The above mentioned collected climatic data were used to calculate the cooling load of a representative, (reference), building for five experimental stations selected from the 23 stations described in chapter 2, (numbered 2, 7, 9, 13, 14). Station numbered 2, as already mentioned, is the reference station while the remaining four experimental stations were placed in the central area of Athens and can be regarded as urban stations. The average values of any parameter characterising these four stations are attributed to a station mentioned as "urban”. Urban stations have been selected after a detailed statistical analysis of all the collected data from the 23 stations. Analysis has shown that it is possible to group them according to different climatological criteria, (Livada et al, 2002). Based on this analysis five representative stations have been selected to be considered in the present study.

In order to satisfy all possible scenarios regarding the buildings’ height in the centre of Athens, the thermal behaviour of a reference building with a. one single floor, b. two floors,

c. three floors, d. four floors, and e. five floors, has been calculated. This building is considered to be representative of the Athens’ buildings. Definition of the representative residential building in Greece, has been performed through a detailed collection of data on residential buildings. The survey included data for more than 1000 residences located in the Western Athens Area and was performed in the frame of a major research program aiming to improve the energy and environmental quality of the region, (Klitsikas and Santamouris, 1997). In parallel, the design of the reference building is according to the statistical data collected for all residences in the country, (Hellenic Statistical Service, 1991). Thus, the average cooling load, (in kWh/m2), of the reference building was calculated for the whole summer period, (1st of May to 30th of September), of the years 1997 and 1998 using the SUMMER BUILDING energy simulation program (1995). Each
floor has an area of 200m2 in square shape. The vertical envelope of each floor is made of double brick with an air gap between the two brick layers and external insulation, in a percentage of 90% and of a concrete layer with external insulation in the remaining 10%. A description of the reference building is presented in Table3.

Simulations of the thermal behaviour of the reference building and calculations of its cooling load for the whole summer period for both years, 1997 and 1998, have been performed using hourly data of the ambient temperature collected at the selected five experimental stations presented in chapter 3. As mentioned,

The same solar radiation data have been used for all stations as a non-significant spatial variation regarding solar radiation values has been observed in Athens (Psiloglou, 1997).

Table 4 shows the mean electrical cooling load in kWh/m2 for the selected five stations as calculated using the measured climatological data for the years 1997 and 1998 The air- conditioner is assumed to be a PTAC air-conditioner with no fresh air input and an electric input ratio EIR of. 0.438 at ARI-rated conditions COP 2.25 . The calculated values are very close to the cooling loads reported by Hassid et al, (2000), for the same period as well as with data collected through different monitoring campaigns. The impact of the different parameters affecting the cooling load of the buildings like the set pint temperature, the cooling schedule, the air flow rate, and the orientation of the building has been studied and reported in details in a previous paper, (Hassid et al, (2000), and will not be repeated here.

We define as heat island energy cost, the difference between the urban station’s cooling load, which is the average value of the central stations’ cooling loads, and those of the reference one. The average heat island energy cost was calculated close to 33.2 kWh/m2 for the year 1997 and 29 kWh/m2 for the year 1998

The idea behind the Universal Energy Supply Protocol (UESP) is to equip all components (all kinds of generators, batteries and loads) with an identical and well-defined electrical DC connection as well as with intelligence and a communication interface, speaking a defined protocol (called UESP). Power flow and information flow are separated, leading to more flexibility in system sizing and standardisation. A centralised control and energy management system administers the system as a whole. Its software is able to manage the energy generation and consumption and ensures the required level of reliability while reducing the operational cost to a minimum. Therefore fuel costs, ageing effects and maintenance costs are taken into account when calculating the optimal operation strategy. In contrast to existing management concepts, the UESP approach is to source out the intelligence and the knowledge on the operational behaviour and cost of the components from the central management system into the components themselves. The components provide information about their current status of operation, current and future operation cost and constraints to the central management system. Here, using virtual stock exchange algorithms, an optimised schedule for all components is determined and fed back to the components for implementation. The central management is thus very generic and can handle any component using the UESP protocol. It automatically adapts to new or changed system configurations, as these changes impact the optimisation only by additional players on the virtual stock market. This allows the mentioned “Mount-and — forget” concept throughout the system, meaning that no adjustment and special programming needs to take place whenever components are attached or removed. Based on results from the provided planning tool, the hybrid system can grow flexibly with the energy demand.

