Renewable energy technologies

Electricity and CHP

i Around 40 GWh of renewable electricity is generated annually at present. With 1 800 hours of sunshine received annually, the solar resource in the city is one of the best in Germany. The rapid uptake of solar PV has also been supported by the national feed-in-tariff law and under the Renewable Energy Act, power is sold to the grid. Approximately 60 local buildings have significant solar PV systems integrated into their designs. These include the 100 kWp system installated on the roof of the Badenova football stadium in 1995, since extended to 290 kW ; 690 kW on the

Trade Fair Centre roof; 365 kWp above an expressway tunnel; 240 PV panels on the 19-floor façade of the railway station; as well as various PV panels installed on the City Hall, the Fraunhofer Research Institute for Solar Energy Systems, half of the 70 schools, several churches, a few factories (including 570 kWe installed on the Solar-Fabrik manufacturing plant), private houses, supermarkets and multi-storey car parks (Fig. 35). By 2009 over 12 MWp of PV capacity had been installed in total, producing around 10 GWh/yr of electricity. However, this is still only just over 1.1% of the total power demand of the city. Several of the buildings generate more power than is consumed by their residents.

90. Badenova is the largest energy supplying company in the South Baden region, originating from the merger of several local and municipal energy providers, some remaining as principal shareholders.

Figure 35 • Examples of buildings in the Vauban suburb with solar PVon their roofs include a car park, a supermarket (just across the boundary in Merzhausen), private houses and an apartment block with the tram to the city centre running on grass covered areas

Figure 35 • Examples of buildings in the Vauban suburb with solar PVon their roofs include a car park, a supermarket (just across the boundary in Merzhausen), private houses and an apartment block with the tram to the city centre running on grass covered areas

I hive 1.8 MW Enercon wind turbines have been constructed on city land in the nearby Schwartzwald (Black Forest) overlooking the city (Fig. 36). They generate 14 GWh/yr of electricity that meets around 1.3% of total city demand. Since the state council has prohibited wind further developments for aesthetic reasons, targets to increase this share may no longer be achievable.

Photo credit: Ralph Sims

I T he Vauban biomass CHP plant using wood chips from the nearby forest and wood processing industries has 345 kWe capacity and produces around 1.5% of the total power demand for the city. The heat capacity of 7 MWth has been utilised in a district heating scheme since 2002 to meet around two-thirds of the local heat demand. In addition, a solar PV manufacturing facility has installed a small CHP plant running on vegetable oil. In total, over 50% of the city's power demand is met by around 130 local, small-scale CHP plants, but most of these are burning natural gas. For example, the chemical company Rhodia has operated a CHP plant in partnership with the local utility company Badenova since 1998. It has the capacity for 60 MWe and 244 MWth of heat used on site, giving a performance efficiency of around 80%.

I T landfill gas site also produces CHP, with a total power generation from biomass sources amounting to around 16.6 GWh/yr, or 2% of total energy demand. The target for biomass CHP electricity is around 6% of the projected total demand by 2010. Badenova is planning five new sites for the production of biogas within the Freiburg region. The gas will be fed into the natural gas network and used as fuel for CHP plants in Freiburg to help meet the targets.

I Treiburg's refuse collection used to be taken to the city's landfill site before 2005. Since then, non-recyclable waste is incinerated at a thermal plant in the Industrial Park, Breisgau 20 km south of Freiburg. This plant supplies electricity to 25 000 households and extraction and use of the surplus heat is planned.

I S mall hydro-power plants in local rivers, streams and canals generate around 1.9 GWh/yr.

I Tn enhanced resource geothermal project near Freiburg has been evaluated with the aim of producing 4 to 10 MWe electricity and 23-40 MWth heat. The high drilling cost, estimated to exceed EUR 50M, is a disincentive, as are the technical and safety risks. Whether construction will begin within the next two to three years remains uncertain.

Heating and cooling

I Tround 15 000 m2 of solar thermal collectors have been installed on numerous buildings within the city. This includes the University Hospital cafeteria with a 270 m2 collector to produce hot water for use in the kitchen and dishwasher.

I T he "Heliotrope" rotating solar house that tracks the movement of the sun is a novel design of building by local architect Rolf Disch. It is cylindrical, built on a single supporting shaft, with triple-glazed windows on only one side and with solar collectors mounted on the roof.91 It follows the sun in winter to gain heat, but can rotate away from it in summer to provide cooling.

I T ground source reversible heat pump has been installed by the pharmaceutical company Pfizer in its Freiburg plant to give mechanical heating, mechanical cooling or natural cooling to its office building. The 19 probes drilled to 130 m depth at 6 m spacings in a field of 0.12 ha in 2008 can provide heating up to 135 kW capacity with a cooling capacity to 110 kW. The soil temperature varies between 10oC and 20oC from the end of the heating period to the end of the cooling period. The company also has installed a Quantum high efficient chiller and a biomass boiler and is planning to install a biomass CHP unit.

Transport

I T he city trams are powered by electricity with 80% of their total demand generated by local hydropower plants and the rest from other renewables in the mix.

I Good cycle tracks, and easy access to electric trams and buses for the majority of the city population, have enabled 35% of residents to choose to live without owning a car. In Vauban,

91. http://www.inquirer.net/specialfeatures/theenvironmentreport/view.php?db=1&article=20090314-194059

car-free living is strongly promoted, with easy access to 35 share-cars available for residents to rent when required, by simply booking one over the internet. Residents are encouraged to park their private cars in one of the two multi-storey car parks located a short distance away from the housing areas, for which they pay a substantial annual fee. A regular, free tram service to the Freiburg city centre and elsewhere has been installed since 2006, with buses also providing free travel.

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