Faqs
1. What is solar energy?
Solar (or photovoltaic or "PV") energy is electrical energy produced when sunlight strikes a solar cell in a solar panel. The cell has an absorbing material (traditionally silicon, but now other cheaper and lighter alternates are under development) which absorbs the photons in sunlight, a process which knocks electrons loose from their atoms and excites them into flowing through the material to produce electricity.
2. Why solar roof?
The roof is a perfect location for a solar energy generation plant. It is an expanse of open space facing up to the sky. Moreover it is space you already own or control and which otherwise has no use apart from keeping the rain out. Thus by turning it into a solar generation pant you make something out of nothing - think of it as like owning an oil prospecting licence but with the oil already discovered, much more easily extracted, in an almost infinite supply and without the greenhouse gas side effects.
3. Why now?
The financial, political and technological climate has never been better - solar is about to take off!
On the financial side, oil and coal are finite and traded to ever increasing prices on firm increasing demand and unstable supply. Uranium costs have gone up many fold over the past few years and storing spent fuel is an expensive headache. Biofuels may be squeezed as pressures grow to devote crops to food production instead. The trend for non-renewable energy cost can only be upward.
Politically, fossil fuels are unpopular. They emit greenhouse gasses, which the EU has agreed should be cut by 20% from 1990 values by 2020, with renewable energies to form 20% of total energy by 2020.
However just as the twin forces of crippling escalating energy costs and the dangerous side effects of traditional sources of energy open up a void, the great scientific minds of this world step in to fill it with solutions destined to drive the cost of solar energy down to the point where some say within the next 7 years energy produced on your own roof will cost less than the energy which the public utilities can supply. Some components of solar are of course entirely free (and perfectly politically stable) - the sun for one, and your roof for another (you already own or control it and it has no other use). Of course you still have to pay for the panels, and it is here that the real innovations are coming through to make the difference. Traditionally the cell is made of silicon mounted on a glass backing. Silicon is expensive, and glass panels are cumbersome and expensive to mass produce. A number of companies are now starting to turn out new-style thin film cells made with machines like printing presses which apply layers of light absorbing materials such as CIGS onto thin and flexible backing – a simpler and more efficient production method which slashes production costs (some claim down to one tenth of traditional panels), as well as resulting in a more flexible product capable of easy installation and adaptable to many different surface types.
Hand in hand with technological ingenuity comes the ingenuity of financial engineers, who have devised financing products such as Power Purchasing Agreements (PPAs) by which companies provide turnkey installations which they own and run, and which the host roof owner has the option to buy on favourable terms in due course and meantime can enjoy the benefits of electricity at below market prices.
4. Where are people installing solar roofs and on what types of roof are they doing it?
Almost every week you can read a press release from major household names who have woken up to the advantages (financial and ecological) of the solar roof concept: Macy's, PepsiCo, Hewlett-Packard, Estee Lauder, Wal-Mart, Cadbury Schweppes, BT, Costco… and the list goes on. They are all turning their warehouse or retail or office roofs into solar power plants.
And time and time again those who have done it or helped facilitate it say: "Why are we wasting all that unused commercial roof top space?" Governor Schwarzenegger, launching a project in California in early 2008 to place 250 megawatts of advanced photovoltaic generating power on 65 million square feet of roofs of Southern Californian commercial buildings, said: "If commercial buildings started partnering with utilities to put this solar technology on their rooftops, it would set off a huge wave of renewable energy growth".
When Cadbury Schweppes formally put into operation the new rooftop solar system at their manufacturing plant in Blacktown, New South Wales, the regional director of BP Solar commented: "Like Blacktown, there are many other regions across Australia where literally vast fields of commercial roof space lie dormant . These roof tops could be turned into mini power stations allowing many more Australian businesses to produce emission free electricity at the very time of the day when energy prices are often at their peak."
And it is not just commercial roof tops. Warehouses, stores, factories, distribution centres and office blocks may be prime and obvious candidates, but there are many others – schools, municipal buildings (London City Hall has done it), libraries, hospitals, football stadiums and of course simple houses – a spectacular example being Colona Real Estate in Germany, which has a portfolio of 20,000 residential units on which it is installing rooftop solar panels.
5. Must the roof be in a sunny country or place?
No. What matters is daylight, not direct sunlight. You can still generate some power on a cloudy day. Germany, where clouds cover the skies for about two-thirds of all daylight hours and it rains all year round, is the world's leading solar power generator, with over 300,000 PV systems. Of course you get more power out of the sunshine in the sunnier parts of the world.
6. Are all roofs suitable?
In principle, yes, but some may be better than others. Of course your roof must be strong enough, because traditional solar panels are not light. However the next generation of cells consists of layers of light absorbing materials deposited onto sheets as thin as aluminium foil. They are light, adaptable to any surface or shape, easy to apply (like rolling on wallpaper) and cheap and easy to produce.
If your roof is flat, it may not matter which direction it faces. However in the northern hemisphere sloping roofs should ideally face south or within 90 degrees of south, and all roofs should be free from shadows, otherwise the output of any system decreases. You should however distinguish shading due to overlooking permanent obstructions like buildings or conifer trees from shading due to non-permanent things like deciduous trees which lose their leaves in autumn. Many tools are available for determining how much solar energy is likely to be available from your roof.
7. I own or control a roof - how can I make use of it?
There are a number of different ways in which you might exploit your roof space.
Firstly to use as a location for a plant supplying power to a third party. There are those looking for suitable locations to set up power plants. They might rent or licence the roof from you and install their plant on it, selling the electricity generated to the local power company. Lars Falck, CEO of jiwi solar, a leading German renewable energy company currently building what will be the largest solar power plant in eastern Germany, said in his press release on the project: "To realise further projects juwi solar is therefore always interested in suitable roof space and vacant land in high sunshine areas". He was talking big, because they are big players, but there will be others out there looking for more modest roof top opportunities. Remember, it is difficult to transport energy produced in this way, so panels tend to be installed in or near the place where the energy is required. So a power plant to supply a city centre will have to be installed right in the heart of the city, and if you own one of those roofs you can command a premium
Secondly, to use as a location for a plant supplying power for your own use. There are contractors who arrange and pay for the cost of a solar power plant on your roof or other space, provided you buy the electricity which the plant generates, at rates usually below current public utility rates, and usually for several years, at the end of which you can buy the plant outright at favourable rates. The contractor does all the maintenance (although usually little is required). This can be thought of as a hedge against rising energy costs - you bet that for the period of the contract the costs of electricity generated by the public utility will exceed the fixed contract price (a gamble you might think worth taking in an era of high oil, uranium and coal prices).
Thirdly, to use as a location for a plant supplying power to you for you to sell on. There are contractors who will install plants on your roof or other space to generate electricity for you to sell to the public utility company, usually at several times the market rate. This is the "feed-in tariff" model inspired by German legislation, and adapted by a number of other European states and elsewhere (such as South Australia).