At any location between the optical concentrator and the target of the concentrator or behind the target point (focus) it is possible to define an orientation of a surface which yields the maximum illumination for this location.

Fig. 1 shows the distribution of the maximum achievable concentration of a solar beam with the parameters described by Buie et al. (2003) for a paraboloidal dish which has a diameter of four times the focal length, which means that the focal point lies in the same plane as the rim of the dish. This plane shall be called the focal plane for which in Fig. 1 z = 0. For almost all positions the maximum concentration can be achieved for a receiver surface element orientation normal to the radiation reflected from the dish. Due to end effects, this is only for such positions well below or above the focal plane. In the following, we will show that the isolines in Fig. 1 form a parabola. z

0.00 -0.01 -0.02 -0.03 -0.04 -0.05 -0.06 -0.07 -0.08 -0.09 -0.10

-0.11 A /’ /

Fig. 1 shows the position and orientation of several area elements with an concentration of about 400 suns. Each element is normal to the radiation reflected from the dish and therefore would be tangential to a sphere with a radius equal to the distance of the area element to the focus. It can be seen that the area elements with maximum equal concentration do not add up to a smooth, continuously differentiable surface. Therefore, it is not possible to find a continuously differentiable surface with uniform illumination, which achieves the maximum concentration at each point in space.

At each position in space the illumination on a surface can be reduced to any arbitrary concentration value below the maximum concentration at this position by changing the orientation of the surface. The relation between orientation of the surface and concentration can be described by following equation:

C( x, y) = Cmax( x)cos(y) Eq.(1)

with Cmax(x) as the maximum achievable concentration at the location X and у the angle between the normal of the orientated surface and the normal of the surface of maximum concentration.

Therefore, for a specific desired illumination level there must be a region that is defined by the fact that, along the perimeter of said region, the maximum illumination is equal to the desired illumination. The perimeters for specific concentration values are shown in Fig. 1. Within such a perimeter, at every point a surface can be constructed that will have at least one orientation with the wanted illumination. An almost symmetrical region lies behind the target.

If the concentrator or radiation source creates an illumination field which is continuously differentiable throughout the aforesaid region, there must logically exist at least one continuous surface which has the property of uniform illumination. This surface can be analytically or numerically calculated if the amount and direction of incoming radiation is known at every point.

To quantify the performance effect of multiple orientations within one PV-array, performance calculations were carried out for a rather extreme situation: a house with a double-sided roof facing east and facing west (both slopes 45°). The calculations were performed with PVSYST V3.21 [7] for a sunny summer day in the Netherlands (52° north latitude). The results are given in figure 1. This figure shows the in plane irradiance on the two array parts, the sum of their individual maximum power values and the maximum power value of both parts connected in parallel. The figure shows that parts of an array with different orientations can be connected in parallel without a significant loss of power. From this it can be concluded that multiple orientations within one PV-array are acceptable as long as the modules within a string have the same orientation; the parallel strings may have different orientations. The effect of multiple orientations of modules within a string has not been modelled since it is common practice to avoid these situations.

Low price of plant biomass. In Russia, plant derived biomass is inexpensive enough to cover transportation costs for high-tech fuel and power products. For instance, the average price for wood sawdust from woodworking factories is about 5 Euro/MWh. In the assumption that the price of wood pellets produced of sawdust is even twice as much as that of a raw stuff, it would not exceed 10 Euro/MWh (i. e., thrice as low as in Austria where it is about 30 Euro/MWh [8]). As for prices for agricultural wastes such as straw, they are usually reduced to those of collection and transportation.

