� Tel.: +44-114-255-1570.E-mail address: johnpage@un

0360-5442/$ - see front matter #doi:10.1016/j.energy.2004.04.037

ivshef.freeserve.co.uk (J. Page).

2004 Elsevier Ltd. All rights reserved.

Energy 30 (2005) 1501–1515

www.elsevier.com/locate/energy

First conference on measurement and modeling of solarradiation and daylight ‘‘Challenges for the 21st Century’’

Napier University, Edinburgh, 15–16 September 2003

John Page �

Emeritus Professor of Building Science, University of SheffieldSheffield S11 9BG, UK.

Abstract

This was the opening paper to the Conference. The paper combines the historic experience of theauthor on solar radiation climatology built up over the last 50 years with a more detailed account of hiscontribution to a number of recent European funded projects dealing with solar radiation in the contextof applications. These projects have been especially concerned with the improved delivery of accuratelyestimated and reliable solar radiation data to users. The recent European projects have made extensiveuse of satellite data in conjunction with reliable ground truth sites. The paper explains the special empha-sis now being placed on the effective use of IT to provide user selected data delivery on the world wideweb. The paper finishes with a suggested road map for the future for solar radiation and daylightmeasurement and applications research. The importance of achieving an improved understanding of dif-fuse radiation through improved measurement approaches is especially stressed. The need for animproved understanding of spectral radiation is also underlined.# 2004 Elsevier Ltd. All rights reserved.

1. Introduction

Envisioning the future of an environmentally threatened world throws out many challenges toour existing mind-sets. We are currently facing serious risks concerning the nature of our futureglobal climate. Wise use of energy is central to the future of our planet and to the future of ourhuman life styles. The perceived climate change risks are critically based on excessive use of fos-sil fuels. We urgently need to move towards a more sustainable global society. The sun is by far

J. Page / Energy 30 (2005) 1501–15151502

and away our most important energy resource. We have now to learn rapidly how to use thisresource more wisely than we do at present, in order to address the climate change challengeseffectively. However, the process involves much more than meeting the thermal challengesimposed by climate change in isolation.

The energy of the sun may be harnessed in a multitude of ways, for example, to increase pho-tosynthetic yields, to enable improved visual perception, to achieve improved bio-thermal envi-ronments and to generate electricity using voltaic devices, among many other things.

2. The biological significance of solar radiation

There is always a biological aspect in using solar energy in our living environment. We there-fore need to think beyond the thermal environment considered in isolation. For example, day-lighting is important for human health as well as for perception. It drives our human biologicaltime clocks. In fact, daylight drives the chemical time clocks of all biological systems. Light trig-gers the daily and seasonal time responses of all plants. Light enables visual perception and sofosters bio-communication between all zoological species in the world. Daylight links us ashuman beings with our wider natural environment.

So the radiation applications solution space, for which we are involved in systematic dataprovision, has to involve the inter-relation of the sensible use of thermal energy of the sun withthe simultaneous design of biologically acceptable environments.

3. The importance of the spectral element

There is an important spectral element implicit in many of the analyses needed. For example,building design has to integrate daylighting design, a spectrally selected component of solarradiation, and thermal environmental design in biologically sensible ways. The assessment ofUV exposure risks, another spectral element, has to be embraced in the biological analysis. Theissues to be addressed are more complex than most people realize. It is important to recognizethe living world interacts with photons photochemically to drive essential life processes.

4. The challenges ahead

We need accurate measured radiation data first to achieve basic scientific understanding ofthe workings of our atmosphere. Most of life is located in that atmosphere. Marine life islocated in the oceans. Light penetrates those oceans. The atmosphere above chemically interactswith them. We need effective human policies to live in our atmosphere successfully, because wehave developed the human capacity to damage it in very serious ways. Responding effectively tosuch challenges implies creating powerful design tools to inform and support policies for usingthe sun effectively over a wide range of applications. It also demands effective tools to assist usreject the excessive solar radiation gains, which can make us in our buildings too hot and causeother environmental damage. Tools for considering the UV environment are also needed.

So, I ask you to start to identify yourselves in this meeting as tool builders for the future. Iview you as early ‘‘solar age’’ people. It is time to ask you to sharpen your ‘‘solar flints’’ foraction.

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5. Fostering the future in the context of the importance of tasks

Nearing 79, my life’s work must be nearly complete. I feel now it is especially important forme to do as much as possible to foster the emergence of new cadres of young scientific workersof appropriate vision. Your skills are needed to blaze the future trails in this central field ofhuman endeavour. We require an expanded and knowledgeable solar radiation workforce. Oneof my own especial pleasures in working with European teams over recent years has been thepersonal working contact it has given me with two generations of younger people. They havetaught me a lot. I have enjoyed their enthusiasm.

