No, I don’t hate “renewables”

20 07 2019

Another masterpiece from Tim who keeps churning out great stuff on his website……

During a conversation with a friend yesterday I was asked why I was so hostile toward “renewables” – or as I prefer to call them, non-renewablerenewable energy-harvesting technologies.  My answer was that I am not opposed to these technologies, but rather to the role afforded to them by the Bright Green techno-utopian crowd, who continue to churn out propaganda to the effect that humankind can continue to metastasise across the universe without stopping for breath simply by replacing the energy we derive from fossil fuels with energy we harvest with wind and tide turbines, solar panels and geothermal pumps.  These, I explained to my friend, will unquestionably play a role in our future; but to nowhere near the extent claimed by the proponents of green capitalism, ecosocialism or the green new deal.

It would seem that I was not alone in being asked why I was so disapproving of “renewables.”  On the same day, American essayist John Michael Greer addressed the same question on his Ecosophia blog:

“Don’t get me wrong, I’m wholly in favor of renewables; they’re what we’ll have left when fossil fuels are gone; but anyone who thinks that the absurdly extravagant energy use that props up a modern lifestyle can be powered by PV cells simply hasn’t done the math. Yet you’ll hear plenty of well-intentioned people these days insisting that if we only invest in solar PV we can stop using fossil fuels and still keep our current lifestyles.”

Greer also explains why so many techno-utopians have such a starry-eyed view of “renewables” like solar panels:

“The result of [decades of development] can be summed up quite readily: the only people who think that an energy-intensive modern lifestyle can be supported entirely on solar PV are those who’ve never tried it. You can get a modest amount of electrical power intermittently from PV cells; if you cover your roof with PV cells and have a grid tie-in that credits you at a subsidized rate, you can have all the benefits of fossil fuel-generated electricity and still convince yourself that you’re not dependent on fossil fuels; but if you go off-grid, you’ll quickly learn the hard limits of solar PV.”

Greer is not alone in having to spell this out.  The first article I read yesterday morning was a new post from Tim Morgan on his Surplus Energy Economics blog, where he makes the case that even if we were not facing a climate emergency, our dependence upon fossil fuels still dooms our civilisation to an imminent collapse:

“Far from ensuring ‘business as usual’, continued reliance on fossil fuel energy would have devastating economic consequences. As is explained here, the world economy is already suffering from these effects, and these have prompted the adoption of successively riskier forms of financial manipulation in a failed effort to sustain economic ‘normality’.”

The reason is what Morgan refers to as the rapidly-rising “energy cost of energy” (ECoE) – a calculation related to Net Energy and Energy Return on Energy Invested (EROI).  Put simply, industrial civilisation has devoured each fossil fuel beginning with the cheapest and easiest deposits and then falling back on ever harder and more expensive deposits as these run out.  The result is that the amount of surplus energy left over to grow the economy after we have invested in energy for the future and in the maintenance and repair of the infrastructure we have already developed gets smaller and harder to obtain with each passing month.

Morgan sets out four factors which determine the Energy Cost of Energy:

  • Geographical reach – as local deposits are exhausted, we are obliged to go further afield for replacements.
  • Economies of scale – as our infrastructure develops, we rationalise it in order to keep costs to a minimum; for example, having a handful of giant oil refineries rather than a large number of small ones. Unfortunately, this is a one-off gain, after which the cost of maintenance and repair results in diminishing returns.
  • Depletion – most of the world’s oil and coal deposits are now in decline, after providing the basis for the development of industrial civilisation. Without replacement, depletion dooms us to some form of degrowth.
  • Technology – the development of technologies that provide a greater return for the energy invested can offset some of the rising ECoE, but like economies of scale, they come with diminishing returns and are ultimately limited by the laws of thermodynamics:

“To be sure, advances in technology can mitigate the rise in ECoEs, but technology is limited by the physical properties of the resource. Advances in techniques have reduced the cost of shale liquids extraction to levels well below the past cost of extracting those same resources, but have not turned America’s tight sands into the economic equivalent of Saudi Arabia’s al Ghawar, or other giant discoveries of the past.

“Physics does tend to have the last word.”

Morgan argues that by focusing solely on financial matters, mainstream economics misses the central role of surplus energy in the economy:

“According to SEEDS – the Surplus Energy Economics Data System – world trend ECoE rose from 2.9% in 1990 to 4.1% in 2000. This increase was more than enough to stop Western prosperity growth in its tracks.

“Unfortunately, a policy establishment accustomed to seeing all economic developments in purely financial terms was at a loss to explain this phenomenon, though it did give it a name – “secular stagnation”.

“Predictably, in the absence of an understanding of the energy basis of the economy, recourse was made to financial policies in order to ‘fix’ this slowdown in growth.

“The first such initiative was credit adventurism. It involved making debt easier to obtain than ever before. This approach was congenial to a contemporary mind-set which saw ‘deregulation’ as a cure for all ills.”

