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

Matching supply to demand at all times makes renewable power production a complex, slow, expensive and unsustainable undertaking.

image sailboat

Image: Eye of the 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. 345 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. 67

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.

average cloud cover 2002-2015

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. 8910

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. 89

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 121314 In practice, however, wind turbines can operate between 0 and 100% of their maximum power at any moment.

image solar wind output

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. 1617

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.

every power plant in the usa

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. 212223

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 of europe

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. 212627

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. 2025 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). 293031

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.

live windmap 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. 323334

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. 333940

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.

image windmiill belgium

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)

Comments

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Angus

Fantastic article Kris, thanks.

One idea that is not explored is that of combining approaches to energy. For example, if regions have some storage, and some ability to transmit energy to other regions, and some ability to perform demand management, then there will be (I think!) far fewer days of shortfall.

The reason is that the interconnectors can then be sized to average (demand-reduced) consumption, rather than peak consumption, and storage can be sized for a shorter period because power can be brought in from further away at the reduced rate.

Hope that makes sense, Angus

Marcos Belançon

I would like to add something to the discussion. It is not necessary to think about the storage, because we don’t have a technology for photovoltaics for example that could be scaled up to our needs. The back contact of common PV is made of silver. 25kg per MWp. This means that today we already use 10% of the silver extracted every year to fabricate photovoltaics. And if we keep the actual production rate, in about 20 years the installed capacity will not grow anymore. We will be replacing the older ones. Wind is not so different.

Hilton Dier

Part of the problem is that we (the U.S.) waste so much energy. The average European uses about 60% of the energy of the average American. With real effort we could cut our usage in half.

Hydroelectric is part of the solution. Hydro output varies over hours and days rather than minutes and is much more predictable. It provides about 6% of our present production. Make that 12% if we stopped wasting so much.

The latest and most promising storage method is actually quite simple. A company called ARES is building a MW scale storage system that is an electrically powered train loaded with stone on a track that goes up the side of a mountain. It’s all early 20th century technology, aside from the control system. No exotic batteries necessary. They claim an 80% round trip efficiency, which is roughly that of a battery.

But yes, a demand side strategy is the best. We should all have electric meters on the inside of our houses, giving us our present and historical use, present cost of electricity, and predicted future cost. That would allow us to make informed decisions about use.

kris de decker

Correction. I deleted the following sentence because it is wrong: “Energy storage also assumes an oversizing of the renewable power capacity, otherwise there would never be a surplus of electricity that could be stored for later use.”

Keith H. Burgess

I totally disagree. This is more to do with the ability to store the power than producing it, & it is about how much people use & think they need to use. People need to get a grip. We have been off grid for over 40 years. We have a relatively small solar power set up. We have a 24 volt battery bank converted to 240 volt AC. The main item we power is or fridge freezer, & we lived for over 20 years without any electricity at all. Keith.

kris de decker

@ Keith

The article is not talking about off-the-grid systems. In fact, an off-the-grid system is a good example of a system that adjusts demand to supply to a certain degree. Battery storage is costly so it’s usually limited to a few days of reserve at most. During longer low power periods, off-the-gridders adjust demand to supply. They have no other choice.

zmau

You missed one important concept in the system. Prices. Price is very strong piece of information which helps to adjust demand to supply.

So, when supply is low, prices should go up (that’s exactly what happens on all free markets all over the world), and people will spend less. So there will probably be no need for real restrictions.

Also, overall higher energy price will surely reduce overall consumption, and that’s really not a problem, because a lot of cheap energy is just wasted anyway.

John Weber

Many materials used in our industrial world require energy from mining to manufacturing for processing and transportation. The energy for some of these products is in the form of high temperatures – 2000° F (nearly 1100°C). These processes run 24/7 365 days.

There are proposals that solar and wind energy collecting devices can provide the energy to maintain the industrial world. To look at this possibility, solar electric panels, wind turbines and concentrated solar installations in the form of parabolic trough collectors (PTC) have been assessed.