So I thank Professor Tariq Muneer, both for his vision in setting up this meeting and forinviting me personally to chair it jointly with my old friend, Professor John Monteith, FRS. Wehave both been involved with solar radiation research for a very long time. The fact that one ofus was in building research and the other in agricultural research enriched our perception ofcritical issues. I see solar energy science as essentially a multidisciplinary activity.

John and I both still believe in the importance of the scientific tasks that lie ahead. Like longdistance relay runners, we are now passing the batten of progress on to you. There are manylaps yet to run. So it is wonderful to see young people in our group here today fresh and readyto discuss the important topics on our agenda. We have also a number of very experiencedspeakers. We welcome them too. John and I have already read your abstracts with great interestand now look forward to hearing your fuller expositions and listening to the consequentdebates, which I am certain will be lively.

6. Building bridges between radiation observations and radiation applications

I also welcome you here today as a person who has devoted considerable attention overnearly 50 years to building solar radiation information bridges. These bridges have providedpaths by which solar radiation data have been linked to practical solar energy applications. Thepaths conjoin ideas from those, who measure solar radiation in the field or from space, i.e. thepeople who provide us with the basic observational data banks, with those who need solar radi-ation data for use in a wide range of practical applications. It is good that both the issues ofthermal applications and of daylighting applications are considered.

7. The measurement pioneers and the new approaches based on satellites

The people who provided the solar data in the past used to have their instruments firmly onthe ground. The pioneers also had their scientific feet firmly on the surface of the earth. Todaywe receive much solar radiation data from sensing instruments located far above our atmos-phere. Satellite technology now contributes a significant proportion of the basic solar radiationinformation available to us globally, but it requires considerable effort to make that informationefficiently available for practical applications. Much of our recent European Union (EU) fundedteam effort on solar radiation data has been devoted to turning this theoretical opportunity intoan accessible real facility open to any user who wants it. You can see some of what we haveachieved by going to the Solar Database Intelligent System web site [1]. This site is the product

J. Page / Energy 30 (2005) 1501–15151504

of our recent European collaborative work on solar energy. Like the pioneers before us, we tooneed to keep our science on solid ground.

The availability of data from sophisticated well-calibrated ground sites of high scientific qual-ity becomes even more important as satellite technologies develop. Validated clear sky horizon-tal surface models and overcast sky models provide essential algorithmic components in theprocess of converting the extraterrestrial radiance observations into ground values of irradiance.Our detailed EU-linked work on satellite derived data associated with SoDa-IS has been basedon Heliosat 2. The work was led by the Groupe Teledetection & Modelisation of l’Ecole desMines de Paris. The Heliosat 2 method we used is described by Rigollier et al [2]. The methodused had to take account of the cloud index at any time. The cloud index results from a com-parison of what is observed in a set of pixels around the target pixel with what would beobserved if the sky were clear. The Rigollier et al. model [3] was used to model the clear-skyvalues. The Linke turbidity factors used reside in the database of SoDa-IS. A description of thisdatabase may be found in Remund et al. [4]. Ground observations importantly provide the onlyreliable way (‘‘ground truth’’) for checking the resultant efficacy of the algorithmic structuresbeing used to reduce the extraterrestrial radiance observations to ground level radiation values.Reduction processes enabling the estimation of ground solar radiation from space, based onadvances in atmospheric sciences, always need checking against reliable ground observations.

8. The importance of narrow band spectral information

There is the growing realisation too of the increasing importance of narrow-band spectralinformation, as essential for the better understanding of solar-radiation-driven photochemistry.I must remind you that photochemistry dominates the interaction between the radiativeenvironment and the living cell. Such photochemical reactions are very sensitive to wavelength.Photovoltaic solar cell performance is also strongly linked to wavelength. We cannot rest on ourlaurels, saying knowledge of photosynthetically active radiation (PAR) is enough for all botanicstudies and CIE-defined light illuminance is enough for all human visual studies. For example,for a view of the wider impacts of light on humans, refer Brainard and Glickman [5]. We needimproved spectral tools in addition to better broad-band tools. So I anticipate extensive expan-sion of interest in the spectral area, both in field measurement on the ground and in the associa-ted algorithmic studies. SoDa-IS, for example, provides a method for estimating thecomponents of UV-A, UV-B and UV-Erythemal for any place in the world. Using Gueymard’s[6] SMARTS spectral programme, we built a bridge between the broadband data sets and thenarrow-band UV data sets and incorporated the methodology into the IT structures we haddeveloped to deliver the results to users, refer Page [7]. This enabled us to deliver our pre-dictions by E-mail for any user-requested location across the world, refer [1].

