Stephen Lacey: This is The Interchange, a weekly conversation on the changing business of energy and cleantech from Greentech Media. I'm Stephen Lacey in Boston, joined as always by my co-host Shayle Kann. Hey Shayle.
Shayle Kann: Hey Stephen.
Stephen Lacey: On today's show, solar-plus-storage is a potential sweet spot for customers in a post-net metering world -- but does it come with carbon costs? We're talking with the author of a new study on the emissions impact of pairing batteries with solar PV. That author is Dr. Robert Fares, an AAAS Science and Technology Policy Fellow at the U.S. Department of Energy, and a former postdoctoral fellow at the University of Texas Energy Institute, where he initially conducted the analysis we're talking about today. Robert, welcome.
Dr. Robert Fares: Thank you.
Stephen Lacey: Today's show is kind of a follow-up to an interview we conducted last summer with Jesse Jenkins about the value of grid-scale storage as a carbon reduction tool. This time we're focused on residential energy storage paired with solar. Dr. Fares was the lead author on a study published a couple weeks ago in the journal Nature Energy. It is called “The Impacts of Storing Solar Energy in the Home to Reduce Reliance on the Utility.” It looks at what happens to energy consumption and carbon emissions when you add batteries to a residential PV system in Texas. A short answer: They both go up. We'll talk about why and how much that matters.
First, I have this simple journalistic philosophy. If you have a strong reaction to something, it's probably worth covering. When it came out, this report got a fairly strong response from people following the storage industry, and it got a slew of coverage. Strangely enough, there was actually this non-peer-reviewed study that came to a similar conclusion released shortly after. Shayle, I noticed you and our storage team leader Ravi Manghani were tweeting about it with a bunch of folks, chewing on the assumptions, talking about what it means for Texas and markets beyond. What grabbed you about this report and what do you hope to get out of Robert?
Shayle Kann: I think that it's an important question to ask. If I might broaden the question a little bit -- if you put a bunch of residential storage on the grid, particularly residential storage that's paired with residential solar, what does that do to overall energy consumption, what does that do to peak demand, and, importantly, what does that do to emissions? That's a question that often doesn't get asked in the conversations around energy storage, so you see a lot of hype about residential energy storage that just assumes it's there to reduce carbon emissions and make the grid cleaner. It's a worthwhile question to say, well does it really do that, and under what conditions?
This study I thought...was an interesting start to looking at that question, but I also do think it's important to understand the frame that the study puts around that question, and the extent to which it's applicable broadly, because we want to be careful as we're designing policy and regulation around energy storage at the residential level or just around tariff structures for customers, not to assume that the impacts in one case will be the same everywhere. It's a good conversation to be having right now in the nascent stage of the residential energy storage market.
Stephen Lacey: Robert, why don't you jump in there and explain, is that where you started as well, where a lot of people assume that storage necessarily provides some sort of environmental benefit. Help us contextualize where you started in this study.
Dr. Robert Fares: Yeah, I think Shayle put it really well. That was the context we were coming from. You hear politicians, industry leaders, technologists, and they're often listing this litany of emerging energy technologies and all the benefits they're going to have, and they go solar and wind and renewables and storage. Of course I know fundamentally from a thermodynamic perspective that the big difference between storage and a renewable energy generator is that it's not an energy producer rather it's an energy consumer. It's an energy consuming device that gives you power flexibility. That power flexibility is what makes a lot of people say it's the holy grail. It allows you to take in electricity at one point in time and release it another point in time. That is an incredible feature on today's electric grid, which essentially has no capability to store electricity in that way.
We wanted to critically understand. That capability could be very valuable. How does the extra energy consumption associated with this particular application that's emerging of storing solar energy in the home, what impact does that actually have? Not only on the amount of kilowatt-hours consumed in the household and how that's going to affect the customers bills, but also how does that affect the upstream electricity system and emissions.
Shayle Kann: Right. Let's dig in a little bit into what you studied and what you found. I know I have a bunch of questions about both the assumptions that went into this and then the applicability of it beyond the case that you're studying. Let's start by going over what you looked at and what you found. You basically modeled out real solar customers in Texas. These are actual customers with actual load profiles who actually have solar. You said, what if they added residential energy storage and used that energy storage to effectively self consume as much of the solar as they could to reduce their reliance on the utility. You said, what impact would that have in a couple of different manners for the storage to be deployed? What impact would that have on their overall electricity consumption, their peak consumption and then ultimately in their emissions. Do you want to sort of briefly run through what the high level findings were?