The energy requirements in 2010 for the following essential components of our industrial world are provided: steel, aluminum, chromium, copper, manganese, cement and glass. This energy would be mining, processing and transporting to name some. Other important components of the industrialized world such as nickel and cobalt are not considered because they are part of the high temperature processing of other ore metals.

The kWh output and area required for installations of solar electric panels, wind turbines and PTC has been researched. This then is divided into the energy (exajoules converted to kWh) required for global production of each material in 2010.

NEEDED 121,214.45 Square Miles of Solar Electric Collectors 257,472 square miles and 2,807,276 Wind Turbines 77183.4 square miles of PTCs There are many other critical components of our global industrialized world that require industrial heat (lead, silver, tin, food processing) that are right at the top heating limit of solar devices. They must also be included in an all “renewable” future. If only half of important materials were provided, what would our world be like?

IN AN INDUSTRIALIZED SOCIETY, IT FALLS TO THE PROMOTERS OF A FUTURE FORRENEWABLEENERGY TO SHOW HOW THESE ESSENTIAL MATERIALS AND SO MUCH ELSE CAN BE PROVIDED.

See maps, images and calculations at: http://sunweber.blogspot.com/2017/08/heat-for-tomorrow-many-materials-used.html

John Weber

ORE GRADES This paper quantifies, on a global level, the relationship between ore grade and energy intensity. With the case of copper, the study has shown that the average copper ore grade is decreasing over time, while the energy consumption and the total material production in the mine increases. Analyzing only copper mines, the average ore grade has decreased approximately by 25% in just ten years. In that same period, the total energy consumption has increased at a higher rate than production (46% energy increase over 30% production increase). Decreasing Ore Grades in Global Metallic Mining: A Theoretical Issue or a Global Reality? http://www.mdpi.com/2079-9276/5/4/36

John Weber

There are multiple questions that a realistic assessment of the future of these devices requires. Each of these questions asks about the future of “renewable” devices.

First and foremost: What do we need the energy for? Not, why - what do we want this electricity for. This must be one of the mantras for survival now and tomorrow.

When it comes time to replace these devices: Where will the energy and resources come from?

To replace components of these systems: Where will the energy and resources come from?

As we need to manufacture the tools and toys we want the electricity for: Where will the energy and resources come from?

Will we sequester/store the energy to provide for these future needs? How will we do that?

OR

Will dedicated devices be built simply to facilitate replacement of devices and their auxiliary parts (inverters, controllers, fans)?

Who will manage these dedicated devices?

What will stop society from using this sequestered energy?

Will the need to protect this sequestered energy create an even more constrained and draconian social environment?

How will this electricity be equally shared globally compared to the present unequal energy availability?

How will we mine and transport all these raw resources: the basic material for fabrication, the actual devices, the various auxiliary equipment, the tools and the toys? More at: http://sunweber.blogspot.com/2016/11/the-energy-in-our-future.html

Jan Steinman

It’s about time someone said this!

While the politicians continue to recite, “Our life-style is not negotiable.”

Darkest Yorkshire

I’m becoming increasingly concerned about the capacity of renewables but this post misses a few things that may make the future less bleak.

Demand response is widely used in industry and is growing. Companies get paid a lot of money to crank up operations when there’s too much power in the system and to turn off consumption and fire up their backup generators when there’s too little. https://www.flexitricity.com/en-gb/

Those sorts of generators can back up renewables and can themselves be fueled by renewable or industrial waste gasses that have to be got rid of somehow. It doesn’t have to be a single-use fossil fuel infrastructure. https://www.clarke-energy.com/news/ (see particularly ‘Gas Types’ and ‘Power’ sections.