9. Responding to the challenges

You will all certainly need to develop and refine your practical vision to achieve the effectivebridge building needed between solar radiation measurement and solar radiation applications. Ideliberately use the word practical as we are talking about applications of radiation scienceknowledge to a wide range of human activities involving policy making and design decision

1505J. Page / Energy 30 (2005) 1501–1515

making. We are not, in this meeting, just discussing solar radiation measurement in isolation.

We look to its value for many practical applications. It is an issue of using the science as well as

doing the science.The sun drives the energetics of the whole earth, but many of its impacts are still poorly

understood even by experts. Solar radiation is also the driving force for natural ecosystems. A

sound understanding of energy flows is critical for the Science of Ecology.One of the most interesting features of the solar flux is its very high variability from instant to

instant and from day to day. Constable, the famous English landscape painter summed up the

challenges we face in measurement when he wrote ‘‘ The world is wide; no two days are alike or

even two hours, neither were there ever two leaves of a tree alike; since the creation of the world’’.

The application challenge is to decide how much complexity can be addressed in design and

what statistical simplifications are acceptable. Constable knew the dynamics were complicated

but gave us considered visual images. In essence, we too have to present a set of data pictures

based on sound statistical principles. The clarity of the presentation of these data to the user is

important. It determines whether the ideas will be taken up or not.

10. The scene 50 years ago. The emergent interest in solar radiation in Building Research

When I started work at the Building Research Station in 1953, some 50 years ago, I was put

to work on the improvement of the design of buildings for tropical climates. There were two

scientific cultures present at BRE at that time, each group working in relative isolation from the

other. I do not think they really understood that the two cultures had to be inter-linked to find

satisfactory human solutions within buildings. One scientific culture was concerned with the pre-

diction of the thermal climate of buildings. Their solar radiation studies were directed towards

the issue of controlling the over-heating of buildings, adopting the concept of the design day,

then defined by AHSRAE as August 1st. This group was very solar beam oriented, considering

the diffuse radiance both small and isotropic in nature. They did not make radiation measure-

ments. The other culture, led by R.G. Hopkinson, was preoccupied with the design of the day-

lighting of buildings. One can form a good impression of the global daylighting culture of that

time from Hopkinson’s classical book [8] Their daylight data studies were then very much

directed towards the standardisation of the properties of a reference overcast sky to be used for

high latitude daylighting design. The daylighting group saw the proper definition of the lumi-

nance distribution of the overcast sky as the key challenge. Hopkinson’s group made field meas-

urements of radiative quantities. There was also a strong interest on human lighting needs,

established by physcho-physical experimentation. Broadening the BRE daylighting studies

towards the Tropics created a need to define a clear sky luminance model that reflected the

actual distribution of light across the cloudless sky. Kittler [9] played an important role in this

vital development. A historic review of the daylighting design pioneers may be found in the Pro-

ceedings of CIE Conference held in London two years ago including a contribution by myself,

refer Page [10].

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11. The importance of diffuse radiation measurements

I immediately saw that if you did not understand the impacts of solar radiation on the verti-cal surfaces of buildings, you were unlikely to be able to provide sound advice for buildingdesigners. I also found out very quickly that I could make no progress unless I could split thebeam from the sky diffuse irradiation and then add on the ground reflected radiation. Applica-tions usually require knowledge of radiation on inclined surfaces. An infinite number of slopesand orientations are available. Therefore, applicable practical solutions have to be sought algo-rithmically. Observations on non-standard oriented surfaces are valuable for developing andvalidating algorithmic models. Such observations are rare. The algorithmic tools, to be appli-cable, have to confer freedom of orientation and tilt in their application. It is difficult enough tofind funds to make measurements for the horizontal surface.

12. Algorithms as bridging mechanisms between observation and application

The underlying algorithmic structure in solar energy modelling forms the arch which supportsthe bridge above, which must connect horizontal surface solar radiation observations and theirapplication to provide practical solutions to real world problems. The algorithmic arch belowthus supports the user path above. We must attempt to provide a level path for user runningfrom basic information sources into practical design. As in all bridges, the underlying individualstones in arch have to be both strong in themselves and also key in well with their neighbours toprovide strength through mutual support at their mating faces. The whole arch has to bechecked for safe performance and not just the individual stones. This points to the essentialneed for effective teamwork to build confidently algorithmic safe crossings. I have hadvery positive experiences in team working in European projects funded by the EuropeanCommission. We have achieved so much more by working in team than we would have everdone working in our separate organisations. What I would see as one goal of this meeting is toencourage more team building around the many difficult challenges we face. I am sure this isgoing to be one result of the Conference.

13. The mid-50s radiation measurement research community

I knew within weeks of starting at the Building Research Establishment that I had to initiateinteraction with the correct people in the scientific community concerned with detailed solarradiation measurement. It was fortunate that R.G.Hopkinson’s team were on the site, becausethey had the contacts to the key measurers.

