*3.3. Economical Analyses*

Due to varying investment costs depending on supplier and client, several offers for the described technologies were obtained to determine the costs for the case study and the mean value was chosen for further consideration. The investment costs include all associated costs as well as set-up and commissioning cost. For the annual costs of the investment the straight-line depreciation for a period of 15 years for the boiler and 10 for all other technologies and the steam accumulator is applied. The annual costs for the technologies *Ctechnology* are the sum of depreciation costs *Cdepr*, the fuel costs for biomass *pBM*, natural gas *pNG*, biogas *pBG*, biomethane *pbiomethane* and electricity *pel*. Equation (7) shows an example for calculating the costs for the concept with the biomass boiler. All technologies without electricity generation are calculated accordingly.

$$\mathcal{C}\_{BM} = \mathcal{C}\_{depr} + E\_{steam,BM} \cdot p\_{BM} + E\_{steam,B} \cdot p\_{NG}.\tag{7}$$

The electricity generation costs for the FC *Cel*,*FC* and the MGT *Cel*,*MGT* are added to the annual costs and the earnings from the usage of the generated electricity or selling *Sel* it to the grid are subtracted from the annual costs (Equation (8)).

$$C\_{\rm FC} = C\_{\rm depr} + E\_{\rm steam, FC} \cdot p\_{\rm biomass} + E\_{\rm steam, B} \cdot p\_{\rm NG} + C\_{\rm el, FC} - S\_{\rm el} \tag{8}$$