The inevitable result was the financial crash in 2008, when unrepayable debt threatened to unwind the entire global financial system.  And while the financial crisis has been temporarily offset by more of the same medicine – quantitative easing and interest rate cuts – it has been the continued expansion of emerging markets that has actually kept the system limping along:

“World average prosperity per capita has declined only marginally since 2007, essentially because deterioration in the West has been offset by continued progress in the emerging market (EM) economies. This, though, is nearing its point of inflexion, with clear evidence now showing that the Chinese economy, in particular, is in very big trouble.

“As you’d expect, these trends in underlying prosperity have started showing up in ‘real world’ indicators, with trade in goods, and sales of everything from cars and smartphones to computer chips and industrial components, now turning down. As the economy of ‘stuff’ weakens, a logical consequence is likely to be a deterioration in demand for the energy and other commodities used in the supply of “stuff”.

“Simply stated, the economy has now started to shrink, and there are limits to how long we can hide this from ourselves by spending ever larger amounts of borrowed money.”

The question this raises is not simply, can we replace fossil fuels with non-renewable renewable energy-harvesting technologies (Morgan refers to them as “secondary applications of primary energy from fossil fuels”) but can we deploy them at an ECoE that allows us to avoid the collapse of industrial civilisation?  Morgan argues not.  The techno-utopian bad habit of applying Moore’s Law to every technology has allowed economists and politicians to assume that the cost of non-renewable renewable energy-harvesting technologies will keep halving even as the energy they generate continues to double.  However:

“[W]e need to guard against the extrapolatory fallacy which says that, because the ECoE of renewables has declined by x% over y number of years, it will fall by a further x% over the next y. The problem with this is that it ignores the limits imposed by the laws of physics.”

More alarming, however, is the high ECoE of non-renewable renewable energy-harvesting technologies; despite their becoming cheaper than some fossil fuel deposits:

“…there can be no assurance that the ECoE of a renewables-based energy system can ever be low enough to sustain prosperity. Back in the ‘golden age’ of prosperity growth (in the decades immediately following 1945), global ECoE was between 1% and 2%. With renewables, the best that we can hope for might be an ECoE stable at perhaps 8%, far above the levels at which prosperity deteriorates in the West, and ceases growing in the emerging economies.”

At this point, no doubt, some readers at least will be asking Morgan why he dislikes “renewables” so much.  And his answer is the same as Greer’s and my own:

“These cautions do not, it must be stressed, undermine the case for transitioning from fossil fuels to renewables. After all, once we understand the energy processes which drive the economy, we know where continued dependency on ever-costlier fossil fuels would lead.

“There can, of course, be no guarantees around a successful transition to renewable forms of energy. The slogan “sustainable development” has been adopted by the policy establishment because it seems to promise the public that we can tackle environmental risk without inflicting economic hardship, or even significant inconvenience.”

Morgan’s broad point here is that there is a false dichotomy between addressing environmental concerns and maintaining economic growth.  The economy is toast irrespective of whether we address environment crises or not.  There is not enough fossil fuel energy to prevent he system from imploding – the only real question to be answered is whether we continue with business as usual until we crash and burn or whether we take at least some mitigating actions to preserve a few of the beneficial aspects of the last 250 years of economic development.  After all, having clean drinking water, enough food to ward off starvation and some basic health care would make the coming collapse easier than it otherwise might be.

The problem, however, is that even with the Herculean efforts to deploy non-renewable renewable energy-harvesting technologies in the decades since the oil crisis in 1973, they still only account for four percent of our primary energy.  As Morgan cautions, it is too easy for westerners to assume that our total energy consumption is entirely in the gas and electricity we use at home and in the fuel we put in the tanks of our vehicles.  In reality this is but a tiny fraction of our energy use (and carbon footprint) with most of our energy embodied within all of the goods and services we consume.  Not only does fossil fuel account for more than 85 percent of the world’s primary energy, but both BP and the International Energy Agency reports for 2018 show that fossil fuel consumption is growing at a faster rate than non-renewable renewable energy-harvesting technologies are being installed.

Nor is there a green new deal route out of this problem.  As a recent letter to the UK’s Committee on Climate Change, authored by Natural History Museum Head of Earth Sciences Prof Richard Herrington et al., warns:

“To replace all UK-based vehicles today with electric vehicles (not including the LGV and HGV fleets), assuming they use the most resource-frugal next-generation NMC 811 batteries, would take 207,900 tonnes cobalt, 264,600 tonnes of lithium carbonate (LCE), at least 7,200 tonnes of neodymium and dysprosium, in addition to 2,362,500 tonnes copper. This represents, just under two times the total annual world cobalt production, nearly the entire world production of neodymium, three quarters the world’s lithium production and at least half of the world’s copper production during 2018. Even ensuring the annual supply of electric vehicles only, from 2035 as pledged, will require the UK to annually import the equivalent of the entire annual cobalt needs of European industry…

“There are serious implications for the electrical power generation in the UK needed to recharge these vehicles. Using figures published for current EVs (Nissan Leaf, Renault Zoe), driving 252.5 billion miles uses at least 63 TWh of power. This will demand a 20% increase in UK generated electricity.

