source: EDN article
Steve Taranovich in its EDN article discuss future vision of selling back energy and gaining a nice margin over what it cost to charge electric vehicles at night using ultracapacitor technologies and large energy storage systems. Shortened version is presented in this article, the full EDN article – see the link above.
Steve Taranovich -June 17, 2016
It was mid-afternoon on a hot, steamy summer day when the power outage struck without warning in a large metropolis. Shortly thereafter, that same evening, somewhere in the depths of the power utilityโs grid computer system, an internet alert was regionally generated to countless Tesla Model S vehicles whose auto-pilots immediately set course via GPS for the affected grid sub-stations. At once, garage doors opened, electronic drives sprung to life, autonomous vehicles reversed onto suburban streets and in a seemingly dream-like trance, but fully aware of their surroundings, entered highway on-ramps in a journey to become veritable power sources through banks of power inverters to the blacked-out region (Figure 1). Each of these vehicles, with their 85 kW-hr capabilities, now provided emergency power to hospitals, businesses, and homes in the region until utility crews could restore power.
Figure 1: Teslas on the road with automatic steering and traffic aware cruise control. (Image courtesy of Tesla Motors)
And there was a bonus to these electric vehicles (EV) owners who availed themselves to this opportunity: They are selling back their energy and gaining a nice margin over what it cost them to charge their vehicles at night—as much as a 6x return-on-investment. Where else can you get that kind of return on your money?
This is Nuvationโs Mike Worryโs fantasy of a Hollywood movie-like, science fiction to become a reality in the next five years or less. Think this is still a fantasy? Well Nissan just announced on May 10 a new trial scheme allowing electric vehicle owners in the U.K. to sell power from their vehicles back to the grid.
Under the vehicle-to-grid (V2G) pilot project, developed in partnership with Italian utility Enel and U.K.โs National Grid, 100 Nissan LEAF vehicle owners in the U.K. will use special bi-directional charging points to sell stored power from their vehicles back to the grid at peak times.
There are currently about 18,000 electric Nissan LEAFs running on U.K. roads. If all were connected, they would have a capacity of 180 MW of energy.
Ask the experts
I recently called upon Mike Worry, CEO of Nuvation Engineering and Martin Mills, Regional Sales Manager of Maxwell Technologies for their expertise in bringing to the EDN audience, a clear picture of large scale energy storage and the Ultracapacitorโs place in this technology.
Daily Energy cycling
I began our discussion with a question regarding the use of batteries and ultracapacitors in smoothing out solar and wind-powered generatorsโ output fluctuations over time. Worry commented that this was a good example of a hybrid application working well to combine the high power of ultracapacitors with the high energy of batteries. In applications such as this, the need for a great deal of energy that a battery can supply in a function such hours-long electricity demand reduction is combined with the exceptional response time and cycle life of an ultracapacitor measured in millions of cycles vs. the batteryโs thousands of cycle capability.
If there are wind gusts occurring 10s of times per day, then you will consume a batteryโs life in under a year. Whereas, if you hybridize with ultracapacitors, you now have a quality system that is able to handle the frequent high power surges with ultracaps and the slower but longer duration outages with a battery.
This is both good for operations and good for cost. Worry said that what Nuvation, as an engineering company, finds in these energy storage systems is that to each part of a problem you build a different solution, so ultracaps and batteries work really well in such situations.
Mills added that from Maxwellโs perspective, ultracaps in these types of hybrid systems really are a great complement to batteries. They help extend life expectancy as well as reduce the potential size of the batteries required. The operational temperature range also give ultracaps an advantage, even though most of these systems will have some sort of thermal management capability. Ultracaps are exceptional at extreme cold temperatures as compared to batteries, so thermal management design, if implemented, need not be too elaborate or costly.
I commented that I had written an article in which ultracaps supplemented batteries in a light rail transportation system in extremely hot climates like Arizona where I live. A Maxwell expert gave some great insights into this type of design challenge.
