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Wednesday, 8 April 2015

The Catch-22 of Energy Storage

Robin Evans kindly pointed me to a post of fundamental importance concerning renewables. If anyone ever tells you that wind or solar is the answer to our energy problem, just steer them to this post, because they are talking out of their arse.

This post has been reprinted in its entirety from HERE from the blog “Brave New Climate”.

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The Catch-22 of Energy Storage

Pick up a research paper on battery technology, fuel cells, energy storage technologies or any of the advanced materials science used in these fields, and you will likely find somewhere in the introductory paragraphs a throwaway line about its application to the storage of renewable energy.  Energy storage makes sense for enabling a transition away from fossil fuels to more intermittent sources like wind and solar, and the storage problem presents a meaningful challenge for chemists and materials scientists… Or does it?


Guest Post by John Morgan. John is Chief Scientist at a Sydney startup developing smart grid and grid scale energy storage technologies.  He is Adjunct Professor in the School of Electrical and Computer Engineering at RMIT, holds a PhD in Physical Chemistry, and is an experienced industrial R&D leader.  You can follow John on twitter at @JohnDPMorgan. First published in Chemistry in Australia.


Several recent analyses of the inputs to our energy systems indicate that, against expectations, energy storage cannot solve the problem of intermittency of wind or solar power.  Not for reasons of technical performance, cost, or storage capacity, but for something more intractable: there is not enough surplus energy left over after construction of the generators and the storage system to power our present civilization.

The problem is analysed in an important paper by Weißbach et al.1 in terms of energy returned on energy invested, or EROEI – the ratio of the energy produced over the life of a power plant to the energy that was required to build it.  It takes energy to make a power plant – to manufacture its components, mine the fuel, and so on.  The power plant needs to make at least this much energy to break even.  A break-even powerplant has an EROEI of 1.  But such a plant would pointless, as there is no energy surplus to do the useful things we use energy for.

There is a minimum EROEI, greater than 1, that is required for an energy source to be able to run society.  An energy system must produce a surplus large enough to sustain things like food production, hospitals, and universities to train the engineers to build the plant, transport, construction, and all the elements of the civilization in which it is embedded.

For countries like the US and Germany, Weißbach et al. estimate this minimum viable EROEI to be about 7.  An energy source with lower EROEI cannot sustain a society at those levels of complexity, structured along similar lines.  If we are to transform our energy system, in particular to one without climate impacts, we need to pay close attention to the EROEI of the end result.

The EROEI values for various electrical power plants are summarized in the figure.  The fossil fuel power sources we’re most accustomed to have a high EROEI of about 30, well above the minimum requirement.  Wind power at 16, and concentrating solar power (CSP, or solar thermal power) at 19, are lower, but the energy surplus is still sufficient, in principle, to sustain a developed industrial society.  Biomass, and solar photovoltaic (at least in Germany), however, cannot.  With an EROEI of only 3.9 and 3.5 respectively, these power sources cannot support with their energy alone both their own fabrication and the societal services we use energy for in a first world country.

Energy Returned on Invested, from Weißbach et al.,1 with and without energy storage (buffering).  CCGT is closed-cycle gas turbine.  PWR is a Pressurized Water (conventional nuclear) Reactor.  Energy sources must exceed the “economic threshold”, of about 7, to yield the surplus energy required to support an OECD level society.

Energy Returned on Invested, from Weißbach et al.,1 with and without energy storage (buffering).  CCGT is closed-cycle gas turbine.  PWR is a Pressurized Water (conventional nuclear) Reactor.  Energy sources must exceed the “economic threshold”, of about 7, to yield the surplus energy required to support an OECD level society.

These EROEI values are for energy directly delivered (the “unbuffered” values in the figure).  But things change if we need to store energy.  If we were to store energy in, say, batteries, we must invest energy in mining the materials and manufacturing those batteries.  So a larger energy investment is required, and the EROEI consequently drops.

Weißbach et al. calculated the EROEIs assuming pumped hydroelectric energy storage.  This is the least energy intensive storage technology.  The energy input is mostly earthmoving and construction.  It’s a conservative basis for the calculation; chemical storage systems requiring large quantities of refined specialty materials would be much more energy intensive.  Carbajales-Dale et al.2 cite data asserting batteries are about ten times more energy intensive than pumped hydro storage.

Adding storage greatly reduces the EROEI (the “buffered” values in the figure).  Wind “firmed” with storage, with an EROEI of 3.9, joins solar PV and biomass as an unviable energy source.  CSP becomes marginal (EROEI ~9) with pumped storage, so is probably not viable with molten salt thermal storage.  The EROEI of solar PV with pumped hydro storage drops to 1.6, barely above breakeven, and with battery storage is likely in energy deficit.

