Willett Kempton at a wind installation in Denmark. (Photo courtesy University of Delaware)

Q&A: Can renewables alone (with storage) power the grid?

Conventional wisdom among many utilities and analysts says that renewable energy is expensive and unreliable because the wind doesn’t always blow and the sun doesn’t always shine when electricity demand is highest, and because grid-scale storage is expensive and not ready for prime time.

As a result, many in the electric power industry believe that to power entire regional electrical grids, we must continue to rely on fossil fuels for much of our baseload power.

Last month, Willett Kempton, a renewable energy expert at the University of Delaware, reported a detailed analysis turning conventional wisdom on its head.

Writing in the Journal of Power Sources, a peer-reviewed journal, Kempton and his colleagues reported for the first time that by 2030 the grid could be powered almost entirely using a mix of wind (both on- and off-shore), solar and grid-scale energy storage, and that this grid would be both affordable and reliable.

This conclusion came from extensive computer modeling that analyzed four years of hour-to hour data on weather and electricity consumption by the PJM Interconnection, the regional transmission organization for a 13-state swath of the mid-Atlantic and Midwest.

Midwest Energy News caught up with Kempton to ask him what it will take to move to a grid powered almost entirely by renewables.

Midwest Energy News: Earlier studies showed that in theory there’s far more than enough wind and solar power to meet the world’s electricity demands. But many believe that wind and solar are too intermittent to be reliable as a source of baseload power, and our limited ability to store that energy until it’s needed will keep us continually reliant on fossil fuels for baseload power. You found that wasn’t the case. If renewables and storage were adopted as you describe in this study, what would the electrical grid look like in 2030?

Kempton: You have a diversity of sources because you’re more likely to have power generated when you need it if you have onshore wind and offshore wind and some solar. A lot of the time you’re generating more power than you need. And when you are doing that you store it, but before long your storage fills up, so most of the time you’ve got excess power.

Sometimes, when you don’t have enough power being generated by renewables, you discharge your storage and run on that, plus whatever renewables you’ve got. And a few times per year, you actually have to look to some other source. In our analysis we used fossil, using legacy plants that are already in existence, and just running them much less frequently.

So, that’s what the system looks like: Lots of apparently excess renewables, a very small amount of storage, and some older fossil plants that are being kept around for these situations.

Earlier computer modeling efforts by renewable energy analysts had tried to match wind, solar and hydro generation to electricity use to see if renewables could provide reliable electricity. Your model instead tested 28 billion combinations of renewables and storage and sought out those that were least expensive. Why did you seek to minimize cost rather than maximize reliability?

We did set a reliability limit, so we said you have to enough power to run the system 30 percent of the time, enough for 90 percent of the time, enough for 99.9 percent of the time. For each of these, we ran for minimum cost. The reason we did that is that we really were trying to match two fluctuating things. People talk about renewable energy fluctuating, but load also fluctuates. So, unless you really understand whether the fluctuations are in sync or out of sync, it’s very hard to know how much renewable generation you need to make load.

[It’s also hard to know] which types, because wind on land tends to peak in production more in the evening, though that varies with location. Wind offshore tends to be more constant, but tends to peak when you have storm patterns moving through.  And solar, of course, peaks at noon. So, what’s the least-cost combination of those three and storage? We couldn’t know that in advance. We really had to try all combinations.

Your model found that the most affordable renewable-dominated grid was one with more than twice the generation capacity than would seem to be needed. Does that mean the excess energy would be wasted?

If we only had today’s uses of electricity, and didn’t change anything about how we use electricity, than yes it would be wasted. But what we saw when we did this model is that the excess primarily occurs in the cold months. That’s not necessarily something we expected. I mean, we knew there was more wind in the winter. We’re getting lots of excess electricity, especially September, October through May.

And lo and behold, that’s when we’re using a lot of fuels for heating. So . . . we asked the question, suppose we displaced natural gas for heating with this excess electricity? And when you calculate the energy value of that excess electricity, it’s pretty close to the same as the amount of energy burned for natural gas.

In this study, you sought to minimize all the costs of burning fossil fuels, and you included costs that ratepayers don’t pay for today, such as the damaging health and environmental effects of harvesting and burning coal and natural gas. Given the political power of utilities and fossil fuel companies, that seems like a big assumption. Why do you think it’s justified?

