The solar energy resources in the building stock is assessed in several steps of which the key features are presented in the table below.

Solar-architectural key features for the assessment of the buildings and their potential for solar energy purposes (photovoltaic and thermal)

Major characteristics	Descriptive and analytical elements
Solar characteristics	• Irradiation (general in the area concerned) • Yield (specific for the surfaces concerned) • Shading caused by elements other than construction features of the building concerned, e. g. trees, neighbouring buildings, wider horizon)
Architectural characteristics	• Shape (eight basic types of roof forms) • Construction features of the relevant building skin parts (e. g. chimneys, windows, terrasses, HVAC, etc.)
Other characteristics	• Listed buildings • Cultural / historical zones

With respect to the solar irradiation, it can be stated that sunshine is quite generous a) for the Canton of Geneva as a whole (if compared to other densely populated areas in Switzerland) with 1350 kWh per square meter of optimally oriented surface and b) for a wide range of differently oriented surfaces, too. Examples can illustrate the latter point (compare with the figure below):

1. a surface oriented south yields at least 90% of the maximum annual solar irradiation if it is tilted between 2° and 62°

2. a surface tilted by 25° yields at least 90% of the maximum annual solar irradiation if it is oriented between — 67° et 67°, thus grosso modo between ESE and WSW.

3.

Solar Irradiation in Relative Terms of Maximum Yearly Yield (Solar Criteria) for Different Surfaces (Tilt and Orientation) — Location: Geneva-Cointrin 180- 150- 120 * 90- 60- ЗО* 0* — ЗО* — Є0* -90* -120* -150* -180* Orientation (Azimut)

о 95%-IOO% □ 90%-85% o85%80% o80%-85% □ 75%80% ■70%-75% ■65%-70% ■60%4′;5% ■55%«% ■50%-55% ■45%-50% ■«%-«%

a horizontal surface still yields 89% of the maximum annual solar irradiation.

Solar irradiation in relative terms of maximum yearly yield (solar criteria in % of 1350 kWh per square meter and year) for different surfaces (tilt and orientation) — location: Geneva- Cointrin

□ □ bailments

В □ batiments

H □ parcelles I I <all other values^ PROPRI_PUB 0СДР; СЕН; CFF; C 0 □ 0 0

communes

0 0 orthophoto В D mns_relief_ge В □ Plan de ville E 0 MNS 0 0 partiel_lm 0 0 partie2_lm 0 0 partie3_lm 0 0 partie4_lm 0 0 partie5_lm 0 0 partie6_lm

?Іх]

Identify (ram: | batiments_pub

Location: І497182.74 Л1Є175.75

SHAPE

Polygon

COMMUNE Onex NO_COMM 34 NO_BATIMEN 1315

BATDDP

DATEDT DESTINATIO Salle despoil NOMENCLATU 4.5.2 NOME N_CLAS E quipement collectif PROVENANCE autie

SURFACE

OBJECTID 43093S3

EPOQUE SHAPE_AREA 829.90775 SHAPE_LEN 11Є. 037047

The buildings and their surfaces are subsequently attributed to 19 categories while being visually assessed with GIS. First category comprises horizontal surfaces (e. g. flat roofs), the other 18 categories are defined through six orientation sectors (steps of 30°) and three tilt classes (moderate, medium and high tilt). An illustration of how the view and statistical data are screened is shown in the figure below.

Screenshot of aerial picture and statistical data provided by the GIS. Source: SITG

The different elements — both positively and negatively influencing the suitability of the building with respect to solar energy uses — are summarised on sequenced quality levels and aggregated in respective indexes providing quantitative reference values. The table below presents the global analysis results of the approx. 1700 public buildings assessed.

Levels of solar-architectural suitability and reduction factors Surfaces Suitability index Ground floor area 1’888’400 m2 1.00 Roof surfaces with suitable exposition (good solar yield) 1‘447‘921 m2 0.77 Reduction factor « construction — obstruction » 44.8% Roof surfaces with suitable exposition and architecture 799‘517 m2 0.42 Reduction factor « shading » 18.6% Solar-architecturally suitable surface 650‘546 m2 0.34

Levels of solar-architectural suitability and reduction factors as well as resulting surfaces and global suitability indexes (reference ratio « suitable area / ground floor area »)

A first assessment round is dedicated to the public buildings in Geneva, which belong either to the municipalities or to the canton and with a minimum ground floor area of 300 m2. A second assessment round is dedicated to a representative selection of buildings of the whole building stock in the territory.

Intermediary results based on the approx. 1700 objects assessed are available for the « geometry » potential, i. e. solar-architectural suitability of the building skin given. These results range from basic descriptions of the building stock in terms of building types, age structure, property structure, roofscape, etc. to elaborated analysis of the solar — architectural suitability of the public building stock for solar photovoltaic and thermal

570 public buildings have been identified with a tilted roof area being solar — architecturally suitable (minimum solar yield is 90%) for photovoltaic applica­tions. The most important system class in relative terms is the size category from 10 to 30 kWp with a share of 47%.

729 public buildings have been identified with a horizontal / flat roof area being solar-architecturally suitable (minimum solar yield is 90%) for photovoltaic appli­cations. The most important system class in relative terms is the size category from 10 to 30 kWp with a share of 40%.

203 public buildings have been identified with a tilted roof area being solar — architecturally suitable (orientation south ±30°) for solar thermal applications. The most important system class in relative terms is the size category from 100 to 300 m2 with a share of 42%. The solar active collector is calculated on a basis of 1 m2 of suitable roof area is equivalent to 1 m2 of suitable active collector area.

738 public buildings have been identified with a horizontal / flat roof area being solar-architecturally suitable for solar thermal applications. The most important system class in relative terms is the size category from 100 to 300 m2 with a share of 42%. The solar active collector is calculated on a basis of 3 m2 of suitable roof area is equivalent to 1 m2 of suitable active collector area.

applications. Hereunder, a set of results concerning the relative distribution of potentially installable system size classes is given for the public building stock assessed.

Currently, more implementation relevant issues (e. g. age and stability of building roofs, construction work envisaged, legal and financial issues, social and communal acceptance and willingness, etc.) are under analysis in close collaboration with the municipalities concerned. More results will be published in a report later this year.

Le Potentiel Solaire dans le Canton de Geneve

Analyse et Evaluation du Potentiel Solaire — Photovoltai’que et Thermique — dans le Parc Immobilier Public du Canton de Geneve

Front picture of the future report on the solar energy potential in the Canton of Geneva.