The rapid decrease in the cost of solar modules is motivating significant increases in distributed solar generation from rooftops and solar farms. Since the electric grid was not designed to support large-scale decentralized, intermittent, and uncontrollable solar generation, there are strict caps set on the amount of solar energy that may connect to the grid. Unfortunately, due to rapid solar growth, users are now starting to hit these caps. In addition, setting strict caps is highly inefficient, and wastes much of the grid's potential to accept solar power. Instead, as in the Internet, all users should be able to freely connect solar modules to the grid and dynamically share its capacity to transmit solar power. The proposal includes hardware in the loop simulation activities that will demonstrate feasibility of the approach. To address the problem, this project will conduct fundamental research on the design of "smart" software-defined solar (SDS) systems that self-regulate the power they let "flow" into the grid. Similar to data transmission in the Internet, SDS systems dynamically regulate the solar energy that flows into the grid to maximize its available solar capacity, maintain a balanced supply and demand, and fairly share the available capacity among connected users. In particular, the project will develop new mechanisms for fairly controlling solar power flows, new protocols for rate-limiting solar flows into the grid, and new policies for leveraging batteries as energy buffers to regulate solar flows. To enable SDS, the project will design new mechanisms for fairly controlling solar output from inverters and charge controllers, new protocols for rate-limiting solar injection into the grid, and new policies for leveraging batteries as energy buffers to regulate solar output. Collectively, these mechanisms and policies will provide the technical foundation for a new class of "networking" protocols for solar energy.