“Challenges of using ‘green energy’ to power electric cars: If wind farms are chosen to generate the power for the projected two billion cars at UK average usage, this requires the equivalent of a further years’ worth of total global copper supply and 10 years’ worth of global neodymium and dysprosium production to build the windfarms.

“Solar power is also problematic – it is also resource hungry; all the photovoltaic systems currently on the market are reliant on one or more raw materials classed as “critical” or “near critical” by the EU and/ or US Department of Energy (high purity silicon, indium, tellurium, gallium) because of their natural scarcity or their recovery as minor-by-products of other commodities. With a capacity factor of only ~10%, the UK would require ~72GW of photovoltaic input to fuel the EV fleet; over five times the current installed capacity. If CdTe-type photovoltaic power is used, that would consume over thirty years of current annual tellurium supply.

“Both these wind turbine and solar generation options for the added electrical power generation capacity have substantial demands for steel, aluminium, cement and glass.”

Put simply, there is not enough Planet Earth left for us to grow our way to sustainability.  The only option open to us is to rapidly shrink our activities and our population back to something that can be sustained without further depleting the planet we depend upon.  Continue with business as usual and Mother Nature is going to do to us what we did to the dodo and the passenger pigeon.  Begin taking some radical action – which still allows the use of some resources and fossil fuels – to switch from an economy of desires to one of needs and at least a fewhumans might survive what is coming.

The final problem, though, is that very few people – including many of those who protest government inaction on the environment – are prepared to make the sacrifices required.  Nor are our corporations and institutions prepared to forego their power and profits for the greater good.  And that leaves us with political structures that will inevitably favour business as usual.

So no, I don’t hate “renewables” – I just regard those who blithely claim that we can deploy and use them to replace fossil fuels without breaking a sweat to be as morally bankrupt as any climate change denying politician you care to mention.  There is a crash on the horizon, the likes of which we haven’t seen since the fourteenth century.  When the energy cost of securing energy – whether fossil fuel, nuclear or renewable – exceeds the energy cost of sustaining the system; our ability to take mitigating action will be over.  Exactly when this is going to happen is a matter of speculation (we should avoid mistaking inevitability for imminence).  Nevertheless, the window for taking action is closing fast; and promising Bright Green utopias as we slide over the cliff edge is not helping anybody.





How (Not) to Run a Modern Society on Solar and Wind Power Alone

20 07 2019

This is a great article from Low-Tech Magazine explaining the limitations of renewable energy. Let me tell you, now we are off grid and not relying on it for the house site, I have personally visited the limits of solar energy on several occasions. Winter, in particular, really tests my ability to do things, even building. We’ve had lengthy rainy periods when the solar array has literally produced nothing whatsoever, and I couldn’t even use power tools. When the sun shines, I can do anything. But when it doesn’t……. to add insult to injury, even owning a wind turbine would not help, because at this time of year there’s no useable wind!

While the potential of wind and solar energy is more than sufficient to supply the electricity demand of industrial societies, these resources are only available intermittently. To ensure that supply always meets demand, a renewable power grid needs an oversized power generation and transmission capacity of up to ten times the peak demand. It also requires a balancing capacity of fossil fuel power plants, or its equivalent in energy storage. 

Consequently, matching supply to demand at all times makes renewable power production a complex, slow, expensive and unsustainable undertaking. Yet, if we would adjust energy demand to the variable supply of solar and wind energy, a renewable power grid could be much more advantageous. Using wind and solar energy only when they’re available is a traditional concept that modern technology can improve upon significantly.

100% Renewable Energy

It is widely believed that in the future, renewable energy production will allow modern societies to become independent from fossil fuels, with wind and solar energy having the largest potential. An oft-stated fact is that there’s enough wind and solar power available to meet the energy needs of modern civilisation many times over.

For instance, in Europe, the practical wind energy potential for electricity production on- and off-shore is estimated to be at least 30,000 TWh per year, or ten times the annual electricity demand. [1] In the USA, the technical solar power potential is estimated to be 400,000 TWh, or 100 times the annual electricity demand. [2]

Such statements, although theoretically correct, are highly problematic in practice. This is because they are based on annual averages of renewable energy production, and do not address the highly variable and uncertain character of wind and solar energy. 

Annual averages of renewable energy production do not address the highly variable and uncertain character of wind and solar energy

Demand and supply of electricity need to be matched at all times, which is relatively easy to achieve with power plants that can be turned on and off at will. However, the output of wind turbines and solar panels is totally dependent on the whims of the weather.

