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Part 1
Mainstream photovoltaic projects
Our energy future is choice, not fate. Oil dependence is a problem we need no longer have â and it's cheaper not to.
[It] can be eliminated by proven and attractive technologies that create wealth, enhance choice, and strengthen common security.
Amory Lovins, Rocky Mountain Institute1
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Chapter 1
Introduction
Why solar energy matters
Energy is the most important resource on Earth. It is estimated to account for nearly 10 per cent of the world's economy.1 Over more than a century the sector has grown to become a tightly controlled behemoth, much of which is in the hands of a small number of multinational corporations. Over the last 40 years, however, the growth of renewable energy has started to challenge this status quo. For the first time, it is possible to generate high-grade, sustainable electricity; that is, to generate electricity without depleting our finite mineral resources. Solar power is central to this âdemocratisationâ of the world's energy.
Energy comes in many forms and is used in many ways. Not all energy sources are suitable for any given application. You cannot practically use nuclear power in a car, nor run a wristwatch on tidal energy. Beyond such questions of suitability, there are an additional four key factors that determine our choice of energy source: sustainability, energy security, price and price again.
Solar energy2 has the ability to win against all these criteria and that is why it should become the dominant energy source within our lifetimes. I expect solar power generation to overtake other renewables, nuclear power, coal, oil and gas by the middle of this century and to become the leading contributor to the world's energy mix. And I am no longer alone in this view. In 2011 the International Energy Agency, originally a bastion of the fossil fuel sector, expressed the view3 that solar would be the leading energy technology by 2060.
Energy, renewables and society
All energy sources are measured against my âfourâ selection criteria of sustainability, security, price and price. Economics dominates, but the other two criteria have become more recognised in recent decades.
The issue of environmental sustainability has come to prominence only in recent years, since the recognition of climate change gained acceptance in the 1990s. It was acknowledged that our traditional energy sources, and in particular the burning of fossil fuels, were the major contributors to carbon emissions and so to global climate change. By contrast, renewable energy sources have no net emissions.
The second issue, energy security, is both a political and environmental concern. Apart from those few nation states lucky enough to be entirely self-sufficient in their energy supplies, countries need to consider where their primary energy comes from, and for how long it will be available. This issue encompasses concerns about the reserves of fossil fuel sources and nuclear fissile materials; and how long these reserves might last. At the same time, the political stability of the source nations, the costs and the uncertainties of transport all add to the risks which energy consumers face.
The approaching âpeak oilâ cliff face, when we are consuming petroleum faster than we are discovering new reserves,4 and the increasing volatility of traditional primary energy prices5 both lead to the conclusion that increased use of renewables is a prerequisite for acceptable levels of energy security. Energy security also has a local dimension; renewables lend themselves to decentralised applications, enabling energy users to have a lesser exposure to imports from remote pipelines or grid networks, and to supply disruption at times of shortage.
So, renewable energy is the obvious winner in terms of sustainability and energy security. Why, then, is it not already dominating the energy sector?
First, it must be said that in some places it is starting to do so. In Europe, for example, there was more new investment in solar power in 2010 than there was in any other energy technology, including coal, oil or gas. In most parts of the world, though, renewable energy remains a âbit-part playerâ, mainly because its capital cost is higher than that of traditional energy sources. This is, however, an unfair comparison because traditional energy sources usually have a higher life cycle cost due to the ongoing requirement for fuel at uncertain prices, and they do not carry the full cost of so-called âexternalitiesâ such as emissions and waste storage.
Recently, many European governments have tried to âlevel the playing fieldâ by introducing subsidies for renewable energies. This has certainly had a positive effect, even though fossil fuels continue to receive greater subsidies.6 In the longer term, sustainable energy sources have to become competitive with traditional energy in an unsubsidised marketplace. This is just starting to happen and I expect solar power in particular to become competitive much earlier than most people realise, as further discussed in Chapter 3.
Policy background
National and international policies and incentives for solar power are covered in greater detail later, but it is appropriate to summarise here the key principles applicable to renewables. In most cases there are two aspects: the carrot and the stick.
Starting with the stick, there is now a well-established, if ponderous, movement under the Kyoto Protocol7 to financially penalise carbon emissions. This attempt to âtax the polluterâ takes different forms in different jurisdictions. Few have yet moved to a fully fledged carbon tax at a realistic level, largely because there are strong, resistant lobbies to such a tax, especially from within energy-intensive industries. Most legislators are more comfortable with an emissions-trading scheme that seeks to use a market-based approach to establishing the price of carbon emissions.
The carrot takes the form of incentives, obligations or financial instruments designed to support renewable energies. Typical examples are feed-in tariffs, renewable portfolio standards and investment tax credits (see Chapter 10). The impact these incentives have on the solar power market will be discussed in depth later, but in summary, the markets where the most effective measures were implemented have shown explosive growth.
Renewable energies
The socio-political considerations driving these measures have focused primarily on the transition to a more sustainable energy economy and apply to renewable energy generally. The term ârenewable energyâ applies to a very wide range of resources encompassing power generation, heat production and the production of solid, liquid and gaseous fuels. Inevitably, different technologies have different characteristics and suit different applications.