Mills said that there are two different market segments where ultracaps are used in transportation and grid applications: When an ultracap is deployed on the light rail vehicle itself, that is a transportation market area; when it is used to store wayside energy captured through recuperative or regenerative braking, we call that a grid application.
Rate-payers concerned with the cost of using the utility
I posed the question asking how stacked utility services could be implemented using smart-storage electronics. I wondered how services such as demand charge reduction could save rate-payers money by using energy during low demand times and providing energy back to the grid during peak times. And how ultracaps would fit into this scenario.
Worry exclaimed that the fascinating part of the emerging energy storage industry is that weโre taking a resource of energy that used to only be instantaneous and transactional and we are inventing the concept of being able to store it and then apply that stored energy using energy management software.
By analogy, imagine what money was like before we had the ability to store money in banks or before we had the ability to store information in written form. We are now doing that with energy. There is a whole new economic model that has emerged from that.
The ability to stack these services is really in a software layer and the ones that make for quick returns and justify return on investment (ROI), like demand charge reduction and load shifting or behind-the-meter applications, are all about how the utility prices electricity. If they charge a premium for your highest amount of power draw, then of course that will motivate the industry to figure out what they can put in place in the way of energy storage to reduce that demand charge, and equally if there are different charges for different times of the day, then that will motivate the industry to use energy for time-of-use shifting. Worry thinks we will see emerging residential energy storage systems that basically make decisions, stacking those different types of algorithms to figure out the best way to apply energy storage in order to reduce your electric bill.
Then on the utility side of the meter you see stacked services that are making different decisions because on the utility level there are things such as renewables integration and frequency regulation that are operating at a larger level and making different decisions; this would be another set of algorithm-stacked services that run on the grid level.
Easing the financial burden
I live in Arizona where there are many people with residential solar installations that are taking advantage of the abundant sunshine here in the desert. So many homeowners think they can get off the grid easily here. Without energy storage, that is going to be difficult because there are still cloudy days during the monsoon season as well as other times of the year. ROI is in the order of an average of 10 years or so for these types of installations to recoup their initial investment. So stacked usage would help lessen the financial burden of the homeowner utility bill.
Mike Worry thinks we will see some energy storage rollout in high quantity, small energy storage systems on the residential side in order to have people optimize their electric bills. The largest driver for energy storage will be on the utility scale, and he thinks it will be the very high Renewable Portfolio Standards (RPS) targets of many utilities.
Solar curtailment
Worry lives in California where currently 42% of utility generation uses renewables. That has already resulted, for example, on a summer afternoon, in solar curtailment because there is more solar energy available to be fed back onto the grid than the utility can absorb. There are lessons to be learned from this. Solar curtailment just recently occurred in Germany as well.
We are going to start seeing situations where there is a negative rate schedule. This means that the grid, being an old legacy system, has lots of capability to handle extra energy if there is not enough generation, i.e. an excess of load; however, too much renewable energy being fed back to the grid cannot be handled by the utilities. The solution to excess energy from renewables is to roll out vastly increased amounts of energy storage, says Worry.
California went to the federal government and stated that there is a problem when we have too much solar and we canโt use it all; we donโt have enough load in that summer afternoon to use all that excess solar energy. So maybe we should slow down Solar Income Credits. The federal government replied with a definitive No, and that they are going to maintain the credits; it is an important national initiative, so California needed to figure it out.
A government-mandated energy storage effort?
Well, California did figure it out and responded with the comment that they would roll out 1.36 GW-hrs of energy storage in their state. That is is a multi-billion dollar contract to accomplish this, but it will be distributed among many suppliers. This effort is, of course, a utility-driven, well-known market and government mandates are pushing the largest part of this effort.
Nuvation actually just announced the conformance of their utility-scale (up to 1250 VDC, scalable to a 50 battery-stack configuration for ISO container-housed electrochemical energy storage systems) battery management system to the MESA open standard for energy storage (Figure 2).
