Jurgen Maier & Reinhold Vetter

Institute for Land Management Compatible to Environmental Requirements, Mullheim Auf der Breite 7, D-79379 Mullheim, Germany

phone: 0(049) 7631-3684-0, fax: 0(049) 7631-3684-30, e-mail: poststelle@iful. bwl. de

In search of sensible alternatives for biomass production the cultivation of short — rotation coppices on agricultural crop land has to be tested. From an economic point of view this is a feasible long term option (i. e. , if the price for biomass increases according to the shortage of biomass by-products) due to the fact that in perennial cultivation and with low input it can produce a high yield of biomass within a short time.

These cultivation conditions and results may possibly have the ecological consequences wanted: high yield of biomass respectively energy as well as low input of energy result in a favorable energy balance and in a high energy output per unit area. The ecological assessment is improved by the renunciation of yield — increasing input such as fertiliser and pesticides; perennial cultivation is in general considered to be advantageous for soil protection, water and species. In the specific case of short-rotation coppice, research came to the conclusion that willow and poplar, for example, are suitable for the sanitation of soil and inshore waters. In comparison to other biomass — such as energy cereal and energy grass — another ecological advantage is the lower amount of emissions that can be expected in a technically optimised combustion process due to the favorable composition of fuel.

Three short-rotation coppices were tested on three locations in two different regions in the state of Baden-WOrttemberg (in the Southwest of Germany) with regard to an energetic use of biomass.

The two locations in the upper Rhine valley differ fundamentally in their yield potential (see Table 1). In MOllheim the soil is profound with a good water supply. With regard to the water supply, Grissheim is a marginal location where grain maize is irrigated. In the cooler location of Binsdorf, located in the foreland of the mountainous Alb, the temperature is the most limiting factor for thermophile plants.

The three short-rotation coppices, willow (Salix viminalis), poplar (Populus spec.) and empress tree (Paulownia tomentosa) were planted on large plots in the form of cuttings, originating from various tree nurseries. They were planted in different years (see Table 2). The standing crops were cultivated without any pesticides or fertilisers — with exception of the planting year, if necessary. In Grissheim the experimental plots with willows and poplars were irrigated as they were located within a field of grain maize which had to be irrigated regularly.

The rotation period chosen for the short-rotation of willow used as coppice forest was 2 (U2) and 3 years (U3) at the two locations in the upper Rhine valley, and 3 years (U3) at the cooler location Binsdorf. Poplar was harvested in a 4-year-cyle, the empress tree was harvested once after a 5-year-rotation. The harvest was done by machine (maize chopper) or manually with a chain saw on the whole parcel, including the outer rows of plants. The 1996 yield of willow and poplar in Grissheim was not taken into consideration, as the outer rows of plants were not harvested.

Results

Yield

The three species of trees tested gave an average harvest of 11 tons of dry matter per hectare and year on the two locations in the Rhine valley and mountains, including the irrigated location Grissheim in the upper Rhine valley (see Table 3). By excluding the irrigated location, the average yield is 9 tons. The species obiviously differ in their yield potential. Willows show a lower yield level and seem to be limited mainly because of lower amount of water and not as much by temperature. Without irrigation willows achieved 8 tons. At the cooler location in Binsdorf they produced some more biomass in a 3-year-

rotation than in MQllheim with a lower precipitation (on average of the two rotations U2 and U3). These yields correspond with the data of UNSELD (1999) who states the yield with a maximium of 7 to 8 tons of dry matter for willow and poplar on experimental locations on a dry soil in the summer. In Grissheim willows had not quite the level of poplars. In 1996 the appearance of the poplar leaf beetle (Melasoma populi) was discovered and caused defoliation of individual leaves. A yield reduction because of the beetle is not being assumed. Without irrigation, the thermophile empress tree produces at MQllheim in the Rhine valley nearly 13 tons of biomass, i. e. more than willow.

