when you get snow on solar panels?

Sun Tracking

Tilting Panels

Installing panels that tilt can make a significant different to the power they generate over the course ofa year. Tilting panels are much simpler than panels that fully track the sun. Typically, the tilting is done manually and changes are made just a few times each year, optimising the tilt angle during the seasons.

This is a good article on adjustable/tilting solar panels.

Heliostats

Heliostats are devices that track the sun and keep solar panels facing the sun for maximum power generation and efficiency. The downside of these devices are that they need a lot of room, are quite complex and subject to failure. The obvious advantage is that panels that track the movement of the sun throughout the day can receive approximately 10% more energy in the winter than fixed panels and around 40% more in the summer. This is a huge increase.

Heliostats that track the sun from East to West only are called 'single axis' trackers. Those that also track it in a vertical direction are called 'dual axis' trackers.

AllSun Tracker Series 20
AllEarth Renewables produce the AllSun Tracker Series 20, which is a good example of sun-tracking technology. Devices like this claim to increase energy output by around 35% to 45% by ensuring optimum alignment of the panels with the sun throughout the day.

There is a great article on the Home Power website on sun trackers.

Passive sun tracker
This single axis, passive tracker uses the heat from sunlight to vaporize liquid Freon contained in containers mounted on each side of the tracker. As the gas expands, it forces the liquid into the container on the other side of the tracker and the change in balance causes it to rotate.

Efficiency

As the technology improves, so does the efficiency of the solar panels. This can make them much more cost effective by reducung the costs and size of installation required.

Empa thin film solar cell
In January 2013, Empa (the Swiss Federal Laboratories for Materials Science and Technology) claimed to have set a new efficiency record for thin-film copper indium gallium (di)selenid (or CIGS) based solar cells on flexible polymer foils, reaching an efficiency of 20.4%.

Flexible thin film solar cells also have the advantages of increased flexibility and a more cost-effective roll-to-roll manufacturing process.

Alternative Solar Panel Designs

V3 Solar's Spin Cells
V3 Solar's Spin Cells use an arrangement of cone shaped solar cells to generate more electricity for a given area.

Roof tiles
Photovoltaic roof tiles and slates provide a more subtle way to generate electricity but, make much more sense when planned into a new build or project to repair/replace an existing roof.

Manufacturers

Sharp Solar

Sharp Solar produce a wide range of PV cells, including their thin-film silicon cells which are transparent to visible light.

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