Dr. Robert Fares: Beginning with the motivation behind the study -- we knew part of the reason this application of solar-plus-storage was interesting is that the actual way that the battery would charge and discharge directly depends on when the consumer uses energy and how that aligns with when their solar panels produce power and the relative magnitude of their energy consumption versus their solar generation. We really needed some household level data to understand how residential storage would typically respond to consumer solar generation and consumption.
Fortunately as a researcher at the University of Texas at Austin we had this unique partnership with this entity that emerged after the American Recover and Reinvestment Act and the Smart Grid Demonstration program that followed, which you all are probably familiar with. They now have a very robust collection of electricity data collected on a one-minute time interval from hundreds of volunteer households in Austin. We wanted to use a full year of data. We curated a data set of about 99 households that allowed us to model batteries responding to 99 different customers' electricity generation and use profiles.
Once we could model how storage would respond to their consumption and generation behavior in order to try and reduce reliance on the utility, which we were interested in because that's the number one selling point from residential storage vendors today, where that's the marketing pitch they make, is like, you make your solar during the day, you send a lot of it to the grid, why not store it and use it at night?
We wanted to analyze that application, so that we could then model, how does the actual change and the temporal nature of when that home draws electricity from the grid, and injects electricity to the grid change the overall schedule of generators and the resulting emissions. What we found is with today's current Texas grid mix, [it] led to an increase in emissions. That was little bit of a surprise to us because definitely before we conducted the study there was some internal debate where we were thinking well, in the middle of the day is kind of a moderate load period when solar is typically generating electricity. Maybe by storing energy then we'll actually be increasing generation from combined-cycle natural gas plants like the cleanest fossil fuel power plants out there and offsetting combustion turbines, which kind of have more NOx emissions and higher CO2 emissions than a combine cycle. It seems mostly because of the inefficiencies of the storage, you only get 85 percent of the energy you put in back. Emissions did go up on average.
Shayle Kann: Basically what happens if you store a bunch of the solar that the solar on your roof produces in the process of charging your battery and then discharging it, your round trip efficiency as it's called will be something like 85 percent. Meaning you'll lose 15 percent of the power just in that process. There's an inefficiency there and you don't end up using less electricity in the home, so that 15 percent gets made up by pulling a little bit more from the grid. That's one component.
The other component is what you end up doing, is shifting when you are pulling power from the grid from the time when solar is generating, say middle of the day, to the time when solar is not generating, say in the evening. Between those two things in this case you found that, one, your net electricity consumption goes up, which I think is obvious and always going to be true unless you have 100 percent efficiency, but more interestingly you found that emissions in this case would go up because you pull a little bit more power and because the timing of when you are pulling power doesn't make it cleaner basically.
Dr. Robert Fares: Yeah, and you know this is something that wasn't discussed explicitly in a lot of the media coverage of this because it's a little bit of a subtle point. I didn't write about this in my own blog article covering it but if you look at the household level impact data for the case of SO2 and NOx emissions, there were sometimes where even with the 85 percent efficient storage, which is consuming extra energy where for individual households their SO2 emissions would go down and their NOx emissions would go down. That's an example of where for that particular household, because of the way they use electricity and when they use electricity and when their storage end up charging and discharging, they happen to reduce NOx and SO2 emissions, which is really interesting because of the way they're shifting generation around. The advantage of having this data set of 99 different households is we could say, well for this large collection of diverse households, what's the average impact and that we saw an average increase for both of those two.
Stephen Lacey: Just as a side point. This mirrors the debate or the research that is being conducted about how clean electric vehicles are and it really just depends on what electricity you're consuming form the grid when you determine how clean electric vehicles are relative to combustion engines.
Dr. Robert Fares: Not to cut in, but while you're mentioning vehicles, that's just something about, because you are right where there a lot of similarities but at the same time one of the fundamental advantages of electric vehicles is that in that case you're competing in a way, even if you're drawing fossil fuel energy from the grid, you're competing a large scale emission controlled generator to a small internal combustion engine which is relatively inefficient especially compared to something like a combined cycle natural gas power plant. Whereas with storage you're charging with grid electricity and then you're offsetting grid electricity. You don't have that fundamental advantage of offsetting a smaller less efficient gasoline or diesel generator, or engine in the case of an internal combustion car.
