Getting to 100 Percent

[Admin]

Kevin Cameron has been writing about motorcycles for nearly 50 years, first for <em>Cycle magazine</em> and, since 1992, for <em>Cycle World</em>. (Robert Martin/)

It looks easy enough: If we just keep building more and more wind and solar generating capacity while retiring our conventional electricity-generating plants, eventually we’ll reach 100 percent renewables.

Because wind and solar outputs vary, our national electricity grid would need ways to compensate for loss of solar at sundown, as well as wind variations from dead calm to gale force. During 2020, 60 percent of US electric power came from combustion and 20 percent from nuclear, with wind supplying 8.4 percent and solar 2.3 percent; the balance came from hydroelectric at 7.3 percent and geothermal with 0.4 percent.

The Existing Power Model

Traditionally, grid power has been supplied by limited numbers of large power stations. Existing coal-fired plants are in the range of 750 megawatts (MW), large nuclear plants at 1,750 MW, and combined-cycle natural-gas-fired turbines at 550 MW. None of these sources can be switched on or off at short notice, and reducing their output below “nameplate power” involves loss of efficiency.

Wind and solar installations are typically much smaller; 95 MW from a cluster of 20–30 large wind turbines and 10 MW for a substantial solar-panel installation. Because the energy-gathering ability of these sources depends upon area, they require large chunks of land.

At present, when it comes to a fast-starting power source with the agility to compensate for variations in available wind and solar energy, the answer is the simple-cycle gas turbine, fired by natural gas. Such machines began life as “topping units” which supplied extra power beyond base load to drive summer air conditioning.

For the moment this means that for every 100 MW of wind or solar power we build we also need an equal amount of stand-by power to take its place at night or in times of low wind velocity. Taken to extremes, this implies keeping two power systems available: one carbon-free renewable wind and solar, plus a second with enough combustion-generated standby power to maintain system output.

Power Storage and Transmission

Two alternatives have been proposed for the future:

1. Long-distance power transfer from areas that have an excess to areas that haven’t enough.
2. Building extra wind and solar capacity and storing the excess energy for use wherever needed.

On the first point, it is certainly possible to use high-voltage transmission lines to move power over long distances. As an example, at present Australia plans to generate 10,000 MW of solar power on 58 square miles of solar panels and transmit it 2,600 miles undersea to Singapore by high-voltage DC cables; the Australian city of Darwin will also receive some of this power. Proposed opening is in 2027, and it would make this project the largest solar-generation and battery-storage system in existence. Projected cost is $22 billion USD. This is expected to provide 15 to 20 percent of Singapore’s electric power demand, and a funding agreement is expected in 2023.

An interesting study by ScottMadden Management Consultants entitled “Transmission in the US: What Makes Developing Electric Transmission so Hard?” explores what would be involved in converting the US electric grid from its present form, which is based upon synchronizing the outputs of relatively few quite large conventional generating stations, to a more distributed network capable of maintaining the stability of a much larger number of smaller electricity producers with varying outputs.

The more distributed system of the future is expected to require doubling the existing 180,000 miles of HV transmission lines. At present the cost per mile of overhead high voltage transmission line is roughly $300,000, but underground transmission multiplies that roughly times 10.

To underscore the financial importance of electricity distribution cost, the report says that a typical consumer’s electric bill now includes:

Cost of electricity generation 56 percent

Cost of electricity transmission 13 percent

Cost of distribution to consumers 30 percent

Electricity transmission in the US is subject to a combination of federal, state, and local lawmaking. Acquiring permits and rights-of-way for expansion of the US power grid could therefore be a complex process. Funding is up to investors. We live under free-market capitalism, which may differ from an economy planned by environmentalists.

Battery Storage

What about large-scale battery storage? It most certainly is coming. Vistra Corporation has built a 300-megawatt-hour (MWh) capacity storage battery at Moss Landing in Monterey Bay, California. It began operation in December 2020. The energy stored is sufficient to supply the average power consumption of the City of Los Angeles for seven minutes, or to power the nation for two and a half seconds. Bear in mind that even such limited storage facilities are valuable in their ability to rapidly smooth out fluctuations in grid power. Another 100 MWh of storage is coming soon, and there is said to be space for a total of 1,500 MWh battery capacity on the Moss Landing site.

There’s a lot to be done. We live in interesting times.

View the full article

[fullscreenaging]

Something interesting for a change. 

[fastbob]

Kin' 'ell ! What's happened to Kev's head ? Is his giant brain trying to escape ? 

[bonio]

3 hours ago, fullscreenaging said:

Something interesting for a change. 

First one I've read and got as far as the second paragraph

[Bender]

1 hour ago, bonio said:

First one I've read and got as far as the second paragraph

First to read had to give us the short version  

[fullscreenaging]

3 hours ago, bonio said:

First one I've read and got as far as the second paragraph

I didn’t suddenly develop a migraine after the first two sentences, so I carried on.