Fast Ramping

Customer Solar: Every . minutes, a new solar installation goes live Traditional Generation: Energy storage: Coal-red power will supply % growth just / of power generation in by – compared with more than half in

Fast ramping: Electric Vehicles: Utilities can expect a Without it, -% increase in electricity consumption among households the grid’s a that own a PEV sitting duck Grid Scale Customer Solar: Process Load: gigawatts gigawatts of load Wind: % of new installed PV exibility in top generation capacity base by U.S. industries

f you’d happen to attend a utility conference this year, chances are some vendor has a picture of the now-famous “duck chart” somewhere in its booth or presentation materials. The duck chart is a graph plotted by the California Independent System Operator (CAISO), and it I represents what will happen as distributed generation begins to take up more and more of the net load curve. Net load in this chart is the diff erence between two forecasts: load and electricity production from variable generation resources. As a CAISO explanation of the duck curve notes, “In certain times of the year, these curves produce a ‘belly’ appearance in the mid-afternoon that quickly ramps up to produce an ‘arch’ similar to the neck of a duck — hence the industry moniker of “’The Duck Chart.’”

To determine the curve of the duck, CAISO analyzed net load forecasts for • Decreased frequency response, which will result when more solar pro- every day of the year from 2012 to 2020. According to CAISO, the analysis duction means that fewer resources with automatic frequency-sensing shows several conditions will emerge. Those conditions include: and output adjustments will be online • Short, steep ramps needed to meet rapid increases and decreases California’s duck curve is particularly compelling because it refl ects changes in demand coming in the near future as a result of the state’s regulatory mandate to • Over-generation risk brought on when mid-day solar production supplies achieve a portfolio standard of 33 percent renewable generation by 2020. more energy than real-time demand That’s fewer than fi ve years away. But, even without those ambitious goals, many states will face similar conditions. Following is a look at reasons why and what some are doing about it. Numbers add up First, let’s look at why fast ramping is becoming a necessity. In a nut- shell, it’s the growth of variable generation resources like solar and wind energy installations. U.S. growth fi gures for solar generation are eye-popping. By the end of 2015, installed solar capacity had expanded to more than 30 times 2006 levels, according to the Solar Energy Industries Association. On the commercial end of things, a wide range of businesses invested or reinvested in solar projects. Among them are Walmart – the company with the most solar electric capacity, according to SEIA. The big box store that Sam Walton built has more than 140 MW of photovoltaic (PV) capacity coming from 348 completed installations. Plenty of other companies choose solar, too. Costco, Ikea, FedEx and For- The NREL report adds, “How soon these detrimental effects will occur ever 21 are some of the bigger retailers. Manufacturers include General will depend on the amount of creep damage present and the specific Motors, Ford, Toyota, Volkswagen, Intel, Owens Corning and Johnson & types and frequency of the cycling. Several renewable integration stud- Johnson. Overall, the U.S. solar market is set to grow 119 percent in 2016, ies, including those performed by NREL and the Western Electricity Co- GTM Research predicted in the U.S. Solar Market Insight Report 2015 Year ordinating Council, have recognized increased power plant cycling due to in Review. renewables. Additionally, most reports also list the need for more flexible GTM also forecasts that 16 gigawatts (GW) of solar will be installed in generation in the generation mix to meet the challenge of ramping and the U.S. in 2016, which is more than twice the 7.3 GW installed during providing reserve requirements.” record-breaking 2015. Nearly three-quarters – 74 percent – of the 2016 Meeting ramping needs head on installations will be utility-scale deployments, but that still leaves the elec- Multiple approaches exist for addressing the fast-ramp requirements tric system with potentially less inertia and, therefore, more vulnerability to of a DER-laden grid. One is market-based, and it’s being pioneered frequency excursions. by California, which has been working to implement a “flexible ramp- Like solar power, wind energy – another variable generation resource – ing product,” or new short-term energy market that could shift energy also is on the rise. According to the Bloomberg New Energy and Finance supply and demand very quickly. The flexible ramping product differs 2016 Factbook, an estimated 8.5 GW of wind capacity was installed in 2015 from other ancillary services, such as regulation which supports fre- versus solar’s 7.3 GW. Wind build in 2015 topped numbers from 2014 by quency balance and spinning reserves that step in if a generation 65 percent. source is lost, because its aim is to incent generators to bid their true The down side of ups and downs ramping capability, not just capacity. As of now, tariff development is underway. Load fluctuations accompany solar and wind generation, so fast-ramping resources are a must. What is ramping? It’s the ability of a generation fa- On a smaller scale, generation companies also have a way of addressing cility or energy resource to stop or start on command. The ramp rate is the fast ramping needs. Some, like NRG Energy in California, are building flex amount of time required for output to increase or decrease. plants designed to fill in when renewables don’t produce enough electricity. NRG’s plants employ combined-cycle technology that uses both a gas and That sounds simple enough, but here’s the problem. Most base-load gen- steam turbine to produce electricity from the same fuel by routing the waste eration resources can’t be quickly cycled up or down. That’s why CAISO’s heat from the gas turbine to the steam unit. Together, the two turbines duck curve has a big belly. The lower half of the curve represents the can product up to 50 percent more energy from the fuel than a traditional over-generation that must occur because California’s long-start genera- simple-cycle power plant. tion resources keep churning out energy in the middle of the day, when solar power is available to provide the electricity used by much of the According to an article that appeared on National Geographic’s website, load on the system. NRG has two generation units in El Segundo, Calif., and they “can each ramp up to 150 megawatts within 10 minutes and reach a maximum output There’s another problem, too. According to the U.S. Energy Information Ad- of 275 megawatts apiece in less than an hour. In contrast, old gas-fired ministration, 39 percent of generation in the U.S. comes from coal-based steam boilers still in use at the site take up to 12 hours to warm up, and plants, and another 27 percent