Cold climate. Most of Russia’s forestry resources and arable lands are situated in areas with cold climate where heating period lasts to over 7 months. As biomass preparation and/or conversion normally require certain thermal treatment operations, relatively high quantities of heat and/or hot water can be obtained as by-products. For instance, considerable part of heat spent on drying vegetable feedstock or pyrolysis of biomass can be then used for domestic and municipal heating and hot water supply thus reducing overall costs in this branch of economy.

Low price of manpower. Manpower in Russia is manifold lower than in EU states.

For example, average salary in agriculture is approx. 45 Euro per month and that of very skilled workers of industrial enterprises typically amounts to not more than 200 to 250

Euro/month. Obviously, even with relatively high (compared with the average national level) salary rates in biomass collection, storage and conversion industries, manpower cost would be within rather moderate EU range.

Low employment in agriculture and local industries provides an opportunity to easily stuff local enterprises involved in plant biomass production, primary treatment, conversion and preparation for transportation.

Relatively high level of expertise of a number of local industrial enterprises, particularly those that were earlier involved in the defence industry infrastructure. These enterprises have qualified stuff of engineers and workers capable of designing and manufacturing complicated biofuel related technological processes and equipment.

Technological solutions related to biofuels and their use have been found by Russian researchers making it possible to achieve higher efficiency of biomass conversion into biofuels, particularly for transport application which are waiting for investors into this sector of renewable energy business. After their implementation in relevant technological equipment these technological solutions could make biofuel flows from Russia to the EU much more profitable and safe.

The Institut fur Solare Energieversorgungstechnik (ISET) in Kassel has been developing scenarios for a future electricity supply entirely with renewable energies. Various concepts have been studied for providing renewable energies to Europe and neighbouring regions.

An extensive region (s. Fig. 9) with approx. 1.1 billion inhabitants and an electricity consumption of roughly 4000 TWh/a has been analysed to determine the available potentials for a future energy system. This process has taken into account ECMWF data as the meteorological basis and the population density as a restrictive factor for the wind energy potentials or estimated roof areas in all countries within the shown regions for determining the roof top photovoltaic potentials, combined with data on solar irradiation (ECMWF and NCEP/NCAR), wind speeds, and also temperatures used e. g. for photovoltaic electricity production and for solar thermal electricity production. Also other renewable resources such as biomass and hydropower have been investigated or included at the level of current knowledge. Mathematical optimisation routines have been applied to the question of which renewable resources with their individual temporal behaviour at different sites and with different yields should be used, and how selection should be made to achieve optimum cost performance. (A linear optimisation with roughly 2.45 million restrictions and about 2.2 million free variables is employed to find the best combination in each scenario.). The optimisation takes into account the temporal behaviour of the combined consumption of all countries within every individual region shown in Fig. 9 as well as all requirements imposed by resource-constrained production. Both sets of data, electricity demand and

temporal behaviour of the possible production, have been compiled for optimisation (using time series with three-hour intervals) for all of the 19 regions to be supplied. The optimisation process ensures that supply will meet demand at any time, while determining if and to which extent any potential source is to be used, and how every part of the supply system will operate, including the dimensioning and operation of a HvDc grid that is superimposed on the current grid infrastructure. The criterion of optimisation is the minimization of overall annual costs of electricity when fed into the regional high-voltage grids, enabling these costs to be compared directly with those from regular power stations feeding into the conventional AC-high-voltage grid. However, the economic optimisation of all power plant operations for a time frame greater than, or equal to, three hours has simultaneously been included using sets of time series extending over one year.

• 6.1 Base Case Scenario

The promising results for the base-case scenario — which assumes an electricity supply system implemented entirely with current technology using only renewable energies at today’s costs for all components (s. a. [Czi 01]) — indicate that electricity could be produced and transported to the local grids at costs below 4.7 €ct/kWh, which hardly differs from the case of conventional generation today. (At gas prices in 2002 of about 2.4 €ct/kWh for industrial consumers in Germany [EC 04], electricity from newly erected combined-cycle gas power stations had already reached significantly higher 5 — 6 €ct/kWhei.) In this scenario, nearly 70% of the power originates from wind energy produced from wind turbines with a rated power of 1040 GW. Biomass and existing hydroelectric power plants provide most of the backup requirements within the supply area, in which the individual regions are strongly interconnected via high-capacity HVDC transmission lines. Electricity is generated from biomass at 6.6 €ct/kWhel after proceeds from heat sales have been factored in. This result lies significantly above the average price level, yet the backup capability is essential to reduce the overall cost of the entire system. About 42% of the electricity produced is interregionally transmitted via the HVDC-System whereby the total transmission losses sum up to 4.2% of the electricity produced. Another 3.6% loss is production which neither can be consumed at the time it is produced nor be stored for later use within the pumped storage plants and therefore is produced in excess. These two losses may be considered quite acceptable for an electricity supply only using renewable energies.

