Inherent unreliable renewables dictate GND “100% renewable electricity” mandate yields unavoidable GHG emissions

by Larry Hamlin | May 31, 2019

The Green New Deal (GND) and California’s SB 100 are both draconian and completely unrealistic pipe dreams that politically mandate “100% renewable electricity” for the U.S. and California respectively.

A new 117 page study from the American Enterprise Institute (AEI) has determined that these politically contrived schemes of “100% renewable energy” are self defeating because of the inherent unreliability of renewables which results in significant GHG emissions occurring from the unavoidable need for backup dispatchable and reliable fossil generation. This backup fossil generation is required to provide grid stability functions including frequency, voltage and synchronization control, daily system load ramping and to prevent power shortages and blackouts.


The AEI study evaluated the GND proposed scheme presented to Congress and concluded that any attempt to mandate “100% renewable electricity” that could achieve the necessary outcome of preserving electric system grid stability and reliability requires that backup fossil generation be operating to deal with the inherent and unavoidable unreliability of renewables thus yielding the result that significant GHG emissions cannot be avoided.

The AEI study found that the amount of fossil backup generation required for a 100% GND renewable generation scenario for the U.S. would result in GHG emissions the equivalent of 35% of the emissions levels that occurred from all U.S. power generation in the year 2017.

Accordingly unless the U.S. is willing to abandon electric grid system stability and reliability and knowingly accept that significant periods of unreliable electric grid stability along with power shortages and blackouts will occur throughout the U.S. there is no choice but to acknowledge that GHG emissions cannot be avoided with a 100% renewable generation political mandate.

This same outcome occurs at the state level as well where the 100% renewable generation electric grid stability and reliability failings must be addressed either through importing backup fossil generation via transmission links, operating through the use of in-state backup fossil generation or a combination of both these backup fossil generation options.

The AEI study summary concludes the following regarding the impracticality of trying to operate a reliable and stable 100% renewable energy system:

“Because of the need for conventional backup generation to avoid blackouts in a “100 percent renewable system” and because those backup units would have to be cycled up and down depending on wind and sunlight conditions, one ironic effect would be GHG emissions from natural gas–fired backup generation 22 percent higher than those resulting in 2017 from all natural gas–fired power generation. And those backup emissions would be over 35 percent of the emissions from all power generation in 2017.

Without fossil-fired backup generation, the national and regional electricity systems would be characterized by a significant decline in service reliability — that is, a large increase in the frequency and duration of blackouts. Battery backup technology cannot solve this problem. It is unlikely that a power system characterized by regular, widespread service interruptions would be acceptable to a large majority of Americans. Accordingly, the emissions effects of backup generation as just described in fact would be observed, which is to say that to a significant degree the GND is self-defeating in its asserted climate goals. That is another reason to conclude that the true goals are an expansion of wealth transfers to favored interests and the power of government to command and allocate resources. Moreover, the reduction in individual and aggregate incomes attendant upon the GND policies would yield a reduction in the collective political willingness to invest in environmental protection over time.”

The GND proposal scheme articulates among its fanciful provisions the following regarding 100% renewable electricity:

And “it is the duty of the Federal Government to create a Green New Deal,” the goals of which “should be accomplished through a 10-year national mobilization . . . that will require the following goals and projects—”

• “Eliminating pollution and greenhouse gas emissions as much as technologically feasible”;

• “Meeting100 percent of the power demand in the United States through clean, renewable, and zero-emission energy sources . . . by dramatically expanding and upgrading renewable power sources”;

The AEI GND report provides the following assessment of the significant and intractable problems facing any attempt to implement a stable and reliable 100% renewable electricity system:

“It is technically impossible for a 100 percent renewable power system, as defined in the GND, or anything approximating it to avoid both frequent service interruptions (“blackouts”) and a far smaller decline than commonly assumed in emissions of conventional pollutants and GHG. In other words, service interruptions are a crucial problem under a 100 percent renewable power system, a problem that can be addressed only with conventional backup capacity. This observation requires a brief primer on the operation of an electric power system.