comes from natural gas facilities. So, 56 NRG typically fires them up in the evening to be ready for the next day’s percent of the nation’s energy is coming from fossil-fuel-based generation power needs.” resources and, as the National Renewable Energy Lab points out in its Power Plants Cycling Costs report, cycling fossil-fuel-based power plants is costly. Built-in flexibility The NREL report explains why: “Every time a power plant is turned off and Flex power plants are a great addition to the modern grid, but we shouldn’t on, the boiler, steam lines, turbine and auxiliary components go through forget that the grid already has plenty of flexibility built in via the flexibility of unavoidably large thermal and pressure stresses, which cause damage. This loads themselves. And both residential and commercial loads can participate. damage is made worse for high-temperature components by the phenome- A good example on the C&I side can be seen in water and wastewater pump- non we call creep-fatigue interaction.” ing operations. They consume approximately 7 percent of the electricity used In materials science, creep refers to deformation of materials due to me- in the U.S., and water pumping has inherent storage properties. That’s be- chanical stresses. Fatigue is material weakening in response to repeated cause you can fill a reservoir to the top during hours when solar or wind pro- stress. It’s the reason a piece of metal can break in two after you repeatedly duction is high or overall demand is low, and thereby shift that pumping load bend and unbend it. to off-peak hours without impacting operations at the water or wastewater production plant. According to the NREL report, “While cycling-related increases in failure rates may not be noted immediately, critical components will eventually Enbala uses water pumping facilities in delivering grid services, and the start to fail.” program is a win-win for both the grid operator and the water utility. Energy bills, as a percentage of operating costs for drinking water sys- Potential results of shorter component life in power plants include higher tems, can typically reach as high as 40 percent, according to the U.S. En- plant equivalent forced outage (EFOR) rates and higher maintenance costs vironmental Protection Agency. At one facility participating in regulation to replace components at or near the end of their service lives. Reduced service for its regional ISO through the Symphony by EnbalaTM platform, overall plant life is another potential impact. water utility managers were able to shave thousands off an electric bill that previously reflected 1,200,000 kilowatt hours per month in usage a gigawatt of energy each night by controlling the electric resistance water and a peak demand of 1,900 kilowatts. heaters of 65,000 end-use members. On the residential side, the nation’s 50 million residential electric wa- The cost-effective solution ter heaters could deliver significant energy storage according to new Leveraging load flexibility like the examples above,Symphony by Enbala is al- research commissioned by the National Rural Electric Cooperative Associ- ready in use controlling and coordinating electricity usage at a wide range of ation (NRECA), the Natural Resources Defense Council (NRDC), the Peak facilities, all of which have their own capacity and ramping capabilities that Load Management Alliance (PLMA) and Great River Energy (GRE). are part of the platform’s control parameters. Together these connected Conducted by the global economic consulting firm The Brattle Group, the assets can deliver very fast-ramping capacity at a grid operator’s command. report on this research has a fitting title: The Hidden Battery Opportunities in How? The platform coordinates the customer-defined constraints and oper- Electric Water Heating. ating parameters of each asset continuously. This allows a grid operator to As the report authors explain, “Electric water heaters are essentially pre- dictate how much capacity they need with whatever precision they choose. installed thermal batteries that are sitting idle in more than 50 million Because the platform aggregates a large number of loads, there is always homes across the U.S. By heating the water in the tank to store thermal some grouping of assets that will deliver capacity with whatever speed and energy, water heaters can be controlled in real-time to shift electricity precision the grid operator needs. consumption from higher-priced hours when less efficient generating units Why are such approaches so valuable? Because they’re an easier way to are operating on the margin to lower-priced hours when less costly gener- firm renewables, increase the grid’s ability to accommodate renewables, ation is operating on the margin and, in some cases, there may be excess supply fast-ramping resources and help power providers address these supply of energy from low- or zero-emitting resources such as wind power.” issues without adding to the burden of capital expense they already face. The report also explains why water heaters offer so much opportunity. Today, decades of underinvestment in the grid are finally catching up According to the researcher, water heaters account for 9 percent of house- to us. EIA figures show the average age of a coal-based power plant in hold electricity consumption across the U.S. That’s the third largest source the U.S. is 38. Many older plants don’t have the scrubbers installed to of residential electricity consumption. Space cooling accounts for 13 percent, comply with the Mercury and Air Toxic Standards, which go into effect and lighting accounts for 11 percent. Approximately 40 percent of U.S. this year . Consequently, EIA anticipates that as much as 90 percent of households have electric water heaters. the coal-fired capacity that had been slated for retirement in 2020 will What can be achieved when you control them? Great River Energy, a gen- actually occur this year. eration and transmission cooperative in Minnesota, has been able to store According to the Rocky Mountain Institute’s report titled The Economics of Demand Flexibility, “Electric utilities in the United States plan to invest an estimated $1+ trillion in traditional grid infrastructure – generation, transmission, and distribution – over the next 15 years, or about $5-80 billion per year, correcting years of underinvestment. However, official forecasts project slowing electricity sales growth in the same period (less than 1 percent per year), coming on the heels of nearly a decade of flat or declining electricity sales nationwide.” RMI estimates that residential demand flexibility could help power providers avoid as much as $13 billion per year in grid costs. When coordinated with a distributed energy resource management platform, demand flexibility can do more than forestall investment. It can ramp rapidly enough to flatten out the duck curve. In other words, we can achieve the fast ramping our grid needs if we leverage the flexibility of DERs connected to it. Who knows? Maybe we’ll wind up with a dead duck curve instead of a sitting-duck grid.