Category Archives: SonSolar

ESES Master Theses

At the time of writing, the latest year’s theses are not yet presented, defended, or graded (this will happen in June and in September). The first four years’ theses (graded from A to E) are 27, and as seen from this list of titles, they cover many different areas of renewable energy:

1. A systematic analysis of a large grid-connected amorphous double-junction photovoltaic system in high latitude application.

2. A heat use concept for the EMA-collector in combination with a heat pump and a borehole store.

3. Evaluation of an EPS-MaReCo.

4. Analysis of three-pipe-system for combined heating and cooling distribution.

5. Energy conscious retrofit of single family houses: Comparison of Sweden and Hungary.

6. Market and literature study on technologies for seasonal storage of solar energy regarding small-scale applications, with focus on thermo chemical storage.

7. Comparison of batteries with different charge control method.

8. Development of a cost effective solar cooker.

9. Generation of electricity by using thermo-photovoltaic devices with photonic techniques and combination of selective edge filter.

10. Cost analysis on solar powered radio base station with cooling demands.

11. Optical and thermal performances of load adapted solar collectors: Optical modelling of two load adapted collectors.

12. Optical and thermal performance of load adapted solar collectors: Outdoor performance tests and evaluation.

13. Evaluation and simulation of a combined system based on heat pump, solar collectors.

14. Simulation of a solar absorption cooling system for hot climate.

15. Optimisation with industry of a solar heating system using simulations.

16. Experimenting with the sun. Experiments for the exhibition “Nedkalla Solkraften” at the Museum of Science and Technology in Stockholm

17. Tibetan Photovoltaic Village System

18. Investigation of Hogskolans 1.44/1.8 kW PV-system

19. Designing a Curriculum for a Course on Renewable Energy suitable for the Faculty of Engineering the University of Surabaya, Indonesia

20. Charging Station design for electric transportation

21. Solar Pellet Combisystems: a feasibility study in Toscana, Italy

22. Heat Resistance between PV Cells and Thermal Absorber in a Photovoltaic/Thermal Solar System

23. Use of Solar Energy in Low Cost Housing in De Aar, South Africa

24. Characterization of Monocrystalline Silicon Solar Cells using Different Methods

25. Evaluation of Properties and Performance of Low — cost Prototype Solar Collector

26. The Solar Lantern and battery Options Photovoltaic Technologies

27. Solar cooling

Our original intention was that all ESES students should do their thesis work within one of the current research projects at SERC. As it has turned out, at the most half of the students have done that. Some have had strong ideas about something else that they wanted to do (and managed to convince the ESES examiner that it would be an acceptable choice). Some have opted for a task that was offered by a SERC researcher but not part of a current project. Some have done their thesis work at another institution, even abroad, or at a company.

Acknowledgements

We would like to thank many colleagues at SERC who participate in ESES activities with administration, lecturing, lab instruction, study tour guiding, and thesis supervising — in all, making the ESES year possible: Per Berg, Anneli Carlqvist, Frank Fiedler, Jill Gertzen, Annette Henning, Tara Kandpal, Klaus Lorenz, Svante Nordlander, Bengt Perers, Tomas Persson, and Mats Ronnelid.

References

Broman, L. (2003); ESES, a European master’s Program in Solar Energy Engineering. Proc. ISES Solar Worls Congress, Goteborg, Swden, paper PE4 (4pp).

Broman, L., Blum, K., Garofoli, V., Kristoferson, L., Kusoffsky, U., and Hidemark, B. (1998). Creating a European Solar Engineering School. In Anil Misra, Ed., Renewable Energy Education — Current Scenario and Future Projections, pp 42-47. Tata Energy Research Institute, New Delhi.

Broman, L., Duffie, J. A., and Lindberg, E. (1991); A Concentrated Course in Solar ThermalProcessEngineering. Proc. ISES Solar World Congree, Denver, USA, pp 3815­3820.

Duffie, J. A. and Beckman, W. A. (1991). Solar Engineering of Thermal Processes. John Wiley & Sons, New York.

