Taking into account that in Athens the Public Power Corporation refers a mean yield of 30% per kWh between production and final consumption and that the production of each kWh causes CO2 emissions equal to 0.9 kg, (European Commission, 2001), the CO2 emissions, (in tn), caused by the total Athens’ heat island energy cost have been calculated. Finally, the ecological footprint of the Athens’ heat island, (in ha), is calculated by dividing the estimated CO2 emissions by the average world CO2 sequestration rate by the forests which is 5128.205 kg CO2/ha.

By considering that all buildings are air conditioned, we calculated, Table 5, the maximum potential ‘Athens heat island energy cost’ in kWh/m2, the maximum potential ‘total Athens heat island energy cost’ in GWh, the maximum potential CO2 emissions due to the total Athens heat island energy cost, in tn, and finally the maximum potential ecological footprint of the Athens heat island in ha.

As it can be observed, there is a remarkable potential energy cost of the urban heat island phenomenon in Athens ranging between 1300-1500 GWh/y, a very high potential increase of the CO2 emissions ranging from 4 to 4.6 Mtn. The calculated maximum potential ecological footprint because of the heat island effect varies between 780000 to 900000 ha.

Table 6 shows the actual Athens’ heat island energy cost, the actual total Athens’ heat island energy cost, the actual CO2 emissions due to the total Athens’ heat island energy cost in tn, and finally the actual ecological footprint of the Athens’ heat island.

References

Barett, J., and Scott, A.: 2001 ‘An ecological footprint of Liverpool: Developing sustainable scenarios’, Report for the Environmental Agency.

Geros, V., and Santamouris, M.: 1995, Summer-Building, Energy simulation tool,

University of Athens, Athens.

Hassid, S., Santamouris, M., Papanikolaou, N., Linardi, A., Klitsikas, N.,

Georgakis, C., and Asimakopoulos, D. N.: 2000, ‘The effect of the Athens heat island on air conditioning load’, Energy and Buildings 32, 131-141.

Hellenic Statistical Service : 1991, ‘Construction in Greece’.

Klitsikas, N. and Santamouris, M.: 1997, Final Report of the program ‘Sustainable Western Athens’, Association of the Municipalities of Western Athens.

Livada, I., Sant. amouris, M., Niachou, K., Papanikolaou, N., and Mihalakakou, G.:2002, ‘Determination of places in the great Athens area where the heat island effect is observed’, Theor. Appl. Climatol. 71, 219-230.

Mihalakakou, G., Flocas, H. A., Santamouris, M., and Helmis, C.: 2002,

‘Application of neural networks to the simulation of the heat island over Athens, Greece, using synoptic types as a predictor’, J. Appl. Meteorol. 41,

519-527.

Mi. halakakou, G., Santamouris, M., Papanikolaou, N., Cartalis, C., and

Tsangrassoulis, A. :2003, ‘Simulation of the urban heat island phenomenon in Mediterranean climates’, Pure and Applied Geophysics, In Press.

Psiloglou, V.: 1997, ‘Development of an atmospheric solar radiation model’, Ph. D. Dissertation, University of Athens, Physics Department, Athens, Greece.

Rees, W.: 1992, ‘Ecological footprints and appropriate carrying capacity: What urban economics leaves out’, Environment and Urbanisation 4, Part 2.

Santamouris, M., Mihalakakou, G., Papanikolaou, N., and Asimakopoulos, D. N.: 1999, ‘A neural network approach for modeling the heat island phenomenon in urban areas during the summer period’, Geophys. Res. Letters 26, 337-340.

Santamouris, M., Papanikolaou, N., Livada, I., Koronakis, I., Georgakis, C., Argiriou, A., and Asimakopoulos, D. N.: 2001, ‘On the impact of urban climate on the energy consumption of buildings’, Solar Energy 70, 201-216.

Simmons, C., and Chambers, N.: 1998, ‘Footprint UK Households : how big is your ecological garden?’ Local Environment 3, 355-362.

Wackernagel, M., and Rees, W.: 1996: ‘Our ecological footprint: reducing human impact on the Earth’, Gabriola Island, BC and Philadelphia, PA: New Society Publishers.

Wackernagel, M.: 2000, ‘Big things first: focusing on the scale imperative with the Ecological Footprint’ Ecological Economics 32, 391-394.