Therefore, to find out if and how we can run a modern society on solar and wind power alone, we need to compare time-synchronised electricity demand with time-synchronised solar or wind power availability. [3][4] [5] In doing so, it becomes clear that supply correlates poorly with demand.


The intermittency of solar en wind energy compared to demand

Above: a visualisation of 30 days of superimposed power demand time series data (red), wind energy generation data (blue), and solar insolation data (yellow). Average values are in colour-highlighted black lines. Data obtained from Bonneville Power Administration, April 2010. Source: [21]


The Intermittency of Solar Energy

Solar power is characterised by both predictable and unpredictable variations. There is a predictable diurnal and seasonal pattern, where peak output occurs in the middle of the day and in the summer, depending on the apparent motion of the sun in the sky. [6] [7]

When the sun is lower in the sky, its rays have to travel through a larger air mass, which reduces their strength because they are absorbed by particles in the atmosphere. The sun’s rays are also spread out over a larger horizontal surface, decreasing the energy transfer per unit of horizontal surface area.

When the sun is 60° above the horizon, the sun’s intensity is still 87% of its maximum when it reaches a horizontal surface. However, at lower angles, the sun’s intensity quickly decreases. At a solar angle of 15°, the radiation that strikes a horizontal surface is only 25% of its maximum. 

On a seasonal scale, the solar elevation angle also correlates with the number of daylight hours, which reduces the amount of solar energy received over the course of a day at times of the year when the sun is already lower in the sky. And, last but not least, there’s no solar energy available at night.

Cloud map

Image: Average cloud cover 2002 – 2015. Source: NASA.

Likewise, the presence of clouds adds unpredictable variations to the solar energy supply. Clouds scatter and absorb solar radiation, reducing the amount of insolation that reaches the ground below. Solar output is roughly 80% of its maximum with a light cloud cover, but only 15% of its maximum on a heavy overcast day. [8][9][10]

Due to a lack of thermal or mechanical inertia in solar photovoltaic (PV) systems, the changes due to clouds can be dramatic. For example, under fluctuating cloud cover, the output of multi-megawatt PV power plants in the Southwest USA was reported to have variations of roughly 50% in a 30 to 90 second timeframe and around 70% in a timeframe of 5 to 10 minutes. [6]

In London, a solar panel produces 65 times less energy on a heavy overcast day in December at 10 am than on a sunny day in June at noon. 

The combination of these predictable and unpredictable variations in solar power makes it clear that the output of a solar power plant can vary enormously throughout time. In Phoenix, Arizona, the sunniest place in the USA, a solar panel produces on average 2.7 times less energy in December than in June. Comparing a sunny day at midday in June with a heavy overcast day at 10 am in December, the difference in solar output is almost twentyfold. [11]

In London, UK, which is a moderately suitable location for solar power, a solar panel produces on average 10 times less energy in December than in June. Comparing a sunny day in June at noon with a heavy overcast day in December at 10 am, the solar output differs by a factor of 65. [8][9]

The Intermittency of Wind Energy

Compared to solar energy, the variability of the wind is even more volatile. On the one hand, wind energy can be harvested both day and night, while on the other hand, it’s less predictable and less reliable than solar energy. During daylight hours, there’s always a minimum amount of solar power available, but this is not the case for wind, which can be absent or too weak for days or even weeks at a time. There can also be too much wind, and wind turbines then have to be shut down in order to avoid damage.

On average throughout the year, and depending on location, modern wind farms produce 10-45% of their rated maximum power capacity, roughly double the annual capacity factor of the average solar PV installation (5-30%). [6] [12][13][14] In practice, however, wind turbines can operate between 0 and 100% of their maximum power at any moment.


Hourly wind power output on 29 different days in april 2005 at a wind plant in california

Hourly wind power output on 29 different days in april 2005 at a wind plant in california. Source: [6]


For many locations, only average wind speed data is available. However, the chart above shows the daily and hourly wind power output on 29 different days at a wind farm in California. At any given hour of the day and any given day of the month, wind power production can vary between zero and 600 megawatt, which is the maximum power production of the wind farm. [6]

Even relatively small changes in wind speed have a large effect on wind power production: if the wind speed decreases by half, power production decreases by a factor of eight. [15] Wind resources also vary throughout the years. Germany, the Netherlands and Denmark show a wind speed inter-annual variability of up to 30%. [1] Yearly differences in solar power can also be significant. [16] [17]

How to Match Supply with Demand?

To some extent, wind and solar energy can compensate for each other. For example, wind is usually twice as strong during the winter months, when there is less sun. [18] However, this concerns average values again. At any particular moment of the year, wind and solar energy may be weak or absent simultaneously, leaving us with little or no electricity at all.

Electricity demand also varies throughout the day and the seasons, but these changes are more predictable and much less extreme. Demand peaks in the morning and in the evening, and is at its lowest during the night. However, even at night, electricity use is still close to 60% of the maximum. 

At any particular moment of the year, wind and solar energy may be weak or absent simultaneously, leaving us with little or no electricity at all.

