Grid Scale Renewable Energy Storage NOW
The cost per kilowatt hour produced by renewables is currently competitive with fossil fuels and these costs continue to fall. Storage, not cost, is the barrier for a full conversion to clean energy. Hydrogen is the ideal storage medium and round trip costs and efficiencies for electrolyzers and fuel cells are projected to improve over the next decade. Currently, however, the only practicable way to store extremely large amounts of hydrogen gas is in salt caverns, which have limitations; locations limited to specific geological areas, low withdrawal rate, low number of fill/discharge cycles/year, and large amounts of residual gas left in the caverns at all times.
A single 20-ft-dia x 2,000-ft-deep Solar Wind Storage underground chamber can be constructed at any location and can store 500 metric tons of hydrogen gas indefinitely at 5,000 psi. Based on fuel cells with a 40% efficiency rating, one filled chamber has the capacity to generate 8,000+ MWh of electricity, more than 2.5 times the average daily total output of a 550-MW Solar Farm.
The estimated construction cost for one 8.2 ft x 1250 ft Solar Wind Storage Chamber is $6.1 million. Based on an estimated annual operating and maintenance cost of $100,000 and a projected life of 50 years, this chamber will store 53,000 kg of hydrogen at 5,000 psi pressure which can provide 50 pct renewable power to 52,000 homes on a daily basis for only $0.014/kg storage cost.
Advantages of SWS Storage System:
-
The ideal storage system should have the ability to: 1) store renewable energy when there’s a surplus, 2) provide energy within seconds when there’s a demand, and 3) do both simultaneously if there is an overlap. This system can do all three.
-
PEM electrolyzers that produce hydrogen gas more efficiently at high pressures, can feed 5,000 psi hydrogen directly into the storage chamber, thus eliminating the need for mechanical compression.
-
A constant balanced gas pressure is maintained in the chamber and electrolyzer during the filling process by the SWS water-regulated patented system. This system forces all gas from the chamber, eliminates the need for residual gas to be left in the chamber and prevents contamination of an empty chamber.
-
The chambers can be lined with cylindrical hydrogen-resistant tubing, metal or composite materials, that are assembled on site and provide a leak-proof storage vessel within the chamber.
-
The surrounding ground provides a stress resistant boundary that is ideal for creating a storage chamber that can withstand pressures in excess of 10,000 psi.
-
The system provides ultra-long (indefinite) storage capability with no limit on the number or frequency of full recycling of the gas content.
-
The chambers can be constructed in 6 – 9 months at nearly any location, using common mining techniques such as blind bore shaft drilling or various other methods.
Large-scale, economical and efficient storage for renewables is currently the bottleneck in converting from a fossil fuel to a renewable energy-based economy. The SWS system uses existing technologies and equipment to provide a solution to this problem.