Garg, H. P. and Kandpal, T. C. (1999). LaboratoryManualon Solar ThermalExperiments. Narosa, New Delhi.

Kandpal, T. C. and Garg, H. P. (2003). Financial Evaluation ofRenewable Energy Technologies. Macmillan, New Delhi.

Markvart, T., Ed. (1996). SolarElectricity. John Wiley & Sons, New York.

EU White Paper on RES (1997). Energyforthe Future: Renewable Sources ofEnergy — White Paper for a Community Strategy and Action Plan <http://europa. eu. int/en/comm/dg17/599fi_en. htm

The Sun Emulator

Because the Sun Emulator uses seven rings to simulate the 21st day of all twelve months, the heliodon is a 3-D model of the sun paths. At an instant, one can tell that the sun comes only from a part of the sky often called the solar window. It is also easy to see which region of the sky the sun shines from during the overheated period, which region of the sky in the underheated, and equally important which region of the sky the sun never shines from. It is also easy to show how these regions of the sky move up and down with changes in latitude. It is most important to understand that any specific sun angles are not very meaningful and potentially misleading. For example, June 21 at 12 noon is not representative of the summer condition although frequently used in graphical approaches to solar design. Rather, it is very important to understand that the sun must be rejected whenever it comes from the summer region of the sky. The size of this region is a function of climate. Similarly, the sun angle of Dec. 21, 12 noon is not especially meaningful because we want to collect the sun when it is coming from the winter region of the sky.

By rotating the cradle holding the rings, it is easy to understand how to design a solar responsive building anywhere from the equator to the poles. It is instantly obvious, for example, that at the equator, north and south windows receive equal amounts of sun over a year. Thus the Sun Emulator is a powerful teaching tool even before its lights are turned on.

The Sun Emulator clearly shows not only the daily symmetry of the sun’s travels across the sky but also the annual symmetry where the sun path for Nov. 21 is the same as Jan. 21 and May 21 is the same as July 21, etc. It is for this reason that only 7 rings (sun paths) are needed to simulate the 12 months. This heliodon also shows how for six months of the year the sun shines into north windows at all latitudes even if it is only for brief times and at very glancing angles. Most people, including many "solar designers”, erroneously believe that the sun never shines into north windows or that it only occurs for a few days. For hot climates this fact is of great importance. It is also easy to understand how the length of day is a function of not only time of year but also latitude, except of course, for the two days each year called the equinoxes. All this can be understood within minutes by any person, of any age, and any educational level.

Unlike graphical, verbal, or mathematical explanations, learning from a "conceptually clear” heliodon is easy, quick, leaves a profound understanding, and will be retained far better because it does not depend on rote memory but on a god’s-eye — view experience of the relationships of a building with its constantly changing solar environment.

Renewable Energy Policy in Poland

Malgorzata Wolna, Polish Solar Energy Society ISES

Introduction

Black and brown coal have been used as main energy raw materials in Poland for centuries, and even today are the basic source of energy used for both industrial and domestic purposes. However fossil fuels create environmental problems such as air pollution by increasing carbon dioxide and other greenhouse gases concentration in the earth atmosphere causing, in consequence, climate changes due to global warming. Systems utilising renewable energy sources (RES) are often not economical. The prices of conventional energy carriers are lower than those of RES. Financial mechanisms addressed directly to the independent producers of energy from RES are insufficient. These and a number of other barriers hinder the development of RES sector.

However the environmental situation indicates that changes in the structure of energy supplies in Poland are urgently needed and new solutions and applications are being considered.

Goals of Poland’s renewable energy policy

The EU’s White Paper [1] presents the strategy and action plan in the field of RES, which requires all members states to take steps towards the solution of energy problems. The European Union’s target is to increase the share of RES from 6% to 12% of gross energy consumption by 2010. Another document — EU’s Renewable Electricity Directive 2001/77/EC [2] gives a framework for increasing the share of green electricity from 14% to 22% of gross electricity consumption by 2010. The forecasts also include ten European applicant countries that will in the nearest future become members of the European Union.