At that time there were not so many people involved, so a half a dozen letters enabled thecore group to be contacted. Some worked in independent Observatories and some worked inNational Meteorological Services. In the United Kingdom (UK) there was the UK Meteoro-logical Office site at Kew Observatory housed in a historic building, which presented many diffi-culties for practical measurements. Other important European Centres were located in Sweden,in Uccle (Belgium), in Vienna (Austria), and in Davos (Switzerland). Mountains figured large inthe work of the latter two observatories because of the historic importance of mountain-based

1507J. Page / Energy 30 (2005) 1501–1515

ultraviolet heliotherapy at the time when tuberculosis was common. In Europe we used theGngstrom pyrheliometric scale.

Wider afield, Nathan Robinson whom I got to know well, was a key worker in Israel. Russiahad work of high quality but the political barriers to effective scientific collaboration were thenhigh. Eventually, I met up personally face to face with Professor Kondratiev at a meeting of theWorld Radiation Commission at Oxford in the late ‘50s. This meeting showed me howadvanced the USSR was in the field of solar radiation climatology at that time. We were alsoisolated from the East German work at Potsdam.

In the USA the Smithsonian Institution was the key centre. Elderly Abbott was by far andaway the most important figure. He had several younger co-workers who were helping him.Universities like Harvard and MIT were active too. They all worked to the Smithsonian pyrhe-liometric scale.

14. The expansion into studies for tropical areas

It was still a world of Empires and Colonies. In the early fifties, a few skilled scientists experi-enced in practical measurement began to be posted to pioneering positions in Africa. When Istarted, Schuepp was very active in the African Belgium colonies, where he pioneered the under-standing of radiation climatology in humid tropical climates. Drummond had recently movedfrom Kew to South Africa, where he studied the two-season radiative climate of SouthernAfrica. He identified the impacts of dust pollution on dry-season radiation, which contrastedwith the high atmospheric clarity of the wet seasons in Southern Africa. Drummond also con-tributed significantly to the more accurate measurement of solar radiation using shading rings.They carried down the Gngstrom scale from Europe.

It was many years before we progressed to the common world radiation standard known asWorld Radiometric Reference (WRR). The impact of earlier pyrheliometric scales on differenttime segments of long-term solar radiation records is often overlooked by contemporary work-ers analysing long-term radiation data trends.

15. Using sunshine and cloud data. Gngstrom formula approaches

The pioneers were hands-on enthusiasts, with great personal knowledge of their instruments.Many of their measurements were spot measurements. The continuous recording of outputs wasdifficult. Using a galvanometer with a mechanical chopper bar, one could build a dot-basedgraphical record. This dot record then had to be evaluated visually to estimate the hourlyirradiation. There were no data loggers. It was thus very expensive to run a continuouslyrecording radiation station. There were consequently very few continuous observing solar radi-ation stations across the globe. This gave great importance to methods for estimating solar radi-ation from conventional ground meteorological observations of cloud amounts or of sunshineamounts. However, one could only derive the required regression equations from those siteswhere there were actual radiation observations. Extrapolation was often adopted, using the fewregression constants available without taking proper knowledge of seasonal changes in atmos-pheric clarity at different sites. Consequently, inappropriate regression constants were oftenapplied to estimate radiation. The sum of the monthly Gngstrom regression coefficients ðam þ bmÞ

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depends strongly on local atmospheric clarity. These important issues are discussed in detail inthe 3rd European Solar Radiation Atlas [11] and in the 4th European Solar Radiation Atlas[12] Sunshine data were used to generate infill global radiation data in the preparation of theseAtlases but the clarity of the site was always assessed first in the selection of the regression con-stants.

16. Impacts of advances in data logging and instrument improvement

It is easy to make an instrument which, when irradiated, will produce an electrical signal, sothe arrival of data logging made it much simpler to produce a record from an electrical signal.However, the solar radiation observers then tended to be changed from being specialised scien-tists with personal knowledge of their instruments to becoming routine data collectors. Themajority of the observers unfortunately failed to realize that it was in fact quite difficult to ach-ieve a sound radiation record. Their bosses, thinking the task was simple, usually gave them toofew resources and, also, too little training to do the job properly. Nevertheless, one or twoinstrument manufacturers gave considerable attention to improving their instrumentation. Forexample, Andy Drummond and Anders Gngstrom were recruited by Eppley Instruments to helpimprove their instruments. This did not necessarily mean the improved instruments fell into thehands of people trained or motivated to use them with appropriate skill. It also did not meanthe instruments were in fact properly re-calibrated at appropriate intervals. Fairly frequently,they were not. The US attempted a complex data rehabilitation exercise (refer Randall andLeonard [13]), but rehabilitated data can never be as good as properly measured data. Qualitycontrol of radiation observations is certainly an important issue, which has become even morecritical now that climate-change scientists have started to demand very accurate data to testtheir models and detect radiative forcing at the 1 W/m2 level.