Mean Temperature, Mean Maximum Temperature and Cooling Degree Hours for the year 1997 and for the five experimental stations

Mean Temperature, Mean Maximum Temperature and Cooling Degree Hours for the year 1998 and for the five experimental stations

Table 5

The maximum potential Athens’ heat island energy cost, the maximum potential total Athens’ heat island energy cost, the maximum potential CO2 emissions due to the total Athens’ heat island energy cost in tn, and finally the maximum potential ecological footprint of the Athens’ heat island.

The actual Athens’ heat island energy cost, the actual total Athens’ heat island energy cost, the actual CO2 emissions due to the total Athens’ heat island energy cost in tn, and finally the actual ecological footprint of the Athens’ heat island.

As practical example the power supply of a telecommunication station (e. g. repeater) is shown in Fig. 1.

In the initial phase the supply is sufficiently maintained by a PV generator, a wind generator, battery and the central energy management. Now as time goes by, the demand for electricity is usually rising due to higher utilisation or added transmission equipment. In a standard hybrid system then the battery would need enlargement as well as PV generator and additional generator. This means downtime for the system and modification to the control. When adding UESP-capable components to an existing UESP system however, they can simply be attached to the power and communication busses and are instantaneously integrated.

Wind Generator Diesel Generator

Fig. 1: Simple UESP System for initial supply to telecom load

As can be seen in Fig. 2 the system is extended by discrete new components, while the existing components are still in operation. For the second battery a converter is required for parallel operation, allowing individual determination of State-of-Charge and State-of — Health as well as the combination of different battery types with complementing properties.

Using a ray trace, a suitable surface can be approximated by breaking it up into small facets where the position and orientation of one after the other can be sequentially optimised to achieve uniform illumination. Fig 2 shows this design process in which several facets are sequentially optimised. First the distance of a horizontal facet on the axis of symmetry is varied until the ray trace program calculates the wanted concentration or illumination on the surface within a given tolerance. Instead of optimising the position of the first facet for a given illumination or concentration, a position and orientation of the first facet can be chosen which defines the illumination and concentration for the whole uniformly illuminated surface.

Next, another facet is attached to the first facet with an arbitrary orientation. Now the orientation of the second facet is varied by turning it around the point in which it touches the first facet. For each variation a ray trace program calculates the average concentration or illumination on this facet. The facet is varied until the wanted value is

achieved within the given tolerance. Next another facet is optimised by turning it around the point where it touches the second facet. This procedure is continued until for a facet the maximum concentration is less than the wanted concentration and therefore no orientation can be found anymore for which the concentration or illumination is within the given tolerance. This defines the rim of the receiver.

The result strongly depends on the starting point. In principle it is possible to start at any point within the suitable region. For a symmetrical system it is reasonable to start along the symmetrical axis as shown in the example above to achieve a symmetrical result.

It is feasible to approximate the surface by small facets since a real photovoltaic receiver will be put together out of small flat solar cells too. It is sufficient to calculate the average irradiation on these facets since each cell produces electricity, which as well depends on the average irradiation over the surface of the cell.

Many ray trace programs using different principles are available or can be programmed which can be used for such an optimisation process. In a companion paper (Buie et al., 2004) another procedure for generating regions of uniform illumination is described.

To quantify the difference between the mismatch loss in partially shaded PV-modules connected in parallel and in series, experiments were conducted with nine modules alternately connected in parallel and connected in series. The measurements were done with the very same modules under virtually identical conditions, which excludes other influences on the array power than the mismatch effect.

Experiments were performed with 9 modules on sheds on a horizontal roof. The orientation of the sheds is depicted in figure 2. Figure 3 shows which 9 modules of the second shed were used for the experiments.

The 9 modules were chosen arbitrarily from the total set of modules and were not cleaned prior to the experiments. The modules have their original two bypass diodes (1 diode per string of 18 cells).

With a specially designed relay-switchbox the 9 modules were alternately connected in parallel and connected in series. During the measurement campaigns the IV-curve of the modules with the parallel connection and with the series connection were measured alternately. The pairs of IV-curves were used to calculate the corresponding pairs of maximum power point values.

Next to the PV-arrays some slim poles (5 x 6 cm) are situated with horizontal wires (6 mm). The width of the PV-cells is 12.5 cm. At the time of the measurements these poles cast a shadow over some of the 9 modules mainly in the morning period. In the afternoon this happens only sporadically. The wire always casts a shadow over the modules. The following picture shows the shadows on the modules at 10:40h. The shadow of the wire is too thin to be seen on the picture.

Figure 3: sketch of the shed with 9 x 4 modules.

The 9 modules chosen for the experiment are indicated with the dark-grey filling.