Fig. 1 shows that the 2- and 3-year-rotation obviously has no influence on the production of biomass on willow plantations. In MQllheim, an insignificant higher yield of biomass was ascertained; in Grissheim, the location with irrigation an insignificantly lower yield. FRIEDRICH (1999) did not find out any influence of the rotation time on the yield of dry matter either, that had been produced in a 5- or 10-year rotation. With regard to the biomass production of the individual rotations in Grissheim starting from the third respectively the first harvest, the biomass yield shows a significant reduction from one harvest to the next. After 10- or 12-year-cultivation the biomass yield is less than half of the starting yield. The rootstocks which did not sprout any more increased from one rotation to the next. Regarding the younger short-rotation coppice in MQllheim, the yield of the first harvest is lower than the following ones. This concerns both rotation periods. The reduction of the biomass production, beginning from the third rotation may originate in the loss of production because some rootstocks did not sprout. In Binsdorf’s 3-year-rotation the yield is the same as in MQllheim. In the 2003 harvest there were also less rootstocks sprouting than the harvest before.

Fuel Characteristics

If the coppice biomass is used as solid fuel — for example in wood-fired heating (power) plants — the combustor operating company is mainly interested in the composition of the wood listed in Table 4.

Compared to forest timber (trunk wood respectively twigs) coppice biomass contains more water, if it had not been left in the field to dry. The upper heat value H0 of the three different coppice biomass with about 20 Megajoule per kilogram dry matter is the same as of forest timber. The ash content of willow and poplar is about 4 times higher than of empress tree which has the same ash content as forest timber, i. e. 0,5%. With more than 3%, twigs of spruce have the highest ash content of all tested wood. For a low-emission combustor and its trouble-free operation, sulphur, nitrate and chloride are the relevant components. Mainly in a high-temperature range chloride is unwanted because of the danger of corrosion and dioxine emissions (MAIER et. al., 1998). The different coppice biomass has a little higher content of sulphur than trunk wood, but it is significantly lower than that of twigs of spruce. The nitrate concentration of the empress tree is comparable to trunk wood, whereas willow and poplar show a nitrate concentration which is 5 times higher than of trunk wood, but only half as high as of twigs of spruce. The chloride concentration of all coppice biomass is below 0,01% and therefore on a very low level, with exception of willow. Because of an individual value of more than 0,3% in the willows harvested in Grissheim in 1996, their chloride concentration is 10 times higher.

Summary

In two pedo-climatic different regions in the state of Baden-Wurttemberg three short — rotation coppices willow, poplar and empress tree were tested with regard to their biomass productivity on arable land and to their properties for energetic use. Between 8 and 13 tons of dry matter per hectare and year could be produced under extensive cultivation

conditions, over 15 tons with irrigation. Due to their composition, it can be assumed that their use as solid fuel in a biomass combustor is just as unproblematic as with forest timber.

Key words: short rotation, willow, poplar, empress tree, productivity, quality of fuel

Literature

E. Friedrich, 1999. Anbautechnische Untersuchungen in forstlichen Schnellwuchsplantagen und Demonstration des Leistungsvermogens schnellwachsender Baumarten. In: Bundesministerium fur Ernahrung, Landwirtschaft und Forsten, Bonn, Modellvorhaben „Schnellwachsende Baumarten“. Landwirtschaftsverlag Munster, Deutschland, 19 — 150.

J. Maier, R. Vetter, V. Siegle, H. Spliethoff, 1998. Anbau von Energiepflanzen — Ganzpflanzengewinnung mit verschiedenen Beerntungsmethoden (ein — und mehrjahrige Pflanzenarten); Schwachholzverwertung. Abschlussbericht Forschungsvorhaben Nr. 22-94.11, Ministerium Landlicher Raum Baden-Wurttemberg, Deutschland, 100 Seiten

R. Vetter & J. Maier, 1996. Production of energy crops in summerdry regions of Southwest — Germany for solid fuel. Biomass for energy and the environment, Proceedings of the 9th European Bioenergy Conference, Copenhagen, Denmark, Vol. 1: 528 — 530

R. Unseld, 1999. Kurzumtriebsbewirtschaftung auf landwirtschaftlichen Grenzertragsboden — Biomassenproduktion und bodenokologische Auswirkungen verschiedener Baumarten. Diss. Univ. Freiburg, Shaker Verlag, Deutschland, 193 Seiten.