Figure 2: GBC-installed-in-1MW-Container: the black box on the right side is the Nuvation Grid Battery Controller โ it controls multiple battery stacks to enable megawatt-scale battery management. (Image courtesy of Nuvation)
Nuvationโs attainment of Draft 3 conformance streamlines the integration of their battery management system with Parker Hannifinโs MESA-conformant inverters and third-party site controllers on the Alevo GridBank project (Figure 3).
Figure 3: Michael Worry (facing us third person from the left) at Parker Hannifin Grid Tie Division in North Carolina, showing various people from the energy storage industry the battery management systems in the new 1MW/1Wh Alevo GridBank ESS (Image courtesy of Nuvation)
I commented that when there is a Tesla or two in everyoneโs garage; that will help the energy storage effort, as well as greatly benefit Elon Musk.
Generate an income from your EV
Worry said that we can envision that in the future,ย EVs will no longer be a family cost but a family income source. At night, in a region where there is wind and nuclear generation running and not getting much demand from customers, you would charge up your EV and the next morning drive it from your residential area into a congested town, like an area where you work or have a business. Then discharge it for the energy needs of the local businesses at a higher rate to the EV owner than it cost you to charge it the night before. You actually generate an income from your EV. (EDN also had discussed this issue back in a 2007 blog.)
Worry has a Model S with 85 kW-hr potential, and he only needs to drive 20 miles to work, so he would happily sign an agreement to sell his energy, at a nice margin, out of his car and onto the grid. He feels that there are many others who would also see the benefit of this and do it as well.
Energy shifting of loads
I was curious how energy shifting of loads would benefit by the combined usage of batteries and ultracapacitors.
Mike Worry told us that in time-of-use billing, ultracapacitors would not necessarily a good fit. This is more of an energy play rather than a high power play because it is usually over a few hours. So for example, at Worryโs home in Campbell, CA on a summer afternoon, he can sell electricity at $0.25 per kW-hr and then buy it back at night at $0.04 per kW-hr—an amazing 6x spread. Go to any stock trader and tell them that we are going to give you a guaranteed market to day-trade an asset and get a 6x multiplier every single day. Too good to be true? Itโs a reality.
Worry did a load shifting experiment at home by charging his EV battery from a stored energy lead-acid battery during his utilityโs peak demand charge periods; the ROI was delivered in only six months. He believes this to be an artificial spread since it probably will not continue.
Voltage sag and power quality remediation–Fast response applications for ultracaps?
Ultracaps are an excellent match for fast response, high power applications like Voltage Sag and Power Quality Remediation. Voltage Sag is a utility-grade issue where they need to implement larger energy storage systems to handle Voltage Sag and related to that—Frequency Regulation. Worry said that they are putting in large systems and you can be charging and discharging from that 20, 30 or 40 times per day. Nuvation has looked at applications like that using batteries and you would chew up your battery life in about four monthsโnot very economically viable.
Those types of applications really work best with ultracapacitors paired with a battery resource behind it. And then the level behind that would be generators or Peaker Plants as a sequence of energy operations.
There are about 300 Peaker Plants in the U.S. which only turn on for a few days per year. They need to be fully set up and staffed, while only being used for a small number of days in the year when there is a demand surge. If you could save the cost of all these Peaker Plants and replace them with ultracapacitors in conjunction with battery energy storage, you can realize a great deal of cost-savings.
The other part of this is that to be prepared for variable load fluctuations that cannot be forecasted, there is an estimated 30% Spinning Reserve. There is approximately 30% more energy generated than is needed in the instant. If we can capture that excess energy in energy storage systems and use it to manage variations of load, this would drastically reduce the need for spinning fossil fuel generators; in this way you can recover that 30% of electricity, which is huge.
