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.

Estimating Power Output

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

http://pvoutput.org
http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php

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.

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. This solar energy calculator gives you a good indication of how efficient an installation will be.

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."

Configuration

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.

Tilting Panels

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 10% (in winter) to 40% (in summer) more energy than fixed panels. This is a huge increase.

Alternative Panels

http://www.solarcentury.co.uk/homes/about-solar/c21e-solar-tiles-and-slates/