When I asked my questions, I was told that I did not know how the grid works. This provided to be a less than satisfactory answer, because the way the grid worked required the burning of a lot of fossil fuels, that produced far too much CO2. When I pointed this out, I got two sorts of answers:
* A renewable dominated grid can be made reliable by creating transmission links between lots of renewable sources.A careful examination of both answers will reveal that they are both seriously flawed. Ten Trainer points out a electrical supply problems wich no ammount of renewable transmission linking will solve.
* A renewawables dominated grid will depend on a lot of energy storage.
The greatest challenges set by variability of wind and sun concerns the gaps of several days in a row when there might be no sun or wind energy available across large regions, including continents. Following are cases from the many studies documenting the magnitude and seriousness of these common events.Thus day long gaps in renewable energy supply, even when drawn from a large area pose significant problems. In order to supply electricity on dark winter days when little wind is blowing, many extra wind generators must be drawn on. Thus a renewables based post-carbon grid, must include many extra wind generators inorder to provide a reliable electrical supply. Each of those generators costs money to build, and link to the grid. So the cost of the post carbon all renewables grid must include the redundant generation capacity, required to mke the grid reliable. As it turned out the cost of building redundant wind and solar generating capacity made the cost of wind and/or solar based generating systems far more expensive than nuclear systems, and thus far less likely to be built. None of the renewabvle advocates I questioned, responded to the concern related to redundency costs.
· Lenzen’s review (2009) includes impressive graphs from Oswald et al, (2008) and Soder et al., (2007). The first shows wind energy availability over the whole of Ireland, UK and Germany for the first 300 hours of 2006, i,.e., in mid winter, the best time of the year for wind energy. For half this time there was almost no wind input in any of these countries, with capacity factors averaging around 6%. For about 120 continuous hours UK capacity averaged about 3%. During this period UK electricity demand reached its peak high for the year, at a point in time when wind input was zero.
· Soder et al. provide a similar plot for West Denmark in mid winter, again one of the best wind regions in the inhabited world. For two periods, one of 2 and one of about 2.5 days, there was no wind input at all, and in all there were about 8 days with almost no contribution from wind energy.
· Lenzen’s third plot is for the whole of Germany, again showing hardly any wind input for several days in a row. (See also E.On Netz, 2004.)
o Davey Coppin (2003) make the same point for Australia with its much more favourable wind resources than Germany, for instance indicating that for 20% of the time a wind system integrated across 1500 km from Adelaide to Brisbane would be operating at under 8% of peak capacity.
· Mackay (2008, p. 189) reports data from Ireland between Oct. 2006 and Feb. 2007, showing a 15 day lull over the whole country. For 5 days output from wind turbines was 5% of capacity and fell to 2% on one day.
· Similar documentation on lengthy gaps is given by Coelingh, 1999, Fig. 7, Sharman 2005. At times the Danish wind system contributes almost no electricity.
But what about energy storage? A recent post on The Oil Drum, titled A Nation Size Battery lays out some of the problems of the storage approach. The posts author Tom Murphy, an associate professor of physics at the University of California, San Diego, states:
solar and wind suffer a serious problem in that they are not always available. There are windless days, there are sunless nights, and worst of all, there are windless nights. Obviously, this calls for energy storage, allowing us to collect the energy when we can, and use it when we want.Dr. Murphy is obviously not anti-renewables, but he is a rare pro-renewables realist who has analyzed the problems and is willing to go on record about what is the score:
Small-scale off-grid solar and wind installations have been doing this for a long time, typically using lead-acid batteries as the storage medium. I myself have four golf-cart batteries in my garage storing the energy from eight 130 W solar panels, and use these to power the majority of my electricity consumption at home.
We’re not a nation tolerant of power outages. Those big refrigerators can spoil a lot of food when the electricity drops away. A rule of thumb for remote solar installations is that you should design your storage to last for a minimum of three days with no energy input. Even then, sometimes you will “go dark” in the worst storm of the winter. This does not mean literally three days of total deprivation, but could be four consecutive days at 25% average input, so that you only haul in one day’s worth over a four day period, leaving yourself short by three.Thus Dr. Murphy is trying to confront the very gap problem exposed by Dr. Trainer. Not only confront it, but describe the sort of storage system that will insure reliable electricity in an all renewables grid. He assumes that a 7 day supply of battery stored electricity would be sufficient, and that this wouldb
So let’s buy ourselves security and design a battery that can last a week without any new inputs (as before, this is not literally 7 days of zero input, but could be 8 days at 12.5% average input or 10 days at 30% input). This may be able to manage the worst-case “perfect” storm of persistent clouds in the desert Southwest plus weak wind in the Plains.
requires 336 billion kWh of storage. We could also use nuclear power as a baseload to offset a significant portion of the need for storage—perhaps chopping the need in two. This post deals with the narrower topic of what it would take to implement a full-scale renewable-energy battery.Dr. Murphy then acknowledges the importance of low storage costs.
