Balancing 100% Renewables
Updated: Aug 15, 2019
RE-AMP is a network of 160 member organizations with the goal of reducing economy wide CO2 emissions 80% by 2050 across eight Midwest states. Evolved has been working with RE-AMP for the last year to contextualize the physical changes needed to reach this goal, and I recently attended their annual meeting in Chicago to speak on the challenges of balancing very high levels of renewables in the electricity system.
The basic message from the presentation is that while there are no technical limitations to the amount of wind and solar that may be installed, in very high (>70%) renewable systems, the imbalance between renewable supply and electricity demand across seasons presents a substantial challenge. Using examples from the Eastern Interconnection, the presentation shows “straw-man” 100% renewable systems with different shares of wind and solar in order to convey the magnitude of balancing needs for each, which are significant.
The reality is that such very high renewable system systems are reliable and affordable only through the deployment of a combination of the following three solutions:
Low carbon dispatchable generation that will operate at relatively low capacity factors, for instance gas power plants running on a combination renewable gas and natural gas with carbon capture and sequestration.
Hydrogen electrolysis and power-to-gas (P2G) facilities operating flexibly in combination with a further buildout of renewables. Th benefit of this solution is twofold: (1) it provides low-carbon fuels and chemical feedstocks for industry and transportation; and (2) it can take advantage of the significant capacity of existing natural gas storage facilities.
Very long duration (>1500 hours) energy storage with near zero marginal cost for each new MWh energy stored. Examples would be underground thermal energy storage or very large hydro reservoirs.
Batteries and flexible load are two solutions that receive ample attention and have value in the medium term, but they are not up to the scale of the seasonal energy storage challenge presented by high levels of renewables. Batteries are orders of magnitude too expensive on an energy basis and flexible load does not have the ability to shift load for the duration that is needed.
For more information, download the presentation. Note: the presentation was updated on 11/17/2017 to correct a sign error in energy imbalance figures.