The results of the measurements on a sunny day (17/11/2003) are shown in figure 5. It shows that in the afternoon, when there is practically no shading, the parallel concept produces marginally more power than the series concept. However in the morning, when there is only little shading, the parallel concept produces significantly more.

Of course the difference between both concepts depends very much on the shading conditions and consequently no general conclusions can be formulated on the annual energy gain by the parallel concept. However the results do show that PV-systems in the built environment, which are virtually always subject to some shading, will profit by the parallel concept.

4 Accessibility

PV modules are poorly accessible when being part of a building. Usually scaffolding must be put up to replace defective modules. As this is costly it is good to consider what are the effects of a defect in the system.

Most PV-modules are equipped with one or more bypass diodes to prevent thermal destruction of cells due to hot spots in case of partial shading. Another function of bypass diodes is that failing modules in a string are bypassed and that the remaining modules of the string can still produce power. This situation however may lead to additional mismatch loss in the case of a central inverter with parallel strings. This is caused by the differences in the MPP voltage of the strings with a different number of active modules. It is also possible that the cabling that interconnects the modules fails. In these situations one failing module in a string results in the loss of the complete string. This happened recently in a Dutch BIPV system in which 6 modules out of about 400 failed. The modules were part of strings with a length of 13 modules. The 1.5% of failing modules resulted in a loss of 10% of the strings. Since energy loss of 10% was considered unacceptable the failing modules had to be replaced. Because of the low accessibility of the roof this could only be done at high costs. In case the strings would have been shorter (ultimately with a length of one module), the energy loss would have been acceptable and no repair would have been needed.

As in the previous two paragraphs this is merely an example of what can happen. It is hard to quantify the over-proportional energy loss on annual basis as averaged over all BIPV installed. Nevertheless it is recommended to use short strings in BIPV system due to limited accessibility for repairing.

It is also recommended to have a system layout that enables to mount the modules simply. An identical connection of all modules is preferred, favouring a fully parallel or series connection. In addition the mounting system must allow simple and easy installation and maintenance.

5. Consequences

In the previous chapters arguments are given for application of short strings in building integrated PV-systems. The arguments are based on the energy yield of the array. The effects of price, efficiency and reliability of the inverters were not taken into account.

The shortest possible string is a string consisting of one module. This leads to the parallel connection of many modules. Possible concepts for applying many modules in parallel are:

• All modules directly DC-connected via a low resistance cable to a central inverter (low voltage DC-bus). In the Wirefree concept [4] this cable is omitted by the dual use of metal strips for mechanical support and electrical connection.

• All modules equipped with their own module (AC-modules) with an AC-bus.

• All modules equipped with an individual maximum power point tracker:

— DC/DC module inverter connected to a high voltage DC-bus and a central DC/AC inverter

— DC/AC module inverter connected to a high voltage AC-bus and a central AC/AC inverter

6. Conclusions

In the design of a BIPV system it is necessary to take partial shading, especially at low altitudes of the sun, possible different orientations within the system and the chance of component failures into account. These factors lowering the energy output must be offset to the system cost, including engineering and maintenance cost.

In many cases a parallel connection of modules is favourable especially if it can be combined with lower component costs, such as the Wirefree concept.

7. Acknowledgement

This work was supported by the Netherlands Agency for Energy and Environment Novem (project number: 2020-02-11-11-003).

[1]

Russia’s entry into the EU bio-fuel market is going to be the basis for further co-operation, beneficial for all parties involved. While the EU gets the access to relatively inexpensive renewable energy source, the investments from the EU members would help Russia to develop the branch of renewable fuel industry creating workplaces in rural areas and to accumulate financial resources for implementation of the new efficient biomass conversion technologies and energy bio-products transportation. It is supposed that wood biomass based energy production requires several times more workplaces per energy unit than that using conventional petroleum derived fuels [9]. Since unemployment in the Eu countries is also a serious problem, a certain number of workplaces in biofuel industry should be created there. However taking into account enormous difference of salary rates in Russia and the EU, it is advisable to perform most of labour-demanding operations in rural areas of Russia.

By contrast, if interregional transmission is not allowed in a restrictive decentralised scenario, excess production increases significantly to 10% of the production, and additional backup power as well as backup energy employing other resources become necessary within individual isolated regions to meet the demand, leading to great additional expenses. In one scenario, fuel cells powered with renewable hydrogen produce electricity at about 20 €ct/kWhel (which is already quite optimistic if the hydrogen is produced from renewable energies), raising the net electricity costs to over 8 €ct/kWhel on the average. For Region 6 (Germany and Denmark), this restrictive "decentralized”

(insular) strategy would lead to costs of electricity greater than 10 €ct/kWh.