Consequently, if renewable power capacity is calculated based on the annual averages of solar and wind energy production and in tune with the average power demand, there would be huge electricity shortages for most of the time. To ensure that electricity supply always meets electricity demand, additional measures need to be taken.

First, we could count on a backup infrastructure of dispatchable fossil fuel power plants to supply electricity when there’s not enough renewable energy available. Second, we could oversize the renewable generation capacity, adjusting it to the worst case scenario. Third, we could connect geographically dispersed renewable energy sources to smooth out variations in power production. Fourth, we could store surplus electricity for use in times when solar and/or wind resources are low or absent.

As we shall see, all of these strategies are self-defeating on a large enough scale, even when they’re combined. If the energy used for building and maintaining the extra infrastructure is accounted for in a life cycle analysis of a renewable power grid, it would be just as CO2-intensive as the present-day power grid. 

Strategy 1: Backup Power Plants

Up to now, the relatively small share of renewable power sources added to the grid has been balanced by dispatchable forms of electricity, mainly rapidly deployable gas power plants. Although this approach completely “solves” the problem of intermittency, it results in a paradox because the whole point of switching to renewable energy is to become independent of fossil fuels, including gas. [19]

Most scientific research focuses on Europe, which has the most ambitious plans for renewable power. For a power grid based on 100% solar and wind power, with no energy storage and assuming interconnection at the national European level only, the balancing capacity of fossil fuel power plants needs to be just as large as peak electricity demand. [12] In other words, there would be just as many non-renewable power plants as there are today.

Power plant capacity united states

Every power plant in the USA. Visualisation by The Washington Post.

Such a hybrid infrastructure would lower the use of carbon fuels for the generation of electricity, because renewable energy can replace them if there is sufficient sun or wind available. However, lots of energy and materials need to be invested into what is essentially a double infrastructure. The energy that’s saved on fuel is spent on the manufacturing, installation and interconnection of millions of solar panels and wind turbines.

Although the balancing of renewable power sources with fossil fuels is widely regarded as a temporary fix that’s not suited for larger shares of renewable energy, most other technological strategies (described below) can only partially reduce the need for balancing capacity.

Strategy 2: Oversizing Renewable Power Production

Another way to avoid energy shortages is to install more solar panels and wind turbines. If solar power capacity is tailored to match demand during even the shortest and darkest winter days, and wind power capacity is matched to the lowest wind speeds, the risk of electricity shortages could be reduced significantly. However, the obvious disadvantage of this approach is an oversupply of renewable energy for most of the year.

During periods of oversupply, the energy produced by solar panels and wind turbines is curtailed in order to avoid grid overloading. Problematically, curtailment has a detrimental effect on the sustainability of a renewable power grid. It reduces the electricity that a solar panel or wind turbine produces over its lifetime, while the energy required to manufacture, install, connect and maintain it remains the same. Consequently, the capacity factor and the energy returned for the energy invested in wind turbines and solar panels decrease. [20]

Installing more solar panels and wind turbines reduces the risk of shortages, but it produces an oversupply of electricity for most of the year.

Curtailment rates increase spectacularly as wind and solar comprise a larger fraction of the generation mix, because the overproduction’s dependence on the share of renewables is exponential. Scientists calculated that a European grid comprised of 60% solar and wind power would require a generation capacity that’s double the peak load, resulting in 300 TWh of excess electricity every year (roughly 10% of the current annual electricity consumption in Europe).

In the case of a grid with 80% renewables, the generation capacity needs to be six times larger than the peak load, while the excess electricity would be equal to 60% of the EU’s current annual electricity consumption. Lastly, in a grid with 100% renewable power production, the generation capacity would need to be ten times larger than the peak load, and excess electricity would surpass the EU annual electricity consumption. [21] [22] [23] 

This means that up to ten times more solar panels and wind turbines need to be manufactured. The energy that’s needed to create this infrastructure would make the switch to renewable energy self-defeating, because the energy payback times of solar panels and wind turbines would increase six- or ten-fold.

For solar panels, the energy payback would only occur in 12-24 years in a power grid with 80% renewables, and in 20-40 years in a power grid with 100% renewables. Because the life expectancy of a solar panel is roughly 30 years, a solar panel may never produce the energy that was needed to manufacture it. Wind turbines would remain net energy producers because they have shorter energy payback times, but their advantage compared to fossil fuels would decrease. [24]

Strategy 3: Supergrids

The variability of solar and wind power can also be reduced by interconnecting renewable power plants over a wider geographical region. For example, electricity can be overproduced where the wind is blowing but transmitted to meet demand in becalmed locations. [19]

Interconnection also allows the combination of technologies that utilise different variable power resources, such as wave and tidal energy. [3] Furthermore, connecting power grids over large geographical areas allows a wider sharing of backup fossil fuel power plants.