The solar campaign is carried out by O. O.

Energiesparverband. O. O. Energiesparverband is the regional energy agency of Upper Austria and was established in 1991 by the regional government. Aim of the agency is the

promotion of energy efficiency, RES and innovative energy technologies. O. O.

Energiesparverband is a central institution for energy information and one of Europe’s

largest energy advice and information providers. Services to different target groups, from

private households to SME’s and public bodies are offered.

The main services of O. O. Energiesparverband include:

• energy information and awareness raising activities

• energy advice for private households and industry: 15,000 energy advice sessions annually

• international co-operation & European projects: vice-precidency of FEDARENE, member of EUFORES, co-ordinator of the OPET-RES-e network

• management of a sustainable buildings programme which includes energy certification for buildings and the calculation of an energy index for every new single family house (> 30,000 calculations carried out)

• a great number of different training activities (for energy advisors, for installers etc.)

• organisation of conferences, workshops, seminars, competitions

• management of the OEC, the network of green energy businesses.

Results

In Upper Austria, 674,000 m2 solar thermal collectors are installed, which equals 488 m2 per 1,000 inhabitants, a leading European figure.

In total 230 million kWh heat are produced annually and the Upper Austrian companies account for a quarter of the annual turn-over of the Austrian solar industry of about 121 million € and are securing around 450 jobs

As a result of the promotion activities, more than 100 large-scale solar thermal systems have been installed in public institutions and companies totalling more than 3,500 m2 collectors.

The awareness raising activities are also responded by the population, a recent opinion poll among 500 Upper Austrian citizens showed the image of solar thermal collectors is very good:

• 93% believe solar collectors to be environmentally friendly

• 75% that they are convenient

• 54% in general could imagine to use them

• the only advantage is seen in the high price.

The example of O. O. Energiesparverband and Upper Austria clearly demonstrates that a lot can be done at a regional level, provided the necessary political backing is given and a comprehensive action plan including information and promotion programmes is carried out.

A brief summary of the energy resources of Georgia is given below:

1.3 Oil, Gas and Coal

There are small amounts of oil in Samgori region (east Georgia) and along the Black Sea shelf near Supsa (west Georgia). Also, small amounts of natural gas exist in east Georgia. Coal is mined in Abkhazia and near Kutaisi (west Georgia), but between 1976 and 1991 output fell nearly 50 percent, to about 1 million tons annually. The largest deposits, both in Abkhazia, are estimated to contain 250 million tons and 80 million tons, respectively. Domestic coal provides half of the requirement of Rustavi metallurgical plant.

1.4 Solar Radiation

Solar radiation varies significantly at different locations in Georgia. Also, there is a large difference in sunshine hours between summer and winter. Average monthly sunshine in summer months reaches 225-300 hours, but drops to 50-75 hours in winter. Generally, eastern Georgia is much sunnier and drier than the western part of the country. Tables 1 & 2 present the distribution of annual and monthly solar radiation data for Tbilisi and a number of other sites throughout Georgia.

SHAPE * MERGEFORMAT

1.5 Wind

Although Georgia is not a very windy country, there are several promising locations with high average annual wind speeds. One of them is Mount Sabueti (1248 m) with an average annual wind speed of 9.1 m/s.[37] Later measurements, conducted for a short period of time (August 1998 — September 1999) by Renewable Energy Resources Department of “Energogeneratsia” (State Power Generation Company of Georgia), yielded 7.52 m/s at 50 m height. Several other promising sites for future wind park developments are mountainous surroundings of Tbilisi, Didi Digomi district of Tbilisi, Tbilisi Sea area, Poti port on the Black Sea shore and Chorokhi river canyon in Ajara (south-west Georgia). The total wind potential that could be tapped for power generation is estimated as 4.5 billion kWh per year.[38]

1.6 Hydro Power

Georgia is very rich with hydro energy resources. There are more than 26 000 rivers with, according to some estimates, the ability to generate over 80 billion kWh per year. Currently less than 10 % of their potential is tapped.