• 6.3 Scenarios with Reduced Costs for Individual Components

The effect of cost changes for individual technologies and components was also investigated in particular scenarios. This was used to find the costs at which PV could cost-effectively contribute to the supply. A major cost reduction for PV equipment would
enable this technology to provide a significant contribution to the electricity supply. If all other costs remained the same, a reduction to one-eighth of current PV costs would enable an economically viable 4% contribution to overall electricity generation to be provided. The generation would nevertheless be limited to the southernmost regions — particularly to regions 12,16, 17, and 18. If the cost were only one-sixteenth of present levels, PV technologies could account for about 22% of all electricity generation, reducing generation costs compared with the base case scenario by about 10% to 4.3€ct/kWh.

Even in this case, however, photovoltaic technologies would not be used in the northern regions 1, 2, 3, 6, 9, and 19, because they could not contribute to overall cost reductions.

If the costs of the mirror fields of solar thermal power plants were reduced by half — as is anticipated in the near future — solar thermal plants would already constitute about 13% of all electricity generation. In this case, the electricity costs lie at 4% below those of the base case scenario. Reducing the costs of the collector array to 40% and simultaneously lowering storage costs to two-thirds of current levels (still clearly above achievable storage costs according to the recent research mentioned above) would increase their contribution to 28% of the electricity produced, while the electricity generation costs would fall by about 10% to 4.3 €ct/kWh. These examples illustrate that solar thermal generation presents an economically attractive perspective for the future that can be realized fairly easily in view of minimal cost regression factors.

1.1 Holistic research groups

The work is divided into thematic research and demonstration buildings. The information source to be used in the thematic groups is mainly the demonstration buildings that will be built in the participating countries. The information collected from each building will be used as input to the conclusions of the different groups. Each thematic group will address the Northern Dimension and the corresponding problems throughout their work and produce first concrete recommendations for future BIPV projects. Dutch partners will share their experience from the last ten years working with BIPV exploitation and development.

Five Thematic Areas have been identified corresponding to five important barriers to BIPV exploitation. These Areas are grouped into the following two Work packages:

Work packages 1 and 2 represent the co­ordination and dissemination of the project, respectively. The partners in WPs 3 and 4 represent different interest groups in PV exploitation, so as to form holistic and multi­knowledge groups, capable of addressing the barriers from different angles and perspectives. The Task

Leaders are responsible for leading the discussions, compiling results and

administrating all work in relation to each respective area.

Each group has the freedom to develop the contents of their work, but will follow a general work design. The groups will utilise the knowledge and experience that the

participants have developed through years of work in the area, from participating in EU-funded and national projects and networks, and so on. They are analysing each building of the project, both by studying material on solutions and technology, and by visiting the buildings. The fact that all involved participants represent or work in the construction industry is a guarantee that all information developed will be concrete and directly usable in the design, development and planning of PV installations in the Northern Dimension. All results will be disseminated in the Northern Dimension, e. g. in the form of written material or open spreading of information.

The outcome of all tasks will be recommendations on design of BIPV in future buildings and lessons learned from the PV — NORD demonstration projects.

1.2 Task 3.1 Aesthetics and PV Integration

Task 3.1 Aesthetics and PV Integration will

review the architectural solutions and the integration methods applied in each building project. Background information regarding the planning process is of great interest as many BIPV projects are stopped already in a very early stage due to negative opinions from city planners or other decision-makers involved. It is valuable to see early architectural sketches in order to follow the development to the final design. Aesthetics and PV integration is closely interrelated factors. Examples are climate (e. g. snow, ice, heavy rains) and sun inclination (e. g. double function shading), which affect the design and reflect on the characteristics of the installation.

1.3 Task 3.2 Environment

Task 3.2 Environment is dedicated to the very important issues regarding materials used in the solar cells and other parts of the PV installations. The concept of Building Integrated PV should include that the solar cells are considered an energy source AND a building component similar to e. g. roof tiles, bricks or concrete. Compared to other EU-countries, Northern Europe has advanced greatly in the area of environmental legislation and norms and their implementation: These are to be taken into thorough consideration in PV-NORD.

1.4 Task 3.3 Power and Electricity

Task 3.3 Power and Electricity addresses the electrical design in each demonstration project. Which system voltage is selected, how can the connection of modules be solved, what about grounding, lighting and over voltage protection, what are the criteria for selecting inverters, are some examples of relevant issues. Safety is of course a high priority, as are the relevant electrical codes and installation recommendations. The connection to the utility grid will also be part of Task 3.3.