Shayle Kann: Right. I think that's a good segue into sort of the core group of questions that I have about this study which is around applicability. I think what you found given the specific set of circumstances that you were looking at was really interesting, and it's important to note that in some cases, energy storage if deployed in this manner, in this location, at these times can have a net increase in CO2 emissions. I wonder in a bunch of different ways how dependent that finding is on exactly what you're modeling. I guess just to start in on a couple other things; the first one being, you're modeling out energy storage that is used for self consumption, and I think you correctly point out that a lot of the marketing, if you look at the marketing for the Powerwall or a Sonnen product or anything like that, they talk about reducing reliance on the utility in the marketing materials.
That said, I'm not at all convinced that's how systems are being deployed. The primary use case for most energy storage that's been deployed at the residential level in the U.S. is time-of-use shifting, it is demand charge management. If you're in...SRP territory, it's backup or reliability. I don't think outside of maybe Hawaii where there's a self-supply tariff, I don't think you have a lot of customers who are actually charging and discharging energy storage purely for self consumption purposes. I wonder if you were looking, this is obviously outside the scope, but if you were looking at a different use case for energy storage, might that change the equation?
Dr. Robert Fares: I think that's a very fair point. To give you some background on why we decided to focus on self consumption, so part of it was it not only that this seems to be the main marketing pitch made by storage vendors, but also because I think there's this perception amongst consumers, that by storing their own solar energy they can be greener. Whereas I don't think there's the same perception that by responding to time of use prices or something that's going to make me greener, right?
Shayle Kann: Though it may, right? It could be true.
Dr. Robert Fares: Yeah. I think like a general point regarding the issues you're bring up here, and this is related to the intro you gave, part of what we wanted to show with this paper is that the smart grid and electricity systems and the energy system in general is complicated right. I don't like making generalizations about it, like I don't like making generalizations saying that storage is always clean or that storage is always dirty. The point you're making here is that, I think there are certainly cases where storage could lead to a reduction in emissions and I alluded to one where I talked about the phenomenon, maybe you could have shifting of basically increasing generation from combine cycle plants and using that to offset combustion turbines or coal would certainly lead to a reduction in emissions assuming the efficiency of the storage device is high enough.
Shayle Kann: I think, and I don't know how much this played in, Texas is a place where you have a lot of wind generation, generally occurs in the evening, so if you're charging in the middle of the day while there's not a lot of solar on the grid yet, so you're generally getting the charging during the dirtier time, and then discharging when it would have been wind, so it would have been actually pretty clean, you don't get a lot emissions benefit out of that, but in the future if Texas ends up with a lot more solar which is certainly ERCOT expects to happen, you could imagine the equation will start to change even within Texas.
Dr. Robert Fares: That brings up a really important point that we haven't talked about explicitly but I'm sure you all are aware of. In academic circles we talk about the difference between what's called marginal emissions versus average emissions. Marginal emissions are they emissions associated with increasing or decreasing generation at a certain time of day. That's different than saying, what's the emissions factors of all of the generators on the grid average. The reason that's important is because if you say you are going to implement energy efficiency like put in a more efficient light bulb, that's going to have a marginal change on the electricity generation mix. It's going to make it so that only your most expensive generator that's turned on to meet peak demand or just the highest level of demand is turned down. Not all of the generators are turned down equally.
Shayle Kann: There's a difference between looking at what the impact would be of a single customer putting storage in their house to self consume their personal solar versus a lot of people simultaneously doing the same thing and thus it having an impact on capacity on the grid.
Dr. Robert Fares: It's not just that. Talking about the case of renewables, when you're looking at these marginal impacts versus average impacts. That's really important because the way that generators are scheduled by the grid operators, they're scheduled from least marginal cost to highest marginal cost. The least marginal cost generators are generally going to, if the grid can take their electricity then they will always be fully dispatched and fully turned on. Other generators that have a higher marginal cost will be turned on and off as demand fluctuates.
Renewables have, this is one of the fundamental market advantages of renewables, is renewables have a marginal cost of $0. Or in the case of, if you're looking at the wind production tax credit, they have a marginal cost of $-23 dollars per MWh or whatever the exact production tax credit is currently. That means that even in a place like Texas where you have an awful lot of wind energy, when wind is producing at capacity, say it's 40 percent of the generation on the grid, the other 60 percent is actually made up with flexible natural gas and even coal and nuclear generator. That means that if you were to reduce demand or increase demand, the amount of wind being produced wouldn't actually change, what would change was the output from these marginal generators. These typically fossil fueled generators.