I’ll use lead-acid batteries as a baseline. Why? Because lead-acid batteries are the cheapest way to store electricity today. They’re bulky, sloshy, and very heavy, which makes them unsuitable for electric cars or laptop computers. But they’re very efficient, commonly achieving 85% or better energy efficiency in a charge cycle. The technology is well tested, having been around since 1859. And lead is a common element, being the endpoint of the alpha-decay chain of heavy elements like uranium and thorium. Their economic favorability makes lead-acid batteries hands-down the most common battery type in stand-alone renewable systems worldwide.If the entrire grid were backed up bu a single giant lead storage battery, how much lead are we talking about?
our national battery occupies a volume of 4.4 billion cubic meters, equivalent to a cube 1.6 km (one mile) on a side. The size in itself is not a problem: we’d naturally break up the battery and distribute it around the country. This battery would demand 5 trillion kg (5 billion tons) of lead.Murphy points out the problems associated with other battery storage technologies,
A USGS report from 2011 reports 80 million tons (Mt) of lead in known reserves worldwide, with 7 Mt in the U.S. A note in the report indicates that the recent demonstration of lead associated with zinc, silver, and copper deposits places the estimated (undiscovered) lead resources of the world at 1.5 billion tons. That’s still not enough to build the battery for the U.S. alone. We could chose to be optimistic and assume that more lead will be identified over time. But let’s not ignore completely the fact that at this moment in time time, no one can point to a map of the world and tell you where even 2% of the necessary lead would come from to build a lead-acid battery big enough for the U.S. And even the undiscovered but suspected lead falls short.
What about cost? At today’s price for lead, $2.50/kg, the national battery would cost $13 trillion in lead alone, and perhaps double this to fashion the raw materials into a battery (today’s deep cycle batteries retail for four times the cost of the lead within them). But I guarantee that if we really want to use more lead than we presently estimate to exist in deposits, we’re not dealing with today’s prices. Leaving this caveat aside, the naïve $25 trillion price tag is more than the annual U.S. GDP. Recall that lead-acid is currently the cheapest battery technology. Even if we sacrificed 5% of our GDP to build this battery (would be viewed as a huge sacrifice; nearly a trillion bucks a year), the project would take decades to complete.
But even then, we aren’t done: batteries are good for only so many cycles (roughly 1000, depending on depth of discharge), so the national battery would require a rotating service schedule to recycle each part once every 5 years or so. This servicing would be a massive, expensive, and never-ending undertaking.
I focus here on lead-acid because it’s the devil we know; it’s the cheapest storage at present, and the materials are far more abundant than lithium (13 Mt reserves worldwide, 33 Mt estimated global resources), or nickel (76 Mt global reserves, 130 Mt estimated land resources worldwide). If we ever got serious about building big storage, there will be choices other than lead-acid. But I nonetheless find it immensely instructive (and daunting) to understand what it would mean to scale a mature technology to meet our needs. It worries me that the cheapest solution we have today would break the bank just based on today’s cost of raw materials, and that we can’t even identify enough in the world to get the job done.Murphy is still a renewables true believer, but unlike most, he acknowledges the new clothes problem.
This post does not proclaim that there is no way to build adequate storage to accommodate a fully-renewable energy infrastructure. A distributed grid helps, and an armada of gas-fired peak-load plants would offset the need for full storage. Storage can be augmented by pumped hydro, compressed air, flywheels, other battery technologies, etc.Such realism and candor is exceedingly rare among renewable supporters.
Rather, the lesson is that we must work within serious constraints to meet future demands. We can’t just scale up the current go-to solution for renewable energy storage—we are yet again fresh out of silver bullet solutions. More generally, large scale energy storage is not a solved problem.
My conclusion in 2007 was that renewables supporters were ignoring significant problems that would make an all renewables grid hugely expensive, and that in fact they would have no choice but to fall back on carbon based technology, inorder to make the renewable approach viable. Dr. Murphy acknowledges the problem
an armada of gas-fired peak-load plants would offset the need for full storage.But why chose carbon emitting natural gas in preference to nuclear? Natural gas will not solve the carbon problem, and there are serious environmental problems related to natural gas recovery technology. But natural gas is more acceptable in the ranks f the anti-nuclear power fanatics. The objection might be raised that nuclear power is too expensive, but any attempt to bridge the renewables intermittency gap is likely to make a non-nuclear, renewables based generation system more expensive than an alternative nuclear power based system.
The Emperor, that is a renewable based generating system has no clothes, that is it is far more expensive and far less practical than a nuclear based generating system. Most Renewable supporters, with the exception of Dr. To, Murphy, keep telling us how beautiful the Emperor's clothes are, but surely by now they must see how necked the Emperor truly is.