17. The inauguration of the WMO World Radiation Data Centre

The systematic international collection of data records within the WMO World RadiationData Centre, located at the main Geophysical Observatory of a city that was then called Lenin-grad and now St. Petersburg, progressed and eventually became operational as an online data-bank [14]. There were gradually data from more sites. However, the lack of quality controlmeant that some of the data supplied by national meteorological offices to the WMO centrewere unreliable. The 4th European Solar Radiation Atlas drew on the St. Petersburg Centre forsolar energy data for 1981–1990. However, every dataset we used had first to be carefullychecked for quality by the German Meteorological Service. As a result, many data had to berejected.

18. The current lack of diffuse radiation data of appropriate quality

There are even fewer ground sites observing diffuse radiation. Sometimes shading disks areused, sometimes shadow bands. The published records obtained with shadow band pyran-ometers are sometimes corrected for shadow-band obstruction and sometimes not. Different dif-fuse correction procedures are used by different meteorological services. Some of these

1509J. Page / Energy 30 (2005) 1501–1515

correction procedures are not explained explicitly. Sometimes there are failures in the actual

mechanics of the shading procedures, so there may be undetected patches of direct beam inter-

ference in the supplied records. Consequently, we have faced great difficulties in gaining access

to reliable diffuse radiation records in the development of the European Solar Radiation

Atlases. As there are so few observed diffuse records, diffuse radiation at most sites has had to

be estimated algorithmically from the global radiation record using a small set of sites which we

considered had acceptable data to develop the algorithms. The detailed ESRA processes are

reported in ESRA [12].

19. The significance of instrumental improvements for the better understanding of diffuse radiation

I would like to conclude my comments on diffuse radiation by stating that the improvement

of the modeling of diffuse irradiance on horizontal surfaces is a critical activity for future solar

radiation applications. Diffuse radiation deserves more serious study, using modern advanced

pyranometers operating with shading disks. The paper by Myers to this Conference points out

that pyranometers with all-black receivers are rarely in thermal equilibrium outdoors creating

important errors in practical use. He mentions differences of about 20 W/m2 (or about 20%) in

clear-sky diffuse horizontal radiation around noon between current all-black sensors and older

black and white sensors. This topic has drawn considerable attention lately due to the impor-

tance of accurate solar radiation measurements in climatology and climate change applications.

As a result, black and white sensors are now replacing all-black sensors to measure diffuse radi-

ation and avoid thermal imbalance effects in research-grade measurement sites, like those from

WMO’s Baseline Solar Radiation Network [15] Moreover, this improved measurement of dif-

fuse radiation is performed with a tracking shade disc to block the sun without the need for

empirical shadow-band corrections. Diffuse irradiance is then summed with the horizontally

resolved direct irradiance to obtain global irradiance data. In recent literature, this adding tech-

nique has been shown to produce significantly better global irradiance results than the conven-

tional method, using a single unshaded pyranometer, because of the latter’s thermal imbalance

and cosine error. Such improved techniques and studies need to be replicated in different cli-

mates around the world to construct better clear-sky diffuse algorithms and correct historical

data of diffuse and global irradiance if possible.

20. Estimating the irradiation on inclined planes

The final scientific issue I will dwell on briefly is the problem of the estimation of the diffuse

sky radiation incident on inclined planes. The radiance distribution of the sky would be needed

for this but is rarely monitored. Models exist for clear skies of different turbidity and for over-

cast skies. The all-sky issue is more complex. In the 4th European Solar Radiation Atlas [13],

we preferred a modified form of the Muneer model [16] as described in [13]. In general, the

Perez model [17] has gained favour internationally, but our detailed EU regional studies using

observed data sets did not confirm this choice for European conditions.

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21. Additional radiation related studies with which the author has been associated

Applications tools are very important for many professional activities. The building engineer-ing services design groups have an important need for predigested information concerning theimpacts of climate on building engineering decision making. The Chartered Institution of Build-ing Services Engineers has devoted considerable resource to the development of their Guide J,Weather and Solar Radiation data [18]. This publication contains considerable information onthe radiative climate arranged in forms suitable for engineering design. Both UK and inter-national data are included. The issues of daylight availability are addressed too. The productionteam believe that it is one of the most advanced Guides of its kind in the world. The radiationsections of the publication drew strongly on the author’s experience on EU projects. Thisreflects the need to adopt professional approaches that have a sound trans-European Unionfoundation.