None of your sources on energy storage included the best one - liquid air energy storage. http://www.liquidair.org.uk/about-liquid-air It piggybacks on the industrial gas business so needs far less new technology and infrastructure. It also has several uses. http://dearman.co.uk/ In addition to the listed uses, another option is to separate the air into oxygen and nitrogen. This uses more energy but the nitrogen can then be used for nearly everything liquid air can, except where there is a suffocation hazard. The oxygen has many uses but one of the most interesting is to run industrial furnaces in oxyfuel mode (particularly flameless), which results in fuel savings and a better end product. http://www.praxair.com/industries/metal-production/oxygen-enhanced-combustion http://www.lindegaspr.com/internet.lg.lg.pri/en/images/Flameless%20oxyfuel%20for%20more%20production%20CO2%20NOx%20SuE%200708811_10828.pdf

Also, I love how the Zakeri article lists the options to decouple pumped hydro storage from geographical restraints and they get progressively weirder - “water filled balloon under pressure caused by sand”. That sounds like an insane nineteenth century patent application from the enthusiastic heights of the age of invention. Or some world-changing project the Bolsheviks planned but never quite got round to. :)

Keith Pickering

You’ve hit the nail on the head here in many ways. It’s not just energy, it’s EROI as you have correctly shown; and VRE (solar and wind) are marginal on their own, but require much more energy input to make them viable at high grid penetrations. A recent paper by Weissbach et al. has broken this down more explicitly, looking at both EROI with and without required storage, and the economic limits under each. The paper assumes pumped hydro for storage, which is still far and away the cheapest storage medium, although it is geographically limited. See: http://homepages.uc.edu/~becktl/shaka-eroi.pdf

This is why many of us (although perhaps not on this site) see substantial increases in nuclear power as the last-best hope of building a carbon-free civilization.

Andrew Streit

I believe that this article is the precursor to the future, one that as the generation who ‘tamed nature’ many will find abhorrent. Fossil fuels allowed us to ignore everything we learned in the past millennia and build the same house in Minnesota as Nevada or New England. Burn baby burn has been our mantra and one that purely on the engineering feat I am proud of. We proved we could do something, now we have to do it smarter and with centuries in mind not fiscal quarters or shareholder returns but survival. At some point any article which says “expensive” I am going to ignore. If fossil fuels will eventually run out, (a common theme if you believe the earth is round) then investment in fossil fuel replacement is infinitely cheaper than re-investing in a dying industry. Philosophically, pragmatically and sustainably a society based solely on profit is fading so how do we transition to an economy that is built on scientific principles and societal preservation and expansion?

Tilman Keding

As already partly mentioned in comments above, I’m missing other types of renewable energy in the article… hydropower and biogas especially. These are more stable and can, depending on the type of plant, be used for energy storage.

The energy market (in europe) is already partly regulating itself today by adapting prices to demand and availability of energy, up to negative prices, when there is too much power available. Demand side management, where industries with high energy demand can give the energy supplier the option to switch off their non time-critical machinery when little power is available, is already in use today (in Germany for industrial power use of >50MW).

Depending heavily on the the available resources (wind, sun, water, biomass), studies show that 100% renewable energy is definitely possible without big increas in storage, in Germany for example if the grid connections between areas of high production and high demand are improved: https://www.energiesystemtechnik.iwes.fraunhofer.de/content/dam/iwes-neu/energiesystemtechnik/de/Dokumente/Studien-Reports/2014_Roadmap-Speicher-Langfassung.pdf

Still, to not turn the whole landscape in energy production spaces, it would be great to not only adapt energy demand, but also reduce it.

George Smiley

Some of the calculations look specious to me, especially the manufacturing ENERGY payback times for renewable infrastructure. Fifteen years for a solar panel? A home 300 watt panel costs about $300 and it will take 7-15 years to pay the capex back including its share of the whole system; total manufacturing COST, installation, inverter, wiring, retail mark-ups and EVERYTHING. I suggest the actual energy component consumed in producing this item is negligible. I can unmake it by melting it to a primordial white hot blob in an inefficient little home-made gas powered fan-forced furnace with $25 worth of LP gas and most of the heat just blows on past. I won’t bother looking up the kilojoules from that 20 kg. of propane, but I suggest a week’s panel output, say 1.5 KWh per day stored in batteries would outdo the LP and vaporize the panel using a plasma cutter for about $1 worth of energy. Which also suggests that high temperatures from renewables may be difficult in terms of steady baseload power as required by a continuously operating smelter but it is in no way out of the question.

