How do the numbers emerge?
In terms of a more decentralised approach to energy supply, the objectives of the planned measures are to
1) Exploitation of the local potential for electricity generation through photovoltaics (PV) and wind energy to cover the share of electricity demand currently still covered by fossil energy sources plus the additional demand through sector coupling (e-mobility, heat pumps, hydrogen production),
2) temporal balancing between the supply of electricity from renewable energy and consumption on site: smart grid, distributed storage capacity, local plants for power-to-gas and reconversion via combined heat and power (CHP).
This means that local generation is assumed to be as high as possible in order to limit supra-regional electricity transport and the associated grid expansion. The surrounding area (e.g. district) offers additional capacities beyond the local demand, especially in the areas of wind energy and (agro)photovoltaics. However, this potential is not taken into account here.
The electricity demand in 2030 is estimated taking into account the demand of all sectors (households, industry, commerce/trade/services, transport) and taking into account both savings potentials (sufficiency expectation factor 90%) and additional demand, e.g. due to e-mobility, heat pumps and electrolysis. In the process, 18% is assumed for hydrogen production for industry and CHP plants. The latter
The latter cover the demand at times when there is not enough electricity from PV and wind (keyword “cold dark period”). This results in a demand of approx. 453 GWh per year to be covered by local expansion, which is distributed among the different types of generation as follows:
a) 188 MWp photovoltaic roof area, of which 14.7 MWp will be realised in 2020 (potential according to the solar cadastre of southern Lower Saxony is 296 MWp),
b) 167 MWp photovoltaic open space and 31 MWp agro-photovoltaic,
c) 34 MWp wind power (onshore).
MWp means installed capacity (“peak”). Agro-photovoltaics are PV systems on agriculturally used land. It is assumed that the equivalent of 950 hours of full load hours/year will be achieved for photovoltaics and 2500 full load hours/year for wind power. The expansion can, of course, be distributed differently across the various sources if the potential is available, in order to cover the assumed electricity demand. About 407 GWh will still be required from the public grid in 2030, i.e. 239 GWh or 37% less than in 2018. It is assumed in the CO2 balance that 100% of the grid electricity will also be generated in a climate-neutral way in 2030 – if not, the remaining fossil share must be taken into account in the balance. The electricity balance also includes a contribution of 31 GWh per year from the pyrolysis (see below) of biomaterial.
Overall, the electricity demand in 2030 is about one third higher than in 2018, at 860 GWh; this is due to the conversion of heat supply from renewable energy (heat pumps, etc.), hydrogen production for CHP plants and industrial heat, and the growth of e-mobility. A sufficiency factor of 90% (10% savings) is assumed. With the energy refurbishment of the remaining building stock and the increasing number of electric vehicles, the demand for electrical energy will increase further after 2030.
The financial and personnel costs for expanding the power supply from renewable energy are determined on the basis of the following assumptions:
– Roof-mounted photovoltaics: 840,000 € and 2 FTE per MWp
– Ground-mounted photovoltaics: 600,000 € and 2 FTE per MWp
– Agrophotovoltaics: 750,000 € and 2 FTE per MWp
– Wind power: 1,423,000 € and 4.7 FTE per MWp
– PV for electrolysis/CHP: 6,531,000 € and 3.9 FTE per MWp
– ditto. Wind power: 5,010,000 € and 6.6 FTE per MWp
(FTE = full-time equivalents, i.e. the work of an employee in one year).
It would make a lot of sense to install local storage units for solar electricity in the residential buildings, which could cover a good part of the private electricity demand in the evening and night hours. This could save some of the high investments for electrolysis/CHP. This is not considered in the current plan.
For the municipality, a share of 5% of the investment costs is assumed, which is mainly for PV (roof and open space) on municipal properties (municipal buildings and residential buildings of Municipal Housing). Electrolysers and CHP plants can be operated by municipal utilities or private investors. Additional staff for the Stat concerns planners for the municipal share of the investments, for energy master plans and for outreach energy advice for electricity and heat (assumption of an average of 3 working days per advice with preparation and follow-up for a total of approx. 20,000 buildings, i.e. 2,000 buildings per year).
The running costs are, on the one hand, the personnel costs for the city (own or contracted personnel) and, on the other hand, the costs for the maintenance (maintenance and repair) of the PV and wind power plants as well as the electrolysers and CHP plants between 2% and 3% of the investment per year. The calculation takes into account that the plants will be built up gradually over 10 years.