The BIGGEST problem with clean energy

This video is wrong.  The first step towards reaching a zero emissions economy, is to reduce the CO2 production of the electricity infrastructure to 50% of it's current value.  This is readily achieved by solar panels alone, without the need to build even 1 kWh of battery or other form of energy storage.

Solar photovoltaic panels have gotten so cheap in recent times, that they produce the cheapest form of energy of all the mainstream existing technologies (the only potential exception being wood harvested on your own land using your own labor, where you value your time and risk of injury at $0/hour).  A properly implemented solar photovoltaic array can generate electricity at 2 cents / kWh, when the panels and support equipment is amortized over a 20 year or longer timescale (most solar panels come with a 20 or 25 year warrantee, and getting well over 20 years of practical service is realistic).

If you 3x overbuild your solar array size (such that you are wasting 2x of your base energy needs, on sunny days), the useful electricity it produces will be 3x as expensive, so around 6 cents / kWh, which is still cheaper than what the vast majority of electricity consumers pay today.  Consequently, it is economically sensible to 3x overbuild solar panels.  Doing so also provides highly reliable electricity, even on cloudy days, since on completely and continuously cloudy days (but without precipitation), solar panels generally still produce around 30% or more of their full sun day output values.

If we did 3x overbuild solar panels, we could nearly 100% shutdown all combustion power plants, during the daytime hours.  This would in effect reduce the CO2 production intensity of the electric grid to roughly 50% of the current values, since the combustion plants would only be operating during the nighttime hours of the day.

Once you have so many solar panels installed, there will be massive surpluses of electricity during sunny daytime conditions, since the system is 3x overbuilt to meet the normal daytime energy needs of society.  You can then use some of this "surplus" electricity for electric car charging purposes (assuming people go to the trouble of installing charging ports at places of employment).  The rest of the electricity can be put to valuable use as low priority industrial energy, for energy intensive activities, such as metals refining and reduction (ex: making iron from iron oxide for instance).  

Then, if people buy enough electric vehicles, and the electric vehicles are designed with high cycle life batteries in them (ex: lithium iron phosphate could be used, which often provides manufacturer claimed cycle life of 4000-20,000 cycles at 80% depth of discharge), the electric vehicles can be used to perform car to grid and grid to car storage operations.  High cycle life batteries are somewhat expensive on their own, but when you are buying them primarily for a high value use purpose (ex: as part of an electric car), they are very cost effective, and can serve a dual use purpose of storing vehicle propulsion energy, in addition to providing grid energy storage (some of which will be consumable during the nighttime hours of the day, using stored solar energy from the daytime hours).  Eventually, a zero emissions economy becomes realized, where long range, high cycle life, car to grid/grid to car capable electric vehicles are providing the majority of the necessary electricity grid energy storage for nighttime consumption.

Thus, there is no grid energy storage "problem" at present.  The current problem, is that society is not yet embracing solar photovoltaic panels fully.  They are good tech, but they are highly underutilized at present.  Simply building and hooking up far more of them, is the first step towards a zero emissions economy.  Energy storage technology is not the problem, as the current problem is one of human behavior, that is, most people just aren't doing the right actions to build the necessary solar panel manufacturing plants, and then running them at full capacity to build the necessary solar panels.