Wide spread use has been made of the METEONORM CD-ROM based design tool overmany years. Meteotest of Bern Switzerland, who developed the earlier versions of METEO-NORM, were interlinked as full partners into the EU sponsored Soda-IS programme [1]. Thisexperience has enabled Meteotest to produce a new considerably improved version of METEO-NORM, METEONORM 5 [19]. The author played a considerable role in the evolution of thenew improved algorithmic structure embedded in the product. The principle algorithmic issuesare fully described in the Handbook embedded in the CD-ROM.

A more specialised study has also been prepared concerning the impact of radiation clima-tology on photovoltaic system design, refer Page [20].

22. Current challenges

It is clear that a gap exists between meteorological measurements (including radiation) andthe effective use of that kind of data for applications. There is the fundamental atmosphericscience need for a better understanding of the details of radiative transfer at different levels inthe atmosphere. There are still enormous gaps in our knowledge concerning radiative transferthrough different types of clouds. Predictions of ground-level irradiance below clouds obtainedusing satellite observations have been hampered by lack of information about the transmissionproperties of the different cloud types involved. Cloud type data have not been available withinHeliosat 2. The current EU Heliosat 3 programme has access to a considerable additionalamount of data provided by the latest European satellite. This should open the prospect ofimproved results under overcast conditions using detailed cloud characterisation data.

23. Proposed road map for the future

I will conclude by suggesting a road map for the future, setting down various goals to be fol-lowed to help close some of the gaps.

23.1. The measurement and data processing agenda

1 I

mproving the definition of data requirements for different fields of study involving solar radi-ation measurement and data, giving full attention to the significance of daylighting studies.

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We require more precise statements concerning the various scientific data needs. Requestedneeds have to respect our actual current practical instrumental capacity to deliver therequested physical measurements at the required levels of accuracy stated.

2 I

mproving our knowledge of the actual terrain exposure of various instruments in use and theconsequent errors likely to be encountered in their field use. More importance must be attached to providing accurate meta-data describing the specificenvironment of ground measurement sites and their geographical exposure. The impact ofsurrounding terrain needs to be revealed to potential data users. Systematic methods toapply corrections for terrain exposure are needed. These techniques are especially impor-tant in mountainous areas. Otherwise systematic data mapping becomes impossible in ter-rain obstructed areas.

3 E

ncouraging the development of improved instrumentation. The economics preclude wide spread attempts to devise new instrumentation. This is bestdone at major centres with the advanced scientific capacity needed to do it. We basicallyneed instruments of international calibre.

4 E

xpanding the number of site measuring diffuse radiation with modern accurateinstrumentation. The experience of the EU has demonstrated that lack of accurate diffuse radiation meas-urements introduces substantial difficulties in the estimation of inclined surface irradiation.It is desirable to replace shadow band shading techniques with shading disks of inter-nationally defined dimensions.

5 I

mproving links between groups carrying out well calibrated spectral irradiance measurementsand the rest of the solar radiation measurement communication. The specialised groups working on spectral irradiance over parts of the spectrum do notseem to be in good communication with the rest of the solar radiation measurement com-munity. There is a lack of knowledge about the diffuse spectral irradiance under overcastand partly clouded conditions. More measurements of the spectral radiance could helpachieve a better understanding of how best to convert horizontal surface diffuse radiationto inclined plane diffuse irradiance. Currently knowledge of the spectral irradiance fromclear skies dominates. In many climates, cloudless skies are relatively rare

6 R

ecognising the importance of good atmospheric models. When comparing measured data and model predictions, we are never sure if the modelsare wrong or the measurements—or both.

7 R

ecognising the importance of international collaboration. Many years ago, the EU started to recognise that solar radiation modelling and resourcemapping are important scientific topics. They invested in many well-directed programmes:

. firstly, to build up fundamental knowledge;

. secondly, to institute proper quality control of existing observational data;

. thirdly, to combine ground-based information with satellite information;

. finally, to apply that systematic knowledge to make application information readily avail-able to users in user friendly forms exploiting IT for information transfer, through theuse of computerised digital mapping techniques.

J. Page / Energy 30 (2005) 1501–15151512

This recognition needs to expand to other countries/continents. An International Confer-ence such as this one helps serve this goal.

8 C

reative multicultural team building. In all EU sponsored research work, team work involving scientific institutes from severalmember countries has been an essential ingredient for successful research approval. Teamworking can always be improved. The world is a big place and using experience from dif-ferent countries helps avoid the assumption that the characteristics of your own atmos-phere apply in all other countries.