Dan Engstrom, NCC Engineering

NCC Construction Sverige AB, SE-405 14 Goteborg, Sweden
Phone Int. + 46 31 771 50 53, Fax Int. + 46 31 15 11 88, dan. engstrom@ncc. se

This paper summarises PV-NORD, an EU project on building integrated photovoltaic systems. In Northern Europe, the harsh climate, low energy prices and conservative construction traditions have limited the use of grid-connected PV systems in buildings. Too little attention has been paid to the fact that building integrated photovoltaics (BIPV) is the only high quality renewable source of electricity possible in an urban environment. Based on the EU White Paper, the purpose of PV-NORD is to catalyse the development of BIPV in Northern Europe and to provide the necessary knowledge and direct demonstration to put BIPV on the agenda of the coming years’ energy planning.

The partners represent different interest groups in PV exploitation, and form multi-knowledge groups, addressing the barriers from different angles, based on eight demonstration buildings in the participating countries. The thematic research is organized into five tasks: Aesthetics and PV integration, Power and electricity, Environment, Management and IT, and finally Financing and ownership. In this paper, the potential of BIPV is demonstrated by the PV-NORD building Kollektivhuset, central Copenhagen. This is a fagade renovation project for a multi-storey housing block for handicapped tenants. The photovoltaic modules are mounted in the glazed balcony parapets with a coloured sliding panel behind. This panel can be slid so as to utilise the heat from the PV modules or block the radiating heat from entering the balcony. The modules thus have multiple functions: as radiators for the balconies, as sound insulation, as electricity generators and aesthetically as dynamic fagade elements.

1. Introduction

Today, there are practically no Building Integrated PV (BIPV) projects in Northern Europe. A harsh climate, low prices of energy and conservative construction traditions have limited the use of grid-connected PV systems in buildings. The existing energy systems vary greatly between the different countries, and include both cheap energy from non-fossil fuels like hydro and nuclear power stations, and extensive use of fossil fuels. Traditional industries are typically dependent on high electrical demands and a large part of the building stock is heated by electrical energy. In fact, Sweden and Finland have Europe’s highest electricity consumption per inhabitant!

However, there need not be a conflict between these facts and BIPV. By using energy savings and BIPV, the need for external electricity supply will be reduced. Thereby more renewable energy is provided on the electricity market to substitute more of the fossil fuel. Nordic electricity is still to a large extent being produced by fossil fuel and the possibility to
extend hydropower has almost been exhausted. This is why BIPV is one of the technologies next to move the energy sector towards a sustainable situation.

By focusing so much on the relative high electricity price from BIPV as is the case now, too little attention is being paid to maybe the most important fact:

BIPV is the only high quality (electricity) renewable energy source possible in an urban environment, where an ever — increasing share of our total energy consumption is taking place. If BIPV is not introduced now, we miss a whole generation of renovation and new building projects, which in the future are likely to be very expensive to provide with aesthetically and technically good BIPV solutions.

In reality there is not a large resistance against BIPV. But as long as we only compare the direct electricity prices per kWh, without taking into account all externalities, added values and potential risks in lack of planning for
future use of solar energy in our cities, no changes can be expected to happen.

In order to fulfil the goals of the EU White Paper on an increased use of renewable energy in Europe, it is of great importance that the development of BIPV also takes part in Northern Europe. In the Netherlands it has been shown how the market for BIPV, in only a few years, has been exploited on a large scale with single projects in MW-sizes being realised.

