The implicatations of dispatchable versus intermittent electricity generation

Many have a strong opinion on where we should go with electricity generation. Opinion does not necessarily equate with fact. Surprisingly little focus is put on the economic and technological aspects of this important matter, considering its vital importance. To say " transition from fossil fuel generation" is easy, but its implementation is proving to be a massive challenge for the world with no immaculate solutions found to date. Anthropogenic greenhouse gas emissions are the cause of the need to transition. The so called 'renewables', (solar panels and wind turbines), have captured the hearts of many. The rich world has gone bonkers, on the mistaken idea that we can get to net zero by using only 'cheap renewables' for generating our electricity. Given the more than a decade that large scale subsidized experiments have been done, experience is clear that relying totally on 'renewables' alone is non-viable.

The Need for Transition

The world's energy consumption has increased by some 8.7 times between 1950 and 2021, an exponential growth of some 3% per annum. This has led to much greater anthropogenic emissions of greenhouse gases. As well as the increase in atmospheric carbon dioxide since the Industrial Revolution, satellite and spacecraft information show that there is a significant deviation in the Earth's outgoing longwave radiation (OLR) at around 15 microns, which corresponds to an absorption band of carbon dioxide. This is clear evidence of a surface-warming effect resulting from our emissions. Extreme weather events are suggestive but not proof of any substantial warming effect of our activities. There are factors, both known and unknown, which affect the climate also. To avoid panic about this, remember that the oceans have an enormous heat capacity compared to the atmosphere, that the energy intensity of the Earth's OLR varies as the fourth power of the absolute temperature and that climate modelling is very inexact. These mechanisms (not the modelling) slow down the rate of surface heating, that is, cause a lag. We need to transition, but we should best do it without a knee jerk reaction and with essentially global agreement on how to proceed. Also, best done on the basis of technology and economics, rather than on ignorant ideology or should that be idiotology?

Definitions

Dispatchable

Dispatchable generators are those that can quickly provide electricity when called upon and can vary with demand. These include fossil and nuclear fission.

Intermittent

Intermittent generators are those that produce electricity at irregular intervals, not continuous or steady, coming and going at intervals, sporadic. These include solar and wind.

Categorical Difference

Dispatchable and intermittent define the two categories of electricity generators in terms of their critical performance characteristics. Dispatchable generators include all fossil fuels and nuclear fission. Intermittent generators include solar panels and wind turbines. The critical, essential, significant difference between the performance characteristics of these two classes of electricity generators is, in general, either is not well-understood or is ignored. Society wants reliable, affordable electricity on demand, 24/7 and now carbon-free. Without the backup of dispatchable generators, 'renewable' generators are not fit for purpose. This has been world experience and can be deduced also from a technological and economic evaluation basis. Dispatchable generators are indispensable, whereas 'renewable' generators are not indispensable to an electricity utility.

Individual Generator Costs

Comparing dispatchable to intermittent generators is not possible by the method used in the past (Levelised Cost of Electricity) because intermittents only work when the weather obliges, also the redundancy. Consider a 10MW coal-fired power generator and a 10MW solar panel array. Given that the solar panels only work for about 6 hours a day on average, the 24 hour output of the solar array is 2.5 MW. This means the solar array is only useful for ¼ of a day, so comparing the 2 systems on the basis of 10MW capacity is invalid. Take note also that the capital cost of the solar array must be increased by four times to compare with that of the coal-fired generator. Similar considerations apply to wind turbines. 'Renewables' are cheaper to operate, costing essentially nothing, but when the capital costs are included, as good accountancy or reality dictates, the picture is not so rosy, even comparing generators in isolation. In addition, the 'renewables' cannot supply electricity needed on demand. Also to provide the 10MW for 24 hours the 'renewables' require expensive battery backup.

System Costs

To make any sense of the matter, we need to compare total system costs and not individual costs of different generators. The ultimate metric is the cost of electricity to consumers, which includes more costs than just the stand-alone cost of a generator. This means taking into account all the costs of delivering electricity to the consumer.

Electricity utilities with a high proportion of dispatchable generators are typically configured as high-density, continuous, centralized facilities, requiring transmission only to supply on demand and taking up minimal area for their output. On the other hand electricity utilities with a significant proportion of 'renewable' generators are characterized by low-density intermittent and decentralized facilities, requiring expensive ancillary facilities, including land and transmission. This comparison alone is enough to show that 'renewables are not a cheap form of energy'. Coal is, and nuclear next, as high-density continuous, centralized facilities. If 'renewables' were so good, subsidies would not be needed to encourage their construction. It is also noteworthy that France, with some 62% of its power from nuclear does not have the highest consumer electricity price in the EU.

Output from dispatchable generators is essentially constant in regard to voltage and frequency. In the case of intermittents, when they happen to be operating at the pleasure of the weather, their output is forever varying. In the case of solar, we have a varying DC output which has to be converted to AC 50Hz for consumption, often with considerable losses in transmission if the panels are located far from consumption. In the case of wind turbines we have ever-changing wind strength varying the speed of rotation of the turbines with consequent change in voltage and frequency output. Again considerable adjustment has to be made to the variable output from these generators for consumption in equipment designed for 50 Hz and 240 V for domestic supply. The cost of the equipment needed to convert the varying electricity output to fit the consumer is hidden from the general public and it is substantial.

Conclusions

Society wants reliable, affordable and now carbon-free electricity on demand, 24/7 and with minimal environmental degradation.

Although solar and wind are cheap to operate, per se, their total costs are not cheap and they are not fit for purpose alone. World experience to date confirms this. Electricity utilities employing 'renewables' must have a component of dispatchable generation in the mix. Gas is a compromise dispatchable. It still emits carbon dioxide, but less so than coal-fired power for the same amount of electricity. The only carbon-free dispatchable electricity generating source generally available at the present state of technology is nuclear fission.