This is the fifth of 6 parts of a discussion of SoCalEd’s plan to decarbonize California by 2045. This fourth ‘building block’ in SoCalEd’s Roadmap 2045 is a move to low carbon fuels.
The details below this graphic explain it better:
–50% reduction in natural gas consumption
–40% of rest is biomethane or hydrogen
–20% of heavy trucks are powered by hydrogen
Lets tackle those three ‘low carbon fuel’ points in reverse order.
Heavy delivery hydrogen powered trucks
20% of heavy trucks powered by hydrogen is technical nonsense contrary to SoCalEd’s own point two. See my essay Hydrogen Hype in ebook Blowing Smoke for details of hydrogen’s many problems.
In sum, hydrogen is very difficult to store, and is only an energy intermediary (because it is made from water or methane, as any free hydrogen escaped the atmosphere billions of years ago).
Most commercial hydrogen is produced by steam reformation of methane. On net energy grounds we are better off from a CO2 perspective ‘burning’ natural gas rather than converting it to hydrogen.
Hydrogen from water electrolysis has a theoretical efficiency of 88%, but practical efficiency is about 75%. Four percent of commercial hydrogen is produced by electrolysis today. Using electricity from renewables to produce hydrogen and then using the hydrogen in fuel cells at about 60% efficiency is theoretically possible for electrified heavy trucks, but the net useful energy is only (0.75*0.6) 45% of the starting renewable electricity.
The BIG (pun intended) problem with hydrogen powered heavy trucks is its fuel cell. The big physical difficulty is size and weight, never mind cost. A typical class 8 OTR ’18 wheeler’ truck tractor is about 600Hp (needed to get over the Rockies and Appalachians), or about 450 Kw. A Ballard 100Kw PEM fuel cell for city buses (SOFC cannot be thermally cycled on/off because of heat stress cracking) has the rough dimensions 1.2m x 0.9m x 0.5m and weighs 285Kg. Its cooling system is 0.7m x 0.5m x 0.4m and weighs 44Kg. Ballard’s 60Kw PEM is 1.1m x 0.9m x 0.5m. A class 8 tractor would need four 100Kw plus one 60Kw PEMs. Ignoring cooling, that is a minimum fuel cell space requirement of 5.9m x 4.5m x 2.5m! Is all cell, no truck—doesn’t fit. And the thing would also weigh at least 1.4 metric tons
Lest this seem a bit unfair to SoCalEd’s vision, perhaps they meant the typical integrated class 7 ‘box van’ delivery truck, usually a cab over diesel design at about 250Hp, or about 185Kw. Two of the Ballard 100kw PEMs would suffice. Minimum space required (again ignoring cooling) is ‘only’ 2.4m x 1.8m x 1m. Still doesn’t fit.
In sum hydrogen powered trucks are apparently not possible.
40% of natural gas is replaced by biomethane or hydrogen
This second part has two separate claims.
The hydrogen claim was already refuted above. Replacing natural gas with hydrogen from steam reformation makes the CO2 ‘problem’ worse. Replacing natural gas with renewable electrolysis hydrogen wastes 25% of the electricity; we are better off without conversion.
That leaves biomethane.
Methanogen bacteria ingest hydrocarbons and excrete methane. True in ruminant stomachs and in landfills. So the basic SoCalEd question becomes how to usefully capture meaningful quantities of biomethane? Obviously not from cow farts.
There are hundreds of landfill methane extraction facilities that use the methane from garbage decomposition to produce electricity using spark ignited diesel engines. There is a large one near my Chicagoland townhome, located along Willow Road west of the Lake. Google Earth will take you there. The top of the big old landfill is now Willow Hill Golf Course. Methane collection wells dot the sloped sides; two Caterpillar spark ignited diesel generators are housed in the structure at the entrance off Willow Road.
But biomethane from garbage and sewage decomposition is limited in quantity both by source material and by production time perspectives, as digestion is a fairly slow process. It is possible to range the supply magnitude problem. SoCalGas is the largest natural gas utility in California. It has 20.9 million customers. Seventy percent on 40% biomethane is ‘only’ 5.85 million customers supplied with biomethane. Nope.
50% reduction in building natural gas consumption
Utility natural gas is mostly for CCGT. SoCalEd likes lots of renewables, but will need natural gas for backup generation. With enough renewables and backup this aspiration might be possible.
Residential natural gas is mostly for heating and hot water. Those functions could be electrified, but at great cost to the building owners and no cost to SoCalEd, same problem as with electrified vehicles (see previous parts 3 and 4). The grid would have an even larger ‘decarbonized electricity’ set of virtually insurmountable renewables problems.
So even though the low carbon fuels figure is big, pretty and green, it is comprised of newly found elements from SoCal’s periodic table: impossibilium and hopium.