What are the limitations of wind and solar photovoltaic cells?

Wind energy is developing very fast, which is based on a lot of subsidies. Solar power is small but growing faster, which is also based on high subsidies. 

 

To be fair, government spending on research and development and various incentives have played a big role. Unfortunately, solar pv still does not have economic benefits, but the biggest problem is intermittent. We need round-the-clock energy supply. 

 

Apart from hydropower (which is a pity), the main carbon-free new energy sources are intermittent. 

 

Nuclear power is carbon-free, but it has high costs, security issues, and nuclear waste, and plutonium is not used to make weapons. 

 

I think the biggest problem with two major new sources of energy, wind and solar, is storage. Ironically, Germany has installed a lot of rooftop solar power, but in the summer, coal-fired power plants are still under construction and the electricity price is negative during the day because they pay for electricity. At night, coal is the only energy source, and because energy companies have to recoup their costs, they either raise the price of electricity, because they don‘t make any money during the day, or they just go bankrupt. 

 

Many people study energy storage, the battery is a form of storage, and there are other forms, such as compressed air and liquid metals. But we have no idea if we can make energy storage as efficient as the grid. We are still very far from economies of scale.