Electric energy in large amounts cannot be stored at low cost in batteries due to technological limitations; only indirect storage in the form of water in dams is economic. (The problems with battery storage are discussed in Chapter 4.) This reality means that the production and consumption of electricity in a given power network must be balanced constantly to prevent blackouts and more generally to preserve the expected reliability of the system.

Because unexpected surges in demand and/or outages of generating equipment can occur, backup generation capacity must be maintained; such backup capacity is termed the “operating reserve” for the given network. This operating reserve is of two types; the first is the “spinning reserve”—that is, generators already connected to the network, the output of which can be increased by raising the torque applied to the generating turbines. The typical system requirement is that spinning reserves be 50 percent or more of total operating reserves. The second component of operating reserves is the supplemental reserve, which comprises generation capacity that can be brought on line within five to 10 minutes and/or electric power that can be obtained quickly from other networks or by withholding power being distributed to other networks. Additional reserve capacity often is provided by generators that require up to an hour to come on line; this backup capacity is not included in measures of the operating reserve for a system because of the length of time required for availability.

Electric supply systems respond to growing demands (“load”) over the course of a day (or year) by increasing output from the lowest-cost generating units first and then calling on successively more expensive units as electric loads grow toward the daily (or seasonal) peak. (“Baseload” units run more or less constantly except for scheduled and unscheduled downtime.) Electric generation capacity fueled by renewable energy sources is not “dispatchable”; that is, it is not available on demand because wind and sunlight are intermittent. In other words, system planning and optimization cannot be based on an assumption that it will be available to provide power to the grid when it is expected to be most economic. Accordingly, it cannot be scheduled: It requires backup generation capacity to preserve system reliability.

Several studies have concluded that wind capacity does not impose large reliability costs on a given power system as long as the wind generation remains about 10–20 percent or less of system out- put, because the intermittent nature of wind resources given a small market share has effects similar to those of unexpected outages and other familiar problems characterizing conventional generation.51 At the same time, outages of wind capacity due to weak wind conditions are much more likely to be correlated geographically than is the case for outages of conventional plants, for the obvious reason that weak winds in part of a given region are likely to be observed in tandem with weak winds in other parts of that region. Because appropriate sites for utility-scale solar facilities (and rooftop photovoltaic systems) are concentrated geographically, the same correlation problem is likely to affect solar electric generation as well.

The problem of frequency regulation and grid stability—related to but distinct from the intermittency problem—created by a large expansion of non-dispatchable power generation is well-known.52 In brief, most US generating capacity is alternating current (AC) and must be synchronized at 60 hertz. Because generation from wind and solar units cannot be ramped up and down in response to disequilibria in power frequencies in a grid, conventional units must be used to regulate those frequencies. Without such frequency regulation, the grid can become unstable, in the sense that the generators comprising the grid would be spinning at different speeds, a condition of nonsynchronous generation that can cause a power outage. In a critique of a proposal53 for a 100 percent renewable power grid, Christopher Clack et al. make the following central observation.

An important gap in the analysis of [Jacobson et al.] is that it does not provide evidence that the proposed [100 percent renewable] system can maintain sufficient frequency regulation to preserve power system stability. The designers of power markets have known for decades that there is a need for improved markets that reward ancillary services that contribute to grid stability.

Further, [Jacobson et al.] state that [their] model “assumes a fully interconnected grid” that does not include any transmission constraints. [They] simply assume that there is unlimited transmission availability and that if “congestion is an issue at the baseline level of long-distance transmission, increasing the transmission capacity will relieve congestion with only a modest increase in cost.”

This is a striking set of assumptions given that it has proven extremely difficult to site vital transmission lines, notably near urban areas (where loads are concentrated).54

In short, expansion of renewable power generation requires ancillary investment in backup capacity using conventional (dispatchable) technologies if frequent service interruptions are to be avoided.”