Martin Mills told us that with regard to alternatives typically what most people do is add more batteries to compensate for the power demand in their systems. The reason they do that is they do that is they are usually not familiar with the technology and usage of ultracaps or do not understand how they can be properly hybridized into a system. However, in stacked use cases that require both power and energy, it is generally more economical from a capital and operational expenditure perspective to hybridize ultracapacitors with high energy batteries such as aqueous batteries or flow batteries. For example, a stacked use case could be to provide solar smoothing, peak shaving, and time shifting within a single energy storage system. ย An excellent example of this is the system recently deployed at Duke Energy.
Maxwell has also been very successful in the transportation market which adopt ultracaps in such initiatives regen for diesel electric hybrid buses and Start-Stop systems for automotive in Europe and North America.
Planet Analog has a blog by Maxwellโs Shaw Lynds on finding the sweet spot for hybridization in which two new ultracap grid energy storage projects have been rolled out at Duke Energy and China Guodian Corp (Figure 4).
Figure 4: Lifecycle cost of selected grid-tied energy storage technologies versus project-rated discharge time using the Zakeri model. (Image courtesy of Maxwell Technologies)
Distributive energy sources to help stabilize grid energy distribution
Alevo Analytics looks at how the grid is used and then forecasts the best place to insert what they call a โGrid Bank.โ They run an Area Controller that can optimize the use of energy storage, stacking the services, and figure when the batteries should be charged and discharged in order to stabilize distribution.
Utlities want to know where the EVs are
Mike Worry told us that there has been much attention on what the impact is going to be on the grid with increasing adoption of EVs. The level of issues have perhaps been a bit overplayed because the draw of an EV is not much different than your air conditioner (A/C) at home and you donโt hear about people being concerned about the rollout A/Cs as being a threat to de-stabilize the grid. Typically, an A/C is used heaviest in the daytime, and there are some areas of the country where they are run at night as well. Here in California where he lives, Worry says that he turns off his A/C at night and charges his EV, so itโs not really a difference in transmission requirements.
I thought that A/Cs are a mature technology and their usage is well understood by the utility. EVs are still in the early stages of ramping. Worry replied that some people get excited that EVs are drawing a huge amount of power but they actually can be adjustable remotely with a switch controlled over the Internet. He does not have the ability to reach into his A/C at home to adjust its power draw but he sure can reach into his Tesla and regulate his charge rate.
There is a great deal of thought and capability being put into how that is being done, so we need to continue to be good engineers and pay attention to that system roll-out, but he does not think that EVs will collapse the grid.
Frequency regulation issues on the grid
I wondered how batteries and ultracaps could help play a role in Frequency Regulation.
Worry commented that batteries and ultracaps are actually a required solution in order to roll-out variable generation renewables and have a risk of that load variation increasing with the adoption of EVs. We are going to need more capability to provide stability to frequency and load regulation. Fast responding energy storage assets are essential. Hybrid systems containing ultracaps combined with batteries, as we saw in California adoption of renewables, will stall out unless there is an energy storage system to go with it. As someone in the energy storage ecosystem, Worry likes it when California continues to roll-out more Solar because that will require more energy storage and the software it will be providing for Frequency Regulation at the same time it is providing for renewables integration. It is beyond the fact that it can help—it is actually a requirement.
Nuvationโs efforts in battery management systems on a grid scale
Nuvation has been building battery management systems (BMS) for the last eight years. They have a product in the field at the utility level. What they are seeing on a Grid scale is continuously increasing voltages and sizes. The present Nuvation battery management system can go up to 1,250 VDC and scale it up to 50 stacks in parallel (Figure 5).
Figure 5: A high level block diagram of a multistack energy storage system being run by Nuvation BMS. (Image courtesy of Nuvation)
Worry is glad that they put that type of capability into the product because they are seeing people build ever-increasingly large systems. They have a product they call a Grid Battery Controller (announced last year) which will take all of those parallel stacks and have them look like a single battery. There is a layer of energy management systems doing the Area Controller functions, combining together multiple energy storage systems and their energy now becomes software. You can remotely choose what type of grid you desire. You can say that I want the grid that produces the lowest cost per kW-hr of Energy Storage or I want the grid that runs the greenest or I want the grid that reduces my transmission as much as possible. You can actually choose on a software level, the type of utility you want (Figure 6).
