written 6 Mar 2022
published 13 Mar 2022
Two of the challenges threatening the foundation of our civilization are climate change and diminishing energy resources. To preserve a habitable planet, we must reduce atmospheric carbon emissions 50 percent by 2030. In addition, global oil production peaked in 2018, so demand must decrease faster than declining production to keep oil affordable. The solution to both is a shift from consuming limited, polluting, energy resources to collecting and storing renewable ones. Assuming humanity has the political and economic will to respond, what does this significant infrastructure shift require?
The present average electricity consumption in Mendocino county is 1400MWhr/day (megawatt hours per day), ranging one third higher in the summer. Of this, Sonoma Clean Power (SCP) supplies 2/3, Ukiah Municipal supplies 1/5, and PG&E supplies 1/7. The carbon free portion averages to 83 percent. In California, electricity production is 1/5 of our energy use, with transportation consuming 2/5, and heating and manufacturing the other 2/5. Since most of the electricity in our county is already carbon free, further emission cuts will have to come from the 4/5 of the energy economy which is still fossil fuel powered. Increasing energy efficiency to reduce what is needed is critical, but the electrical industry will still have to double, or even triple, their current production to hit the 2030 target.
SCP is investigating expanding production from the Geyser fields in Sonoma and Lake counties, using new geothermal technology which radically reduces water usage and allows greater portions of the heat field to become productive. Humboldt Bay is developing large offshore wind capacity combined with onshore storage. Both these projects will generate significant non-carbon baseload power, but will take time to accomplish and require extensive grid upgrades to get that power to market. Complicating matters, the current grid is already close to maximum capacity, and will need massive investment and time to functionally increase carrying capacity.
An alternative, which avoids most grid capacity issues, is extensive construction of distributed renewable power systems. In Mendocino county this would be primarily solar with storage. If we assume an annual average of 4 watthours production per watt of installed array, producing another 1400MWhr/day would require 350MW (megawatts) of array. That means adding 44MW a year, for 8 years, within Mendocino county. Each megawatt array requires an average of 4 acres, requiring 176 acres per year. But land dedicated to power production is not lost to other uses. Roof tops and parking lot canopies can be used in urban areas, and many kinds of agricultural uses thrive in the shade under arrays.
Solar production peaks around noon, but loads are spread throughout the day, so each array requires storage to help support the load while reducing stress on the grid. Every array should have storage 4 times the array capacity, distributing the daily output over time. This local storage allows using the grid to preposition baseload power produced during the night, while the grid load is at a minimum. These distributed systems can be configured to stand alone as a microgrid, increasing local power resilience during natural disasters.
Batteries are good for storing day time solar power for night time use, but not for storing summer sun for winter consumption, but the power peaks of summer could be locally converted to hydrogen. This emerging technology resolves several important limitations of renewable energy: long term energy storage, direct application for heating and industry, shipping and aircraft fuels, and quick refueling times for long haul freight.
The two biggest challenges for wide spread hydrogen use today are increasing water electrolyzer efficiencies to produce the hydrogen and storing the result. Hydrogen can be stored as a compressed gas, a cooled liquid, or converted to an organic liquid like ammonia or methanol. The hydrogen can be reconverted to electricity through a fuel cell, or used as a combustion fuel. Local hydrogen production would be a dispatchable load, aiding grid management, and would help the shift from propane or natural gas heating. Buildings are already being heated by burning hydrogen, and pilot plants using hydrogen in the production of steel and cement, two of the most energy intensive industries, are already operating. Toyota, Mercedes, and Cummings are working on hydrogen fueled versions of their products.
This describes the scope of the production and storage requirements for a habitable future.
