A Gentle Introduction to Grid-Scale Solar Energy and Storage Systems
Solar photovoltaics (PV), aka solar panels, are the fastest growing energy resource, and by 2030 will be the largest renewable energy resource, passing hydropower.
Generation of solar power at the grid-scale is estimated at 60 USD per MWh. That’s enough to power 813 US homes, suburban ones with a bunch of rooms, mind you, for a full hour. Compare that to the recent June 2025 heatwave in NYC, causing NYISO (the grid operator for New York) to jack wholesale prices for electricity on a stressed grid to $7,000 per MWh on Long Island.
Solar power is here, it is cheap, and it can supplant or even replace our fossil fuel reliance for grid-scale energy needs.
Even I’m solar powered. I consume food for energy, and that food either stores sunlight (solar energy) in its cells or consumes plants that do. Photovoltaics rely on a slightly different reaction than I do, but the sun is not something to be blind to when it comes to energy production and consumption.
There are several pain points with solar, however. The sun doesn’t shine 24 hours a day - despite the fact that we use energy 24 hours a day. This issue, intermittency, is one of the key obstacles to overcome in the adoption of solar power as part of the generation mix that supports our electrical grid. The fact that clouds, night, and dirt on solar panels can reduce their power output to nearly zero is not a problem that coal or gas power plants face, and can lead to grid instability, brownouts, and frequency fluctuation issues.
We can rely on the electrical grid because of the massive electrical inertia on the generation side, with thousands of interconnected spinning generators, and massive electrical drag on the demand side, with millions of people connecting and disconnecting power every day. With solar, a huge storm cloud passing over a key solar farm can take thousands of megawatts of capacity off the grid in a moments notice, leading to major issues with grid reliability.
So how can we introduce the inertia we need to bring solar to the top of our stack in energy generation? We look to energy storage systems, which provide a sort of artificial inertia. Instead of relying of physical inertia from spinning turbine blades, we can simulate a smoothing effect on the intermittency of solar power with battery systems that turn the on-off cycles of solar into a constant flow of power into the grid.
By placing a battery energy storage system (BESS) between solar generation and grid interconnection, we can store power during overgeneration throughout the day, and release that energy during the night, providing a more consistent and reliable source of energy.
This electrical virtual inertia comes at some cost, however. Batteries are not cheap (at ~$200,000 per MWh of storage capacity) and we encounter losses (as with any component we add to the system) on the order of ~10% for a round trip efficiency (RTE) of 90%.
There are other ways to smooth out the intermittency of solar. Adding to our engineering triumvirate, we raise thermal and mechanical to our electrical storage.
Electricity can easily be turned into heat (passing a current through any material with resistance will give you heat and/or a flame), which can be used to store electrical power. Thermal energy systems (TES) capture excess solar electricity, and turn it into heat to store in a thermal battery made of sand, carbon, or bricks. This thermal energy is most useful for direct heat applications like creating steam for use in factories or heating a large campus, since the conversion of heat back into electricity to power the grid is fairly inefficient.
We can also introduce physical (mechanical) inertia to our solar electrical systems to help smooth out the jagged edges of sun hitting the earth for our electrical grid. One common way to do this is with mechanical rotational inertia via flywheel energy systems (FES). These systems use some portion of electrical energy to spin induction motors so that a heavy cylindrical mass (thousands of kilograms) is spun to high RPMs. When kept in a vacuum, these flywheels can store a significant portion of energy for minutes or hours, losing only a small percentage of its speed each day. The spinning drums can be bled off to power the grid during the night to make use of excess energy, or they can be activated during grid stress events as a rapid supplement to power generation.
Over a longer-duration period, other methods of mechanical energy storage can be used. The most common, by far, in the US is pumped hydro store (PHS). Energy is used to pump water up a mountain into a dam, so that it can be released on demand to spin a turbine and generate electricity. These occupy vast stretches of space, have a comparatively low cost and energy density, but are infinitely rechargeable, unlike lithium ion batteries. We are also running out of convenient places to put these grid-sized and grid-scaled storage systems. Other ideas to store excess electrical energy include using cranes and winches to hoist huge blocks of concrete high into the sky, and allow the downward descent and release of this potential energy to feed the grid, but these have yet to be proven on an economic battleground.
Check back in soon for more information about the grid and how it works, alternatives for energy storage systems, and how renewable energy plays into my big ideas for cooling our overheated world.