7 Case study

The case study focuses on three different districts of Geneva represented in the Figure 7.1. Each of these districts has different characteristics.

Figure 7.1: Map of selected neighborhoods

The first district is Vessy, which is located in the southeast of the map. It is a residential area that is completely composed of individual houses and has 23 buildings. The vast majority of these buildings were constructed between 1981 and 1990.

Figure 7.2: Sunburst diagram of the end use demand of Vessy

The second district of the case study is Florissant which is located between the two other districts on the map. This neighbourhood is mainly composed of residential buildings with two that also have shops and one that is purely an administrative building. One of the two commercial buildings is the building with the highest consumption in the neighbourhood. Most of these buildings were constructed between 1961 and 1980 and some were built before 1919. It is important to specify the period of construction of the buildings, as this will have an impact on the quality of the insulation.

Figure 7.3: Sunburst diagram of the end use demand of Florissant

The third district is Jonction, which is located to the west on the map. These nine buildings are located near the confluence of the Rhone and Arve rivers. This district is a residential district where almost every building is composed of another class of building such as administrative, industrial or educational buildings. This district is a little different from the other two, as it is made up of old buildings that have been renovated or extended in subsequent years.

Figure 7.4: Sunburst diagram of the end use demand of Jonction

In the three sunburst diagrams, it can be seen that space heating (SH) has the highest end use demand compared to the electricity demand (Elec) and to the district hot water (DHW).

The table below shows the useful values of the three districts for the rest of the case study. The Energy Reference Area (ERA) represents a specific area used as a reference for calculating or evaluating energy-related quantities or performance metrics. It allows to compare the energy end-use of two district having different size. For example, it can be seen that the ERAs for Jonction and Florissant are around 23 higher than those for Vessy.

Table 7.1: Useful values of the three districts
District	ERA [\(m^2\)]	Solar roof aera [\(m^2\)]	Maximal domestic electricity power [kW]
Vessy	6374	5161	46.378
Jonction	148662	37932	1000
Florissant	140513	21695	972.5

The following case study will analyse the different optimisations carried out for each of the three districts for a system not using fossil fuels, with the aim of answering the research questions. It has been decided to add an additional feature at each stage to analyse the impact of this modification on the optimisation result. To begin with, a comparison is made between the two optimisation modes, building-scale (= decentralised) and district-scale (= decomposed) optimisation. Next, the grid constraints were added to the district-scale optimisations. Two different constraints were set to compare their impact on the system. Then, the “pv_orientation” functionality present in REHO is used to take into account the position of the photovoltaic panels as well as the shadows on the solar surfaces. Next, the case study will analyse the effect of the stochasticity that has been modelled in this project. Three values of standard deviation of the time-shift have been tested. Finally, the impact of certain storage systems on energy communities was tested. The means of storage can be modelled by electric batteries, by electric vehicles or by other systems present in REHO. It should be noted that thermal storage systems such as tanks for space heating or for domestic hot water are present from the first optimisation.