We’re not saying this is going to happen. We’re not saying this is a prediction of the future. We’re just saying let’s just look at what the costs are. Because people say, Renewable energy is expensive, or electric cars are expensive. Let’s figure out what the cost actually is.

Say I opened up a new business. I want to buy some things, manufacture a product and sell it, but I’m going to take some of the costs and I’m going to put it on somebody else’s ledger. So I’m not going to actually pay for the steel I’m using. I’m going to charge Dan for that. Well, I’m going to be able to offer my product at a lower price.

That’s what the fossil fuel industry is doing right now. Especially with health costs, which is an immediate, current cost that actually just goes right over on the ledger of health.

We’re not saying that’s going to change, just like I wouldn’t have said in 1960 people are going to stop smoking cigarettes. We’re just saying, what is the actual cost of this? So don’t tell me that cigarettes are cheap, or that electricity from coal is cheap–it is, by market price–but that’s not the total cost. We were trying to calculate total cost.

At the same time, we did not subsidize the renewables. We didn’t say, hey, there’s a production tax credit now and that’s a cool policy and you can get the taxpayers to pay for part of your wind turbine. We took away all the subsidies. We just put the actual costs of renewables and the actual cost of fossil, and put them together.

To achieve the sort of all-renewable grid that you write about, do we need new or improved generation or storage technologies?

We did not assume any technological changes. We took the numbers that were projected for 2030–what the same technologies would cost then, with the kind of minor refinements you get when you manufacture a product over 20 years. And, we took the cost projected for storage. I don’t think that’s realistic. I think that we will have step changes in both storage and in renewable generation, and they’ll probably occur before 2020, much less by 2030. But we didn’t assume that. We just assumed current technologies with refinements, but not new discoveries.

What policy changes would have to happen to make the grid you describe a reality?

My first answer would be let’s just charge what stuff costs. So, a new technology gets subsidized for 10 or 15 years, but if you’ve got external costs, they ought to be included in the price. So, we can estimate, when you build a coal plant, you don’t know if Jones is going to die of cancer vs. Smith, but you know from epidemiological studies that it will cause approximately this many deaths and lost work days and so forth. So that should be part of the cost of generation. If you do that, then the market will just do this stuff by itself.

In the policy area, the other way to do it is what we’re doing now, which is to subsidize renewables until they get to enough volume that they’re actually able to compete without subsidies. But that’s a policy answer.

The other way to answer the question is, What would we do to get there? I think I would say we would need some analysis by the energy planners to ask not just what’s cheaper today–onshore wind or offshore wind or solar–but to ask what kind of systems do we want when we build this out to 30 percent or 50 percent of our energy production from renewables. Our study shows you don’t want to keep just picking the cheapest source. You want to pick sources that go together so that one that might be a bit more expensive, but produces power when your cheaper ones are not producing much power–you want to have that as part of the mix.

That’s not the way we do planning now. You need another 100 MW? What’s the cheapest way to do it? That [describes] all state energy planning and all [utility] planning. Nobody’s doing this kind of analysis like we have done here.

10 thoughts on “Q&A: Can renewables alone (with storage) power the grid?

  1. Thanks for the great analysis of renewable energy potential! My suggestion for all developers of wind farms, old and new, would be to install solar panels on the south side of every wind turbine tower. The wind farm already has a grid connection so this would add very little cost, but would add quite a bit to the energy production time each day. The solar combined with the wind would smooth out the power outputs of the generation asset.

  2. I like seeing that the paper is available to read online.
    It’s interesting that wind could offset the fossil fuels for heating if we stored them.
    If the US were to export Natural Gas, we would have the hassles of LNG terminals but the market does exist.
    Right now the cost of NG is so low and we have plenty of it for the next 100 years. So do we just stop harvesting or sell off to Japan and other countries the NG?

  3. For about 4 years now I’ve thought about a project like this one – now here it is, great work! I have not looked at the report in detail but plan to study it over the next few days. And then as member of our local electric co-op will try to get our directors and our main wholesale power provider to comment on it.

  4. Can renewables alone power the grid? NO.
    Is there utility scale storage available? Only if there is nearby hydro with pumped storage.
    See BENTEK study of Public Service of Colorado.

  5. The writers of the paper were unfortunately on hopium, assuming a perfect transmission system within PJM’s territory. But we can dream, can’t we?

