Solar-Energy Surface Potential 2005
As long-term possible contributions of solar systems to the energy supply of Berlin, the following values were ascertained by the investigation:
- solar-thermal energy for heat supply: 12 % (cf. Table 3)
- photovoltaics for power supply: 9 %.
This is the perspective for 2050.
Neither the inner-city housing blocks typical of Berlin nor the functional buildings of the post-war period, nor the commercial districts built during the ‘80s are ideal for the current mobilization of areas for solar utilization, since solutions can at present be realized here economically only with some difficulty.
Figure 2 shows comparison of the distribution of surfaces available for solar-energy utilization by urban-space type. Berlin had around 3,390,000 inhabitants in 2005. The total potential urban solar-energy surface on roofs is 10.40 sq.m. per inhabitant, and 3.38 sq.m. per inhabitant on façades, for a total of 13.78 sq.m. per inhabitant in Berlin. The single-family homes of the post-war period (Urban-Space Type 11) have the greatest potential, with a urban solar-energy surface potential (roofs and façades) of 6,480,000 sq.m. in the capital. In terms of solar-urban roof-surface potential, the Post-War Commercial and Industrial Areas (Urban-Space Types 13, 16, 20), the Housing Estates of ‘50s and ‘70s (Urban-Space Types 7 and 9) and Functional Buildings the ‘50s, ‘60s and ‘70s (Urban-Space Type 12) stand out.
The main thrust of further more intensive investigations for the concretization of possible potential for the installation of solar-technology systems will be toward for the following urban-space types:
- Social housing of the ‘50s, row buildings
- Multi-storey housing of the ‘70s
- Single-family home areas of the ‘50s, ‘60s and ‘70s; and
- Commercial and industrial area of ‘50s, ‘60s and ‘70s.
Moreover, there are particularly favorable possibilities for including solar-energy goals in all projects on construction sites. Here, the investigation will focus primarily on future single-family home and multi-storey housing areas, and also on large-scale service areas.
Table 3 shows a summary of long-term potential contribution of solar-thermal energy to the heat supply in Berlin, by urban-space type.
The Significance of the Solar-Energy Surface Potential for Berlin’s Climate-Protection Goals
The results of the investigation of solar-energy surface potential also indirectly permits inferences regarding CO2 reduction potential via solar-energy use. The potential for solar power production comes to 1,093,720 MWh/yr. Complete exploitation of the solar-power potential ascertained would mean a CO2, saving of approx. 732,792 tons annually. That would be equal to almost 8.5 percent of the CO2 emissions of approx. 8,665,780 tons caused in 2000 by the entire Berlin power consumption of 12,934,000 MWh.
Although the calculated reduction of 8.5 percent is based on a comparison referenced to today’s power-plant stock in Germany, its efficiency and its structure of power-generating facilities, it is nonetheless clear that solar energy could make a considerable contribution to CO2 reduction.
The level of potential CO2 savings through the use of solar-thermal systems depends on the CO2 emissions factors of the fuels replaced by solar energy. If natural gas is assumed to be the main fuel, the equivalent CO2 value of a heat quantity of one kilowatt hour produced with natural gas amounts to 310 grams. The total potential for solar-thermal heat production of 17,160,612 MWh thus enables a CO2 savings of approx. 5,319,790 tons per year.
In order to fully exploit both the photovoltaic and the solar-thermal energy potential of much of the building stock suitable, in terms of the orientation of roofs and façades, for solar utilization, the structural and technical prerequisites for the installation of solar systems must first be created. This can only be accomplished in the context of necessary redevelopment measures oriented towards the replacement cycles of the components.
In order to fully exploit the solar-thermal potential, additional prerequisites are necessary. The heating systems must be compatible with solar-thermal systems, and placement areas must be available for the hot-water tanks. The efficiency of solar-thermal energy is maximized when it is used to provide home heating, in connection with reduced heating requirements for buildings, and with large-area heating systems.
In order to achieve the long-term climate-protection goal of 80 % CO2 reduction by 2050, the potential of both solar-thermal energy and photovoltaics will have to be realized, combined, moreover, with high-quality energy rehabilitation and energy-efficient new buildings.
Berlin has the advantage that large portions of its building stock have already been modernized over the past two decades, either in urban-renewal areas, in publicly subsidized housing areas, or in concrete-plate housing estates.