add HVDC underground

Author: fneum

inputs/manual_input.csv

@@ -48,6 +48,9 @@ HVDC overhead,FOM,2030,2,%/year,2011,"Hagspiel et al. (2014): doi:10.1016/j.ener
 HVDC submarine,investment,2030,970,EUR/MW/km,2017,Härtel et al. (2017): https://doi.org/10.1016/j.epsr.2017.06.008 .,Table 1
 HVDC submarine,FOM,2030,0.35,%/year,2018,Purvins et al. (2018): https://doi.org/10.1016/j.jclepro.2018.03.095 .,"Based on estimated costs for a NA-EU connector (bidirectional,4 GW, 3000km length and ca. 3000m depth). Costs in return based on existing/currently under construction undersea cables."
 HVDC submarine,lifetime,2030,40,years,2018,Purvins et al. (2018): https://doi.org/10.1016/j.jclepro.2018.03.095 .,"Based on estimated costs for a NA-EU connector (bidirectional,4 GW, 3000km length and ca. 3000m depth). Costs in return based on existing/currently under construction undersea cables."
+HVDC underground,investment,2030,970,EUR/MW/km,2017,Härtel et al. (2017): https://doi.org/10.1016/j.epsr.2017.06.008 .,Table 1 (same as for HVDC submarine)
+HVDC underground,FOM,2030,0.35,%/year,2018,Purvins et al. (2018): https://doi.org/10.1016/j.jclepro.2018.03.095 .,"Based on estimated costs for a NA-EU connector (bidirectional,4 GW, 3000km length and ca. 3000m depth). Costs in return based on existing/currently under construction undersea cables. (same as for HVDC submarine)"
+HVDC underground,lifetime,2030,40,years,2018,Purvins et al. (2018): https://doi.org/10.1016/j.jclepro.2018.03.095 .,"Based on estimated costs for a NA-EU connector (bidirectional,4 GW, 3000km length and ca. 3000m depth). Costs in return based on existing/currently under construction undersea cables. (same as for HVDC submarine)"
 HVDC inverter pair,investment,2030,150000,EUR/MW,2011,"Hagspiel et al. (2014): doi:10.1016/j.energy.2014.01.025 , table A.2 .",
 HVDC inverter pair,lifetime,2030,40,years,2011,"Hagspiel et al. (2014): doi:10.1016/j.energy.2014.01.025 , table A.2 .",
 HVDC inverter pair,FOM,2030,2,%/year,2011,"Hagspiel et al. (2014): doi:10.1016/j.energy.2014.01.025 , table A.2 .",