Category Renewable Energy – The Facts

The heart of a PV array – the solar cell

As described in Chapter 2, solar thermal energy converts solar rays into heat. Photovoltaics is another way of using solar energy. This technology is based on a well known effect in physics: some semiconduc­tors convert light directly into electrical current. This chapter focuses on the main applications and the future of photovoltaics as seen from today.

Just as the absorber is the heart – the part that converts sunlight into heat – of a solar thermal array (see 2.1), the solar cell is the heart of a photovoltaic array. Spread out thinly over the largest possible area, this semiconductor converts incident light directly into electrical current.

The first solar cell was made using silicon in 1954, and 90 per cent of all solar cells currently made worldwide are still manufac­tured using th...

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Expanding hydropower – the example of Germany

Hydropower has been used for centuries in Germany. Often, hydropower was the start­ing point for merchants and cottage industries (mills, pumps, etc.). Starting in the mid-19th century, hydropower was used to generate electricity, and up to 2003 it was the largest source of renewable electricity in Germany. Today, hydropower provides some 20 billion kilowatt-hours of electricity per year, roughly 4 per cent of the country’s elec­tricity consumption.

At the same time, hydropower is the only renewable source of energy that has been largely exhausted in Germany; roughly 75 per cent of its potential is already exploited. The potential for new large hydro dams has already been completely used up, though current systems can generally be revamped to increase power output considerably...

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Compensation for solar power with a return on investment

Before feed-in rates were offered for solar power starting on 1 April 2000, there was a tremendous difference between the cost of such systems and the amount paid for solar power. In 1999, around 8 eurocents per kilowatt-hour was paid for one kilowatt – hour. If array owners sold all of their power to the grid, they would get just under €1500 over 20 years for a 1 kilowatt-peak system (20 years at 900kWh/year at 0.08 €/kWh = €1440). But back then, such a system would have cost around €10,000 and therefore never have even come close to paying for itself.

To provide a proper return, the Solar Energy Association of Aachen came up with the idea of offering feed-in tariffs for solar power at the beginning of the 1990s...

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Renewable Energy -. The Facts

There are dark clouds on the horizon. Climate change – long researched, discussed and denied – is increasingly making its pres­ence felt. Drawn up by more than 2000 climate researchers from around the globe, the International Panel on Climate Change’s (IPCC) 2007 report has a clear message: the Earth will inevitably heat up by more than 2°C above the temperature of the preindus­trial age. Additional warming would have enormous consequences for mankind and the environment, and a global economic crisis can only be avoided if the global community works closely together.

‘The time for half measures is over’, former French President Jacques Chirac once said, commenting on the challenges of climate protection...

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The off-grid solar house – a model for the Solar Age?

In 1992, the Fraunhofer Institute for Solar Energy Systems opened its Energy- Autonomous Solar House in Freiburg, Germany, as a research and demonstration project.21 With 145m2 of floor space on two stories, it has five rooms, a kitchen and ancil­lary rooms. This house proved that a single-family home could make do with the solar energy from its roof and walls the whole year even in the German climate. The ‘autonomy’ here thus concerns not only space heating, but also hot water, gas for cooking, and electricity. Several years of operation demonstrated that this independ­ence is possible without any loss of comfort for residents.22 Like a passive house, this house has:

• Extremely good insulation.

• Large southern windows to exploit solar energy passively.

• Regulated ventilation with...

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Fuel cells in mobile applications

‘The only thing that comes out of the exhaust is water vapour!’ In light of climate change and smog, such statements seem attractive at first. No wonder most major car manufacturers have been working on fuel cell cars at some point or another;16 these cars would have electric drive trains powered by electricity from fuel cells. A number of different concepts have been investigated: fuel cells with hydrogen, methanol and natural gas.

In the mid-1990s, the first prototypes were presented. Daimler-Chrysler also launched a test fleet of 30 buses and 60 cars in 2002/2003.17 Volkswagen has discontinued its research on hydrogen drive systems and BMW discontinued its field tests on hydro­gen as a fuel for cars with conventional engines in 2009 .18

Today, no market launch is in sight...

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Phasing out nuclear

The 1986 reactor catastrophe in Chernobyl finally made everyone realize what the risks of nuclear power are. But climate change has since made it clear that our current energy supply system also poses tremendous risks. The energy sector is taking advantage of this new situation to play one risk off against the other; in the process, nuclear energy is now being sold as a way to combat the greenhouse effect. After all, the argu­ment goes, nuclear energy offsets fossil energy, thereby reducing carbon emissions.

While correct on the surface, this claim leaves out a number of important issues. For instance, under the Schroeder government Germany resolved to decommission its nuclear plants after 32 years of service...

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Example 3: Efficient pumps

More efficient pumps and pump controls would save many billions of kilowatt-hours of electricity and heat in homes, businesses and industrial plants. But this change would require decision-makers to be better informed and tradespeople better trained; in addition, we would need an investment philosophy that accepts higher investment costs in return for lower operating costs.27

These three examples make it clear that a solar energy supply is easier to reach and less expensive if conservation measures are simultaneously exploited.

Towards the goal of 100 per cent solar energy, Example 2 does not seem that convincing. If we want to go further, we can do the following:

• Use more solar energy. A larger solar array would cover a larger share of heating demand (see 2.3).

• Use greater efficienc...

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