Something that could change in the future, if we're looking at the future of the grid mix is a couple things could happen that would change what generators tend to be marginal. One is that, you could have a situation where you have what's called renewable over generation often right, where basically you have so much renewables on the system that you have to curtail them. Either due to a transmission constraint or simply because the total renewable production on the grid is exceeding demand.
Shayle Kann: Right, which is Europe or even occasionally in California already we're starting to see that happen.
Dr. Robert Fares: Yeah, and there can be individual instances of that happening. That's a case where storage, and this is something that I'm always careful to say when I'm talking about the results we found in the paper is that one storage directly enables renewable energy and it's a good thing. That's an example of storage directly enabling renewable energy. That renewable generation could not occur unless you had storage. This actually brings up another issue, unless you had storage or some other way of increasing the flexibility of the grid, and you can think about flexibility in space and time. If you're looking at the example of Texas, there were pretty significant wind curtailments. Something like eight or 10 years, maybe five to 10 years ago in West Texas because there wasn't sufficient transmission capacity to get all the wind energy being produced out of west Texas.
Now with the CREZ lines which is this major project, CREZ stands for competitive renewable energy zones. These transmission lines that were funded and approved by the state government in Texas and then funded through the regulated electric delivery utilities. Since these power lines were energized, very rarely is wind curtailed in Texas. That's part of the reason Texas has seen such large wind energy growth, and been able to facilitate 40 percent wind penetration on a real time basis for hours at a time without a problem.
Stephen Lacey: Shayle I know you have a bunch of questions about applicability here, I want to jump in and just ask, why do you think so many people reacted to this study. To the wonks, the folks who follow this space closely, it's self evident when you have 85 percent efficiency, then you're necessarily consuming more power, and you're necessarily emitting more pollutants. The really interesting part of this study for me was quantifying those pollutants based on where you are on the grid and using this real-time residential data. A lot of us know that this is the case. Help me understand why you think this got such a reaction.
Dr. Robert Fares: I think definitely part of the reaction was because a lot of people have these preconceived notions about the virtues of storing solar energy, especially directly storing renewables in a battery. I think you get this idea where if I'm storing pure renewable energy then there's no way that could be bad. That's because you're not, we would say as engineers, you're not drawing your box big enough. You're not drawing your box where you're looking at emissions impacts large enough to think about what happens outside maybe your individual building where you're storing your solar energy.
By putting your solar in a battery and losing 15 percent of it, and this assumes of course that that battery isn't directly enabling the installation of that renewable system. If you're just adding a battery for reasons of wanting to be resilient or wanting to be independent from the utility or whatever, then what you are doing is you are causing an increase in fossil fuel production or in production from the grid which is dominated by fossil fuels today. That's going to lead to an increase in emissions somewhere. I think that this is an evolving area and policy makers are hopefully becoming more aware that, I like saying storage doesn't automatically reduce emissions. That's the way of saying it, whereas renewables solar and wind, there's really no way that they don't reduce emissions. That's like a very clear cut case. If you're interested in reducing emissions you really need to think about or what storage really brings.
Shayle Kann: I just want to drive home a point though that you've made a couple times Robert in this conversation and that you did make in the study but I don't think got enough attention in the coverage of it necessarily. What you're saying here is that energy storage does not inherently reduce emissions unless it enables more renewable penetration. Even in the study you found solar-plus-storage in these cases is still less emissions on net than not solar at all. Solar alone is best, solar-plus-storage is next best, and no solar is the worst.
I think it's important to be clear that in a case where energy storage enables more solar, really it's going to be increasingly a big share of the energy storage market. In the case of Hawaii, perfect example, Hawaii has now if you're a solar customer, you can choose between the self supply tariff which basically forces you to do exactly what you're modeling in your study here Robert, or you can do grid supply for which your feed-in tariff is really low if the economics don't work. The market is hoping that a lot of self supply customers will come up. It hasn't happened yet, so the economics aren't really quite there yet and a result solar installations are declining in Hawaii, but if and when they do pick up again that would be a case where more solar is being enabled by energy storage, and thus might still reduce emissions.