This is a rather unsettling conclusion if we are looking to renewable energy for a transition to a low carbon energy system: we cannot use energy storage to overcome the variability of solar and wind power.

In particular, we can’t use batteries or chemical energy storage systems, as they would lead to much worse figures than those presented by Weißbach et al.  Hydroelectricity is the only renewable power source that is unambiguously viable.  However, hydroelectric capacity is not readily scaled up as it is restricted by suitable geography, a constraint that also applies to pumped hydro storage.

This particular study does not stand alone.  Closer to home, Springer have just published a monograph, Energy in Australia,3which contains an extended discussion of energy systems with a particular focus on EROEI analysis, and draws similar conclusions to Weißbach.  Another study by a group at Stanford2 is more optimistic, ruling out storage for most forms of solar, but suggesting it is viable for wind.  However, this viability is judged only on achieving an energy surplus (EROEI>1), not sustaining society (EROEI~7), and excludes the round trip energy losses in storage, finite cycle life, and the energetic cost of replacement of storage.  Were these included, wind would certainly fall below the sustainability threshold.

It’s important to understand the nature of this EROEI limit.  This is not a question of inadequate storage capacity – we can’t just buy or make more storage to make it work.  It’s not a question of energy losses during charge and discharge, or the number of cycles a battery can deliver.  We can’t look to new materials or technological advances, because the limits at the leading edge are those of earthmoving and civil engineering.  The problem can’t be addressed through market support mechanisms, carbon pricing, or cost reductions.  This is a fundamental energetic limit that will likely only shift if we find less materially intensive methods for dam construction.

This is not to say wind and solar have no role to play.  They can expand within a fossil fuel system, reducing overall emissions.  But without storage the amount we can integrate in the grid is greatly limited by the stochastically variable output.  We could, perhaps, build out a generation of solar and wind and storage at high penetration.  But we would be doing so on an endowment of fossil fuel net energy, which is not sustainable.  Without storage, we could smooth out variability by building redundant generator capacity over large distances.  But the additional infrastructure also forces the EROEI down to unviable levels.  The best way to think about wind and solar is that they can reduce the emissions of fossil fuels, but they cannot eliminate them.  They offer mitigation, but not replacement.

Nor is this to say there is no value in energy storage.  Battery systems in electric vehicles clearly offer potential to reduce dependency on, and emissions from, oil (provided the energy is sourced from clean power).  Rooftop solar power combined with four hours of battery storage can usefully timeshift peak electricity demand,3 reducing the need for peaking power plants and grid expansion.  And battery technology advances make possible many of our recently indispensable consumer electronics.  But what storage can’t do is enable significant replacement of fossil fuels by renewable energy.

If we want to cut emissions and replace fossil fuels, it can be done, and the solution is to be found in the upper right of the figure.  France and Ontario, two modern, advanced societies, have all but eliminated fossil fuels from their electricity grids, which they have built from the high EROEI sources of hydroelectricity and nuclear power.  Ontario in particular recently burnt its last tonne of coal, and each jurisdiction uses just a few percent of gas fired power.  This is a proven path to a decarbonized electricity grid.

But the idea that advances in energy storage will enable renewable energy is a chimera – the Catch-22 is that in overcoming intermittency by adding storage, the net energy is reduced below the level required to sustain our present civilization.

BNC Postscript

When this article was published in CiA some readers had difficulty with the idea of a minimum societal EROI.  Why can’t we make do with any positive energy surplus, if we just build more plant?  Hall4 breaks it down with the example of oil:

Think of a society dependent upon one resource: its domestic oil. If the EROI for this oil was 1.1:1 then one could pump the oil out of the ground and look at it. If it were 1.2:1 you could also refine it and look at it, 1.3:1 also distribute it to where you want to use it but all you could do is look at it. Hall et al. 2008 examined the EROI required to actually run a truck and found that if the energy included was enough to build and maintain the truck and the roads and bridges required to use it, one would need at least a 3:1 EROI at the wellhead.

Now if you wanted to put something in the truck, say some grain, and deliver it, that would require an EROI of, say, 5:1 to grow the grain. If you wanted to include depreciation on the oil field worker, the refinery worker, the truck driver and the farmer you would need an EROI of say 7 or 8:1 to support their families. If the children were to be educated you would need perhaps 9 or 10:1, have health care 12:1, have arts in their life maybe 14:1, and so on. Obviously to have a modern civilization one needs not simply surplus energy but lots of it, and that requires either a high EROI or a massive source of moderate EROI fuels.

The point is illustrated in the EROI pyramid.4 (The blue values are published values: the yellow values are increasingly speculative.)