Wind map europe saturday september 2 2017 23h48

Wind map of Europe, September 2, 2017, 23h48. Source: Windy.

Although today’s power systems in Europe and the USA stretch out over a large enough area, these grids are currently not strong enough to allow interconnection of renewable energy sources. This can be solved with a powerful overlay high-voltage DC transmission grid. Such “supergrids” form the core of many ambitious plans for 100% renewable power production, especially in Europe. [25] The problem with this strategy is that transmission capacity needs to be overbuilt, over very long distances. [19]

For a European grid with a share of 60% renewable power (an optimal mix of wind and solar), grid capacity would need to be increased at least sevenfold. If individual European countries would disregard national concerns about security of supply, and backup balancing capacity would be optimally distributed throughout the continent, the necessary grid capacity extensions can be limited to about triple the existing European high-voltage grid. For a European power grid with a share of 100% renewables, grid capacity would need to be up to twelve times larger than it is today. [21] [26][27]

Even in the UK, which has one of the best renewable energy sources in the world, combining wind, sun, wave and tidal power would still generate electricity shortages for 65 days per year.

The problems with such grid extensions are threefold. Firstly, building infrastructure such as transmission towers and their foundations, power lines, substations, and so on, requires a significant amount of energy and other resources. This will need to be taken into account when making a life cycle analysis of a renewable power grid. As with oversizing renewable power generation, most of the oversized transmission infrastructure will not be used for most of the time, driving down the transmission capacity factor substantially.

Secondly, a supergrid involves transmission losses, which means that more wind turbines and solar panels will need to be installed to compensate for this loss. Thirdly, the acceptance of and building process for new transmission lines can take up to ten years. [20][25] This is not just bureaucratic hassle: transmission lines have a high impact on the land and often face local opposition, which makes them one of the main obstacles for the growth of renewable power production.

Even with a supergrid, low power days remain a possibility over areas as large as Europe. With a share of 100% renewable energy sources and 12 times the current grid capacity, the balancing capacity of fossil fuel power plants can be reduced to 15% of the total annual electricity consumption, which represents the maximum possible benefit of transmission for Europe. [28]

Even in the UK, which has one of the best renewable energy sources in the world, interconnecting wind, sun, wave and tidal power would still generate electricity shortages for 18% of the time (roughly 65 days per year). [29] [30][31]

Strategy 4: Energy Storage

A final strategy to match supply to demand is to store an oversupply of electricity for use when there is not enough renewable energy available. Energy storage avoids curtailment and it’s the only supply-side strategy that can make a balancing capacity of fossil fuel plants redundant, at least in theory. In practice, the storage of renewable energy runs into several problems.

First of all, while there’s no need to build and maintain a backup infrastructure of fossil fuel power plants, this advantage is negated by the need to build and maintain an energy storage infrastructure. Second, all storage technologies have charging and discharging losses, which results in the need for extra solar panels and wind turbines to compensate for this loss. 

Wind map usa

Live wind map of the USA

The energy required to build and maintain the storage infrastructure and the extra renewable power plants need to be taken into account when conducting a life cycle analysis of a renewable power grid. In fact, research has shown that it can be more energy efficient to curtail renewable power from wind turbines than to store it, because the energy needed to manufacture storage and operate it (which involves charge-discharge losses) surpasses the energy that is lost through curtailment. [23]

If we count on electric cars to store the surplus of renewable electricity, their batteries would need to be 60 times larger than they are today

It has been calculated that for a European power grid with 100% renewable power plants (670 GW wind power capacity and 810 GW solar power capacity) and no balancing capacity, the energy storage capacity needs to be 1.5 times the average monthly load and amounts to 400 TWh, not including charging and discharging losses. [32] [33] [34]

To give an idea of what this means: the most optimistic estimation of Europe’s total potential for pumped hydro-power energy storage is 80 TWh [35], while converting all 250 million passenger cars in Europe to electric drives with a 30 kWh battery would result in a total energy storage of 7.5 TWh. In other words, if we count on electric cars to store the surplus of renewable electricity, their batteries would need to be 60 times larger than they are today (and that’s without allowing for the fact that electric cars will substantially increase power consumption).

Taking into account a charging/discharging efficiency of 85%, manufacturing 460 TWh of lithium-ion batteries would require 644 million Terajoule of primary energy, which is equal to 15 times the annual primary energy use in Europe. [36] This energy investment would be required at minimum every twenty years, which is the most optimistic life expectancy of lithium-ion batteries. There are many other technologies for storing excess electricity from renewable power plants, but all have unique disadvantages that make them unattractive on a large scale. [37] [38]

Matching Supply to Demand = Overbuilding the Infrastructure

In conclusion, calculating only the energy payback times of individual solar panels or wind turbines greatly overestimates the sustainability of a renewable power grid. If we want to match supply to demand at all times, we also need to factor in the energy use for overbuilding the power generation and transmission capacity, and the energy use for building the backup generation capacity and/or the energy storage. The need to overbuild the system also increases the costs and the time required to switch to renewable energy.