Poland has adopted a renewable energy strategy, whose goals, at present, are lower than the targets set by the European Union. The main objective is to increase the share of energy from renewable sources in primary energy balance to 7.5% in 2010 and to 14% in 2020 [3]. In the Accession Treaty [4] Poland set its national indicative target for the consumption electricity from RES in the total gross electricity consumption to amount to 7.5% by 2010.

Table 1. The share of green electricity generation in 10 candidate countries in 1999 and prospects in 2010 [5]

Candidate Country

The share of green electricity generation (%)

1999

2010

Czech Republic

3.8

8

Estonia

0.2

5.1

Cyprus

0.05

6

Latvia

42.4

49.3

Lithuania

3.3

7

Hungary

0.7

3.6

Malta

0

5

Poland

1.6

7.5

Slovenia

29.9

33.6

Slovak Republic

17.9

31

Table 1 presents the targets negotiated by ten associated candidate countries. It depicts the share of green electricity in the total gross electricity consumption predicted in 2010 and compares it with figures for 1999.

Ministry of Agriculture and Rural Development

To meet numerous challenges and solve problems in the RES sector, the Polish governmental policy is focused on several scopes of activity, including environmental, economic, financial, agricultural, educational and research policy (Fig. 1).

Educational and research policy

Ministry of Education

Ministry of Scientific Research and Information Technology

Fig. 1 RES policy in different sectors in Poland

Experiences gained with the realisation ofthe. Summer Academy for Mediterranean Solar Architecture (SAMSA 2002)

Patricia Ferro* — ISES ITALIA, criferro@tiscali. it
Cesare Silvi* — ISES ITALIA — csilvi@jndra. com
Maryke van Staden* — International Solar Energy Society (ISES) — mvanstaden@ises. org
*ISES ITALIA, Via Tommaso Grossi 6, 00184 Rome, Italy
* InternationalSolarEnergySociety(ISES), Wiesentalstr50, 79115Freiburg, Germany

Introduction

Recognising the need for practical training in the field of integrating solar technologies in building design, using solar architecture strategies, Renewable Energy Technologies (RETs) and energy efficiency (EE) concepts, the International Solar Energy Society (ISES) organised the first Summer Academy for Solar Architecture in Freiburg, Germany in 1997. This training event focused on sustainable building in temperate to cold climates (Northern and Central Europe). Subsequent events were organised in different parts of the world, providing training to professionals in the building industry, as well as to senior architecture and engineering students.

ISES together with ISES ITALIA (the Italian Section of ISES), adapted the Summer Academy concept for training in the Mediterranean region. They jointly realised the first Summer Academy for Mediterranean Solar Architecture (SAMSA) in Rome in the summer of 2002, togetherwith the University of Roma Tre.

This paper addresses the experiences gained with the realisation of the SAMSA 2002 in Italy, dealing with the Academy contents and organisational aspects. Regarding the contents, the paper will review the approach used in dealing with the general principles of solar architecture and the requirements of the Mediterranean cultures and climates (e. g. considering the ‘whole building’ approach, natural cooling and ventilation system, etc). On the organisational aspects it will provide an insight into the cooperation between experts and organisations, as a key factor for the success of the Academy (acquiring funding, selecting experts, regional marketing, etc).

In 2004 the range of Summer Academies continues, with three European events promoted by the ISES network. This will build on the SAMSA 2002 and other events, providing an inter-connected range of further education teaching events. It will assist the sharing of information and tools for implementing solar architecture and EE designs, using RETs. In this way the Academies support and expand the European network ofskilled solararchitecture professionals.

The views expressed in this paper are solely those of the authors and should not be ascribed to ISES ITALIA.

New Light on Rome 2000

Eight years later, promoted by ISES ITALIA, New Light on Rome by Peter Erskine was held in Rome in the year 2000.