Finally, if you are interested in pumped hydro storage, a previous Brave New Climate article by Peter Lang covers the topic in detail, and the comment stream is an amazing resource on the operational characteristics and limits of this means of energy storage.

References

  1. Weißbach et al., Energy 52 (2013) 210. Preprint available here.
  2. Carbajales-Dale et al., Energy Environ. Sci. DOI: 10.1039/c3ee42125b
  3. Graham Palmer, Energy in Australia: Peak Oil, Solar Power, and Asia’s Economic Growth; Springer 2014.
  4. Pedro Prieto and Charles Hall, Spain’s Photovoltaic Revolution, Springer 2013.

Friday, 3 April 2015

Wind threatens security of Scotland’s power supplies

  • NOTE: I have reproduced this article in its entirety from Scottish Energy News. It is of fundamental importance to the debate about wind energy in Scotland

 

Dash for Scottish renewables is creating an ‘economic cuckoo’ which threatens security of Scotland’s power supplies

Scientific Alliance Jack Ponton power chart graphic Feb 2015

By Prof. JACK PONTON and JOHN WILLIAMS

By 2020, Scotland will be generating a huge surplus of heavily subsidised renewable electricity that it cannot use, sell or store.

The cost implications of producing this surplus will run into billions of pounds, and experts are now demanding that the Scottish Government confirms how it will deal with this huge green surplus – just as Scotland’s cheapest source of electricity – Longannet coal-fired power station, faces closure.

This crisis has been widely predicted. It is entirely a consequence of reducing Scotland’s ability to balance electricity demand by rapidly increasing the variable supply from wind generated power. Wind power is intermittent, it is not secure, and it cannot be stored in the quantities required.

Given the Scottish Government’s renewable energy policy, the crisis is, ironically, a double one of shortages and (very costly) surpluses. 

At times, there will be a shortage of supply that could lead to power cuts, unless power is imported from England (in 2014, Scotland imported electricity from England on 162 days ).

At others, there will be an excess of production that cannot be used but will have to be paid for by consumers or taxpayers. 

In 2010, Scotland had a secure and balanced electricity supply.

There were two nuclear, two coal and one gas-fired power stations, a suite of hydro electric stations providing dispatchable, ie available on demand, power of about 8.4GW. There was a nominal wind capacity of just over 2.5GW.  The red line shows approximate peak demand of 6GW. Scotland’s electricity needs were safe and secure.

Even the loss of a major power station for maintenance or emergency repairs would not have required import of power from south of the border.

By 2015, a major transformation has taken place: the system is still secure but perhaps only just: the lights are still on – but it is costing more.

Cockenzie coal-fired station had been closed. Although Peterhead gas power station now has a reduced capacity there is still 6.7GW of dispatchable power, comfortably in excess of peak demand but susceptible to a nuclear outage.

The transformation has been in the expansion of wind to 7.1GW nominal capacity. Flexible dispatchable power, ie coal, gas and hydro, totals 4.7GW. (Nuclear cannot be conveniently turned on and off so, although it is dispatchable, it is not flexible.)

When the wind blows hard, there is still conventionally generated power to take off line, and the capacity to export up to 3.3GW via interconnection to England.  In 2010, there was 8.6GW of generating capacity; today there is a theoretical 13.9 GW capacity.

However, potential problems are beginning to emerge. Minimum wind load factors of less than 5% can occur so that wind generation can be lower than 0.35GW. For instance, at 2.30pm on 19 January 2015, UK wind load factor was 2.2%) If low wind generation coincides with a reduction in dispatchable generation, power has to be imported. Indeed, imports of power have been required on 162 days in the last three years.

Conversely, high wind speeds resulting in load factors of more than 80%, have at times of low demand required output reductions from Longannet – now the only major Scottish energy resource that can be turned down relatively easily. This increases the cost of operating the plant, and along with other factors such as carbon taxes has brought its future into question. 

Wind turbines may also need to be shut down to avoid overloading the grid, in which case their operators receive ‘constraint payments’ well in excess of their lost revenue.

What will be the position in 2020? Will Scotland benefit from the green electricity ‘bonanza’?

Or will the renewables’ surplus become an unbearable cost to the Scottish economy?

The 2020 configuration assumes that already consented wind farms totaling 8.68GW will have been built, exceeding the Scottish Government’s ‘100% renewable generation’ by nearly 20%.

It is likely that Longannet will have become unprofitable and will close down.  The two Scottish nuclear plants (owned by the French nationalised operator, EDF) should still be operational.There will be 4.4GW of dispatchable power, 1.6GW below the safe threshold. Although the 15.8GW of wind capacity operating above 10% capacity should cover that for most of the time, when load factors fall below this significant shortfalls will occur.