1.7 Geothermal

Total geothermal water resources of Georgia are projected to be up to 250 Mln m3/year. For present day, up to 300 springs with 50°-110°C water temperature are registered. Currently operating geothermal wells provide approximately 60 000 m3/day debit. Some good sources of geothermal hot water are listed below:

• 85°-100°C natural flow field in Zugdidi area (western Georgia) — The wells need rehabilitation.

• 60°C natural flow field near Lisi Lake in Tbilisi — 4000 m3/day debit. The wells need rehabilitation. This field supplies hot water to Tbilisi’s Saburtalo district.

• 55°C natural flow field in the Vardzia area (southern Georgia) — 240 m3/day debit.

The 443,2 kWp PV generator is composed by 2686 modules with the following characteristics:

o Nominal Power: 165 Wp o Power Tolerance: 5% o Voltage MPP: 17.4 Vdc o Frameless, transparent Tedlar.

Modules were packed in groups of 360 units. 16 ones of each group were randomly chosen and sent to IER-CIEMAT for independent quality control and power measuring. Previously, 4 modules were calibrated and used as reference ones for the whole campaign of tests both in IER-CIEMAT and in ISOFOTON factory. IER-CIEMAT2 is an Spanish public laboratory devoted to investigation and certification in the field of renewable energies, including PV.

Due to voltage input of inverter, a configuration of 79 rows with 34 modules in series has been used. Since dispersion losses are directly related to number of modules in series, it is recommended to classify them by current values when that number is high.3

In order to carry out classification previously to manufacturing, an internal production database was used as reference. Therefore three categories were established so modules were classified as soon as power was measured. It should be noted that both values from database and power measuring were corrected to include reference from CIEMAT.

PV generator is electrically DC floating. Due to high voltages used (600 Vdc), a permanent insulation monitoring device is installed inside DC protection and control box. Several mechanisms of protection can be activated when an insulation fault is detected: for example, disconnection of PV generator and inverter, short-circuit of PV generator and direct connection to earth4. This action can be programmed and selected through remote control.

The schematic structure of the new module concept is shown in Fig. 1. The module consists of a copper layer, a glass fibre sandwich foil (0.5mm FR4), a second copper layer, the solar cells, the encapsulation material and the cover material (down to top). The solar cells are series connected by solder or silver filled adhesives. The last bus bar is contacted either with a small copper band and solder or with an electrically conductive tape to the PCB. The solar cells are connected to the PCB with a nonconductive SMD adhesive for the chip assembly.

Such a module structure has the following advantages:

1. High module efficiencies (> 20%)

Because of the shingle technology the shading surface is reduced to a minimum. Depending on cell quality and packaging a module efficiency over 20% is possible.

2. Stable despite 1.5 mm thickness

Because of the printed circuit board and the fixed connection of the solar cells attached to it by the SMD adhesive, the solar module receives an extremely stable shape. For example, the module can fall from a height of 1.5 m to the ground, without any damage.

3. Only 1.5 mm module rim

A module rim of 1.5 mm outside the solar cells is necessary. This frame is necessary, in order to stick the packaging material to the PCB. Larger width is not used, since the device integrated module is not permanently exposed to wind and weather.

4. Variable position of the contacts on the back

Due to the double-sided structure of the printed circuit board it is possible to contact the module on the back in any place. The contacting can function in such a way that two spring loaded contacts press on two edge contacts of the module.

5. Aesthetic exterior

Apart from the purely technical advantages the shingle technology on printed circuit boards has a very even appearance (see Fig. 8).

Contacting

New steps were made by E. Guk, V. Shuman et al. (Ioffe Institute), by authors (VIESH, VEI), by Sater B. (USA), et al, in developing new technology of manufacturing SCVJ, including, for example, direct bonding.

A method of manufacturing a high intensity SCVMJ (thermal compression bonding with siluminum) [13] was developed in VIESH. The main goal of this technology is to provide a structure for a photovoltaic cell which gives in result improved characteristics: improving quality of interconnecting soldering, eliminating of compensative influence of aluminum to n+-layers, high temperature tolerance and mechanical firmness (the cross section of classical vertical structures without antireflection coat is showed at Fig.3). According to this invention, the siluminum layers prevent a penetration of compensative impurities (Al) into n+- region. The produced solar cell structure gives in result high quality mechanical and electrical contact, high fill factor for I-V-characteristic (more than

0. 8), and increased tolerance to high temperature under high intensity.

