Today, messages about energy are mostly negative ones. We are focusing on ways to use less energy, even though life in the 21st century requires increasing consumption of energy, not only for the third world, but for the first world.
According to the US Department of Energy, the solar energy resource from a 100-mile-square area of Nevada could supply the United States with all its electricity (about 800 gigawatts) using modestly efficient (10%) commercial PV modules (see DOE report here). With sufficient energy storage, solar energy could produce 100% of the energy needs of the world. Rather than restricting energy usage in the name of environmental protection, a solar powered grid would make abundant energy available for new applications and benefits. Abundant energy can also be a solution to the problem of fresh water supply, food production, liquid fuel synthesis, etc.
Many initiatives for resolving energy issues involve conservation of energy or energy efficiency. For example, smart grid and demand-response are both focusing on better utilization of energy. However, as the following chart shows, the growth in energy supply is mirroring global population growth. While efficiency improvements are helpful, they do not address the core issue that energy demand will not slow before population growth stops.
Global warming is generally accepted as a catastrophic problem for the world. We make the argument that renewable energy is abundant, and has the potential to completely replace the use of fossil fuels. This transition requires both energy storage as well as the Digital Grid.
According to the DOE, a solar PV plant 100 miles square in the Southwest would generate 100% of the electricity used by the entire US today. Such a solar plant would not need to be located in only a single place, of course. This is only to illustrate the scale of solar energy which would address our energy needs.
In order to make use of solar energy for substantial proportions of our energy needs, storage will be necessary.
Renewables such as solar and wind, are sufficient in total average energy supply, however, due to weather conditions and diurnal variation, the supply of energy at any given instant will not meet the required energy demand. For this reason, energy storage will be required if renewable energy is to provide a large proportion of our daily demand of energy.
Energy storage is available through a variety of technologies today. The most widely used technology for bulk energy storage is pumped hydroelectric power. Many hydroelectric power plants have reservoirs below the power source, which are able to use excess energy from the grid to pump water back up to the upper reservoir. Typically, water is pumped up at night, when demand is low, and then flows back down to generate during peak energy demand hours during the day.
Compressed air is another type of energy storage, where air is compressed and stored either in tanks above ground or in unused caverns underground.
Large solar power plants are often thermal plants, which use giant movable mirrors to concentrate the energy from the sun to heat a fluid which is then used to drive steam turbines to generate electricity. These thermal solar plants are currently being built with large tanks to store the heated fluid, enabling the generation of electricity during the evening hours after the sun goes down.
Finally, there is battery technology, which is seeing both technology improvements and cost reductions driven by the growth of the electric vehicle industry.
We believe that through the mass deployment of all of these types of energy storage, the costs will drop dramatically.
The chart at the left, which is logarithmic on both axes, shows the drops in prices delivered by the photovoltaic module industry. As production rose, pricing dropped, showing a reduction of 100:1 over the 30 years from 1976.
We believe that energy storage will illustrate a similar drop in pricing as production expands up to gigawatt scales.
We would like to emphasize, however, that energy storage is not strictly required for the digital grid. Many of the benefits of the digital grid can be obtained without energy storage. Storage is necessary for 100% renewable generation of electricity, and the Digital Grid is the solution to managing the grid which has achieved penetration of from 30% to 100% renewables.