The exhibition was part of the ISES Millennium Solar Forum, a series of scientific and cultural events promoted by ISES to mark, at the beginning of a new Millennium, the importance of solar energy, in particular:

• To illustrate that the sun has always been a source of energy, creativity and inspiration;

• To make use of the high potential inherent in artistic work for promoting solar energy applications;

• To bring new cultural dimensions to the field of solar energy which is primarily dominated by the approaches in use by scientists, technologists and business people;

• To benefit solar energy technology applications with the vision of artists;

• To promote contemporary art and design, inspired by the sun and the latest scientific discoveries and technological developments in solar energy.

As in Secrets of the Sun, also in "New Light on Rome 2000," the medium used by Erskine was not paint, but the solar spectrum, which in this case, however, was not produced by active systems, such as those used for Secrets of the Sun, but by passive systems, that included laser-cut prisms to receive and to catch the sunlight at various openings of the monument (Ilsolea360gradi 2000).

In addition to the Trajan’s Market, New Light on Rome 2000 was exhibited at another four ancient monuments and historic buildings: Museo delle Mura di Porta San Sebastiano, Cappella Palatina della Casa dei Cavalieri di Rodi, Criptoportico Neroniano del Foro Romano e Palatino.

Fig. 2 — A view of Peter Erskine’s solar art exhibition "New Light on Rome,"at Trajan’s Markets in Rome, June2000

SOS — Secrets of the Sun and New Light on Rome 2000 enhanced even more the already spectacular ancient

architecture, by

transforming monuments, churches and historic buildings into magical rainbow chambers. Flat prisms, such as those installed by Erskine at the Trajan’s Markets,

perception of ancient monuments by projecting on them the

captured the Sun’s light at openings just as windowpanes of 2000 years ago might have. In addition they were conveying to people the message that active or passive solar systems can change profoundly the artistic solar spectrum, however without any harm. In the same way solar technologies can change the natural and built environments where we live and work with benefit to them, to our health, and to the quality of life. Rome’s car emissions, on the contrary, are not visible but they cause more damage to the monuments than the solar radiation.

Experiences with Future Energy Issues as Project. Topics for Upper Grade Students-A Case Study

Birgit Brinkmann

Gymnasium Birkenfeld, Germany

Address for Contact:

Prof. Dr. Klaus Brinkmann
Umwelt-Campus Birkenfeld
Automation and Energy System Technology
P. O. Box 1380, D-55761 Birkenfeld/Germany
E-Mail: birgit. brinkmann@math-edu. de

In several federal states of Germany 11th or 12th grade students in public schools have the possibility to do a little research work. This is generally named “Facharbeit” and has to be documented in a paper. We as students may choose any topic we like for such a work. Subjects of particular interest for us as students are themes concerning our future life, the social and economical environment in which we will live. Here the problem of future energy is one of the most important ones.

In this paper I want to present my own experiences, which I made during my work. I want to present the occurring organizational difficulties, my successes and frustrations, the new insights I won. A comparison of my personal experiences with the experiences made by my student colleagues shows general common disadvantages, which lead to a list of wishes.

Perspectives

Looking forward to the future, the Centre for Sustainable Development has formulated a strategy for its own sustainable development. This strategy is based on inner collaboration and external networking with other institutions, members of the national and European academic community but also with representatives of the economic and social environment.

The support for developing spin off companies is another point of our future and represents an experience so far not fully exploited in Romania.

The presence of the members of the Centre in the scientific life, participators in research

and education projects — was the path for developing successful collaborations and we

intend to enlarge our partner consortium based on the existent (and developing) resources

and on the mutual interest.