Figure 6: Running 4 stacks – All the readings are actually an accurate reflection of what you would see in a running large-scale ESS. (Image courtesy of Nuvation)
Itโs kind of cool that they can have that kind of innovation going on in a grid that is really a pretty old system. I would liken it to that of the old telephone Plain Old Telephone Service (POTS) phone lines and the advent of Digital Subscriber Lines (DSL) in the 80s.
DC power transmission would make Edison happy
There are many thoughts and efforts about High Voltage (HV) DC Power Transmission ultimately to homes and businesses and even HVDC in Telecom and Data Centers.
Mike Worry thought that this was possible. There may be more of that as we do more and more solar and renewable energy storage as DC functions.
I think that if you look at what we are powering for the most part, itโs all electronics and they mostly run on DC power to all the semiconductors.
Worry added that all our computers are DC-based and we have all these โwall wartsโ everywhere, converting AC back to DC. Hawaii has a mandate to be 100% renewables by 2040. Their renewables are all going to be DC. So you are going to take it from DC, convert it to AC, transmit it and then convert most of it back to DC for consumption.
The existing transmission infrastructure is mostly AC and AC-coupling is an electrical system that people understand well and are comfortable with it. Worry does not see DC transmission coming any time soon for general roll-out. What you may see is a system where you get DC grids somewhere like in the building of a new community in the middle of the Arizona desert and they are going to build a DC town because they donโt have the existing legacy AC Grid out there.
The other thing that is really fascinating is to look at third world countries where there is no good roll-out of telecom. Rather than going the route of North America by rolling out a series of infrastructure composed of wired transmission lines and putting wireless on top of that, you will get parts of the world that choose to skip the wired route and just go directly to a wireless infrastructure for telecom because it is cheaper.
Mike Worry thinks that will happen with Energy Storage as well. They will say, well look—weโve got this area of Africa or India that already has a horrible grid, so letโs just have this whole town go off-grid and letโs put in a large solar array paired with energy storage and weโll run this whole town on DC power.
Utility Solar customers
Aside from large scale energy storage, we have mentioned the homeowners/EV owners and small businesses in this article as well. Just to round out the discussion and bring to light the challenges with this group, I want to mention an excellent article in the local Arizona Republic newspaper by Ryan Randazzo which outlined the latest realities with โSolar + Batteriesโ.
Since I now live in Arizona, with 300+ days filled with sunshine, I have become acutely aware of utility โDemand Ratesโ which Mike Worry has also addressed briefly above. Here in Arizona, some energy advocates who promote rooftop solar, are anti-utility imposed โdemand ratesโ oriented. It seems to me that homes and small businesses would benefit from battery to reduce the financial effect of โdemand chargeโ as Worry indicated as well.
Here in Arizona, the grid is highly strained by homes with solar panels because they are most effective at noon here in the desert, but towards sunset can only generate about 25% of their full capacity, with zero output at night. The local demand for electricity here peaks at about the time the sun sets, at which time businesses and homes are in full swing with their air conditioners (Itโs an unusual phenomena in the desert as opposed to other areas like the East coast where I came from, where the maximum temperature of the day is around sunset). So the problem is that solar panels without battery storage capability do not effectively help the utility in this late-afternoon demand time.
The local Arizona utilities are now urging customers to employ battery technology and have said that this effort is not anymore just a solar-only story, which is a dinosaur. This solution will also work well to improve solar energy solutions anywhere else even though Arizona is an extreme case.
Many large solar energy installers are opposed to utility demand rates. Battery storage systems in the home coupled with solar and demand-controlling devices like those which prevent large appliances from operating at the same time, smart inverters and advanced air conditioners with SEER and EER along with a programmable thermostat look to be the solution to greatly mitigate demand rates by utilities to solve this debate.
