Category Renewable Energy – The Facts

Is there enough land for biofuels?

Expanding the production of biomass and biofuels in particular would require tremen­dous amounts of land – land that is not available in unlimited quantities either in Germany or elsewhere. At the same time, land is needed to produce food. As greater amounts of land are devoted to the produc­tion of biomass for energy purposes, conflicts are therefore inevitable. The figures below make that clear:

Worldwide, some 50 million square kilome­tres were available for agriculture in 2000, equivalent to 8200m2 per person. Most of this land is used extensively, however, such as grasslands in Argentina. Only around 15 million square kilometres, roughly 2500m2 per person, is used intensively. This figure will drop, however, as growing populations overtake production increases...

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What is the energy payback?

With wind turbines and solar arrays getting bigger all the time, some wonder whether all of the materials used (‘grey energy’) are worthwhile – or, put differently, do we invest more energy in such systems than they will be able to generate?

The term to understand here is ‘energy payback’. It is an indication of how long the system needs to produce the energy invested in it. After that time, it begins producing a ‘surplus’. If a system can remain in operation longer than it needs to pay back the original energy investment, the energy payback is positive.

Energy payback not only depends on manu­facturing, but also on how the system is used. For example, a wind turbine in windy locations will produce more power, thereby foreshortening its energy payback...

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Grid-connected PV arrays

Power generated from photovoltaics offers a number of benefits:

Emissions – PV arrays are silent and emit no waste gases.

Service life – since there are no moving parts, solar arrays have very long service lives. Manufacturers offer warranties of 20 years and longer for solar panels. Environmental impact – silicon solar cells are environmentally friendly during oper­ation and can be recycled without any environmental impact.2 Resources – silicon is the second most common element on the Earth’s crust, so it is hard to imagine us running out of the raw material.

Wide range of applications – photo – voltaics can be used in a large number of applications from pocket calculators and wristwatches to large solar power plants.

Thanks to these benefits and a number of governmental policies to prom...

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Hydropower and nature conservation

There are ecological limits to the expansion of hydropower. One goal of nature conser­vation is to protect natural waterways and waterways close to nature. This goal can conflict with the use of hydropower; after all, hydropower units change ecosystems. When permits are granted for hydropower units, the individual situation must be assessed exactly. The following must be taken into consideration and weighed against the advantages of renewable power:

Impact on the ecosystems of flowing water, especially the protection and development of local flora and fauna both in the water and on banks.

Impact on water management, espe­cially flood protection, flow rates and groundwater.

Impact on other water functions, such as recovery rates.

Minimum water volume

Diversion hydroplants, one of the most...

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From the Feed-in Act to the Renewable Energy Act (EEG)

The rollout of the Feed-in Act at the begin­ning of 1991 marked a turning point in the history of wind power in Germany. For the first time, grid operators were required by law to pay a floor price for renewable power sold to the grid. The rates paid were based on the average power prices for all retail customers in the previous year.

Grid operators were obligated to pay 90 per cent of that figure for electricity from wind power and solar arrays, 80 per cent for power from biomass and small hydro stations with a capacity up to 500kW, and 65 per cent for power from hydro plants with a capacity ranging from 500kW-5MW.

For instance, Germany’s Bureau of Statistics calculated that the average price per kilo­watt-hour in 1997 was 9...

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‘Renewables are the way of the future’ – 20 years ago, this was a minority opinion. Back then, our energy supply came from fossil sources (coal, oil and gas) and from nuclear power. Power providers did not believe that solar energy could ever make up a large share of the pie and merely spoke of it as the ‘spare tyre’, which was good to have on board, but not something you would want to rely on all the time.

Over the past few years, opinions have begun to change. Markets for renewable energy sources are booming around the world. At the same time, the negative effects of our fossil-nuclear energy supply become clearer all the time:

• The dramatic impact on the climate of our uninhibited consumption of fossil energy is causing glaciers and polar ice to melt at rates previously unimagined...

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Plus-energy houses

Generally, homes are energy consumers, not producers. They need heating energy and electricity, which they get from outside. But a model project in Freiburg, Germany, turns the table. The houses in the Solar Estate neighbourhood not only cover their own energy demand, but also export excess elec­tricity to the grid.23

The technologies in this residential area have already been presented in the previous sections. They were simply recombined here.

• As in passive houses, excellent external insulation on the walls, windows and roofs is combined with a ventilation system with heat recovery and large south-facing windows that passively use solar energy to cover the remaining residual energy demand, which ranges from 6-12kWh per square metre a year in this project – considerably below the pas...

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The potential in Germany

The previous chapters discussed various sources of solar energy and the components within a solar energy supply. In this chapter, we provide a more holistic overview – what share of our energy supply can the various sources of renewable energy have, and how much energy can they provide?

The supply of solar energy is gigantic (see 1.6). However, the theoretical potential can never be completely exploited because avail­ability depends on time and location, the efficiency of the technologies used and other aspects. After these limitations have been taken into account, the technical potential is much lower than the theoretical even before we have discussed economic feasibility.

A number of studies have been produced on the technical potential of renewables in Germany, with varying results...

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