References

1. Brundtland, G. H., UN Report, Our Common Future, 1987

2. Kaplanis, S, Visa, I., Duta, A., Renewable Energy Systems & Environment, Ed. Univ. Transilvania, 2003

3. Peake, S., The Jo’burg Summit, ReFocus, 11/12, 2002, p. 46-50

4. Sorensen, B., Meibom, P., A global renewable energy scenario, Int. J., Global Energy Issues, 13, No. 1-5, 1998

5. * * * The Romanian Strategy for Sustainable Development, Ed Nova, Bucuresti, 1999

6. Duta, A., Visa, I., Training the students for promoting renewable energy systems, in Proceedings of the 2nd Balkan Region Conference on Engineering Education, Ed. Univ. Lucian Blaga, Sibiu, 2003, p. 109 — 112

7. Visa, I., Duta, A., Exchange of Competencies on Renewable Energy Sources and Environment Management, in Proceedings of the 2nd Balkan Region Conference on Engineering Education, Ed. Univ. Lucian Blaga, Sibiu, 2003, p. 73 — 76

8. Visa, I., Duta, A., Kaplanis, S., Renewable energy sources and environmental management users-friendly ICT tools, in Proceedings of the International Conference on Solar Energy Systems, Goteborg, Sweden, 2003 (on CD)

9. Visa, I., Duta, A., Bejan, V., Renewable Energy Systems and Environment Management Development in the Transilvania University, Education for Sustainable Development, Ed. Univ. Transilvania, Brasov, 2003

Fuel consumption ratio, avoided carbon and reference standards

The cost of one ton of the fuel carbon (dioxide) avoidance by the specific technology is an important yardstick for renewable energy technology evaluation. However, there is a fundamental dilemma here: How to compute the avoided carbon amount per one kWhe that need not be generated from fossil sources. Is it by assuming, say, a 40% efficiency conversion of the fuel (heat of combustion) to electricity? Why not 30%, perhaps 55%? Any assumption will lead to a different result for the avoided carbon amount. The problem requires an agreed reference efficiency to serve as standard. In case more than one standard becomes necessary, this should be temporary and well reasoned. Full transparency of applied standard(s) (recognized or implied) is essential, with no exception.

Analysis is in place before we can answer the question. Figure 1, drawn after the diagram pattern of Geyer [2] illustrates the Fuel Consumption Ratios (FCR) for model thermal power

The relative fuel consumption (hence emissions) ratio and the green energy fraction of systems over full load hours. a 30% fuel in SEGS solar hours. a 50% fuel in SEGS solar hours.

systems of various conversion efficiencies, by the thin solid lines with varying slopes. In the figure the 60% conversion Combined Cycle (CC) is taken as a baseline standard for reference, thus having an FCR of 1 (as shown by the vertical scale on the right) when the power plant has operated for the full 8760 hours of the year (full yearly load). The 60% CC baseline seems to serve as the recommended standard reference for large power plants at sites where natural gas may be available. The CC is at present a practical, efficient power plant of available technology. Line slopes of various efficiencies are shown on the chart. For example, the 30% conversion line, which shows an FCR of 2 (the inverse efficiency-ratio with respect to the 60% standard) for the full year operation. It reflects the relative excess fuel consumption (hence emissions) of the 30% system as compared to the 60% (baseline standard). As the amount of fuel (in terms of the heat of combustion) is 1.667 kWht (per 1 kWhe electricity) for the 60% conversion, it will double to a value of 3.333 kWht for the 30% conversion. The avoided carbon in weight (ton/MWh) for each case is derived through the FCR value and the particular fuel stoichiometry (chemical compsition-based accounting). It is of significance to recognize that the avoided carbon amount per one kWhe (green electricity) output is not explicit without a clear decision on the baseline or reference standard [3]. By setting the reference standard, we can resolve the above-mentioned problem of how to compute the avoided carbon amount per one kWhe electrical energy output. Thus, environmental parameters of hybrid systems are governed by set standards.

Solar Energy Education Project for Schools

Dorota Chwieduk, R. E. Critoph2, Tony Book

1Institute of Fundamental Technological Research, Polish Academy of Sciences, ul. Swietokrzyska 21, 00049 Warsaw, dchwied@ippt. gov. pl

2 School of Engineering, University of Warwick, CV4 7AL Coventry, UK. R. E.Critoph@warwick. ac. uk

3 Riomay Ltd, 1 Birch Road, Eastbourne, BN23 6PL, UK, tonybook@pavilion. co. uk

Educational goals in scientific subjects can best be achieved if theory is backed up by demonstrations of practical applications. To achieve the aim of educating young people in solar energy, a Polish — British project “Solar Energy Educational Demonstration System for Schools — Mini Solar Laboratory" has been undertaken. The UK’s Department for Environment Food and Rural Affairs (DEFRA) has supported the project. The main aims of the project are to increase the awareness of renewables in young people through the process of theoretical study and experimental work on solar energy, and to implement environmental protection through renewable energy applications.

