The grid of 2030: all renewable, 90 percent of the time
arstechnica.com
arstechnica.com
>>When there is not enough renewable energy direct from source, and the stored energy reserves are insufficient to bridge the shortfall, top up the remaining few percent of the demand with fossil fuels.<<
We don't have any way to "top up" the remaining few percent of demand with fossil fuels. You can't simply flip a switch on a coal fired or nuclear power plant and have it instantly produce power. These massive processes need tremendous lead time to start producing electricity. So, in theory wind could provide a lot of power, but since we have no idea when the wind will die and when we will need to "top off" the shortfall, we keep coal fired plants churning.
This is one reason why, as the largest utility in Germany states[1], it takes roughly 24MW of wind power to take just 1MW of fossil fuel power offline:
"As a result, the relative contribution of wind power to the guaranteed capacity of our supply system up to the year 2020 will fall continuously to around 4% (FIGURE 7). In concrete terms, this means that in 2020, with a forecast wind power capacity of over 48,000MW (Source: dena grid study), 2,000MW of traditional power production can be replaced by these wind farms."
Storage, and the near-immediate ability to use what is stored, would help this tremendously, but we don't have that capability, and we don't seem to be well on our way to getting it, even by 2030.
[1]http://www.wind-watch.org/docviewer.php?doc=eonwindreport200...
First, you need to build wind/solar plants, which tend to be more expensive than conventional power plants to start with.
Then, you either need to invest in R&D for power storage systems and build out those facilities or, more likely, you need to build out conventional power capacity to accommodate for demand when solar or wind is not producing. In the end you've spent quite a lot more money and likely you haven't actually reduced the number of conventional power plants you've built or even reduced CO2 emissions substantially (due to the reliance on less clean conventional power plants during solar/wind down times as well as the CO2 cost of constructing those plants).
Another novel and new invention is www.aquionenergy.com who has an environmental battery made of carbon and salt :)
Essentially its best to start capping our consumption levels and increasing efficiency. Have a look at the current wasted energy in our system: https://flowcharts.llnl.gov
On many days, the wind power goes up at night and down during the day, very much in complement, though in larger scale than, solar generation. More solar will more nearly equalize the two -- on good days.
California is nowhere near having an overcapacity of renewable sources to worry about; just look at the first graph where the lowest demand (2 AM to 4 AM) is 22 GW on 12/14/2012. The highest the solar gets is not quite 1 GW. The wind is more variable, anecdotally as high as 3+ GW and as low as a flatline near zero for the whole state all day and night.
What I'm wondering is whether we can get there from here. We can't simply dictate the end result we want and have it appear.
What we could use now is some kind of economic simulation, taking into account the cost of shutting down fossil plants early, the capital cost of building all that wind and solar (and the upfront capital is the bulk of the cost, since operating costs are low), the actual utilities and regulatory structures currently in place, etc.
Then we can see whether what sort of policy changes we might need, to get an end result like this, and what it will cost to put all this in place.
This way we act as a buffer allowing better ressource usage.
Even better, appliances like dishwashers and washing machines could be connected to the network to read the price level and run automatically when the price is lower than a fixed amount.
Even better, for industries which are using energy automatically, they should bid for the excess energy and when there is a big surplus, the energy will be really cheap and will be used instead of going to waste.
Large users on the other hand, can devote a team to ensure optimal usage around complex / time-dependent tariffs.
Great point about smart appliances tho: that will have to wait for full integration of the smart grid and there will have to be a clear incentive to buy expensive appliances... since the overall savings could be fairly minimal (e.g. one less peaker plant) it's harder to provide benefits for millions of users. Again "demand response" e.g. turn-down-on-demand for large power users (perhaps even large building airconditioner loads) makes sense to target first.
There is no doubt a lot of interesting tech potential in this area... but utilities move so so slow.
Right now it's only cost-effective with large loads, and only economical if it's largely automated.
(By point of comparison, most people already can't be bothered to switch off a 100W room light when they leave. That means we just don't GAF about saving pennies per hour if it means we have to push a button every so often).
However, seeing how heating and cooling are the only residential loads that are really worth worrying about, and both can typically be advanced or deferred by an hour or so without any problems, you could probably solve 90% of the problem by smartening up a handful of appliances in each home.