Brian Mallalieu

An interesting & obviously well-thought through article, but two other points that could be considered:

  1. Macro-supergrids (i.e. worldwide)could utilise the fact that the sun does not ‘disappear’ for 12+ hours, but merely transfers to the opposite hemisphere, and even winds also vary in intensity & time across the world.

  2. Other renewables (unmentioned) are available e.g. biomass, AD, geothermal etc. which can contribute. Posted by: Brian Mallalieu | September 18, 2017 at 03:36 PM

J.C.

The answer is nuclear. We have “magic” available to us, but are still operating based on unjustified fear.

John McGinnis

A thorium salt reactor has just been restarted. Thorium reactors could provide the baseload metrics needed by society.

rdp

Kris says: …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.

At least one utility company, Arizona Public Service (APS) has proposed “a ‘reverse demand response’ pilot that aims to address negative pricing in the middle of the day by shifting non-residential load to times when renewable energy abundant.” See http://www.utilitydive.com/news/aps-proposes-reverse-demand-response-in-new-demand-side-management-plan/504632/

This makes great economic sense for both utilities (deferred build-out) and business (cheap energy), and I hope other utilities follow suit.

kris de decker

Discussions at Resilience & Treehugger

http://www.resilience.org/stories/2017-09-14/how-not-to-run-a-modern-society-on-solar-and-wind-power-alone/

https://www.treehugger.com/green-architecture/why-wind-and-solar-wont-save-us.html

deadrody

Adjusting demand….. LOL!!! You do realize that there are plenty of people, damn near 50%, if not more (probably a lot more_, including hardcore environmentalists that - if told, well, you can only run half the appliances, lights, etc. that you want, so you can have true 100% renewable energy - have no real interest at all.

People who realize 100% renewable energy as well as “global warming” are pipe dreams are really not interested in curtailing their electricity usage to support a mythical “100% renewable energy” grid.

I mean, I appreciate the time taken to illuminate just how unrealistic “100% renewable energy” really is. But at what point do we start to realize, there is no money for ANY of that. No a super grid, not 3-5 times the renewable generation capacity, not any kind of scale-able energy storage. None of it. Like I said - pipe dream.

William Thorpe

@John Weber - there has been some good work done on using solar furnaces for industrial heat, smelting etc. Some interesting examples even on this website. They can easily get the temperatures required for most processes (there is some limit, but it’s well above 3,000 C).

The issue of course is that most industry currently is situated in countries without so much solar resource. It might be that in a solar powered economy, industrial processing will need to move to sunnier regions in order to directly access the availability of solar heat. That could have interesting geopolitical consequences.

kris de decker

@ J.C & John McGinnis (#18, #19)

Concerning nuclear, I’m prepared to make a compromise. Lower the electricity use to the level of what the already operating atomic plants produce and I agree. However, if you plan to build new power plants to match supply to demand at all times, you’re running into the same problems: it takes too much resources, money and time to go nuclear at such a scale. And atomic plants are (more or less) fine as long as there is peace, and as long as there’s money to maintain them.

@ Brian (#17), Tilman (#15), Hilton (#3)

The choice for solar and wind energy only is based on the fact that these are — by far — the renewable energy sources with the largest potential. Hydropower and biomass could only be scaled up with devastating consequences. You could turn every mountain range into pumped storage power plants, but that means flooding nature and villages.

Counting on biomass is of course a great risk for deforestation. Wind and especially solar energy (the mother of almost all other renewable energy sources) are much less problematic in this sense. We have to be careful not to harvest too much wind (climate change!) but we are still far from that. And for solar energy, there are no such issues at all.