The background of the project

A Polish — British project — Solar Energy Educational Demonstration System "Mini Solar Laboratory" for Schools has been undertaken by Polish and British partners representing science, education and business. The prime purpose was to present to young people the principles of renewables and their role in a modern industrial world. In Britain there are many different demonstration and educational projects for young people focused on energy conservation and applications of renewable energy. However, there are not so many such projects in Poland.

In Poland to promote utilisation of solar energy at schools a few active solar systems, equipped with flat plate solar collectors or PV modules have been installed. Most of these systems have been installed thanks to international co-operation and international funds. Some general information about two projects is given below.

The realisation of the first project was made possible due to the Polish — Danish bilateral co-operation and Danish financial support. A solar heating system with 80 m2 of solar collector and a 3 m3 storage tank has been installed in the primary school (nr 173) in the city centre of Lodz [1]. The solar system supplies hot water to the hot water system at the school, the heat surplus being used to warm up the water for the school swimming pool. The other solar school project was realised in Wawer near Warsaw [2]. This is a roof — mounted 1 kWp PV grid connected system (one of the first of its kind in Poland). The system consists of 20 BP Solar double-junction thin-film amorphous silicon PV modules (MST-50 MV) in universal frames. The area of the array is 16 m2The system was built as a result of Polish — American co-operation thanks to US Ecolinks Program. Both these projects are typical demonstration projects and promote the idea of solar energy through the demonstration of the modern solar energy technologies.

The main aim of our project was not only to demonstrate solar technology but also to educate young people in solar energy through a theory and practice. For a good practical education it is important not only to learn about solar energy and other renewables but also to be able to interact with a real solar system, i. e. to alter its operation and control parameters, and to learn from the effect on the system performance and solar energy fraction. The objective of the project was to build a school display, in the form of a "mini solar laboratory" that can demonstrate and teach Solar Energy at the same time. It was decided that the laboratory should consist of two parts: an open — air laboratory on the roof of the school and indoor laboratory inside the school building. The indoor laboratory is
connected by a monitoring and visualisation system with the outside part. This allows pupils to change the system control parameters by the use of computer software.

The realisation of the project was possible thanks to The UK’s Department for Environment Food and Rural Affairs (DEFRA) which has supported the purchase of a "Mini Solar Laboratory" via its Environmental Assistance Fund.

Directions for Use

Printed directions for the use of the Sun Emulator are extremely brief and almost unnecessary because this heliodon is a model of our everyday reality. First, the model to be tested is placed at the center of the round table, its south orientation aligned with that of the heliodon. Then the cradle holding the seven rings is adjusted for the correct latitude by means of a single locking knob. Next, a twelve position rotary switch is used to choose the sunbath for the 21st day of any desired month. To simulate the daily motion, the appropriate ring is rotated by hand from sunrise to sunset. Other rings are then rotated to investigate solar access and shading patterns at other times of year. To

see what happens through the year at a particular time of day, the lights of all the rings are aligned and the rotating switch is turned to simulate the annual travel of the sun up and down the sky.

2. Applications

Although the Sun Emulator was developed primarily for architecture students, it is appropriate for a much wider audience, as will be discussed below. For architecture, landscape architecture, planning, and interior design students a heliodon has three separate applications: (1) the initial learning of concepts and principles, (2) the design process, and (3) presentation. As was described above, the Sun Emulator is an unsurpassed teaching tool. As a design tool, it can be used to actually assemble a design as, for example, when the length of an overhang is determined on the model by a trial and error method. Or the heliodon can be used as an analysis tool where a design, developed away from the device, is tested for its performance. In my own classes, I have students test models of designs they developed previously in studio. After the analysis establishes what works and what doesn’t, the students redesign their projects to be more solar responsive. Next, fast and dirty study (not presentation) models are built of an important window and shading system and these are then tested on the heliodon to determine what weaknesses remain for further redesign. A popular application among the students is for presentation purposes. They use the heliodon to photograph their models to document their designs’ solar responsiveness for juries and portfolios.

