Analysis Results of Collectopia Cross-Simulation (EIFER-EDF-AIT)

Analysis Result Description

1- Eifer investigated four different scenarios to find a best solution for Collectopia

• Scenario 1: 'Reference' case study
  • all technologies are available for choice
  • no constraints except the constraints usually applied like process transformation, energy balance, demand supply
• Scenario 2: with CO2eq constraint
  • same than scenario #1 with CO2eq cap: 265t/year
  • 1990 CO2eq emissions: 0.9t/p/year (electricity and heat production)
• Scenario #3: with CO2eq price
  • same than scenario #1 with CO2eq price
  • 80€ per emitted ton of CO2eq per year

Assuming electricity costs of 18 ct/kWh, gas import costs of 7 ct/kWh, CO₂ emissions of 80 g/kWh electrical energy and 230 g/kWh for gas, the annual costs for the different scenarios increase from 517 T€ for the reference scenario #1 to 601 T€ for the scenario #2 with a CO₂eq constraint. Fig. 15 depicts the costs for the different scenarios. By adding costs for CO₂ emissions, the net expenditures naturally go up. However, the amount of gas imported is still high, as can be seen in Fig. 16. The gas import and thus, the CO₂ emission can be effectively reduced by the utilization of an aquifier (scenario #4), which can be derived by the cash flow comparison of scenario #1 and #4. A more detailed analysis reveals that in case of scenario #4 a great part of the gas boilers will be replaced by centralized heat pumps The Combined Heat Power plants (CHP) generation capacity is not at all considered in the energy generation mix and local PV generation only slightly increases compared to the reference scenario (Fig. 17). The total emitted CO₂ can be reduced by 85 % from about 1000 T/a to 137 T/a. Additionally, it is remarkable that there will be no investment in different storage technology like batteries.

2- The key conclusions of the strategic planning for Collectopia are:

• Large thermal storage capacities facilitate the integration of large amounts of renewable heat in an economic way.
• The sizing of thermal storage is key for economic heat and electricity supply of an efficient newly‑build residential eco-district.
• For seasonal (mid/long-term storage) aquifer thermal energy storage systems (ATES) are preferable.
• For short term storage, water tanks are favorable.
• The supply of an eco-district under tight CO2 constraints will gravitate towards local electricity consumption in case of a high CO2 intensity of the public electricity mix while in the opposite case, the use of local resources will remain moderate.
• Likewise, the potential for CO₂ emission reduction through thermal storage increases with the CO₂ intensity of the public electricity mix, or decreases respectively.

3- AIT investigated phase change material (PCM) storage system and successfully developed latent heat storage models. The models were implemented in Dymola/Modelica. Furthermore, AIT investigated suitable integration scenarios within the Collectopia Energy System. Decentralized PCM storages are especially interesting at the Greenhouse and within the residential buildings to serve as short-term buffer on a daily/hourly basis. They help to cut peak power demands and distribute the load more evenly during the day, which is beneficial for equipment efficiency. By the installation of a 650 kWh PCM-storage at the Greenhouse peak power demand reduces by 26.7% from 150 kW to 110 kW (cf. Figures below). For the residential buildings a 115 kWh PCM-storage helps to eliminate the domestic hot water and space heating peak in the morning. As a consequence, the heat pump peak power can be reduced by 38.5% from 65 kW to 40 kW.