9 A

chieving more effective use of satellite observations in the estimation of the components ofsurface irradiation s linking satellite data to quality-controlled observed ground data. This was an important objective in the EU Programme that led to the development of theSoDa website [1]. A better worldwide climate databank needs to be built, including satel-lite data to supplement limited ground observations. Good quality control will be essential.Developing better satellites with more spectral channels and algorithmically harnessingthem to advanced data extraction programmes such as Heliosat 3, so improving associatedsoftware programs that will open the door to improved radiation data services. The pro-vision of improved ground truth data is essential support this advance. Better ground truthdiffuse radiation data especially will contribute to achieving higher accuracy estimates ofthe components of radiation using satellites.

10 R

educing gaps, errors and questionable quality control in the large number of data setsavailable. Gaps in data produce difficulties in the many applications areas where numerical simu-lation of system performance is often. Science based methods for filling gaps play animportant role.

23.2. The applications agenda

11 R

esponding more effectively to the complex climatic information needs of users in a variety ofapplied fields. These applications include agriculture, land drainage, water supply, transport, environ-mental control, energy supply and distribution, and, even more directly, construction.

12 H

elping to meet the increasing concerns about health and the environment. Providing improved understanding of the role of climate knowledge in health-policydecision making. SoDa-IS addressed, for example, the issues of estimating UV radiationon a worldwide basis.

13 E

nhancing the understanding of climate as a pollution redistributor. We currently have relatively weak knowledge how aerosols are raised into the air andredistributed into other regions of the world. Studies of radiance patterns obtained by sat-ellites linked to ground level turbidity measurements could help identify the origins of vari-ous pollutants and their subsequent global redistribution.

14 E

mphasizing the importance of the built environment to climate change and supporting build-ing design with appropriate data.

1513J. Page / Energy 30 (2005) 1501–1515

Sustainable building needs to be properly guided through the application of relevant user-friendly climatologies for each part of the world. As buildings normally last a long time,estimated future solar radiation under different energy scenarios is needed for effectivedesign.

15 R

ecognizing the inescapable increasing use of Information Technology (IT) in the form ofweb databases, dynamic question/answer processes, expert advice, etc. This activity is well recognised in the SoDa-IS programme.

16 H

elping governments cope with the public pressure to take care of climate change, healthissues and environmental problems. The future of solar radiation climate is part of the vision. Global warming will producereduced solar radiation in some areas of the world. This contrasts with the popular high-latitude assumption that a warmer climate will necessarily become a sunnier climate.

17 H

elping international bodies like CIE, WHO, UNEP, each with their specialised concernslinked to radiation, such as cataracts, skin cancer, sleep/wake cycles. Refer, for example,Brainard and Glickman, [5] . Meeting other special demands where spectral radiation dataare essential.

18 P

roviding improved data to help in the assessment of climate as an economic and environmen-tal resource, noting the special emerging importance of the renewable energy sector.

19 A

dvising policy makers (WMO, UNEP, etc.) on the impact of solar radiation on the waterbalance of countries through its influence on potential evaporation. The impacts of evapor-ation on the limited water resources available for the future of urbanism and agriculture areconsiderable. This is especially true in hot countries with seasonal rainfall.

20 P

resenting climate change as a dominating research topic. Demonstrating more effectively theinfluence of international, national and regional development policies based on a solar radi-ation agenda, and provide them with the radiatively based tools needed to support the goalof achieving sustainability.

21 R

esearching the influence of solar radiation on issues like sea level rise and wave surge risks ina world where a significant fraction of its economic activity is located close to the sea and istherefore at risk.

22 I

mproving the capacity to provide long-term forecasts of climate many months ahead,especially forecasting the solar radiation climate (e.g., El Nino-type impacts).

23 S

upplying or improving climate advice to reduce the impacts of climate disasters through bet-ter disaster management.

24 M

aintaining a mailing list of solar radiation experts who can help on the above applicationsissues, inter-connected through the world wide web.

I am afraid it is a long list. That is what makes solar radiation studies so important for ourfuture. I am sure the Conference on Measurement and Modelling of Solar Radiation & Day-light will considerably help in these tasks by gaining momentum in the solar radiation com-munity. I wish this new venture a long life and invite you all to participate in its next meeting,to be held in Athens, Greece, in 2005.

J. Page / Energy 30 (2005) 1501–15151514

References

[1] Ecole des Mines de Paris at Sophia Antipolis: Project Coordinator Wald L. Integration and exploitation of net-worked Solar Radiation databases for environment monitoring, the Soda-IS project. Visit Project dynamic userinteractive site at http://www.soda-is.com.

[2] Rigollier C, Lefevre M, Wald L. The method Heliosat-2 for deriving short wave solar radiation from satelliteimages. Submitted to Solar Energy 2004 (in press), doi: 10.1016/j.solener.2004.04.017.

