The report.

From the Summary:

Figure 1 summarizes the main results of the analysis. A future energy scenario emitting 85% less CO₂ emissions than 1990 levels is compared with a reference scenario, which assumes that the German energy system operates in 2050 the same way as it does today. Results show that ii) the primary energy in the minus 85-percent scenario will drop 42 % below today’s values by 2050. iii) Assuming that no penalty is imposed on CO₂ emissions and the price of fossil energy remains constant, calculations show that the cumulative total costs to maintain and operate today’s energy system will be 27% less than transforming the energy system to the targeted minus 85 percent scenario. iv) On the other hand, if the penalty for CO₂ emissions increases to €100/ton by 2030 and thereafter remains constant and given that fossil fuel prices increase annually by 2 percent, then the total cumulative costs of today’s energy system (Reference) are 8% higher than the costs required for the minus 85 percent scenario up to 2050.

From the report, regarding electrical energy storage:

Electrical energy storage systems in the form of stationary and mobile (in vehicles) batteries or pumped-storage power plants are used as storage systems. Hydrogen storage systems and thermal hot water storage systems in different orders of magnitudes are considered in addition.
With respect to methane storage system, the simplified assumption is made that currently already existing storage capacities (including grid, approx. 210 TWh [9]) will also be available to the system in the future. Thus, they are not considered in the optimisation.

Pumped storage plants are not included in the optimisation. Bases on current values of an installed power of approx. 6.3 GW, and storage capacity of approx. 40 GWh, [26, 27] an increase to 8.6 GW and/or 70 GWh is assumed until 2050 for the dimensions of these plants (power and electric storage capacity) (own assumptions based on [28]).

(Note in above no change in the amount of pumped storage.)

That’s it. Feasible. Germany.

Related U.S. references:

• Planning the Distributed Energy Future (Black & Veatch and SEPA
• The Utility of the Future, MIT Energy Initiative, 2016
• Distributed energy resources: Required reading for a modern grid
• Distributed Wind Energy Association

And, quoting from the MIT report above:

The present trend toward widespread availability and decreasing cost of distributed generation and storage results in the possibility of grid defection—that is, complete disconnection from the grid.44 Grid defection may be motivated by physical conditions such as the ability to install some embedded generation within a residence or business, and economic considerations such as the desire to avoid network costs. Grid defection represents an extreme form of price elasticity and must be considered—from an efficiency perspective—in tariff design and in decisions about which regulated costs are to be included in electricity tariffs.

Pumped hydro energy storage and molten salt thermal storage account for the vast majority of installed energy storage capacity to date, but these technologies are poorly suited to distributed applications (DOE 2015).

Now, I’m done. I have real work to do.