The project PV-NORD, or Widespread Exploitation of Building Integrated Photovoltaics in the Northern Dimension of the European Union, aims to remedy this. The purpose of this project is to catalyse the development and to provide the necessary knowledge and direct demonstration to put BIPV on the agenda of the energy planning in North European countries.

The main objective of PV-NORD is to create conditions for a widespread exploitation of BIPV in the Northern Dimension (i. e. the policy of the EU for work in the North, within the EU and with its neighbours). The project will run for three years, during which time almost 200 kWp will be realised in eight pilot PV systems in Nordic countries and the Netherlands. This will pave the way for at least 5 MWp of grid — connected PV to be installed or planned in Sweden, Finland, Denmark and Norway.

The current situation is that Sweden, Finland and Norway together have less than 150 kWp of BIPV projects whereas Denmark through their "SOL 300" program started in 1998, have reached almost 1 MWp. As a comparison to
this, the Netherlands expects to achieve over 50 MWp before 2005.

The goal will be reached by:

• Demonstrating the potential of BIPV in eight prestigious buildings in the Nordic countries and the Netherlands.

• Identifying and preparing for a removal of the main barriers that hinder a larger penetration in the countries in this region. We are already aware of many of these barriers but through co-operation between the involved countries we will have better possibilities to move forward.

• Making it possible to eliminate large parts of these barriers through first preparation of concrete instructions and tools, first dissemination to relevant target groups etc.

From the foregoing, the role and importance of renewable energy in sustainable development and poverty alleviation in rural areas is evident. Renewable energy sources have the potential to fire up or to improve rural economies with greater effects in transforming rural livelihoods. A number of applications of renewable energy sources at household level require only some minimum resource utilisation to be effected. These include solar cookers for food preparation and water sanitization or heating which can be made with easily locally available and more affordable materials.

Another example is the use of fireless cookers, which again would require easily available and affordable local materials. These simple examples offers some wonderful opportunity for the poor people in rural areas to utilise renewable energy with resultant reduction in their energy cost while conserving environment and reaping benefits of clean energy. Abundant sunshine all year round in most of the rural areas provides greater opportunity for utilization of solar energy.

Opportunities for renewable energy technology in poverty alleviation and sustainable development among poor people in rural areas are enormous. Just as the mobile telephony has spread fast and widely in Kenya, there is also great potential for the renewable energy technology to take effect in rural areas of Kenya fast and widely. A number of opportunities exist for application of solar and wind energy among the rural folk and include the following:

1. Solar Energy Applications: (a) Industry e. g

Agricultural-based processing

Cottage industries —

Clothing

Embroidery

Knitting

Weaving

Leather works

Printing

Pottery

(b) Community centre: Amenities like IT-computer

Internet

Email

Telephony services

Radio

TV

Video/DVD

Learning/education resources

Social and entertainment facilities e. g games, sports

(c) Household — Use of solar panel Lighting

Water heating Water sanitization Cooking

Home radio/TV/Video games

Household appliances:-laundry, ironing, microwaving, cold storage/freezers etc

2. Wind

Applications:- Water pumping for Irrigation & other uses.

Recommendation

Given the large number of people living in rural areas needing usage of renewable energy services, strategies focused on reaching as many households as possible stand a great chance of success to be taken up and to provide a return on investment.

The opportunities to invest in renewable energy technologies in these areas could therefore be achieved through support targeting self-help groups within communities and also targeting whole communities. Credit schemes mechanisms need to be development whereby individuals or groups might be provided with specific renewable energy technology items, which they would then repay with time. The schemes could involve training and development of marketing co-operatives for products made from the applications of renewable energy technologies.

Rural Friends Kenya as a southern development organisation welcomes such partnerships with Northern partners to initiate renewable energy projects on pilot and scaled-up bases.