Though I do not intend to assess each renewable energy resource in detail, it is useful to consider some of the properties which most renewable energy sources share, and to identify some of the unique characteristics of solar electric generation. Most importantly, all renewable energy sources are fundamentally sustainable. They are, therefore, preferable to traditional energy sources in terms of their resource efficiency, impact on the environment and energy security as outlined above.
Bioenergy sources need a material input in the form of crops, timber or algae, but the other (what I call) âelementalâ renewables use aspects of the Earth's natural environment, such as sunshine, wind, geothermal heat or the movement of water in the rivers and oceans. In most cases this means the source of energy is more ubiquitous than traditional non-renewables and so they can be used widely over the surface of the planet. This also means that renewables like solar, geothermal and wind power offer greater potential for what is known as decentralised energy, placing generation closer to the user than traditional centralised power stations. Renewable energy conversion devices are often more modular than traditional energy sources and can therefore be applied at both small and large scales.
The solar energy options
Solar energy in particular has these characteristics and arguably the most ubiquitous energy source. Outside the polar circles sunlight falls everywhere on the planet every day of the year. Both solar thermal and solar electric systems are built up from individual panels or modules, and so can be applied at the same level of efficiency from milliwatt-to gigawatt-scale systems.
Photovoltaics is not the only technology for converting solar energy, nor even the only solar electric generation technology. For solar hot water (SHW), energy is captured in the form of heat using flat-plate or evacuated-tube solar thermal panels. Another approach is to use an array of mirrors to concentrate the sun's heat onto a boiler used for power generation through a traditional steam cycle. This technology is normally called concentrated solar power (CSP), solar âpower towersâ or solar thermal electricity (STE).
Of the different forms of solar power and solar electric generation, this book deals with photovoltaics, the most widely used solar technology and the fastest growing. Photovoltaics is the direct conversion of light into electricity. It is commonly referred to as PV, an abbreviation so standard that I will use it throughout this book, despite my efforts to resist buzzwords and jargon. The word comes from the Greek âphotoâ, meaning light, combined with âvoltâ, for electric potential, named after the Italian physicist Count Alessandro Volta, who invented the battery in the early nineteenth century.
The dawn of photovoltaics
Observation of the photovoltaic effect is credited to the 19-year-old French scientist Alexandre-Edmond Becquerel in 1839, who first published the finding.8 In practice, it might have been a joint discovery with his father, the physicist Antoine CĂ©sar, with whom he was working at the time. The Becquerels noticed that when light strikes certain substances, an electric charge accumulates. We now understand the science rather more fully and I shall return to this later.
It may seem strange to us today that they did not do more with this discovery, but the field of scientific endeavour at that time was a blanker canvas, and the talented Becquerels had so many fresh areas to explore. An expert in electricity and electro-chemistry, Antoine CĂ©sar invented a galvanometer to measure resistance and an early battery. Alexandre-Edmond was particularly interested in light and worked on spectroscopy, fluorescence, phosphorescence and early photography. Their genius for physics extended to a third generation and Alexandre-Edmond's son Henri, who won the Nobel Prize along with his students Marie and Pierre Curie for their work on radioactivity in 1903.
The photovoltaic effect was broadened when, in 1887, Heinrich Hertz showed by adding a second electrode that the light-induced charge could drive an electric current9 in what became known as the photoelectric effect. Albert Einstein applied his knowledge of quantum theory to this field.10 In fact, his Nobel Prize in 1921, when general relativity was still somewhat controversial, was awarded âfor his services to theoretical physics, and especially for his discovery of the law of the photoelectric effectâ.
Despite all this great science, Becquerel's discovery went practically unexploited for well over a century. In the 1950s, research teams at the electronics company RCA and AT&T's Bell Laboratories developed working PV solar cells with up to 8 per cent efficiency. In 1954 Bell Laboratories applied for a patent for a âSolar Energy Converting Apparatusâ, which was in due course granted,11 but commercial applications were still elusive because of the high cost. About this time, the embryonic space programme realised that missions would be severely restricted if they had to take all their energy supplies with them, normally in the form of batteries. The quest for energy generation sources in space led inevitably to solar power, and in 1958 the Vanguard I satellite12 was the first to use solar cells to produce electricity. These early cells were small, crystalline silicon devices, typically sized at just 1 cm square. Cost in this application was not a primary issue and was very high in those days â around $1,000 per watt of capacity, three orders of magnitude above today's typical solar cell costs.
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Chapter 2
Daylight to electricity
The wonder of photovoltaics
Before describing how the market for large-scale systems developed, it is important to have a little more understanding about where the energy comes from and how photovoltaic systems convert it.
The solar resource
Solar energy is electromagnetic radiation emitted by the sun. Enough of it falls on the surface of the Earth in one hour to power it for a whole year. It has been estimated1 that it would require about 500,000 km2 of solar systems to provide all the energy we need. This is about the area of Uzbekistan â though Uzbek readers should note that I say this only for comparison purposes, not as a proposition! Every locatio...