Calculating only the energy payback times of individual solar panels or wind turbines greatly overestimates the sustainability of a renewable power grid.

Combining different strategies is a more synergistic approach which improves the sustainability of a renewable power grid, but these advantages are not large enough to provide a fundamental solution. [33] [39] [40]

Building solar panels, wind turbines, transmission lines, balancing capacity and energy storage using renewable energy instead of fossil fuels doesn’t solve the problem either, because it also assumes an overbuilding of the infrastructure: we would need to build an extra renewable energy infrastructure to build the renewable energy infrastructure.

Adjusting Demand to Supply

However, this doesn’t mean that a sustainable renewable power grid is impossible. There’s a fifth strategy, which does not try to match supply to demand, but instead aims to match demand to supply. In this scenario, renewable energy would ideally be used only when it’s available. 

If we could manage to adjust all energy demand to variable solar and wind resources, there would be no need for grid extensions, balancing capacity or overbuilding renewable power plants. Likewise, all the energy produced by solar panels and wind turbines would be utilised, with no transmission losses and no need for curtailment or energy storage.  

Moulbaix Belgium  the windmill de la Marquise XVII XVIIIth centuries

Windmill in Moulbaix, Belgium, 17th/18th century. Image: Jean-Pol GrandMont.

Of course, adjusting energy demand to energy supply at all times is impossible, because not all energy using activities can be postponed. However, the adjustment of energy demand to supply should take priority, while the other strategies should play a supportive role. If we let go of the need to match energy demand for 24 hours a day and 365 days a year, a renewable power grid could be built much faster and at a lower cost, making it more sustainable overall.

If we could manage to adjust all energy demand to variable solar and wind resources, there would no need for energy storage, grid extensions, balancing capacity or overbuilding renewable power plants.

With regards to this adjustment, even small compromises yield very beneficial results. For example, if the UK would accept electricity shortages for 65 days a year, it could be powered by a 100% renewable power grid (solar, wind, wave & tidal power) without the need for energy storage, a backup capacity of fossil fuel power plants, or a large overcapacity of power generators. [29] 

If demand management is discussed at all these days, it’s usually limited to so-called ‘smart’ household devices, like washing machines or dishwashers that automatically turn on when renewable energy supply is plentiful. However, these ideas are only scratching the surface of what’s possible.

Before the Industrial Revolution, both industry and transportation were largely dependent on intermittent renewable energy sources. The variability in the supply was almost entirely solved by adjusting energy demand. For example, windmills and sailing boats only operated when the wind was blowing. In the next article, I will explain how this historical approach could be successfully applied to modern industry and cargo transportation.

Kris De Decker (edited by Jenna Collett)


Sources:

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[2] Lopez, Anthony, et al. US renewable energy technical potentials: a GIS-based analysis. NREL, 2012. See also Here’s how much of the world would need to be covered in solar panels to power Earth, Business Insider, October 2015.

[3] Hart, Elaine K., Eric D. Stoutenburg, and Mark Z. Jacobson. “The potential of intermittent renewables to meet electric power demand: current methods and emerging analytical techniques.” Proceedings of the IEEE 100.2 (2012): 322-334.

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[5] Mulder, F. M. “Implications of diurnal and seasonal variations in renewable energy generation for large scale energy storage.” Journal of Renewable and Sustainable Energy 6.3 (2014): 033105.

[6] INITIATIVE, MIT ENERGY. “Managing large-scale penetration of intermittent renewables.” (2012).

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[8] Sun Angle and Insolation. FTExploring.

[9]  Sun position calculator, Sun Earth Tools.

[10] Burgess, Paul. ” Variation in light intensity at different latitudes and seasons effects of cloud cover, and the amounts of direct and diffused light.” Forres, UK: Continuous Cover Forestry Group. Available online at http://www. ccfg. org. uk/conferences/downloads/P_Burgess. pdf. 2009.

[11] Solar output can be increased, especially in winter, by tilting solar panels so that they make a 90 degree angle with the sun’s rays. However, this only addresses the spreading out of solar irradiation and has no effect on the energy lost because of the greater air mass, nor on the amount of daylight hours. Furthermore, tilting the panels is always a compromise. A panel that’s ideally tilted for the winter sun will be less efficient in the summer sun, and the other way around.

[12] Schaber, Katrin, Florian Steinke, and Thomas Hamacher. “Transmission grid extensions for the integration of variable renewable energies in europe: who benefits where?.” Energy Policy 43 (2012): 123-135.

[13] German offshore wind capacity factors, Energy Numbers, July 2017

[14] What are the capacity factors of America’s wind farms? Carbon Counter, 24 July 2015.

[15] Sorensen, Bent. Renewable Energy: physics, engineering, environmental impacts, economics & planning; Fourth Edition. Elsevier Ltd, 2010.

