Upside down Sustainable Energy or Why Fracking May Support Renewables - a remark -

  reprint (by W. Scharnhorst) Hydraulic fracturing, or fracking, is shunned by the environmentalists that laud renewable energy sources. However, by not supporting both initiatives, they may be working at cross purposes. Natural gas, booming largely because of fracking, complements renewable energies on the grid. The two seemingly opposite technologies are, for the moment, inextricably linked. Renewable energies like solar and wind produce most of their output at times of the day when not that many people need it. Peak demand for electricity is usually in the morning and evening. Solar production is highest during the middle of the day and afternoon, and wind reaches its highest production at night.

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Because there is no large-scale economical way to store that energy and reconcile the misaligned supply and demand, most of our peak demand must still rely on non-renewable fuel sources. Electricity outputs from burning different fossil fuels also have different characteristics. Output from coal-fired plants is particularly inefficient to ramp up and down to meet changes in demand. However, natural gas-fired plants can quickly meet those hourly variations. Some natural gas can even ramp up or down at a moment’s notice to meet minute-to-minute fluctuations During most of the year in Northern states, energy consumption peaks first in the morning as we all take showers and get ready for the day, then levels out during the midday. It peaks again more dramatically in the evening hours as we flip on computers, televisions, ovens, microwaves and water-heaters. Demand finally drops down to base load, or minimum demand, at night. Some states use Demand Response programs to smooth out demand by making electricity cheaper on off-peak hours, thereby disincentivizing peak use. However, even the best program can’t eliminate all variability in power demand. Base load in most parts of the United States is still provided by coal plants or nuclear plants. Because both are slow and inefficient to ramp up — though very efficient once at full capacity — they have contractual minimum run times that can last several days. In contrast, large, efficient combined-cycle natural gas plants, which can often be ramped up in half an hour, are used to accommodate these relatively predictable hourly changes. More renewables, however, lowers the predictability of the total energy supply. The wholesale price of electricity is measured by marginal cost, with the cheapest going on line first. Because renewables are essentially free to switch on, they’re the lowest part of the order, or supply stack, and are automatically connected to the grid. The minute-to-minute variations in solar and wind output from cloud cover or interrupted winds adds another layer of variability to the inescapable daily variation in renewable output. That variation within daily variability is met by either gas- or oil- fired peaking units, named for their ability to meet fluctuations in peak demand quickly. While gas-fired peaking units are less efficient than their large combined-cycle counterparts, most of them are capable of ramping up to full output within just a few minutes to offset either an unexpected or expected fall in renewable production. Large natural gas combined-cycle units are ostensibly cleaner than coal plants and the same is true of gas-fired peaking units versus their oil counterparts. When all options were available, hydroelectricity is actually the perfect way of compensating for variation in renewable production. Hydro power ramps up nearly instantaneously, emits few greenhouse gases, if any, and has almost no marginal cost, which determines electric wholesale prices. However, it is limited both to specific locations and in total quantity. Only 6 percent of American electricity is generated by hydropower, and most of it is consumed within state lines. Continue... // empowered by scharnhorst-csa.blogspot.com).

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