If we’re going to run society on renewable energy, sun and wind will be our best chance.

kris de decker

@ George (#16)

I’m not sure what you mean. I based my calculation for solar PV panels on an energy payback time of 2 to 4 years, depending on location. However, these numbers imply that all electricity produced by a solar panel is effectively used. From the moment you start curtailing solar energy, it will take more time before a solar panel generates the energy it took to produce it.

@ Brian (#17)

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, that’s right. However, this runs into the same problems and 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. 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. See reference 22.

@ zmau (#7)

Using pricing to regulate energy demand is not that easy. First of all, there’s many people, even in the industrialised world, who can’t afford to pay their energy bills. Second, to make it work, price differences have to be quite large, considering the relatively low price-elasticity of electricity demand. If you would have large price peaks that reflect the variable supply of renewable energy, leaving the refrigerator on when you leave the house on a windless night might ruin you. Maybe it’s a good idea for industry: large factories pay much lower electricity prices than households.

kris de decker

@ Darkest Yorkshire (#12)

I looked into this “Flexitry” company you mentioned. If I understand the concept well, it’s totally the opposite of what I mean. They use backup generation capacity from factories (often diesel generators) to match supply to demand in periods of low renewable power generation.

They write that they make it “possible for a much larger volume of variable renewable generation to be absorbed”, but their approach doesn’t lower the energy demand in times of short supply. It basically provides a balancing capacity of fossil fuel power plants.

Darkest Yorkshire

Flexitricity’s website doesn’t do as good a job of explaining what they do as it used to. I think they emphasise on-demand generation because more businesses are interested in that beecause it doesn’t interrupt production and gets another use out of the generators they already have. But both the Frequency Response and STOR services can work either by turning on generation or turning down demand. Footroom turns up consumption to absorb renewable surpleses.

Most of the current generators run on diesel but gas engines could run on natural gas, biomethane, syngas or a few industrial waste gases. In my previous comment on oxyfuel for industry I didn’t mention that it also allows carbon monoxide to burn faster and so be used not just in low temperature boilers but in high temperature furnaces and gas engines as well. So syngas becomes more useful when separated into hydrogen and carbon monoxide.

But then there is the problem of what to use renewable gases for, as even at maximum production there isn’t enough to go round. The choices are domestic heating, on-demand generation, transport fuel or industrial use (biomethane can do any of them, syngas is poisonous so is more limited). And the potential in any one of these areas is limited. Claims for domestic heating vary from 50-100% and for electricity 1% of demand (but available whenever needed). I don’t know if anyone has tried to calculate how much industrial gas demand can be met sustainably.

The transport potential I read was about 15%, so enough to take a decent chunk out of bus and truck consumption. The potential of using liquid methane as a transport fuel has increased recently along with the development of the Dearman engine. It was realised that it releases energy in two stages - when it expands from liquid to gas and when the gas burns. If an engine is designed to take advantage of both stages, liquid methane’s energy density rises considerably.

Even with these options gases are as serious a renewable crunch point as electricity and liquid fuels.

I’ve always been against nuclear but have been looking at the claims for fast neutron reactors. They can be fuelled on anything - uranium, plutonium, thorium, nuclear waste - and can stretch supplies for thousands of years. They have liquid cores so can’t melt down. The fuel is reprocessed in the same building with good fuel put back in the reactor, medical and industrial isotopes removed, and what is left is only radioactive for 300 years instead of 80,000+. These designs seem to solve an awful lot of problems, so what are the arguments against them?

Antoine BL

Fantastic article as always.

However it talks of the future of the electricity grid only and not of the gas network which provides a big part of our energy consumption.

One of the solutions that was not explored here lies in the complementarity between these two networks. Negawatt is a french association which works on a 100% renewable scenario for 2050 in France, including all uses. Their moto is soberness, then efficiency, then renewables energy, I think this is close to your approach.