Industrial users can often do similar things. A cold storage facility, for example, could do most of it's cooling when power is cheap and then coast through the expensive periods. And they use enough electricity to pay someone (or buy an automated system) to handle it for them.
Once you solve heating and cooling, everything other than cooking (basically lighting and entertainment) is getting more and more efficient every year. And most people don't cook enough to make that a significant load.
The problem with building out solar or especially wind power generation is that it's unreliable, it doesn't produce power when you want it. This means that you need to supplement power generation with low latency backup systems. Unfortunately, those systems tend to be gasoline-powered generators. Building those and operating them is expensive and also not so beneficial from a total CO2 emissions perspective. More so when you compare the whole system to simply replacing the windmill and the generator with a natural gas generator, which is more reliable, cheaper, and produces less total net CO2.
http://en.wikipedia.org/wiki/Renewable_energy_in_Germany
It's possible
http://www.bloomberg.com/news/2011-05-30/germany-becomes-net...
http://www.bloomberg.com/news/2012-08-19/merkel-s-green-shif...
http://www.spiegel.de/international/germany/new-coal-fired-p...
It's easy to generate a lot of renewable energy when you've got the old power plants ready to cover any shortfalls in generation capacity. Just because you can acheive 25% under those conditions by prioritizing renewables does not imply that you can push renewables up to 90%+.
The wind can stop blowing for quite some time, even on a country wide scale. You either have to store the energy, import it from other countries or have backup power stations to cover the shortfall.
The (free) book Without Hot Air is a fantastic read for more information. It's written by a no nonsense physicist that dives pretty deep into possible plans for a future energy grid, including all the messy details.
And the details are messy. Any renewable energy plan that doesn't sound like a momentus undertaking is cheating by 1) Only talking about electricity, not total energy 2) Discounting embodied energy of imports 3) Keeping a country sized fossil fuel infrastructure around to fill in the gaps 4) Importing energy
Sometimes all four.
Besides, as we bring more cars off of fossil fuels, we will need the electricity on the grid anyway.
As to why AC uses so much power, a lot of it relates to dehumidifying air which takes a lot more power than you might expect.
PS: In most areas you can substitute solar hot water heaters for the vast majority of home heating needs so long term it's not really a problem.
The problem is still severe. In a country the size of the US it is still possible for there to be days of very little wind across the whole country. And, of course, once the Sun goes down on the West coast there won't be any power coming from solar for many hours. Which means that in a worst case scenario you need to rely on nuclear, coal, or hydrocarbon based power generation. And it means that you can't avoid having to build out conventional power generation capacity to match peak loads (which can occur when solar and wind power production is effectively zero).
It'd be nice if the actual study were online somewhere without a paywall.
And I haven't read it yet, but I guess storage costs rise very sharply for every additional 9 you want in your reliability. 90% could mean a month without power each year. To get from there to 99% or a week one very two years by improving storage capacity, you would likely need capacity for at least three weeks of full load.
https://sites.google.com/site/verticalwindfarm/
it still doesnt matter because everyone gets screwed.
http://www.csmonitor.com/layout/set/print/content/view/print...
apparently there is no value in ideas.
also the only scholarship i ever got was from Chevron. the irony will save us!
I'm guessing that at current wind/solar capacity, any fluctuations can be absorbed by just slowing down the flow out of the reservoir, rather than ever having it reverse.
You also need a downhill source of water, which means any dam that's the last one downstream can't really use this approach.
You could maybe even get away with an entirely closed-loop system, but if you look at the scale of the problem, you need either a huge pair of reservoirs (lake-sized) or a huge elevation difference (mountain-sized), or preferably both. It doesn't appear economical to build e.g. a tank on a tower.
It's just not very cost effective right now.
I can certainly believe the capital requirements are much higher for pumped storage than for natural gas peakers.
Round trip efficiency isn't great, but also not terrible. It beats the fuel-cell/electrolysis cycle, but loses to batteries. It can be profitable though because energy rates can reach near zero (and even occasionally slightly negative) at night.
99% of installed energy storage is pumped hydro.
We do this to some extent, but the reality is we do need to ensure rivers continue to flow for a number of reasons (I guess).
http://www.inference.phy.cam.ac.uk/withouthotair/c26/page_18...
basically the author says that what you describe is the best option right now but there are only so many places you can put those facilities because they require very specific geography.
That being said building lakes and dams is really bad for the river eco system and really expensive to buy land out from under people to flood it.