The next technology [14] offers the method of manufacturing a high intensity solar cell using n-type silicon with high diffusion length.

In other version of solar cell’s design of this invention it is additionally expedient to form alloyed inversing layer and TiOx antireflection coatings at the front sensitive surface. In this case hybrid cells representing a combination of planar and vertical p-n-junctions are manufactured.

Advantage of such design is combining of two processes: soldering and diffusion, which moreover are carrying out at the lower temperatures. It allows canceling a number of technological steps, to decrease a possibility of introducing different contaminations and defects and, in general, to save a high diffusion length which leads to increasing efficiency and to decreasing energy consumption for manufacture.

A number of research works were carried out at A. F. Ioffe Physicotechnical Institute [17-18, 21-23].

The Silicon Direct Bonding (SDB) or fusion bonding technique, in principle, a rather simple process of room temperature mating of two polished wafers and subsequent annealing at higher temperature, allows the fabricating of special devices for many applications. Direct bonding of silicon to silicon, as well as bonded interfacial layers of
different materials such as siluminum, poly-silicon, silicon oxide or nitride is feasible by SDB. Bonding of patterned wafers containing microstructures is an important technique for micromechanical device fabrication. Aligned bonding of preprocessed wafers offers new possibilities for 3D-integration. For semiconductor device manufacturers the Si-Si bonded wafer offers a cost effective alternative to thick epitaxial layers that have traditionally been used for applications such as power devices and p-i-n diodes. Last several years a number of papers, devoted to using SDB for solar cells are appeared. Solid-phase direct bonding silicon wafers having the diffusion p+ — or n+-layers with high surface doping concentration is described in [22].

The SDB for the fabrication of solar cell structures with vertical p-n-junctions is demonstrated in [23]. This technology based on ion implantation and direct wafer bonding of p+-p — n+-structures. The internal quantum yield of such structures was near 1 in the wavelength range of 350-900 nm.

The several methods using SDB are proposed in [19].

According to the first method of manufacture the wafers with p+-p- and n+-n-structures are oriented at the same crystallographic direction and bonding under a pressure in a vacuum furnace at the temperatures 800-1000 oC. The technological steps are similar to [13, 14]. In accordance with the second method the p+-p — n+-structures are exposed to SDB and in accordance with the third method symmetrical p+-n — p+- or n+-p — n+- structures are used for SDB. The cross-sections of interdigitated contacts on the backside of SCVMJ are shown at the Fig.9.

These methods allow to avoid the processes of metallization right up to SDB and to reach high efficiency values.

Using optimized bonding process it is possible to join two wafers of any doping and orientation with an interface that is free of silicon dioxide, silicon defects, precipitates and any unwanted doping. All this means that holes and electrons can move freely across the interface as if it was not even there!

Last achievements of Sater B. also show good prospects for vertical multi-junction technology. He developed high voltage silicon vertical multi-junction (VMJ) solar cells that provide efficient operation for up to 1000 suns intensity. The VMJ cell is an integrally bonded, series-connected array of miniature vertical junction p-n-n+ unit cells. The design gives high voltage, low current operation and other performance advantages at high intensities. Fabrication processes are being finalized and efficiencies exceeding 20% at up to 1000 suns intensity are expected. Preliminary tests at about 500 suns intensity show a 0.78-cm2 VMJ cell containing 40 unit cells with a maximum output power density of 11.385 W/cm2 at 24.5 volts with an estimated efficiency of 20.2%.

Applications

High voltage photovoltaic SC “Photovolt” are intended for power supply of high-voltage radio, dosimetric, other electronic and special equipment (rated at 100 to 1,000 V) as well as household appliances (rated at 220/110 V).

Solar power installations are currently sufficient to provide lighting, pump water, and power telecommunications facilities, and home appliances in remote areas and in vehicles.

