A main problem with solar energy have is the fundamental fact that once the sun goes down, solar energy cannot be produced. Therefore, the storage of energy created during the day must be integrated into the system to allow of usage during hours when the sun is not present.
There are a few methods of storing solar energy. These methods are divided into solar electricity storage and solar thermal storage. For solar electricity, rechargeable batteries are used to store the excess power generated by the system. A second common method of storing excess electricity is by converting the power into potential kinetic energy, through hydro-storage. Water is pumped into a system with the excess power and when electric power is needed, the water is let out, which generated electricity. Another method used is by directing the excess generated electricity back into the grid. This method used by solar systems, which are grid-tied, is called net metering. For solar thermal systems, the excess heat is stored in thermal mass or water systems, which then release the heat gradually during the night. All these methods, however, have a limiting amount of energy that can be stored at a reasonable cost. “Solar energy is an incredible resource, but one of its weak points is affordable storage options to be able to have a bank of power that can be used when demand is high but the sun is down”5.
In order for renewable energy to take over the job coal has kept in the U.S., providing 50% of the electricity production and 25% of total energy use, energy storage systems must be drastically improved so that it is cost-effective. “The goal of 50 percent of the U.S. power supply from solar and wind assumes that 100 to 150 gigawatts of energy storage, or roughly half the size of the country’s coal capacity, will emerge to provide power when the sun isn’t shining and the wind isn’t blowing”2. This statistic does not even consider the fact that some systems may also be offline and unable to generate power during peak times nor the future growth in energy consumption. Another problem that arises is that with the increase in solar production, more transmission lines will need to be added. In fact, according to one article, it will need to double in order to appease the demand.
New advances in the field of energy storage are needed in order for solar energy to take the place of coal. These advances allow for wider use of solar energy in the future. Currently in development is a steam engine, redesigned for cheap energy storage. These engines, called Terrajoules, “have a modular unit size of 300 kilowatts peak/125 kilowatts of typical output over the course of a day. Off-grid customers will need to use the system over 2,000 hours per year to get a strong financial payback”4. While the cost-effectiveness of solar systems increases with frequent advancements, the development of solar storage systems needs to pick up the pace to allow for solar to dominate in energy production, and pave the way for a cleaner future.