[3] Rigollier C, Bauer O, Wald L. On the clear sky model of the 4th European Solar Radiation Atlas with respect tothe Heliosat method. Solar Energy 2000;68(1):33–48.

[4] Remund J, Wald L, Lefevre M, Ranchin T, Page JK. Worldwide link turbidity information. Proceedings of theISES Conference, Gotenborg, Sweden, June 14–19th 2003. Freiburg (Germany): International Solar EnergySociety; 2003.

[5] Brainard GC, Glickman G. The biological potency of light in humans: significance to health and behaviour.Proceedings of the CIE Conference, Section I, Light & Human Health. 2003. I-22–I-33.

[6] Gueymard CA. Parameterized transmittance model for direct beam and circumsolar spectral irradiance. SolarEnergy 2001;71:325–46.

[7] Page JK. A user friendly IT based spectral module for estimating beam and diffuse UVA & UVB irradianceson inclined surfaces. Proceedings of the CIE/Arup Symposium on Visual Environment, April 24th and25th, 2002, London. Paris: CIE Publication x024:2002: ISBN 3 901 906 16 9, 2002. 28–34.

[8] Hopkinson RG, Petherbridge P, Longmore J. Daylighting. London: Heinemann; 1966.[9] Kittler R. Standardisation of outdoor conditions for the calculation of the Daylight Factor with clear skies. Pro-

ceedings of the Conference on Sunlight in Buildings, Newcastle 1965, Rotterdam, Boucentrum. 1967. 273–86.[10] Page JK. Visual environment—the symposium context. Proceedings of the CIE/Arup Symposium on Visual

Environment, April 24th and 25th, 2002, London. Paris: CIE Publication x024: 2002: ISBN 3 901 906 16 9.2002. p. 5. Several other papers in this meeting discussed the role of the selected historic pioneers of daylightingdesign, RG. Hopkinson, G. Pleijel, and J. Krochmann.

[11] Palz W, Grief J, editors. European solar radiation atlas, 3rd improved and revised edition including disks.Heidelberg and New York: Springer-Verlag; 1996 ISBN 3-540-61179-7.

[12] Grief J, Scharmer K, editors. European Solar Radiation Atlas 4th Edition including CD-ROM with tool box.Scientific Advisors: Dogniaux R, Page JK. Authors: Wald L, Albuisson M, Czeplak G, Bourges B, Aguiar R,Lund H, Jukoff A, Terzenbach U, Beyer HG, Borisenko EP. Published for the Commission of the EuropeanCommunities by les Presses de l’ Ecole des Mines de Paris in 2 volumes. Volume 2 ‘‘Data base and exploitationsoftware’’ is the document that contains the scientific detail, 2000.

[13] Randall M, Leonard SL. Reference insolation data base: a case study with recommendations. In: Report ofSolar Energy Data Workshop November 1973 Report No. NSF-RA-N-74-062, September 1974. Turner C, edi-tor. National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Silver Spring,MD: 1974.

[14] WMO World Radiation Data Centre. St. Petersburg. The world data are now accessible on line at http://wrdc.mgo.rssi.ru or at http://wrdc-mgo.nrel/gov. The series currently appears to end in 1993.

[15] Baseline surface radiation network, BSRN, World Radiation Monitoring Centre, Division of Climate Research,Institute of Geography, ETH, Zurich. Requests for the observed data are made to http://bsrn.ethz.ch.

[16] Muneer T. Solar radiation model for Europe. Building Services Engineering Research and Technology1997;11(4):153–63.

[17] Perez R, Ineichen P, Seals R. A new simplified version of the Perez diffuse irradiance model for inclined surfaces.Solar Energy 1987;39:221–31.

[18] Chartered Institution of Building Services Engineers. CIBSE Guide J, Weather and Solar Radiation Data.London: Published as a CD-ROM by the Chartered Institution of Building Services Engineers, 222, BalhamHigh Road, London SW12 9BS. 2000. J.K. Page prepared very significant sections of this Guide including solarand illuminance data, also long-wave radiation exchange and sol–air temperature The radiation sections of theGuide align algorithmically with the European Solar Radiation Atlas.

1515J. Page / Energy 30 (2005) 1501–1515

[19] Remund J, Kunz S. METEONORM Version 5.0. Bern, Switzerland: Bern METEOTEST, Fabrikstrasse 14, 3012Bern, Switzerland. 2003. This CD-ROM based product links closely to the SoDa-IS project [1]. J.K. Page wasclosely associated with the improvements now incorporated in the latest version of METEONORM.

[20] Page JK. The role of solar radiation climatology in the design of photovoltaic systems. In: Marvart T, CastanerL, editors. Practical handbook of photovoltaics: fundamentals and applications. Oxford: Elsevier; 2000, p. 8–66.