The characteristics of a grid able to integrate 100% of renewable generation
This spring, the state of California made it clear that renewable energies are not complementary elements in electrical systems. On May 8th, 100% of the electricity demand in the state was met with clean energy, mainly with photovoltaic technology, followed by wind.
California is leading the U.S. nation toward a clean energy future through incentives for renewable technology installation, clean energy grants, mandating programs, and solar communities. These factors play an important role, but What additional elements should the energy systems incorporate towards a fully renewable grid?
O. Probst, et al.  describes that an electrical system in the renewable energy era has to integrate a large-scale transmission grid, distribution generation, energy storage, reliable forecasting models, and smart grids.
The expansion planning of the transmission grid acquires a new dimension in the path to the energy transition. It is not just a matter of energy flow without congestion through the lines, but that of the deploy of transmission infrastructure with enough capacity, in those areas that have good renewable resources (which makes them suitable sites for the development of new clean energy projects).
Distribution generation, from a technical perspective, reduces the distances between generators and loads avoiding transmission and distribution losses, offering potential benefits to electric system planning and operations. But also, from a social-economic perspective, represents the opportunity to supply energy to isolated communities.
Energy storage provides flexibility to the grid allowing it to adapt before rapid changes in the generation/demand and transmission outages. The main applications of energy storage are the black start, spinning reserve, emergency backup, energy arbitrage, peak shaving, time shifting, load leveling, and power quality .
Renewable energy generation forecasting, which depends upon weather profile, helps to make sure that the grid will have adequate and appropriate size resources to meet the resilience and availability needs without oversizing the system .
The implementation of new electric power hardware, software, and design strategies enables multiple capabilities and functions in a smart grid, allowing it to have better control of its components, at greater resolution in both time and space. While the idea of smart grids did not have its origins in renewable energy, there are important implementations of smart technologies that can directly or indirectly enable more effective use and higher penetration levels of renewable energy in the electric grid, for example the implementation of Dynamic Line Rating, FACTS, HVDC, fast reactive power and voltage control, demand response management, and internet of things .
Being the energy generation sector the main contributor to greenhouse gases emissions, it is fundamental a true commitment that results in the implementation of initiatives that can shape greener and more sustainable electrical systems. From the integration of appropriate technologies to the right formulation of regulations, and the incorporation of strategies that allow the achievement of an energy transition.
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 O. Probst, S. Castellanos, and R. Palacios. Transforming the grid towards fully renewable energy.
 World Energy Council, Five steps to energy storage.
 A. Israr and Q. Yang, Resilient and sustainable microgeneration power supply for 5G mobile networks.