Ania Rovne. Christopher J. Dey and David R. Mills

School of Physics A28, University of Sydney, NSW 2006, Australia
Telephone: +61-2-9351 5980, Fax: +61-2-9351 7725, E-mail: royne@physics. usyd. edu. au

Abstract — Cooling of photovoltaic cells is one of the main concerns when designing concentrating photovoltaic systems. Cells may experience both short-term (efficiency loss) and long-term (irreversible damage) degradation due to excess temperatures. Design considerations for cooling include low and uniform cell temperatures, system reliability and sufficient capacity for dealing with "worst case scenarios", and minimal power consumption by the cooling system. This paper presents an overview of various methods that can be employed for cooling of photovoltaic cells. It includes a brief review of cooling alternatives found in other fields, namely nuclear reactors, gas turbines and the electronics industries. Different solar concentrators systems are examined, grouped according to geometry. The optimum cooling solutions differ between single-cell arrangements, linear concentrators and densely packed photovoltaic cells. Single cells typically only need passive cooling even for very high concentrations. Densely packed cells rely on active cooling in all cases.

1 Introduction

In general, the battery is responsible for 20 to 40 % of the total life cycle costs of a PV hybrid system. This is the largest individual item. These costs can be reduced only if intelligent operation management clearly extends the battery lifetime. Therefore, a battery concept was developed for the "Rappenecker Hof", which allows several parallel battery strings to be operated independently of each other. By this it is possible to disconnect individual strings from the load in order to allow full charging. This is an essential process for a long lifetime. Meanwhile other strings continue to supply power to the load. Energy is distributed among the battery strings via a DC/DC converter in the most favourable way for the lifetime of the complete system.

As part of the new concept for the PV hybrid system at the "Rappenecker Hof", the former 162 V system was reconfigured into three parallel 48 V strings, each with 24 cells. Each of these strings has a capacity of 200 Ah. The electrical demand due to the restaurant at the "Rappenecker Hof" has increased over the past few years, so that the battery has become too small. This unbalanced relationship between energy consumption and storage capacity resulted in one complete charging cycle each day, and thus to premature ageing of the battery. The three 200 Ah strings have been supplemented with an additional string employing the same OPzS technology and a capacity of 420 Ah. These four strings can be operated in parallel without difficulties despite their different ageing conditions by using the battery management system (BMS) developed at Fraunhofer ISE.

The block circuit diagram in Fig. 4 shows the concept of the battery management system. Each battery is connected separately to the BMS. The current, voltage and temperature of each string is recorded. The total battery current which flows into or out of the battery system, and the voltage across the common DC bus are also measured. These data are analysed by a microcontroller. Based on these data the state of charge (SOC) and state of health (SOH — ageing condition) are internally determined. An algorithm implemented in the microcontroller decides which battery should be connected to the DC bus of the PV
hybrid system. Long periods from one complete charging process of the battery to the next, which are typical for PV systems, are shortened using a DC/DC converter. This allows charge to be exchanged between batteries in a way that one battery can be used to fully charge another. Only small amounts of energy are transferred between the batteries in this "maintenance charging" process. During this process, the remaining batteries can store the energy supplied to them or provide power to the load. This parallel operation thus allows the energy to be used efficiently, while simultaneously increasing the lifetime and the reliability of the batteries. Furthermore, the BMS includes charging strategies for batteries that have suffered from inadequate charging, which "rejuvenate" them with maintenance charging processes that make their rated capacity accessible again. Appropriate operation management by the BMS ensures that large compensation currents do not flow in the circuits of the corresponding batteries.

The power switch which connects the batteries to the common DC bus is based on MOS — FET’s. Five transistors were connected in parallel to achieve the required current rating of 150 A per string. The batteries can be connected to or disconnected from the common DC bus by the microcontroller by an IC control board. Hardware for logical gates on the IC control board prevents a battery from being connected simultaneously to both the DC bus and the output of the DC/DC converter, and by this from short-circuiting the converter. The algorithm used for SOC balancing was developed at Fraunhofer ISE for use with microcontrollers and includes correction algorithms based on expert knowledge. In this way, the SOC is determined to an accuracy of 10% without needing a complete full charge for recalibration.

The battery system including the BMS has two external terminals, so that it can be connected to the PV hybrid system in the same way as a conventional battery. In addition, it outputs information on the SOC and SOH of the storage system.