Dr. Robert Fares: Absolutely. That's something where even before the conversation started in the media, I don't know if everyone made it to the end of the paper, but that was I believe made it into the results and conclusions in the paper. They're pretty strict about the word count but I was adamant about keeping that in there. I do talk about Hawaii in the paper. This unique case of where the grid supply tariff is, not only is it not economically advantageous but I believe that they actually have a cap on the total number of interconnections they can offer under the grid supply tariff. The self supply tariff is a great example of where storage could directly enable solar.
I do want to draw a distinction between Hawaii and the rest of the United States because Hawaii is really an extremely unique case when it comes to renewables integration, because their grid is very small. It has a small amount of flexible generation on it that can offer what electrical engineers sometimes call stiffness. What that means is that the grid frequency is relatively insensitive to changes in supply and demand. In this case, Hawaii their grid isn't stiff and so that means that fluctuations in supply and demand or supply from renewables or demand from consumers can cause some pretty wild fluctuations on the grid wide frequency, and then also on individual distribution feeders in Hawaii, there's an awful lot of houses with solar installed. Part of the reason that is is because Hawaii being isolated from the mainland imports most of its, or generates most of its electricity from imported fuel oil. That's something where it causes their electricity prices to be a lot higher and so the economic case for solar is really good in Hawaii.
The combined things of having a really good economic case for solar and having a grid that is probably the worst in the United States at integrating renewables makes it so that there's this really good case where storage is one of the best options for integrating renewable energy.
Shayle Kann: I agree with you that Hawaii is unique, and certainly...you can get an early view into some of things that might happen in the mainland in Hawaii and some of the things that will happen in the mainland will never happen in Hawaii because like you said it's an island grid. I think the broader point that I wanted to make is that in my view as time goes on storage is more and more going to be necessary in order for the economics of residential solar to pan out in more places. When that's true, I think we go back to this. Storage can reduce emissions even in these cases as long as it's enabling more renewables.
An example of that that I think will be coming on the mainland is in California where solar customers in California are already switching to mandatory time-of-use rates. While those time of use rates in the initial iteration, when they come into effect aren't going to significantly deteriorate the impact or the economics of residential solar. I think the presumption is that over time as you get more and more solar on the grid, the time of use rates are going to sort of move away from solar. The rates are going to get higher when the sun isn't out and they're going to get lower when the sun is out. That's going to create worse economics for solar but an incentive to install energy storage along with that solar. In a case when the only way you can make those economics work is by adding energy storage, it still seems to me that energy storage would have a negative impact on emissions.
Dr. Robert Fares: I think that's absolutely true and that's why, especially in the way that I was writing about this paper for the blog, and also just talking to the media is really stressing the point explicitly before, which is that solar alone if you could do it it's going to be your cleanest option, and then solar-plus-storage is going to be your second cleanest, and then the grid is far behind. At least today's grid which is dominated by fossil fuels is far behind when it comes to the clean energy. If the only way you can get that solar on your roof is by using solar-plus-storage then that's probably the way to go. I think that there's a whole, I guess like two main comments on what you said.
The first one is, I think the economic pull argument that you made is a really good one and that's because if thinking about the wholesale electricity market and what's really happening in the supply and demand dynamics as you get too much renewables generating in a certain time, is that the price of electricity goes to zero or it goes negative. That basically is store, baby, store. If you can charge your battery and get paid for it, that's great. It's nice that the economic incentive aligns where if you have too much solar being generated in the middle of the day in a place like California, there's this clear economic incentive to store energy and then discharge it later on to offset more expensive possible generators.
Shayle Kann: For me what the takeaway here is, especially as I'm thinking about policy makers and regulators, for me it's when designing policy or regulation to support energy storage, and I do think that there's plenty of case to be made, especially at the state level, we should be doing that right now to try to get this market off the ground. When doing that we should have an eye toward exactly how the time shifting of load and what storage is doing to the overall generation mix and thus what impact it has on emissions. I do think that's probably not taken into account as much as it could be in a lot of these conversations, but I don't think it's necessarily a case against creating incentives for energy storage today.