1.5 Task 4.1 Financing and Ownership

In Task 4.1 Financing and Ownership different financing solutions are evaluated. Subsidies might come from national or municipality programmes or in the form of rate-based incentives and so on. Several of the new innovative financing solutions such as BOOT (Build, Own, Operate and Transfer) and

different financing partnership constellations could be transferred to the BIPV sector. The ownership of the PV installations can also vary from each flat having its own system or belonging to a co-operative tenants-owned building society. In some cases the local utility company is the owner. Different solutions also have varying effects on taxation.

1.6 Task 4.2 Management and ICT Task 4.2 Management and ICT (Information and Communication Technology), finally, focus on how operation and maintenance of the PV systems is solved in the different demonstration buildings. Particular emphasis is put on the use of tools based on modern information technologies, ICT. In the Swedish buildings (Holmen/Grynnan and Lysande, see below) a local Intranet will be installed and IT will be a general tool for the surveillance of the buildings. The tenants will have access to data showing their energy consumption and it is foreseen that also monitoring of the PV installations will be included. For example, the Ekoviikki demonstration building (Finland) will involve advanced ICT for control of the PV installations in cooperation with the regional utility company. Advanced information technology solutions will be demonstrated where the production and consumption of PV energy would be constantly monitored and controlled. The tenants will even have access to real-time updates through the Internet or a mobile phone.

Jyoti Prasad Painuly

UNEP Risoe Centre on Energy, Climate and Sustainable Development, Risoe National laboratory, DK-4000, Denmark, email: j. p.painuly@risoe. dk

and

Eric Usher

Energy and Ozon Action Unit — Division of Technology, Industry and Economics — United
Nations Environment Programme, 39-43 quai Andre Citroen, 75739 Paris, email:

eric. usher@unep. fr

Abstract: Renewable Energy is expected to contribute significantly in future to World Energy Supply. It holds tremendous potential for countries like India where approximately seventy percent of the rural households are still without access to electricity. These households continue to rely on less efficient and polluting energy sources, typically biomass for cooking and heating and kerosene for lighting. Even when connected to grid, problems of capacity shortages and inconsistent quality plague the power supply, especially in rural and semi urban areas in most parts of India. Despite high initial costs, Solar Home Systems (SHS) emerge as an attractive option in the context of costly or unreliable alternatives and escalating grid power tariffs. Barrier to the growth of SHS market include a lack of access to financing, awareness, and risk perception associated with the technology, new to the customers of SHS and financing community. Consultations with stakeholders were held and an intervention was designed to address these barriers through creation of a credit facility in partnership with two banks having wide reach to the potential customers. The facility provides loan to the customers and a small subsidy to buy down high cost of the credit, which is designed to reduce over the three-year operation of the facility, with a target to reach market rates of interest at the end of the project. Technical support, awareness raising strategies and training were included as a part of the overall strategy. The credit facility was launched between April and June 2003 by the two banks. Early indications on sales have been very encouraging and the facility is expected to surpass the target of 5000 SHS sales in two years well in advance. Feedback mechanisms such as customer surveys, new initiatives to reach the poor households, and ongoing consultations with stakeholders etc. are also part of the market development strategy.

1. Introduction

Renewable Energy (RE) is expected to contribute significantly in future to World Energy Supply. Though estimates vary, studies indicate significant growth potential for renewables, particularly in scenarios where environmental constraints are imposed, for example on CO2 emissions. According to IEA estimates, a scenario that considers new energy and environment policies in OECD countries, the share of renewables could reach 25 percent by 2030 (IEA, 2002).

The implication of the growing share of world energy needs mean RE can be expected to have a substantial share of energy sector investment which in total is estimated to be US$16 trillion over the next 30 years, 60% for the electricity sector alone. This is three times the amount invested in the last 30 years, and is due to the expected doubling of global electricity demand. The investment potential is huge even if renewables were to
capture only 3-5% of this market. According to IEA (2002), globally installed renewable energy capacity is expected to more than double over the next ten years from approx. 130 GW in 2003 to 300 Gw in 2013. Renewable energy is thus a multi-billion dollar industry and the most dynamic sector of the global energy market.