[16] Jerez, S., et al. “The Impact of the North Atlantic Oscillation on Renewable Energy Resources in Southwestern Europe.” Journal of applied meteorology and climatology 52.10 (2013): 2204-2225.

[17] Eerme, Kalju. “Interannual and intraseasonal variations of the available solar radiation.” Solar Radiation. InTech, 2012.

[18] Archer, Cristina L., and Mark Z. Jacobson. “Geographical and seasonal variability of the global practical wind resources.” Applied Geography 45 (2013): 119-130.

[19] Rugolo, Jason, and Michael J. Aziz. “Electricity storage for intermittent renewable sources.” Energy & Environmental Science 5.5 (2012): 7151-7160.

[20] Even at today’s relatively low shares of renewables, curtailment is already happening, caused by either transmission congestion, insufficient transmission availability, or minimal operating levels on thermal generators (coal and atomic power plants are designed to operate continuously). See: “Wind and solar curtailment”, Debra Lew et al., National Renewable Energy Laboratory, 2013. For example, in China, now the world’s top wind power producer, nearly one-fifth of total wind power is curtailed. See: Chinese wind earnings under pressure with fifth of farms idle, Sue-Lin Wong & Charlie Zhu, Reuters, May 17, 2015.

[21] Barnhart, Charles J., et al. “The energetic implications of curtailing versus storing solar- and wind-generated electricity.” Energy & Environmental Science 6.10 (2013): 2804-2810.

[22] Schaber, Katrin, et al. “Parametric study of variable renewable energy integration in europe: advantages and costs of transmission grid extensions.” Energy Policy 42 (2012): 498-508.

[23] Schaber, Katrin, Florian Steinke, and Thomas Hamacher. “Managing temporary oversupply from renewables efficiently: electricity storage versus energy sector coupling in Germany.” International Energy Workshop, Paris. 2013.

[24] Underground cables can partly overcome this problem, but they are about 6 times more expensive than overhead lines.

[25] Szarka, Joseph, et al., eds. Learning from wind power: governance, societal and policy perspectives on sustainable energy. Palgrave Macmillan, 2012.

[26] Rodriguez, Rolando A., et al. “Transmission needs across a fully renewable european storage system.” Renewable Energy 63 (2014): 467-476.

[27] Furthermore, new transmission capacity is often required to connect renewable power plants to the rest of the grid in the first place — solar and wind farms must be co-located with the resource itself, and often these locations are far from the place where the power will be used.

[28] Becker, Sarah, et al. “Transmission grid extensions during the build-up of a fully renewable pan-European electricity supply.” Energy 64 (2014): 404-418.

[29] Zero Carbon britain: Rethinking the Future, Paul Allen et al., Centre for Alternative Technology, 2013

[30] Wave energy often correlates with wind power: if there’s no wind, there’s usually no waves.

[31] Building even larger supergrids to take advantage of even wider geographical regions, or even the whole planet, could make the need for balancing capacity largely redundant. However, this could only be done at very high costs and increased transmission losses. The transmission costs increase faster than linear with distance traveled since also the amount of peak power to be transported will grow with the surface area that is connected. [5] Practical obstacles also abound. For example, supergrids assume peace and good understanding between and within countries, as well as equal interests, while in reality some benefit much more from interconnection than others. [22]

[32] Heide, Dominik, et al. “Seasonal optimal mix of wind and solar power in a future, highly renewable Europe.” Renewable Energy 35.11 (2010): 2483-2489.

[33] Rasmussen, Morten Grud, Gorm Bruun Andresen, and Martin Greiner. “Storage and balancing synergies in a fully or highly renewable pan-european system.” Energy Policy 51 (2012): 642-651.

[34] Weitemeyer, Stefan, et al. “Integration of renewable energy sources in future power systems: the role of storage.” Renewable Energy 75 (2015): 14-20.

[35] Assessment of the European potential for pumped hydropower energy storage, Marcos Gimeno-Gutiérrez et al., European Commission, 2013 

[36] The calculation is based on the data in this article: How sustainable is stored sunlight? Kris De Decker, Low-tech Magazine, 2015.

[37] Evans, Annette, Vladimir Strezov, and Tim J. Evans. “Assessment of utility energy storage options for increased renewable energy penetration.” Renewable and Sustainable Energy Reviews 16.6 (2012): 4141-4147.

[38] Zakeri, Behnam, and Sanna Syri. “Electrical energy storage systems: A comparative life cycle cost analysis.” Renewable and Sustainable Energy Reviews 42 (2015): 569-596.

[39] Steinke, Florian, Philipp Wolfrum, and Clemens Hoffmann. “Grid vs. storage in a 100% renewable Europe.” Renewable Energy 50 (2013): 826-832.

[40] Heide, Dominik, et al. “Reduced storage and balancing needs in a fully renewable European power system with excess wind and solar power generation.” Renewable Energy 36.9 (2011): 2515-2523.