The structures with vertical p-n junctions can be used as a high-sensitive sensor of position of the light beam (including transparent type sensors in IR region near the edge of absorption).

Let us also mention about project developing 3-D radiation imaging detectors here based on the ability of deep etching in a semiconductor by new methods to form deep macrospores or trenches in the material in a pixel matrix that can be doped to form vertical p-n-junctions [24].

Thermo-photovoltaic conversion, laser transfer energy systems, space concentrator systems, medical power supply systems, photometry (including high intensity), detection of nuclear particles are also the interesting areas for application of SCVJ due to low series resistance, high temperature resistance, high voltage output, unusual geometry and identical receiving surfaces. Taking into account that concentrator companies are making progress toward increasing their market, the SCVJ may become a good option of concentrator SC.

Small-scale version of space concentrator with SCVJ on the backside (along the top edge) of reflectors is depicted in Fig. 10.

SCVJ are very good for special applications such as, for example, space solar probe where SC with high thermal and radiation tolerance intended for conversion solar radiation with intensity, which is changing from usual to very high levels.

Conclusion

A number of practical SCVJ was developed and new approaches were proposed in Russia and in the USA.

Theoretical estimations indicate the limit of efficiency of SCVJ is similar to the limit of efficiency of traditional (planar) SC, but they are more suitable for conversion of concentrated light and have improved performance in term of radiation tolerance.

The combined spectral-probe and other methods have been developed for the investigation of vertical multi-junction solar cells and other types of the solar cells with complex structure.

According to obtained experimental data limit specific power is equal to 3.6 kW/cm2and specific voltage is equal to 100V/cm2. These values are probably impossible to have for SC of planar type.

At the modern stage of development semiconductor technology it is possible to use new design, concepts, and approaches and new advanced technology to achieve the efficiency close to the theoretical limit.

The aim of this part of the research is to individuate total productivity of regional forest areas, both in terms of marketable wood and in terms of residues to be used for energy purposes. As previously underlined, the biomass usable for energy purposes is produced during silvicultural operations aimed at producing firewood and industrial wood. In fact, applying current prices it doesn’t result convenient to fell woods just for the purpose of producing wood chips for energy use. The two types of production result tightly bound since the amount of residues for energy purposes, that it is possible to recycle, is directly proportional to ecological and economic productivity of forests in terms of marketable assortments.

The work was articulated in the following phases. The first was the individuation and analysis of the geographic localization of forest resources through the Territorial

Information System. The second was the quantification of sustainable total productivity, by mean of a coefficient in term of biomass for hectare in a year.

In Sicily context, there are only two areas of the regional territory that produce this type of biomass and are two regional park: “Parco dei Nebrodi” and “Parco dell’Etna” .

The first elaboration on the Territorial information System concerned the selection of potentially productive forest crops on the basis of the following criteria:

— slope below 70%

— easy or rather easy accessibility

— slightly affected or free from erosion

Has been estimated that in Sicily it is theoretically possible to produce, free from environmental risks, more than 2,2 million tons of marketable wood and 500.000 tons of residues for energy production. Under the economic perspective, it isn’t convenient to exploit all woods, since not always the profits are able to cover the utilisation costs. By using a specific model, it has been possible to estimate that each year in Sicily there is a potential production of 1,15 million tons of firewood. The results of the model are coherent with the time series quoted in official statistics. The exploitation of this type of biomass is strongly connected with the forest utilization that in Sicily contest are very modest. Consequently the global potential is reduced to 7546 ton for “Parco dell’Etna” e 8734 ton for “ Parco dei Nebrodi”. In this last context has been carried out and energetic analysis comparing some different heat system and different fuel. Result of this study is that biomass is competitive with a price of 115€/t.

Transmission technologies will play a key role in any system employing widespread renewable resources for a common supply. Current transmission capacities between EU countries and to adjacent regions are entirely inadequate for transferring the quantities of electricity required for a complete renewable electricity supply. For example, the northern German grid would already be overloaded in the near future, if current plans for a massive realization of offshore wind farms would be realised without grid enforcements [IGW 01] [NDN 01] [BDH+ 03]. Capacity expansion should thus take into account the prospect of transmission over thousands of kilometers using the particularly appropriate high-voltage DC (HVDC) grid technology (s. also [ABB 01]).