Among the developing countries, India has been at the forefront of RE development with a full-fledged Ministry of Non-Conventional Energy Sources (MNES) dedicated to the promotion of RE. The MNES Policy Statement on Renewable Energy includes meeting minimum rural energy needs, providing decentralised / off-grid energy supply for agriculture, industry, commercial and household sectors in rural and urban areas; and, generating and supplying quality grid power. The medium-term goals, to 2012, include 10% of new power capacity addition from renewables, progressive electrification by renewables of; 18,000 villages in remote areas, deployment of five million solar lanterns, two million solar home lighting systems, and one million solar water heating systems in the household segment (MNES, 2002-03 and IEA, 2001).

With approximately seventy percent of rural households still without access to electricity in India, less efficient and polluting energy sources — typically biomass for cooking and heating, and kerosene for lighting — are used in rural areas, with an adverse impact on the health and economic development of the users, as well as the environment. Even when connected to the grid, problems of capacity shortages and inconsistent quality plague the power supply, especially in rural and semi urban areas in most parts of India, including Karnataka. This has led households to look to alternative power supply systems such as inverters, diesel generators, and solar PV systems. But use of solar PV systems is on a very small-scale due to several barriers.

Concentration of sunlight onto photovoltaic cells, and the consequent replacement of expensive photovoltaic area with less expensive concentrating mirrors or lenses, is seen as one method to lower the cost of solar electricity. However, only a fraction of the incoming sunlight striking the cell is converted into electrical energy. The remainder of the absorbed energy is converted into thermal energy in the cell and may cause the junction temperature to rise unless the heat is efficiently dissipated to the environment. The major design considerations for cooling of photovoltaic cells are listed below:

— The cell temperature generally needs to be kept below ~60°C and should never exceed ~100°C [1].

— The cells should be kept at a uniform temperature [2, 3].

— The cooling system should be reliable, simple and low-maintenance.

— The total energy output of the collector is increased if the thermal energy can be used, for example as domestic hot water or low temperature process heat [4]. This makes it desirable to have a cooling system that delivers potable water at as high a temperature as possible.

— The power required of any active component of the cooling circuit is a parasitic loss to the system [4], and should thus be kept to a minimum.

— Materials use should be kept down for the sake of cost, weight and embodied energy considerations.

1.1 Concentrator geometries

The requirements for cell cooling differ considerably between the various types of concentrator geometries (Figure 1). In small point-focus concentrators, sunlight is usually focused onto each cell individually, so that each cell has an area roughly equal to that of

the concentrator available for heat sinking. Single cell systems commonly use various types of lenses for concentration. Line focus systems typically use parabolic troughs or linear Fresnel lenses to focus the light onto a row of cells. In this configuration, the cells have less area available for heat sinking because two of the cell sides are in close contact with the neighbouring cells. In larger point-focus systems, such as dishes or heliostat fields, the receiver generally consists of a multitude of densely packed cells. This arrangement presents greater problems for cooling than the two previous configurations, because, except for the edge cells, each of the cells only has its rear side available for heat sinking. This means that, in principle, the entire heat load must be dissipated in a direction normal to the module surface, which generally implies that passive cooling can not be used in these configurations at their typical concentration levels.

The system was planned and constructed during the first half of 2003. The system has been operating since September 2003. In autumn, 2003, comprehensive measurement equipment with automatic daily data transfer to Fraunhofer ISE was installed.

The most important measurement data are also presented in parallel to visitors on site with a graphical presentation. The complete data acquisition system commenced operation on 1st December, 2003.

Figure 5 illustrates how the fuel cell fills the gaps in the power supply when the wind is weak and there is no solar radiation. Wind and sun complemented each other very well on this day.

3. Outlook

As well as modernising the power supply for the "Rappenecker Hof", another goal of this project is to use and demonstrate fuel cells in off-grid systems. It is important that fuel cells are applied in real systems under field test conditions now, in order to provide valuable information for their further development. In addition, it is intended to demonstrate the technology in the system to the general public. An innovative battery system is a further technological highlight of the new hybrid power supply.

The system consists entirely of commercially available components, with the aim of determining the extent to which the market can already provide the technology needed. The two-year test phase will concentrate on systems-technological optimisation of the individual system components. The comprehensive measurement technology installed ensures that particular questions can also be studied in detail.

Modernisation of the power supply for the "Rappenecker Hof" was possible as a result of funding from the innovation fund for atmospheric and water conservation of the utility, badenova AG & Co. KG in Freiburg. The project partners, the Riesterer family from Oberried, Phocos AG-Deutschland from Illerkirchberg and the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg also contributed with substantial sums toward the financing of this project.