These will have to be met by importing dispatchable power from England, assuming that adequate capacity does in fact exist there. The 2.07GW of nuclear power should provide reliable base load regardless of the weather.

However, when one of these nuclear plants is off line for scheduled or unscheduled maintenance, Scotland’s security of supply will become entirely dependent upon imports.

This is one aspect of the problem that an unbalanced electricity supply will produce. The other, ironically, is what to do with a surplus of power.

Peak demand is at around 6pm on a week day in winter, and minimum demand is always at night at the weekend in summer. This minimum is about 38% of peak, roughly 2.3GW.  Night-time summer demand for electricity would be almost met by the two Scottish nuclear power stations, neither of which can be turned down easily.

With approximately 15GW of installed wind capacity operating at a realistic maximum of 80% load factor, wind generation could peak at 12GW, nearly all of it surplus to Scotland’s needs. 

Since producers get paid their elevated guaranteed price regardless of whether or not there is demand for the power, this represents a substantial cost to consumers – unless the surplus can be used effectively.

Interconnection capacity to England is to be increased to 6GW (at great cost), but this is only about half of the possible excess. 

The current Scottish Government plan is evidently for Scotland to somehow profit from exporting its surpluses. However, when the wind blows hard here it is usually also blowing hard in England and Europe, and consequently spot power prices hit rock bottom.

As it is extremely unlikely that Scotland’s neighbours would be prepared to pay the premium prices which the wind generators have been guaranteed, the cost of the difference will fall on local consumers.

Renewable energy enthusiasts talk about storing electricity but currently the only available means of large scale storage is pumped hydro.

There are two such schemes in Scotland and two in Wales. These have a storage capacity of only 27GWh, just over three quarters of an hour of UK average demand. The new Coire Glas scheme, approved but awaiting a final investment decision, is the only addition currently proposed. This would have a storage capacity of 30GWh.  Average daily electricity consumption in Scotland is about 100GWh. 

Peak excess production over a very windy 24 hours could be nearly 300GWh but Coire Glas could only handle 0.6GW. To absorb 12GW of excess generation would require at least 20 schemes of this size – but the geography and hydrology of such projects is so restrictive that it is not clear if there are any further suitable sites in the country, let alone 20.

How long will it be before the Scottish Government finally acknowledges the truth: that the blind dash for wind is pointless, it will be hugely expensive, and that degrading even more of Scotland’s landscapes will be futile?

Not only is there no need for any more wind in Scotland’s energy mix but the country’s lack of conventional supply will ensure long-term reliance on the UK and Europe for the safety of Scotland’s electricity supply.

Jack Ponton, FREng

John Williams is Chairman of the Borders Network of Conservation Groups.

Copyright © Energy News Scotland Ltd

Tuesday, 31 March 2015

Caledonia, you’re calling me…

You’ll all have seen the wind farm maps I’ve posted on here. They have shown the proposed devastation of the wild land of the Monadh Liath and the land to the west of Loch Ness

Malcolm Kirk has produced an excellent video that illustrates the devastation far better than any map.

Note: Public Health Warning! There follows fifty seconds of accordion music, but be brave! It’s over quickly and is followed straight after by some hauntingly beautiful music.

CLICK ON ‘FULL SCREEN’ TO SEE IT AT ITS BEST.

Many thanks to Malcolm Kirk. Excellent work, Sir!

You’ll be delighted to know that a petition to the Scottish Government has been started:

  • Calling on the Scottish Parliament to urge the Scottish Government to take steps to designate the Loch Ness and Great Glen as a National Scenic Area; to recommend a priority application is made to UNESCO for the area to be afforded World Heritage protection; and to take appropriate steps to discourage further wind turbine developments and support the restoration of sites damaged by wind turbines.

You can find and then sign this petition by clicking

HERE

Please, please help by signing it. It takes but moments to do this, but it could save this wonderful landscape for ever.

Thank you. You can find out more by visiting SaveLochNess.com

Tuesday, 24 March 2015

Barney’s Long Walk

All the dogs I’ve ever known have had an extraordinary sense of direction; they always knew the way back home and they can always find your hidden breakfast pasties. So quite why Barney, the beautiful Flat Coat Retriever, needs Bob and Jos Mahon to tag along on his walk from Land’s End to John o’ Groats I’ll never know.

But that is what’s happening and it’s happening in very short order!

This Friday, the 27th March, Barney and his two hangers-on are taking the first few steps from Land’s End. Barney is walking for Guide Dogs for the Blind but he is handing over the blogging duties to Bob.

You will be able to find all about it and follow this wonderful walk by clicking HERE. You can also find a permanent link in my “Better Places to Visit” column on the RHS of this blog.