In summary the AEI study evaluates U.S. electric power generation and energy data for the year 2017 and calculates from that data the amount of new renewable generation required for a 100% renewable generation system, the necessary backup fossil generation required and the resulting GHG emissions associated with this GND scheme.

The study established that 848 GW of conventional generation must be replaced by 2,627 GW’s of new renewable generation to achieve 100% renewable electricity. The much larger amount of replacement renewable generation reflects the much lower capacity factors from renewable power plants versus reliable and predictable fossil generation plant capacity factors. The many issues affecting the much lower renewable energy capacity factors are addressed in detail in the AEI study. The study estimates that the new100% renewable generation system will require 394 GW of backup electric system reserve natural gas combined cycle power plants.

The study utilizes a conservatively low 15% electric system generation reserve margin for its evaluation. Most North American Electric Reliability Corporation (NERC) grid organizations operate with reserve margins in the range between 15% to 25%. The required backup generation is estimated to be operating at about a 40% capacity factor needed to provide all electric grid stability functions, daily ramping of system load, system regulating margin and spinning and standby reserves to prevent power shortages and blackouts.

The study determined that “annual emissions from natural gas backup generation under the GND “100 percent renewables” mandate, perhaps surprisingly, would be 22 percent higher than the emissions from all 2017 natural gas–fired generation and over 35 percent of the emissions from all power generation in 2017. This is the direct result of the unreliability of renewable power: The backup units must be cycled up and down depending on wind and sunlight conditions, thus increasing heat rates (btu per kWh) and emissions.63 The seriousness of this cycling problem is illustrated in Table 2: Annual natural gas backup generation under the GND would be over 6 percent higher than all natural gas generation in 2017, but emissions from natural gas backup power production, again, would be 22 percent higher. In short, the GND “100 percent renewables” mandate—even given the assumptions inherent in the GND policy proposals—to a significant degree is self-defeating as a purported solution to a climate crisis.”

In addition the AEI study addressed the costs that would be associated with the GND electricity mandate which included cost evaluations of new renewable energy capacity and related costs associated with transmission, backup power, land and emissions which are summarized in Table 10 of the study as presented below.


The $490.5 billion dollars per year cost just for the electricity portion of the GND proposal schemes (the GND socialized goodies dealing with single-payer health care, “free” college, national high speed rail system, national building efficiency retrofit program, national employment guarantee, etc are addressed in the AEI study but not in this essay) does NOT include how the sunk costs of the 848 GW of existing conventional generation would be dealt with by the government with the sunk costs of these assets likely to be in the multi trillion dollar range.

The AEI study also provides a breakdown of the electrical system 100% renewable energy GND scheme by each state. Each states year 2017 data is evaluated by addressing its respective generation capacity, fuel mix and energy consumption. The costs for each state reflects the differences between these components among the various states. The graph below presents this data.


For the state of California the cost per household is $1,885 per year or a total annual cost of about $22 billion dollars per year.

The summary of the AEI study clearly notes that the end result of the GND even if zero emissions could be achieved has no discernible impact on global temperatures which is highlighted in the report as follows:

“Moreover, notwithstanding the assertions from GND proponents that it is an essential policy to confront purportedly adverse climate phenomena, the future temperature impacts of the zero-emissions objective would be barely distinguishable from zero: 0.173°C by 2100, under the maximum Intergovernmental Panel on Climate Change parameter (equilibrium climate sensitivity) about the effects of reduced GHG emissions. Under an assumption consistent with the findings reported in the recent peer-reviewed literature, the effect would be 0.083°C by 2100, a policy impact not measurable against normal variation in temperatures. This conclusion is not controversial and suggests strongly that the GND’s real goal is wealth redistribution to favored political interests under the GND social-policy agenda and a dramatic increase in government control of resource allocation more generally”.

Also unaddressed in the GND proposal is the indisputable fact that any reductions in GHG emissions by the U.S., which already leads the world in reducing CO2 emissions, is completely irrelevant to the future growth both cumulatively and incrementally of global emissions which are totally controlled by the world’s developing nations.