  6. Randy, we can dream. But in the case of grid connected industrial solar and wind, they are mostly pipe dreams.

  7. I wonder if Rolf Westgard is the same individual who is promoting the Keystone XL pipeline. If so, don’t be fooled by the smoke and mirrors. If it is the same individual, Westgard suggests burning gasoline derived from the Alberta tar sands will have a similar lifecycle greenhouse-gas footprint compared to conventional crude sources. This is nothing more than fantastic fiction folks. The peer-reviewed science has shown, in a recent report commissioned by the European Union, that lifecycle emissions (well-to-wheels) will be ~23% higher using synthetic crude from tar sands in Alberta, relative to using conventional feedstock in refineries. Given this, let’s imagine if the entire fleet of the U.S. is converted to more fuel-efficient internal combustion engine (ICE) vehicles, say a 20% improvement in fuel efficiency is achieved fleet-wide across the nation. Burning gasoline originating from Alberta bitumen will mean emissions will not even decrease, but will instead increase overall. Kind of spinning the tires as with such an approach we get nowhere and problems such as global warming will continue getting worse. Makes much more sense to think the problem through a little better, which is what Dr. Kempton and his team have done. It’s not rocket science to understand that electric vehicles are 4-5 times more efficient than ICE vehicles. Need some storage, such as batteries, to achieve a high-penetration of clean renewable energies? No problem. This is not expensive in reality. Just put four wheels on the batteries and replace burning fossil fuels in our vehicles altogether. We can literally drive the change by integrating wind and solar in our EVs. Batteries add to upfront capital costs, sure, but maintenance costs of an EV are 1/5 of the gas-guzzling, global warming automobiles we drive to day. Driving 100 miles on ~$3 of wind and solar sounds less like a pipedream and more like a plan for a sustainable future to me. In fact, it’s Keystone XL that’s the pipedream, etc… one that will bring our worst nightmares to reality. If we just keep burning everything, someday most of Delaware will be underwater, along with 7% of the world’s land as we’ll eventually disappear all the world’s ice pack, most of the people in the world live near coasts, so hopefully people are learning to see through all of this smog, of lies and deception. We will grab hold of this potential of large-scale wind and solar power integration for the benefit of us all.

  8. http://www.oilempire.us/peak-electricity.html

    Renewables for a Steady State Economy

    Using solar energy for twenty years (and wind power for ten) taught me that renewable energy could only run a smaller, steady state economy. Our exponential growth economy requires ever increasing consumption of concentrated resources (fossil fuels are more energy dense than renewables). A solar energy society would require moving beyond growth-and-debt based money.
    After fossil fuel we will only have solar power, but that won’t replace what we use now. We need to abandon the myth of endless growth on a round, and therefore, finite planet to have a planet on which to live. Will we use the remaining fossil fuels to make lots of solar panels and relocalize food production instead of waging Peak Oil Wars?

    Living on our current solar budget could not be a seamless substitute for digging up a hundred million years of sunlight.

  9. Mark Robinowitz, while it is sensible to come to grips with limits of humankind’s growth of civilization on our finite planet earth, we should acknowledge the facts: wind, water and sun can power the world entirely with energy for the long-run. True, you may need neodymium for turbines and it is classified as a rare earth. But, to power half the world with wind requires 1/7 of current reserves of this element. There is no shortage of concrete and steel, and ~98% of steel is recycled, this can be done with all critical materials for turbines, solar panels, batteries, fuel cells, etc… So while recycling may be needed to power the world forever with clean energy, materials and energy resources are certainly not limits. I’m not sure you understand how little of the available wind and sunlight is needed to repower civilization for humankind. It’s trivial, and only about half the Sahara desert, in terms of land area would be needed to power everyone, everywhere in a clean energy economy. Mostly this will be open space between wind turbines. I appreciate your concerns, and am not trying to dissuade you from encouraging folks to reduce the use of resources.. I agree with this principle. That said, let’s awaken to the facts folks, no more science fiction. It can be done with wind, water and sun:


    In Mr. Robinowitz’s link, he asserts that wind turbines can’t be built fast enough. Yet in World War II the world produced ~800,000 airplanes in only a few years, so don’t tell me we can’t produce four million modern wind turbines over a few decades.