Dr. Robert Fares: Now that you mentioned that point and as we're talking about economic push and pull, an important point to make is like I Just spelled out how renewables growth can directly incentivize storage that helps increase renewable penetration. Especially when the price of natural gas was higher and coal generators were more common, then in that case there was direct incentive to store coal electricity which was cheaper than natural gas and then use that to offset natural gas production. That's something where if you're looking at the extreme case of pure stored coal electricity and then you're throwing 15 percent away to your battery inefficiencies, then you end up having storage being worse than coal.
That doesn't mean that that is going to happen, especially today where we have natural gas being very low price, and natural gas combined-cycle being the go to generation technology. It's important to remember in having these discussions about then role of storage in the grid, is that it can have various impacts. It can enable renewables but it can also, acting in an economic way enable coal.
Stephen Lacey: That right there is I think a clear case for why this is so important when we model the grid, when we consider high amounts of solar and potentially solar-plus-storage and then think about rate design, but also I wonder, and I'm not trying to be flipping here, whether this actually matters for consumers. You're right in that a lot of companies are pitching self consumption as one of the primary benefits for solar-plus-storage, but if you look at surveys of consumers, many of them don't really care about emission. Many of them just want to disconnect themselves from the utility. A lot of the folks who are trying to self consume as much as possible really are driven by an emotional cell. Emissions is really low on the list for a lot of the people, if you actually look at what consumers are telling companies. We talked about this a few months back with Enphase which conducted a pretty robust survey with prospective customers. There's clear implications here for rate design and grid modeling and public policy, but like when you actually pitch consumers, at least the early adopters, many of them just don't care about emissions.
Dr. Robert Fares: I think that's a really good point. Speaking of Tesla and obviously we're talking about examples of home storage like the Powerwall, I think part of what Tesla did with it's electric vehicle is they showed that consumers don't necessarily care about how much money they're spending they're spending on fuel, and how much electrofuel is going to save them, and how much it's going to offset their carbon footprint, they just want a really cool car. If you can sell to them they're going to want to buy it. I think what you said is true. Consumers buy things because they're pretty or something, right? I think like as an engineer studying energy, I'm like the worst person at trying to like put my finger on the pulse of consumers buying energy related products because I think about things from a very analytical perspective.
Shayle Kann: This was true with solar and it's going to be true with energy storage too. There's a small group of people who are going to do it when it's not economic and they'll do it because they want to get away from the utility, or they'll do it because they want back up and reliability, or for the emotional cell that Stephen's talking about. That's not how this market is going to scale. This market is going to scale on economics when there's a pure economic case for energy storage. Those are going to be the customers that want it for, it still might not be emissions reduction purposes, that might be icing on the cake. That's true with solar true. A lot of the solar customers, they want to be green but they're first and foremost saving money, and I think that's what's going to happen with storage too.
Stephen Lacey: Did you ever consider modeling solar-plus-storage against say a diesel generator?
Dr. Robert Fares: I guess in that case, we weren't explicitly looking at backup-type applications or off grid applications. If you're looking at taking homes fully off-grid, that's a tricky question. That's unrelated to the paper, because we of course are looking at these upstream grid impacts and if you're looking at someone trying to completely sever ties with the grid then it's like to what extent do those upstream grid impacts affect them.
Shayle Kann: I think most customers aren't totally defecting from the grid. If they're doing this they're doing it for back up. Seems to me like, I guess it's a little complex but the simple version of that is just either they were going to do back up with a diesel generator or they were going to do solar-plus-storage and solar-plus-storage is definitely going to be cleaner. The question is, were they going to do solar-plus-storage or nothing?
Dr. Robert Fares: That looks at how is the battery actually operating, right? We looked at a battery where because of tariffs or because of desires to cut ties with the utility it's operating to store solar on a daily basis. If you compare that to a battery that only discharges to provide back power, then of course whatever impact it has going to be relatively modest because it's just not doing that much. In the United States we don't lose electricity service that often, and so that means that your battery isn't actually going to be discharging that much. Presuming that it's only going to be discharging when it's providing power to your house in an outage situation.
Shayle Kann: I got to say, of this entire conversation, my favorite part was hearing for the first time the expression "store, baby, store." One can only hope that Rick Perry at some point during his tenure as Secretary of Energy will use that phrase.
Stephen Lacey: Dr. Robert Fares is a former postdoctoral fellow at the University of Texas Energy Institute where he conducted that study, and he's now AAAS Science and Technology Policy Fellow at the U.S. DOE. We really appreciate you coming on the show. He joined us from Washington, D.C.