One thing that is holding back solar and wind power is the need for a substitute source of electrical power when solar and wind do not produce power. Solar does not produce power at night. Wind power is not generated when the wind is calm.
One solution is to use “Peaker” generating plants.
They supply the power needed to meet “peak” energy demand. An example of peak demand is when folks crank up their air conditioners in hot weather.
Solar and wind power can help take some of the peak demand for power only when they are actually generating electric power. This means when wind mills or solar panels are installed a matching amount of generating capacity, using traditional fuels, must be installed to be able to keep the system in balance.
Currently gas turbine engine generating plants are used to meet the demand for quick starting power generation. They can be go from zero to generating power in an hour or two. (Traditional fossil fuel fired steam turbine generating plants take a day or two to start up.) Gas turbine engines are somewhat like aircraft jet engines only much larger. They are usually burn natural gas or in some cases landfill gas.
A Better Alternative is to Store Surplus Electrical Power
Storing electrical power when there is surplus is like putting money in a saving account. Save it when you have a little extra so you can use it later when needed.
A large scale utility power system batteries are needed to store surplus power when solar and wind power are in full production. The power could then be used from the battery bank when demand exceeds the current supply.
We Need Better and Bigger Batteries
Some of the batteries being used and developed for power storage that are based on chemical reactions include:
- Traditional Lead Acid batteries
- Lithium ion batteries
- Zinc Hybrid batteries
- Flow batteries
Chemical batteries are successfully being used for keeping computer centers going during utility power failures. The batteries take the load just long enough to allow for startup diesel powered emergency generators.
Some large chemical battery systems are in use or under construction by utility companies. They are very expensive and require special handling due to the hazardous nature and value of the chemicals involved.
A mechanical power storage system that is used in some applications are flywheel machines. Energy is deposited making the flywheel rotate faster. Energy is withdrawn later resulting in slowing the fly wheel. The need for precision machinery limits the size of flywheels. Special magnetic bearings are needed to keep friction losses low. They are not currently practical for large utility size storage.
Another system that is in use to store energy uses compressed air. Air is compressed into large underground caverns or big storage tanks. The air pressure in storage increases as energy is added. When there is a demand for it electrical power can be made using stored compressed air running turbines to retrieve the energy.
The heat of compression results in lost energy unless additional equipment is installed to recover the heat energy. The compressed air tends to leak away and very large storage and mechanical equipment is needed.
95% of all U. S. Electrical Power Storage is Done Using Water
The only truly successful utility large scale “battery” systems that I know of in the U. S. of are pumped storage facilities. Consumers Energy has one in Michigan. They use surplus electrical power to pump water from Lake Michigan up to a reservoir. The reservoir is built into the top of a sand dune several hundred feet above Lake Michigan.
When there is a shortage of power Consumers Energy runs the water from the reservoir back into Lake Michigan through a water wheel that makes electrical power.
The switch over from pumping water up hill to making power by running water downhill can be done quickly when the demand changes.
The pump storage facility is surrounded with windmills that make power when the wind blows. This clean energy is used to pump fresh water up from the lake into the reservoir.
Pumped water storage systems work very well, but they are limited to locations where there is a large body of water such as a big lake or ocean. Also a favorable location is needed where an elevated reservoir exists or can be constructed. The electrical power storage capacity depends on the size of the reservoir and elevation above the water source.
An ocean water pumped storage facility is being built in Japan. It should work well but corrosion resistant materials are much more expensive. Plus the dissolved solids in the ocean water can cause problems. Using fresh water is better because it is not as corrosive as sea water.
We need more power storage capacity so that more electrical power from our wind and solar resources can be used effectively. Improvement of known technologies and invention of new energy storage methods are both needed.