The following treatment of transmission costs and losses assumes a HVDC capacity of about 5 GW. For the purpose of analysis, the city of Kassel near the geographical centre of Germany has been selected as the terminal point of the HVDC line. Costs of 60 €/kW for each of the converter stations at both ends of the line as well as 70 €/(kW 1000 km) for (double bipol) HVDC overhead transmission lines and 700 €/(kW 1000 km) for ocean cable have been assumed (s. also [Hau 99]). The relative transmission losses at full load are 4%/1000 km in the lines and 0.6% at each converter. The losses are greatly dependent on electrical loading and have been treated accordingly. The life expectancy has been conservatively estimated at 25 years for cost calculation purposes (more than 100 years lifetime is realistic for overhead lines [Wan 03]). An interest rate of 5% has been assumed, and the annual operating costs have been set at 1% of the initial investment
costs. With transmission line lengths assumed to require extended distances due to the inevitable geographic limitations of direct routes, a rated transmission capacity equal to the rated power of the wind and solar generators is employed. (The rated power of the transmission lines is about 50% below the thermal transmission limit, which is worth to be mentioned since it involves an inherent technical immunity against faults.) The same specific cost figures for the converters and the transmission lines as well as the interest rate and the computational lifetime are used for the individual scenario calculations.

Out of a solar surface potential of approx. 800,000 m2, a production capacity of approx. 80,000kWp, i. e. 80 Megawatt (MWp) can be derived with which a yearly electricity output of 67,000 MWh can be obtained.

From a yearly total electricity requirement of 506,000 MWh by the city of Fuerth, approx. 13 % of this could be covered by photovoltaic energy means.

Converted to the “current comparison” of households which have an average electricity consumption of approx. 3500-4000 kWh/a, approx. 14,000 to 19,000 households could be supplied with electricity from the sun.

The present installation capacity from all of the PV-installations in the urban area amounts to approx. 2000 kWp from which a yearly electricity production of approx. 1900 MWh is derived. In comparison to the total yearly requirement, the photovoltaic electricity currently produced in Fuerth accounts for 0.33% of the yearly requirement.

The solar energy potential

Out of a solar surface potential of approx. 800,000 m2, a production capacity of approx. 80,000kWp, i. e. 80 Megawatt (MWp) can be derived with which a yearly electricity output of 67,000 MWh can be obtained.

From a yearly total electricity requirement of 506,000 MWh by the city of Fuerth, approx. 13 % of this could be covered by photovoltaic energy means.

Converted to the “current comparison” of households which have an average electricity consumption of approx. 3500-4000 kWh/a, approx. 14,000 to 19,000 households could be supplied with electricity from the sun.

The present installation capacity from all of the PV-installations in the urban area amounts to approx. 2000 kWp from which a yearly electricity production of approx. 1900 MWh is derived. In comparison to the total yearly requirement, the photovoltaic electricity currently produced in Fuerth accounts for 0.33% of the yearly requirement.

The comparison shows that Fuerth, together with all municipalities in the nation are still standing at the start in the mobilization of the solar energy potential. It also highlights that decades of goal-oriented effort is necessary in advancing the potential to a relevant, energy-economical size.

Carbon trading markets in the US are at a pre-inception stage: those in Europe (including the forthcoming EU-wide scheme) are targeted at large industrial emitters. None as yet are specifically addressed at the construction sector. But there is good reason that they should: in the US, for example (fig. 3) CO2 emissions from commercial buildings have risen in the last decade faster than in any other sector.

Fig. 3: increase in US CO2 emissions by sector, 1990-2001.

Buildings — especially new buildings — have not been well represented to date in the UK trading system

• 90% of incentive money went to 10 organisations, mostly in chemical/petrochemical sector

• building-related projects were among the smallest in the first round (March 2002)

• one successful bidder: a group of building managers from 6 universities — at least one (Cambridge) has since dropped out, citing inflexibility of scheme

• most building-related projects for plant retrofit, CHP

• building sector participants anticipate non-financial benefits