Why Renewables Cost More (some basics for short attention spans)

“Power plants, usually natural gas, must be kept in spinning reserve, ready to come online when the wind stops blowing or the sun stops shining. There is the cost of natural gas to keep these units operating off-line, as well as maintenance costs from the added wear and tear on these units.”

“The strongest winds, which are the best for generating electricity, are found hundreds, if not a thousand or more miles away from where the electricity is used. Fossil-fuel] power plants are located closer to where the electricity is used.”

“Coal-fired and NGCC power plants were built to operate as baseload plants operating continuously. Cycling results in an increase in the number of cold-starts and shutdowns.”

The renewable-energy lobby has the advantage of many citizens having short attention spans and not being experts in the field. Thus the notion of a free energy input (wind) seems appealing–clean and green and cheap.

But this impression is opposite from the truth in many ways. Cost-wise, it is fallacious.

Aside from the fact that the levelized cost of electricity (LCOE) is higher for wind and solar, there are many other operating costs that result in wind and solar being far more expensive than coal or natural gas for generating electricity.

Back-up

This is a well-documented cost, where power plants, usually natural gas, must be kept in spinning reserve, ready to come online when the wind stops blowing or the sun stops shining. Wind and solar are unreliable, and must have back-up power ready to go on-line at a moment’s notice. First, there is the cost of natural gas to keep these units operating off-line, but secondly, there are the additional maintenance costs from the added wear and tear on these units.

Storage

Storage is required to minimize the effect of rapid ramping up of fossil fuel power plants when the sun sets, or as an alternative to keeping natural gas power plants in spinning reserve. The CAISO Duck curve illustrates what happens when the sun sets, and fossil fuel power plants must be rapidly brought on-line to meet demand. Storage could theoretically provide some of the power needed when the sun sets.

The cost of storage varies, but at a minimum is around $2,000 per KW, about the same as the cost of a new natural gas combined cycle power plant. A recent trial by Pacific Gas & Electric resulted in storage costs that were more than twice as large.

The CAISO Duck Curve illustrates the sudden ramping as renewables increase.

Transmission lines

The strongest winds, which are the best for generating electricity, are found hundreds, if not a thousand or more miles away from where the electricity is used. This requires building expensive transmission lines. While it’s true, new coal-fired or natural gas combined cycle (NGCC) power plants may also need new transmission lines, these power plants are located closer to where the electricity is used.

The Joint Coordinated System Plan determined it would cost an additional $200 billion to build the transmission lines needed if only half the nation used wind energy, where wind supplied only 20% of the power.

More recent is the Pathfinder wind energy project that requires a $3 billion investment in transmission lines (see, Absurd Cost of California Wind).

Cycling

Coal-fired and NGCC power plants were built to operate as baseload plants operating continuously.

Because wind and solar operate intermittently, it’s necessary for these baseload plants to cycle up and down, following the constantly changing output from wind and solar plants. Cycling also results in an increase in the number of cold-starts and shutdowns.

Cycling puts an added strain on boilers, turbines and many other components of the transmission and distribution system. Thermal expansion and contraction is the main culprit. Different materials have different coefficients of expansion, so boiler tubing may expand more rapidly than the firewalls and other materials surrounding the tubing.

Ramping up when the sun sets, as described above, also causes this type of damage.

This damage increases maintenance costs. Utilities, such as Duke Power, are installing new monitoring equipment and attempting to develop new operating methods in an effort to minimize the damaging effects of transient temperatures.

Industry trade publications, such as Power Magazine and Turbomachinery International, are recognizing the damaging and costly effects of cycling.

Summary

All of these are operating costs that are borne by the utility and eventually paid for by customers.

They don’t include the social costs when there is a blackout, such as occurred in South Australia due to the unreliability of wind and solar. And not included is the environmental problem of energy sprawl from dilute in place of dense energy, explained elsewhere.