One of their major tricks to achieve 100% renewables is to convert the electricity into gas when there is oversupply. This way, they can use the existing gas network which is extensive and benefit from the 150 TWh of stockage already existing in France. Then they use it for heating and transportation and as a last resort to produce again electricity via cogeneration. This approach is quickly described in english in the summary of the last report https://negawatt.org/IMG/pdf/negawatt-scenario-2017-2050_english-summary.pdf and better detailed in the 2011 report : https://negawatt.org/IMG/pdf/150622_negawatt-executivesummary.pdf

I think this solution may be additional to the other solutions described in the article and besides on the website (reduction and flexibility of demand), and I am really looking forward to the next article.

Norman Pagett

the ultimate omission is that our industrial/commercial infrastructure functions on the production and sale of ”stuff” Unfortunately you can’t make ‘stuff” using electricity.

Electricity is useless until it is used to power machinery, and you cant make machinery without the input of oil coal or gas. Even wiring needs plastic as insulation, (made from oil)

This explains our predicament in greater detail

https://extranewsfeed.com/an-infinity-of-futility-819630ea935f

Fusion

Has no one considered the impact of removing “global” scale energy from the atmosphere or the oceans? If you think climate change is a problem now, you have no imagination.

trylogic

“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.”

“The energy that’s saved on fuel is spent on the manufacturing, installation and interconnection of millions of solar panels and wind turbines.”

…because the energy payback times of solar panels and wind turbines would increase six- or ten-fold.”

The statements above are incorrect for the following reasons :

If the energy needed for the manufacturing, installation and interconnection of millions of solar panels and wind turbines is CREATED by SOLAR PANELS and WIND TURBINES the payback time is ZERO!

For example :

A large industrial building has the roof covered with solar panels providing enough energy to manufacture the solar panels below.

Only solar and wind power is used for the manufacturing of components, installations and connections.

QED!

Wim Turkenburg

One question is whether we should focus on 100% renewables or even 100% solar and wind, or on 100% reduction of CO2 emission from the energy sector within the period 2017-2050. I think to focus should be on emission reduction.

Then a question is: what is the optimum contribution of intermittent renewables and what technologies and approaches could compliment the intermittency of solar and wind in an optimal manner.

We did such a study focused on the electricity sector in Europe in the year 2050 using an hourly simulation model (PLEXOS) and assuming a need for 96% CO2 emission reduction. We simulated the power system with 40%, 60% and 80% penetration of renewables and we assessed 5 options to compliment intermittent renewables to achieve both a reliable supply and the lowest total system costs.

It was found that total system costs can be reduced by a combination of: (1) Demand response (DR); (2) natural gas-fired power plants with and without Carbon Capture and Storage (CCS); (3) increased interconnection capacity; (4) curtailment. It was found that electricity storage increases total system costs in all scenarios.

The charging costs and investment costs make storage relatively expensive, even projecting cost reductions of 40% for Compressed Air Energy Storage (CAES) and 70% for batteries compared to 2012.

For details see: A.S. Brouwer et al., ‘Least-cost options for integrating intermittent renewables in low-carbon power systems’, Applied Energy 161 (2016) 48-74.

drs

Part of the problem is that we (the U.S.) waste so much energy. The average European uses about 60% of the energy of the average American”

That’s somewhat misleading. Europeans generally enjoy a nicer climate than most Americans, either generally cooler (but not too cold) or warm but dry. Much of the US lives in climate ranging from hot and humid to sub-freezing temperatures. This will naturally lead to more energy use in heating and A/C. And if Americans relocated to the friendlier West Coast, we’d have to provide them with water and housing.

We Americans could use a lot less energy with better housing and with denser cities (walkable, electrified public transit), though of course building new buildings takes energy of its own. European gas taxes have fostered fewer and more efficient cars. But there is a basic climate difference, too.

drs

Has no one considered the impact of removing “global” scale energy from the atmosphere or the oceans? If you think climate change is a problem now, you have no imagination.”