Homebuilders are another major user group. Most homebuilders are in fact designers. They often decide which building design will be used, what its orientation will be, where it will be located on a lot, what trees will be left standing or where trees will be planted, etc. Each of these decisions would benefit greatly from the understanding of solar responsive design principles. Developers are even more in need of this knowledge because street orientation has major consequences, since it will usually determine orientation of the buildings which are almost always aligned with the street rather than the sun. One of the most successful developments in the second half of the twentieth century, Village Homes in Davis, California, was designed by means of physical models tested for solar responsiveness.

Government officials also need to understand the benefits and practicality of solar responsive planning and design. Laws, planning regulations, and building codes generally do not encourage solar design because their writers were not convince of the benefits and the feasibility of solar designs. I have direct experience with a government official who after seeing the heliodon demonstration developed an interest in the potential of solar responsive regulations.

If homeowners and architectural clients are not interested in solar responsive design, then there is little incentive for building professionals to provide such designs. Thus, it is imperative that all who finance or control the design of buildings should be knowledgeable about the potential benefits of working with the sun, and ironically, many of these benefits come from strategies that cost little or are free.

In effect almost everyone should understand and thus believe the financial and environmental benefits of solar responsive design. This widely held understanding, I believe, is best accomplished by means of a "conceptually clear” heliodon. If the hands-

on science museums for children had heliodons, children would understand early on and in a lasting manner the logic of designing with the sun. Schools too could use heliodons in their earth science or physics courses. If children routinely learned about these principles, we would have future generations that would demand the benefits of solar responsive design because they would know that they are real, achievable, and economically wise.

3. Limitations

The Sun Emulator is an excellent heliodon for teaching and designing where high precision is not vital, which is the case for most building design. For example, the precise knowledge of the shading from a tree is meaningless since trees grow. Also weather is too variable to establish precise dates when sun or shade must be available.

Although the sun angles for the point at the center of the heliodon table are very precise, as one moves away from that point, in all three axes, error accumulates. Thus, small models are best and some larger models can be moved around so that the part of the model being analyzed is placed over the center of the table.

The highest precision in model testing is possible with sundials mounted on models tested outdoors, the only place where parallel light rays are readily available. Although such model testing is extremely precise, it is inconvenient, awkward, and conceptually unclear. It is awkward because you can’t test models outdoors at night, in the rain, or on cloudy days, and it is frustrating and uncomfortable under partially cloudy, windy, hot and cold conditions. Testing models outdoors requires the model to be tilted to account for all three variables of sun angles: latitude, time of year, and time of day. As described earlier these problems are both practical and conceptual in nature. Non-horizontal models must be well glued and prevented from sliding. They are also not easily analyzed since we find it hard to relate to buildings that are not horizontal. Consequently, I recommend outdoor analysis with sundials only after a design is ready for presentation purposes, or for fine tuning when high precision is required.

Although a larger heliodon could handle larger models, the Sun Emulator was sized so that it can still pass through a standard door, be completely fabricated at the factory, shipped fully assembled, and take up very little space when stored (less than 2 square meters) (Fig. 3). After unpacking or storage, it is only necessary to plug the heliodon into an electrical outlet and to rotate the model table from vertical to horizontal.

FIG. 3

The Sun Emulator in its storage mode. The cradle with the 7 rings is set for 0 ° latitude, as it would be to simulate solar geometry at the equator.

Although some other heliodons are more precise for larger models than the Sun Emulator, its "conceptual clarity” ease of use, and other advantages described above, more than compensate for its limited precision.