Rather, we’ve looked at the numbers. Human power use is a tiny fraction of surface isolation, like one part in a thousand.

It’s conceivable that mass use of wind would make more of a difference to wind patterns, but being worse than global warming is a high bar to clear.

John Puma

The opening sentence: “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.”

OK, correct for what is says explicitly.

BUT the unmentioned follow-up is that current global electricity demand (usage) is only a fraction of the current global energy demand (usage).

So the problem is: can current non-electrical energy usage be converted to electrical substitutes (think airliners) or can “modern” consume-more-tomorrow-than-today society be convinced to use considerably less energy?

Noel Cass

Another great article, Kris.

Growth in the developed economies might be coming to an end. This might be due to diminishing marginal returns (Bonaiuti, 2014), the exhaustion of technological innovations (Gordon 2012) or limits in creating effective demand and investment outlets for capital accumulating at a compound interest rate (Harvey 2010). Natural resources also pose a limit to growth. Economic growth degrades high-order (low entropy) energy stocks, turning them into low-order (high entropy) heat and emissions. Peak oil, peaks in the extraction rates of essential stocks such as phosphorous, and climate change from carbon emissions, may already restrict growth. The new stocks that substitute oil are also exhaustible, such as shale gas, and often dirtier, such as coal or tar sands, accelerating climate change. Renewable energy from solar or wind flows is cleaner, but renewable sources yield lower energy surpluses (energy returns to energy investment – EROI), given the existing technology, compared to fossil fuels. A lot of conventional energy will have to be expended in the transition to renewables. A solar civilization can only support smaller economies, given the low EROI of renewable energies compared to fossil fuels. A transition to renewables will inevitably be a degrowth transition.” - Introduction: Degrowth, A Vocabulary for a New Era. Giorgos Kallis, Federico Demaria and Giacomo D’Alisa.

Chris Williams

Great article, thanks. Has anyone modeled the impact of using biofuels solely for load balancing, rather than as now for base load? The UK, for example, can provide about 40-50% of capacity with gas power stations. These exist already. Can we invest in storage for gas, and then fill that gradually with biogas? This might be difficult: on the other hand, we’ve also got the old coal power stations. These can be converted to run on woodchips (Drax has been), and I think that they can give us about 30% of current capacity. Clearly, there are massive problems with using wood chips at the same level that we now use coal — but what if we shifted the market so that we were only burning biofuels in order to meet demand peaks: the numbers above imply that this would be equivalent to about one sixth (60 days) of the current load. Rather than using Drax every day to generate 4% of the UK’s power from woodchips sourced from North America, we could leave it switched off most of the time, surrounded by large stockpiles of woodchips sourced from the UK.

So, whereas five years ago I was thinking that the best thing to do with the UK’s coal plants was to blow them up, now I want them left intact for future clean use. And if Carbon Capture and Storage technology ever arrives, we can install it there to make them CO2-negative.

I agree that making demand more variable is very important. It lowers the bar. But I think that a combination of some oversupply by renewables, legacy nuclear (itself suffering from massive flexibility issues!), interconnectors, battery storage (lithium-ion is only one technology—vanadium flow works also) and biofuels in legacy fossil fuel plants will all help us to clear that bar.

Base load’ didn’t use to exist — electricity companies created it to have people to sell their product to. See the ‘Electrical Association for Women’ as an example of a ‘consumer’ group created to persuade UK consumers to buy electrical appliances (and use them during the day), and funded by the electricity supply industry.

Doug

A DC power grid would generate far greater losses than AC. Is that a typo?

Joshua Spodek

This post helped inspire a podcast episode I did on resilience, “Why Unplug?” https://shows.acast.com/leadership-and-the-environment/episodes/426-why-unpug based on my changing my behavior to see what was possible living with less regular power.


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  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. 

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  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. 

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

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  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. 

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  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] 

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